Quantitative DigitoGraphy: a Comprehensive Real-Time Remote Monitoring System for Parkinson's Disease

People with Parkinson's disease (PWP) face critical challenges, including lack of access to neurological care, inadequate measurement and communication of motor symptoms, and suboptimal medication management and compliance. We have developed QDG-Care: a comprehensive connected care platform for Parkinson's disease (PD) that delivers validated, quantitative metrics of all motor signs in PD in real time, monitors the effects of adjusting therapy and medication adherence and is accessible in the electronic health record. In this article, we describe the design and engineering of all components of QDG-Care, including the development and utility of the QDG Mobility and Tremor Severity Scores. We present the preliminary results and insights from the first at-home trial using QDG-Care. QDG technology has enormous potential to improve access to, equity of, and quality of care for PWP, and improve compliance with complex time-critical medication regimens. It will enable rapid "Go-NoGo" decisions for new therapeutics by providing high-resolution data that require fewer participants at lower cost and allow more diverse recruitment.

Differential Effects of Pathological Beta Burst Dynamics Between Parkinson's Disease Phenotypes Across Different Movements

Background: Resting state beta band (13-30 Hz) oscillations represent pathological neural activity in Parkinson's disease (PD). It is unknown how the peak frequency or dynamics of beta oscillations may change among fine, limb, and axial movements and different disease phenotypes. This will be critical for the development of personalized closed loop deep brain stimulation (DBS) algorithms during different activity states. Methods: Subthalamic (STN) and local field potentials (LFPs) were recorded from a sensing neurostimulator (Activa® PC + S, Medtronic PLC.) in fourteen PD participants (six tremor-dominant and eight akinetic-rigid) off medication/off STN DBS during 30 s of repetitive alternating finger tapping, wrist-flexion extension, stepping in place, and free walking. Beta power peaks and beta burst dynamics were identified by custom algorithms and were compared among movement tasks and between tremor-dominant and akinetic-rigid groups. Results: Beta power peaks were evident during fine, limb, and axial movements in 98% of movement trials; the peak frequencies were similar during each type of movement. Burst power and duration were significantly larger in the high beta band, but not in the low beta band, in the akinetic-rigid group compared to the tremor-dominant group. Conclusion: The conservation of beta peak frequency during different activity states supports the feasibility of patient-specific closed loop DBS algorithms driven by the dynamics of the same beta band during different activities. Akinetic-rigid participants had greater power and longer burst durations in the high beta band than tremor-dominant participants during movement, which may relate to the difference in underlying pathophysiology between phenotypes.

Perspective: Evolution of Control Variables and Policies for Closed-Loop Deep Brain Stimulation for Parkinson's Disease Using Bidirectional Deep-Brain-Computer Interfaces

A deep brain stimulation system capable of closed-loop neuromodulation is a type of bidirectional deep brain-computer interface (dBCI), in which neural signals are recorded, decoded, and then used as the input commands for neuromodulation at the same site in the brain. The challenge in assuring successful implementation of bidirectional dBCIs in Parkinson's disease (PD) is to discover and decode stable, robust and reliable neural inputs that can be tracked during stimulation, and to optimize neurostimulation patterns and parameters (control policies) for motor behaviors at the brain interface, which are customized to the individual. In this perspective, we will outline the work done in our lab regarding the evolution of the discovery of neural and behavioral control variables relevant to PD, the development of a novel personalized dual-threshold control policy relevant to the individual's therapeutic window and the application of these to investigations of closed-loop STN DBS driven by neural or kinematic inputs, using the first generation of bidirectional dBCIs.

Feasibility of direct venous inoculation of the radiation-attenuated Plasmodium falciparum whole sporozoite vaccine in children and infants in Siaya, western Kenya

PfSPZ Vaccine, composed of radiation-attenuated, aseptic, purified, cryopreserved Plasmodium falciparum sporozoites, is administered by direct venous inoculation (DVI) for maximal efficacy against malaria. A critical issue for advancing vaccines that are administered intravenously is the ability to efficiently administer them across multiple age groups. As part of a pediatric safety, immunogenicity, and efficacy trial in western Kenya, we evaluated the feasibility and tolerability of DVI, including ease of venous access, injection time, and crying during the procedure across age groups. Part 1 was an age de-escalation, dose escalation trial in children aged 13 months-5 years and infants aged 5-12 months; part 2 was a vaccine efficacy trial including only infants, using the most skilled injectors from part 1. Injectors could use a vein viewer, if needed. A total of 1222 injections (target 0.5 mL) were initiated by DVI in 511 participants (36 were 5-9-year-olds, 65 were 13-59-month-olds, and 410 infants). The complete volume was injected in 1185/1222 (97.0%) vaccinations, 1083/1185 (91.4%) achieved with the first DVI. 474/511 (92.8%) participants received only complete injections, 27/511 (5.3%) received at least one partial injection (<0.5 mL), and in 10/511 (2.0%) venous access was not obtained. The rate of complete injections by single DVI for infants improved from 77.1% in part 1 to 92.8% in part 2. No crying occurred in 51/59 (86.4%) vaccinations in 5-9-year-olds, 25/86 (29.1%) vaccinations in 13-59-month-olds and 172/1067 (16.1%) vaccinations in infants. Mean administration time ranged from 2.6 to 4.6 minutes and was longer for younger age groups. These data show that vaccination by DVI was feasible and well tolerated in infants and children in this rural hospital in western Kenya, when performed by skilled injectors. We also report that shipping and storage in liquid nitrogen vapor phase was simple and efficient. (Clinicaltrials.gov NCT02687373).

Gender Differences in Modifying Lumbopelvic Motion during Hip Medial Rotation in People with Low Back Pain

Reducing increased or early lumbopelvic motion during trunk or limb movements may be an important component of low back pain treatment. The ability to reduce lumbopelvic motion may be influenced by gender. The purpose of the current study was to examine the effect of gender on the ability of people with low back pain to reduce lumbopelvic motion during hip medial rotation following physical therapy treatment. Lumbopelvic rotation and hip rotation before the start of lumbopelvic rotation were assessed pre- and posttreatment for 16 females and 15 males. Both men and women decreased lumbopelvic rotation and completed more hip rotation before the start of lumbopelvic rotation post-treatment compared to pre-treatment. Men demonstrated greater lumbopelvic rotation and completed less hip rotation before the start of lumbopelvic rotation than women both pre- and post-treatment. Both men and women reduced lumbopelvic motion relative to their starting values, but, overall, men still demonstrated greater and earlier lumbopelvic motion. These results may have important implications for understanding differences in the evaluation and treatment of men and women with low back pain.

Differences in end-range lumbar flexion during slumped sitting and forward bending between low back pain subgroups and genders

Patterns of lumbar posture and motion are associated with low back pain (LBP). Research suggests LBP subgroups demonstrate different patterns during common tasks. This study assessed differences in end-range lumbar flexion during two tasks between two LBP subgroups classified according to the Movement System Impairment model. Additionally, the impact of gender differences on subgroup differences was assessed. Kinematic data were collected. Subjects in the Rotation (Rot) and Rotation with Extension (RotExt) LBP subgroups were asked to sit slumped and bend forward from standing. Lumbar end-range flexion was calculated. Subjects reported symptom behaviour during each test. Compared to the RotExt subgroup, the Rot subgroup demonstrated greater end-range lumbar flexion during slumped sitting and a trend towards greater end-range lumbar flexion with forward bending. Compared to females, males demonstrated greater end-range lumbar flexion during slumped sitting and forward bending. A greater proportion of people in the Rot subgroup reported symptoms with each test compared to the RotExt subgroup. Males and females were equally likely to report symptoms with each test. Gender differences were not responsible for LBP subgroup differences. Subgrouping people with LBP provides insight into differences in lumbar motion within the LBP population. Results suggesting potential consistent differences across flexion-related tasks support the presence of stereotypical movement patterns that are related to LBP.

