The whey acidic protein family member, WFDC1/ps20 is a permissivity factor in HIV infection. Herein we describe a contrasting role for ps20 in limiting MHV-1 infection. Intranasal MHV-1 infection produces a respiratory infection in mice. Using ps20 knockout mice we provide evidence that intranasal MHV-1 infection results in increased lung viral titers in ps20(-/-) compared to ps20(/) mice. Roles for ps20 in regulating expression of neutrophil-specific chemotactic factors, thereby potentially modulating neutrophil migration, and in modulating neutrophil susceptibility to MHV-1 infection.

> 95% as determined by Tris-Bis PAGE; > 95% as determined by HPLC