Influenza is an important health issue due to the emergence of several pandemic strains during the past century: 1918 H1N1, 1957 H2N2, 1968 H3N2 and 2009 H1N1. Current licensed vaccines protect health by eliciting antibody responses against the viral surface glycoproteins hemagglutinin (HA) and neuraminidase (NA). However, influenza viruses evade host memory against HA and NA via antigenic drift and shift. Thus, vaccines are prepared annually containing three influenza strains predicted to be prevalent in the upcoming season. Upon identification of a possible pandemic strain, it may take six months to develop a new vaccine. The current licensed approach is insufficient. New candidate vaccines attempt to address these issues by targeting conserved epitopes including influenza matrix protein 1 (M1), matrix protein 2 (M2), and nucleoprotein (NP) to elicit long-term protection. Humoral immunity prevents the spread of virus, while T-cell immunity mediates viral clearance. T-cell immunity against conserved proteins is heterosubtypic, reacting with multiple strains of influenza virus. M1, M2, and NP-specific T-cell epitopes have all been shown to be cross-strain reactive. Furthermore, T-cell responses to M1 and NP are not only cross-reactive, but also immunodominant.
Last date updated on March, 2021