A call to cellular & humoral arms: enlisting cognate T cell help to develop broad-spectrum vaccines against influenza A.

Influenza A is an important cause of morbidity and mortality worldwide. In the United States alone influenza kills 30,000 to 50,000 people in a non-epidemic year and significantly more in an acute epidemic.(1) An emerging pandemic influenza virus, such as H5N1, could have a devastating economic and social impact. The Surgeon General estimates that at least 43 million Americans, especially those younger than 1 and older than 60, are at risk of death from influenza. Antigenically distinct influenza virus strains emerge regularly, mandating changes in influenza vaccine antigenic composition. Consequently, the immunity engendered by the conventional influenza vaccines is relevant only for a short time. However, by incorporating conserved influenza T cell epitopes, it may be possible to develop more immunogenic, broader-spectrum vaccines that may be efficacious over a longer period. This review summarizes the critical components of effective influenza vaccines, a rational vaccine design approach, and the pertinent influenza immunology.