Sex differences in lumbopelvic movement patterns during hip medial rotation in people with chronic low back pain

OBJECTIVE

To examine sex differences in lumbopelvic motion and symptom behavior during hip medial rotation in people with low back pain (LBP). We hypothesized that men would demonstrate greater and earlier lumbopelvic motion and would be more likely to report increased symptoms compared with women.

DESIGN

Cross-sectional observational study.

SETTING

University musculoskeletal analysis laboratory.

PARTICIPANTS

Persons with chronic LBP (N=59; 30 men, 29 women) were recruited from the community and a university-based physical therapy clinic.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Lumbopelvic rotation range of motion, amount of hip rotation completed before the start of lumbopelvic motion, and provocation of LBP symptoms during the test of prone hip medial rotation were measured.

RESULTS

Men demonstrated significantly more lumbopelvic rotation (men, 10.0°±5.1°; women, 4.5°±3.9°; P<.001) and completed less hip rotation before the start of lumbopelvic motion (men, 5.4°±3.8°; women, 16.0°±13.2°; P<.001) compared with women. Additionally, a significantly greater percentage of men (60.0%) than women (34.5%; P=.050) reported increased symptoms with hip medial rotation.

CONCLUSIONS

Men could be at greater risk than women for experiencing LBP symptoms related to hip medial rotation as a result of greater and earlier lumbopelvic motion.

Low interrater reliability of examiners performing the prone instability test: a clinical test for lumbar shear instability

OBJECTIVE

To test the interrater reliability of examiners performing the prone instability test (PIT), a clinical test proposed to identify lumbar shear instability.

DESIGN

Cross-sectional test-retest design examining individuals with mechanical low back pain (LBP).

SETTING

University-based musculoskeletal analysis laboratory.

PARTICIPANTS

Individuals (N=30) with mechanical LBP recruited from community sources in a metropolitan region.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASURES

Repeated measures of a clinical examination test proposed to identify lumbar shear instability.

RESULTS

Interrater reliability of examiners' judgments of PIT results were indexed with percentage of agreement and κ statistic. Examiners obtained 63% agreement and κ of .10 (95% confidence interval, -.27 to .47). Adjusted κ values based on prevalence and bias indexes were calculated to evaluate the effect on κ. The prevalence index associated with examiner judgments of the PIT was .43, and bias index was .03. The prevalence-adjusted bias-adjusted κ value was slightly higher than the unadjusted κ value (κ=.27; 95% confidence interval, -.08 to .61).

CONCLUSIONS

Results of our study are not consistent with those of previous studies examining the reliability of therapists performing the PIT. We conclude that examiners do not attain acceptable interrater reliability when performing procedures for the PIT based on the information currently provided in the literature. Based on our experience, we suggest further exploration, standardization, and clarification of procedural details to improve therapists' ability to conduct the PIT on individuals with LBP.

Effect of classification-specific treatment on lumbopelvic motion during hip rotation in people with low back pain

Increased and early lumbopelvic motion during trunk and limb movements is thought to contribute to low back pain (LBP). Therefore, reducing lumbopelvic motion could be an important component of physical therapy treatment. Our purpose was to examine the effects of classification-specific physical therapy treatment (Specific) based on the Movement System Impairment (MSI) model and non-specific treatment (Non-Specific) on lumbopelvic movement patterns during hip rotation in people with chronic LBP. We hypothesized that following treatment people in the Specific group would display decreased lumbopelvic rotation and achieve more hip rotation before lumbopelvic rotation began. We hypothesized that people in the Non-Specific group would display no change in these variables. Kinematic data collected before and after treatment for hip lateral and medial rotation in prone were analyzed. The Specific group (N = 16) demonstrated significantly decreased lumbopelvic rotation and achieved greater hip rotation before the onset of lumbopelvic rotation after treatment with both hip lateral and medial rotation. The Non-Specific group (N = 16) demonstrated significantly increased lumbopelvic rotation and no change in hip rotation achieved before the onset of lumbopelvic rotation. People who received treatment specific to their MSI LBP classification displayed decreased and later lumbopelvic motion with hip rotation, whereas people who received generalized non-specific treatment did not.

Differences in activity limitation between 2 low back pain subgroups based on the movement system impairment model

OBJECTIVE

To examine if activity limitation differs between 2 low back pain (LBP) subgroups in the Movement System Impairment (MSI) model.

DESIGN

Cross-sectional observational study.

SETTING

University medical center musculoskeletal analysis laboratory.

PARTICIPANTS

Convenience sample of 83 subjects with chronic LBP who were subgrouped as rotation (Rot) or rotation with extension (RotExt) according to the MSI model.

INTERVENTIONS

Not applicable.

MAIN OUTCOME MEASUREMENTS

Subjects completed the modified Oswestry Low Back Pain Disability Questionnaire and the physical function subscale of the 36-Item Short-Form Health survey (SF-36 PFS) to assess activity limitation. Subjects also completed baseline measures related to demographics, LBP history, pain intensity, habitual activity level, general health status, and fear-avoidance behavior. Independent-samples t-tests, χ² tests of independence, and 2-way analysis of variance tests were used to analyze the data.

RESULTS

Subjects in the Rot subgroup reported greater activity limitation on the modified Oswestry Questionnaire (P = .02) and SF-36 PFS (P = .03) than subjects in the RotExt subgroup. No other differences between LBP subgroups were significant (P > .05), except gender. More women (71%) than men (29%) were in the RotExt subgroup (P = .03). However, there was no main effect of gender and no interaction effect of gender and LBP subgroup on the modified Oswestry Questionnaire or the SF-36 PFS (P > .05).

CONCLUSIONS

These results support that the Rot and RotExt LBP subgroups based on the MSI model differ with regard to variables that index activity limitation, with the Rot subgroup reporting greater limitation on both activity limitation measures. These differences are not the result of differences in other baseline measures.

Pulmonary gas exchange in the morbidly obese

The literature on pulmonary gas exchange at rest, during exercise, and with weight loss in the morbidly obese (body mass index or BMI > or = 40 kg m(-2)) is reviewed. Forty-one studies were found (768 subjects weighted mean = 40 years old, BMI = 48 kg m(-2)). The alveolar-to-arterial oxygen partial pressure difference (AaDO2) was large at rest in upright subjects at sea level (23, range 5-38 mmHg) while the arterial pressure of oxygen (PaO2) was low (81, range 50-95 mmHg). Arterial pressure of carbon dioxide (PaCO2) was normal. At peak exercise (162 W), gas exchange improves. Weight loss of 45 kg (BMI = -13 kg m(-2)) over 18 months is associated with an improvement in PaO2 (by 10 mmHg, range 1-23 mmHg), a reduction in AaDO2 (by 8 mmHg, range -3 to -16 mmHg), and PaCO2 (by -3 mmHg, range 3 to -14 mmHg) at rest. Every 5-6 kg reduction in weight increases PaO2 by 1 and reduces AaDO2 by 1 mmHg, respectively. Morbidly obese women have better gas exchange at rest compared with morbidly obese men which is likely due to lower waist-to-hip ratios in women than from differences in weight or BMI.

