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Anne C Teirlinck,
Meta Roestenberg,
Marga van de Vegte-Bolmer,
Anja Scholzen,
Moniek J L Heinrichs,
Rianne Siebelink-Stoter,
Wouter Graumans,
Geert-Jan van Gemert,
Karina Teelen,
Martijn W Vos, [......],
Steffen Borrmann,
Yolanda P A Rozier,
Marianne A A Erkens,
Adrian J F Luty,
Cornelus C Hermsen,
B Kim Lee Sim,
Lisette van Lieshout, Stephen L Hoffman,
Leo G Visser,
Robert W Sauerwein
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ABSTRACT: We established a new field clone of Plasmodium falciparum (Pf) for use in controlled human malaria infections (CHMI) and vaccine studies to complement the current small portfolio of Pf strains, primarily based on NF54. The Cambodian clone NF135.C10 consistently produced gametocytes and generated substantial numbers of sporozoites in Anopheles mosquitoes and diverged from NF54 parasites by genetic markers. In a CHMI trial, three of five volunteers challenged by mosquitoes infected with NF135.C10 and four of five challenged with NF54 developed parasitaemia as detected by microscopy. The two strains induced similar clinical signs and symptoms as well as cellular immunological responses.
The Journal of Infectious Diseases 11/2012; · 6.41 Impact Factor
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Meta Roestenberg,
Else M Bijker,
B Kim Lee Sim,
Peter F Billingsley,
Eric R James,
Guido J H Bastiaens,
Anne C Teirlinck,
Anja Scholzen,
Karina Teelen,
Theo Arens,
André J A M van der Ven,
Anusha Gunasekera,
Sumana Chakravarty,
Soundarapandian Velmurugan,
Cornelus C Hermsen,
Robert W Sauerwein, Stephen L Hoffman
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ABSTRACT: Controlled human malaria infection with sporozoites is a standardized and powerful tool for evaluation of malaria vaccine and drug efficacy but so far only applied by exposure to bites of Plasmodium falciparum (Pf)-infected mosquitoes. We assessed in an open label phase 1 trial, infection after intradermal injection of respectively 2,500, 10,000, or 25,000 aseptic, purified, vialed, cryopreserved Pf sporozoites (PfSPZ) in three groups (N = 6/group) of healthy Dutch volunteers. Infection was safe and parasitemia developed in 15 of 18 volunteers (84%), 5 of 6 volunteers in each group. There were no differences between groups in time until parasitemia by microscopy or quantitative polymerase chain reaction, parasite kinetics, clinical symptoms, or laboratory values. This is the first successful infection by needle and syringe with PfSPZ manufactured in compliance with regulatory standards. After further optimization, the use of such PfSPZ may facilitate and accelerate clinical development of novel malaria drugs and vaccines.
The American journal of tropical medicine and hygiene 11/2012; · 2.59 Impact Factor
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ABSTRACT: Typically, vaccines distributed through the Expanded Program on Immunization (EPI) use a 2-8°C cold chain with 4-5 stops. The PfSPZ vaccine comprises whole live-attenuated cryopreserved sporozoites stored in liquid nitrogen (LN(2)) vapor phase (LNVP) below -140°C and would be distributed through a LNVP cold chain. The purpose of this study was to model LNVP cold chain distribution for the cryopreserved PfSPZ Vaccine in Tanzania, estimate the costs and compare these costs to those that would be incurred in distributing a 'conventional' malaria vaccine through the EPI. Capital and recurrent costs for storage, transportation, labor, energy usage and facilities were determined for the birth cohort in Tanzania over five years. Costs were calculated using WHO/UNESCO calculators. These were applied to a 2-8°C distribution model with national, regional, district, and health facility levels, and for the cryopreserved vaccine using a 'modified hub-and-spoke' (MH-S) LNVP distribution system comprising a central national store, peripheral health facilities and an intermediate district-level transhipment stop. Estimated costs per fully immunized child (FIC) were $ 6.11 for the LNVP-distributed cryopreserved vaccine where the LN(2) is generated, and $ 6.04 with purchased LN(2) (assuming US $ 1.00/L). The FIC costs for distributing a conventional vaccine using the four level 2-8°C cold chain were $ 6.10, and with a tariff distribution system as occurs in Tanzania the FIC cost was $ 5.53. The models, therefore, predicted little difference in 5-year distribution costs between the PfSPZ vaccine distributed through a MH-S LNVP cold chain and a conventional vaccine distributed through the more traditional EPI system. A LNVP cold chain provides additional benefits through the use of durable dry shippers because no refrigerators, freezers or refrigerated trucks are required. Thus strain at the cold chain periphery, vaccine wastage from cold chain failures and the environmental impact of distribution would all be reduced.
