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Mourão Dias Magalhães L, Silva Araújo Passos L, Toshio Fujiwara R, Lacerda Bueno L. Immunopathology and modulation induced by hookworms: From understanding to intervention. Parasite Immunol 2020; 43:e12798. [PMID: 33012113 DOI: 10.1111/pim.12798] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/12/2020] [Revised: 08/21/2020] [Accepted: 09/25/2020] [Indexed: 12/15/2022]
Abstract
Hookworm infection is considered the most prevalent human soil-transmitted helminth infection affecting approximately 500 million people and accounting for 3.2 million disability-adjusted life years lost annually. As with many other neglected tropical diseases, no international surveillance mechanisms that show accurate data on the prevalence of hookworm infection are in place, thus hindering strategies to control parasite transmission. In this review, we unravel the current knowledge in immunopathology and immunoregulation of hookworm infection and present discoveries in drug therapies based on the capability of hookworms to regulate inflammation to treat allergic, inflammatory and metabolic diseases. Additionally, we highlight potential vaccine development and treatments and propose avenues for further inquiry.
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Affiliation(s)
| | - Livia Silva Araújo Passos
- Department of Parasitology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Ricardo Toshio Fujiwara
- Department of Parasitology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
| | - Lilian Lacerda Bueno
- Department of Parasitology, Federal University of Minas Gerais, Belo Horizonte, Minas Gerais, Brazil
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Kamdem SD, Konhawa F, Kuemkon EM, Meyo Kamguia L, Tchanana GK, Nche F, Oumarou A, Hamza M, Ouratou Y, Tcheutchoua MN, Ghislain Essomba R, Ngogang MP, Kengne M, Netongo PM, Ondigui BE, Okomo Assoumou MC, Brombacher F, Nono JK. Negative Association of Interleukin-33 Plasma Levels and Schistosomiasis Infection in a Site of Polyparasitism in Rural Cameroon. Front Immunol 2019; 10:2827. [PMID: 31849991 PMCID: PMC6901687 DOI: 10.3389/fimmu.2019.02827] [Citation(s) in RCA: 9] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/14/2019] [Accepted: 11/18/2019] [Indexed: 12/20/2022] Open
Abstract
Background: This study aimed to investigate the association of plasma levels of IL-33, a mucosal alarmin known to elicit type-2 immunity, with infection and liver fibrosis profiles of school children from an endemic area for Schistosoma mansoni, malaria and hepatitis (B & C) in rural Cameroon. Methods: A cross-sectional study enrolling schoolchildren from 5 public schools was conducted. Single schistosomiasis, malaria and hepatitis infections or co-infections were assessed by kato katz, microscopy, and rapid diagnostic tests, respectively. Hepatic fibrosis was assessed by ultrasound according to WHO Niamey guidelines and plasma levels of Interleukin 33 were determined by ELISA. All statistics were performed using R studio software. Principal findings: We found a prevalence of 13.5% (37/275), 18.2% (50/275), and 8% (22/275), respectively for schistosomiasis, malaria and hepatitis (B or C) single infections. Only 7.6% (21/275) of co-infections were reported. Although Plasma IL-33 showed a minimal negative risk for schistosomiasis infection (AOR 0.99; 95% CI 0.97–1.01), S. mansoni infected participants had lower levels of plasma IL-33 (p = 0.003) which decreased significantly as eggs burdens increased (p = 0.01) with a negative Pearson coefficient of r = −0.22. Hepatic fibrosis occurred in 47.3% (130/275) of our study population independently from plasma levels of IL-33 (AOR 1.00; 95% CI 0.99–1.01). Conclusion/Significance: Our data failed to show an association between plasma IL-33 levels and liver disease but convincingly report on a negative association between plasma IL-33 levels and schistosomiasis infection and egg burden in school children from a polyparasitic schistosomiasis endemic area.
