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The 2014 Zaire Ebola virus outbreak highlighted the need for a safe, effective vaccine with a rapid onset of protection. We report the safety and immunogenicity of the recombinant vesicular stomatitis virus-Zaire Ebola virus envelope glycoprotein vaccine (rVSV∆G-ZEBOV-GP) across a 6 log10 dose range in two sequential cohorts. In this phase 1b double-blind, placebo-controlled, dose-response study we enrolled and randomly assigned healthy adults (aged 18–61 years) at eight study sites in the USA to receive a single injection of vaccine or placebo, administered by intramuscular injection. In cohort 1, participants were assigned to receive 3 × 103, 3 × 104, 3 × 105, or 3 × 106 PFU doses of rVSV∆G-ZEBOV-GP or placebo. In cohort 2, participants were assigned to receive 3 × 106, 9 × 106, 2 × 107, or 1 × 108 PFU doses of rVSV∆G-ZEBOV-GP or placebo. Participants were centrally allocated by the study statistician to vaccine groups or placebo through computer-generated randomisation lists. The primary safety outcome was incidence of adverse events within 14 days in the modified intention-to-treat population (all randomly assigned participants who received vaccine or placebo), and the primary outcome for immunogenicity was IgG ELISA antibody titres at day 28 in the per-protocol population. Surveillance was enhanced for arthritis and dermatitis through to day 56. This study is registered with ClinicalTrials.gov, number NCT02314923. Between Dec 26, 2014, and June 8, 2015, 513 participants were enrolled and randomly assigned; one was not immunised because of unsuccessful phlebotomy. In cohort 1, 256 participants received vaccine (3 × 103 [n=64], 3 × 104 [n=64], 3 × 105 [n=64], or 3 × 106 PFU [n=64]) and 74 received placebo. In cohort 2, 162 participants received vaccine (3 × 106 [n=20], 9 × 106 [n=47], 2 × 107 [n=47], or 1 × 108 PFU [n=48]) and 20 received placebo. Most adverse events occurred in the first day after vaccination, and were mild to moderate in intensity, of a short duration, and more frequent at high vaccine doses (9 × 106 PFU and greater). At the 2 × 107 PFU dose (used in phase 3 trials), the most common local adverse events versus placebo within the first 14 days were arm pain (57·4% [27 of 47] vs 7·4% [seven of 94]) and local tenderness (59·6% [28 of 47] vs 8·5% [eight of 94]). The most common systemic adverse events at the 2 × 107 PFU dose versus placebo, occurring in the first 14 days, were headache (46·8% [22 of 47] vs 27·7% [26 of 94]), fatigue (38·3% [18 of 47] vs 19·1% [18 of 94]), myalgia (34·0% [16 of 47] vs 10·6% [10 of 94]), subjective fever (29·8% [14 of 47] vs 2·1% [two of 94]), shivering or chills (27·7% [13 of 47] vs 7·4% [seven of 94]), sweats (23·4% [11 of 47] vs 3·2% [three of 94]), joint aches and pain (19·1% [nine of 47] vs 7·4% [seven of 94]), objective fever (14·9% [seven of 47] vs 1·1% [one of 94]), and joint tenderness or swelling (14·9% [seven of 47] vs 2·1% [two of 94]). Self-limited, post-vaccination arthritis occurred in 4·5% (19 of 418) of vaccinees (median onset 12·0 days [IQR 10–14]; median duration 8·0 days [6–15]) versus 3·2% (three of 94) of controls (median onset 15·0 days [6–20]; median duration 47·0 days [37–339]), with no apparent dose relationship. Post-vaccination dermatitis occurred in 5·7% (24 of 418) of vaccinees (median onset 9·0 days [IQR 2–12]; median duration 7·0 days [4–9]) versus 3·2% (three of 94) of controls (median onset 5·0 days [3–53]; median duration 33·0 days [5–370]). A low-level, transient, dose-dependent viraemia occurred in concert with early reactogenicity. Antibody responses were observed in most participants by day 14. IgG and neutralising antibody titres were dose-related (p=0·0003 for IgG ELISA and p<0·0001 for the 60% plaque-reduction neutralisation test [PRNT60] by linear trend). On day 28 at the 2 × 107 PFU dose, the geometric mean IgG ELISA endpoint titre was 1624 (95% CI 1146–2302) and seroconversion was 95·7% (95% CI 85·5–98·8); the geometric mean neutralising antibody titre by PRNT60 was 250 (176–355) and seroconversion was 95·7% (85·5–98·8). These robust immunological responses were sustained for 1 year. rVSV∆G-ZEBOV-GP was well tolerated and stimulated a rapid onset of binding and neutralising antibodies, which were maintained through to day 360. The immunogenicity results support selection of the 2 × 107 PFU dose. Biomedical Advanced Research and Development Authority, US Department of Health and Human Services.

