The role of toll-like receptor polymorphisms in susceptibility to canine distemper virus

Canine distemper virus (CDV) is a global multi-host pathogen of wildlife. Toll-like receptors (TLR) are key recognition structures of the innate immune system. To investigate host susceptibility to CDV, the presence of non-synonymous single nucleotide polymorphisms (SNPs) in the coding regions of TLR 2, 3, 4, 7 and 8 genes were investigated in two recent CDV outbreaks in South Africa. The first case consisted of five lions (Panthera leo), diagnosed with CDV. Four of the lions died following exposure to the virus. The second case consisted of six African wild dogs (Lycaon pictus) with CDV and one surviving African wild dog. TLR diversity showed a higher rate of polymorphism in the African wild dogs within each of the TLR loci compared to lions. A single amino acid change (Met527Thr) within the leucine rich repeat of TLR2 was observed in the single surviving lioness. This alteration resulted in a non-polar to polar group change, potentially influencing the expression and function of TLR2. No specific amino acid alterations could be associated with CDV susceptibility in the African wild dogs. This study provides a critical starting point in elucidating the mechanism involved in host immunity and therefore susceptibility towards CDV infection.