The Effect of Epigenetic Variation on Vaccine Efficacy in Santa Catalina Island Foxes

Abstract

It has been shown that the fox population on Santa Catalina Island off the southern coast of California has little to no genetic diversity. A large outbreak of Canine Distemper Virus (CDV) swept through the population, causing this species of fox to be conservation reliant. One preservation effort is a widespread vaccination protocol against CDV, but when implementing this it was seen that some foxes respond to the vaccine while others do not, making conservation more difficult. We would expect all foxes to have practically identical phenotypes given their lack of genetic diversity, but since this is not the case, we look to the methylation on the genome, which affects how the genes are expressed, to explain the differences we see. To study this, I took a sample of 39 foxes and used Reduced Representation Bisulfite Sequencing to look at the methylation present on each fox’s genome. The foxes were broken up into two groups based on response to the CDV vaccine, with 19 foxes in the poor responder group and 20 in the good responder group. Differential methylation between the two groups was analyzed using R, and a gene set enrichment analysis was used to study the genes affected by these differentially methylated sites. Looking deeper into these differentially methylated genes, we start to see immune response genes being affected. Continued studying of the thousands of affected genes may allow us to better understand why the foxes express different responses to the CDV vaccine despite being genetically monomorphic.