Developmental and reproductive safety of Advax-CpG55.2™ adjuvanted COVID-19 and influenza vaccines in mice

A phase I study of the safety, reactogenicity and immunogenicity of two quadrivalent seasonal influenza vaccines (Fluzone® or Flublok®) with or without one of two adjuvants (AF03 or Advax-CpG55.2) in healthy adults 18-45 years of age

Seasonal influenza continues to cause significant morbidity and mortality, particularly for the elderly and immunocompromised. Current licensed influenza vaccines provide only partial protection even for immunocompetent hosts. Vaccine adjuvants can improve the magnitude and breadth of immune responses and there is considerable interest in identifying new adjuvants that can improve immune responses to seasonal influenza vaccines. This phase I, randomized, double-blind trial evaluated the safety and immunogenicity of one dose of 2018/2019 quadrivalent influenza vaccine (either Fluzone® or Flublok®) administered intramuscularly with or without one of two adjuvants (AF03 or Advax-CpG55.2). A total of 241 healthy adults aged 18-45 years were enrolled and randomized to 1 of 6 groups. Groups 1-3 received one dose of Fluzone® QIV 2018/2019 administered alone or with AF03 or Advax-CpG55.2 and Groups 4-6 received one dose of Flublok® QIV 2018/2019 alone or with one of these two adjuvants. All participants received Fluzone® or Flublok® QIV 2019/2020 ninety days later. Primary objectives were to evaluate safety and reactogenicity along with changes in hemagglutinin inhibition (HAI), neuraminidase inhibition (NAI) and neutralizing antibodies to 2018/2019 seasonal influenza antigens, comparing Day 1 and Day 29 titers. Secondary objectives evaluated the impact of adjuvants on immune responses after subsequent doses of unadjuvanted seasonal influenza vaccine and immunologic responses to heterologous influenza H1 and H3 antigens. Overall, the adjuvanted vaccines were safe and generated robust immune responses against both homologous and heterologous strains. Similar responses were seen across all six study arms. Both adjuvants were associated with qualitatively improved immune responses against some strains at varying timepoints, but results were inconsistent. There were no substantial differences in safety or reactogenicity identified between the study groups and all vaccine formulations were well tolerated. In this highly immunologically-experienced cohort, neither AF03 nor Advax-CpG55.2 demonstrated notable benefit when added to the seasonal influenza vaccine. (ClinicalTrials.gov ID# NCT03945825).

Advax-SM™-Adjuvanted COBRA (H1/H3) Hemagglutinin Influenza Vaccines

Adjuvants enhance immune responses stimulated by vaccines. To date, many seasonal influenza vaccines are not formulated with an adjuvant. In the present study, the adjuvant Advax-SM™ was combined with next generation, broadly reactive influenza hemagglutinin (HA) vaccines that were designed using a computationally optimized broadly reactive antigen (COBRA) methodology. Advax-SM™ is a novel adjuvant comprising inulin polysaccharide and CpG55.2, a TLR9 agonist. COBRA HA vaccines were combined with Advax-SM™ or a comparator squalene emulsion (SE) adjuvant and administered to mice intramuscularly. Mice vaccinated with Advax-SM™ adjuvanted COBRA HA vaccines had increased serum levels of anti-influenza IgG and IgA, high hemagglutination inhibition activity against a panel of H1N1 and H3N2 influenza viruses, and increased anti-influenza antibody secreting cells isolated from spleens. COBRA HA plus Advax-SM™ immunized mice were protected against both morbidity and mortality following viral challenge and, at postmortem, had no detectable lung viral titers or lung inflammation. Overall, the Advax-SM™-adjuvanted COBRA HA formulation provided effective protection against drifted H1N1 and H3N2 influenza viruses.

Comparative immunogenicity and safety of SpikoGen®, a recombinant SARS-CoV-2 spike protein vaccine in children and young adults: An immuno-bridging clinical trial

BACKGROUND

SpikoGen® is a recombinant subunit spike protein ectodomain vaccine manufactured in insect cells and formulated with the novel polysaccharide-based Advax-CpG55.2 adjuvant. This study aimed to compare the immunogenicity and safety of SpikoGen® vaccine in children, adolescents and young adults.

METHODS

This was a non-randomized, three-arm, open-label, parallel-group, immuno-bridging, non-inferiority trial to compare the immunogenicity and safety of a primary course of two intramuscular doses of SpikoGen® vaccine in children aged 5 to < 12 years, adolescents aged 12 to < 18 years and young adults aged 18 to 40 years. Children 5-12 years received a half dose of 12.5 μg spike protein, whereas the other groups received the full vaccine dose. Vaccine immunogenicity was evaluated via assessment of serum anti-spike and neutralizing antibodies 14 days after the second dose. Solicited adverse events were recorded for 7 days after each vaccination. Safety assessments including serious adverse events were continued through six months after the second dose in children and adolescents.

RESULTS

Two weeks after the second dose, seroconversion rates for neutralizing antibody levels were not significantly different for children (59.50 %), adolescents (52.06 %) and adults (56.01 %). The 95 % confidence interval of the difference in seroconversion rates between children and adults was within the prespecified non-inferiority margin of 10 % (-12 % to 5 %). SpikoGen® vaccine was well tolerated in all age groups with the most common solicited adverse events being injection site pain and fatigue which were generally transient and mild.

CONCLUSION

SpikoGen® vaccine was shown to be safe, well tolerated and immunogenic in children as young as 5 years of age, with non-inferior responses to those seen in adults. The Iranian FDA authorisation of SpikoGen® vaccine is now extended down to 5 years of age.

Advax-CpG55.2-adjuvanted monovalent or trivalent SARS-CoV-2 recombinant spike protein vaccine protects hamsters against heterologous infection with Beta or Delta variants

The ongoing evolution of SARS-CoV-2 variants emphasizes the need for vaccines providing broad cross-protective immunity. This study was undertaken to assess the ability of Advax-CpG55.2 adjuvanted monovalent recombinant spike protein (Wuhan, Beta, Gamma) vaccines or a trivalent formulation to protect hamsters againstBeta or Delta virus infection. The ability of vaccines to block virus transmission to naïve co-housed animals was also assessed. In naïve hosts, the Beta variant induced higher virus loads than the Delta variant, and conversely the Delta variant caused more severe disease and was more likely to be associated with virus transmission. The trivalent vaccine formulation provided the best protection against both Beta and Delta infection and also completely prevented virus transmission. The next best performing vaccine was the original monovalent Wuhan-based vaccine. Notably, hamsters that received the monovalent Gamma spike vaccine had the highest viral loads and clinical disease of all the vaccine groups, a potential signal of antibody dependent-enhancement (ADE). These hamsters were also the most likely to transmit Delta virus to naïve recipients. In murine studies, the Gamma spike vaccine induced the highest total spike protein to RBD IgG ratio and the lowest levels of neutralizing antibody, a context that could predispose to ADE. Overall, the study results confirmed that the current SpikoGen® vaccine based on Wuhan spike protein was still able to protect against clinical disease caused by either the Beta or Delta virus variants but suggested additional protection may be obtained by combining it with extra variant spike proteins to make a multivalent formulation. This study highlights the complexity of optimizing vaccine protection against multiple SARS-CoV-2 variants and stresses the need to continue to pursue new and improved COVID-19 vaccines able to provide robust, long-lasting, and broadly cross-protective immunity against constantly evolving SARS-CoV-2 variants.