Vaccine 11/2012; · 3.77 Impact Factor
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Thomas L Richie,
Yupin Charoenvit,
Ruobing Wang,
Judith E Epstein,
Richard C Hedstrom,
Sanjai Kumar,
Thomas C Luke,
Daniel A Freilich,
Joao C Aguiar,
John B Sacci, [......],
David E Lanar,
Jennifer Ng,
Meng Shi,
Peter M Hobart,
Jon A Norman,
Lorraine A Soisson,
Michael R Hollingdale,
William O Rogers,
Denise L Doolan, Stephen L Hoffman
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ABSTRACT: When introduced in the 1990s, immunization with DNA plasmids was considered potentially revolutionary for vaccine development, particularly for vaccines intended to induce protective CD8 T cell responses against multiple antigens. We conducted, in 1997-1998, the first clinical trial in healthy humans of a DNA vaccine, a single plasmid encoding Plasmodium falciparum circumsporozoite protein (PfCSP), as an initial step toward developing a multi-antigen malaria vaccine targeting the liver stages of the parasite. As the next step, we conducted in 2000-2001 a clinical trial of a five-plasmid mixture called MuStDO5 encoding pre-erythrocytic antigens PfCSP, PfSSP2/TRAP, PfEXP1, PfLSA1 and PfLSA3. Thirty-two, malaria-naïve, adult volunteers were enrolled sequentially into four cohorts receiving a mixture of 500 μg of each plasmid plus escalating doses (0, 20, 100 or 500 μg) of a sixth plasmid encoding human granulocyte macrophage-colony stimulating factor (hGM-CSF). Three doses of each formulation were administered intramuscularly by needle-less jet injection at 0, 4 and 8 weeks, and each cohort had controlled human malaria infection administered by five mosquito bites 18 d later. The vaccine was safe and well-tolerated, inducing moderate antigen-specific, MHC-restricted T cell interferon-γ responses but no antibodies. Although no volunteers were protected, T cell responses were boosted post malaria challenge. This trial demonstrated the MuStDO5 DNA and hGM-CSF plasmids to be safe and modestly immunogenic for T cell responses. It also laid the foundation for priming with DNA plasmids and boosting with recombinant viruses, an approach known for nearly 15 y to enhance the immunogenicity and protective efficacy of DNA vaccines.
Human vaccines & immunotherapeutics. 11/2012; 8(11).
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ABSTRACT: One of the bottlenecks in the development of a whole sporozoite malaria vaccine is the route and method of sporozoite administration. Immunization and challenge of human volunteers by mosquito bites is effective, but cannot be used as a vaccine. Intravenous immunization with sporozoites is effective in rodents and non-human primates, and being studied in humans, but is not yet used for licensed vaccines for infectious diseases. Intradermal and subcutaneous immunization regimens show a strong decrease in protective efficacy, which in rodents, is associated with a decreased degree of parasite liver infection during immunization. The objective of this study was to explore alternative routes of sporozoite administration to increase efficiency of liver infection. Using in vivo imaging, we found that IM injection of sporozoites resulted in a greater parasite liver load compared to ID and SC injection. The use of small inoculation volumes and multiple injections further increased the subsequent liver load. These observations were corroborated in a Plasmodium yoelii model using cryopreserved sporozoites administered ID. Our findings provide a rationale for the design of clinical trials to optimize needle and syringe administration of Plasmodium falciparum sporozoites.
