Enhanced Immunogenicity of a Whole-Inactivated Influenza A Virus Vaccine Using Optimised Irradiation Conditions.

Eve Victoria Singleton,Justin Bryan Davies,Timothy Raymond Hirst,Shannon Christa David,Mohammed Alsharifi,Chloe Jayne Gates

doi:10.3389/fimmu.2021.761632

Abstract

Influenza A virus presents a constant pandemic threat due to the mutagenic nature of the virus and the inadequacy of current vaccines to protect against emerging strains. We have developed a whole-inactivated influenza vaccine using γ-irradiation (γ-Flu) that can protect against both vaccine-included strains as well as emerging pandemic strains. γ-irradiation is a widely used inactivation method and several γ-irradiated vaccines are currently in clinical or pre-clinical testing. To enhance vaccine efficacy, irradiation conditions should be carefully considered, particularly irradiation temperature. Specifically, while more damage to virus structure is expected when using higher irradiation temperatures, reduced radiation doses will be required to achieve sterility. In this study, we compared immunogenicity of γ-Flu irradiated at room temperature, chilled on ice or frozen on dry ice using different doses of γ-irradiation to meet internationally accepted sterility assurance levels. We found that, when irradiating at sterilising doses, the structural integrity and vaccine efficacy were well maintained in all preparations regardless of irradiation temperature. In fact, using a higher temperature and lower radiation dose appeared to induce higher neutralising antibody responses and more effective cytotoxic T cell responses. This outcome is expected to simplify irradiation protocols for manufacturing of highly effective irradiated vaccines.

Highlights

Influenza A virus (IAV) is a major health concern and causes significant morbidity and mortality on a global scale
No virus infectivity was detected in any of the Madin-Darby canine kidney (MDCK) monolayers treated with irradiated preparations for all 3 passages, whereas replication of live virus was amplified at each passage (Figure 1)
IAV is inactivated using g-irradiation, and the heterosubtypic protection is mediated by induction of cross-reactive cytotoxic T cell responses [5]

Summary

Introduction

Influenza A virus (IAV) is a major health concern and causes significant morbidity and mortality on a global scale. Vaccination remains the most effective method to combat IAV infection, though current inactivated vaccines have major valency and efficacy limitations. Existing formulations consist of purified IAV surface proteins haemagglutinin (HA) and neuraminidase (NA) of 2 IAV strains and Enhanced Immunogenicity of IAV Vaccine an additional 1 or 2 influenza B virus strains predicted to circulate in a given year. Whilst effective at protecting against ‘vaccine-included’ strains, the immune responses induced by current IAV vaccines are antibody-based only and provide minimal protection against strains not included in a given formulation (i.e. non-vaccine strains). Current IAV vaccines are ineffective against newly emerging seasonal strains and novel pandemic strains and must be updated and redistributed every year due to the highly mutagenic nature of IAV surface proteins

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