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BACKGROUND: Plasmodium falciparum parasitaemia during pregnancy causes maternal, fetal, and infant mortality. Poor pregnancy outcomes are related to blood-stage parasite sequestration and the ensuing inflammatory response in the placenta, which decreases over successive pregnancies. A radiation-attenuated, non-replicating, whole-organism vaccine based on P falciparum sporozoites (PfSPZ Vaccine) has shown efficacy at preventing infection in African adults. Here, we aimed to examine vaccine safety and efficacy of the PfSPZ Vaccine in adults and women who anticipated conception. METHODS: Two randomised, double-blind, placebo-controlled trials (phase 1 MLSPZV3 and phase 2 MLSPZV4) were conducted at a clinical research centre in Mali. MLSPZV3 included adults aged 18-35 years and MLSPZV4 included non-pregnant women aged 18-38 years who anticipated conception within a year of enrolment. In MLSPZV3, participants were stratified by village and randomly assigned (2:1) using block randomisation to receive three doses of 9â×â105 PfSPZ Vaccine or saline placebo at weeks 0, 1, and 4 (4-week schedule) or at weeks 0, 8, and 16 (16-week schedule) and a booster dose around 1 year later. In MLSPZV4, women received presumptive artemether-lumefantrine twice per day for 3 days 2 weeks before dose one and were randomly assigned (1:1:1) using block randomisation to receive three doses of 9â×â105 or 1·8â×â106 PfSPZ Vaccine or saline placebo all administered at weeks 0, 1, and 4 (4-week schedule). Participants in both studies received artemether-lumefantrine 2 weeks before dose three and additionally 2 weeks before dose four (booster dose) in MLSPZV3. Investigators and participants were masked to group assignment. The primary outcome, assessed in the as-treated population, was PfSPZ Vaccine safety and tolerability within 7 days after each dose. The secondary outcome, assessed in the modified intention-to-treat population, was vaccine efficacy against P falciparum parasitaemia (defined as the time-to-first positive blood smear) from dose three until the end of transmission season. In exploratory analyses, MLSPZV4 evaluated incidence of maternal obstetric and neonatal outcomes as safety outcomes, and vaccine efficacy against P falciparum parasitaemia during pregnancy (defined as time-to-first positive blood smear post-conception). In MLSPZV4, women were followed at least once a month with human chorionic gonadotropin testing, and those who became pregnant received standard of care (including intermittent presumptive sulfadoxine-pyrimethamine antimalarial drugs after the first trimester) during routine antenatal visits. These studies are registered with ClinicalTrials.gov, NCT03510481 and NCT03989102. FINDINGS: Participants were enrolled for vaccination during the onset of malaria seasons for two sequential studies conducted from 2018 to 2019 for MLSPZV3 and from 2019 to 2021 for MLSPZV4, with follow-up during malaria seasons across 2 years. In MLSPZV3, 478 adults were assessed for eligibility, of whom 220 were enrolled between May 30 and June 12, 2018, and then between Aug 13 and Aug 18, 2018, and 210 received dose one. 66 (96%) of 69 participants who received the 16-week schedule and 68 (97%) of 70 who received the 4-week schedule of the 9â×â105 PfSPZ Vaccine and 70 (99%) of 71 who received saline completed all three doses in year 1. In MLSPZV4, 407 women were assessed for eligibility, of whom 324 were enrolled from July 3 to July 27, 2019, and 320 received dose one of presumptive artemether-lumefantrine. 300 women were randomly assigned with 100 per group (PfSPZ Vaccine 9â×â105, 1·8â×â106, or saline) receiving dose one. First trimester miscarriages were the most commonly reported serious adverse event but occurred at a similar rate across study groups (eight [15%] of 54 with 9â×â105 PfSPZ Vaccine, 12 [21%] of 58 with 1·8â×â106 PfSPZ Vaccine, and five [12%] of 43 with saline). One unrelated maternal death occurred 425 days after the last vaccine dose in the 1·8â×â106 PfSPZ Vaccine group due to peritonitis shortly after childbirth. Most related adverse events reported in MLSPZV3 and MLSPZV4 were mild (grade 1) and frequency of adverse events in the PfSPZ Vaccine groups did not differ from that in the saline group. Two unrelated serious adverse events occurred in MLSPZV3 (one participant had appendicitis in the 9â×â105 PfSPZ Vaccine group and the other in the saline group died due to a road traffic accident). In MLSPZV3, the 9â×â105 PfSPZ Vaccine did not show vaccine efficacy against parasitaemia with the 4-week (27% [95% CI -18 to 55] in year 1 and 42% [-5 to 68] in year 2) and 16-week schedules (16% [-34 to 48] in year 1 and -14% [-95 to 33] in year 2); efficacies were similar or worse against clinical malaria compared with saline. In MLSPZV4, the PfSPZ Vaccine showed significant efficacy against parasitaemia at doses 9â×â105 (41% [15 to 59]; p=0·0069 in year 1 and 61% [36 to 77]; p=0·0011 in year 2) and 1·8â×â106 (54% [34 to 69]; p<0·0001 in year 1 and 45% [13 to 65]; p=0·029 in year 2); and against clinical malaria at doses 9â×â105 (47% [20 to 65]; p=0·0045 in year 1 and 56% [22 to 75]; p=0·0081 in year 2) and 1·8â×â106 (48% [22 to 65]; p=0·0013 in year 1 and 40% [2 to 64]; p=0·069 in year 2). Vaccine efficacy against post-conception P falciparum parasitaemia during first pregnancies that arose in the 2-year follow-up was 57% (14 to 78; p=0·017) in the 9 × 105 PfSPZ Vaccine group versus 49% (3 to 73; p=0·042) in the 1·8â×â106 PfSPZ Vaccine group. Among 55 women who became pregnant within 24 weeks after dose three, vaccine efficacy against parasitaemia was 65% (23 to 84; p=0·0088) with the 9â×â105 PfSPZ Vaccine and 86% (64 to 94; p<0·0001) with the 1·8â×â106 PfSPZ Vaccine. When combined in a post-hoc analysis, women in the PfSPZ Vaccine groups had a non-significantly reduced time-to-first pregnancy after dose one compared with those in the saline group (log-rank test p=0·056). Exploratory maternal obstetric and neonatal outcomes did not differ significantly between vaccine groups and saline. INTERPRETATION: PfSPZ Vaccine was safe and well tolerated in adults in Mali. The 9â×â105 and 1·8â×â106 doses of PfSPZ Vaccine administered as per the 4-week schedule, which incorporated presumptive antimalarial treatment before the first vaccine dose, showed significant efficacy against P falciparum parasitaemia and clinical malaria for two malaria transmission seasons in women of childbearing age and against pregnancy malaria. PfSPZ Vaccine without presumptive antimalarial treatment before the first vaccine dose did not show efficacy. FUNDING: National Institute of Allergy and Infectious Diseases, National Institutes of Health, and Sanaria.