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Affiliation(s)
- Severin Donald Kamdem
- Division of Immunology, Health Science Faculty, University of Cape Town, Cape Town, South Africa.,Cape Town Component, International Centre for Genetic Engineering and Biotechnology, Cape Town, South Africa.,Immunology of Infectious Diseases Unit, South African Medical Research Centre, Cape Town, South Africa
| | - Francis Konhawa
- School of Health Sciences, Catholic University of Central Africa, Yaoundé, Cameroon
| | - Erve Martial Kuemkon
- School of Health Sciences, Catholic University of Central Africa, Yaoundé, Cameroon
| | - Leonel Meyo Kamguia
- School of Health Sciences, Catholic University of Central Africa, Yaoundé, Cameroon
| | - Gladys K Tchanana
- School of Health Sciences, Catholic University of Central Africa, Yaoundé, Cameroon.,CIAB EXACT Medical Laboratory, Yaoundé, Cameroon
| | - Frungwa Nche
- Faculty of Medicine and Biomedical Sciences, University of Yaoundé 1, Yaoundé, Cameroon
| | | | | | - Yasmine Ouratou
- Biotechnology Centre, University of Yaoundé 1, Yaoundé, Cameroon
| | | | - René Ghislain Essomba
- School of Health Sciences, Catholic University of Central Africa, Yaoundé, Cameroon.,National Public Health Laboratory, Ministry of Public Health, Yaoundé, Cameroon
| | | | - Michel Kengne
- School of Health Sciences, Catholic University of Central Africa, Yaoundé, Cameroon
| | - Palmer Masumbe Netongo
- Biotechnology Centre, University of Yaoundé 1, Yaoundé, Cameroon.,Department of Biochemistry, University of Yaoundé 1, Yaoundé, Cameroon
| | | | | | - Frank Brombacher
- Division of Immunology, Health Science Faculty, University of Cape Town, Cape Town, South Africa.,Cape Town Component, International Centre for Genetic Engineering and Biotechnology, Cape Town, South Africa.,Immunology of Infectious Diseases Unit, South African Medical Research Centre, Cape Town, South Africa.,Wellcome Centre for Infectious Diseases Research in Africa, Institute of Infectious Diseases and Molecular Medicine (IDM), University of Cape Town, Cape Town, South Africa
| | - Justin Komguep Nono
- Division of Immunology, Health Science Faculty, University of Cape Town, Cape Town, South Africa.,Cape Town Component, International Centre for Genetic Engineering and Biotechnology, Cape Town, South Africa.,Immunology of Infectious Diseases Unit, South African Medical Research Centre, Cape Town, South Africa.,The Medical Research Centre, Institute of Medical Research and Medicinal Plant Studies, Ministry of Scientific Research and Innovation, Yaoundé, Cameroon
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Abstract
A sample size formula for comparing two groups of count data is derived using the method of moments by matching the first and second moments of the distribution of the count data, and it does not need any further distributional assumption. Compared to sample size formulas derived using a likelihood-based approach or using simulations, the proposed sample size formula applies to count data following any distribution in addition to the negative binomial distribution. The proposed sample size formula can be used even when the study is analyzed with a likelihood-based approach. Because asymptotically, the method of moments is no more efficient than likelihood-based approaches, the proposed sample size formula can be viewed as an upper bound of the required sample size by likelihood-based approaches to start the study. Applications of the sample size formula are illustrated using an asthma study design.
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Affiliation(s)
- Lin Wang
- a Department of Biostatistics and Programming , Sanofi US Inc , Bridgewater , NJ , USA
| | - Chunpeng Fan
- a Department of Biostatistics and Programming , Sanofi US Inc , Bridgewater , NJ , USA
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Overgaard HJ, Olano VA, Jaramillo JF, Matiz MI, Sarmiento D, Stenström TA, Alexander N. A cross-sectional survey of Aedes aegypti immature abundance in urban and rural household containers in central Colombia. Parasit Vectors 2017; 10:356. [PMID: 28750651 PMCID: PMC5530958 DOI: 10.1186/s13071-017-2295-1] [Citation(s) in RCA: 37] [Impact Index Per Article: 5.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/01/2017] [Accepted: 07/17/2017] [Indexed: 11/15/2022] Open
Abstract
BACKGROUND Aedes aegypti, the major vector of dengue, breeds in domestic water containers. The development of immature mosquitoes in such containers is influenced by various environmental, ecological and socioeconomic factors. Urban and rural disparities in water storage practices and water source supply may affect mosquito immature abundance and, potentially, dengue risk. We evaluated the effect of water and container characteristics on A. aegypti immature abundance in urban and rural areas. Data were collected in the wet season of 2011 in central Colombia from 36 urban and 35 rural containers, which were either mosquito-positive or negative. Immature mosquitoes were identified to species. Data on water and container characteristics were collected from all containers. RESULTS A total of 1452 Aedes pupae and larvae were collected of which 81% were A. aegypti and 19% A. fluviatilis. Aedes aegypti immatures were found in both urban and rural sites. However, the mean number of A. aegypti pupae was five times higher in containers in the urban sites compared to those in the rural sites. One of the important factors associated with A. aegypti infestation was frequency of container washing. Monthly-washed or never-washed containers were both about four times more likely to be infested than those washed every week. There were no significant differences between urban and rural sites in frequency of washing containers. Aedes aegypti immature infestation was positively associated with total dissolved solids, but negatively associated with dissolved oxygen. Water temperature, total dissolved solids, ammonia, nitrate, and organic matter were significantly higher in urban than in rural containers, which might explain urban-rural differences in breeding of A. aegypti. However, many of these factors vary substantially between studies and in their degree of association with vector breeding, therefore they may not be reliable indices for vector control interventions. CONCLUSIONS Although containers in urban areas were more likely to be infested with A. aegypti, rural containers still provide suitable habitats for A. aegypti. Containers that are washed more frequent are less likely to produce A. aegypti. These results highlight the importance of container washing as an effective vector control tool in both urban and rural areas. In addition, alternative designs of the highly productive washbasins should continue to be explored. To control diseases such as dengue, Zika and chikungunya, effective vector breeding site control must be implemented in addition to other interventions.
