Immunization with high epitope density of M2e derived from 2009 pandemic H1N1 elicits protective immunity in mice

► We evaluate the antigenicity and protection of the 2009 H1N1 M2e epitope. ► We constructed three antigens containing 2, 4, 8 copies of this M2e epitope. ► Higher epitope densities evoked more intensive and more diverse antibody response. ► Intranasal immunization protects mice from lethal influenza virus challenge.