Molecular genetic diversity of EBV and HHV6V: impact on viral load in coinfection

Aim. The aim of the study was to investigate molecular genetic diversity of Epstein-Barr virus (EBV) and human herpes virus 6B (HHV6B) and its influence on viral load in children of Nizhny Novgorod region during co-infection. Materials and methods. 246 children with mononucleosis-like syndrome (MLS) and 118 healthy virus-carriers were examined. Based on serological and PCR studies, etiological agent in children with MLS and EBV and/or HHV6B carriage in healthy children were established, EBV and/or HHV6V DNA content in blood leukocytes was determined. EBV and HHV6B genotyping was performed based upon amino acid sequence of EBV LMP-1 protein fragment and nucleotide sequence of HHV6B U90 gene fragment. Results. EBV + HHV6B manifest coinfection or healthy carriage was detected in 31% of children with MLS and 34% of healthy children, respectively. Circulation of 4 EBV genovariants (B95-8, NC, China-1, and MEDneg) and 4 HHV6B genovariants (GV1a, GV2a, GV2b, and GV2e) was detected under monoinfection, 11 combinations of virus genovariants – under coinfection. Under monoinfection and coinfection, EBV/B95-8, EBV/NC, HHV6B/GV2b and HHV6B/GV2e genovariats dominated. In children with MLS, EBV DNA content decreased by 230-276 copies/10 5 cells under EBV/ B95-8 coinfection compared to monoinfection regardless of HHV6B genovariants. Under EBV/B95-8 + HHV6B/GV2b or EBV/B95-8 + HHV6B/GV2e coinfection HHV6B viral load decreased by 1.3 copies/10 5 cells. Under EBV/B95-8 + HHV6B/GV1a and EBV/B95-8 + HHV6B/GV2e coinfection HHV6B and EBV DNA content interconnected in linear-logarithmic manner. Conclusion. Molecular genetic polymorphism of EBV and HHV6B influenced on viral DNA content in blood leukocytes of children with MLS during coinfection.