Elizabeth Uhl

University of Georgia

 

Human measles virus (HMV) and canine distemper virus (CDV) are closely related morbilliviruses. The first definitive description of canine distemper was made in 1748 by a Spanish scientist traveling in South America. No evidence of CDV infection in Pre-Columbian dog remains has been found and wild dog packs are too small for CDV to persist as an endemic infection. In contrast, the large dog populations in South American cities combined with the rampant measles epidemics post European colonization provided ideal conditions for HMV to jump to dogs and be maintained. Investigation of viral adaptation to host codon usage bias (CUB) revealed human CUB had a significantly higher relative adaptiveness for 6 of 7 CDV proteins than canine CUB.  In addition, optimization of CDV nucleotide sequences to either human or canine CUB increased their sequence identity for all but 2 proteins. Considering that viruses infecting humans show more adaptation to their host’s CUB than viruses infecting non-human mammalian hosts, these findings support the historical and evolutionary evidence that CDV arose from HMV. They also imply that further optimization of CDV to the mammalian CUB has the potential to enhance its ability to replicate in humans.