1
|
Chatterjee AK. Discovery of novel anti-infective agents. ADVANCES IN PHARMACOLOGY (SAN DIEGO, CALIF.) 2024; 100:39-117. [PMID: 39034055 DOI: 10.1016/bs.apha.2024.05.001] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/23/2024]
Abstract
Academic and other non-profit institutions have a long-term vision to improve human health where commercial interests can be limited for profit organizations. Medicinal chemistry to these diseases with no commercial benefit needs is well suited in the academic environment and this chapter outlines some work conducted at Calibr-Skaggs around antibiotic drug development that has led to initiation of multiple clinical trials over the last decade.
Collapse
Affiliation(s)
- Arnab K Chatterjee
- Calibr-Skaggs Institute of Innovation Medicines, Scripps Research, La Jolla, CA, United States.
| |
Collapse
|
2
|
Gupta AK, Eliasen AM, Andahazy W, Zhou F, Henson K, Chi V, Woods AK, Joseph SB, Kuhen KL, Wisler J, Ramachandruni H, Duffy J, Burrows JN, Vadas E, Slade A, Schultz PG, McNamara CW, Chatterjee AK. A Prodrug Strategy to Reposition Atovaquone as a Long-Acting Injectable for Malaria Chemoprotection. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2024:2024.02.08.579395. [PMID: 38979188 PMCID: PMC11230151 DOI: 10.1101/2024.02.08.579395] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 07/10/2024]
Abstract
Recent malaria drug discovery approaches have been extensively focused on the development of oral, smallmolecule inhibitors for disease treatment whereas parenteral routes of administration have been avoided due to limitations in deploying a shelf-stable injectable even though it could be dosed less frequently. However, an updated target candidate profile from Medicines for Malaria Venture (MMV) and stakeholders have advocated for long-acting injectable chemopreventive agents as an important interventive tool to improve malaria prevention. Here, we present strategies for the development of a long-acting, intramuscular, injectable atovaquone prophylactic therapy. We have generated three prodrug approaches that are contrasted by their differential physiochemical properties and pharmacokinetic profiles: mCBK068, a docosahexaenoic acid ester of atovaquone formulated in sesame oil, mCKX352, a heptanoic acid ester of atovaquone formulated as a solution in sesame oil, and mCBE161, an acetic acid ester of atovaquone formulated as an aqueous suspension. As a result, from a single 20 mg/kg intramuscular injection, mCKX352 and mCBE161 maintain blood plasma exposure of atovaquone above the minimal efficacious concentration for >70 days and >30 days, respectively, in cynomolgus monkeys. The differences in plasma exposure are reflective of the prodrug strategy, which imparts altered chemical properties that ultimately influence aqueous solubility and depot release kinetics. On the strength of the pharmacokinetic and safety profiles, mCBE161 is being advanced as a first-in-class clinical candidate for first-in-human trials.
Collapse
|
3
|
van der Boor SC, Alkema M, van Gemert GJ, Teelen K, van de Vegte-Bolmer M, Walk J, van Crevel R, de Mast Q, Ockenhouse CF, Sauerwein RW, McCall MBB. Whole sporozoite immunization with Plasmodium falciparum strain NF135 in a randomized trial. BMC Med 2023; 21:137. [PMID: 37024868 PMCID: PMC10079489 DOI: 10.1186/s12916-023-02788-9] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/06/2022] [Accepted: 02/15/2023] [Indexed: 04/08/2023] Open
Abstract
BACKGROUND Whole sporozoite immunization under chemoprophylaxis (CPS regime) induces long-lasting sterile homologous protection in the controlled human malaria infection model using Plasmodium falciparum strain NF54. The relative proficiency of liver-stage parasite development may be an important factor determining immunization efficacy. Previous studies show that Plasmodium falciparum strain NF135 produces relatively high numbers of large liver-stage schizonts in vitro. Here, we evaluate this strain for use in CPS immunization regimes. METHODS In a partially randomized, open-label study conducted at the Radboudumc, Nijmegen, the Netherlands, healthy, malaria-naïve adults were immunized by three rounds of fifteen or five NF135-infected mosquito bites under mefloquine prophylaxis (cohort A) or fifteen NF135-infected mosquito bites and presumptive treatment with artemether/lumefantrine (cohort B). Cohort A participants were exposed to a homologous challenge 19 weeks after immunization. The primary objective of the study was to evaluate the safety and tolerability of CPS immunizations with NF135. RESULTS Relatively high liver-to-blood inocula were observed during immunization with NF135 in both cohorts. Eighteen of 30 (60%) high-dose participants and 3/10 (30%) low-dose participants experienced grade 3 adverse events 7 to 21 days following their first immunization. All cohort A participants and two participants in cohort B developed breakthrough blood-stage malaria infections during immunizations requiring rescue treatment. The resulting compromised immunizations induced modest sterile protection against homologous challenge in cohort A (5/17; 29%). CONCLUSIONS These CPS regimes using NF135 were relatively poorly tolerated and frequently required rescue treatment, thereby compromising immunization efficiency and protective efficacy. Consequently, the full potential of NF135 sporozoites for induction of immune protection remains inconclusive. Nonetheless, the high liver-stage burden achieved by this strain highlights it as an interesting potential candidate for novel whole sporozoite immunization approaches. TRIAL REGISTRATION The trial was registered at ClinicalTrials.gov under identifier NCT03813108.
Collapse
Affiliation(s)
- Saskia C van der Boor
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands
| | - Manon Alkema
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands
| | - Geert-Jan van Gemert
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands
| | - Karina Teelen
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands
| | - Marga van de Vegte-Bolmer
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands
| | - Jona Walk
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands
- Present affiliation: TropIQ Health Sciences, Transistorweg 5-C02, 6534 AT, Nijmegen, The Netherlands
| | - Reinout van Crevel
- Department of Internal Medicine, Radboud Center for Infectious Diseases, Radboud University Medical Centre, Geert Grooteplein Zuid 10, 6525 GA, Nijmegen, The Netherlands
| | - Quirijn de Mast
- Department of Internal Medicine, Radboud Center for Infectious Diseases, Radboud University Medical Centre, Geert Grooteplein Zuid 10, 6525 GA, Nijmegen, The Netherlands
| | | | - Robert W Sauerwein
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands.
- Present affiliation: TropIQ Health Sciences, Transistorweg 5-C02, 6534 AT, Nijmegen, The Netherlands.
| | - Matthew B B McCall
- Department of Medical Microbiology, Radboud Center for Infectious Diseases, Radboud University Medical Center, Geert Grooteplein Zuid 28, 6525 GA, Nijmegen, The Netherlands.
| |
Collapse
|
4
|
Schnyder JL, de Jong HK, Bache EB, van Hest RM, Schlagenhauf P, Borrmann S, Hanscheid T, Grobusch MP. On the potential for discontinuing atovaquone-proguanil (AP) ad-hoc post-exposure and other abbreviated AP-regimens: Pharmacology, pharmacokinetics and perspectives. Travel Med Infect Dis 2022; 52:102520. [PMID: 36526126 DOI: 10.1016/j.tmaid.2022.102520] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2022] [Revised: 11/30/2022] [Accepted: 12/09/2022] [Indexed: 12/15/2022]
Abstract
According to current guidelines, atovaquone-proguanil (AP) malaria chemoprophylaxis should be taken once daily starting one day before travel and continued for seven days post-exposure. However, drug-sparing regimens, including discontinuing AP after leaving malaria-endemic areas are cost-saving and probably more attractive to travelers, and may thus enhance adherence. AP has causal prophylactic effects, killing malaria parasites during the hepatic stage. If early hepatic stages were already targeted by AP, AP could possibly be discontinued upon return. Pharmacokinetic data and studies on drug-sparing AP regimens suggest this to be the case. Nevertheless, the evidence is weak and considered insufficient to modify current recommendations. Field trials require large numbers of travelers and inherently suffer from the lack of a control group. Safely-designed controlled human malaria infection trials could significantly reduce study participant numbers and safely establish an effective AP abbreviated regimen which we propose as the optimal trial design to test this concept.
Collapse
Affiliation(s)
- Jenny L Schnyder
- Center for Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam UMC, Location University of Amsterdam, Amsterdam, Netherlands
| | - Hanna K de Jong
- Center for Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam UMC, Location University of Amsterdam, Amsterdam, Netherlands
| | - Emmanuel B Bache
- Center for Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam UMC, Location University of Amsterdam, Amsterdam, Netherlands
| | - Reinier M van Hest
- Department of Hospital Pharmacy & Clinical Pharmacology, Amsterdam UMC, Location University of Amsterdam, Amsterdam, Netherlands
| | - Patricia Schlagenhauf
- University of Zurich Centre for Travel Medicine, WHO Collaborating Centre for Travelers' Health, Department of Public and Global Health, Military Medicine Biology Competence Centre, Institute for Epidemiology, Biostatistics and Prevention, Zurich, Switzerland
| | - Steffen Borrmann
- Institute of Tropical Medicine, German Centre for Infection Research (DZIF), University of Tübingen, Tübingen, Germany; Centre de Recherches Médicales en Lambaréné (CERMEL), Lambaréné, Gabon
| | - Thomas Hanscheid
- Instituto de Microbiologia, Faculdade de Medicina, Universidade de Lisboa, Lisbon, Portugal
| | - Martin P Grobusch
- Center for Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam UMC, Location University of Amsterdam, Amsterdam, Netherlands; Institute of Tropical Medicine, German Centre for Infection Research (DZIF), University of Tübingen, Tübingen, Germany; Centre de Recherches Médicales en Lambaréné (CERMEL), Lambaréné, Gabon; Masanga Medical Research Unit (MMRU), Masanga, Sierra Leone; Institute of Infectious Diseases and Molecular Medicine (IDM), University of Cape Town, Cape Town, South Africa.