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BACKGROUNDSanaria PfSPZ Vaccine, composed of attenuated Plasmodium falciparum (Pf) sporozoites (SPZ), protects against malaria. We conducted this clinical trial to assess the safety and efficacy of PfSPZ Vaccine in HIV-positive (HIV+) individuals, since the HIV-infection status of participants in mass vaccination programs may be unknown.METHODSThis randomized, double-blind, placebo-controlled trial enrolled 18- to 45-year-old HIV-negative (HIV-) and well-controlled HIV+ Tanzanians (HIV viral load <40 copies/mL, CD4 counts >500 cells/µL). Participants received 5 doses of PfSPZ Vaccine or normal saline (NS) over 28 days, followed by controlled human malaria infection (CHMI) 3 weeks later.RESULTSThere were no solicited adverse events in the 9 HIV- and 12 HIV+ participants. After CHMI, 6 of 6 NS controls, 1 of 5 HIV- vaccinees, and 4 of 4 HIV+ vaccinees were Pf positive by quantitative PCR (qPCR). After immunization, anti-Pf circumsporozoite protein (anti-PfCSP) (isotype and IgG subclass) and anti-PfSPZ antibodies, anti-PfSPZ CD4+ T cell responses, and Vδ2+ γδ CD3+ T cells were nonsignificantly higher in HIV- than in HIV+ vaccinees. Sera from HIV- vaccinees had significantly higher inhibition of PfSPZ invasion of hepatocytes in vitro and antibody-dependent complement deposition (ADCD) and Fcγ3B binding by anti-PfCSP and ADCD by anti-cell-traversal protein for ookinetes and SPZ (anti-PfCelTOS) antibodies.CONCLUSIONSPfSPZ Vaccine was safe and well tolerated in HIV+ vaccinees, but not protective. Vaccine efficacy was 80% in HIV- vaccinees (P = 0.012), whose sera had significantly higher inhibition of PfSPZ invasion of hepatocytes and enrichment of multifunctional PfCSP antibodies. A more potent PfSPZ vaccine or regimen is needed to protect those living with HIV against Pf infection in Africa.TRIAL REGISTRATIONClinicalTrials.gov NCT03420053.FUNDINGEquatorial Guinea Malaria Vaccine Initiative (EGMVI), made up of the Government of Equatorial Guinea Ministries of Mines and Hydrocarbons, and Health and Social Welfare, Marathon Equatorial Guinea Production Limited, Noble Energy, Atlantic Methanol Production Company, and EG LNG; Swiss government, through ESKAS scholarship grant no. 2016.0056; Intramural Research Program of the National Institute of Allergy and Infectious Diseases, NIH; NIH grant 1U01AI155354-01.
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Infecções por HIV , Vacinas Antimaláricas , Malária Falciparum , Adolescente , Adulto , Humanos , Pessoa de Meia-Idade , Adulto Jovem , Anticorpos Antiprotozoários , População da África Oriental , Infecções por HIV/complicações , Vacinas Antimaláricas/imunologia , Malária Falciparum/prevenção & controle , Plasmodium falciparum , Tanzânia , Soronegatividade para HIV , Soropositividade para HIV , Eficácia de VacinasRESUMO
Development of next-generation vaccines against Plasmodium falciparum (Pf) is a priority. Many malaria vaccines target the pre-erythrocytic sporozoite (SPZ) and liver stages. These include subunit vaccines based on the Pf circumsporozoite protein (CSP) and attenuated PfSPZ vaccines. However, these strategies require 3-4 doses and have not achieved optimal efficacy against field-transmitted malaria. Prime-and-trap is a recently developed two-step heterologous vaccine strategy that combines priming with DNA encoding CSP followed by a single dose of attenuated SPZ. This strategy aims to induce CD8+ T cells that can eliminate parasites in the liver. Prior data has demonstrated that prime-and-trap with P. yoelii CSP and PySPZ was immunogenic and protective in mice. Here we report preliminary data on the immunogenicity of PfCSP prime and PfSPZ trap vaccine in rhesus macaques. This vaccine induced PfCSP-specific antibodies and T cell responses in all animals. However, response magnitude differed between individuals, suggesting further study is required.
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Vacinas Antimaláricas , Malária Falciparum , Animais , Camundongos , Linfócitos T CD8-Positivos , Macaca mulatta , Plasmodium falciparum , Proteínas de Protozoários/genética , Vacinas Atenuadas , Anticorpos AntiprotozoáriosRESUMO
The radiation-attenuated Plasmodium falciparum sporozoites (PfSPZ) Vaccine has demonstrated safety and immunogenicity in 5-month-old to 50-year-old Africans in multiple trials. Except for one, each trial has restricted enrollment to either infants and children or adults < 50 years old. This trial was conducted in Equatorial Guinea and assessed the safety, tolerability, and immunogenicity of three direct venous inoculations of 1.8 × 106 or 2.7 × 106 PfSPZ, of PfSPZ Vaccine, or normal saline administered at 8-week intervals in a randomized, double-blind, placebo-controlled trial stratified by age (6-11 months and 1-5, 6-10, 11-17, 18-35, and 36-61 years). All doses were successfully administered. In all, 192/207 injections (93%) in those aged 6-61 years were rated as causing no or mild pain. There were no significant differences in solicited adverse events (AEs) between vaccinees and controls in any age group (P ≥ 0.17). There were no significant differences between vaccinees and controls with respect to the rates or severity of unsolicited AEs or laboratory abnormalities. Development of antibodies to P. falciparum circumsporozoite protein occurred in 67/69 vaccinees (97%) and 0/15 controls. Median antibody levels were highest in infants and 1-5-year-olds and declined progressively with age. Antibody responses in children were greater than in adults protected against controlled human malaria infection. Robust immunogenicity, combined with a benign AE profile, indicates children are an ideal target for immunization with PfSPZ Vaccine.