Effect of metatarsal phalangeal joint extension on plantar soft tissue stiffness and thickness

BACKGROUND

Plantar soft tissue stiffness and thickness are important biomechanical variables to understand stress concentrations that may contribute to tissue injury.

OBJECTIVE

The purpose of this study was to determine the effects of passive metatarsal phalangeal joint (MPJ) extension on plantar soft tissue stiffness and thickness.

METHODS

Seventeen healthy participants (7 male, 10 female, mean age 25.3 years, S.D. 4.4 years, mean BMI 24.7 kg/m(2), S.D. 3.2 kg/m(2)) were tested. Plantar soft tissue stiffness and thickness were measured at the metatarsal heads, midfoot and heel using a custom-built indentor device and an ultrasound machine.

RESULTS

Indicators of soft tissue stiffness (K1 values) at the metatarsal heads and midfoot showed increases in stiffness of 81-88% (S.D.20-33%) in the MPJ extension position compared with the MPJ neutral position. Soft tissue thickness measures at the metatarsal heads with the MPJ in neutral ranged from a mean of 8.9 to 13.5mm and decreased, on average, by 8.8% (S.D. 2.9%) with MPJ extension.

CONCLUSIONS

MPJ extension has a profound effect on increasing forefoot plantar soft tissue stiffness and a consistent but minimal effect on reducing soft tissue thickness. These changes may help transform the foot into a rigid lever at push-off consistent with the theory of the windlass mechanism.

Cross-protection between attenuated Plasmodium berghei and P. yoelii sporozoites

An attenuatedPlasmodium falciparum sporozoite (PfSPZ) vaccine is under development, in part, based on studies in mice withP. berghei. We usedP. berghei andP. yoelii to study vaccine-induced protection against challenge with a species of parasite different from the immunizing parasite in BALB/c mice. One-hundred percent of mice were protected against homologous challenge. Seventy-nine percent immunized with attenuatedP. berghei sporozoite (PbSPZ)(six experiments) were protected against challenge withP. yoelii sporozoite (PySPZ), and 63% immunized with attenuatedPySPZ(three experiments) were protected against challenge withPbSPZ. Antibodies in sera of immunized mice only recognized homologous sporozoites and could not have mediated protection against heterologous challenge. Immunization with attenuatedPySPZ orPbSPZ induced CD8⁺ T cell-dependent protection against heterologous challenge. Immunization with attenuatedPySPZ induced CD8⁺ T cell-dependent protection against homologous challenge. However, homologous protection induced by attenuatedPbSPZ was not dependent on CD8⁺ or CD4⁺ T cells, and depletion of both populations only reduced protection by 36%. Immunization of C57BL/10 mice withPbSPZ induced CD8⁺ T cell-dependent protection againstP. berghei, but no protection againstP. yoelii. The cross-protection data in BALB/c mice support testing a human vaccine based on attenuatedPfSPZ for its efficacy againstP. vivax.

Sequencing the genome of Plasmodium falciparum

Advances in microbial genomic sequencing have the potential to revolutionize the control of infectious diseases. Recently, a consortium of researchers and funding agencies from the United States and Great Britain have embarked on a project to sequence the genome from Plasmodium falciparum, the most important cause of human malaria. The Malaria Genome Sequencing Project has reached an important milestone with the completion of the entire DNA sequence and annotation of chromosome 2, a 950 kilobase chromosome of Plasmodium falciparum. This review article will provide an overview of the malaria genome sequencing project, highlight progress in the field of microbial sequencing, and suggest new directions for future malaria research.

Mutating the anchor residues associated with MHC binding inhibits and deviates CD8+ T cell mediated protective immunity against malaria

We investigated whether immune responses induced by immunization with plasmid DNA are restricted predominantly to immunodominant CD8+ T cell epitopes, or are raised against a breadth of epitopes including subdominant CD8+ and CD4+ T cell epitopes. Site-directed mutagenesis was used to change one or more primary anchor residues of the immunodominant CD8+ T cell epitope on the Plasmodium yoelii circumsporozoite protein, and in vivo protective efficacy and immune responses against defined PyCSP CD8+ and/or CD4+ epitopes were determined. Mutation of the P2 but not P9 or P10 anchor residues decreased protection and completely abrogated the antigen-specific CD8+ CTL activity and CD8+ dependent IFN-gamma responses to the immunodominant CD8+ epitope and overlapping CD8+/CD4+ epitope. Moreover, mutation deviated the immune response towards a CD4+ T cell IFN-gamma dependent profile, with enhanced lymphoproliferative responses to the immunodominant and subdominant CD4+ epitopes and enhanced antibody responses. Responses to the subdominant CD8+ epitope were not induced. Our data demonstrate that protective immunity induced by PyCSP DNA vaccination is directed predominantly against the single immunodominant CD8+ epitope, and that although responses can be induced against other epitopes, these are mediated by CD4+ T cells and are not capable of conferring optimal protection against challenge.

Effect on antibody and T-cell responses of mixing five GMP-produced DNA plasmids and administration with plasmid expressing GM-CSF

One potential benefit of DNA vaccines is the capacity to elicit antibody and T-cell responses against multiple antigens at the same time by mixing plasmids expressing different proteins. A possible negative effect of such mixing is interference among plasmids regarding immunogenicity. In preparation for a clinical trial, we assessed the immunogenicity of GMP-produced plasmids encoding five Plasmodium falciparum proteins, PfCSP, PfSSP2, PfEXP1, PfLSA1, and PfLSA3, given as a mixture, or alone. The mixture induced higher levels of antibodies against whole parasites than did the individual plasmids, but was associated with a decrease in antibodies to individual P. falciparum proteins. T-cell responses were in general decreased by administration of the mixture. Immune responses to individual plasmids and mixtures were generally higher in inbred mice than in outbreds. In inbred BALB/c and C57BL/6 mice, coadministration of a plasmid expressing murine granulocyte-macrophage colony-stimulating factor (mGM-CSF), increased antibody and T-cell responses, but in outbred CD-1 mice, coadministration of mGM-CSF was associated with a decrease in antibody responses. Such variability in data from studies in different strains of mice underscores the importance of genetic background on immune response and carefully considering the goals of any preclinical studies of vaccine mixtures planned for human trials.

