An Ad-Vectored H3N8 Avian influenza vaccine induces potent immunity and protection in mice and chickens.

Abstract

In recent years, the H3N8 avian influenza virus (AIV) has circulated among poultry in China and caused human infections, posing challenges to public health. Therefore, there is an urgent need to develop a vaccine against the H3N8 AIV. A recombinant vaccine expressing H3N8 viral hemagglutinin (HA) was constructed using human adenovirus type 5 as a vector and designated as rAd-HA. BALB/c mice and specific pathogen-free (SPF) chickens were immunized via intramuscular (i.m.) injection or intranasal (i.n.) inoculation, respectively. The vaccine's immunogenicity and protective efficacy were systematically evaluated. The results showed that the vaccine could induce robust humoral and cellular immune responses. Both mice and chickens immunized via i.m. or i.n. routes exhibited hemagglutination inhibition (HI) titers of ≥ 64. IFN-γ expression levels were significantly upregulated in mice. Additionally, both intranasally immunized mice and chickens produced mucosal immune antibodies secretory IgA (sIgA). Challenge protection experiments revealed that the vaccine effectively protected BALB/c mice against lethal viral doses, suppressing viral replication and tissue damage. These findings demonstrate that rAd-HA provides robust protection for both mammals and poultry, offering a powerful tool for H3N8 prevention and control.