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Vacinas Antimaláricas , Malária Falciparum , Animais , Adulto , Humanos , Criança , Lactente , Pré-Escolar , Pessoa de Meia-Idade , Plasmodium falciparum , Malária Falciparum/prevenção & controle , Esporozoítos , Vacinas Atenuadas , Guiné Equatorial , Método Duplo-Cego , Imunogenicidade da VacinaRESUMO
A highly effective malaria vaccine remains elusive despite decades of research. Plasmodium falciparum sporozoite vaccine (PfSPZ Vaccine), a metabolically active, nonreplicating, whole parasite vaccine demonstrated safety and vaccine efficacy (VE) against endemic P. falciparum for 6 months in Malian adults receiving a five-dose regimen. Safety, immunogenicity, and VE of a three-dose regimen were assessed in adults in Balonghin, Burkina Faso in a two-component study: an open-label dose escalation trial with 32 participants followed by a double-blind, randomized, placebo-controlled trial (RCT) with 80 participants randomized to receive three doses of 2.7 × 106 PfSPZ (N = 39) or normal saline (N = 41) just before malaria season. To clear parasitemia, artesunate monotherapy was administered before first and last vaccinations. Thick blood smear microscopy was performed on samples collected during illness and every 4 weeks for 72 weeks after last vaccinations, including two 6-month malaria transmission seasons. Safety outcomes were assessed in all 80 participants who received at least one dose and VE for 79 participants who received three vaccinations. Myalgia was the only symptom that differed between groups. VE (1 - risk ratio; primary VE endpoint) was 38% at 6 months (P = 0.017) and 15% at 18 months (0.078). VE (1 - hazard ratio) was 48% and 46% at 6 and 18 months (P = 0.061 and 0.018). Two weeks after the last dose, antibodies to P. falciparum circumsporozoite protein and PfSPZ were higher in protected versus unprotected vaccinees. A three-dose regimen of PfSPZ Vaccine demonstrated safety and efficacy against malaria infection in malaria-experienced adults.
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Esporozoítos , Vacinas , Humanos , AnimaisRESUMO
An effective vaccine is needed for the prevention and elimination of malaria. The only immunogens that have been shown to have a protective efficacy of more than 90% against human malaria are Plasmodium falciparum (Pf) sporozoites (PfSPZ) manufactured in mosquitoes (mPfSPZ)1-7. The ability to produce PfSPZ in vitro (iPfSPZ) without mosquitoes would substantially enhance the production of PfSPZ vaccines and mosquito-stage malaria research, but this ability is lacking. Here we report the production of hundreds of millions of iPfSPZ. iPfSPZ invaded human hepatocytes in culture and developed to mature liver-stage schizonts expressing P. falciparum merozoite surface protein 1 (PfMSP1) in numbers comparable to mPfSPZ. When injected into FRGhuHep mice containing humanized livers, iPfSPZ invaded the human hepatocytes and developed to PfMSP1-expressing late liver stage parasites at 45% the quantity of cryopreserved mPfSPZ. Human blood from FRGhuHep mice infected with iPfSPZ produced asexual and sexual erythrocytic-stage parasites in culture, and gametocytes developed to PfSPZ when fed to mosquitoes, completing the P. falciparum life cycle from infectious gametocyte to infectious gametocyte without mosquitoes or primates.
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Plasmodium falciparum , Esporozoítos , Animais , Humanos , Camundongos , Culicidae/parasitologia , Malária/parasitologia , Malária/prevenção & controle , Vacinas Antimaláricas/biossíntese , Vacinas Antimaláricas/química , Malária Falciparum/parasitologia , Plasmodium falciparum/crescimento & desenvolvimento , Esporozoítos/crescimento & desenvolvimento , Esporozoítos/patogenicidade , Hepatócitos/parasitologia , Fígado/parasitologia , Proteína 1 de Superfície de Merozoito , Eritrócitos/parasitologia , Técnicas In VitroRESUMO
Background: While prior research has shown differences in the risk of malaria infection and sickness between males and females, little is known about sex differences in vaccine-induced immunity to malaria. Identifying such differences could elucidate important aspects of malaria biology and facilitate development of improved approaches to malaria vaccination. Methods: Using a standardized enzyme-linked immunosorbent assay, IgG antibodies to the major surface protein on Plasmodium falciparum (Pf) sporozoites (SPZ), the Pf circumsporozoite protein (PfCSP), were measured before and two weeks after administration of a PfSPZ-based malaria vaccine (PfSPZ Vaccine) to 5-month to 61-year-olds in 11 clinical trials in Germany, the US and five countries in Africa, to determine if there were differences in vaccine elicited antibody response between males and females and if these differences were associated with differential protection against naturally transmitted Pf malaria (Africa) or controlled human malaria infection (Germany, the US and Africa). Results: Females ≥ 11 years of age made significantly higher levels of antibodies to PfCSP than did males in most trials, while there was no indication of such differences in infants or children. Although adult females had higher levels of antibodies, there was no evidence of improved protection compared to males. In 2 of the 7 trials with sufficient data, protected males had significantly higher levels of antibodies than unprotected males, and in 3 other trials protected females had higher levels of antibodies than did unprotected females. Conclusion: Immunization with PfSPZ Vaccine induced higher levels of antibodies in post-pubertal females but showed equivalent protection in males and females. We conclude that the increased antibody levels in post-pubertal females did not contribute substantially to improved protection. We hypothesize that while antibodies to PfCSP (and PfSPZ) may potentially contribute directly to protection, they primarily correlate with other, potentially protective immune mechanisms, such as antibody dependent and antibody independent cellular responses in the liver.