| |
Collapse
|
5
|
Salkeld J, Themistocleous Y, Barrett JR, Mitton CH, Rawlinson TA, Payne RO, Hou MM, Khozoee B, Edwards NJ, Nielsen CM, Sandoval DM, Bach FA, Nahrendorf W, Ramon RL, Baker M, Ramos-Lopez F, Folegatti PM, Quinkert D, Ellis KJ, Poulton ID, Lawrie AM, Cho JS, Nugent FL, Spence PJ, Silk SE, Draper SJ, Minassian AM. Repeat controlled human malaria infection of healthy UK adults with blood-stage Plasmodium falciparum: Safety and parasite growth dynamics. Front Immunol 2022; 13:984323. [PMID: 36072606 PMCID: PMC9444061 DOI: 10.3389/fimmu.2022.984323] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/01/2022] [Accepted: 08/01/2022] [Indexed: 11/13/2022] Open
Abstract
In endemic settings it is known that natural malaria immunity is gradually acquired following repeated exposures. Here we sought to assess whether similar acquisition of blood-stage malaria immunity would occur following repeated parasite exposure by controlled human malaria infection (CHMI). We report the findings of repeat homologous blood-stage Plasmodium falciparum (3D7 clone) CHMI studies VAC063C (ClinicalTrials.gov NCT03906474) and VAC063 (ClinicalTrials.gov NCT02927145). In total, 24 healthy, unvaccinated, malaria-naïve UK adult participants underwent primary CHMI followed by drug treatment. Ten of these then underwent secondary CHMI in the same manner, and then six of these underwent a final tertiary CHMI. As with primary CHMI, malaria symptoms were common following secondary and tertiary infection, however, most resolved within a few days of treatment and there were no long term sequelae or serious adverse events related to CHMI. Despite detectable induction and boosting of anti-merozoite serum IgG antibody responses following each round of CHMI, there was no clear evidence of anti-parasite immunity (manifest as reduced parasite growth in vivo) conferred by repeated challenge with the homologous parasite in the majority of volunteers. However, three volunteers showed some variation in parasite growth dynamics in vivo following repeat CHMI that were either modest or short-lived. We also observed no major differences in clinical symptoms or laboratory markers of infection across the primary, secondary and tertiary challenges. However, there was a trend to more severe pyrexia after primary CHMI and the absence of a detectable transaminitis post-treatment following secondary and tertiary infection. We hypothesize that this could represent the initial induction of clinical immunity. Repeat homologous blood-stage CHMI is thus safe and provides a model with the potential to further the understanding of naturally acquired immunity to blood-stage infection in a highly controlled setting.
Collapse
Affiliation(s)
- Jo Salkeld
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | - Jordan R. Barrett
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Celia H. Mitton
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | - Ruth O. Payne
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Mimi M. Hou
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Baktash Khozoee
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Nick J. Edwards
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Carolyn M. Nielsen
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Diana Muñoz Sandoval
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Florian A. Bach
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | - Wiebke Nahrendorf
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
| | | | - Megan Baker
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | | | - Doris Quinkert
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | | | - Ian D. Poulton
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Alison M. Lawrie
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Jee-Sun Cho
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Fay L. Nugent
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Philip J. Spence
- Institute of Immunology and Infection Research, University of Edinburgh, Edinburgh, United Kingdom
- Centre for Immunity, Infection and Evolution, University of Edinburgh, Edinburgh, United Kingdom
| | - Sarah E. Silk
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Simon J. Draper
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
| | - Angela M. Minassian
- Department of Biochemistry, University of Oxford, Oxford, United Kingdom
- The Jenner Institute, University of Oxford, Oxford, United Kingdom
- *Correspondence: Angela M. Minassian,
| |
Collapse
|
6
|
Han B, Alquist CR. Amber-colored Plasma in Therapeutic Plasma Exchange. Clin Infect Dis 2021; 72:519-520. [PMID: 33527129 DOI: 10.1093/cid/ciaa896] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Affiliation(s)
- Bing Han
- Department of Pathology, Louisiana State University Health Sciences Center, New Orleans, Louisiana, USA
| | | |
Collapse
|
7
|
Nevagi RJ, Good MF, Stanisic DI. Plasmodium infection and drug cure for malaria vaccine development. Expert Rev Vaccines 2021; 20:163-183. [PMID: 33428505 DOI: 10.1080/14760584.2021.1874923] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/21/2022]
Abstract
Introduction: Despite decades of research into the development of a vaccine to combat the malaria parasite, a highly efficacious malaria vaccine is not yet available. Different whole parasite-based vaccine approaches, including deliberate Plasmodium infection and drug cure (IDC), have been evaluated in pre-clinical and early phase clinical trials. The advantage of whole parasite vaccines is that they induce immune responses against multiple parasite antigens, thus lowering the impact of antigenic diversity. Deliberate Plasmodium IDC, as a vaccine approach, involves administering infectious, live parasites in combination with an anti-malarial drug, which controls the infection and enables induction of protective immune responses.
Collapse
Affiliation(s)
- Reshma J Nevagi
- Institute for Glycomics, Griffith University, Gold Coast Campus, Southport, QLD, Australia
| | - Michael F Good
- Institute for Glycomics, Griffith University, Gold Coast Campus, Southport, QLD, Australia
| | - Danielle I Stanisic
- Institute for Glycomics, Griffith University, Gold Coast Campus, Southport, QLD, Australia
| |
Collapse
|
8
|
Hanscheid T, Schlagenhauf P, Grobusch MP. Atovaquone/proguanil for malaria chemoprophylaxis - Could a difference in susceptibility during hepatic development explain the need to continue drug intake for 7 days post-exposure? Travel Med Infect Dis 2019; 33:101527. [PMID: 31759143 DOI: 10.1016/j.tmaid.2019.101527] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/25/2019] [Revised: 11/19/2019] [Accepted: 11/20/2019] [Indexed: 10/25/2022]
Affiliation(s)
- Thomas Hanscheid
- Instituto de Microbiologia, Instituto de Medicina Molecular, Faculdade de Medicina, Universidade de Lisboa, Lisboa, Portugal.
| | - Patricia Schlagenhauf
- University of Zürich Travel Clinic, WHO Collaborating Centre for Traveller's Health, Institute for Epidemiology, Biostatistics and Prevention, University of Zürich, Zürich, Switzerland
| | - Martin P Grobusch
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Amsterdam University Medical Centers, Location AMC, University of Amsterdam, Amsterdam, the Netherlands
| |
Collapse
|
9
|
Skinner-Adams TS, Fisher GM, Riches AG, Hutt OE, Jarvis KE, Wilson T, von Itzstein M, Chopra P, Antonova-Koch Y, Meister S, Winzeler EA, Clarke M, Fidock DA, Burrows JN, Ryan JH, Andrews KT. Cyclization-blocked proguanil as a strategy to improve the antimalarial activity of atovaquone. Commun Biol 2019; 2:166. [PMID: 31069275 PMCID: PMC6499835 DOI: 10.1038/s42003-019-0397-3] [Citation(s) in RCA: 17] [Impact Index Per Article: 3.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/29/2018] [Accepted: 03/15/2019] [Indexed: 12/28/2022] Open
Abstract
Atovaquone-proguanil (Malarone®) is used for malaria prophylaxis and treatment. While the cytochrome bc1-inhibitor atovaquone has potent activity, proguanil's action is attributed to its cyclization-metabolite, cycloguanil. Evidence suggests that proguanil has limited intrinsic activity, associated with mitochondrial-function. Here we demonstrate that proguanil, and cyclization-blocked analogue tBuPG, have potent, but slow-acting, in vitro anti-plasmodial activity. Activity is folate-metabolism and isoprenoid biosynthesis-independent. In yeast dihydroorotate dehydrogenase-expressing parasites, proguanil and tBuPG slow-action remains, while bc1-inhibitor activity switches from comparatively fast to slow-acting. Like proguanil, tBuPG has activity against P. berghei liver-stage parasites. Both analogues act synergistically with bc1-inhibitors against blood-stages in vitro, however cycloguanil antagonizes activity. Together, these data suggest that proguanil is a potent slow-acting anti-plasmodial agent, that bc1 is essential to parasite survival independent of dihydroorotate dehydrogenase-activity, that Malarone® is a triple-drug combination that includes antagonistic partners and that a cyclization-blocked proguanil may be a superior combination partner for bc1-inhibitors in vivo.
Collapse
Affiliation(s)
- Tina S. Skinner-Adams
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111 Australia
| | - Gillian M. Fisher
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111 Australia
| | - Andrew G. Riches
- Commonwealth Scientific and Industrial Research Organization, Biomedical Manufacturing, Clayton, VIC 3168 Australia
| | - Oliver E. Hutt
- Commonwealth Scientific and Industrial Research Organization, Biomedical Manufacturing, Clayton, VIC 3168 Australia
| | - Karen E. Jarvis
- Commonwealth Scientific and Industrial Research Organization, Biomedical Manufacturing, Clayton, VIC 3168 Australia
| | - Tony Wilson
- Commonwealth Scientific and Industrial Research Organization, Biomedical Manufacturing, Clayton, VIC 3168 Australia
| | - Mark von Itzstein
- Institute for Glycomics, Griffith University Gold Coast Campus, Gold Coast, QLD 4222 Australia
| | - Pradeep Chopra
- Institute for Glycomics, Griffith University Gold Coast Campus, Gold Coast, QLD 4222 Australia
| | - Yevgeniya Antonova-Koch
- School of Medicine, University of California, San Diego, La Jolla, CA 92093 USA
- Present Address: California Institute for Biomedical Research (Calibr), La Jolla, CA 92037 USA
| | - Stephan Meister
- School of Medicine, University of California, San Diego, La Jolla, CA 92093 USA
- Present Address: Beckman Coulter Life Sciences in Indianapolis, Indianapolis, IN 46268 USA
| | | | - Mary Clarke
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111 Australia
| | - David A. Fidock
- Department of Microbiology and Immunology, and Division of Infectious Diseases, Department of Medicine, Columbia University Medical Center, New York, NY 10032 USA
| | - Jeremy N. Burrows
- Medicines for Malaria Venture (MMV), Route de Pré Bois 20, Geneva, 1215 Switzerland
| | - John H. Ryan
- Commonwealth Scientific and Industrial Research Organization, Biomedical Manufacturing, Clayton, VIC 3168 Australia
| | - Katherine T. Andrews
- Griffith Institute for Drug Discovery, Griffith University, Nathan, QLD 4111 Australia
| |
Collapse
|
10
|
DSM265 at 400 Milligrams Clears Asexual Stage Parasites but Not Mature Gametocytes from the Blood of Healthy Subjects Experimentally Infected with Plasmodium falciparum. Antimicrob Agents Chemother 2019; 63:AAC.01837-18. [PMID: 30858218 PMCID: PMC6437518 DOI: 10.1128/aac.01837-18] [Citation(s) in RCA: 27] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 01/25/2019] [Indexed: 12/19/2022] Open
Abstract
DSM265 is a novel antimalarial drug in clinical development that acts as a selective inhibitor of Plasmodium dihydroorotate dehydrogenase. In a previous phase 1b study, a single 150-mg dose of DSM265 showed partial efficacy against experimentally induced blood-stage Plasmodium falciparum malaria (IBSM). DSM265 is a novel antimalarial drug in clinical development that acts as a selective inhibitor of Plasmodium dihydroorotate dehydrogenase. In a previous phase 1b study, a single 150-mg dose of DSM265 showed partial efficacy against experimentally induced blood-stage Plasmodium falciparum malaria (IBSM). Pharmacokinetic/pharmacodynamic modeling predicted a human efficacious dose of 340 mg. The primary objectives of the current study were to determine the safety and efficacy of a single oral 400-mg dose of DSM265 against P. falciparum in the IBSM model. Eight healthy participants were inoculated intravenously with 2,800 parasites and treated with DSM265 7 days later. Unexpectedly, one participant did not develop parasitemia during the study. All other participants developed parasitemia, with the complete clearance of asexual parasites occurring following DSM265 treatment. All seven subjects also became gametocytemic. The secondary objectives were to investigate the gametocytocidal and transmission-blocking activity of a second 400-mg dose of DSM265, which was administered 23 days after inoculation. Gametocytes were not cleared by the second dose of DSM265, and transmission-blocking activity could not be determined due to low gametocyte densities. Three DSM265-related adverse events occurred, including a cutaneous rash in one subject on the day of the second DSM265 dose. The results obtained in this study support the prediction of the efficacious dose of DSM265 and provide further evidence that DSM265 is generally safe and well tolerated. In addition, this study confirms preclinical data indicating that DSM265 permits the development and maturation of gametocytes and does not clear mature circulating gametocytes. (This study has been registered at ClinicalTrials.gov under identifier NCT02573857.)
