A new study reveals that B cells can produce antibodies against the H1N1 influenza virus that also neutralize various other influenza strains, marking a development that could inform research into potential universal flu vaccines. The findings showed that the antibodies targeted two conserved regions of the virus - the cause of the 2009 swine flu pandemic - and that transfers of the antibodies protected mice from lethal infection. The work suggests that vaccines that target the two sites might be able to protect against a broader array of flu strains. Influenza is one of humanity's greatest microbial foes, being responsible for both seasonal flu and more severe flu pandemics that pose major threats to global health. Current vaccines for seasonal flu induce antibodies against the "head" region of hemagglutinin, the major surface antigen on influenza viruses. However, this strategy only protects against a few strains of influenza, and these antigen sites mutate frequently enough that a new vaccine is needed each year. Searching for better vaccine targets, Jenna Guthmiller and colleagues studied the properties of antibodies from memory B cells exposed to the 2009 pandemic H1N1 influenza virus. They saw that the B cells produced antibodies that targeted the receptor-binding site or lateral patch epitopes, two regions of the hemagglutinin head that are conserved across many strains of influenza. As a result, these antibodies neutralized most H1 influenza viruses the researchers tested, and antibodies against the lateral patch also reacted to the H3N2 strain and to influenza B viruses. Furthermore, transfers of the antibodies protected mice from lethal doses of H1N1 influenza, and some of the lateral patch antibodies also neutralized a natural, recent flu strain with mutations in a major antigen site.