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Vacinas Antimaláricas , Malária Falciparum , Malária , Adulto , Criança , Lactente , Animais , Feminino , Humanos , Masculino , Malária Falciparum/prevenção & controle , Plasmodium falciparum , Esporozoítos , Malária/tratamento farmacológicoRESUMO
BACKGROUND: Plasmodium falciparum (Pf) sporozoite (SPZ) vaccines are the only candidate malaria vaccines that induce > 90% vaccine efficacy (VE) against controlled human malaria infection and the only malaria vaccines to have achieved reproducible VE against malaria in adults in Africa. The goal is to increase the impact and reduce the cost of PfSPZ vaccines by optimizing vaccine potency and manufacturing, which will benefit from identification of immunological responses contributing to protection in humans. Currently, there is no authentic animal challenge model for assessing P. falciparum malaria VE. Alternatively, Plasmodium knowlesi (Pk), which infects humans and non-human primates (NHPs) in nature, can be used to experimentally infect rhesus macaques (Macaca mulatta) to assess VE. METHODS: Sanaria has, therefore, produced purified, vialed, cryopreserved PkSPZ and conducted challenge studies in several naïve NHP cohorts. In the first cohort, groups of three rhesus macaques each received doses of 5 × 102, 2.5 × 103, 1.25 × 104 and 2.5 × 104 PkSPZ administered by direct venous inoculation. The infectivity of 1.5 × 103 PkSPZ cryopreserved with an altered method and of 1.5 × 103 PkSPZ cryopreserved for four years was tested in a second and third cohort of rhesus NHPs. The lastly, three pig-tailed macaques (Macaca nemestrina), a natural P. knowlesi host, were challenged with 2.5 × 103 PkSPZ cryopreserved six years earlier. RESULTS: In the first cohort, all 12 animals developed P. knowlesi parasitaemia by thick blood smear, and the time to positivity (prepatent period) followed a non-linear 4-parameter logistic sigmoidal model with a median of 11, 10, 8, and 7 days, respectively (r2 = 1). PkSPZ cryopreserved using a modified rapid-scalable method infected rhesus with a pre-patent period of 10 days, as did PkSPZ cryopreserved four years prior to infection, similar to the control group. Cryopreserved PkSPZ infected pig-tailed macaques with median time to positivity by thin smear, of 11 days. CONCLUSION: This study establishes the capacity to consistently infect NHPs with purified, vialed, cryopreserved PkSPZ, providing a foundation for future studies to probe protective immunological mechanisms elicited by PfSPZ vaccines that cannot be established in humans.
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Vacinas Antimaláricas , Malária Falciparum , Malária , Plasmodium knowlesi , Adulto , Animais , Humanos , Macaca mulatta , Plasmodium falciparum , EsporozoítosRESUMO
Immunization with radiation-attenuated Plasmodium falciparum (Pf) sporozoites (SPZ) in PfSPZ Vaccine, has provided better vaccine efficacy (VE) against controlled human malaria infection (CHMI) with the same parasites as in the vaccine (homologous) than with genetically distant parasites (heterologous). We sought to identify an immunization regimen that provided similar VE against CHMI with homologous and heterologous Pf for at least 9 weeks in malaria-naïve adults. Such a regimen was identified in part 1 (optimization), an open label study, and confirmed in part 2 (verification), a randomized, double-blind, placebo-controlled study in which VE was assessed by cross-over repeat CHMI with homologous (PfNF54) and heterologous (Pf7G8) PfSPZ at 3 and 9-10 weeks. VE was calculated using Bayesian generalized linear regression. In part 1, vaccination with 9 × 105 PfSPZ on days 1, 8, and 29 protected 5/5 (100%) subjects against homologous CHMI at 3 weeks after the last immunization. In part 2, the same 3-dose regimen protected 5/6 subjects (83%) against heterologous CHMI at both 3 and 9-10 weeks after the last immunization. Overall VE was 78% (95% predictive interval: 57-92%), and against heterologous and homologous was 79% (95% PI: 54-95%) and 77% (95% PI: 50-95%) respectively. PfSPZ Vaccine was safe and well tolerated. A 4-week, 3-dose regimen of PfSPZ Vaccine provided similar VE for 9-10 weeks against homologous and heterologous CHMI. The trial is registered with ClinicalTrials.gov, NCT02704533.
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Background: Plasmodium falciparum (Pf) Sporozoite (SPZ) Chemoprophylaxis Vaccine (PfSPZ-CVac) involves concurrently administering infectious PfSPZ and malaria drug, often chloroquine (CQ), to kill liver-emerging parasites. PfSPZ-CVac (CQ) protected 100% of malaria-naïve participants against controlled human malaria infection. We investigated the hypothesis that PfSPZ-CVac (CQ) is safe and efficacious against seasonal, endemic Pf in malaria-exposed adults. Methods: Healthy 18-45 year olds were enrolled in a double-blind, placebo-controlled trial in Bougoula-Hameau, Mali, randomized 1:1 to 2.048 × 105 PfSPZ (PfSPZ Challenge) or normal saline administered by direct venous inoculation at 0, 4, 8 weeks. Syringes were prepared by pharmacy staff using online computer-based enrolment that randomized allocations. Clinical team and participant masking was assured by identical appearance of vaccine and placebo. Participants received chloroquine 600mg before first vaccination, 10 weekly 300mg doses during vaccination, then seven daily doses of artesunate 200mg before 24-week surveillance during the rainy season. Safety outcomes were solicited adverse events (AEs) and related unsolicited AEs within 12 days of injections, and all serious AEs. Pf infection was detected by thick blood smears performed every four weeks and during febrile illness over 48 weeks. Primary vaccine efficacy (VE) endpoint was time to infection at 24 weeks. NCT02996695. Findings: 62 participants were enrolled in April/May 2017. Proportions of participants experiencing at least one solicited systemic AE were similar between treatment arms: 6/31 (19.4%, 95%CI 9.2-36.3) of PfSPZ-CVac recipients versus 7/31 (22.6%, 95%CI 29.2-62.2) of controls (p value = 1.000). Two/31 (6%) in each group reported related, unsolicited AEs. One unrelated death occurred. Of 59 receiving 3 immunizations per protocol, fewer vaccinees (16/29, 55.2%) became infected than controls (22/30, 73.3%). VE was 33.6% by hazard ratio (p = 0.21, 95%CI -27·9, 65·5) and 24.8% by risk ratio (p = 0.10, 95%CI -4·8, 54·3). Antibody responses to PfCSP were poor; 28% of vaccinees sero-converted. Interpretation: PfSPZ-CVac (CQ) was well-tolerated. The tested dosing regimen failed to significantly protect against Pf infection in this very high transmission setting. Funding: U.S. National Institutes of Health, Sanaria. Registration number: ClinicalTrials.gov identifier (NCT number): NCT02996695.