Vaccine 10/2012; · 3.77 Impact Factor
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Takeshi Annoura,
Ivo H J Ploemen,
Ben C L van Schaijk,
Mohammed Sajid,
Martijn W Vos,
Geert-Jan van Gemert,
Severine Chevalley-Maurel,
Blandine M D Franke-Fayard,
Cornelus C Hermsen,
Audrey Gego,
Jean-Francois Franetich,
Dominique Mazier, Stephen L Hoffman,
Chris J Janse,
Robert W Sauerwein,
Shahid M Khan
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ABSTRACT: The critical first step in the clinical development of a malaria vaccine, based on live-attenuated Plasmodium falciparum sporozoites, is the guarantee of complete arrest in the liver. We report on an approach for assessing adequacy of attenuation of genetically attenuated sporozoites in vivo using the Plasmodium berghei model of malaria and P. falciparum sporozoites cultured in primary human hepatocytes. We show that two genetically attenuated sporozoite vaccine candidates, Δp52+p36 and Δfabb/f, are not adequately attenuated. Sporozoites infection of mice with both P. berghei candidates can result in blood infections. We also provide evidence that P. falciparum sporozoites of the leading vaccine candidate that is similarly attenuated through the deletion of the genes encoding the proteins P52 and P36, can develop into replicating liver stages. Therefore, we propose a minimal set of screening criteria to assess adequacy of sporozoite attenuation necessary before advancing into further clinical development and studies in humans.
Vaccine 02/2012; 30(16):2662-70. · 3.77 Impact Factor
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Sophie H Adjalley,
Geoffrey L Johnston,
Tao Li,
Richard T Eastman,
Eric H Ekland,
Abraham G Eappen,
Adam Richman,
B Kim Lee Sim,
Marcus C S Lee, Stephen L Hoffman,
David A Fidock
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ABSTRACT: Clinical studies and mathematical models predict that, to achieve malaria elimination, combination therapies will need to incorporate drugs that block the transmission of Plasmodium falciparum sexual stage parasites to mosquito vectors. Efforts to measure the activity of existing antimalarials on intraerythrocytic sexual stage gametocytes and identify transmission-blocking agents have, until now, been hindered by a lack of quantitative assays. Here, we report an experimental system using P. falciparum lines that stably express gametocyte-specific GFP-luciferase reporters, which enable the assessment of dose- and time-dependent drug action on gametocyte maturation and transmission. These studies reveal activity of the first-line antimalarial dihydroartemisinin and the partner drugs lumefantrine and pyronaridine against early gametocyte stages, along with moderate inhibition of mature gametocyte transmission to Anopheles mosquitoes. The other partner agents monodesethyl-amodiaquine and piperaquine showed activity only against immature gametocytes. Our data also identify methylene blue as a potent inhibitor of gametocyte development across all stages. This thiazine dye almost fully abolishes P. falciparum transmission to mosquitoes at concentrations readily achievable in humans, highlighting the potential of this chemical class to reduce the spread of malaria.