Collapse
|
11
|
Romero AH. Role of Trifluoromethyl Substitution in Design of Antimalarial Quinolones: a Comprehensive Review. Top Curr Chem (Cham) 2019; 377:9. [PMID: 30835005 DOI: 10.1007/s41061-019-0234-7] [Citation(s) in RCA: 14] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/24/2018] [Accepted: 02/22/2019] [Indexed: 10/27/2022]
Abstract
Malaria represents a significant health issue, and novel effective drugs are needed to address parasite resistance that has emerged to the current drug arsenal. The most popular antimalarial drugs are focused on the 7-chloro-4-aminoquinoline [e.g., chloroquine (CQ), amodiaquine (AQ), isoquine (IQ), and tebuquine (TBQ)], artemisinin, and atovaquone systems. Recently, endochin has been used as a platform to design a variety of novel potent and safe antimalarial agents named endochin-like quinolones (ELQs). Also, antimalarial quinolones have been constructed from other quinolones drugs such as ICI-56780 and floxacrine. Trifluoromethyl substitution has provided a significant increase in the antimalarial response of many of the designed ELQs against Plasmodium-resistant strains and for in vivo models. In particular, attachment of a substituted trifluoromethoxy (or trifluoromethyl in some cases) biaryl side chain at 2-, 3-, 4-, or 6-position of the quinolone core has shown to be crucially important to generate selective and potent novel ELQs. Furthermore, 6-chloro and 7-methoxy moieties on the quinolone core have been identified as essential pharmacophores when the trifluoromethoxy biaryl side chain is placed at 2- or 3-position of the quinolone core. Methyl or ethyl ester attached at 3-position is essential when the trifluoromethoxy aryl side chain is attached at 6- or 7-position of the quinolone core. Some promising ELQs are currently under clinical trials, representing an excellent platform for the design of new potent, selective, effective, and safe antimalarial drugs against emergent resistance malarial models.
Collapse
Affiliation(s)
- Angel H Romero
- Cátedra de Química General, Facultad de Farmacia, Universidad Central de Venezuela, Los Chaguaramos, Caracas, 1041-A, Venezuela.
| |
Collapse
|
12
|
Ssemaganda A, Giddam AK, Zaman M, Skwarczynski M, Toth I, Stanisic DI, Good MF. Induction of Plasmodium-Specific Immune Responses Using Liposome-Based Vaccines. Front Immunol 2019; 10:135. [PMID: 30774635 PMCID: PMC6367261 DOI: 10.3389/fimmu.2019.00135] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2018] [Accepted: 01/16/2019] [Indexed: 12/30/2022] Open
Abstract
In the development of vaccines, the ability to initiate both innate and subsequent adaptive immune responses need to be considered. Live attenuated vaccines achieve this naturally, while inactivated and sub-unit vaccines generally require additional help provided through delivery systems and/or adjuvants. Liposomes present an attractive adjuvant/delivery system for antigens. Here, we review the key aspects of immunity against Plasmodium parasites, liposome design considerations and their current application in the development of a malaria vaccine.
Collapse
Affiliation(s)
| | | | - Mehfuz Zaman
- Institute for Glycomics, Griffith University, Southport, QLD, Australia
| | - Mariusz Skwarczynski
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
| | - Istvan Toth
- School of Chemistry and Molecular Biosciences, The University of Queensland, Brisbane, QLD, Australia
- School of Pharmacy, The University of Queensland, Brisbane, QLD, Australia
- Institute for Molecular Bioscience, The University of Queensland, Brisbane, QLD, Australia
| | | | - Michael F. Good
- Institute for Glycomics, Griffith University, Southport, QLD, Australia
| |
Collapse
|
13
|
Controlled Infection Immunization Using Delayed Death Drug Treatment Elicits Protective Immune Responses to Blood-Stage Malaria Parasites. Infect Immun 2018; 87:IAI.00587-18. [PMID: 30323025 PMCID: PMC6300636 DOI: 10.1128/iai.00587-18] [Citation(s) in RCA: 12] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/27/2018] [Accepted: 09/23/2018] [Indexed: 01/27/2023] Open
Abstract
Naturally acquired immunity to malaria is robust and protective against all strains of the same species of Plasmodium. This develops as a result of repeated natural infection, taking several years to develop. Naturally acquired immunity to malaria is robust and protective against all strains of the same species of Plasmodium. This develops as a result of repeated natural infection, taking several years to develop. Evidence suggests that apoptosis of immune lymphocytes due to uncontrolled parasite growth contributes to the slow acquisition of immunity. To hasten and augment the development of natural immunity, we studied controlled infection immunization (CII) using low-dose exposure to different parasite species (Plasmodium chabaudi, P. yoelii, or P. falciparum) in two rodent systems (BALB/c and C57BL/6 mice) and in human volunteers, with drug therapy commencing at the time of initiation of infection. CIIs with infected erythrocytes and in conjunction with doxycycline or azithromycin, which are delayed death drugs targeting the parasite’s apicoplast, allowed extended exposure to parasites at low levels. In turn, this induced strong protection against homologous challenge in all immunized mice. We show that P. chabaudi/P. yoelii infection initiated at the commencement of doxycycline therapy leads to cellular or antibody-mediated protective immune responses in mice, with a broad Th1 cytokine response providing the best correlate of protection against homologous and heterologous species of Plasmodium. P. falciparum CII with doxycycline was additionally tested in a pilot clinical study (n = 4) and was found to be well tolerated and immunogenic, with immunological studies primarily detecting increased cell-associated immune responses. Furthermore, we report that a single dose of the longer-acting drug, azithromycin, given to mice (n = 5) as a single subcutaneous treatment at the initiation of infection controlled P. yoelii infection and protected all mice against subsequent challenge.
Collapse
|
14
|
Stanisic DI, Fink J, Mayer J, Coghill S, Gore L, Liu XQ, El-Deeb I, Rodriguez IB, Powell J, Willemsen NM, De SL, Ho MF, Hoffman SL, Gerrard J, Good MF. Vaccination with chemically attenuated Plasmodium falciparum asexual blood-stage parasites induces parasite-specific cellular immune responses in malaria-naïve volunteers: a pilot study. BMC Med 2018; 16:184. [PMID: 30293531 PMCID: PMC6174572 DOI: 10.1186/s12916-018-1173-9] [Citation(s) in RCA: 28] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/25/2018] [Accepted: 09/11/2018] [Indexed: 12/21/2022] Open
Abstract
BACKGROUND The continuing morbidity and mortality associated with infection with malaria parasites highlights the urgent need for a vaccine. The efficacy of sub-unit vaccines tested in clinical trials in malaria-endemic areas has thus far been disappointing, sparking renewed interest in the whole parasite vaccine approach. We previously showed that a chemically attenuated whole parasite asexual blood-stage vaccine induced CD4+ T cell-dependent protection against challenge with homologous and heterologous parasites in rodent models of malaria. METHODS In this current study, we evaluated the immunogenicity and safety of chemically attenuated asexual blood-stage Plasmodium falciparum (Pf) parasites in eight malaria-naïve human volunteers. Study participants received a single dose of 3 × 107 Pf pRBC that had been treated in vitro with the cyclopropylpyrolloindole analogue, tafuramycin-A. RESULTS We demonstrate that Pf asexual blood-stage parasites that are completely attenuated are immunogenic, safe and well tolerated in malaria-naïve volunteers. Following vaccination with a single dose, species and strain transcending Plasmodium-specific T cell responses were induced in recipients. This included induction of Plasmodium-specific lymphoproliferative responses, T cells secreting the parasiticidal cytokines, IFN-γ and TNF, and CD3+CD45RO+ memory T cells. Pf-specific IgG was not detected. CONCLUSIONS This is the first clinical study evaluating a whole parasite blood-stage malaria vaccine. Following administration of a single dose of completely attenuated Pf asexual blood-stage parasites, Plasmodium-specific T cell responses were induced while Pf-specific antibodies were not detected. These results support further evaluation of this chemically attenuated vaccine in humans. TRIAL REGISTRATION Trial registration: ACTRN12614000228684 . Registered 4 March 2014.
