Purpose: This study sought to determine the effects of microneedle coating formulation, drying time and storage time on antigen stability and in vivo immunogenicity of influenza microneedle vaccines.
Methods: The stability of inactivated influenza virus vaccine was monitored by hemagglutination (HA) activity and virus particle aggregation as a function of storage time and temperature with or without trehalose. In vivo immunogenicity of inactivated influenza vaccines coated onto microneedles was determined in mice by virus-specific antibody titers and survival rates.
Results: In the absence of trehalose, HA activity decreased below 10% and to almost zero after 1 h and 1 month of drying, respectively. Addition of trehalose maintained HA activity above 60% after drying and above 20% after 1 month storage at 25°C. Loss of HA activity generally correlated with increased virus particle aggregation. Administration of microneedles coated with trehalose-stabilized influenza vaccine yielded high serum IgG antibody titers even after 1 month storage, and all animals survived with minimal weight loss after lethal challenge infection.
Conclusions: Inactivated influenza virus vaccine coated on microneedles with trehalose significantly improved the HA activity as well as in vivo immunogenicity of the vaccine after an extended time of storage.