Impact of an amino acid deletion detected in the hemagglutinin (HA) antigenic site of swine influenza A virus field strains on HA antigenicity

Influenza A viruses circulating in pigs are of major concern because they can reduce herd productivity and sometimes infect humans. Understanding how these viruses change their surface proteins is essential for predicting their evolution and preventing outbreaks. This study focuses on swine influenza A virus isolated from pig farms in Japan and investigates the effect of a specific amino acid deletion in the hemagglutinin protein, which plays a key role in viral recognition by the host immune system. The results show that this deletion does not greatly affect virus growth but markedly alters how the immune system recognizes the virus. Such antigenic changes may allow the virus to evade existing immunity in pig populations and potentially increase the risk of transmission to humans. These findings underscore the need for continued surveillance of such variants in pigs and for future studies to evaluate their possible zoonotic implications.