Genome Study Highlights Evolutionary Factors Behind Human Cytomegalovirus Diversity

Researchers at the University College London, the University of Montreal, and the Great Ormand Street Hospital for Children National Health Service Foundation Trust take a look at the enhanced genome diversity found in the human cytomegalovirus (CMV) herpesvirus in a paper appearing in Proceedings of the National Academy of Sciences. By bringing together available whole-genome sequences for 259 CMV isolates from Europe, the Middle East, Africa, North America, Asia, and Australia — including sequences for dozens of CMV strains found in immunocompromised individuals — the team tracked down a set of 74 multiallelic regions in the CMV genome that were marked by some two to eight variable alleles apiece. When they considered factors affecting the conserved and variable portions of the genome overall, meanwhile, the authors saw signs of population structure that reflected geography over much of the genome, though a few dozen genome regions with roles in immunomodulation or other core functions were free from this geographic influence — a pattern they attributed to potential balancing selection. "We demonstrate that CMV diversity is influenced by two distinct evolutionary forces," they write, adding that "[t]hese insights into CMV evolution are likely to provide insights into virus biology and inform the development of drugs and global vaccines."