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BACKGROUND: WHO recently approved a partially effective vaccine that reduces clinical malaria in children, but increased vaccine activity is required to pursue malaria elimination. A phase 1 clinical trial was done in Mali, west Africa, to assess the safety, immunogenicity, and protective efficacy of a three-dose regimen of Plasmodium falciparum sporozoite (PfSPZ) Vaccine (a metabolically active, non-replicating, whole malaria sporozoite vaccine) against homologous controlled human malaria infection (CHMI) and natural P falciparum infection. METHODS: We recruited healthy non-pregnant adults aged 18-50 years in Donéguébougou, Mali, and surrounding villages (Banambani, Toubana, Torodo, Sirababougou, Zorokoro) for an open-label, dose-escalation pilot study and, thereafter, a randomised, double-blind, placebo-controlled main trial. Pilot study participants were enrolled on an as-available basis to one group of CHMI infectivity controls and three staggered vaccine groups receiving: one dose of 4·5 × 105, one dose of 9 × 105, or three doses of 1·8 × 106 PfSPZ via direct venous inoculation at approximately 8 week intervals, followed by homologous CHMI 5 weeks later with infectious PfSPZ by direct venous inoculation (PfSPZ Challenge). Main cohort participants were stratified by village and randomly assigned (1:1) to receive three doses of 1·8 × 106 PfSPZ or normal saline at 1, 13, and 19 week intervals using permuted block design by the study statistician. The primary outcome was safety and tolerability of at least one vaccine dose; the secondary outcome was vaccine efficacy against homologous PfSPZ CHMI (pilot study) or against naturally transmitted P falciparum infection (main study) measured by thick blood smear. Combined artesunate and amodiaquine was administered to eliminate pre-existing parasitaemia. Outcomes were analysed by modified intention to treat (mITT; including all participants who received at least one dose of investigational product; safety and vaccine efficacy) and per protocol (vaccine efficacy). This trial is registered with ClinicalTrials.gov, number NCT02627456. FINDINGS: Between Dec 20, 2015, and April 30, 2016, we enrolled 56 participants into the pilot study (five received the 4·5 × 105 dose, five received 9 × 105, 30 received 1·8 × 106, 15 were CHMI controls, and one withdrew before vaccination) and 120 participants into the main study cohort with 60 participants assigned PfSPZ Vaccine and 60 placebo in the main study. Adverse events and laboratory abnormalities post-vaccination in all dosing groups were few, mainly mild, and did not differ significantly between vaccine groups (all p>0·05). Unexpected severe transaminitis occured in four participants: one participant in pilot phase that received 1·8 × 106 PfSPZ Vaccine, one participant in main phase that received 1·8 × 106 PfSPZ Vaccine, and two participants in the main phase placebo group. During PfSPZ CHMI, approximately 5 weeks after the third dose of 1·8 × 106 PfSPZ, none of 29 vaccinees and one of 15 controls became positive on thick blood smear; subsequent post-hoc PCR analysis for submicroscopic blood stage infections detected P falciparum parasites in none of the 29 vaccine recipients and eight of 15 controls during CHMI. In the main trial, 32 (58%) of 55 vaccine recipients and 42 (78%) of 54 controls became positive on thick blood smear during 24-week surveillance after vaccination. Vaccine efficacy (1-hazard ratio) was 0·51 per protocol (95% CI 0·20-0·70; log-rank p=0·0042) and 0·39 by mITT (0·04-0·62; p=0·033); vaccine efficacy (1-risk ratio) was 0·24 per-protocol (0·02-0·41; p=0·031) and 0·22 mITT (0·01-0·39; p=0·041). INTERPRETATION: A three-dose regimen of PfSPZ Vaccine was safe, well tolerated, and conferred 51% vaccine efficacy against intense natural P falciparum transmission, similar to 52% vaccine efficacy reported for a five-dose regimen in a previous trial. FUNDING: US National Institute of Allergy and Infectious Diseases, National Institutes of Health, Sanaria. TRANSLATION: For the French translation of the abstract see Supplementary Materials section.
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Vacinas Antimaláricas , Malária Falciparum , Malária , Adolescente , Adulto , Animais , Criança , Método Duplo-Cego , Humanos , Malária/tratamento farmacológico , Malária Falciparum/tratamento farmacológico , Mali , Pessoa de Meia-Idade , Projetos Piloto , Plasmodium falciparum , Estações do Ano , Esporozoítos , Adulto JovemRESUMO
The radiation-attenuated Plasmodium falciparum sporozoite (PfSPZ) vaccine provides protection against P. falciparum infection in malaria-naïve adults. Preclinical studies show that T cell-mediated immunity is required for protection and is readily induced in humans after vaccination. However, previous malaria exposure can limit immune responses and vaccine efficacy (VE) in adults. We hypothesized that infants with less previous exposure to malaria would have improved immunity and protection. We conducted a multi-arm, randomized, double-blind, placebo-controlled trial in 336 infants aged 5-12 months to determine the safety, tolerability, immunogenicity and efficacy of the PfSPZ Vaccine in infants in a high-transmission malaria setting in western Kenya ( NCT02687373 ). Groups of 84 infants each received 4.5 × 105, 9.0 × 105 or 1.8 × 106 PfSPZ Vaccine or saline three times at 8-week intervals. The vaccine was well tolerated; 52 (20.6%) children in the vaccine groups and 20 (23.8%) in the placebo group experienced related solicited adverse events (AEs) within 28 d postvaccination and most were mild. There was 1 grade 3-related solicited AE in the vaccine group (0.4%) and 2 in the placebo group (2.4%). Seizures were more common in the highest-dose group (14.3%) compared to 6.0% of controls, with most being attributed to malaria. There was no significant protection against P. falciparum infection in any dose group at 6 months (VE in the 9.0 × 105 dose group = -6.5%, P = 0.598, the primary statistical end point of the study). VE against clinical malaria 3 months after the last dose in the highest-dose group was 45.8% (P = 0.027), an exploratory end point. There was a dose-dependent increase in antibody responses that correlated with VE at 6 months in the lowest- and highest-dose groups. T cell responses were undetectable across all dose groups. Detection of Vδ2+Vγ9+ T cells, which have been correlated with induction of PfSPZ Vaccine T cell immunity and protection in adults, were infrequent. These data suggest that PfSPZ Vaccine-induced T cell immunity is age-dependent and may be influenced by Vδ2+Vγ9+ T cell frequency. Since there was no significant VE at 6 months in these infants, these vaccine regimens will likely not be pursued further in this age group.