Production of monoclonal antibodies against a 19-kD recombinant Plasmodium vivax MSP1 for detection of P. vivax malaria in Turkey

Plasmodium vivax malaria, which is transmitted to humans by mosquitoes, is one of the most important parasitic diseases in Turkey. The major protein on the surface of asexual erythrocytic stage merozoites of P. vivax (Pv) is 200 kD and called major merozoite surface protein-1 (PvMSP1). Polyclonal antibodies against the 19-kD C-terminal fragment of PvMSP1 (PvMSP1(19)) are protective in monkey models of P. vivax and associated with protection in field studies. In this research, monoclonal antibodies were produced against PvMSP1(19). A total of 214 IgG(1) antibody-releasing hybridomas were obtained and three monoclonal antibodies were produced (PvMSP1(19).1, PvMSP1(19).2, and PvMSP1(19).3) and selected for further study. They have now been purified from ascitic fluid on a Staphylococcus protein A affinity column. These are the first monoclonal antibodies produced against P. vivax in Turkey and the first monoclonal antibodies produced against this recombinant PvMSP1(19) in the world. The monoclonal antibodies will be used to study the epidemiology of P. vivax in patients with malaria in Turkey, and to develop better strategies for early diagnosis and treatment of the disease in our population.

The Malaria Genome Sequencing Project

An international consortium of genome centres, advanced development teams and funding agencies has begun the task of sequencing the genome of the parasite Plasmodium falciparum, the most important cause of human malaria. Sequencing is proceeding chromosome by chromosome, and the annotated sequence of chromosome 2 is nearly finished. With the continual release of sequence data as they are generated, malaria researchers have access to a steady stream of genomic sequences and will soon have the complete annotation of all of the estimated 5000-7000 P. falciparum genes. The task will then be how to best apply these data to the development of new anti-malarial drugs, vaccines and diagnostic tests. This review provides a brief overview of the Malaria Genome Sequencing Project and suggests potential directions for future malaria research.

Utilization of genomic sequence information to develop malaria vaccines

Recent advances in the fields of genomics, proteomics and molecular immunology offer tremendous opportunities for the development of novel interventions against public health threats, including malaria. However, there is currently no algorithm that can effectively identify the targets of protective T cell or antibody responses from genomic data. Furthermore, the identification of antigens that will stimulate the most effective immunity against the target pathogen is problematic, particularly if the genome is large. Malaria is an attractive model for the development and validation of approaches to translate genomic information to vaccine development because of the critical need for effective anti-malarial interventions and because the Plasmodium parasite is a complex multistage pathogen targeted by multiple immune responses. Sterile protective immunity can be achieved by immunization with radiation-attenuated sporozoites, and anti-disease immunity can be induced in residents in malaria-endemic areas. However, the 23 Mb Plasmodium falciparum genome encodes more than 5300 proteins, each of which is a potential target of protective immune responses. The current generation of subunit vaccines is based on a single or few antigens and therefore might elicit too narrow a breadth of response. We are working towards the development of a new generation vaccine based on the presumption that duplicating the protection induced by the whole organism may require a vaccine nearly as complex as the organism itself. Here, we present our strategy to exploit the genomic sequence of P. falciparum for malaria vaccine development.

Chloroquine for the treatment of uncomplicated malaria in Guyana

At a public hospital in Georgetown, Guyana, 44 patients seeking treatment for symptomatic, slide-confirmed malaria were given standard chloroquine (CQ) therapy and followed for 28 days. The patients apparently had pure infections with Plasmodium falciparum (14), P. vivax (13) or P. malariae (one), or mixed infections either of P. falciparum and P. vivax (17) or of P. falciparum, P. malariae and P. vivax (two). Each received supervised treatment with 10 mg CQ base/kg on each of days 0 and 1, and 5 mg/kg on day 2. On the day of enrollment (day 0), the patients complained of fever (100%), headache (100%), malaise (94%), myalgia (79%), nausea (67%), vertigo (49%) and vomiting (33%). Many (39%) were ill enough to confine themselves to bed. On day 4, fewer of the subjects complained of fever (15%), headache (15%), malaise (6%), myalgia (21%), nausea (6%), vertigo (24%) or vomiting (0%) despite the relatively high (>48%) risk of therapeutic failure. The cumulative incidence of parasitological failure against P. falciparum was 15% at day 4, 33% at day 7 and 48% at day 14. All of the P. vivax and P. malariae infections cleared before day 4 and none recurred by day 7. Two infections with P. vivax recurred later (on day 14 or 28) but in the presence of less than adequate, whole-blood concentrations of CQ plus desethyl-chloroquine (i.e. <100 ng/ml). Taken together, the results indicate a high risk of therapeutic failure of CQ against P. falciparum but also indicate that resistance to CQ in P. vivax occurs infrequently in Guyana.

Randomized, parallel placebo-controlled trial of primaquine for malaria prophylaxis in Papua, Indonesia

Malaria causes illness or death in unprotected travelers. Primaquine prevents malaria by attacking liver-stage parasites, a property distinguishing it from most chemoprophylactics and obviating 4-week postexposure dosing. A daily adult regimen of 30 mg primaquine prevented malaria caused by Plasmodium falciparum and P. vivax for 20 weeks in 95 of 97 glucose-6-phosphate dehydrogenase (G6PD)-normal Javanese transmigrants in Papua, Indonesia. In comparison, 37 of 149 subjects taking placebo in a parallel trial became parasitemic. The protective efficacy of primaquine against malaria was 93% (95% confidence interval [CI] 71%-98%); against P. falciparum it was 88% (95% CI 48%-97%), and >92% for P. vivax (95% CI >37%-99%). Primaquine was as well tolerated as placebo. Mild methemoglobinemia (mean of 3.4%) returned to normal within 2 weeks. Blood chemistry and hematological parameters revealed no evidence of toxicity. Good safety, tolerance, and efficacy, along with key advantages in dosing requirements, make primaquine an excellent drug for preventing malaria in nonpregnant, G6PD-normal travelers.

Determining liver stage parasite burden by real time quantitative PCR as a method for evaluating pre-erythrocytic malaria vaccine efficacy

The detection and quantitation of blood stage parasitaemia is typically used as a surrogate endpoint for estimating the efficacy of vaccines targeted against the hepatic stage, as well as the erythrocytic stage, of the parasite. However, this does not provide an adequate means of evaluating the efficacy of vaccines, which may be only partially effective at the liver-stage. This is a particular concern for effective evaluation of immune enhancement strategies for candidate pre-erythrocytic stage vaccines. Here, we have developed and validated a method for detecting and quantitating liver stage parasites, using the TaqMan fluorescent real-time quantitative PCR system (PE Applied Biosystems). This method uses TaqMan primers designed to the Plasmodium yoelii 18S rRNA gene and rodent GAPDH to amplify products from infected mouse liver cDNA. The technique is highly reproducible as demonstrated with plasmid controls and capable of efficiently quantitating liver-stage parasite burden following a range of sporozoite challenge doses in strains of mice, which differ in their susceptibility to sporozoite infection. We have further demonstrated the capacity of this technique to evaluate the efficacy of a range of pre-erythrocytic stage vaccines. Our data establish this quantitative real-time PCR assay to be a fast and reproducible way of accurately assessing liver stage parasite burden and vaccine efficacy in rodent malaria models.