In this study of 400 children in Mali, an adjuvanted vaccine based on an apical membrane antigen 1 from the 3D7 strain of Plasmodium falciparum (a blood-stage antigen) showed some strain-specific activity in preventing clinical malaria. An effective malaria vaccine would improve the prospects for eradicating malaria. 1 Vaccines that interrupt the transmission of malaria are emphasized in discussions of eradication, 2 but the ideal malaria vaccine would provide a direct clinical benefit. Vaccines targeting the blood stages of malaria are intended to reduce morbidity and mortality and are being developed in hopes of creating a multistage, multiantigen vaccine. 3 Vaccines based on two polymorphic Plasmodium falciparum blood-stage proteins, merozoite surface protein 1 4 and apical membrane antigen 1 (AMA1), 5 were not shown to be effective in recent studies, probably because of insufficient cross-protection against diverse malaria strains 6 , 7 or . . .

Background To further increase the efficacy of malaria vaccine RTS,S/AS02A, we tested the RTS,S antigen formulated using the AS01B Adjuvant System (GlaxoSmithKline Biologicals). Methods In a double-blind, randomized trial, 102 healthy volunteers were evenly allocated to receive RTS,S/AS01B or RTS,S/AS02A vaccine at months 0, 1, and 2 of the study, followed by malaria challenge. Protected vaccine recipients were rechallenged 5 months later. Results RTS,S/AS01B and RTS,S/AS02A were well tolerated and were safe. The efficacy of RTS,S/AS01B and RTS,S/AS02A was 50% (95% confidence interval [CI], 32.9%–67.1%) and 32% (95% CI, 17.6%–47.6%), respectively. At the time of initial challenge, the RTS,S/AS01B group had greater circumsporozoite protein (CSP)-specific immune responses, including higher immunoglobulin (Ig) G titers, higher numbers of CSP-specific CD4+ T cells expressing ⩾2 activation markers (interleukin-2, interferon [IFN]-γ, tumor necrosis factor-α, or CD40L), and more ex vivo IFN-γ enzyme-linked immunospots (ELISPOTs) than did the RTS,S/AS02A group. Protected vaccine recipients had a higher CSP-specific IgG titer (geometric mean titer, 188 vs 73 µg/mL; P <.001), higher numbers of CSP-specific CD4+ T cells per 106 CD4+ T cells (median, 963 vs 308 CSP-specific CD4+ T cells/106 CD4+ T cells; P <.001), and higher numbers of ex vivo IFN-γ ELISPOTs (mean, 212 vs 96 spots/million cells; P <.001 ). At rechallenge, 4 of 9 vaccine recipients in each group were still completely protected. Conclusions The RTS,S/AS01B malaria vaccine warrants comparative field trials with RTS,S/AS02A to deter-mine the best formulation for the protection of children and infants. The association between complete protection and immune responses is a potential tool for further optimization of protection. Trial registration ClinicalTrials.gov identifier NCT00075049.