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Affiliation(s)
- Hans J. Overgaard
- Faculty of Science and Technology, Norwegian University of Life Sciences, Ås, Norway
| | | | | | - María Inés Matiz
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogotá, Colombia
| | - Diana Sarmiento
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogotá, Colombia
| | - Thor Axel Stenström
- SARChI, Institute for Water and Waste Water Technology, Durban University of Technology, Durban, South Africa
| | - Neal Alexander
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London, UK
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Overgaard HJ, Alexander N, Matiz MI, Jaramillo JF, Olano VA, Vargas S, Sarmiento D, Lenhart A, Stenström TA. A Cluster-Randomized Controlled Trial to Reduce Diarrheal Disease and Dengue Entomological Risk Factors in Rural Primary Schools in Colombia. PLoS Negl Trop Dis 2016; 10:e0005106. [PMID: 27820821 PMCID: PMC5098800 DOI: 10.1371/journal.pntd.0005106] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2016] [Accepted: 10/12/2016] [Indexed: 11/24/2022] Open
Abstract
BACKGROUND As many neglected tropical diseases are co-endemic and have common risk factors, integrated control can efficiently reduce disease burden and relieve resource-strained public health budgets. Diarrheal diseases and dengue fever are major global health problems sharing common risk factors in water storage containers. Where provision of clean water is inadequate, water storage is crucial. Fecal contamination of stored water is a common source of diarrheal illness, but stored water also provides breeding sites for dengue vector mosquitoes. Integrating improved water management and educational strategies for both diseases in the school environment can potentially improve the health situation for students and the larger community. The objective of this trial was to investigate whether interventions targeting diarrhea and dengue risk factors would significantly reduce absence due to diarrheal disease and dengue entomological risk factors in schools. METHODOLOGY/PRINCIPAL FINDINGS A factorial cluster randomized controlled trial was carried out in 34 rural primary schools (1,301 pupils) in La Mesa and Anapoima municipalities, Cundinamarca, Colombia. Schools were randomized to one of four study arms: diarrhea interventions (DIA), dengue interventions (DEN), combined diarrhea and dengue interventions (DIADEN), and control (CON). Interventions had no apparent effect on pupil school absence due to diarrheal disease (p = 0.45) or on adult female Aedes aegypti density (p = 0.32) (primary outcomes). However, the dengue interventions reduced the Breteau Index on average by 78% (p = 0.029), with Breteau indices of 10.8 and 6.2 in the DEN and DIADEN arms, respectively compared to 37.5 and 46.9 in the DIA and CON arms, respectively. The diarrhea interventions improved water quality as assessed by the amount of Escherichia coli colony forming units (CFU); the ratio of Williams mean E. coli CFU being 0.22, or 78% reduction (p = 0.008). CONCLUSIONS/SIGNIFICANCE Integrated control of dengue and diarrhea has never been conducted before. This trial presents an example for application of control strategies that may affect both diseases and the first study to apply such an approach in school settings. The interventions were well received and highly appreciated by students and teachers. An apparent absence of effect in primary outcome indicators could be the result of pupils being exposed to risk factors outside the school area and mosquitoes flying in from nearby uncontrolled breeding sites. Integrated interventions targeting these diseases in a school context remain promising because of the reduced mosquito breeding and improved water quality, as well as educational benefits. However, to improve outcomes in future integrated approaches, simultaneous interventions in communities, in addition to schools, should be considered; using appropriate combinations of site-specific, effective, acceptable, and affordable interventions. TRIAL REGISTRATION ClinicalTrials.gov no. ISRCTN40195031.
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Affiliation(s)
- Hans J. Overgaard
- Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Norway
- Institut de Recherche pour le Développement, Maladies Infectieuses et Vecteurs, Ecologie, Génétique, Evolution et Contrôle, Montpellier, France
- Department of Entomology, Faculty of Agriculture, Kasetsart University, Bangkok, Thailand
| | - Neal Alexander
- MRC Tropical Epidemiology Group, London School of Hygiene and Tropical Medicine, London
| | - Maria Ines Matiz
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogota, Colombia
| | | | | | - Sandra Vargas
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogota, Colombia
| | - Diana Sarmiento
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogota, Colombia
| | - Audrey Lenhart
- Liverpool School of Tropical Medicine, Liverpool, United Kingdom
- U.S. Centers for Disease Control and Prevention, Atlanta, United States of America
| | - Thor Axel Stenström
- SARChI Chair, Institute for Water and Waste Water Technology, Durban University of Technology, Durban, South Africa
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Sample size calculations for skewed distributions. BMC Med Res Methodol 2015; 15:28. [PMID: 25886883 PMCID: PMC4423589 DOI: 10.1186/s12874-015-0023-0] [Citation(s) in RCA: 22] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2014] [Accepted: 03/24/2015] [Indexed: 11/10/2022] Open
Abstract
Background Sample size calculations should correspond to the intended method of analysis. Nevertheless, for non-normal distributions, they are often done on the basis of normal approximations, even when the data are to be analysed using generalized linear models (GLMs). Methods For the case of comparison of two means, we use GLM theory to derive sample size formulae, with particular cases being the negative binomial, Poisson, binomial, and gamma families. By simulation we estimate the performance of normal approximations, which, via the identity link, are special cases of our approach, and for common link functions such as the log. The negative binomial and gamma scenarios are motivated by examples in hookworm vaccine trials and insecticide-treated materials, respectively. Results Calculations on the link function (log) scale work well for the negative binomial and gamma scenarios examined and are often superior to the normal approximations. However, they have little advantage for the Poisson and binomial distributions. Conclusions The proposed method is suitable for sample size calculations for comparisons of means of highly skewed outcome variables. Electronic supplementary material The online version of this article (doi:10.1186/s12874-015-0023-0) contains supplementary material, which is available to authorized users.
