SEQUENCE-ANALYSIS OF HUMAN T-CELL LYMPHOTROPIC VIRUS TYPE-I STRAINS FROM SOUTHERN INDIA - GENE AMPLIFICATION AND DIRECT SEQUENCING FROM WHOLE-BLOOD BLOTTED ONTO FILTER-PAPER

Human T cell lymphotropic virus type I (HTLV-I) infection in India has been found to be associated with adult T cell leukaemia/lymphoma (ATL L) and HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/ TSP) among life-long residents of southern India. To examine the heter ogeneity of HTLV-I strains from southern India and to determine their relationship with the sequence variants of HTLV-I from Melanesia, 1149 nucleotides spanning selected regions of the HTLV-I gag, pol, env and pX genes were amplified and directly sequenced from DNA extracted fro m whole blood blotted onto filter paper and from peripheral blood mono nuclear cells, obtained from one patient with HAM/TSP, two with ATLL a nd eight asymptomatic carriers from Andhra Pradesh, Kerala and Tamil N adu. Sequence alignments and comparisons indicated that the 11 HTLV-I strains from southern India were 99.2% to 100% identical among themsel ves and 98.7% to 100% identical to the Japanese prototype HTLV-I ATK. The majority of base substitutions were transitions and silent. No fra meshifts, insertions, deletions or possibly disease-specific base chan ges were found in the regions sequenced. The observed clustering of th e Indian HTLV-I strains with those from Japan, as determined by the ma ximum parsimony method, suggested a common source of HTLV-I infection with subsequent parallel evolution. Amplification of DNA from blood sp ecimens collected on filter paper may be useful for the study of other blood-borne pathogens.