Molecular characterization of Human T-cell Lymphotropic Viruses 1 and 2 (HTLV-1 and HTLV-2) in samples from blood donation candidates in the state of Pará, Brazilian Amazon

The Human T-Lymphotropic Virus (HTLV) is a retrovirus belonging to the Retroviridae family and the Deltaretrovirus genus, which has a tropism for T lymphocytes. Despite being the first human retrovirus identified, knowledge about its infection remains limited, highlighting the need for further research, especially in Northern Brazil.. This study aimed to phylogenetically characterize HTLV-1 and HTLV-2 samples identified in blood donors from the state of Pará. The phylogenetic characterization was performed using DNA samples from blood donors at the HEMOPA Foundation, collected between January 2015 and December 2021. The 5'LTR regions of HTLV-1 and HTLV-2 were amplified using specific primers with Nested PCR. The amplified products were purified and sequenced using the dideoxynucleotide method, with the same primers used in the Nested PCR, for subsequent phylogenetic analysis and the construction of a sequence database, as well as deposits in GenBank. The phylogenetic analysis of the 5'LTR sequences of HTLV-1 from this study, compared with isolates available in GenBank, showed that 100 samples clustered with Cosmopolitan subtype isolates, Transcontinental subgroup, while 2 samples clustered with Cosmopolitan subtype isolates, Japanese subgroup. Regarding the phylogenetic analysis of HTLV-2 from this study in comparison with other GenBank isolates, most of the isolates clustered with strains described as HTLV-2c, and only three samples clustered with strains described as HTLV-2a. The epidemiological profile found in the analyzed samples consisted mainly of women, with an average age of 40 years and a low level of education. The molecular characterization of the viral genome provides information about the viral subtypes circulating in the population. This information may be important for increasing investments in screening and monitoring individuals infected with HTLV, thereby contributing to prophylactic practices related to infection and the dissemination of knowledge about HTLV.