The 2013–2016 Ebola virus outbreak in West Africa was the most widespread in history. In response, alive attenuated recombinant vesicular stomatitis virus (rVSV) vaccine expressing Zaire Ebolavirus glycoprotein (rVSVΔG-ZEBOV-GP) was evaluated in humans. In a phase 1, randomized, dose-ranging, observer-blind, placebo-controlled trial, healthy adults aged 18–65 years were randomized into 4 groups of 10 to receive one of 3 vaccine doses or placebo. Follow-up visits spanned 180 days postvaccination for safety monitoring, immunogenicity testing and any rVSV virus shedding. Forty participants were injected with rVSVΔG-ZEBOV-GP vaccine (n = 30) or saline placebo (n = 10). No serious adverse events related to the vaccine or participant withdrawals were reported. Solicited adverse events during the 14-day follow-up period were mild to moderate and self-limited, with the exception of injection-site pain and headache. Viremia following vaccination was transient and no longer detectable after study day 3, with no virus shedding in saliva or urine. All vaccinated participants developed serum immunoglobulin G (IgG), as measured by Ebola virus envelope glycoprotein-based enzyme-linked immunosorbent assay (ELISA). Immunogenicity was comparable across all dose groups, and sustained IgG titers were detectable through to the last visit, at study day 180. In this phase 1 study, there were no safety concerns after a single dose of rVSVΔG-ZEBOV-GP vaccine. IgG ELISA showed persistent high titers at 180 days postimmunization. There was a period of reactogenicity, but in general, the vaccine was well tolerated. This study provides evidence of the safety and immunogenicity of rVSVΔG-ZEBOV-GP vaccine and importance of its further investigation. Trial registration: Clinical-Trials.gov no., NCT02374385

The 2014–2016 Ebola outbreak caused over 28,000 cases and 11,000 deaths. Merck & Co. Inc., Kenilworth, NJ USA and NewLink Genetics are working with private and public partners to develop and license an Ebola vaccine that was evaluated extensively during the outbreak. The vaccine referred to as V920 is a recombinant vesicular stomatitis virus (rVSV) in which the VSV-G envelope glycoprotein (GP) is completely replaced by the Zaire ebolavirus GP (rVSVΔG-ZEBOV-GP). Eight Phase I and four Phase II/III clinical trials enrolling approximately 17,000 subjects were conducted in parallel to the outbreak to assess the safety, immunogenicity, and/or efficacy of V920. Immunogenicity data demonstrate that anti-GP antibodies are generally detectable by ELISA by 14days postvaccination with up to 100% seroconversion observed by 28days post dose. In addition, the results of a ring vaccination trial conducted by the WHO and their partners in Guinea suggest robust vaccine efficacy within 10days of receipt of a single dose of vaccine. The vaccine is generally well-tolerated when administered to healthy, non-pregnant adults. The development of this vaccine candidate in the context of this unprecedented epidemic has involved the close cooperation of large number of international partners and highlights what we as a public health community can accomplish when working together towards a common goal. Study identification: V920-001 to V920-012. CLINICALTRIALS.GOV identifiers: NCT02269423; NCT02280408; NCT02374385; NCT02314923; NCT02287480; NCT02283099; NCT02296983; NCT02344407; NCT02378753; NCT02503202.