Proceedings of the National Academy of Sciences 11/2011; 108(47):E1214-23. · 9.68 Impact Factor
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Alejandro Jordán-Villegas,
Anilza Bonelo Perdomo,
Judith E Epstein,
Jesús López,
Alejandro Castellanos,
María R Manzano,
Miguel A Hernández,
Liliana Soto,
Fabián Méndez,
Thomas L Richie, Stephen L Hoffman,
Myriam Arévalo-Herrera,
Sócrates Herrera
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ABSTRACT: A non-human primate model for the induction of protective immunity against the pre-erythrocytic stages of Plasmodium vivax malaria using radiation-attenuated P. vivax sporozoites may help to characterize protective immune mechanisms and identify novel malaria vaccine candidates. Immune responses and protective efficacy induced by vaccination with irradiated P. vivax sporozoites were evaluated in malaria-naive Aotus monkeys. Three groups of six monkeys received two, five, or ten intravenous inoculations, respectively, of 100,000 irradiated P. vivax sporozoites; control groups received either 10 doses of uninfected salivary gland extract or no inoculations. Immunization resulted in the production low levels of antibodies that specifically recognized P. vivax sporozoites and the circumsporozoite protein. Additionally, immunization induced low levels of antigen-specific IFN-γ responses. Intravenous challenge with viable sporozoites resulted in partial protection in a dose-dependent manner. These findings suggest that the Aotus monkey model may be able to play a role in preclinical development of P. vivax pre-erythrocytic stage vaccines.
The American journal of tropical medicine and hygiene 02/2011; 84(2 Suppl):43-50. · 2.59 Impact Factor
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ABSTRACT: The malaria parasite Plasmodium falciparum EBA-175 binds its receptor sialic acids on glycophorin A when invading erythrocytes. The receptor-binding region (RII) contains two cysteine-rich domains with similar cysteine motifs (F1 and F2). Functional relationships between F1 and F2 domains and characterization of EBA-175 were studied using specific monoclonal antibodies (mAbs) against these domains.
Five mAbs specific for F1 or F2 were generated. Three mAbs specific for F2 potently blocked binding of EBA-175 to erythrocytes, and merozoite invasion of erythrocytes (IC(50) 10 to 100 µg/ml IgG in growth inhibition assays). A mAb specific for F1 blocked EBA-175 binding and merozoite invasion less effectively. The difference observed between the IC(50) of F1 and F2 mAbs was not due to differing association and disassociation rates as determined by surface plasmon resonance. Four of the mAbs recognized conformation-dependent epitopes within F1 or F2. Used in combination, F1 and F2 mAbs blocked the binding of native EBA-175 to erythrocytes and inhibited parasite invasion synergistically in vitro. MAb R217, the most potent, did not recognize sporozoites, 3-day hepatocyte stage parasites, nor rings, trophozoites, gametocytes, retorts, ookinetes, and oocysts but recognized 6-day hepatocyte stage parasites, and schizonts. Even though efficient at blocking binding to erythrocytes and inhibiting invasion into erythrocytes, MAb R217 did not inhibit sporozoite invasion and development in hepatocytes in vitro.
The role of the F1 and F2 domains in erythrocyte invasion and binding was elucidated with mAbs. These mAbs interfere with native EBA-175 binding to erythrocyte in a synergistic fashion. The stage specific expression of EBA-175 showed that the primary focus of activity was the merozoite stage. A recombinant RII protein vaccine consisting of both F1 and F2 domains that could induce synergistic activity should be optimal for induction of antibody responses that interfere with merozoite invasion of erythrocytes.