Codon optimization of gene fragments encoding Plasmodium falciparum merzoite proteins enhances DNA vaccine protein expression and immunogenicity in mice

In contrast to conventional vaccines, DNA and other subunit vaccines exclusively utilize host cell molecules for transcription and translation of proteins. The adenine plus thymine content of Plasmodium falciparum gene sequences (approximately 80%) is much greater than that of Homo sapiens (approximately 59%); consequently, codon usage is markedly different. We hypothesized that modifying codon usage of P. falciparum genes encoded by DNA vaccines from that used by the parasite to those resembling mammalian codon usage would lead to increased P. falciparum protein expression in vitro in mouse cells and increased antibody responses in DNA-vaccinated mice. We synthesized gene fragments encoding the receptor-binding domain of the 175-kDa P. falciparum erythrocyte-binding protein (EBA-175 region II) and the 42-kDa C-terminal processed fragment of the P. falciparum merozoite surface protein 1 (MSP-1(42)) using the most frequently occurring codon in mammals to code for each amino acid, and inserted the synthetic genes in DNA vaccine plasmids. In in vitro transient-expression assays, plasmids containing codon-optimized synthetic gene fragments (pS plasmids) showed greater than fourfold increased protein expression in mouse cells compared to those containing native gene fragments (pN plasmids). In mice immunized with 0.5, 5.0, or 50 microg of the DNA plasmids, the dose of DNA required to induce equivalent antibody titers was 10- to 100-fold lower for pS than for pN plasmids. These data demonstrate that optimizing codon usage in DNA vaccines can improve protein expression and consequently the immunogenicity of gene fragments in DNA vaccines for organisms whose codon usage differs substantially from that of mammals.

Microbial disease in humans: A genomic perspective

The approach of whole-genome shotgun sequencing coupled with the availability of computational algorithms to facilitate the assembly, gene prediction, and functional annotation of entire genomes has sparked a revolution in our understanding of the biology of free-living organisms. More than 40 bacterial genomes have been sequenced to date, of which several are important human pathogens. The capacity to sequence and assemble entire genomes of bacteria, pathogenic protozoans, and fungi in a rapid and cost-effective way has energized every aspect of microbial science. Comparative genome analysis allows us to dissect the evolutionary forces at work and provides insights into adaptations of microbes to their unique ecological niches. Factors that shape host-pathogen interactions and their outcomes include genetic polymorphisms in the microbial pathogen and host, both of which can impact on microbial virulence or host immune responses to infection. The availability of the genome sequence of entire organisms, together with the use of high-throughput sequence-based genomic technologies to define microbial and host physiological states, provides the unparalleled opportunity to better define clinical outcomes in the field of infectious diseases. There is one overarching lesson: completion of the genomic sequence of any species answers many questions, while at the same time it invites totally new questions.

Expression of the chemokine MIG is a sensitive and predictive marker for antigen-specific, genetically restricted IFN-gamma production and IFN-gamma-secreting cells

The evaluation of antigen-specific immune responses is critical for understanding the mechanisms of immune protection and for establishing the efficacy of candidate vaccines. Here, we describe a novel assay for IFN-gamma activity which is based on the flow cytometric detection of the chemokine, monokine induced by gamma interferon (MIG) as a sensitive and predictive measure of IFN-gamma-mediated effector function, and a surrogate marker for IFN-gamma-producing cells. Upregulation of MIG expression was demonstrated following in vitro activation of peripheral blood mononuclear cells (PBMCs) with defined CD8+ T-cell epitopes derived from influenza virus, cytomegalovirus (CMV), or Epstein-Barr virus (EBV) and was antigen-specific, genetically restricted and dependent on both CD8+ T cells and IFN-gamma. Furthermore, antigen-specific MIG expression was also demonstrated with Plasmodium falciparum circumsporozoite protein (CSP) peptides, using PBMCs from volunteers immunized with irradiated P. falciparum sporozoites. In multiple parallel experiments, the MIG assay was compared to conventional IFN-gamma ELISPOT, IFN-gamma ELISA, MIG ELISA and intracellular cytokine staining assays. The level of MIG expression was shown to be directly associated with the number of IFN-gamma spot-forming cells (SFCs) detected by ELISPOT (r2=0.94). Moreover, in all instances where cultures were considered positive by ELISPOT, a higher stimulation index was noted with the MIG assay as compared with the ELISPOT assay (on average at least threefold higher) and, in some cases, responses as detected by the MIG assay were significant, but the corresponding response as measured by ELISPOT was not significant. Finally, the flow-based MIG assay offers a number of practical and technical advantages over the ELISPOT assay. Our data validate this novel method for the detection of low as well as high levels of antigen-specific and genetically restricted IFN-gamma activity.

Enhancement of the immune response in rabbits to a malaria DNA vaccine by immunization with a needle-free jet device

We compared the needle free jet device device Biojector with syringe/needle as a method to administer a DNA vaccine encoding the Plasmodium falciparum circumsporozoite protein (PfCSP) in albino rabbits. A group of three rabbits was injected by the intramuscular (IM) route using a syringe/needle combination, a second group IM with the Biojector device and a third group both IM and intradermal (ID) using the Biojector. When animals were immunized with the Biojector IM or IM/ID as compared to the syringe/needle IM, we observed 10- and 50-fold greater antibody titers, as measured by enzyme immunoassay (EIA) and indirect fluorescence antibody test (IFAT), respectively. We also observed that the Biojector conferred a greater ability to prime the immune system as compared with the needle. The subsequent boosting of all animals with a recombinant canary pox virus (ALVAC) expressing PfCSP induced significantly higher titers in both Biojector groups of rabbits as compared with the needle and naive animals. These results provided the foundation for a clinical trial using the same regime.

Induction of CD4(+) T cell-dependent CD8(+) type 1 responses in humans by a malaria DNA vaccine

We assessed immunogenicity of a malaria DNA vaccine administered by needle i.m. or needleless jet injection [i.m. or i.m./intradermally (i.d.)] in 14 volunteers. Antigen-specific IFN-gamma responses were detected by enzyme-linked immunospot (ELISPOT) assays in all subjects to multiple 9- to 23-aa peptides containing class I and/or class II restricted epitopes, and were dependent on both CD8(+) and CD4(+) T cells. Overall, frequency of response was significantly greater after i.m. jet injection. CD8(+)-dependent cytotoxic T lymphocytes (CTL) were detected in 8/14 volunteers. Demonstration in humans of elicitation of the class I restricted IFN-gamma responses we believe necessary for protection against the liver stage of malaria parasites brings us closer to an effective malaria vaccine.

Incidence of symptomatic and asymptomatic Plasmodium falciparum infection following curative therapy in adult residents of northern Ghana

Adult residents of holoendemic malaria regions in Africa have a naturally acquired immunity (NAI) to malaria that renders them more resistant to new infections, limits parasitemia, and reduces the frequency and severity of illness. Given such attributes, it is not clear how one might evaluate drug or vaccine efficacy in adults without serious confounding. To determine symptomatic and asymptomatic malaria attack rates in adults of northern Ghana, 197 men and women underwent curative therapy for any pre-existing malaria infections at the start of the high transmission (wet) season. They were monitored for first parasitemia and first clinical episode of infection by Plasmodium falciparum over a 20-week period (May-October 1996). The cumulative incidence of primary infection by P. falciparum was 0.98 and incidence density of infection was calculated to be 7.0 cases/person-year. Symptoms were reported by 19.5% of the individuals at the time of first recurrent parasitemia. Incidence of infection, parasite density, and the frequency of symptoms were comparable in males and females. The results suggest that NAI did not provide these adults with significant defense against rapid re-infection and suggest that this population-infection design could serve to demonstrate the efficacy of a drug or vaccine in preventing parasitemia.

