CD14 plays a limited role during influenza A virus infection in vivo.

Influenza A is a single stranded (ss)RNA virus that can cause upper respiratory tract infections that in rare cases may progress to pneumonia. Toll-like receptors (TLRs) and CD14 are receptors which recognize viral proteins and nucleic acid of several viruses. CD14 is required for influenza-induced cytokine production during infection of mouse macrophages. In addition, CD14 was shown to bind ssRNA, suggesting an important role for CD14 during infection with influenza. To investigate the role of CD14 during influenza pneumonia we inoculated WT and CD14 KO mice with a non-lethal dose of a mouse adapted strain of influenza A. CD14 KO mice displayed a reduced viral load in the lungs, 2 and 14 days after infection with influenza. Pulmonary cytokine production in CD14 KO mice was reduced at day 2 and elevated at day 8 compared to WT mice. CD14 deficiency did not influence lymphocyte recruitment or lymphocyte activation in lungs and draining lymph nodes 8 days after infection. These data show that CD14 plays a limited role in host defense against infection with influenza.