PLoS ONE 01/2011; 6(4):e18393. · 4.09 Impact Factor
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Kavita Tewari,
Barbara J Flynn,
Silvia B Boscardin,
Kathrin Kastenmueller,
Andres M Salazar,
Charles A Anderson,
Velmurugan Soundarapandian,
Adriana Ahumada,
Tibor Keler, Stephen L Hoffman,
Michel C Nussenzweig,
Ralph M Steinman,
Robert A Seder
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ABSTRACT: Development of a fully effective vaccine against the pre-erythrocytic stage of malaria infection will likely require induction of both humoral and cellular immune responses. Protein based vaccines can elicit such broad-based immunity depending on the adjuvant and how the protein is formulated. Here to assess these variables, non human primates (NHP) were immunized three times with Plasmodium falciparum (Pf) circumsporozoite protein (CSP) or CSP cloned into MG38, a monoclonal antibody that targets DEC-205 (αDEC-CSP), an endocytic receptor on dendritic cells (DCs). Both vaccines were administered with or without poly(I:C) as adjuvant. Following three immunizations, the magnitude and quality of cytokine secreting CD4+ T cells were comparable between CSP+poly(I:C) and αDEC-CSP+poly(I:C) groups with both regimens eliciting multi-functional cytokine responses. However, NHP immunized with CSP+poly(I:C) had significantly higher serum titers of CSP-specific IgG antibodies and indirect immunofluorescent antibody (IFA) titers against Pf sporozoites. Furthermore, sera from both CSP or αDEC-CSP+poly(I:C) immunized animals limited sporozoite invasion of a hepatocyte cell line (HC04) in vitro. To determine whether CSP-specific responses could be enhanced, all NHP primed with CSP or αDEC-CSP+poly(I:C) were boosted with a single dose of 150,000 irradiated Pf sporozoites (PfSPZ) intravenously. Remarkably, boosting had no effect on the CSP-specific immunity. Finally, immunization with CSP+poly-ICLC reduced malaria parasite burden in the liver in an experimental mouse model. Taken together, these data showing that poly(I:C) is an effective adjuvant for inducing potent antibody and Th1 immunity with CSP based vaccines offers a potential alternative to the existing protein based pre-erythrocytic vaccines.
Vaccine 10/2010; 28(45):7256-66. · 3.77 Impact Factor
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ABSTRACT: The world is experiencing a pandemic of swine-origin influenza virus H1N1. A vaccine to prevent disease is now available, and millions have or will become ill before they can be vaccinated. The ability to use swine-origin influenza virus vaccines as a public health tool has been described as a "race against time." Oseltamivir and related drugs are being used in an effort to reduce morbidity and mortality, but their efficacy for treating severe influenza is suboptimal, and possible wide-spread emergence of oseltamivir-resistant mutants is a concern. Another approach for prevention and treatment of serious influenza is infusion of hyperimmune plasma. The United States has thousands of licensed blood product collection centers that produce millions of liters of plasma licensed by the Food and Drug Administration on an annual basis for the treatment of serious conditions. Immunotherapy using infusion of convalescent plasma (or hyperimmune intravenous immunoglobulin) has been reported to be an effective treatment for severe influenza and other virulent pathogens in animal models and humans. Plasma obtained from those that have recovered or were early recipients of vaccine offers a resource for production of an immediately available and potentially effective therapy at the local, state, and national level. Past, current, and future uses of immunotherapy and current advisory body recommendations for this approach are presented.
Critical care medicine 02/2010; 38(4 Suppl):e66-73. · 6.37 Impact Factor
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ABSTRACT: Plasmodium vivax (Pv) is the second most important human malaria parasite. Recent data indicate that the impact of Pv malaria on the health and economies of the developing world has been dramatically underestimated. Pv has a unique feature in its life cycle. Uninucleate sporozoites (spz), after invasion of human hepatocytes, either proceed to develop into tens of thousands of merozoites within the infected hepatocytes or remain as dormant forms called hypnozoites, which cause relapses of malaria months to several years after the primary infection. Elimination of malaria caused by Pv will be facilitated by developing a safe, highly effective drug that eliminates Pv liver stages, including hypnozoites. Identification and development of such a drug would be facilitated by the development of a medium to high throughput assay for screening drugs against Pv liver stages. We undertook the present pilot study to (1) assess the feasibility of producing large quantities of purified, vialed, cryopreserved Pv sporozoites and (2) establish a system for culturing the liver stages of Pv in order to assess the effects of drugs on the liver stages of Pv. We used primaquine (PQ) to establish this assay model, because PQ is the only licensed drug known to clear all Pv hepatocyte stages, including hypnozoites, and the effect of PQ on Pv hepatocyte stage development in vitro has not previously been reported. We report that we have established the capacity to reproducibly infect hepatoma cells with purified, cyropreserved Pv spz from the same lot, quantitate the primary outcome variable of infected hepatoma cells and demonstrate the inhibitory activity of primaquine on the infected hepatoma cells. We have also identified small parasite forms that may be hypnozoites. These data provide the foundation for finalizing a medium throughput, high content assay to identify new drugs for the elimination of all Pv liver stages.
