A benign virus previously used as a marker in tracing human migration may be unreliable, according to researchers at Penn State. Results of this study also suggest that some viruses might be undergoing much higher rates of evolution than previously thought.
"The most genetically divergent human populations are in Africa," said Laura Shackelton, a postdoctoral researcher at Penn State's Center for Infectious Disease Dynamics. "But, in the case of this virus, strains from European communities appear to be the most divergent."
The human polyomavirus, or JCV, is a small double-stranded DNA virus that is thought to be primarily transmitted from parents to their children. Infection is usually asymptomatic unless a person has a weak immune system, in which case the virus can cause neurological disease.
There are more than 14 subtypes of the virus, each primarily associated with different human populations such as African, Japanese, South Asian, and European. Population geneticists have assumed that the virus has been with humans since their emergence from Africa.
"Because of this presumed codivergence with human populations, JCV has been widely used as a genetic marker for human evolution and migration," explained Shackelton, whose findings appear this month (October) in the Journal of Virology.
The researchers note that while previous studies of genetic variation have observed some differences between the distribution of JCV and human populations, the extent of the differences in their evolutionary histories has never been fully tested.
Shackelton and her colleagues analyzed 333 genetic sequences of the virus and reconstructed their evolutionary history. They then compared this history to the reconstructed history of human populations, based on mitochondrial DNA.
"If the virus had been with humans since we were a single population, and we have almost strictly transmitted it to our children, you may expect that as populations became isolated, the virus lineages diverged as well," Shackelton noted.