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7
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Zhu H, Lakkis H. Authors' reply to comments on ‘Sample size calculation for comparing two negative binomial rates’. Stat Med 2014; 33:2880. [DOI: 10.1002/sim.6186] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/28/2014] [Accepted: 04/01/2014] [Indexed: 11/10/2022]
Affiliation(s)
- Haiyuan Zhu
- Forest Laboratories, Inc.; Jersey City NJ U.S.A
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8
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Zhu H, Lakkis H. Comments on ‘Sample size calculation for comparing two negative binomial rates’. Stat Med 2014; 33:1979. [DOI: 10.1002/sim.6119] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/21/2014] [Accepted: 02/03/2014] [Indexed: 11/06/2022]
Affiliation(s)
- H. Zhu
- Neal Alexander; MRC Tropical Epidemiology Group; Department of Infectious Disease Epidemiology; London School of Hygiene & Tropical Medicine; Keppel Street London WC1E 7HT UK
| | - H. Lakkis
- Neal Alexander; MRC Tropical Epidemiology Group; Department of Infectious Disease Epidemiology; London School of Hygiene & Tropical Medicine; Keppel Street London WC1E 7HT UK
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9
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Hotez PJ, Bethony JM. Parasitic disease vaccines. Vaccines (Basel) 2013. [DOI: 10.1016/b978-1-4557-0090-5.00059-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/26/2022] Open
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10
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Overgaard HJ, Alexander N, Mátiz MI, Jaramillo JF, Olano VA, Vargas S, Sarmiento D, Lenhart A, Seidu R, Stenström TA. Diarrhea and dengue control in rural primary schools in Colombia: study protocol for a randomized controlled trial. Trials 2012; 13:182. [PMID: 23034084 PMCID: PMC3582494 DOI: 10.1186/1745-6215-13-182] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/14/2012] [Accepted: 09/24/2012] [Indexed: 11/26/2022] Open
Abstract
BACKGROUND Diarrheal diseases and dengue fever are major global health problems. Where provision of clean water is inadequate, water storage is crucial. Fecal contamination of stored water is a common source of diarrheal illness, but stored water also provides breeding sites for dengue vector mosquitoes. Poor household water management and sanitation are therefore potential determinants of both diseases. Little is known of the role of stored water for the combined risk of diarrhea and dengue, yet a joint role would be important for developing integrated control and management efforts. Even less is known of the effect of integrating control of these diseases in school settings. The objective of this trial was to investigate whether interventions against diarrhea and dengue will significantly reduce diarrheal disease and dengue entomological risk factors in rural primary schools. METHODS/DESIGN This is a 2×2 factorial cluster randomized controlled trial. Eligible schools were rural primary schools in La Mesa and Anapoima municipalities, Cundinamarca, Colombia. Eligible pupils were school children in grades 0 to 5. Schools were randomized to one of four study arms: diarrhea interventions (DIA); dengue interventions (DEN); combined diarrhea and dengue interventions (DIADEN); and control (C). Schools were allocated publicly in each municipality (strata) at the start of the trial, obviating the need for allocation concealment. The primary outcome for diarrhea is incidence rate of diarrhea in school children and for dengue it is density of adult female Aedes aegypti per school. Approximately 800 pupils from 34 schools were enrolled in the trial with eight schools in the DIA arm, nine in the DEN, eight in the DIADEN, and nine in the control arms. The trial status as of June 2012 was: completed baseline data collections; enrollment, randomization, and allocation of schools. The trial was funded by the Research Council of Norway and the Lazos de Calandaima Foundation. DISCUSSION This is the first trial investigating the effect of a set of integrated interventions to control both dengue and diarrhea. This is also the first trial to study the combination of diarrhea-dengue disease control in school settings. TRIAL REGISTRATION Current Controlled Trials ISRCTN40195031.
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Affiliation(s)
- Hans J Overgaard
- Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Neal Alexander
- London School of Hygiene and Tropical Medicine, London, UK
| | - Maria Ines Mátiz
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogotá, Colombia
| | | | | | - Sandra Vargas
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogotá, Colombia
| | - Diana Sarmiento
- Instituto de Salud y Ambiente, Universidad El Bosque, Bogotá, Colombia
| | | | - Razak Seidu
- Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway
| | - Thor Axel Stenström
- Department of Mathematical Sciences and Technology, Norwegian University of Life Sciences, Ås, Norway
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Alexander N, Cundill B, Sabatelli L, Bethony JM, Diemert D, Hotez P, Smith PG, Rodrigues LC, Brooker S. Selection and quantification of infection endpoints for trials of vaccines against intestinal helminths. Vaccine 2011; 29:3686-94. [PMID: 21435404 PMCID: PMC3093614 DOI: 10.1016/j.vaccine.2011.03.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/02/2010] [Revised: 02/21/2011] [Accepted: 03/02/2011] [Indexed: 12/22/2022]
Abstract
Vaccines against human helminths are being developed but the choice of optimal parasitological endpoints and effect measures to assess their efficacy has received little attention. Assuming negative binomial distributions for the parasite counts, we rank the statistical power of three measures of efficacy: ratio of mean parasite intensity at the end of the trial, the odds ratio of infection at the end of the trial, and the rate ratio of incidence of infection during the trial. We also use a modelling approach to estimate the likely impact of trial interventions on the force of infection, and hence statistical power. We conclude that (1) final mean parasite intensity is a suitable endpoint for later phase vaccine trials, and (2) mass effects of trial interventions are unlikely to appreciably reduce the force of infection in the community - and hence statistical power - unless there is a combination of high vaccine efficacy and a large proportion of the population enrolled.