PLoS ONE 01/2010; 5(12):e14275. · 4.09 Impact Factor
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Scott J Westenberger,
Colleen M McClean,
Rana Chattopadhyay,
Neekesh V Dharia,
Jane M Carlton,
John W Barnwell,
William E Collins, Stephen L Hoffman,
Yingyao Zhou,
Joseph M Vinetz,
Elizabeth A Winzeler
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ABSTRACT: Up to 40% of the world's population is at risk for Plasmodium vivax malaria, a disease that imposes a major public health and economic burden on endemic countries. Because P. vivax produces latent liver forms, eradication of P. vivax malaria is more challenging than it is for P. falciparum. Genetic analysis of P. vivax is exceptionally difficult due to limitations of in vitro culture. To overcome the barriers to traditional molecular biology in P. vivax, we examined parasite transcriptional changes in samples from infected patients and mosquitoes in order to characterize gene function, define regulatory sequences and reveal new potential vaccine candidate genes.
We observed dramatic changes in transcript levels for various genes at different lifecycle stages, indicating that development is partially regulated through modulation of mRNA levels. Our data show that genes involved in common biological processes or molecular machinery are co-expressed. We identified DNA sequence motifs upstream of co-expressed genes that are conserved across Plasmodium species that are likely binding sites of proteins that regulate stage-specific transcription. Despite their capacity to form hypnozoites we found that P. vivax sporozoites show stage-specific expression of the same genes needed for hepatocyte invasion and liver stage development in other Plasmodium species. We show that many of the predicted exported proteins and members of multigene families show highly coordinated transcription as well.
We conclude that high-quality gene expression data can be readily obtained directly from patient samples and that many of the same uncharacterized genes that are upregulated in different P. vivax lifecycle stages are also upregulated in similar stages in other Plasmodium species. We also provide numerous examples of how systems biology is a powerful method for determining the likely function of genes in pathogens that are neglected due to experimental intractability.
PLoS Neglected Tropical Diseases 01/2010; 4(4):e653. · 4.69 Impact Factor
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ABSTRACT: It was recently reported that when mosquitoes infected with P. berghei sporozoites feed on mice, they deposit approximately 100-300 sporozoites in the dermis. When we inoculate P. yoelii (Py) sporozoites intravenously (IV) into BALB/c mice, the 50% infectious dose (ID(50)) is often less than 3 sporozoites, indicating that essentially all Py sporozoites in salivary glands are infectious. Thus, it should only take the bite of one infected mosquito to infect 100% of mice. In human subjects, it takes the bite of at least 5 P. falciparum-infected mosquitoes to achieve 100% blood stage infection. Exposure to 1-2 infected mosquitoes only leads to blood stage infection in approximately 50% of subjects. If mosquitoes carrying Py sporozoites inoculate 100-300 sporozoites per bite, and 1 to 2 mosquito bites achieve 50% blood stage infection rates, then this would suggest that the majority of sporozoites inoculated by mosquitoes into the dermis are not responsible for a productive infection, or that a significant number of sporozoite-infected mosquitoes do not inoculate any sporozoites. The objective of this study was to determine if this is the case. We therefore studied the infectivity to mice of the bites of 1, 2, 4, or 5-8 Py-infected mosquitoes. The bite of one Py sporozoite-infected mosquito caused blood stage infection in 41.4% (12/29) of mice, two bites infected 66.7% (22/33), four bites infected 75% (18/24), and five to eight bites infected 100% (21/21). These findings demonstrate that inoculation of sporozoites by mosquito bite is much less efficient than IV inoculation of Py sporozoites by needle and syringe. Such data may have implications for determining the best route and dose of administration to humans of our attenuated P. falciparum sporozoite vaccine, the scientific basis of which is immunity by bites from irradiated infected mosquitoes, and suggest that the challenge is to develop a method of administration that approximates IV inoculation, not one that mimics mosquito bite.
