Laura Novik

Protection Against Malaria by Intravenous Immunization with a Nonreplicating Sporozoite Vaccine

Malaria Sporozoite Vaccine Each year, hundreds of millions of people are infected with Plasmodium falciparum, the mosquito-borne parasite that causes malaria. A preventative vaccine is greatly needed. Seder et al. (p. 1359, published online 8 August; see the Perspective by Good) now report the results from a phase I clinical trial where subjects were immunized intravenously with a whole, attenuated sporozoite vaccine. Three of 9 subjects who received four doses and zero of 6 subjects who received five doses of the vaccine went on to develop malaria after controlled malaria infection. Both antibody titers and cellular immune responses correlated positively with the dose of vaccine received, suggesting that both arms of the adaptive immune response may have participated in the observed protection. Intravenous immunization with an attenuated whole malaria sporozoite vaccine protected volunteers in a phase I clinical trial. [Also see Perspective by Good] Consistent, high-level, vaccine-induced protection against human malaria has only been achieved by inoculation of Plasmodium falciparum (Pf) sporozoites (SPZ) by mosquito bites. We report that the PfSPZ Vaccine—composed of attenuated, aseptic, purified, cryopreserved PfSPZ—was safe and wel-tolerated when administered four to six times intravenously (IV) to 40 adults. Zero of six subjects receiving five doses and three of nine subjects receiving four doses of 1.35 × 105 PfSPZ Vaccine and five of six nonvaccinated controls developed malaria after controlled human malaria infection (P = 0.015 in the five-dose group and P = 0.028 for overall, both versus controls). PfSPZ-specific antibody and T cell responses were dose-dependent. These data indicate that there is a dose-dependent immunological threshold for establishing high-level protection against malaria that can be achieved with IV administration of a vaccine that is safe and meets regulatory standards.

Phase 1 Safety and Immunogenicity Evaluation of a Multiclade HIV‐1 Candidate Vaccine Delivered by a Replication‐Defective Recombinant Adenovirus Vector

BACKGROUND The development of an effective human immunodeficiency virus (HIV) vaccine is a high global priority. Here, we report the safety, tolerability, and immunogenicity of a replication-defective recombinant adenovirus serotype 5 (rAd5) vector HIV-1 candidate vaccine. METHODS The vaccine is a mixture of 4 rAd5 vectors that express HIV-1 subtype B Gag-Pol fusion protein and envelope (Env) from subtypes A, B, and C. Healthy, uninfected adults were randomized to receive 1 intramuscular injection of placebo (n=6) or vaccine at dose levels of 10(9) (n=10), 10(10) (n=10), or 10(11) (n=10) particle units and were followed for 24 weeks to assess immunogenicity and safety. RESULTS The vaccine was well tolerated but was associated with more reactogenicity at the highest dose. At week 4, vaccine antigen-specific T cell responses were detected in 28 (93.3%) and 18 (60%) of 30 vaccine recipients for CD4(+) and CD8(+) T cells, respectively, by intracellular cytokine staining assay and in 22 (73%) of 30 vaccine recipients by enzyme-linked immunospot assay. Env-specific antibody responses were detected in 15 (50%) of 30 vaccine recipients by enzyme-linked immunosorbant assay and in 28 (93.3%) of 30 vaccine recipients by immunoprecipitation followed by Western blotting. No neutralizing antibody was detected. CONCLUSIONS A single injection induced HIV-1 antigen-specific CD4(+) T cell, CD8(+) T cell, and antibody responses in the majority of vaccine recipients. This multiclade rAd5 HIV-1 vaccine is now being evaluated in combination with a multiclade HIV-1 DNA plasmid vaccine.

Chimpanzee Adenovirus Vector Ebola Vaccine - Preliminary Report.

