Journal of Animal Research

To control avian influenza infection in chickens, whole inactivated influenza viruses (IIV) are used as vaccine. These vaccines provide immunity only to antigenically matched strains or homologous viruses. Influenza viruses circulating in field undergo spontaneous antigenic changes in head domain, thereby escape from the preexisting vaccine immunity. Therefore, annual reformulation of vaccines are needed to compensate the antigenic change. To overcome this issue, universal flu vaccines are preferred which may protect against antigenically unmatched strains or heterologous viruses. Apart from natural infection, IIV also may induce stalk reactive antibodies but in meager level. Stalk domain of haemagglutinin is one of the target for the development of universal vaccine as it is conserved among influenza viruses. The antigenic changes are rare in stalk rather than head domain. Designing of stalk is challenging in prefusion conformation as it requires skilled knowledge. In the present study, we have tested the reactivity of in vitro expressed HA stalk protein with sera of chickens immunized with different subtypes of inactivated influenza virus vaccines. Our result showed that the HA stalk is reactive with sera against group I viruses mostly because our stalk belongs to the same group I. Hence, we concluded that in-vitro expressed HA stalk protein used in this study is conformationally stable and mimics the HA stalk as present in the intact viruses. This study provides hope for development of universal influenza vaccine in chicken is possible if the stalk immunogen is designed better.