PLoS ONE 01/2010; 5(1):e8947. · 4.09 Impact Factor
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Kirsten E Lyke,
Matthew Laurens,
Matthew Adams,
Peter F Billingsley,
Adam Richman,
Mark Loyevsky,
Sumana Chakravarty,
Christopher V Plowe,
B Kim Lee Sim,
Robert Edelman, Stephen L Hoffman
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ABSTRACT: Experimental infection of malaria-naïve volunteers by the bite of Plasmodium falciparum-infected mosquitoes is a preferred means to test the protective effect of malaria vaccines and drugs. The standard model relies on the bite of five infected mosquitoes to induce malaria. We examined the efficacy of malaria transmission using mosquitoes raised aseptically in compliance with current Good Manufacturing Practices (cGMPs).
Eighteen adults aged 18-40 years were randomized to receive 1, 3 or 5 bites of Anopheles stephensi mosquitoes infected with the chloroquine-sensitive NF54 strain of P. falciparum. Seventeen participants developed malaria; fourteen occurring on Day 11. The mean prepatent period was 10.9 days (9-12 days). The geometric mean parasitemia was 15.7 parasites/µL (range: 4-70) by microscopy. Polymerase chain reaction (PCR) detected parasites 3.1 (range: 0-4) days prior to microscopy. The geometric mean sporozoite load was 16,753 sporozoites per infected mosquito (range: 1,000-57,500). A 1-bite participant withdrew from the study on Day 13 post-challenge and was PCR and smear negative.
The use of aseptic, cGMP-compliant P. falciparum-infected mosquitoes is safe, is associated with a precise prepatent period compared to the standard model and appears more efficient than the standard approach, as it led to infection in 100% (6/6) of volunteers exposed to three mosquito bites and 83% (5/6) of volunteers exposed to one mosquito bite.
ClinicalTrials.gov NCT00744133.
PLoS ONE 01/2010; 5(10):e13490. · 4.09 Impact Factor
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Amanda Maestre,
Carlos Muskus,
Victoria Duque,
Olga Agudelo,
Pu Liu,
Akihide Takagi,
Francis B Ntumngia,
John H Adams,
Kim Lee Sim, Stephen L Hoffman,
Giampietro Corradin,
Ivan D Velez,
Ruobing Wang
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ABSTRACT: Polymorphism of the Duffy Antigen Receptor for Chemokines (DARC) is associated with susceptibility to and the severity of Plasmodium vivax malaria in humans. P. vivax uses DARC to invade erythrocytes. Individuals lacking DARC are 'resistant' to P. vivax erythrocytic infection. However, susceptibility to P. vivax in DARC+ individuals is reported to vary between specific DARC genotypes. We hypothesized that the natural acquisition of antibodies to P. vivax blood stages may vary with the host genotype and the level of DARC expression. Furthermore, high parasitemia has been reported to effect the acquisition of immunity against pre-erythrocytic parasites. We investigated the correlation between host DARC genotypes and the frequency and magnitude of antibodies against P. vivax erythrocytic stage antigens.
We assessed the frequencies and magnitudes of antibody responses against P. vivax and P. falciparum sporozoite and erythrocytic antigens in Colombian donors from malaria-endemic regions. The frequency and level of naturally-acquired antibodies against the P. vivax erythrocytic antigens merozoite surface protein 1 (PvMSP1) and Duffy binding protein (PvDBP) varied with the host DARC genotypes. Donors with one negative allele (FY*B/FY*Bnull and FY*A/FY*Bnull) were more likely to have anti-PvMSP1 and anti-PvDBP antibodies than those with two positive alleles (FY*B/FY*B and FY*A/FY*B). The lower IgG3 and IgG1 components of the total IgG response may account for the decreased responses to P. vivax erythrocytic antigens with FY*A/FY*B and FY*B/FY*B genotypes. No such association was detected with P. falciparum erythrocytic antigens, which does not use DARC for erythrocyte invasion.
