Enhanced CD8+ T-cell response in mice immunized with NS1-truncated influenza virus

 Influenza viruses with truncated NS1 protein stimulate a more intensive innate immune response compared to their wild type counterparts. Here, we investigate how the shortening of the NS1 protein influence the immunogenicity of the conserved T-cellular epitopes of influenza virus. Using flow cytometry, we showed that the intraperitoneal immunization of mice with influenza virus encoding 124 N-terminal amino acid residues of the NS1 protein (A/PR8/NS124) induced higher levels of CD8+ T-cells recognizing immunodominant (NP366-374) and sub-immunodominant (NP161-175, NP196-210, HA323-337, HA474-483, NA427-433) epitopes compared to immunization with the virus expressing full-length NS1 (A/PR8/full NS). It is noteworthy that the response to the immunodominant influenza epitope NP366-374 was achieved with the lower immunization dose of A/PR8/NS124 virus compared to the reference wild type strain. Despite the fact that polyfunctional CD8+ effector memory T-lymphocytes simultaneously producing two (IFNγ and TNFα) or three (IFNγ, IL2 and TNFα) cytokines prevailed in the immune response to both viruses, the relative number of such T-cells was higher in A/PR8/NS124-immunized mice. Furthermore, we have found that polyfunctional populations of lymphocytes generated upon the immunization of mice with the mutant virus demonstrated an increased capacity to produce IFNγ compared to the corresponding populations derived from the A/PR8/full NS-immunized mice. Therefore, immunization with the attenuated influenza virus encoding truncated NS1 protein ensures a more potent CD8+ T-cell immune response.