Multistage multiantigen heterologous prime boost vaccine for Plasmodium knowlesi malaria provides partial protection in rhesus macaques

A nonhuman primate model for malaria vaccine development allowing reliable, stringent sporozoite challenge and evaluation of both cellular and antibody responses is needed. We therefore constructed a multicomponent, multistage DNA vaccine for the simian malaria species Plasmodium knowlesi including two preerythrocytic-stage antigens, the circumsporozoite protein (PkCSP) and sporozoite surface protein 2 (PkSSP2), and two blood stage antigens, apical merozoite antigen 1 (PkAMA1) and merozoite surface protein 1 (PkMSP1p42), as well as recombinant canarypox viruses encoding the four antigens (ALVAC-4). The DNA vaccine plasmids expressed the corresponding antigens in vitro and induced antiparasite antibodies in mice. Groups of four rhesus monkeys received three doses of a mixture of the four DNA vaccine plasmids and a plasmid encoding rhesus granulocyte-monocyte colony-stimulating factor, followed by boosting with a single dose of ALVAC-4. Three groups received the priming DNA doses by different routes, either by intramuscular needle injection, by intramuscular injection with a needleless injection device, the Biojector, or by a combination of intramuscular and intradermal routes by Biojector. Animals immunized by any route developed antibody responses against sporozoites and infected erythrocytes and against a recombinant PkCSP protein, as well as gamma interferon-secreting T-cell responses against peptides from PkCSP. Following challenge with 100 P. knowlesi sporozoites, 1 of 12 experimental monkeys was completely protected and the mean parasitemia in the remaining monkeys was significantly lower than that in 4 control monkeys. This model will be important in preclinical vaccine development.

Exploring the transcriptome of the malaria sporozoite stage

Most studies of gene expression in Plasmodium have been concerned with asexual and/or sexual erythrocytic stages. Identification and cloning of genes expressed in the preerythrocytic stages lag far behind. We have constructed a high quality cDNA library of the Plasmodium sporozoite stage by using the rodent malaria parasite P. yoelii, an important model for malaria vaccine development. The technical obstacles associated with limited amounts of RNA material were overcome by PCR-amplifying the transcriptome before cloning. Contamination with mosquito RNA was negligible. Generation of 1,972 expressed sequence tags (EST) resulted in a total of 1,547 unique sequences, allowing insight into sporozoite gene expression. The circumsporozoite protein (CS) and the sporozoite surface protein 2 (SSP2) are well represented in the data set. A BLASTX search with all tags of the nonredundant protein database gave only 161 unique significant matches (P(N) < or = 10(-4)), whereas 1,386 of the unique sequences represented novel sporozoite-expressed genes. We identified ESTs for three proteins that may be involved in host cell invasion and documented their expression in sporozoites. These data should facilitate our understanding of the preerythrocytic Plasmodium life cycle stages and the development of preerythrocytic vaccines.

Immunogenicity of well-characterized synthetic Plasmodium falciparum multiple antigen peptide conjugates

Given the emerging difficulties with malaria drug resistance and vector control, as well as the persistent lack of an effective vaccine, new malaria vaccine development strategies are needed. We used a novel methodology to synthesize and fully characterize multiple antigen peptide (MAP) conjugates containing protective epitopes from Plasmodium falciparum and evaluated their immunogenicity in four different strains of mice. A di-epitope MAP (T3-T1) containing two T-cell epitopes of liver stage antigen-1 (LSA-1), a di-epitope MAP containing T-cell epitopes from LSA-1 and from merozoite surface protein-1, and a tri-epitope MAP (T3-CS-T1) containing T3-T1 and a potent B-cell epitope from the circumsporozoite protein central repeat region were tested in this study. Mice of all four strains produced peptide-specific antibodies; however, the magnitude of the humoral response indicated strong genetic restriction between the different strains of mice. Anti-MAP antibodies recognized stage-specific proteins on the malaria parasites in an immunofluorescence assay. In addition, serum from hybrid BALB/cJ x A/J CAF1 mice that had been immunized with the tri-epitope MAP T3-CS-T1 successfully inhibited the malaria sporozoite invasion of hepatoma cells in vitro. Spleen cells from immunized mice also showed a genetically restricted cellular immune response when stimulated with the immunogen in vitro. This study indicates that well-characterized MAPs combining solid-phase synthesis and conjugation chemistries are potent immunogens and that this approach can be utilized for the development of subunit vaccines.

Safety of a GM-CSF adjuvant-plasmid DNA malaria vaccine

MuStDO 5 is a multivalent plasmid DNA vaccine for malaria comprised of five plasmid DNAs encoding five proteins from Plasmodium falciparum and one plasmid DNA encoding human GM-CSF. To evaluate the safety of MuStDO 5, a series of pre-clinical studies were conducted in mice and rabbits. In pharmacology studies in mice, GM-CSF could not be detected in the serum following either intramuscular or a combined intramuscular/intradermal administration of the vaccine, but was readily detected in the muscle following intramuscular administration. In a tissue distribution study in mice, MuStDO 5 plasmid DNA was detected by PCR initially in highly vascularized tissues, while at later time-points the plasmid DNA was detected primarily at the site(s) of injection. In GLP safety studies in mice and rabbits, repeated intramuscular/intradermal administration of the MuStDO 5 vaccine was found to be safe and well tolerated without any evidence of autoimmune pathology.

Immunogenicity and protective efficacy of a Plasmodium yoelii Hsp60 DNA vaccine in BALB/c mice

The gene encoding the 60-kDa heat shock protein of Plasmodium yoelii (PyHsp60) was cloned into the VR1012 and VR1020 mammalian expression vectors. Groups of 10 BALB/c mice were immunized intramuscularly at 0, 3, and 9 weeks with 100 microg of PyHsp60 DNA vaccine alone or in combination with 30 microg of pmurGMCSF. Sera from immunized mice but not from vector control groups recognized P. yoelii sporozoites, liver stages, and infected erythrocytes in an indirect fluorescent antibody test. Two weeks after the last immunization, mice were challenged with 50 P. yoelii sporozoites. In one experiment the vaccine pPyHsp60-VR1012 used in combination with pmurGMCSF gave 40% protection (Fisher's exact test; P = 0.03, vaccinated versus control groups). In a second experiment this vaccine did not protect any of the immunized mice but induced a delay in the onset of parasitemia. In neither experiment was there any evidence of a protective effect against the asexual erythrocytic stage of the life cycle. In a third experiment mice were primed with PyHsp60 DNA, were boosted 2 weeks later with 2 x 10(3) irradiated P. yoelii sporozoites, and were challenged several weeks later. The presence of PyHsp60 in the immunization regimen did not lead to reduced blood-stage infection or development of parasites in hepatocytes. PyHsp60 DNA vaccines were immunogenic in BALB/c mice but did not consistently, completely protect against sporozoite challenge. The observation that in some of the PyHsp60 DNA vaccine-immunized mice there was protection against infection or a delay in the onset of parasitemia after sporozoite challenge deserves further evaluation.

