The Non-Classical MHC-II Molecule H2-O (DO) is Required for Efficient Recovery from Influenza A Infection

H2-O (DO) is a non-classical MHC-II protein thought to regulate antigen presentation through inhibition of the catalytic peptide exchange factor H2-M (DM). H2-O−/− (DO-KO) mice have reduced diversity in the MHC-II peptide repertoire presented by peripheral and thymic antigen-presenting cells, as well as Treg populations with altered TCR repertoire and function. Absence of DO expression has been reported to result in increased neutralizing antibody titers, but a protective role for DO in an infectious disease model has not been reported. To determine whether lack of DO affects susceptibility to viral infection, we inoculated DO-KO and WT mice with a sublethal dose of influenza A (PR8). DO-KO mice exhibited a marked delay in recovery from weight loss after primary infection but not following rechallenge. Viral titers were not found to be significantly different between WT and DO-KO mice. After infection, DO-KO mice had reduced cellularity in spleen and draining lymph nodes, and reduced CD4 T cell responses across a variety of epitopes. Surprisingly, epitope-specific CD8 responses also were reduced, as were the numbers of NK and mast cells in lung after infection. These results demonstrate a role for DO in protection from influenza A infection in mice.