Epstein–Barr virus (Herpesviridae: <i>Lymphocryptovirus</i>) types 1 and 2 and other viral markers in patients with nasopharyngeal carcinoma in two geographically and ethnically distinct regions of Russia

Introduction. The discovery of two types of EpsteinBarr virus (EBV) (EBV-1 and EBV-2) that have different biological properties stimulated the search for neoplasms associated with each type of the virus. The aim of the work is to study the nature of the association of nasopharyngeal cancer (NPC) with EBV-1 and EBV-2, serological activity for each viral type and the concentration of EBV DNA in the blood plasma of two gender, age and ethnic groups of NPC patients that represent geographically and climatically different regions of Russia,. Materials and methods. In the blood plasma of patients with NPC and other non- EBV associated tumors of oral cavity (OTOCEBV) from the North Caucasian (NCFD) and Central (CFD) Federal Districts of Russia, the types of EBV and the concentration of viral DNA were determined using respectively nested and real time PCR; titers of IgG and IgA antibodies to viral capsid antigen (VCA) were measured in indirect immunofluorescence assay. Results. The blood plasma samples testing showed that NPC and OTOCEBV patients were infected with both types of EBV in approximately equal proportions. In two groups of NPC patients infected with one of the virus types only, EBV-1 or EBV-2, respectively, no statistically significant differences were found between the geometric mean values of IgG and IgA anti-EBV antibody titers and viral DNA concentrations in blood plasma. The distribution of virus types was not affected by either patient gender or ethnogeographic origin. The difference was found only between age groups: EBV-2 dominated in NPC patients up to 60 years, and EBV-1 was prevalent in patients over 60 years. Conclusion. The lack of the predominance of one of EBV types in NPC patients that are the representatives of different ethnic groups from geographically and climatically different regions, suggests that none of these factors play an important role in the NPC carcinogenesis. Evidently, each type of EBV, EBV-1 or EBV-2, if the necessary conditions arise, are able to exhibit its oncogenic potential to initiate tumor development.