Collapse
Affiliation(s)
- Danielle I Stanisic
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia.
| | - James Fink
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Johanna Mayer
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Sarah Coghill
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Letitia Gore
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Xue Q Liu
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Ibrahim El-Deeb
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Ingrid B Rodriguez
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Jessica Powell
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Nicole M Willemsen
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Sai Lata De
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | - Mei-Fong Ho
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia
| | | | - John Gerrard
- Gold Coast University Hospital, 1 Hospital Blvd, Southport, Queensland, Australia
| | - Michael F Good
- Institute for Glycomics, Griffith University, Parklands Drive, Southport, Queensland, Australia.
| |
Collapse
|
15
|
Lau CL, Ramsey L, Mills LC, Furuya-Kanamori L, Mills DJ. Drug-free Holidays: Compliance, Tolerability, and Acceptability of a 3-Day Atovaquone/Proguanil Schedule for Pretravel Malaria Chemoprophylaxis in Australian Travelers. Clin Infect Dis 2018; 69:137-143. [DOI: 10.1093/cid/ciy854] [Citation(s) in RCA: 6] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2018] [Accepted: 09/28/2018] [Indexed: 11/13/2022] Open
Affiliation(s)
- Colleen L Lau
- Research School of Population Health, Australian National University, Canberra, Australian Capital Territory
- Dr Deb the Travel Doctor, Travel Medicine Alliance, Brisbane, Queensland
| | - Lani Ramsey
- Travel-Bug Vaccination Clinic, Travel Medicine Alliance, Adelaide, South Australia, Australia
| | - Laura C Mills
- Dr Deb the Travel Doctor, Travel Medicine Alliance, Brisbane, Queensland
| | - Luis Furuya-Kanamori
- Research School of Population Health, Australian National University, Canberra, Australian Capital Territory
- Department of Population Medicine, College of Medicine, Qatar University, Doha
| | - Deborah J Mills
- Dr Deb the Travel Doctor, Travel Medicine Alliance, Brisbane, Queensland
| |
Collapse
|
16
|
Savelkoel J, Binnendijk KH, Spijker R, van Vugt M, Tan K, Hänscheid T, Schlagenhauf P, Grobusch MP. Abbreviated atovaquone-proguanil prophylaxis regimens in travellers after leaving malaria-endemic areas: A systematic review. Travel Med Infect Dis 2018; 21:3-20. [PMID: 29242073 PMCID: PMC10956543 DOI: 10.1016/j.tmaid.2017.12.005] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/24/2017] [Accepted: 12/09/2017] [Indexed: 10/18/2022]
Abstract
BACKGROUND We evaluated existing data on the prophylactic efficacy of atovaquone-proguanil (AP) in order to determine whether prophylaxis in travellers can be discontinued on the day of return from a malaria-endemic area instead of seven days after return as per currently recommended post-travel schedule. METHODS PubMed and Embase databases were searched to identify relevant studies. This PROSPERO-registered systematic review followed PRISMA guidelines. The search strategy included terms or synonyms relevant to AP combined with terms to identify articles relating to prophylactic use of AP and inhibitory and half-life properties of AP. Studies considered for inclusion were: randomized controlled trials, cohort studies, quasi-experimental studies, open-label trials, patient-control studies, cross-sectional studies; as well as case-series and non-clinical studies. Data on study design, characteristics of participants, interventions, and outcomes were extracted. Primary outcomes considered relevant were prophylactic efficacy and prolonged inhibitory activity and half-life properties of AP. RESULTS The initial search identified 1,482 publications, of which 40 were selected based on screening. Following full text review, 32 studies were included and categorized into two groups, namely studies in support of the current post-travel regimen (with a total of 2,866 subjects) and studies in support of an alternative regimen (with a total of 533 subjects). CONCLUSION There is limited direct and indirect evidence to suggest that an abbreviated post-travel regimen for AP may be effective. Proguanil, however, has a short half-life and is essential for the synergistic effect of the combination. Stopping AP early may result in mono-prophylaxis with atovaquone and possibly select for atovaquone-resistant parasites. Furthermore, the quality of the studies in support of the current post-travel regimen outweighs the quality of the studies in support of an alternative short, post-travel regimen, and the total sample size of the studies to support stopping AP early comprises a small percentage of the total sample size of the studies performed to establish the efficacy of the current AP regimen. Additional research is required - especially from studies evaluating impact on malaria parasitaemia and clinical illness and conducted among travellers in high malaria risk settings - before an abbreviated regimen can be recommended in current practice. PROSPERO REGISTRATION NUMBER CRD42017055244.
Collapse
Affiliation(s)
- Jelmer Savelkoel
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Academic Medical Center, University of Amsterdam, Meibergdreef 9, DD1100 Amsterdam, The Netherlands
| | - Klaas Hendrik Binnendijk
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Academic Medical Center, University of Amsterdam, Meibergdreef 9, DD1100 Amsterdam, The Netherlands
| | - Rene Spijker
- Medical Library, Academic Medical Center, University of Amsterdam, Meibergdreef 9, DD1100 Amsterdam, The Netherlands
| | - Michèle van Vugt
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Academic Medical Center, University of Amsterdam, Meibergdreef 9, DD1100 Amsterdam, The Netherlands
| | - Kathrine Tan
- Malaria Branch, Centers for Disease Control and Prevention, Atlanta, GA, USA
| | - Thomas Hänscheid
- Instituto de Medicina Molecular and Department of Microbiology, University of Lisbon, Lisbon, Portugal
| | - Patricia Schlagenhauf
- University of Zürich Travel Clinic, WHO Collaborating Centre for Travellers' Health, Institute for Epidemiology, Biostatistics and Prevention, University of Zurich, Zurich, Switzerland
| | - Martin Peter Grobusch
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Academic Medical Center, University of Amsterdam, Meibergdreef 9, DD1100 Amsterdam, The Netherlands.
| |
Collapse
|
17
|
Abstract
Controlled human malaria infection (CHMI) entails deliberate infection with malaria parasites either by mosquito bite or by direct injection of sporozoites or parasitized erythrocytes. When required, the resulting blood-stage infection is curtailed by the administration of antimalarial drugs. Inducing a malaria infection via inoculation with infected blood was first used as a treatment (malariotherapy) for neurosyphilis in Europe and the United States in the early 1900s. More recently, CHMI has been applied to the fields of malaria vaccine and drug development, where it is used to evaluate products in well-controlled early-phase proof-of-concept clinical studies, thus facilitating progression of only the most promising candidates for further evaluation in areas where malaria is endemic. Controlled infections have also been used to immunize against malaria infection. Historically, CHMI studies have been restricted by the need for access to insectaries housing infected mosquitoes or suitable malaria-infected individuals. Evaluation of vaccine and drug candidates has been constrained in these studies by the availability of a limited number of Plasmodium falciparum isolates. Recent advances have included cryopreservation of sporozoites, the manufacture of well-characterized and genetically distinct cultured malaria cell banks for blood-stage infection, and the availability of Plasmodium vivax-specific reagents. These advances will help to accelerate malaria vaccine and drug development by making the reagents for CHMI more widely accessible and also enabling a more rigorous evaluation with multiple parasite strains and species. Here we discuss the different applications of CHMI, recent advances in the use of CHMI, and ongoing challenges for consideration.
Collapse
|
18
|
Abstract
Malaria vaccine development has been dominated by the subunit approach; however, many subunit vaccine candidates have had limited efficacy in settings of malaria endemicity. As our search for an efficacious malaria vaccine continues, the development of a whole-organism vaccine is now receiving much scrutiny. One strategy currently being explored in the development of a whole-organism vaccine involves chemical attenuation of the malaria parasite. In vivo and in vitro chemical attenuation of both liver-stage and blood-stage Plasmodium parasites has been investigated. Here, we discuss both approaches of chemical attenuation in the development of a whole-organism vaccine against malaria.
Collapse
|
19
|
Atovaquone and ELQ-300 Combination Therapy as a Novel Dual-Site Cytochrome bc1 Inhibition Strategy for Malaria. Antimicrob Agents Chemother 2016; 60:4853-9. [PMID: 27270285 DOI: 10.1128/aac.00791-16] [Citation(s) in RCA: 41] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/07/2016] [Accepted: 05/24/2016] [Indexed: 12/31/2022] Open
Abstract
Antimalarial combination therapies play a crucial role in preventing the emergence of drug-resistant Plasmodium parasites. Although artemisinin-based combination therapies (ACTs) comprise the majority of these formulations, inhibitors of the mitochondrial cytochrome bc1 complex (cyt bc1) are among the few compounds that are effective for both acute antimalarial treatment and prophylaxis. There are two known sites for inhibition within cyt bc1: atovaquone (ATV) blocks the quinol oxidase (Qo) site of cyt bc1, while some members of the endochin-like quinolone (ELQ) family, including preclinical candidate ELQ-300, inhibit the quinone reductase (Qi) site and retain full potency against ATV-resistant Plasmodium falciparum strains with Qo site mutations. Here, we provide the first in vivo comparison of ATV, ELQ-300, and combination therapy consisting of ATV plus ELQ-300 (ATV:ELQ-300), using P. yoelii murine models of malaria. In our monotherapy assessments, we found that ATV functioned as a single-dose curative compound in suppressive tests whereas ELQ-300 demonstrated a unique cumulative dosing effect that successfully blocked recrudescence even in a high-parasitemia acute infection model. ATV:ELQ-300 therapy was highly synergistic, and the combination was curative with a single combined dose of 1 mg/kg of body weight. Compared to the ATV:proguanil (Malarone) formulation, ATV:ELQ-300 was more efficacious in multiday, acute infection models and was equally effective at blocking the emergence of ATV-resistant parasites. Ultimately, our data suggest that dual-site inhibition of cyt bc1 is a valuable strategy for antimalarial combination therapy and that Qi site inhibitors such as ELQ-300 represent valuable partner drugs for the clinically successful Qo site inhibitor ATV.
Collapse
|
20
|
Abstract
There have been significant decreases in malaria mortality and morbidity in the last 10-15 years, and the most advanced pre-erythrocytic malaria vaccine, RTS,S, received a positive opinion from European regulators in July 2015. However, no blood-stage vaccine has reached a phase III trial. The first part of this review summarizes the pros and cons of various assays and models that have been and will be used to predict the efficacy of blood-stage vaccines. In the second part, blood-stage vaccine candidates that showed some efficacy in human clinical trials or controlled human malaria infection models are discussed. Then, candidates under clinical investigation are described in the third part, and other novel candidates and strategies are reviewed in the last part.
Collapse
Affiliation(s)
- Kazutoyo Miura
- a Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases , National Institutes of Health , Rockville , MD , USA
| |
Collapse
|
21
|
Abstract
Naturally acquired immunity to the blood-stage of the malaria parasite develops slowly in areas of high endemicity, but is not sterilizing. It manifests as a reduction in parasite density and clinical symptoms. Immunity as a result of blood-stage vaccination has not yet been achieved in humans, although there are many animal models where vaccination has been successful. The development of a blood-stage vaccine has been complicated by a number of factors including limited knowledge of human-parasite interactions and which antigens and immune responses are critical for protection. Opinion is divided as to whether this vaccine should aim to accelerate the acquisition of responses acquired following natural exposure, or whether it should induce a different response. Animal and experimental human models suggest that cell-mediated immune responses can control parasite growth, but these responses can also contribute to significant immunopathology if unregulated. They are largely ignored in most blood-stage malaria vaccine development strategies. Here, we discuss key observations relating to cell-mediated immune responses in the context of experimental human systems and field studies involving naturally exposed individuals and how this may inform the development of a blood-stage malaria vaccine.
