Development of a universal group 2 influenza virus vaccine using chimeric hemagglutinin constructs

The stalk domain of the hemagglutinin (HA) has become the prime target for universal influenza virus vaccine development in the last few years. Unlike the HA head domain, the immunosubdominant stalk domain is conserved to a higher level within each influenza virus HA group. Sequential vaccination with chimeric HA (cHA) vaccine constructs consisting of the same HA stalk and exotic head domains has proven to re-direct the immune response towards the stalk domain. This vaccination concept provides the basis for the development of more broadly cross-protective vaccines that are less affected by antigenic drift and shift, one of the main drawbacks of currently marketed influenza vaccines. Most influenza virus vaccines are licensed as inactivated split vaccines. They are manufactured based on HA content with little to no information and standardization of neuraminidase (NA) content. Virus inactivation is generally performed with alkylating agents such as formalin (FA) or β-propiolactone (βPL), rendering the virus unable to infect or replicate. Though safe, whole inactivated virus vaccines can be highly reactogenic. Virus splitting with detergents like sodium deoxycholate (SDCO) and Triton X-100 (TX-100), which dissociate the virus into smaller parts while maintaining a good immunogenicity profile, are typically employed. To date, there are several studies assessing the effect of a variety of inactivating and splitting agents on influenza viruses, but little is known about the impact of combining these agents on HA stalk conformation and NA activity. Please click Download on the upper right corner to see the full abstract

A universal Influenza B vaccine using mosaic-hemagglutinin vaccine candidates

Influenza viruses undergo antigenic changes in the immuno-dominant hemagglutinin (HA) head domain, necessitating annual re-formulation of and re-vaccination with seasonal influenza virus vaccines for maintaining the protection. We previously synthesized mosaic HA (mHA) proteins of influenza B viruses which redirect the immune response towards the immuno-subdominant conserved epitopes of the B virus HA via sequential immunization. As ~90% of current influenza virus vaccines are manufactured using the inactivated virus platform, we generated and sequentially vaccinated mice with inactivated influenza B viruses displaying either the homologous (same B HA backbones) or the heterologous (different B HA backbones) mosaic HAs. Both approaches induced long-lasting and cross-protective antibody responses showing strong antibody-dependent cellular cytotoxicity (ADCC) activity. Thereafter, we tested different inactivation methods and adjuvants to increase the cross-protection against phylogenetically distant influenza B viruses from both lineages. The use of CpG 1018 or AddaVax boosted the humoral immune response and protection when combined with any inactivation method. Beta-propiolactone (BPL) inactivation was the best method, with high serum HA antibodies levels that correlated with optimal protection in BALB/C mice challenge studies. We believe that these B virus mHA vaccine candidates represent a major step towards a universal influenza B virus vaccine. Please click Download on the upper right corner to see the full abstract

Bioprocess development for universal influenza vaccines based on inactivated split chimeric and mosaic hemagglutinin viruses

Seasonal influenza viruses account for 1 billion infections worldwide every year, including 3–5 million cases of severe illness and up to 650,000 deaths. The effectiveness of current influenza virus vaccines is variable and relies on the immunodominant hemagglutinin (HA) and to a lesser extent on the neuraminidase (NA), the viral surface glycoproteins. Efficient vaccines that refocus the immune response to conserved epitopes on the HA are needed to tackle infections by influenza virus variants. Sequential vaccination with chimeric HA (cHA) and mosaic HA (mHA) constructs has proven to induce immune responses to the HA stalk domain and conserved epitopes on the HA head. In this study, we developed a bioprocess to manufacture cHA and mHA inactivated split vaccines and a method to quantify HA with a prefusion stalk based on a sandwich enzyme-linked immunosorbent assay. Virus inactivation with beta-propiolactone (βPL) and splitting with Triton X-100 yielded the highest amount of prefusion HA and enzymatically active NA. In addition, the quantity of residual Triton X-100 and ovalbumin (OVA) was reduced to very low levels in the final vaccine preparations. The bioprocess shown here provides the basis to manufacture inactivated split cHA and mHA vaccines for pre-clinical research and future clinical trials in humans, and can also be applied to produce vaccines based on other influenza viruses

Enhancing the protection of influenza virus vaccines with BECC TLR4 adjuvant in aged mice

Abstract Influenza A virus (IAV) is a leading cause of respiratory disease worldwide often resulting in severe morbidity and mortality. We have previously shown that the Bacterial Enzymatic Combinatorial Chemistry (BECC) adjuvants, BECC438 and BECC470, formulated with an influenza virus hemagglutinin (HA) protein vaccine, offer greater protection from influenza virus challenge in mouse respiratory models using adult mice than standard HA:adjuvant combinations. In this study, we determined that immunization with HA + BECC adjuvants also significantly broadened the epitopes targeted on HA as compared with other adjuvants, resulting in increased titers of antibodies directed against the highly conserved HA stalk domain. Importantly, we demonstrate that BECC470 combined with an influenza virus HA protein antigen in a prime-only immunization regimen was able to achieve complete protection from challenge in a ~ 12-month-old mouse aged model. Together, this demonstrates the heightened protection provided by the BECC470 adjuvant in an influenza virus vaccine model and shows the enhanced immune response, as compared to other adjuvants elicited by the formulation of HA with BECC470