Background The unprecedented 2014 epidemic of Ebola virus disease (EVD) prompted an international response to accelerate the availability of a preventive vaccine. A replication‐defective recombinant chimpanzee adenovirus type 3–vectored ebolavirus vaccine (cAd3‐EBO), encoding the glycoprotein from Zaire and Sudan species, that offers protection in the nonhuman primate model, was rapidly advanced into phase 1 clinical evaluation. Methods We conducted a phase 1, dose‐escalation, open‐label trial of cAd3‐EBO. Twenty healthy adults, in sequentially enrolled groups of 10 each, received vaccination intramuscularly in doses of 2×1010 particle units or 2×1011 particle units. Primary and secondary end points related to safety and immunogenicity were assessed throughout the first 8 weeks after vaccination; in addition, longer‐term vaccine durability was assessed at 48 weeks after vaccination. Results In this small study, no safety concerns were identified; however, transient fever developed within 1 day after vaccination in two participants who had received the 2×1011 particle‐unit dose. Glycoprotein‐specific antibodies were induced in all 20 participants; the titers were of greater magnitude in the group that received the 2×1011 particle‐unit dose than in the group that received the 2×1010 particle‐unit dose (geometric mean titer against the Zaire antigen at week 4, 2037 vs. 331; P=0.001). Glycoprotein‐specific T‐cell responses were more frequent among those who received the 2×1011 particle‐unit dose than among those who received the 2×1010 particle‐unit dose, with a CD4 response in 10 of 10 participants versus 3 of 10 participants (P=0.004) and a CD8 response in 7 of 10 participants versus 2 of 10 participants (P=0.07) at week 4. Assessment of the durability of the antibody response showed that titers remained high at week 48, with the highest titers in those who received the 2×1011 particle‐unit dose. Conclusions Reactogenicity and immune responses to cAd3‐EBO vaccine were dose‐dependent. At the 2×1011 particle‐unit dose, glycoprotein Zaire–specific antibody responses were in the range reported to be associated with vaccine‐induced protective immunity in challenge studies involving nonhuman primates, and responses were sustained to week 48. Phase 2 studies and efficacy trials assessing cAd3‐EBO are in progress. (Funded by the Intramural Research Program of the National Institutes of Health; VRC 207 ClinicalTrials.gov number, NCT02231866.)

Priming Immunization with DNA Augments Immunogenicity of Recombinant Adenoviral Vectors for Both HIV-1 Specific Antibody and T-Cell Responses

Background Induction of HIV-1-specific T-cell responses relevant to diverse subtypes is a major goal of HIV vaccine development. Prime-boost regimens using heterologous gene-based vaccine vectors have induced potent, polyfunctional T cell responses in preclinical studies. Methods The first opportunity to evaluate the immunogenicity of DNA priming followed by recombinant adenovirus serotype 5 (rAd5) boosting was as open-label rollover trials in subjects who had been enrolled in prior studies of HIV-1 specific DNA vaccines. All subjects underwent apheresis before and after rAd5 boosting to characterize in depth the T cell and antibody response induced by the heterologous DNA/rAd5 prime-boost combination. Results rAd5 boosting was well-tolerated with no serious adverse events. Compared to DNA or rAd5 vaccine alone, sequential DNA/rAd5 administration induced 7-fold higher magnitude Env-biased HIV-1-specific CD8+ T-cell responses and 100-fold greater antibody titers measured by ELISA. There was no significant neutralizing antibody activity against primary isolates. Vaccine-elicited CD4+ and CD8+ T-cells expressed multiple functions and were predominantly long-term (CD127+) central or effector memory T cells and that persisted in blood for >6 months. Epitopes mapped in Gag and Env demonstrated partial cross-clade recognition. Conclusion Heterologous prime-boost using vector-based gene delivery of vaccine antigens is a potent immunization strategy for inducing both antibody and T-cell responses. Trial Registration ClinicalTrails.gov NCT00102089, NCT00108654

Protection against malaria at 1 year and immune correlates following PfSPZ vaccination

An attenuated Plasmodium falciparum (Pf) sporozoite (SPZ) vaccine, PfSPZ Vaccine, is highly protective against controlled human malaria infection (CHMI) 3 weeks after immunization, but the durability of protection is unknown. We assessed how vaccine dosage, regimen, and route of administration affected durable protection in malaria-naive adults. After four intravenous immunizations with 2.7 × 105 PfSPZ, 6/11 (55%) vaccinated subjects remained without parasitemia following CHMI 21 weeks after immunization. Five non-parasitemic subjects from this dosage group underwent repeat CHMI at 59 weeks, and none developed parasitemia. Although Pf-specific serum antibody levels correlated with protection up to 21–25 weeks after immunization, antibody levels waned substantially by 59 weeks. Pf-specific T cell responses also declined in blood by 59 weeks. To determine whether T cell responses in blood reflected responses in liver, we vaccinated nonhuman primates with PfSPZ Vaccine. Pf-specific interferon-γ-producing CD8 T cells were present at ∼100-fold higher frequencies in liver than in blood. Our findings suggest that PfSPZ Vaccine conferred durable protection to malaria through long-lived tissue-resident T cells and that administration of higher doses may further enhance protection.