Collapse
|
22
|
Whole organism blood stage vaccines against malaria. Vaccine 2015; 33:7469-75. [DOI: 10.1016/j.vaccine.2015.09.057] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2015] [Revised: 09/04/2015] [Accepted: 09/14/2015] [Indexed: 11/17/2022]
|
23
|
Abstract
Although it is more than a decade since the parasite genome information was obtained, standardized novel genome-wide selection/prioritization strategies for candidacy of malaria vaccine antigens are still sought. In the quest to systematically identify candidates, it is impossible to overemphasize the usefulness of wheat germ cell-free technology in expressing quality proteins for the post-genome vaccine candidate discovery.
Collapse
Affiliation(s)
- Eizo Takashima
- a Division of Malaria Research, Proteo-Science Center , Ehime University , Matsuyama , Ehime 790-8577 , Japan
| | - Masayuki Morita
- a Division of Malaria Research, Proteo-Science Center , Ehime University , Matsuyama , Ehime 790-8577 , Japan
| | - Takafumi Tsuboi
- a Division of Malaria Research, Proteo-Science Center , Ehime University , Matsuyama , Ehime 790-8577 , Japan
| |
Collapse
|
24
|
Hodgson SH, Juma E, Salim A, Magiri C, Njenga D, Molyneux S, Njuguna P, Awuondo K, Lowe B, Billingsley PF, Cole AO, Ogwang C, Osier F, Chilengi R, Hoffman SL, Draper SJ, Ogutu B, Marsh K. Lessons learnt from the first controlled human malaria infection study conducted in Nairobi, Kenya. Malar J 2015; 14:182. [PMID: 25927522 PMCID: PMC4416324 DOI: 10.1186/s12936-015-0671-x] [Citation(s) in RCA: 55] [Impact Index Per Article: 6.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/20/2015] [Accepted: 03/15/2015] [Indexed: 11/30/2022] Open
Abstract
BACKGROUND Controlled human malaria infection (CHMI) studies, in which healthy volunteers are infected with Plasmodium falciparum to assess the efficacy of novel malaria vaccines and drugs, have become a vital tool to accelerate vaccine and drug development. CHMI studies provide a cost-effective and expeditious way to circumvent the use of large-scale field efficacy studies to deselect intervention candidates. However, to date few modern CHMI studies have been performed in malaria-endemic countries. METHODS An open-label, randomized pilot CHMI study was conducted using aseptic, purified, cryopreserved, infectious P. falciparum sporozoites (SPZ) (Sanaria® PfSPZ Challenge) administered intramuscularly (IM) to healthy Kenyan adults (n = 28) with varying degrees of prior exposure to P. falciparum. The purpose of the study was to establish the PfSPZ Challenge CHMI model in a Kenyan setting with the aim of increasing the international capacity for efficacy testing of malaria vaccines and drugs, and allowing earlier assessment of efficacy in a population for which interventions are being developed. This was part of the EDCTP-funded capacity development of the CHMI platform in Africa. DISCUSSION This paper discusses in detail lessons learnt from conducting the first CHMI study in Kenya. Issues pertinent to the African setting, including community sensitization, consent and recruitment are considered. Detailed reasoning regarding the study design (for example, dose and route of administration of PfSPZ Challenge, criteria for grouping volunteers according to prior exposure to malaria and duration of follow-up post CHMI) are given and changes other centres may want to consider for future studies are suggested. CONCLUSIONS Performing CHMI studies in an African setting presents unique but surmountable challenges and offers great opportunity for acceleration of malaria vaccine and drug development. The reflections in this paper aim to aid other centres and partners intending to use the CHMI model in Africa.
Collapse
Affiliation(s)
| | - Elizabeth Juma
- Centre for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya.
- Centre for Research in Therapeutic Sciences, Strathmore University, Nairobi, Kenya.
| | - Amina Salim
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| | - Charles Magiri
- Centre for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya.
| | - Daniel Njenga
- Centre for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya.
| | - Sassy Molyneux
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| | - Patricia Njuguna
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| | - Ken Awuondo
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| | - Brett Lowe
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| | | | - Andrew O Cole
- Centre for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya.
- Centre for Research in Therapeutic Sciences, Strathmore University, Nairobi, Kenya.
| | - Caroline Ogwang
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| | - Faith Osier
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| | - Roma Chilengi
- Centre for Infectious Disease Research in Zambia, Lusaka, Zambia.
| | | | | | - Bernhards Ogutu
- Centre for Clinical Research, Kenya Medical Research Institute, Nairobi, Kenya.
- Centre for Research in Therapeutic Sciences, Strathmore University, Nairobi, Kenya.
| | - Kevin Marsh
- Kenya Medical Research Institute - Wellcome Trust, Centre for Geographical Medical Research (Coast), Kilifi, Kenya.
| |
Collapse
|
25
|
Abstract
The development of a highly effective malaria vaccine remains a key goal to aid in the control and eventual eradication of this devastating parasitic disease. The field has made huge strides in recent years, with the first-generation vaccine RTS,S showing modest efficacy in a Phase III clinical trial. The updated 2030 Malaria Vaccine Technology Roadmap calls for a second generation vaccine to achieve 75% efficacy over two years for both Plasmodium falciparum and Plasmodium vivax, and for a vaccine that can prevent malaria transmission. Whole-parasite immunisation approaches and combinations of pre-erythrocytic subunit vaccines are now reporting high-level efficacy, whilst exciting new approaches to the development of blood-stage and transmission-blocking vaccine subunit components are entering clinical development. The development of a highly effective multi-component multi-stage subunit vaccine now appears to be a realistic ambition. This review will cover these recent developments in malaria vaccinology.
Collapse
|
26
|
Leshem E, Meltzer E, Stienlauf S, Kopel E, Schwartz E. Effectiveness of short prophylactic course of atovaquone-proguanil in travelers to sub-saharan Africa. J Travel Med 2014; 21:82-5. [PMID: 24298915 DOI: 10.1111/jtm.12088] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 06/08/2013] [Revised: 08/13/2013] [Accepted: 09/24/2013] [Indexed: 01/23/2023]
Abstract
BACKGROUND Current guidelines recommend continuation of atovaquone-proguanil (AP) malaria prophylaxis for 7 days after leaving Plasmodium falciparum endemic areas. Evidence from clinical studies suggests that discontinuation of AP 1 day after exposure ends may be safe and effective. Our objective was to assess the effectiveness of short-course AP prophylaxis among travelers to sub-Saharan Africa. METHODS To detect prophylactic failures associated with short-course AP prophylaxis discontinued 1 day after return, we conducted active surveillance during the years 2010 and 2011, by a retrospective telephone survey 1 to 6 months after travelers' return. Passive surveillance data were obtained from the Israel Ministry of Health (MOH) malaria registry. RESULTS Among 485 travelers to sub-Saharan Africa (cumulative exposure of 4,979 days), 421 (87%) discontinued AP 1 day after leaving the endemic region (cumulative exposure of 4,337 days). None of the 485 travelers reported malaria infection. The MOH malaria registry survey included 363 P. falciparum-infected patients during the years 2003 to 2011. The majority (n = 305; 84%) did not use any malaria prophylaxis. None of the patients had used AP (neither regular nor short course AP) for malaria prophylaxis. CONCLUSIONS We did not detect prophylaxis failures among a group of travelers who discontinued AP prophylaxis 1 day after leaving malaria-endemic areas. Passive surveillance in Israel did not detect any P. falciparum cases among AP users. We recommend further validation of our findings by clinical trials, prospective studies, and active surveillance in larger cohorts to assess the effectiveness of short-course AP prophylaxis in travelers.
Collapse
Affiliation(s)
- Eyal Leshem
- The Center for Geographic Medicine, The Chaim Sheba Medical Center, Tel Hashomer, Israel
| | | | | | | | | |
Collapse
|
27
|
Grobusch MP. Malaria chemoprophylaxis with atovaquone-proguanil: is a shorter regimen fully protective? J Travel Med 2014; 21:79-81. [PMID: 24593022 DOI: 10.1111/jtm.12100] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/29/2013] [Revised: 12/09/2013] [Accepted: 12/09/2013] [Indexed: 12/01/2022]
Affiliation(s)
- Martin P Grobusch
- Center of Tropical Medicine and Travel Medicine, Department of Infectious Diseases, Division of Internal Medicine, Academic Medical Center, University of Amsterdam, Amsterdam, The Netherlands; Institute of Infectious Diseases and Molecular Medicine (IIDMM), University of Cape Town, Cape Town, South Africa; Centre de Récherches Médicales (CERMEL), Lambaréné, Gabon; Institute of Tropical Medicine, University of Tübingen, Tübingen, Germany
| |
Collapse
|
28
|
Good MF, Reiman JM, Rodriguez IB, Ito K, Yanow SK, El-Deeb IM, Batzloff MR, Stanisic DI, Engwerda C, Spithill T, Hoffman SL, Lee M, McPhun V. Cross-species malaria immunity induced by chemically attenuated parasites. J Clin Invest 2013; 123:66634. [PMID: 23863622 PMCID: PMC4011145 DOI: 10.1172/jci66634] [Citation(s) in RCA: 68] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2012] [Accepted: 04/26/2013] [Indexed: 01/29/2023] Open
Abstract
Vaccine development for the blood stages of malaria has focused on the induction of antibodies to parasite surface antigens, most of which are highly polymorphic. An alternate strategy has evolved from observations that low-density infections can induce antibody-independent immunity to different strains. To test this strategy, we treated parasitized red blood cells from the rodent parasite Plasmodium chabaudi with seco-cyclopropyl pyrrolo indole analogs. These drugs irreversibly alkylate parasite DNA, blocking their ability to replicate. After administration in mice, DNA from the vaccine could be detected in the blood for over 110 days and a single vaccination induced profound immunity to different malaria parasite species. Immunity was mediated by CD4+ T cells and was dependent on the red blood cell membrane remaining intact. The human parasite, Plasmodium falciparum, could also be attenuated by treatment with seco-cyclopropyl pyrrolo indole analogs. These data demonstrate that vaccination with chemically attenuated parasites induces protective immunity and provide a compelling rationale for testing a blood-stage parasite-based vaccine targeting human Plasmodium species.
