Molecular Genetic Diversity of HHV6B Among Clinically Healthy Virus Carriers in Russian Industrial City

The molecular genetic polymorphism of human herpes virus 6B (HHV6B) circulating among healthy virus carriers of a large city in the European part of Russia (Nizhny Novgorod) was studied. Using sequencing, we established the nucleotide sequences of the U90B gene fragment of HHV6B isolated from samples of peripheral blood leukocytes and saliva of clinically healthy virus carriers. The virus genovariant was determined according to the previously developed subspecies classification of HHV6B. The circulation of four HHV6B genovariants with different pathogenetic potential was revealed: dominant GV2e and GV2b and minor GV1a and GV2a. There was the difference of HHV6B genovariant structure in subjects of different age: among healthy virus carriers over 35 years old, only one HHV6B genovariant (GV2e) was detected, among people from 8 to 35 years old — three genovariants (GV2e, GV2b, GV1a), among children under 8 years old — all four genovariants. Phylogenetic modeling of the HHV6B population dynamics in the territory of Nizhny Novgorod was performed. The most probable model of the spread of virus genovariants in the population was established, suggesting the initial circulation of GV2e and successive imports of genovariants GV2b (approximately 1979), GV1a (1996) and GV2a (2007). According to this model, for most healthy virus carriers after HHV6B infection in early childhood, the genovariant of the virus does not change during the rest of the life. However, a case of a healthy virus carrier with two genovariants of HHV6B localized in different compartments (blood leukocytes and saliva) was established.