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Affiliation(s)
- Neal Alexander
- London School of Hygiene and Tropical Medicine, London, UK.
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12
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Sabatelli L, Ghani AC, Rodrigues LC, Hotez PJ, Brooker S. Modelling heterogeneity and the impact of chemotherapy and vaccination against human hookworm. J R Soc Interface 2008; 5:1329-41. [PMID: 18331978 DOI: 10.1098/rsif.2007.1255] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023] Open
Abstract
There is a growing emphasis on the development of vaccines against helminths (worms), and mathematical models provide a useful tool to assess the impact of new vaccines under a range of scenarios. The present study describes a stochastic individual-based model to assess the relative impact of chemotherapy and vaccination against human hookworm infection and investigates the implications of potential correlations between risk of infection and vaccine efficacy. Vaccination is simulated as a reduction in susceptibility to infection and the model includes population heterogeneities and dynamical waning of protection. To help identify appropriate measures of vaccine impact, we present a novel framework to quantify the vaccine impact on the infection-associated morbidity and introduce a measure of symmetry to study the correspondence between reduction in intensity and reduction in morbidity. Our modelling shows that, in high-transmission settings, the greatest impact of vaccination will be attained when vaccine efficacy is the greatest among individuals harbouring the heaviest worm burdens, and that the decline of morbidity primarily depends on the level of protection attained in the most at risk 8-12% of the population. We also demonstrate that if risk of infection and vaccine protection are correlated, there is not always a direct correspondence between the reduction in worm burden and in morbidity, with the precise relationship varying according to transmission setting.
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Affiliation(s)
- L Sabatelli
- London School of Hygiene and Tropical Medicine, Keppel Street, London, UK.
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Abstract
Hookworm infection caused by the soil-transmitted nematodes Necator americanus and Ancylostoma duodenale is one of the most common parasitic infections worldwide. Although not directly responsible for substantial mortality, it causes significant morbidity in the form of chronic anemia and protein malnutrition. Current global control efforts based on periodic mass anthelmintic administration are unsustainable, and new control strategies must be developed. This review describes progress in the development of vaccines against hookworm infection, including the preclinical and initial clinical testing of the N. americanus Ancylostoma Secreted Protein-2 Hookworm Vaccine. Plans call for eventual development of a vaccine that will combine at least 2 hookworm antigens--one targeting the larval stage of the life cycle and another targeting the adult worm living in the gastrointestinal tract.
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Affiliation(s)
- David J Diemert
- Sabin Vaccine Institute, George Washington University, Washington, DC 20037, USA
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14
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Fine PE, Mulholland K. Community immunity. Vaccines (Basel) 2008. [DOI: 10.1016/b978-1-4160-3611-1.50075-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/24/2022] Open
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Hotez PJ, Bethony JM. Parasitic disease vaccines. Vaccines (Basel) 2008. [DOI: 10.1016/b978-1-4160-3611-1.50059-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022] Open
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Geiger SM, Caldas IR, Mc Glone BE, Campi-Azevedo AC, De Oliveira LM, Brooker S, Diemert D, Corrêa-Oliveira R, Bethony JM. Stage-specific immune responses in human Necator americanus infection. Parasite Immunol 2007; 29:347-58. [PMID: 17576364 PMCID: PMC1976388 DOI: 10.1111/j.1365-3024.2007.00950.x] [Citation(s) in RCA: 56] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022]
Abstract
We describe how hookworms interact with their human hosts by comparing lymphocyte phenotyping, proliferative responses, and cytokine and chemokine secretion patterns in adults who are either mono-infected with Necator americanus or egg-negative controls resident in an area of high transmission in Brazil. Cellular immune responses against crude hookworm antigen extracts from different developmental stages were evaluated simultaneously. Principal component analysis (PCA) was used to reduce the standardized immune responses. Random effects multivariate regression was then used to investigate whether principal components (PC) differ between the two groups once potential confounders and effect modifiers have been accounted for. Although hookworm patients had reduced percentages of T and B cells, they had higher levels of activated CD4+ T and CD19+ B cells. This state of ‘immune activation’ coincided with lower proliferative responses, especially to third-stage larval antigen. Cytokine levels in mono-infected adults were also lower and characterized by a mixed Th1/Th2-type profile. Excretory/secretory antigen from adult worms was a potent modulator of the immune response, resulting in diminished TNF-α and IL-10 secretion in peripheral blood mononuclear cells (PBMC) from hookworm infected patients. We propose that the longevity of hookworms in their human hosts results from a stage-specific, down-modulation of the immune response.