Collapse
|
29
|
Protection against malaria after immunization by chloroquine prophylaxis and sporozoites is mediated by preerythrocytic immunity. Proc Natl Acad Sci U S A 2013; 110:7862-7. [PMID: 23599283 DOI: 10.1073/pnas.1220360110] [Citation(s) in RCA: 147] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
Volunteers immunized under chloroquine chemoprophylaxis with Plasmodium falciparum sporozoites (CPS) develop complete, long-lasting protection against homologous sporozoite challenge. Chloroquine affects neither sporozoites nor liver-stages, but kills only asexual forms in erythrocytes once released from the liver into the circulation. Consequently, CPS immunization exposes the host to antigens from both preerythrocytic and blood stages, and induced immunity might target either of these stages. We therefore explored the life cycle stage specificity of CPS-induced protection. Twenty-five malaria-naïve volunteers were enrolled in a clinical trial, 15 of whom received CPS immunization. Five immunized subjects and five controls received a sporozoite challenge by mosquito bites, whereas nine immunized and five control subjects received an i.v. challenge with P. falciparum-infected erythrocytes. The latter approach completely bypasses preerythrocytic stages, enabling a direct comparison of protection against either life cycle stage. CPS-immunized subjects (13 of 14) developed anticircumsporozoite antibodies, whereas only one volunteer generated minimal titers against typical blood-stage antigens. IgG from CPS-immunized volunteers did not inhibit asexual blood-stage growth in vitro. All CPS-immunized subjects (5 of 5) were protected against sporozoite challenge. In contrast, nine of nine CPS-immunized subjects developed parasitemia after blood-stage challenge, with identical prepatent periods and blood-stage multiplication rates compared with controls. Intravenously challenged CPS-immunized subjects showed earlier fever and increased plasma concentrations of inflammatory markers D-dimer, IFN-γ, and monokine induced by IFN-γ than i.v. challenged controls. The complete lack of protection against blood-stage challenge indicates that CPS-induced protection is mediated by immunity against preerythrocytic stages. However, evidence is presented for immune recognition of P. falciparum-infected erythrocytes, suggesting memory responses unable to generate functional immunity.
Collapse
|
30
|
Engwerda CR, Minigo G, Amante FH, McCarthy JS. Experimentally induced blood stage malaria infection as a tool for clinical research. Trends Parasitol 2012; 28:515-21. [PMID: 23041118 DOI: 10.1016/j.pt.2012.09.001] [Citation(s) in RCA: 56] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2012] [Revised: 09/10/2012] [Accepted: 09/13/2012] [Indexed: 11/29/2022]
Abstract
A system for experimentally induced blood stage malaria infection (IBSM) with Plasmodium falciparum by direct intravenous inoculation of infected erythrocytes was developed at the Queensland Institute of Medical Research (QIMR) more than 15 years ago. Since that time, this system has been used in several studies to investigate the protective effect of vaccines, the clearance kinetics of parasites following drug treatment, and to improve understanding of the early events in blood stage infection. In this article, we will review the development of IBSM and the applications for which it is being employed. We will discuss the advantages and disadvantages of IBSM, and finish by describing some exciting new areas of research that have been made possible by this system.
Collapse
|
31
|
Duncan CJA, Draper SJ. Controlled human blood stage malaria infection: current status and potential applications. Am J Trop Med Hyg 2012; 86:561-5. [PMID: 22492136 DOI: 10.4269/ajtmh.2012.11-0504] [Citation(s) in RCA: 42] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Abstract
Controlled human malaria infection by blood stage parasite (BSP) inoculation is an alternative to the well-established model of infection with Plasmodium falciparum sporozoites delivered by mosquito bites. The BSP model has been utilized less frequently, but its use is increasing. Advantages of BSP challenge include greater ease of administration, better standardization of the infecting dose per volunteer, and good inter-study reproducibility of in vivo parasite dynamics. Recently, a surprising reduction in clinical symptoms at microscopic patency in the BSP model has been identified, which has an undefined and intriguing pathophysiologic basis, but may make this approach more acceptable to volunteers. We summarize clinical, parasitologic, and immunologic data from all BSP challenges to date, explore differences between the BSP and sporozoite models, and propose future applications for BSP challenge.
Collapse
|
32
|
Duncan CJA, Hill AVS, Ellis RD. Can growth inhibition assays (GIA) predict blood-stage malaria vaccine efficacy? Hum Vaccin Immunother 2012; 8:706-14. [PMID: 22508415 DOI: 10.4161/hv.19712] [Citation(s) in RCA: 64] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
An effective vaccine against P. falciparum malaria remains a global health priority. Blood-stage vaccines are an important component of this effort, with some indications of recent progress. However only a fraction of potential blood-stage antigens have been tested, highlighting a critical need for efficient down-selection strategies. Functional in vitro assays such as the growth/invasion inhibition assays (GIA) are widely used, but it is unclear whether GIA activity correlates with protection or predicts vaccine efficacy. While preliminary data in controlled human malaria infection (CHMI) studies indicate a possible association between in vitro and in vivo parasite growth rates, there have been conflicting results of immunoepidemiology studies, where associations with exposure rather than protection have been observed. In addition, GIA-interfering antibodies in vaccinated individuals from endemic regions may limit assay sensitivity in heavily malaria-exposed populations. More work is needed to establish the utility of GIA for blood-stage vaccine development.
Collapse
|
33
|
In vitro antimalarial activity and drug interactions of fenofibric acid. Antimicrob Agents Chemother 2012; 56:2814-8. [PMID: 22430967 DOI: 10.1128/aac.05076-11] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Plasmodium falciparum has developed resistance to most available treatments, underscoring the need for novel antimalarial drugs. Fibrates are lipid-modifying agents used to reduce morbidity and mortality associated with cardiovascular disease. They may have antimalarial activity through modulation of P-glycoprotein and ATP-binding cassette subfamily A member (ABC-1)-mediated nutrient transport and/or via a putative peroxisome proliferator-activated receptor alpha-like protein. We therefore examined in vitro antimalarial activities of fibrates and their interactions with chloroquine and dihydroartemisinin in chloroquine-sensitive (3D7) and chloroquine-resistant (W2mef) strains of P. falciparum using the conventional isotopic assay microtechnique. A bioassay was used to assess inhibition activities of human plasma after therapeutic fenofibrate doses. Fenofibric acid, the main metabolite of fenofibrate, was the most potent of the fibrates tested, with mean 50% inhibitory concentrations of 152 nM and 1,120 nM for chloroquine-sensitive and -resistant strains, respectively. No synergistic interaction between fibrates and chloroquine or dihydroartemisinin was observed. Plasma fenofibric acid concentrations, quantified by high-performance liquid chromatography in seven healthy volunteers after treatment (mean, 15.3 mg/liter, or 48 μM), inhibited P. falciparum. BLAST analysis revealed the likely presence of an ABC-1 transporter homolog in P. falciparum. Our findings demonstrate that fenofibric acid has activity similar to the activities of conventional antimalarial drugs at concentrations well below those achieved after therapeutic doses. It may inhibit P. falciparum growth by inhibiting intracellular lipid transport.
Collapse
|
34
|
Dow GS, Magill AJ, Ohrt C. Clinical development of new prophylactic antimalarial drugs after the 5th Amendment to the Declaration of Helsinki. Ther Clin Risk Manag 2011; 4:803-19. [PMID: 19209263 PMCID: PMC2621393 DOI: 10.2147/tcrm.s1025] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/30/2022] Open
Abstract
Malaria is of continuing concern in nonimmune traveling populations. Traditionally, antimalarial drugs have been developed as agents for dual indications (treatment and prophylaxis). However, since 2000, when the 5th Amendment to the Declaration of Helsinki (DH2000) was adopted, development of new malaria prophylaxis drugs in this manner has ceased. As a consequence, there may not be any new drugs licensed for this indication in the foreseeable future. Major pharmaceutical companies have interpreted DH2000 to mean that the traditional development paradigm may be considered unethical because of doubt over the likelihood of benefit to endemic populations participating in clinical studies, the use of placebo, and the sustainability of post-trial access to study medications. In this article, we explore the basis of these concerns and suggest that the traditional development paradigm remains ethical under certain circumstances. We also consider alternative approaches that may be more attractive to sponsors as they either do not use placebo, or utilize populations in endemic countries who may unambiguously benefit. These approaches represent the way forward in the future, but are at present unproven in clinical practice, and face numerous regulatory, logistical and technical challenges. Consequently, in the short term, we argue that the traditional clinical development paradigm remains the most feasible approach and is ethical and consistent with the spirit of DH2000 under the appropriate circumstances.
Collapse
Affiliation(s)
- Geoffrey S Dow
- Division of Experimental Therapeutics, Walter Reed Army Institute of Research, Silver Spring, MD, USA.
| | | | | |
Collapse
|
35
|
Deye GA, Miller RS, Miller L, Salas CJ, Tosh D, Macareo L, Smith BL, Fracisco S, Clemens EG, Murphy J, Sousa JC, Dumler JS, Magill AJ. Prolonged Protection Provided by a Single Dose of Atovaquone-Proguanil for the Chemoprophylaxis of Plasmodium falciparum Malaria in a Human Challenge Model. Clin Infect Dis 2011; 54:232-9. [DOI: 10.1093/cid/cir770] [Citation(s) in RCA: 31] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
|
36
|
Chelimo K, Embury PB, Odada Sumba P, Vulule J, Ofulla AV, Long C, Kazura JW, Moormann AM. Age-related differences in naturally acquired T cell memory to Plasmodium falciparum merozoite surface protein 1. PLoS One 2011; 6:e24852. [PMID: 21935482 PMCID: PMC3174209 DOI: 10.1371/journal.pone.0024852] [Citation(s) in RCA: 27] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/10/2011] [Accepted: 08/19/2011] [Indexed: 12/16/2022] Open
Abstract
Naturally acquired immunity to Plasmodium falciparum malaria in malaria holoendemic areas is characterized by the gradual, age-related development of protection against high-density parasitemia and clinical malaria. Animal studies, and less commonly, observations of humans with malaria, suggest that T-cell responses are important in the development and maintenance of this immunity, which is mediated primarily by antibodies that slow repeated cycles of merozoites through erythrocytes. To advance our rather limited knowledge on human T-cell immunity to blood stage malaria infection, we evaluated CD4 and CD8 T-cell effector memory subset responses to the 42 kDa C-terminal fragment of Merozoite Surface Protein 1 (MSP142), a malaria vaccine candidate, by 49 healthy 0.5 to ≥18 year old residents of a holoendemic area in western Kenya. The proportion of individuals with peripheral blood mononuclear cell MSP142 driven IFN-γ ELISPOT responses increased from 20% (2/20) among 0.5–1 year old children to 90% (9/10) of adults ≥18 years (P = 0.01); parallel increases in the magnitude of IFN-γ responses were observed across all age groups (0.5, 1, 2, 5 and ≥18 years, P = 0.001). Less than 1% of total CD4 and CD8 T-cells from both children and adults produced IFN-γ in response to MSP142. However, adults had higher proportions of MSP142 driven IFN-γ secreting CD4 and CD8 effector memory (CD45RA− CD62L−) T-cells than children (CD4: 50.9% vs. 28.8%, P = 0.036; CD8: 52.1% vs. 18.3%, respectively P = 0.009). In contrast, MSP142 driven IFN-γ secreting naïve-like, transitional (CD45RA+ CD62L+) CD4 and CD8 cells were the predominant T-cell subset among children with significantly fewer of these cells in adults (CD4: 34.9% vs. 5.1%, P = 0.002; CD8: 47.0% vs. 20.5%, respectively, P = 0.030). These data support the concept that meaningful age-related differences exist in the quality of T-cell immunity to malaria antigens such as MSP1.