Assuntos
Vacinas Antimaláricas/administração & dosagem , Malária Falciparum/tratamento farmacológico , Plasmodium falciparum/efeitos dos fármacos , Vacinas Atenuadas/administração & dosagem , Adulto , Formação de Anticorpos/efeitos dos fármacos , Formação de Anticorpos/imunologia , Linfócitos B/efeitos dos fármacos , Linfócitos B/imunologia , Método Duplo-Cego , Humanos , Lactente , Quênia/epidemiologia , Vacinas Antimaláricas/efeitos adversos , Malária Falciparum/imunologia , Malária Falciparum/parasitologia , Malária Falciparum/prevenção & controle , Plasmodium falciparum/patogenicidade , Esporozoítos/efeitos dos fármacos , Esporozoítos/patogenicidade , Linfócitos T/efeitos dos fármacos , Vacinação , Vacinas Atenuadas/efeitos adversosRESUMO
The global decline in malaria has stalled1, emphasizing the need for vaccines that induce durable sterilizing immunity. Here we optimized regimens for chemoprophylaxis vaccination (CVac), for which aseptic, purified, cryopreserved, infectious Plasmodium falciparum sporozoites (PfSPZ) were inoculated under prophylactic cover with pyrimethamine (PYR) (Sanaria PfSPZ-CVac(PYR)) or chloroquine (CQ) (PfSPZ-CVac(CQ))-which kill liver-stage and blood-stage parasites, respectively-and we assessed vaccine efficacy against homologous (that is, the same strain as the vaccine) and heterologous (a different strain) controlled human malaria infection (CHMI) three months after immunization ( https://clinicaltrials.gov/ , NCT02511054 and NCT03083847). We report that a fourfold increase in the dose of PfSPZ-CVac(PYR) from 5.12 × 104 to 2 × 105 PfSPZs transformed a minimal vaccine efficacy (low dose, two out of nine (22.2%) participants protected against homologous CHMI), to a high-level vaccine efficacy with seven out of eight (87.5%) individuals protected against homologous and seven out of nine (77.8%) protected against heterologous CHMI. Increased protection was associated with Vδ2 γδ T cell and antibody responses. At the higher dose, PfSPZ-CVac(CQ) protected six out of six (100%) participants against heterologous CHMI three months after immunization. All homologous (four out of four) and heterologous (eight out of eight) infectivity control participants showed parasitaemia. PfSPZ-CVac(CQ) and PfSPZ-CVac(PYR) induced a durable, sterile vaccine efficacy against a heterologous South American strain of P. falciparum, which has a genome and predicted CD8 T cell immunome that differs more strongly from the African vaccine strain than other analysed African P. falciparum strains.
Assuntos
Anticorpos Neutralizantes/imunologia , Fígado/imunologia , Fígado/parasitologia , Vacinas Antimaláricas/imunologia , Plasmodium falciparum/efeitos dos fármacos , Plasmodium falciparum/imunologia , Vacinas Atenuadas/imunologia , Adulto , Animais , Formação de Anticorpos/imunologia , Ensaio de Imunoadsorção Enzimática , Feminino , Humanos , Imunoglobulina G/sangue , Imunoglobulina G/imunologia , Estágios do Ciclo de Vida/imunologia , Malária/sangue , Malária/imunologia , Malária/parasitologia , Malária/prevenção & controle , Vacinas Antimaláricas/administração & dosagem , Vacinas Antimaláricas/efeitos adversos , Vacinas Antimaláricas/química , Masculino , Pessoa de Meia-Idade , Plasmodium falciparum/crescimento & desenvolvimento , Linfócitos T/citologia , Linfócitos T/imunologia , Linfócitos T/metabolismo , Fatores de Tempo , Vacinação/efeitos adversos , Vacinas Atenuadas/administração & dosagem , Vacinas Atenuadas/efeitos adversos , Vacinas Atenuadas/químicaRESUMO
Immunization with Plasmodium falciparum (Pf) sporozoites under chemoprophylaxis (PfSPZ-CVac) is the most efficacious approach to malaria vaccination. Implementation is hampered by a complex chemoprophylaxis regimen and missing evidence for efficacy against heterologous infection. We report the results of a double-blinded, randomized, placebo-controlled trial of a simplified, condensed immunization regimen in malaria-naive volunteers (EudraCT-Nr: 2018-004523-36). Participants are immunized by direct venous inoculation of 1.1 × 105 aseptic, purified, cryopreserved PfSPZ (PfSPZ Challenge) of the PfNF54 strain or normal saline (placebo) on days 1, 6 and 29, with simultaneous oral administration of 10 mg/kg chloroquine base. Primary endpoints are vaccine efficacy tested by controlled human malaria infection (CHMI) using the highly divergent, heterologous strain Pf7G8 and safety. Twelve weeks following immunization, 10/13 participants in the vaccine group are sterilely protected against heterologous CHMI, while (5/5) participants receiving placebo develop parasitemia (risk difference: 77%, p = 0.004, Boschloo's test). Immunization is well tolerated with self-limiting grade 1-2 headaches, pyrexia and fatigue that diminish with each vaccination. Immunization induces 18-fold higher anti-Pf circumsporozoite protein (PfCSP) antibody levels in protected than in unprotected vaccinees (p = 0.028). In addition anti-PfMSP2 antibodies are strongly protection-associated by protein microarray assessment. This PfSPZ-CVac regimen is highly efficacious, simple, safe, well tolerated and highly immunogenic.
