Sin Nombre virus pathogenesis in Peromyscus maniculatus

Sin Nombre virus (SNV), a member of the Hantavirus genus, causes acute viral pneumonia in humans and is thought to persistently infect mice. The deer mouse, Peromyscus maniculatus, has been identified as the primary reservoir host for SNV, To understand SNV infection of P. maniculatus, we examined wild deer mice for localization of viral antigens and nucleic acid. Morphologic examination consistently revealed septal edema within lung tissue and mononuclear cell infiltrates in portal areas of the liver. Immunohistochemical analysis of SNV-infected deer mice identified viral antigens within lung, liver, kidney, and spleen. The lungs consistently presented with the highest levels of viral antigen by immunohistochemistry and with the highest levels of nucleic acid by reverse transcriptase (RT) PCR. The mononuclear cell infiltrates surrounding liver portal triads were positive for SNV antigens in addition to resident macrophages in liver sinuses. Spleen tissue contained antigens in both the red pulp and the periartereolar region of the white pulp. The kidney presented with no gross pathology, although antigens could be localized to glomeruli. Virus antigen levels within the kidney were highest in deer mice that did not have antibodies to SNV but contained viral nucleic acid detectable by RT PCR. Since transmission is thought to occur via urine, our results suggest that virus transmission may be highest in the early stages of infection. In addition, these results indicate that SNV does cause some pathology within its reservoir host.