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The causal association of Zika virus (ZIKV) with microcephaly, congenital malformations in infants, and Guillain-Barré syndrome in adults highlights the need for effective vaccines. Thus far, efforts to develop ZIKV vaccines have focused on the viral envelope. ZIKV NS1 as a vaccine immunogen has not been fully explored, although it can circumvent the risk of antibody-dependent enhancement of ZIKV infection, associated with envelope antibodies. Here, we describe a novel DNA vaccine encoding a secreted ZIKV NS1, that confers rapid protection from systemic ZIKV infection in immunocompetent mice. We identify novel NS1 T cell epitopes in vivo and show that functional NS1-specific T cell responses are critical for protection against ZIKV infection. We demonstrate that vaccine-induced anti-NS1 antibodies fail to confer protection in the absence of a functional T cell response. This highlights the importance of using NS1 as a target for T cell–based ZIKV vaccines.

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Background Given the scale of the ongoing COVID-19 pandemic, the development of vaccines based on different platforms is essential, particularly in light of emerging viral variants, the absence of information on vaccine-induced immune durability, and potential paediatric use. We aimed to assess the safety and immunogenicity of an MF59-adjuvanted subunit vaccine for COVID-19 based on recombinant SARS-CoV-2 spike glycoprotein stabilised in a pre-fusion conformation by a novel molecular clamp (spike glycoprotein-clamp [sclamp]). Methods We did a phase 1, double-blind, placebo-controlled, block-randomised trial of the sclamp subunit vaccine in a single clinical trial site in Brisbane, QLD, Australia. Healthy adults (aged ≥18 to ≤55 years) who had tested negative for SARS-CoV-2, reported no close contact with anyone with active or previous SARS-CoV-2 infection, and tested negative for pre-existing SARS-CoV-2 immunity were included. Participants were randomly assigned to one of five treatment groups and received two doses via intramuscular injection 28 days apart of either placebo, sclamp vaccine at 5 μg, 15 μg, or 45 μg, or one dose of sclamp vaccine at 45 μg followed by placebo. Participants and study personnel, except the dose administration personnel, were masked to treatment. The primary safety endpoints included solicited local and systemic adverse events in the 7 days after each dose and unsolicited adverse events up to 12 months after dosing. Here, data are reported up until day 57. Primary immunogenicity endpoints were antigen-specific IgG ELISA and SARS-CoV-2 microneutralisation assays assessed at 28 days after each dose. The study is ongoing and registered with ClinicalTrials.gov , NCT04495933 . Findings Between June 23, 2020, and Aug 17, 2020, of 314 healthy volunteers screened, 120 were randomly assigned (n=24 per group), and 114 (95%) completed the study up to day 57 (mean age 32·5 years [SD 10·4], 65 [54%] male, 55 [46%] female). Severe solicited reactions were infrequent and occurred at similar rates in participants receiving placebo (two [8%] of 24) and the SARS-CoV-2 sclamp vaccine at any dose (three [3%] of 96). Both solicited reactions and unsolicited adverse events occurred at a similar frequency in participants receiving placebo and the SARS-CoV-2 sclamp vaccine. Solicited reactions occurred in 19 (79%) of 24 participants receiving placebo and 86 (90%) of 96 receiving the SARS-CoV-2 sclamp vaccine at any dose. Unsolicited adverse events occurred in seven (29%) of 24 participants receiving placebo and 35 (36%) of 96 participants receiving the SARS-CoV-2 sclamp vaccine at any dose. Vaccination with SARS-CoV-2 sclamp elicited a similar antigen-specific response irrespective of dose: 4 weeks after the initial dose (day 29) with 5 μg dose (geometric mean titre [GMT] 6400, 95% CI 3683–11 122), with 15 μg dose (7492, 4959–11 319), and the two 45 μg dose cohorts (8770, 5526–13...

There are 3 to 4 million new hepatitis C virus (HCV) infections annually around the world, but no vaccine is available. Robust T-cell mediated responses are necessary for effective clearance of the virus, and DNA vaccines result in a cell-mediated bias. Adjuvants are often required for effective vaccination, but during natural lytic viral infections damage-associated molecular patterns (DAMPs) are released, which act as natural adjuvants. Hence, a vaccine that induces cell necrosis and releases DAMPs will result in cell-mediated immunity (CMI), similar to that resulting from natural lytic viral infection. We have generated a DNA vaccine with the ability to elicit strong CMI against the HCV nonstructural (NS) proteins (3, 4A, 4B, and 5B) by encoding a cytolytic protein, perforin (PRF), and the antigens on a single plasmid. We examined the efficacy of the vaccines in C57BL/6 mice, as determined by gamma interferon enzyme-linked immunosorbent spot assay, cell proliferation studies, and intracellular cytokine production. Initially, we showed that encoding the NS4A protein in a vaccine which encoded only NS3 reduced the immunogenicity of NS3, whereas including PRF increased NS3 immunogenicity. In contrast, the inclusion of NS4A increased the immunogenicity of the NS3, NS4B, andNS5B proteins, when encoded in a DNA vaccine that also encoded PRF. Finally, vaccines that also encoded PRF elicited similar levels of CMI against each protein after vaccination with DNA encoding NS3, NS4A, NS4B, and NS5B compared to mice vaccinated with DNA encoding only NS3 or NS4B/5B. Thus, we have developed a promising "multiantigen" vaccine that elicits robust CMI. IMPORTANCESince their development, vaccines have reduced the global burden of disease. One strategy for vaccine development is to use commercially viable DNA technology, which has the potential to generate robust immune responses. Hepatitis C virus causes chronic liver infection and is a leading cause of liver cancer. To date, no vaccine is currently available, and treatment is costly and often results in side effects, limiting the number of patients who are treated. Despite recent advances in treatment, prevention remains the key to efficient control and elimination of this virus. Here, we describe a novel DNA vaccine against hepatitis C virus that is capable of inducing robust cell-mediated immune responses in mice and is a promising vaccine candidate for humans. G lobal efforts to generate an effective vaccine for hepatitis C virus (HCV) have been hampered, since correlates of sterilizing immunity have not been identified and traditional vaccine strategies have proved to be ineffective (1). Approximately 230 million individuals are infected, many of whom will develop serious liver disease, and since current treatment is costly and often results in serious side effects, this has limited the number of patients who are treated (2, 3). Much of the global effort to develop an effective HCV vaccine/treatment has been directed toward genotype 1 (gt1) (4, 5); however, gt3 is ...