Assuntos
Vacinas Antimaláricas/imunologia , Malária Falciparum/prevenção & controle , Plasmodium falciparum/imunologia , Vacinação/métodos , Vacinas Atenuadas/imunologia , Adulto , Antimaláricos/uso terapêutico , Linhagem Celular , Quimioprevenção , Cloroquina/uso terapêutico , Feminino , Humanos , Imunoglobulina G/imunologia , Vacinas Antimaláricas/efeitos adversos , Malária Falciparum/tratamento farmacológico , Malária Falciparum/imunologia , Malária Falciparum/parasitologia , Masculino , Parasitemia/imunologia , Análise Serial de Proteínas , Esporozoítos/imunologia , Vacinação/efeitos adversos , Vacinas Atenuadas/efeitos adversosRESUMO
PfSPZ-CVac combines 'PfSPZ Challenge', which consists of infectious Plasmodium falciparum sporozoites (PfSPZ), with concurrent antimalarial chemoprophylaxis. In a previously-published PfSPZ-CVac study, three doses of 5.12x104 PfSPZ-CVac given 28 days apart had 100% vaccine efficacy (VE) against controlled human malaria infection (CHMI) 10 weeks after the last immunization, while the same dose given as three injections five days apart had 63% VE. Here, we conducted a dose escalation trial of similarly condensed schedules. Of the groups proceeding to CHMI, the first study group received three direct venous inoculations (DVIs) of a dose of 5.12x104 PfSPZ-CVac seven days apart and the next full dose group received three DVIs of a higher dose of 1.024x105 PfSPZ-CVac five days apart. CHMI (3.2x103 PfSPZ Challenge) was performed by DVI 10 weeks after the last vaccination. In both CHMI groups, transient parasitemia occurred starting seven days after each vaccination. For the seven-day interval group, the second and third vaccinations were therefore administered coincident with parasitemia from the prior vaccination. Parasitemia was associated with systemic symptoms which were severe in 25% of subjects. VE in the seven-day group was 0% (7/7 infected) and in the higher-dose, five-day group was 75% (2/8 infected). Thus, the same dose of PfSPZ-CVac previously associated with 63% VE when given on a five-day schedule in the prior study had zero VE here when given on a seven-day schedule, while a double dose given on a five-day schedule here achieved 75% VE. The relative contributions of the five-day schedule and/or the higher dose to improved VE warrant further investigation. It is notable that administration of PfSPZ-CVac on a schedule where vaccine administration coincided with blood-stage parasitemia was associated with an absence of sterile protective immunity. Clinical trials registration: NCT02773979.
Assuntos
Antimaláricos/administração & dosagem , Vacinas Antimaláricas/imunologia , Malária Falciparum/prevenção & controle , Plasmodium falciparum/imunologia , Vacinação , Adulto , Eritrócitos/imunologia , Feminino , Humanos , Imunogenicidade da Vacina , Vacinas Antimaláricas/administração & dosagem , Malária Falciparum/parasitologia , Pessoa de Meia-Idade , Parasitemia , Esporozoítos , Adulto JovemRESUMO
The diversity of circulating human B cells is unknown. We use single-cell RNA sequencing (RNA-seq) to examine the diversity of both antigen-specific and total B cells in healthy subjects and malaria-exposed individuals. This reveals two B cell lineages: a classical lineage of activated and resting memory B cells and an alternative lineage, which includes previously described atypical B cells. Although atypical B cells have previously been associated with disease states, the alternative lineage is common in healthy controls, as well as malaria-exposed individuals. We further track Plasmodium-specific B cells after malaria vaccination in naive volunteers. We find that alternative lineage cells are primed after the initial immunization and respond to booster doses. However, alternative lineage cells develop an atypical phenotype with repeated boosts. The data highlight that atypical cells are part of a wider alternative lineage of B cells that are a normal component of healthy immune responses.
Assuntos
Anticorpos Antiprotozoários/imunologia , Linfócitos B/imunologia , Vacinas Antimaláricas/administração & dosagem , Malária/imunologia , Plasmodium/imunologia , Vacinação , Adulto , Criança , Pré-Escolar , Feminino , Humanos , Malária/prevenção & controle , Vacinas Antimaláricas/imunologia , Masculino , RNA-SeqRESUMO
Plasmodium falciparum sporozoite (PfSPZ) Vaccine (radiation-attenuated, aseptic, purified, cryopreserved PfSPZ) and PfSPZ-CVac (infectious, aseptic, purified, cryopreserved PfSPZ administered to subjects taking weekly chloroquine chemoprophylaxis) have shown vaccine efficacies (VEs) of 100% against homologous controlled human malaria infection (CHMI) in nonimmune adults. Plasmodium falciparum sporozoite-CVac has never been assessed against CHMI in African vaccinees. We assessed the safety, immunogenicity, and VE against homologous CHMI of three doses of 2.7 × 106 PfSPZ of PfSPZ Vaccine at 8-week intervals and three doses of 1.0 × 105 PfSPZ of PfSPZ-CVac at 4-week intervals with each arm randomized, double-blind, placebo-controlled, and conducted in parallel. There were no differences in solicited adverse events between vaccinees and normal saline controls, or between PfSPZ Vaccine and PfSPZ-CVac recipients during the 6 days after administration of investigational product. However, from days 7-13, PfSPZ-CVac recipients had significantly more AEs, probably because of Pf parasitemia. Antibody responses were 2.9 times higher in PfSPZ Vaccine recipients than PfSPZ-CVac recipients at time of CHMI. Vaccine efficacy at a median of 14 weeks after last PfSPZ-CVac dose was 55% (8 of 13, P = 0.051) and at a median of 15 weeks after last PfSPZ Vaccine dose was 27% (5 of 15, P = 0.32). The higher VE in PfSPZ-CVac recipients of 55% with a 27-fold lower dose was likely a result of later stage parasite maturation in the liver, leading to induction of cellular immunity against a greater quantity and broader array of antigens.