DNA Vaccines Encoding Ebolavirus and Marburgvirus Wild Type Glycoproteins are Safe and Immunogenic in a Phase I Clinical Trial

Background Ebolavirus and Marburgvirus cause severe hemorrhagic fever with high mortality and are potential bioterrorism agents. There are no available vaccines or therapeutic agents. Previous clinical trials evaluated transmembrane-deleted and point-mutation Ebolavirus glycoproteins (GPs) in candidate vaccines. Constructs evaluated in this trial encode wild-type (WT) GP from Ebolavirus Zaire and Sudan species and the Marburgvirus Angola strain expressed in a DNA vaccine. Methods The VRC 206 study evaluated the safety and immunogenicity of these DNA vaccines (4 mg administered intramuscularly by Biojector) at weeks 0, 4, and 8, with a homologous boost at or after week 32. Safety evaluations included solicited reactogenicity and coagulation parameters. Primary immune assessment was done by means of GP-specific enzyme-linked immunosorbent assay. Results The vaccines were well tolerated, with no serious adverse events; 80% of subjects had positive enzyme-linked immunosorbent assay results (≥30) at week 12. The fourth DNA vaccination boosted the immune responses. Conclusions The investigational Ebolavirus and Marburgvirus WT GP DNA vaccines were safe, well tolerated, and immunogenic in this phase I study. These results will further inform filovirus vaccine research toward a goal of inducing protective immunity by using WT GP antigens in candidate vaccine regimens. Clinical Trials Registration NCT00605514.

Attenuated PfSPZ Vaccine induces strain-transcending T cells and durable protection against heterologous controlled human malaria infection

Significance A highly effective malaria vaccine capable of long-term protection against genetically diverse strains is urgently needed. Here, we demonstrate that a three-dose regimen of a live attenuated whole-parasite malaria vaccine conferred durable sterile protection through 33 weeks in ∼50% of subjects against a controlled human malaria infection strain that is heterologous to the vaccine strain. Prior studies by others and us have shown that T cells are critical to mediating sterile protection after live-attenuated malaria vaccination. Here, we provide evidence that this Plasmodium falciparum sporozoite vaccine (PfSPZ Vaccine) induces antigen-specific IFN-γ-producing CD8 and CD4 T cells that recognize both the homologous and the heterologous Pf strain. A live-attenuated malaria vaccine, Plasmodium falciparum sporozoite vaccine (PfSPZ Vaccine), confers sterile protection against controlled human malaria infection (CHMI) with Plasmodium falciparum (Pf) parasites homologous to the vaccine strain up to 14 mo after final vaccination. No injectable malaria vaccine has demonstrated long-term protection against CHMI using Pf parasites heterologous to the vaccine strain. Here, we conducted an open-label trial with PfSPZ Vaccine at a dose of 9.0 × 105 PfSPZ administered i.v. three times at 8-wk intervals to 15 malaria-naive adults. After CHMI with homologous Pf parasites 19 wk after final immunization, nine (64%) of 14 (95% CI, 35–87%) vaccinated volunteers remained without parasitemia compared with none of six nonvaccinated controls (P = 0.012). Of the nine nonparasitemic subjects, six underwent repeat CHMI with heterologous Pf7G8 parasites 33 wk after final immunization. Five (83%) of six (95% CI, 36–99%) remained without parasitemia compared with none of six nonvaccinated controls. PfSPZ-specific T-cell and antibody responses were detected in all vaccine recipients. Cytokine production by T cells from vaccinated subjects after in vitro stimulation with homologous (NF54) or heterologous (7G8) PfSPZ were highly correlated. Interestingly, PfSPZ-specific T-cell responses in the blood peaked after the first immunization and were not enhanced by subsequent immunizations. Collectively, these data suggest durable protection against homologous and heterologous Pf parasites can be achieved with PfSPZ Vaccine. Ongoing studies will determine whether protective efficacy can be enhanced by additional alterations in the vaccine dose and number of immunizations.

Safety, tolerability, and immunogenicity of two Zika virus DNA vaccine candidates in healthy adults: randomised, open-label, phase 1 clinical trials

