Antiviral immunity induced by recombinant nucleoprotein of influenza A virus. I. Characteristics and cross-reactivity of T cell responses

The gene for the nucleoprotein of the A/NT/60/68 influenza virus was expressed in bacteria and the recombinant protein purified. Lympho node cells from mice immunized with recombinant nucleoprotein proliferated in response to in vitro stimulation with a range of type A influenza virus. Proliferation was inhibited by mAb to CD4 and class II MHC gene products. IFN-γ was produced and type-specific CTL were generated in stimulated cultures of immune lymph node cells. These CTL were CD4⁺ and restricted to class II MHC gene products. Immunization with recombinant nucleoprotein generated Th cells in vivo as measured by the ability to generate an accelerated response to hemagglutinin after challenge with inactivated virus. The results are discussed with reference to a cross-reactive vaccine against influenza.