DNA-based vaccines against malaria: status and promise of the Multi-Stage Malaria DNA Vaccine Operation

The introduction of DNA vaccine technology has facilitated an unprecedented multi-antigen approach to developing an effective vaccine against complex pathogens such as the Plasmodium spp. parasites that cause malaria. We have established the capacity of DNA vaccines encoding Plasmodium antigens to induce CD8(+) cytotoxic T lymphocyte and interferon-gamma responses in mice, monkeys and humans. However, like others, we have found that the first or second generation DNA vaccines on their own are not optimal, and have demonstrated the potential of heterologous prime/boost immunisation strategies involving priming with DNA and boosting with poxvirus or recombinant protein in adjuvant. In this review, we summarise the current status and promise of our programmatic efforts to develop a DNA-based vaccine against malaria, our Multi-Stage Malaria DNA Vaccine Operation, and illustrate the transition of promising developments in the laboratory to clinical assessment in humans.

Chloroquine/doxycycline combination versus chloroquine alone, and doxycycline alone for the treatment of Plasmodium falciparum and Plasmodium vivax malaria in northeastern Irian Jaya, Indonesia

Combination therapy is one method of overcoming the global challenge of drug-resistant Plasmodium falciparum malaria. We conducted a hospital-based 28-day in vivo test comparing chloroquine/doxycycline to chloroquine or doxycycline alone for treating P. falciparum and Plasmodium vivax malaria in Irian Jaya, Indonesia. Eighty-nine patients with uncomplicated falciparum malaria were randomized to standard dose chloroquine (n = 30), doxycycline (100 mg every 12 hours [7 days], n = 20), or chloroquine with doxycycline (n = 39); corresponding numbers for vivax malaria (n = 63) were 23, 16, 24. Endpoints were parasite sensitivity (S) or resistance (RI/RII/RIII). Of the 105 evaluable patients, chloroquine/doxycycline cured (S) 20/22 (90.9% [95% CI 78.9-100%]) patients with P. falciparum malaria; 2/22 (9.1% [0-21%]) were RIII resistant. Doxycycline cured 11/17 (64.7% [42.0-87.4%]) patients, and chloroquine 4/20 (20% [2.5-37.5%]). Against P. vivax, chloroquine/doxycycline cured (S) 12/17 (70.6% [48.9-92.2%]) patients, doxycycline 4/12 (33.3% [6.6-59.9%]), and chloroquine 5/17 (29.4% [7.7-51.1%]). Chloroquine/doxycycline was effective against P. falciparum but only modestly effective against P. vivax. These findings support the use of chloroquine/doxycycline as an inexpensive alternative to mefloquine for treating chloroquine-resistant P. falciparum but not chloroquine-resistant P. vivax in this setting.

Induction of biologically active antibodies in mice, rabbits, and monkeys by Plasmodium falciparum EBA-175 region II DNA vaccine

BACKGROUND

Plasmodium falciparum merozoites bind to and invade human erythrocytes via specific erythrocyte receptors. This establishes the erythrocytic stage of the parasite life cycle that causes clinical disease resulting in 2-3 million deaths per year. We tested the hypothesis that a Plasmodium falciparum ligand, EBA-175 region II (RII), which binds its erythrocyte receptor glycophorin A during invasion, can be used as an immunogen to induce antibodies that block the binding of RII to erythrocytes and thereby inhibit parasite invasion of erythrocytes. Accordingly, we immunized mice, rabbits, and monkeys with DNA plasmids that encoded the 616 amino acid RII.

MATERIALS AND METHODS

DNA vaccine plasmids that targeted the secretion of recombinant RII protein with and without the universal T-cell helper epitopes P2P30 were used to immunize mice, rabbits, and Aotus monkeys. RII specific antibodies were assessed by IFA, ELISA, blocking of native [35S] labeled EBA-175 binding to human erythrocytes, and growth inhibition assays, all in vitro.

RESULTS

The RII DNA plasmids were highly immunogenic as measured by ELISA and IFA. The anti-RII antibodies blocked the binding of native EBA-175 to erythrocytes, and rosetting of erythrocytes on COS-7 cells expressing RII. Most important, murine and rabbit anti-RII antibodies inhibited the invasion of merozoites into erythrocytes. We immunized nonhuman primates and showed that the RII-DNA plasmids were immunogenic and well tolerated in these monkeys. Monkeys were challenged with parasitized erythrocytes; one of three monkeys that received RII DNA plasmid was protected from fulminant disease. After challenge with live parasites, anti-RII antibody titers were boosted in the immunized monkeys.

CONCLUSIONS

By proving the hypothesis that anti-RII antibodies can block merozoite invasion of erythrocytes, these studies pave the way for the clinical evaluation of EBA-175 as a receptor-blockade vaccine.

HLA-A*01-restricted cytotoxic T-lymphocyte epitope from the Plasmodium falciparum circumsporozoite protein

Here, we report the identification of a novel CD8+ cytotoxic T-lymphocyte epitope on the Plasmodium falciparum circumsporozoite protein (3D7; amino acids 310 to 319 [EPSDKHIKEY]) that is restricted by HLA-A*01 and is recognized by human volunteers immunized with irradiated P. falciparum sporozoites. HLA-A*01 is the second most common HLA allele among Caucasians.

Interleukin-12- and gamma interferon-dependent protection against malaria conferred by CpG oligodeoxynucleotide in mice

Unmethylated CpG dinucleotides in bacterial DNA or synthetic oligodeoxynucleotides (ODNs) cause B-cell proliferation and immunoglobulin secretion, monocyte cytokine secretion, and activation of natural killer (NK) cell lytic activity and gamma interferon (IFN-gamma) secretion in vivo and in vitro. The potent Th1-like immune activation by CpG ODNs suggests a possible utility for enhancing innate immunity against infectious pathogens. We therefore investigated whether the innate immune response could protect against malaria. Treatment of mice with CpG ODN 1826 (TCCATGACGTTCCTGACGTT, with the CpG dinucleotides underlined) or 1585 (ggGGTCAACGTTGAgggggG, with g representing diester linkages and phosphorothioate linkages being to the right of lowercase letters) in the absence of antigen 1 to 2 days prior to challenge with Plasmodium yoelii sporozoites conferred sterile protection against infection. A higher level of protection was consistently induced by CpG ODN 1826 compared with CpG ODN 1585. The protective effects of both CpG ODNs were dependent on interleukin-12, as well as IFN-gamma. Moreover, CD8+ T cells (but not CD4+ T cells), NK cells, and nitric oxide were implicated in the CpG ODN 1585-induced protection. These data establish that the protective mechanism induced by administration of CpG ODN 1585 in the absence of parasite antigen is similar in nature to the mechanism induced by immunization with radiation-attenuated P. yoelii sporozoites or with plasmid DNA encoding preerythrocytic-stage P. yoelii antigens. We were unable to confirm whether CD8+ T cells, NK cells, or nitric oxide were required for the CpG ODN 1826-induced protection, but this may reflect differences in the potency of the ODNs rather than a real difference in the mechanism of action of the two ODNs. This is the first report that stimulation of the innate immune system by CpG immunostimulatory motifs can confer sterile protection against malaria.

Prospects for vaccines to protect against AIDS, tuberculosis, and malaria

Given the scope of the worldwide health problems caused by the acquired immunodeficiency syndrome, tuberculosis, and malaria, it is imperative that vaccines be developed to prevent these infections. Recent advances in the understanding of these diseases suggest that T-lymphocyte-mediated immunity is important in containing these infections. The application of novel vaccine technologies for eliciting this type of immunity promises to provide successful vaccines for controlling the spread of these deadly infections.

