Antibody responses and cross protection against lethal influenza A viruses differ between the sexes in C57BL/6 mice.

A mouse model was used to determine if protective immunity to influenza A virus infection differs between the sexes. The median lethal dose of H1N1 or H3N2 was lower for naive females than males. After a sublethal, primary infection with H1N1 or H3N2, females and males showed a similar transient morbidity, but females generated more neutralizing and total anti-influenza A virus antibodies. Immunized males and females showed similar protection against secondary challenge with a homologous virus, but males experienced greater morbidity and had higher lung viral titers after infection with a lethal dose of heterologous virus. Females develop stronger humoral immune responses and greater cross protection against heterosubtypic virus challenge.