Collapse
Affiliation(s)
- Kiprotich Chelimo
- Center for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
- Maseno University, Maseno, Kenya
| | - Paula B. Embury
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Peter Odada Sumba
- Center for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | - John Vulule
- Center for Global Health Research, Kenya Medical Research Institute, Kisumu, Kenya
| | | | - Carole Long
- Laboratory of Malaria and Vector Research, National Institute of Allergy and Infectious Diseases, National Institutes of Health, Rockville, Maryland, United States of America
| | - James W. Kazura
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
| | - Ann M. Moormann
- Center for Global Health and Diseases, Case Western Reserve University, Cleveland, Ohio, United States of America
- Department of Pediatrics and Department of Quantitative Health Sciences, University of Massachusetts Medical School, Worcester, Massachusetts, United States of America
- * E-mail:
| |
Collapse
|
37
|
Douglas AD, Andrews L, Draper SJ, Bojang K, Milligan P, Gilbert SC, Imoukhuede EB, Hill AVS. Substantially reduced pre-patent parasite multiplication rates are associated with naturally acquired immunity to Plasmodium falciparum. J Infect Dis 2011; 203:1337-40. [PMID: 21459819 DOI: 10.1093/infdis/jir033] [Citation(s) in RCA: 33] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
Naturally acquired immunity to Plasmodium falciparum's asexual blood stage reduces parasite multiplication at microscopically detectable densities. The effect of natural immunity on initial prepatent parasite multiplication during the period following a new infection has been uncertain, contributing to doubt regarding the utility of experimental challenge models for blood-stage vaccine trials. Here we present data revealing that parasite multiplication rates during the initial prepatent period in semi-immune Gambian adults are substantially lower than in malaria-naive participants. This supports the view that a blood-stage vaccine capable of emulating the disease-reducing effect of natural immunity could achieve a detectable effect during the prepatent period.
Collapse
Affiliation(s)
- A D Douglas
- Jenner Institute, Nuffield Department of Medicine, University of Oxford, UK.
| | | | | | | | | | | | | | | |
Collapse
|
38
|
Good MF. A whole parasite vaccine to control the blood stages of Plasmodium: the case for lateral thinking. Trends Parasitol 2011; 27:335-40. [PMID: 21514227 DOI: 10.1016/j.pt.2011.03.003] [Citation(s) in RCA: 17] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/31/2011] [Revised: 03/16/2011] [Accepted: 03/16/2011] [Indexed: 11/29/2022]
Abstract
Now, 27 years following the cloning of malaria antigens with the promise of the rapid development of a malaria vaccine, we face significant obstacles that are belatedly being addressed. Poor immunogenicity of subunit vaccine antigens and significant antigenic diversity of target epitopes represent major hurdles for which there are no clear strategies for a way forward within the current paradigm. Thus, a different paradigm - a vaccine that uses the whole organism - is now being examined. Although most advances in this approach relate to a vaccine for the pre-erythrocytic stages (sporozoites, liver stages), this opinion paper will outline the possibilities of developing a whole parasite vaccine for the blood stage and address some of the challenges for this strategy, which are entirely different to the challenges for a subunit vaccine. It is the view of the author that both vaccine paradigms should be pursued, but that success will come more quickly using the paranormal approach of exposing individuals to ultra-low doses of whole attenuated or killed parasites.
Collapse
Affiliation(s)
- Michael F Good
- Glycomics Institute, Griffith University, Gold Coast, Australia.
| |
Collapse
|
39
|
Douglas AD, de Cassan SC, Dicks MDJ, Gilbert SC, Hill AVS, Draper SJ. Tailoring subunit vaccine immunogenicity: maximizing antibody and T cell responses by using combinations of adenovirus, poxvirus and protein-adjuvant vaccines against Plasmodium falciparum MSP1. Vaccine 2011; 28:7167-78. [PMID: 20937436 PMCID: PMC3404461 DOI: 10.1016/j.vaccine.2010.08.068] [Citation(s) in RCA: 61] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/18/2010] [Revised: 08/12/2010] [Accepted: 08/13/2010] [Indexed: 12/15/2022]
Abstract
Subunit vaccination modalities tend to induce particular immune effector responses. Viral vectors are well known for their ability to induce strong T cell responses, while protein-adjuvant vaccines have been used primarily for induction of antibody responses. Here, we demonstrate in mice using a Plasmodium falciparum merozoite surface protein 1 (PfMSP1) antigen that novel regimes combining adenovirus and poxvirus vectored vaccines with protein antigen in Montanide ISA720 adjuvant can achieve simultaneous antibody and T cell responses which equal, or in some cases surpass, the best immune responses achieved by either the viral vectors or the protein vaccine alone. Such broad responses can be achieved either using three-stage vaccination protocols, or with an equally effective two-stage protocol in which viral vectors are admixed with protein and adjuvant, and were apparent despite the use of a protein antigen that represented only a portion of the viral vector antigen. We describe further possible advantages of viral vectors in achieving consistent antibody priming, enhanced antibody avidity, and cytophilic isotype skew. These data strengthen the evidence that tailored combinations of vaccine platforms can achieve desired combinations of immune responses, and further encourage the co-administration of antibody-inducing recombinant protein vaccines with T cell- and antibody-inducing recombinant viral vectors as one strategy that may achieve protective blood-stage malaria immunity in humans.
Collapse
|
40
|
Crompton PD, Pierce SK, Miller LH. Advances and challenges in malaria vaccine development. J Clin Invest 2010; 120:4168-78. [PMID: 21123952 DOI: 10.1172/jci44423] [Citation(s) in RCA: 188] [Impact Index Per Article: 13.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
Malaria caused by Plasmodium falciparum remains a major public health threat, especially among children and pregnant women in Africa. An effective malaria vaccine would be a valuable tool to reduce the disease burden and could contribute to elimination of malaria in some regions of the world. Current malaria vaccine candidates are directed against human and mosquito stages of the parasite life cycle, but thus far, relatively few proteins have been studied for potential vaccine development. The most advanced vaccine candidate, RTS,S, conferred partial protection against malaria in phase II clinical trials and is currently being evaluated in a phase III trial in Africa. New vaccine targets need to be identified to improve the chances of developing a highly effective malaria vaccine. A better understanding of the mechanisms of naturally acquired immunity to malaria may lead to insights for vaccine development.
Collapse
Affiliation(s)
- Peter D Crompton
- Laboratory of Immunogenetics, National Institute of Allergy and Infectious Disease (NIAID), NIH, Rockville, Maryland, USA
| | | | | |
Collapse
|
41
|
McCall MBB, Sauerwein RW. Interferon-γ--central mediator of protective immune responses against the pre-erythrocytic and blood stage of malaria. J Leukoc Biol 2010; 88:1131-43. [PMID: 20610802 DOI: 10.1189/jlb.0310137] [Citation(s) in RCA: 119] [Impact Index Per Article: 8.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Immune responses against Plasmodium parasites, the causative organisms of malaria, are traditionally dichotomized into pre-erythrocytic and blood-stage components. Whereas the central role of cellular responses in pre-erythrocytic immunity is well established, protection against blood-stage parasites has generally been ascribed to humoral responses. A number of recent studies, however, have highlighted the existence of cellular immunity against blood-stage parasites, in particular, the prominence of IFN-γ production. Here, we have undertaken to chart the contribution of this prototypical cellular cytokine to immunity against pre-erythrocytic and blood-stage parasites. We summarize the various antiparasitic effector functions that IFN-γ serves to induce, review an array of data about its protective effects, and scrutinize evidence for any deleterious, immunopathological outcome in malaria patients. We discuss the activation and contribution of different cellular sources of IFN-γ production during malaria infection and its regulation in relation to exposure. We conclude that IFN-γ forms a central mediator of protective immune responses against pre-erythrocytic and blood-stage malaria parasites and identify a number of implications for rational malaria vaccine development.
Collapse
Affiliation(s)
- Matthew B B McCall
- Department of Medical Microbiology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands
| | | |
Collapse
|
42
|
Moorthy VS, Kieny MP. Reducing empiricism in malaria vaccine design. THE LANCET. INFECTIOUS DISEASES 2010; 10:204-11. [PMID: 20185099 DOI: 10.1016/s1473-3099(09)70329-9] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/19/2022]
Abstract
Gains in the control of malaria and the promising progress of a malaria vaccine that is partly efficacious do not reduce the need for a high-efficacy vaccine in the longer term. Evidence supports the feasibility of developing a highly efficacious malaria vaccine. However, design of candidate malaria vaccines remains empirical and is necessarily based on many unproven assumptions because much of the knowledge needed to design vaccines and to predict efficacy is not available. Data to inform key questions of vaccine science might allow the design of vaccines to progress to a less empirical stage, for example through availability of assay results associated with vaccine efficacy. We discuss six strategic gaps in knowledge that contribute to empiricism in the design of vaccines. Comparative evaluation, assay and model standardisation, greater sharing of information, collaboration and coordination between groups, and rigorous evaluation of existing datasets are steps that can be taken to enable reductions in empiricism over time.