Currently, no vaccine is available against hepatitis C virus (HCV), and although DNA vaccines have considerable potential, this has not been realised. Previously, the efficacy of DNA vaccines for human immunodeficiency virus (HIV) and HCV was shown to be enhanced by including the gene for a cytolytic protein, viz. perforin. In this study, we examined the mechanism of cell death by this bicistronic DNA vaccine, which encoded the HCV non-structural protein 3 (NS3) under the control of the CMV promoter and perforin is controlled by the SV40 promoter. Compared with a canonical DNA vaccine and a bicistronic DNA vaccine encoding NS3 and the proapoptotic gene NSP4, the perforin-containing vaccine elicited enhanced cell-mediated immune responses against the NS3 protein in vaccinated mice and pigs, as determined by ELISpot and intracellular cytokine staining, whereas a mouse challenge model suggested that the immunity was CD8(+) T-cell-dependent. The results of the study showed that the inclusion of perforin in the DNA vaccine altered the fate of NS3-positive cells from apoptosis to necrosis, and this resulted in more robust immune responses in mice and pigs, the latter of which represents an accepted large animal model in which to test vaccine efficacy.

Objectives Efforts to develop and deploy effective vaccines against severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) continue at pace. Here, we describe rational antigen design through to manufacturability and vaccine efficacy of a prefusion‐stabilised spike (S) protein, Sclamp, in combination with the licensed adjuvant MF59 ‘MF59C.1’ (Seqirus, Parkville, Australia). Methods A panel recombinant Sclamp proteins were produced in Chinese hamster ovary and screened in vitro to select a lead vaccine candidate. The structure of this antigen was determined by cryo‐electron microscopy and assessed in mouse immunogenicity studies, hamster challenge studies and safety and toxicology studies in rat. Results In mice, the Sclamp vaccine elicits high levels of neutralising antibodies, as well as broadly reactive and polyfunctional S‐specific CD4 + and cytotoxic CD8 + T cells in vivo . In the Syrian hamster challenge model ( n = 70), vaccination results in reduced viral load within the lung, protection from pulmonary disease and decreased viral shedding in daily throat swabs which correlated strongly with the neutralising antibody level. Conclusion The SARS‐CoV‐2 Sclamp vaccine candidate is compatible with large‐scale commercial manufacture, stable at 2–8°C. When formulated with MF59 adjuvant, it elicits neutralising antibodies and T‐cell responses and provides protection in animal challenge models.

A universal hepatitis C virus (HCV) vaccine should elicit multiantigenic, multigenotypic responses, which are more likely to protect against challenge with the range of genotypes and subtypes circulating in the community. A vaccine cocktail and vaccines encoding consensus HCV sequences are attractive approaches to achieve this goal. Consequently, in a series of mouse vaccination studies, we compared the immunogenicity of a DNA vaccine encoding a consensus HCV nonstructural 5B (NS5B) protein to that of a cocktail of DNA plasmids encoding the genotype 1b (Gt1b) and Gt3a NS5B proteins. To complement this study, we assessed responses to a multiantigenic cocktail regimen by comparing a DNA vaccine cocktail encoding Gt1b and Gt3a NS3, NS4, and NS5B proteins to a single-genotype NS3/4/5B DNA vaccine. To thoroughly evaluate cytotoxic T lymphocyte (CTL) and T helper (Th) cell responses against Gt1b and Gt3a HCV peptide-pulsed target cells, we exploited a novel fluorescent-target array (FTA). FTA and enzyme-linked immunosorbent spot (ELISpot) analyses collectively indicated that the cocktail regimens elicited higher responses to Gt1b and Gt3a NS5B proteins than those with the consensus vaccine, while the multiantigenic DNA cocktail significantly increased the responses to NS3 and NS5B compared to those elicited by the single-genotype vaccines. Thus, a DNA cocktail vaccination regimen is more effective than a consensus vaccine or a monovalent vaccine at increasing the breadth of multigenotypic T cell responses, which has implications for the development of vaccines for communities where multiple HCV genotypes circulate. Despite the development of highly effective direct-acting antivirals (DAA), infections with hepatitis C virus (HCV) continue, particularly in countries where the supply of DAA is limited. Furthermore, patients who eliminate the virus as a result of DAA therapy can still be reinfected. Thus, a vaccine for HCV is urgently required, but the heterogeneity of HCV strains makes the development of a universal vaccine difficult. To address this, we developed a novel cytolytic DNA vaccine which elicits robust cell-mediated immunity (CMI) to the nonstructural (NS) proteins in vaccinated animals. We compared the immune responses against genotypes 1 and 3 that were elicited by a consensus DNA vaccine or a DNA vaccine cocktail and showed that the cocktail induced higher levels of CMI to the NS proteins of both genotypes. This study suggests that a universal HCV vaccine can most readily be achieved by use of a DNA vaccine cocktail.