In an attempt to improve the efficacy of the candidate malaria vaccine RTS,S/AS02, two studies were conducted in 1999 in healthy volunteers of RTS,S/AS02 in combination with recombinant Plasmodium falciparum thrombospondin-related anonymous protein (TRAP). In a Phase 1 safety and immunogenicity study, volunteers were randomized to receive TRAP/AS02 (N=10), RTS,S/AS02 (N=10), or RTS,S+TRAP/AS02 (N=20) at 0, 1 and 6-months. In a Phase 2 challenge study, subjects were randomized to receive either RTS,S+TRAP/AS02 (N=25) or TRAP/AS02 (N=10) at 0 and 1-month, or to a challenge control group (N=8). In both studies, the combination vaccine had an acceptable safety profile and was acceptably tolerated. Antigen-specific antibodies, lymphoproliferative responses, and IFN-γ production by ELISPOT assay elicited with the combination vaccine were qualitatively similar to those generated by the single component vaccines. However, post-dose 2 anti-CS antibodies in the RTS,S+TRAP/AS02 vaccine recipients were lower than in the RTS,S/AS02 vaccine recipients. After challenge, 10 of 11 RTS,S+TRAP/AS02 vaccinees, 5 of 5 TRAP/AS02 vaccinees, and 8 of 8 infectivity controls developed parasitemia, with median pre-patent periods of 13.0, 11.0, and 12.0 days, respectively. The absence of any prevention or delay of parasitemia by TRAP/AS02 suggests no apparent added value of TRAP/AS02 as a candidate vaccine. The absence of significant protection or delay of parasitemia in the 11 RTS,S+TRAP/AS02 vaccine recipients contrasts with previous 2 dose studies of RTS,S/AS02. The small sample size did not permit identifying statistically significant differences between the study arms. However, we speculate, within the constraints of the challenge study, that the presence of the TRAP antigen may have interfered with the vaccine efficacy previously observed with this regimen of RTS,S/AS02, and that any future TRAP-based vaccines should consider employing alternative vaccine platforms.

The disappointing efficacy of blood-stage malaria vaccines may be explained in part by allele-specific immune responses that are directed against polymorphic epitopes on blood-stage antigens. FMP2.1/AS02 A , a bloodstage candidate vaccine based on apical membrane antigen 1 (AMA1) from the 3D7 strain of Plasmodium falciparum had allele-specific efficacy against clinical malaria in a phase II trial in Malian children. We assessed the cross-protective efficacy of the malaria vaccine and inferred which polymorphic amino acid positions in AMA1 were the targets of protective allele-specific immune responses. FMP2.1/AS02 A had the highest efficacy against AMA1 alíeles that were identical to the 3D7 vaccine-type alíele at 8 highly polymorphic amino acid positions in the cluster 1 loop (c1L) but differed from 3D7 elsewhere in the molecule. Comparison of the incidence of vaccine-type alíeles before and after vaccination in the malaria vaccine and control groups and examination of the patterns of alíele change at polymorphic positions in consecutive malaria episodes suggest that the highly polymorphic amino acid position 197 in c1L was the most critical determinant of allele-specific efficacy. These results indicate that a multivalent AMA1 vaccine with broad efficacy could include only a limited set of key alíeles of this extremely polymorphic antigen.

This study advances the clinical development of the RTS,S/AS01B candidate malaria vaccine to malaria endemic populations. As a primary objective it compares the safety and reactogenicity of RTS,S/AS01B to the more extensively evaluated RTS,S/AS02A vaccine. A Phase IIb, single centre, double-blind, controlled trial of 6 months duration with a subsequent 6 month single-blind follow-up conducted in Kisumu West District, Kenya between August 2005 and August 2006. 255 healthy adults aged 18 to 35 years were randomized (1ratio1ratio1) to receive 3 doses of RTS,S/AS02A, RTS,S/AS01B or rabies vaccine (Rabipur; Chiron Behring GmbH) at months 0, 1, 2. The primary objective was the occurrence of severe (grade 3) solicited or unsolicited general (i.e. systemic) adverse events (AEs) during 7 days follow up after each vaccination. Both candidate vaccines had a good safety profile and were well tolerated. One grade 3 systemic AE occurred within 7 days of vaccination (RTS,S/AS01B group). No unsolicited AEs or SAEs were related to vaccine. A marked increase in anti-CS antibody GMTs was observed post Dose 2 of both RTS,S/AS01B (31.6 EU/mL [95% CI: 23.9 to 41.6]) and RTS,S/AS02A (16.7 EU/mL [95% CI: 12.9 to 21.7]). A further increase was observed post Dose 3 in both the RTS,S/AS01B (41.4 EU/mL [95% CI: 31.7 to 54.2]) and RTS,S/AS02A (21.4 EU/mL [95% CI: 16.0 to 28.7]) groups. Anti-CS antibody GMTs were significantly greater with RTS,S/AS01B compared to RTS,S/AS02A at all time points post Dose 2 and Dose 3. Both candidate vaccines produced strong anti-HBs responses. Vaccine efficacy in the RTS,S/AS01B group was 29.5% (95% CI: -15.4 to 56.9, p = 0.164) and in the RTS,S/AS02A group 31.7% (95% CI: -11.6 to 58.2, p = 0.128). Both candidate malaria vaccines were well tolerated over a 12 month surveillance period. A more favorable immunogenicity profile was observed with RTS,S/AS01B than with RTS,S/AS02A. Clinicaltrials.gov NCT00197054.