Summary Background The Zika virus epidemic and associated congenital infections have prompted rapid vaccine development. We assessed two new DNA vaccines expressing premembrane and envelope Zika virus structural proteins. Methods We did two phase 1, randomised, open-label trials involving healthy adult volunteers. The VRC 319 trial, done in three centres, assessed plasmid VRC5288 (Zika virus and Japanese encephalitis virus chimera), and the VRC 320, done in one centre, assessed plasmid VRC5283 (wild-type Zika virus). Eligible participants were aged 18–35 years in VRC19 and 18–50 years in VRC 320. Participants were randomly assigned 1:1 by a computer-generated randomisation schedule prepared by the study statistician. All participants received intramuscular injection of 4 mg vaccine. In VRC 319 participants were assigned to receive vaccinations via needle and syringe at 0 and 8 weeks, 0 and 12 weeks, 0, 4, and 8 weeks, or 0, 4, and 20 weeks. In VRC 320 participants were assigned to receive vaccinations at 0, 4, and 8 weeks via single-dose needle and syringe injection in one deltoid or split-dose needle and syringe or needle-free injection with the Stratis device (Pharmajet, Golden, CO, USA) in each deltoid. Both trials followed up volunteers for 24 months for the primary endpoint of safety, assessed as local and systemic reactogenicity in the 7 days after each vaccination and all adverse events in the 28 days after each vaccination. The secondary endpoint in both trials was immunogenicity 4 weeks after last vaccination. These trials are registered with ClinicalTrials.gov, numbers NCT02840487 and NCT02996461. Findings VRC 319 enrolled 80 participants (20 in each group), and VRC 320 enrolled 45 participants (15 in each group). One participant in VRC 319 and two in VRC 320 withdrew after one dose of vaccine, but were included in the safety analyses. Both vaccines were safe and well tolerated. All local and systemic symptoms were mild to moderate. In both studies, pain and tenderness at the injection site was the most frequent local symptoms (37 [46%] of 80 participants in VRC 319 and 36 [80%] of 45 in VRC 320) and malaise and headache were the most frequent systemic symptoms (22 [27%] and 18 [22%], respectively, in VRC 319 and 17 [38%] and 15 [33%], respectively, in VRC 320). For VRC5283, 14 of 14 (100%) participants who received split-dose vaccinations by needle-free injection had detectable positive antibody responses, and the geometric mean titre of 304 was the highest across all groups in both trials. Interpretation VRC5283 was well tolerated and has advanced to phase 2 efficacy testing. Funding Intramural Research Program of the Vaccine Research Center, National Institute of Allergy and Infectious Diseases, National Institutes of Health.

Phase I Randomized Clinical Trial of VRC DNA and rAd5 HIV-1 Vaccine Delivery by Intramuscular (IM), Subcutaneous (SC) and Intradermal (ID) Administration (VRC 011)

Background Phase 1 evaluation of the VRC HIV DNA and rAd5 vaccines delivered intramuscularly (IM) supported proceeding to a Phase 2 b efficacy study. Here we report comparison of the IM, subcutaneous (SC) and intradermal (ID) routes of administration. Methods Sixty subjects were randomized to 6 schedules to evaluate the IM, SC or ID route for prime injections. Three schedules included DNA primes (Wks 0,4,8) and 3 schedules included rAd5 prime (Wk0); all included rAd5 IM boost (Wk24). DNA vaccine dosage was 4 mg IM or SC, but 0.4 mg ID, while all rAd5 vaccinations were 1010 PU. All injections were administered by needle and syringe. Results Overall, 27/30 subjects completed 3 DNA primes; 30/30 subjects completed rAd5 primes. Mild local pruritus (itchiness), superficial skin lesions and injection site nodules were associated with ID and SC, but not IM injections. All routes induced T-cell and antibody immune responses after rAd5 boosting. Overall, >95% had Env antibody and >80% had Env T-cell responses. Conclusions The pattern of local reactogenicity following ID and SC injections differed from IM injections but all routes were well-tolerated. There was no evidence of an immunogenicity advantage following SC or ID delivery, supporting IM delivery as the preferred route of administration. Trial Registration Clinicaltrials.gov NCT00321061

Phase I clinical evaluation of seasonal influenza hemagglutinin (HA) DNA vaccine prime followed by trivalent influenza inactivated vaccine (IIV3) boost

Annual influenza vaccination reduces the risks of influenza when the vaccines are well matched to circulating strains, but development of an approach that induces broader and more durable immune responses would be beneficial. We conducted two companion Phase 1 studies, VRC 307 and VRC 309, over sequential seasons (2008-2009 and 2009-2010) in which only the influenza B strain component of the vaccines differed. Objectives were safety and immunogenicity of prime-boost vaccination schedules. A schedule of DNA vaccine encoding for seasonal influenza hemagglutinins (HA) prime followed by seasonal trivalent influenza inactivated vaccine (IIV3) boost (HA DNA-IIV3) was compared to placebo (PBS)-IIV3 or IIV3-IIV3. Cumulatively, 111 adults were randomized to HA DNA-IIV3 (n=66), PBS-IIV3 (n=25) or IIV3-IIV3 (n=20). Safety was assessed by clinical observations, laboratory parameters and 7-day solicited reactogenicity. The seasonal HA DNA prime-IIV3 boost regimen was evaluated as safe and well tolerated. There were no serious adverse events. The local and systemic reactogenicity for HA DNA, IIV and placebo were reported predominantly as none or mild within the first 5days post-vaccination. There was no significant difference in immunogenicity detected between the treatment groups as evaluated by hemagglutination inhibition (HAI) assay. The studies demonstrated the safety and immunogenicity of seasonal HA DNA-IIV3 regimen, but the 3-4week prime-boost interval was suboptimal for improving influenza-specific immune responses. This is consistent with observations in avian H5 DNA vaccine prime-boost studies in which a long interval, but not a short interval, was associated with improved immunogenicity. TRIAL REGISTRATION NCT00858611 for VRC 307 and NCT00995982 for VRC 309.