Collapse
|
43
|
Roestenberg M, McCall M, Hopman J, Wiersma J, Luty AJF, van Gemert GJ, van de Vegte-Bolmer M, van Schaijk B, Teelen K, Arens T, Spaarman L, de Mast Q, Roeffen W, Snounou G, Rénia L, van der Ven A, Hermsen CC, Sauerwein R. Protection against a malaria challenge by sporozoite inoculation. N Engl J Med 2009; 361:468-77. [PMID: 19641203 DOI: 10.1056/nejmoa0805832] [Citation(s) in RCA: 461] [Impact Index Per Article: 30.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/19/2022]
Abstract
BACKGROUND An effective vaccine for malaria is urgently needed. Naturally acquired immunity to malaria develops slowly, and induction of protection in humans can be achieved artificially by the inoculation of radiation-attenuated sporozoites by means of more than 1000 infective mosquito bites. METHODS We exposed 15 healthy volunteers--with 10 assigned to a vaccine group and 5 assigned to a control group--to bites of mosquitoes once a month for 3 months while they were receiving a prophylactic regimen of chloroquine. The vaccine group was exposed to mosquitoes that were infected with Plasmodium falciparum, and the control group was exposed to mosquitoes that were not infected with the malaria parasite. One month after the discontinuation of chloroquine, protection was assessed by homologous challenge with five mosquitoes infected with P. falciparum. We assessed humoral and cellular responses before vaccination and before the challenge to investigate correlates of protection. RESULTS All 10 subjects in the vaccine group were protected against a malaria challenge with the infected mosquitoes. In contrast, patent parasitemia (i.e., parasites found in the blood on microscopical examination) developed in all five control subjects. Adverse events were mainly reported by vaccinees after the first immunization and by control subjects after the challenge; no serious adverse events occurred. In this model, we identified the induction of parasite-specific pluripotent effector memory T cells producing interferon-gamma, tumor necrosis factor alpha, and interleukin-2 as a promising immunologic marker of protection. CONCLUSIONS Protection against a homologous malaria challenge can be induced by the inoculation of intact sporozoites. (ClinicalTrials.gov number, NCT00442377.)
Collapse
Affiliation(s)
- Meta Roestenberg
- Department of Medical Microbiology, Radboud University Nijmegen Medical Center, Nijmegen, The Netherlands
| | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
44
|
Woodberry T, Pinzon-Charry A, Piera KA, Panpisutchai Y, Engwerda CR, Doolan DL, Salwati E, Kenangalem E, Tjitra E, Price RN, Good MF, Anstey NM. Human T cell recognition of the blood stage antigen Plasmodium hypoxanthine guanine xanthine phosphoribosyl transferase (HGXPRT) in acute malaria. Malar J 2009; 8:122. [PMID: 19500406 PMCID: PMC2700129 DOI: 10.1186/1475-2875-8-122] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2009] [Accepted: 06/07/2009] [Indexed: 11/23/2022] Open
Abstract
Background The Plasmodium purine salvage enzyme, hypoxanthine guanine xanthine phosphoribosyl transferase (HGXPRT) can protect mice against Plasmodium yoelii pRBC challenge in a T cell-dependent manner and has, therefore, been proposed as a novel vaccine candidate. It is not known whether natural exposure to Plasmodium falciparum stimulates HGXPRT T cell reactivity in humans. Methods PBMC and plasma collected from malaria-exposed Indonesians during infection and 7–28 days after anti-malarial therapy, were assessed for HGXPRT recognition using CFSE proliferation, IFNγ ELISPOT assay and ELISA. Results HGXPRT-specific T cell proliferation was found in 44% of patients during acute infection; in 80% of responders both CD4+ and CD8+ T cell subsets proliferated. Antigen-specific T cell proliferation was largely lost within 28 days of parasite clearance. HGXPRT-specific IFN-γ production was more frequent 28 days after treatment than during acute infection. HGXPRT-specific plasma IgG was undetectable even in individuals exposed to malaria for at least two years. Conclusion The prevalence of acute proliferative and convalescent IFNγ responses to HGXPRT demonstrates cellular immunogenicity in humans. Further studies to determine minimal HGXPRT epitopes, the specificity of responses for Plasmodia and associations with protection are required. Frequent and robust T cell proliferation, high sequence conservation among Plasmodium species and absent IgG responses distinguish HGXPRT from other malaria antigens.
Collapse
Affiliation(s)
- Tonia Woodberry
- International Health Division, Menzies School of Health Research, Charles Darwin University, Darwin, Australia.
| | | | | | | | | | | | | | | | | | | | | | | |
Collapse
|
45
|
|
46
|
Statins as potential antimalarial drugs: low relative potency and lack of synergy with conventional antimalarial drugs. Antimicrob Agents Chemother 2009; 53:2212-4. [PMID: 19258270 DOI: 10.1128/aac.01469-08] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The in vitro sensitivity of Plasmodium falciparum to atorvastatin and rosuvastatin was assessed using chloroquine-sensitive and chloroquine-resistant strains. Although atorvastatin was more potent, it had weak activity (mean 50% inhibitory concentration of > or = 17 microM) and an indifferent interaction with chloroquine and dihydroartemisinin. Bioassay of plasma from an atorvastatin-treated subject showed similar results.
Collapse
|
47
|
Pinzon-Charry A, Good MF. Malaria vaccines: the case for a whole-organism approach. Expert Opin Biol Ther 2008; 8:441-8. [DOI: 10.1517/14712598.8.4.441] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
|
48
|
Malaria treatment with atovaquone-proguanil in malaria-immune adults: implications for malaria intervention trials and for pre-exposure prophylaxis of malaria. Antimicrob Agents Chemother 2008; 52:1493-5. [PMID: 18268090 DOI: 10.1128/aac.01367-07] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022] Open
Abstract
Eighty adults in areas of Kenya where malaria is holoendemic received presumptive treatment with atovaquone-proguanil and were followed closely. The time to the first Plasmodium falciparum parasitemia was 32 days. This prolonged prophylaxis period has implications for study design when used in malaria intervention trials and cautiously suggests clinical investigation of potential preexposure prophylaxis of malaria.
Collapse
|
49
|
Shanks GD, Magill AJ, Freedman DO, Keystone JS, Bradley DJ, Steffen R. Drug-Free Holidays: Pre-Travel versus During Travel Malaria Chemoprophylaxis. Am J Trop Med Hyg 2007. [DOI: 10.4269/ajtmh.77.1.0770001] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022] Open
Affiliation(s)
- G. Dennis Shanks
- Army Malaria Institute, Brisbane, Queensland, Australia; Walter Reed Army Institute of Research, Silver Spring, Maryland; University of Alabama at Birmingham, Birmingham, Alabama; The Toronto Hospital, Toronto, Ontario, Canada; London School of Hygiene and Tropical Medicine, London, United Kingdom; World Health Organization Collaborating Centre for Travelers’ Health, University of Zurich, Zurich, Switzerland
| | - Alan J. Magill
- Army Malaria Institute, Brisbane, Queensland, Australia; Walter Reed Army Institute of Research, Silver Spring, Maryland; University of Alabama at Birmingham, Birmingham, Alabama; The Toronto Hospital, Toronto, Ontario, Canada; London School of Hygiene and Tropical Medicine, London, United Kingdom; World Health Organization Collaborating Centre for Travelers’ Health, University of Zurich, Zurich, Switzerland
| | - David O. Freedman
- Army Malaria Institute, Brisbane, Queensland, Australia; Walter Reed Army Institute of Research, Silver Spring, Maryland; University of Alabama at Birmingham, Birmingham, Alabama; The Toronto Hospital, Toronto, Ontario, Canada; London School of Hygiene and Tropical Medicine, London, United Kingdom; World Health Organization Collaborating Centre for Travelers’ Health, University of Zurich, Zurich, Switzerland
| | - Jay S. Keystone
- Army Malaria Institute, Brisbane, Queensland, Australia; Walter Reed Army Institute of Research, Silver Spring, Maryland; University of Alabama at Birmingham, Birmingham, Alabama; The Toronto Hospital, Toronto, Ontario, Canada; London School of Hygiene and Tropical Medicine, London, United Kingdom; World Health Organization Collaborating Centre for Travelers’ Health, University of Zurich, Zurich, Switzerland
| | - David J. Bradley
- Army Malaria Institute, Brisbane, Queensland, Australia; Walter Reed Army Institute of Research, Silver Spring, Maryland; University of Alabama at Birmingham, Birmingham, Alabama; The Toronto Hospital, Toronto, Ontario, Canada; London School of Hygiene and Tropical Medicine, London, United Kingdom; World Health Organization Collaborating Centre for Travelers’ Health, University of Zurich, Zurich, Switzerland
| | - Robert Steffen
- Army Malaria Institute, Brisbane, Queensland, Australia; Walter Reed Army Institute of Research, Silver Spring, Maryland; University of Alabama at Birmingham, Birmingham, Alabama; The Toronto Hospital, Toronto, Ontario, Canada; London School of Hygiene and Tropical Medicine, London, United Kingdom; World Health Organization Collaborating Centre for Travelers’ Health, University of Zurich, Zurich, Switzerland
| |
Collapse
|
50
|
Hitani A, Nakamura T, Ohtomo H, Nawa Y, Kimura M. Efficacy and safety of atovaquone-proguanil compared with mefloquine in the treatment of nonimmune patients with uncomplicated P. falciparum malaria in Japan. J Infect Chemother 2006; 12:277-82. [PMID: 17109092 DOI: 10.1007/s10156-006-0465-8] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/01/2006] [Accepted: 07/13/2006] [Indexed: 11/28/2022]
Abstract
Malaria treatment is becoming increasingly difficult due to the widespread drug resistance of Plasmodium falciparum. In Japan, only three antimalarials are approved for treatment: oral quinine, sulfadoxine-pyrimethamine, and mefloquine. Recently, however, the Research Group on Chemotherapy of Tropical Diseases introduced atovaquone-proguanil for treating drug-resistant P. falciparum malaria. This research group had also introduced mefloquine before it was licensed nationally. Using data obtained from the research group, we analyzed the efficacy and safety of atovaquone-proguanil, as compared with mefloquine, in nonimmune patients with uncomplicated P. falciparum malaria. Cures were attained in all (100%) of 20 atovaquone-proguanil-treated and 49 (98%) of 50 mefloquine-treated adults. The mean fever clearance time (FCT) and parasite clearance time (PCT) appeared to be longer in the atovaquone-proguanil group than in the mefloquine group, but the differences were not statistically significant. Three (15%) of the 20 atovaquone-proguanil-treated adults had adverse events (AEs), all of which were transient elevations of liver enzymes, while 19 (38%) of the 50 mefloquine-treated adults had AEs, including dizziness in 8 (16%) and nausea/vomiting in 7 (14%). All 3 children treated with atovaquone-proguanil were cured without developing AEs. Despite the limitations of this study in not being a formal clinical trial, atovaquone-proguanil seemed to be at least equal to, or even better than, mefloquine for the treatment of uncomplicated P. falciparum malaria in nonimmune patients, including children. Its marketing in Japan could be beneficial in offering an alternative therapeutic option. However, vigilance should be maintained on the possible occurrence of rare but severe AEs, and also of the possible spread of drug resistance.
Collapse
Affiliation(s)
- Akihiro Hitani
- Healthcheck, Health Care Center, Medical Institute Zenjinkai, Yokohama, Japan
| | | | | | | | | |
Collapse
|