Individuals with higher DARC expression, which is associated with higher susceptibility to P. vivax infection, exhibited low frequencies and magnitudes of P. vivax blood-stage specific antibody responses. This may indicate that one of the primary mechanisms by which P. vivax evades host immunity is through DARC indirectly down-regulating humoral responses against erythrocytic invasion and development.
PLoS ONE 01/2010; 5(7):e11437. · 4.09 Impact Factor
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The Journal of Infectious Diseases 12/2009; 200(11):1646-9. · 6.41 Impact Factor
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ABSTRACT: We have evaluated the effect of mammalian codon optimization on the immunogenicity and protective efficacy of plasmid DNA vaccines encoding pre-erythrocytic stage Plasmodium falciparum and Plasmodium yoelii antigens in mice. Codon optimization significantly enhanced in vitro expression and in vivo antibody responses for P. falciparum circumsporozoite protein (PfCSP) and P. yoelii hepatocyte erythrocyte protein 17 kDa (PyHEP17) but not for P. yoelii circumsporozoite protein (PyCSP). Unexpectedly, more robust CD4+ and CD8+ T cell responses as measured by IFN-gamma ELIspot, lymphoproliferation, and cytotoxic T lymphocyte assays were noted with native as compared with codon optimization constructs. Codon optimization also failed to enhance CD8+ T cell dependent protection against P. yoelii sporozoite challenge as measured by liver-stage parasite burden. These data demonstrate that the effect of mammalian codon optimization is antigen-dependent and may not be beneficial for vaccines designed to induce T cell dependent protective immunity in this malaria model.
Experimental Parasitology 03/2009; 122(2):112-23. · 2.12 Impact Factor
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ABSTRACT: We are developing a radiation attenuated Plasmodium falciparum sporozoite (PfSPZ) malaria vaccine. An important step was to determine the minimum dose of irradiation required to adequately attenuate each sporozoite. This was studied in the Plasmodium yoelii rodent model system. Exposure to 100 Gy completely attenuated P. yoelii sporozoites (PySPZ). Next we demonstrated that immunization of mice intravenously with 3 doses of 750 PySPZ that had received 200 Gy, double the radiation dose required for attenuation, resulted in 100% protection. These results support the contention that a radiation attenuated sporozoite vaccine for malaria will be safe and effective at a range of radiation doses.
Vaccine 01/2009; 27(27):3675-80. · 3.77 Impact Factor
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Jane M Carlton,
John H Adams,
Joana C Silva,
Shelby L Bidwell,
Hernan Lorenzi,
Elisabet Caler,
Jonathan Crabtree,
Samuel V Angiuoli,
Emilio F Merino,
Paolo Amedeo, [......],
Steven L Salzberg,
Christian J Stoeckert,
Steven A Sullivan,
Marcio M Yamamoto, Stephen L Hoffman,
Jennifer R Wortman,
Malcolm J Gardner,
Mary R Galinski,
John W Barnwell,
Claire M Fraser-Liggett
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ABSTRACT: The human malaria parasite Plasmodium vivax is responsible for 25-40% of the approximately 515 million annual cases of malaria worldwide. Although seldom fatal, the parasite elicits severe and incapacitating clinical symptoms and often causes relapses months after a primary infection has cleared. Despite its importance as a major human pathogen, P. vivax is little studied because it cannot be propagated continuously in the laboratory except in non-human primates. We sequenced the genome of P. vivax to shed light on its distinctive biological features, and as a means to drive development of new drugs and vaccines. Here we describe the synteny and isochore structure of P. vivax chromosomes, and show that the parasite resembles other malaria parasites in gene content and metabolic potential, but possesses novel gene families and potential alternative invasion pathways not recognized previously. Completion of the P. vivax genome provides the scientific community with a valuable resource that can be used to advance investigation into this neglected species.
Nature 11/2008; 455(7214):757-63. · 36.28 Impact Factor