Assuntos
Imunogenicidade da Vacina , Vacinas Antimaláricas/imunologia , Malária Falciparum/prevenção & controle , Plasmodium falciparum/imunologia , Adolescente , Adulto , Idoso , Animais , Anticorpos Antiprotozoários , Antimaláricos/uso terapêutico , Criança , Pré-Escolar , Cloroquina/uso terapêutico , Método Duplo-Cego , Guiné Equatorial/epidemiologia , Feminino , Humanos , Imunização , Lactente , Vacinas Antimaláricas/efeitos adversos , Masculino , Pessoa de Meia-Idade , Parasitemia , Vacinas Atenuadas/efeitos adversos , Vacinas Atenuadas/imunologia , Adulto JovemRESUMO
Generating sufficient antibody to block infection is a key challenge for vaccines against malaria. Here, we show that antibody titers to a key target, the repeat region of the Plasmodium falciparum circumsporozoite protein (PfCSP), plateaued after two immunizations in a clinical trial of the radiation-attenuated sporozoite vaccine. To understand the mechanisms limiting vaccine responsiveness, we developed immunoglobulin (Ig)-knockin mice with elevated numbers of PfCSP-binding B cells. We determined that recall responses were inhibited by antibody feedback, potentially via epitope masking of the immunodominant PfCSP repeat region. Importantly, the amount of antibody that prevents boosting is below the amount of antibody required for protection. Finally, while antibody feedback limited responses to the PfCSP repeat region in vaccinated volunteers, potentially protective subdominant responses to PfCSP C-terminal regions expanded with subsequent boosts. These data suggest that antibody feedback drives the diversification of immune responses and that vaccination for malaria will require targeting multiple antigens.
Assuntos
Anticorpos Antiprotozoários/imunologia , Linfócitos B/imunologia , Vacinas Antimaláricas/imunologia , Vacinação , Animais , Anticorpos Antiprotozoários/genética , Formação de Anticorpos/imunologia , Epitopos/imunologia , Retroalimentação , Humanos , Imunização , Imunoglobulina G , Imunoglobulina M , Malária/imunologia , Camundongos , Camundongos Endogâmicos C57BL , Mutação , Plasmodium falciparum/imunologia , Esporozoítos/imunologia , Vacinas AtenuadasRESUMO
BACKGROUND: A vaccine would be an ideal tool for reducing malaria's impact. PfSPZ Vaccine (radiation attenuated, aseptic, purified, cryopreserved Plasmodium falciparum [Pf] sporozoites [SPZ]) has been well tolerated and safe in >1526 malaria-naive and experienced 6-month to 65-year-olds in the United States, Europe, and Africa. When vaccine efficacy (VE) of 5 doses of 2.7 × 105 PfSPZ of PfSPZ Vaccine was assessed in adults against controlled human malaria infection (CHMI) in the United States and Tanzania and intense field transmission of heterogeneous Pf in Mali, Tanzanians had the lowest VE (20%). METHODS: To increase VE in Tanzania, we increased PfSPZ/dose (9 × 105 or 1.8 × 106) and decreased numbers of doses to 3 at 8-week intervals in a double blind, placebo-controlled trial. RESULTS: All 22 CHMIs in controls resulted in parasitemia by quantitative polymerase chain reaction. For the 9 × 105 PfSPZ group, VE was 100% (5/5) at 3 or 11 weeks (P < .000l, Barnard test, 2-tailed). For 1.8 × 106 PfSPZ, VE was 33% (2/6) at 7.5 weeks (P = .028). VE of dosage groups (100% vs 33%) was significantly different (P = .022). Volunteers underwent repeat CHMI at 37-40 weeks after last dose. 6/6 and 5/6 volunteers developed parasitemia, but time to first parasitemia was significantly longer than controls in the 9 × 105 PfSPZ group (10.89 vs 7.80 days) (P = .039), indicating a significant reduction in parasites in the liver. Antibody and T-cell responses were higher in the 1.8 × 106 PfSPZ group. CONCLUSIONS: In Tanzania, increasing the dose from 2.7 × 105 to 9 × 105 PfSPZ increased VE from 20% to 100%, but increasing to 1.8 × 106 PfSPZ significantly reduced VE. CLINICAL TRIALS REGISTRATION: NCT02613520.
Assuntos
Vacinas Antimaláricas , Malária Falciparum , Malária , Adulto , Animais , Europa (Continente) , Humanos , Malária/prevenção & controle , Malária Falciparum/prevenção & controle , Mali , Plasmodium falciparum , Esporozoítos , TanzâniaRESUMO
BACKGROUND: The whole Plasmodium falciparum sporozoite (PfSPZ) vaccine is being evaluated for malaria prevention. The vaccine is administered intravenously for maximal efficacy. Direct venous inoculation (DVI) with PfSPZ vaccine has been safe, tolerable, and feasible in adults, but safety data for children and infants are limited. METHODS: We conducted an age de-escalation, dose-escalation randomized controlled trial in Siaya County, western Kenya. Children and infants (aged 5-9 years, 13-59 months, and 5-12 months) were enrolled into 13 age-dose cohorts of 12 participants and randomized 2:1 to vaccine or normal saline placebo in escalating doses: 1.35 × 105, 2.7 × 105, 4.5 × 105, 9.0 × 105, and 1.8 × 106 PfSPZ, with the 2 highest doses given twice, 8 weeks apart. Solicited adverse events (AEs) were monitored for 8 days after vaccination, unsolicited AEs for 29 days, and serious AEs throughout the study. Blood taken prevaccination and 1 week postvaccination was tested for immunoglobulin G antibodies to P. falciparum circumsporozoite protein (PfCSP) using enzyme-linked immunosorbent assay. RESULTS: Rates of AEs were similar in vaccinees and controls for solicited (35.7% vs 41.5%) and unsolicited (83.9% vs 92.5%) AEs, respectively. No related grade 3 AEs, serious AEs, or grade 3 laboratory abnormalities occurred. Most (79.0%) vaccinations were administered by a single DVI. Among those in the 9.0 × 105 and 1.8 × 106 PfSPZ groups, 36 of 45 (80.0%) vaccinees and 4 of 21 (19.0%) placebo controls developed antibodies to PfCSP (P < .001). CONCLUSIONS: PfSPZ vaccine in doses as high as 1.8 × 106 can be administered to infants and children by DVI, and was safe, well tolerated, and immunogenic. CLINICAL TRIALS REGISTRATION: NCT02687373.