The Effect of MHC Genes on Vaccine Response in Santa Catalina Island Foxes

Abstract

The island fox (Urocyon littoralis), descendant of the mainland gray fox (Urocyon cinero argenteus), has six recognized subspecies, each inhabiting a different Channel Island of California. A combination of factors such as low genetic diversity, lack of previous exposure to common canine viruses, and long history of isolation left the island foxes vulnerable to an epizootic. A canine distemper virus (CDV) outbreak on Santa Catalina Island in 1999 decimated most of the population (Timm et al., 2009). Intervention by the Catalina Island Conservancy, especially through efficient vaccination protocols, helped to save the population (King et al., 2014). Yet, even though there is a large genetic component to vaccine-induced immune response (Kimman et al., 2007), these fairly genetically monomorphic animals exhibited notable variability in their immune responses. The role that MHC plays in immunity, coupled with the fact that these foxes actually retain considerable variability at MHC loci (Agudo et al., 2011), lead me to believe that MHC genes may be a significant component in vaccine response. I conducted logistic regressions to see whether or not genotypes at certain MHC genes could predict for high vs low vaccine response, a binary outcome that I denoted as individuals with peaks titer levels of ≥32 and <32, respectively. My tests found associations between genotypes at two MHC Class II genes, CFA12-9 and CFA12-21 (p=0.0143 and p=0.020).