Expression, extracellular secretion, and immunogenicity of the Plasmodium falciparum sporozoite surface protein 2 in Salmonella vaccine strains

Deleting transmembrane alpha-helix motifs from Plasmodium falciparum sporozoite surface protein (SSP-2) allowed its secretion from Salmonella enterica serovar Typhimurium SL3261 and S. enterica serovar Typhi CVD 908-htrA by the Hly type I secretion system. In mice immunized intranasally, serovar Typhimurium constructs secreting SSP-2 stimulated greater gamma interferon splenocyte responses than did nonsecreting constructs (P = 0.04).

Protection of Aotus monkeys by Plasmodium falciparum EBA-175 region II DNA prime-protein boost immunization regimen

Aotus monkeys received 4 doses of Plasmodium falciparum EBA-175 region II vaccine as plasmid DNA (Dv-Dv) or recombinant protein in adjuvant (Pv-Pv) or as 3 doses of DNA and 1 dose of protein (Dv-Pv). After 3 doses, antibody titers were approximately 10(4) in DNA-immunized monkeys and 10(6) in protein-immunized monkeys. A fourth dose did not significantly boost antibody responses in the Dv-Dv only or Pv-Pv only groups, but titers were boosted to approximately 10(6) in monkeys in the Dv-Pv group. Four weeks after the last immunization, the animals were challenged with 10(4) P. falciparum-parasitized erythrocytes. Peak levels of parasitemia were lower in the 16 monkeys that received region II-containing plasmids or proteins than in the 16 controls (geometric mean: 194,178 and 410,110 parasites/microL, respectively; P=.013, Student's t test). Three of 4 monkeys in the Dv-Pv group did not require treatment. These data demonstrate that immunization with EBA-175 region II induces a significant antiparasite effect in vivo.

ELISPOT assay for detection of peptide specific interferon-gamma secreting cells in rhesus macaques

A reliable procedure to measure antigen specific T cell responses in rhesus macaques is required to determine the efficacy of vaccines and immunotherapies. The currently available T cell assays are poorly quantifiable or technically difficult to perform. Classical 51Cr-release cytotoxic T cell (CTL) assays are cumbersome and difficult to quantitate reproducibly. Detection of specific T-cell using MHC-peptide tetrameric complexes is highly sensitive, but requires knowledge of MHC type and prior identification of T cell epitopes. We therefore developed a rhesus interferon-gamma (IFN-gamma) ELISPOT assay capable of detecting IFN-gamma secretion in response to stimulation with pooled 20-mer peptides. Peripheral blood mononuclear cells (PBMCs) from rhesus monkeys immunized with a DNA vaccine and recombinant canary pox encoding the Plasmodium knowlesi circumsporozoite protein (PkCSP) were incubated with pools of peptides from PkCSP. Positive responses to peptide pools and individual peptides ranging from 100 to 450 spot forming cells (SFC)/10(6) PBMC were detected in four of four immunized monkeys and in zero of two control monkeys. In two monkeys studied in detail, the IFN-gamma response was focussed on a single 20-mer peptide, QGDGANAGQPQAQGDGANAG, and was dependent on CD4(+), but not CD8(+), T cells. Background responses in control monkeys and preimmunization PBMCs ranged from 10 to 50 SFC/10(6) PBMC. The average within assay and between assay coefficients of variation (CV) for this peptide ELISPOT were 21.9 and 24.7%, respectively. This peptide IFN-gamma assay will be a useful tool for evaluation of T cell responses in rhesus macaques.

Infectious disease. Research (genomics) is crucial to attacking malaria

Solving the enormous problem of malaria worldwide will require a balance between investments in research and control. In this point-counterpoint, two scientists describe the rationales for these very different strategies. Steve Hoffman believes that genomics research is the best investment in the future if we have the vision of malaria eradication. Chris Curtis presents an opposing viewpoint, that low-tech control approaches are the practical ones under current conditions.

Differences in epitope recognition, isotype and titer of antisera to Plasmodium falciparum merozoite surface protein 4 raised by different modes of DNA or protein immunization

Plasmodium falciparum merozoite surface protein 4 (MSP4) is being developed as a component of a subunit vaccine against asexual stages of malaria. Three DNA constructs were produced that induced expression of MSP4 either in the cytoplasm of transfected cells or secreted from cells under the control of the human tissue plasminogen activator (TPA) signal or the native P. falciparum MSP4 signal. Only the construct containing the TPA signal induced detectable antibodies in mice, although gene expression was demonstrated in all constructs and MSP4 was shown to be secreted using either signal by in vitro transient transfection of COS cells. Two recombinant MSP4 proteins that encoded the same sequence as the plasmid DNA were produced in E. coli (EcMSP4-His) and S. cerevisiae (yMSP4-His) and used to raise antibodies in mice. Comparison of the antibodies elicited by these various antigen formulations showed differences in titer, isotype and epitope recognition. The titer of antibodies induced by DNA vaccination was lower than that induced by yMSP4-His, which in turn was lower than that induced by EcMSP4-His. The isotype profiles of the antibodies were also different, the plasmid DNA induced predominantly IgG(2a) responses whereas the two proteins induced predominantly IgG(1) responses. The antibodies induced by DNA and yMSP4-His recognized predominantly the C-terminal epidermal growth factor (EGF)-like domain of the protein, whereas EcMSP4-His induced antibodies recognizing all domains of the protein equally. The antibodies induced by DNA vaccination were directed almost extensively to conformational epitopes so that reactivity with native MSP4 was abolished after disulfide bonds in the protein were disrupted. Antibodies induced by recombinant proteins recognized linear epitopes as well and reactivity to native MSP4 was preserved after reduction and alkylation of parasite proteins.

Plasmid vaccine expressing granulocyte-macrophage colony-stimulating factor attracts infiltrates including immature dendritic cells into injected muscles

Plasmid-encoded GM-CSF (pGM-CSF) is an adjuvant for genetic vaccines; however, little is known about how pGM-CSF enhances immunogenicity. We now report that pGM-CSF injected into mouse muscle leads to a local infiltration of potential APCs. Infiltrates reached maximal size on days 3 to 5 after injection and appeared in several large discrete clusters within the muscle. Immunohistological studies in muscle sections from mice injected with pGM-CSF showed staining of cells with the macrophage markers CD11b, Mac-3, IA(d)/E(d) and to the granulocyte marker GR-1 from day 1 through day 14. Cells staining with the dendritic cell marker CD11c were detected only on days 3 to 5. Muscles injected with control plasmids did not stain for CD11c but did stain for CD11b, Mac-3, IA(d)/E(d), and GR-1. No staining was observed with the APC activation markers, B7.1 or CD40, or with markers for T or B cells. These findings are consistent with the infiltrating cells in the pGM-CSF-injected muscles being a mixture of neutrophils, macrophages, and immature dendritic cells and suggest that the i.m. APCs may be enhancing immune responses to coinjected plasmid Ags. This hypothesis is supported by data showing that 1) separation of injections with pGM-CSF and Ag-expressing plasmid into different sites did not enhance immune responses and 2) immune enhancement was associated with the presence of CD11c+ cells in the infiltrates. Thus, pGM-CSF enhancement may depend on APC recruitment to the i.m. site of injection.