Seasonality in Immune System Function of Deer Mice (Peromyscus maniculatus)

Sin Nombre virus (SNV) is a North American hantavirus that causes Hantavirus Pulmonary Syndrome (HPS) in humans, an acute and rapidly progressing disease with high (~40%) mortality rates. Deer mice (Peromyscus maniculatus) are the primary mode of human HPS infection; humans become infected with SNV via inhalation of virus particles shed through deer mouse excrement. The incidence of human infection with HPS follows distinct seasonal patterns; HPS cases peak during spring and reach annual lows during winter.  In contrast to patterns of human infection, SNV infection in deer mice is chronic; the virus is maintained in their tissues for life.  Recent studies have suggested that immune system function of wild mammals can be seasonally variable.  These findings have potentially significant implications for the deer mouse – SNV system, as deer mice with seasonally reduced immunocompetence may shed greater amounts of SNV, increasing the likelihood of human SNV infection.  Therefore, the objectives of our study are to determine 1) the variability of immune responses of deer mice to SNV across seasons and 2) how seasonal fluctuations in the immune response to SNV impacts their innate, inflammatory immunocompetence. In a capture-mark-recapture study, we are collecting blood samples from individual deer mice repeatedly from April to November. To record fluctuations in the immune response to SNV, we will quantify SNV antibody titers and levels of SNV viral RNA in blood.  To assess the inflammatory immune response, we will measure serological levels of C-reactive protein, a general marker of inflammation.