The human T-cell lymphotropic virus type 1 (HTLV-1) is a DELTARETROVIRUS which was first isolated from a blood sample of a patient with african american cutaneous T-cell lymphoma, in the mid 1970s; Hodgkin was later classified as leukemia / lymphoma adult T-cell (LLcTA) severe disease that affects T lymphocytes Subsequently, the virus was also associated with tropical spastic paraparesis / HTLV-associated myelopathy (HAM / TSP), character chronic and progressive causing damage mainly at the thoracic spinal cord. Their genetic diversity varies according to the region studied, and its mutation rate is very low (about 1% per thousand years) compared to other viruses. The objective of this study was to assess the genetic diversity of HTLV-1 in the metropolitan area of Belém, as well as the frequency of genotypes and the comparison of samples obtained with the sequences available in databases such as GenBank. We used blood samples collected from patients enrolled in the NMT / UFPA between the period January 2010 to December 2013. Then these samples were subjected to DNA extraction and amplification of HTLV PX region, using oligonucleotides inciciadores specific, from the PCR in two steps: internal and external (nested PCR). Positive samples then were subjected to enzymatic digestion of TaqI enzyme so that we could identify and differentiate the HTLV 1 and 2. Next, we performed amplification of the 5 'LTR region also by nested PCR positive samples, which, then were subjected to genetic sequencing. Using the method of maximum likelihood, we constructed a phylogenetic tree for the group display in clades of sequences in question. A Bayesian analysis (molecular clock) to visualize the evolutionary profile of the samples was also performed. The tests identified 78 samples positive for HTLV-1, of these, 44 were sequenced. The aa genotype was common in 100% of samples; the different subtypes had the following range rate and mutations per site per year: a- 2.10 -3; b- 2,69 . 10 -2; c- 6,23 . 10 -2; d- 3,08 . 10 -2; e- 6 . 10 -2; f- 1,78 . 10 -3; g- 2,2 . 10 -2 changes per site per year. It was then revealed a low genotypic diversity and a high genetic stability of the samples positive for HTLV-1 in the region.
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