•Report on first-in-human safety and immunogenicity testing of a genetically attenuated parasite (GAP) P. falciparum strain.•Five out of six volunteers remained peripheral blood smear negative after GAP-infected mosquitoe bite.•Severe attenuation and favorable immune responses following administration p52−/p36− GAP were observed.•Results suggest that further development of live-attenuated GAP strains using genetic engineering should be pursued. Immunization with genetically engineered, attenuated malaria parasites (GAP) that arrest during liver infection confers sterile protection in mouse malaria models. A first generation Plasmodium falciparum GAP (Pf p52−/p36− GAP) was previously generated by deletion of two pre-erythrocytic stage-expressed genes (P52 and P36) in the NF54 strain. A first-in-human, proof-of-concept, safety and immunogenicity clinical trial in six human volunteers was conducted. Exposure consisted of delivery of Pf p52−/p36− GAP sporozoites via infected Anopheles mosquito bite with a five-bite/volunteer exposure followed by an approximately 200-bite exposure/volunteer one month later. The exposures were well tolerated with mild to moderate local and systemic reactions. All volunteers remained blood stage negative after low dose exposure. Five volunteers remained blood stage negative after high dose exposure. One volunteer developed peripheral parasitemia twelve days after high dose exposure. Together the findings indicate that Pf p52−/p36− GAP was severely but not completely attenuated. All six volunteers developed antibodies to CSP. Furthermore, IFN-γ responses to whole sporozoites and multiple antigens were elicited in 5 of 6 volunteers, with both CD4 and CD8 cell cytokine production detected. Severe attenuation and favorable immune responses following administration of a first generation Pf p52−/p36− GAP suggests that further development of live-attenuated strains using genetic engineering should be pursued.

Background. Patterns of expressed genes in the peripheral blood mononuclear cells of persons who were receiving RTS,S/AS01 or RTS,S/AS02 malaria vaccine and were undergoing experimental challenge with mosquito-borne falciparum malaria were examined to identify markers associated with protection. Methods. Thirty-nine vaccine recipients were assessed at study entry; on the day of the third vaccination; at 24 h, 72 h, and 2 weeks after vaccination; and on day 5 after challenge. Of 39 vaccine recipients, 13 were protected and 26 were not. Eleven vaccine recipients exhibited delayed onset of parasitemia. All infectivity control subjects developed parasitemia. Prediction analysis of microarrays identified genes corresponding with protection. Gene set enrichment analysis identified sets of genes associated with protection after the third vaccination and before challenge. Results. After the third vaccination and before challenge, differential expression of genes in the immunoproteasome pathway distinguished protected and nonprotected persons. At 5 days after challenge, differential expression of genes associated with programmed cell death distinguished between subjects protected and not protected from malaria blood-stage infection. Conclusions. The up-regulation of genes associated with the efficient processing of major histocompatibility complex peptides suggests a potential role of the vaccine in conferring major histocompatibility complex class 1—mediated protection and may represent a useful surrogate marker of vaccine efficacy without the need for challenge.