Prevalence and phylogenetic characterization of HTLV-I isolates from Far Eastern Russia

A study was made of the prevalence and phylogenetics of human lymphotropic virus type I (HTLV-I) among the population of Far Eastern Russia. Serum samples from 3749 apparently healthy volunteers and blood donors, covering nine local ethnic groups and migrants from the European regions of the former Soviet Union, were collected in the Khabarovsk and Primorsk territories and on Sakhalin. Two commercial screening tests and three versions of the Western blot assay were used to detect antibodies; serologic data were confirmed by detection of HTLV-I sequences in the cell DNA with PCR. The survey revealed 11 infected individuals; all lived on Sakhalin, and 10 of them were Nivkhi people from the same settlement Nogliki. They exhibited an unusual immune response, since only in four cases the sera were consistently reactive in the Abbott and Serodia tests and contained a broad spectrum of gag-specific antibodies. For the other seven cases the presence of HTLV-I infection could be proved only with PCR. Phylogenetic analysis of the HTLV-I isolate from the Nivhki indicated that, according to the classification of Japanese researchers, it belonged to cosmopolitan subtype A and was closely related with its Japanese counterpart. These data suggested the spread of HTLV-I subtype A among Mongoloid populations.