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Affiliation(s)
- S M Geiger
- Fundação Oswaldo Cruz, Centro de Pesquisas René Rachou, Belo Horizonte-MG, Brazil
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Bethony JM, Loukas A, Hotez PJ, Knox DP. Vaccines against blood-feeding nematodes of humans and livestock. Parasitology 2007; 133 Suppl:S63-79. [PMID: 17274849 DOI: 10.1017/s0031182006001818] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
This paper summarises the progress towards vaccine development against the major blood-feeding nematodes of man and livestock, the hookworms and Haemonchus contortus, respectively. The impact of the diseases and the drivers for vaccine development are summarized as well as the anticipated impact of the host immune response on vaccine design. The performance requirements are discussed and progress towards these objectives using defined larval and adult antigens, many of these being shared between species. Specific examples include the Ancylostoma secreted proteins and homologues in Haemonchus as well as proteases used for digestion of the blood meal. This discussion shows that many of the major vaccine candidates are shared between these blood-feeding species, not only those from the blood-feeding stages but also those expressed by infective L3s in the early stages of infection. Challenges for the future include: exploiting the expanding genome information for antigen discovery, use of different recombinant protein expression systems, formulation with new adjuvants, and novel methods of field testing vaccine efficacy.
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Affiliation(s)
- J M Bethony
- Centro de Pesquisas René Rachou/CPqRR, A FIOCRUZ em Minas Gerais. Rene Rachou Research Center/CPqRR, The Oswaldo Cruz Foundation, Minas Gerais, Brazil.
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Fujiwara RT, Zhan B, Mendez S, Loukas A, Bueno LL, Wang Y, Plieskatt J, Oksov Y, Lustigman S, Bottazzi ME, Hotez P, Bethony JM. Reduction of worm fecundity and canine host blood loss mediates protection against hookworm infection elicited by vaccination with recombinant Ac-16. CLINICAL AND VACCINE IMMUNOLOGY : CVI 2007; 14:281-7. [PMID: 17267592 PMCID: PMC1828853 DOI: 10.1128/cvi.00404-06] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
Abstract
Hookworm infection is one of most important parasitic infection of humans, occurring in 740 million people. Here we report the protective vaccination of dogs with Ac-16, an immunodominant surface antigen from the hookworm Ancylostoma caninum. We show that immunization with Ac-16 formulated with AS03 elicited specific humoral and cellular immune responses and provided partial protection against hookworm infection and morbidity as evidenced by a significant reduction of hookworm egg counts (64% reduction; P = 0.0078) and worm-induced blood loss (P < 0.05). Moreover, specific anti-Ac-16 antibodies recognized the native protein on the surface of third-stage larvae and blocked their migration through tissue in vitro. Our data support the use of Ac-16 as a potential candidate for vaccination against hookworm infection.
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Affiliation(s)
- Ricardo T Fujiwara
- Department of Microbiology, Immunology and Tropical Medicine, The George Washington University, Ross Hall Room 727, 2300 Eye St. NW, Washington, DC 20037, USA
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Alexander N, Bethony J, Corrêa-Oliveira R, Rodrigues LC, Hotez P, Brooker S. Repeatability of paired counts. Stat Med 2007; 26:3566-77. [PMID: 17091531 DOI: 10.1002/sim.2724] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/05/2022]
Abstract
The Bland and Altman technique is widely used to assess the variation between replicates of a method of clinical measurement. It yields the repeatability, i.e. the value within which 95 per cent of repeat measurements lie. The valid use of the technique requires that the variance is constant over the data range. This is not usually the case for counts of items such as CD4 cells or parasites, nor is the log transformation applicable to zero counts. We investigate the properties of generalized differences based on Box-Cox transformations. For an example, in a data set of hookworm eggs counted by the Kato-Katz method, the square root transformation is found to stabilize the variance. We show how to back-transform the repeatability on the square root scale to the repeatability of the counts themselves, as an increasing function of the square mean root egg count, i.e. the square of the average of square roots. As well as being more easily interpretable, the back-transformed results highlight the dependence of the repeatability on the sample volume used.
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Affiliation(s)
- Neal Alexander
- London School of Hygiene and Tropical Medicine, London, UK.
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Loukas A, Bethony J, Brooker S, Hotez P. Hookworm vaccines: past, present, and future. THE LANCET. INFECTIOUS DISEASES 2006; 6:733-41. [PMID: 17067922 DOI: 10.1016/s1473-3099(06)70630-2] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
Hookworms are gastrointestinal nematodes that infect almost 1 billion people in developing countries. The main clinical symptom of human hookworm infections is iron-deficiency anaemia, a direct consequence of the intestinal blood loss resulting from the parasite's feeding behaviour. Although treatment is available and currently used for the periodic removal of adult hookworms from patients, this approach has not effectively controlled hookworm in areas of rural poverty. Furthermore, treated individuals remain susceptible to reinfection following exposure to third-stage infective hookworm larvae in the soil as early as 4-12 months after drug treatment. Therefore, a prophylactic vaccine against hookworm infection would provide an attractive additional tool for the public-health control of this disease. The feasibility of developing a vaccine is based on the previous success of an attenuated larval vaccine against canine hookworm. Several laboratory and field studies have explored the development of a human anti-hookworm vaccine, describing potential protective mechanisms and identifying candidate antigens, one of which is now in clinical trials. The current roadmap that investigators have conceived has been influenced by vaccine development for blood-feeding nematodes of livestock and companion animals; however, recombinant vaccines have yet to be developed for nematodes that parasitise animals or human beings. The roadmap also addresses the obstacles facing development of a vaccine for developing countries, where there is no commercial market.
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Affiliation(s)
- Alex Loukas
- Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, Brisbane, Australia.
