A polyvalent virosomal influenza vaccine induces broad cellular and humoral immunity in pigs

Background Influenza A virus (IAV) is endemic in pigs globally and co-circulation of genetically and antigenically diverse virus lineages of subtypes H1N1, H1N2 and H3N2 is a challenge for the development of effective vaccines. Virosomes are virus-like particles that mimic virus infection and have proven to be a successful vaccine platform against several animal and human viruses. Methods This study evaluated the immunogenicity of a virosome-based influenza vaccine containing the surface glycoproteins of H1N1 pandemic, H1N2 and H3N2 in pigs. Results A robust humoral and cellular immune response was induced against the three IAV subtypes in pigs after two vaccine doses. The influenza virosome vaccine elicited hemagglutinin-specific antibodies and virus-neutralizing activity. Furthermore, it induced a significant maturation of macrophages, and proliferation of B lymphocytes, effector and central memory CD4.sup.+ and CD8.sup.+ T cells, and CD8.sup.+ T lymphocytes producing interferon-[gamma]. Also, the vaccine demonstrated potential to confer long-lasting immunity until the market age of pigs and proved to be safe and non-cytotoxic to pigs. Conclusions This virosome platform allows flexibility to adjust the vaccine content to reflect the diversity of circulating IAVs in swine in Brazil. The vaccination of pigs may reduce the impact of the disease on swine production and the risk of swine-to-human transmission. Keywords: Influenza A virus, Virosomal vaccine, Humoral immunity, Cellular immunity, Swine