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Albonico M, Montresor A, Crompton DWT, Savioli L. Intervention for the control of soil-transmitted helminthiasis in the community. ADVANCES IN PARASITOLOGY 2006; 61:311-48. [PMID: 16735168 PMCID: PMC5633078 DOI: 10.1016/s0065-308x(05)61008-1] [Citation(s) in RCA: 38] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/24/2022]
Abstract
The global strategy for the control of soil-transmitted helminthiasis, based on regular anthelminthic treatment, health education and improved sanitation standards, is reviewed. The reasons for the development of a control strategy based on population intervention rather than on individual treatment are explained. The evidence and experience from control programmes that created the basis for (i) the definition of the intervention package, (ii) the identification of the groups at risk, (iii) the standardization of the community diagnosis and (iv) the selection of the appropriate intervention for each category in the community are discussed. How to best deliver the appropriate intervention, the impact of the control measures on morbidity and on indicators such as school attendance, cognitive development and productivity are presented. The factors influencing the cost-benefits of helminth control are also considered. The recent progress on the control of soil-transmitted helminth infections is illustrated. Research needs are analysed in relation to the most recent perceptions from private-public partnerships involved in helminth control. The way forward for the control of soil-transmitted helminth infections is described as a multi-disease approach that goes beyond deworming and fosters a pro-poor strategy that supports the aims of the Millennium Development Goals.
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Fujiwara RT, Geiger SM, Bethony J, Mendez S. Comparative immunology of human and animal models of hookworm infection. Parasite Immunol 2006; 28:285-93. [PMID: 16842265 DOI: 10.1111/j.1365-3024.2006.00821.x] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
Abstract
Hookworm infection is a major cause of disease burden for animals and humans. Over the past years, the use of animal models in hookworm infections has been driven by the search of new anthelminthic therapies and, especially, vaccine development. These studies also contributed to the advance of knowledge on immunity to hookworms, offering new insights to understand the nature of this parasitic infection. In this article, we will summarize the essential features of the immune response in the two major animal models of hookworm infections (dog and hamster) and then consider its implication for the human immune response.
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Affiliation(s)
- R T Fujiwara
- Department of Microbiology, Immunology and Tropical Medicine, The George Washington University, Washington, DC, USA.
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Hotez PJ, Bethony J, Bottazzi ME, Brooker S, Diemert D, Loukas A. New technologies for the control of human hookworm infection. Trends Parasitol 2006; 22:327-31. [PMID: 16709466 DOI: 10.1016/j.pt.2006.05.004] [Citation(s) in RCA: 66] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2006] [Revised: 03/28/2006] [Accepted: 05/05/2006] [Indexed: 11/21/2022]
Abstract
Since the 1990s, the major approach to hookworm control has been morbidity reduction in school-aged children by periodic deworming with benzimidazoles. Now, efforts are underway to determine the feasibility of integrating deworming with control programs that target other neglected tropical diseases. However, the sustainability of benzimidazole deworming for hookworm is of concern because of the variable efficacy of mebendazole, high rates of post-treatment reinfection and possible development of drug resistance. This requires parallel efforts to develop new and complementary hookworm control tools, such as new anthelmintic drugs (e.g. tribendimidine) and a recombinant hookworm vaccine. It is hoped that, ultimately, anthelmintic vaccination will be linked to deworming as part of an expanded control package.
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Affiliation(s)
- Peter J Hotez
- Department of Microbiology, Immunology, and Tropical Medicine, The George Washington University, 2300 I Street, NW Washington, DC 20037, USA.
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Hotez PJ, Molyneux DH, Fenwick A, Ottesen E, Ehrlich Sachs S, Sachs JD. Incorporating a rapid-impact package for neglected tropical diseases with programs for HIV/AIDS, tuberculosis, and malaria. PLoS Med 2006; 3:e102. [PMID: 16435908 PMCID: PMC1351920 DOI: 10.1371/journal.pmed.0030102] [Citation(s) in RCA: 525] [Impact Index Per Article: 29.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/04/2022] Open
Abstract
Hotez et al. argue that achieving success in the global fight against HIV/AIDS, tuberculosis, and malaria may well require a concurrent attack on the neglected tropical diseases.
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Affiliation(s)
- Peter J Hotez
- Department of Microbiology, Immunology, and Tropical Medicine, The George Washington University, Washington, District of Columbia, USA.
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Loukas A, Bethony JM, Mendez S, Fujiwara RT, Goud GN, Ranjit N, Zhan B, Jones K, Bottazzi ME, Hotez PJ. Vaccination with recombinant aspartic hemoglobinase reduces parasite load and blood loss after hookworm infection in dogs. PLoS Med 2005; 2:e295. [PMID: 16231975 PMCID: PMC1240050 DOI: 10.1371/journal.pmed.0020295] [Citation(s) in RCA: 103] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 04/08/2005] [Accepted: 07/13/2005] [Indexed: 11/18/2022] Open
Abstract
BACKGROUND Hookworms infect 730 million people in developing countries where they are a leading cause of intestinal blood loss and iron-deficiency anemia. At the site of attachment to the host, adult hookworms ingest blood and lyse the erythrocytes to release hemoglobin. The parasites subsequently digest hemoglobin in their intestines using a cascade of proteolysis that begins with the Ancylostoma caninum aspartic protease 1, APR-1. METHODS AND FINDINGS We show that vaccination of dogs with recombinant Ac-APR-1 induced antibody and cellular responses and resulted in significantly reduced hookworm burdens (p = 0.056) and fecal egg counts (p = 0.018) in vaccinated dogs compared to control dogs after challenge with infective larvae of A. caninum. Most importantly, vaccinated dogs were protected against blood loss (p = 0.049) and most did not develop anemia, the major pathologic sequela of hookworm disease. IgG from vaccinated animals decreased the catalytic activity of the recombinant enzyme in vitro and the antibody bound in situ to the intestines of worms recovered from vaccinated dogs, implying that the vaccine interferes with the parasite's ability to digest blood. CONCLUSION To the best of our knowledge, this is the first report of a recombinant vaccine from a hematophagous parasite that significantly reduces both parasite load and blood loss, and it supports the development of APR-1 as a human hookworm vaccine.
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Affiliation(s)
- Alex Loukas
- 1Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
- *To whom correspondence should be addressed. E-mail: (AL); E-mail: (PJH)
| | - Jeffrey M Bethony
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
| | - Susana Mendez
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
| | - Ricardo T Fujiwara
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
| | - Gaddam Narsa Goud
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
| | - Najju Ranjit
- 1Division of Infectious Diseases and Immunology, Queensland Institute of Medical Research, Brisbane, Queensland, Australia
| | - Bin Zhan
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
| | - Karen Jones
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
| | - Maria Elena Bottazzi
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
| | - Peter J Hotez
- 2Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Washington, District of Columbia, United States of America
- *To whom correspondence should be addressed. E-mail: (AL); E-mail: (PJH)
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Goud GN, Bottazzi ME, Zhan B, Mendez S, Deumic V, Plieskatt J, Liu S, Wang Y, Bueno L, Fujiwara R, Samuel A, Ahn SY, Solanki M, Asojo OA, Wang J, Bethony JM, Loukas A, Roy M, Hotez PJ. Expression of the Necator americanus hookworm larval antigen Na-ASP-2 in Pichia pastoris and purification of the recombinant protein for use in human clinical trials. Vaccine 2005; 23:4754-64. [PMID: 16054275 DOI: 10.1016/j.vaccine.2005.04.040] [Citation(s) in RCA: 67] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2005] [Revised: 04/26/2005] [Accepted: 04/29/2005] [Indexed: 10/25/2022]
Abstract
The ASP-2 protein secreted by infective larvae of the human hookworm, Necator americanus, is under development as a recombinant vaccine. Recombinant Na-ASP-2 was expressed in Pichia pastoris, and the purified protein was characterized. At the 60 L scale, the 21.3 kDa recombinant protein was produced at a yield of 0.4 g/L. When formulated with Alhydrogel and injected into rats to determine immunological potency, three 50 microg doses of the formulated recombinant protein elicited geometric mean antibody titers up to 1:234,881. Rat anti-Na-ASP-2 antibody recognized larval-derived ASP-2 and also inhibited larval migration through skin in vitro. The processes developed and tested for the high yield production of recombinant Na-ASP-2 provide a foundation for clinical vaccine development.
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Affiliation(s)
- Gaddam Narsa Goud
- Department of Microbiology and Tropical Medicine, The George Washington University Medical Center, Ross Hall 736, 2300 Eye Street NW, Washington, DC 20037, USA.
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Bethony J, Loukas A, Smout M, Brooker S, Mendez S, Plieskatt J, Goud G, Bottazzi ME, Zhan B, Wang Y, Williamson A, Lustigman S, Correa-Oliveira R, Xiao S, Hotez PJ. Antibodies against a secreted protein from hookworm larvae reduce the intensity of hookworm infection in humans and vaccinated laboratory animals. FASEB J 2005; 19:1743-5. [PMID: 16037096 DOI: 10.1096/fj.05-3936fje] [Citation(s) in RCA: 140] [Impact Index Per Article: 7.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/11/2022]
Abstract
The development of a vaccine would provide an important new tool for the control of human hookworm infection. On the basis of successful vaccination of laboratory animals with living irradiated, third-stage hookworm larvae (L3), we examined the antibody responses of individuals from hookworm endemic areas of Brazil and China against the most abundant L3 secreted antigens, the ancylostoma secreted proteins, ASP-1 and ASP-2. Logistic regression was used to investigate the effects of antibody isotype responses to ASPs on the risk of an individual harboring heavy hookworm infection. A significant protective association was observed between increasing anti-ASP-2 IgE levels and the risk of heavy hookworm infection. To confirm that ASP-2 is a protective antigen, laboratory dogs were immunized with recombinant ASP-2 formulated with the GlaxoSmithKline Adjuvant, AS03. Sera obtained from the immunized dogs exhibited high geometric mean antibody titers, immunoprecipitated native ASP-2 from L3 extracts and localized the site of ASP-2 expression to the glandular esophagus and body channels exiting to the cuticle. The sera also exhibited an increased ability to inhibit migration of L3 through tissue in vitro relative to sera from AS03-injected controls. Upon L3 challenge, the ASP-2 vaccinated dogs exhibited significant reductions in fecal egg counts and intestinal hookworm burden. These findings provide strong support for the development of an effective recombinant vaccine against hookworm infection in humans.
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Affiliation(s)
- Jeffrey Bethony
- Department of Microbiology and Tropical Medicine, The George Washington University, Washington, DC 20037, USA.
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