Low genetic diversity of the Human T-cell Lymphotropic Virus (HTLV-1) in an endemic area of the Brazilian Amazon basin

Abstract

The Human T-cell Lymphotropic Virus (HTLV-1) is a Deltaretrovírus that was first isolated in the 1970s, and associated with Adult T-cell Leucemia-Lymphoma (ATLL), and subsequently to Tropical Spastic Paraparesis-Myelopathy (TSP/HAM). The genetic diversity of the virus varies among geographic regions, although its mutation rate is very low (approximately 1% per thousand years) in comparison with other viruses. The present study determined the genetic diversity of HTLV-1 in the metropolitan region of Belém, in northern Brazil. Blood samples were obtained from patients at the UFPA Tropical Medicine Nucleus between January 2010 and December 2013. The DNA was extracted and the PX region of the HTLV was amplified using nested PCR. The positive samples were then digested using the Taq1 enzyme for the identification and differentiation of the HTLV-1 and HTLV-2. The 5’LTR region of the positive HTLV-1 samples were amplified by nested PCR, and then sequenced genetically. The phylogenetic analysis of the samples was based on the maximum likelihood method and the evolutionary profile was analyzed by the Bayesian approach. Overall, 78 samples tested positive for HTLV-1, and 44 were analyzed here. The aA (cosmopolitan-transcontinental) subtype was recorded in all the samples. The following evolutionary rates were recorded for the different subtypes–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 mutations per site per year. The positive HTLV-1 samples tested in the present study were characterized by their low genetic diversity and high degree of stability.

Lymphotropic Viruses EBV, KSHV and HTLV in Latin America: Epidemiology and Associated Malignancies. A Literature-Based Study by the RIAL-CYTED

“…HTLV-1A has been found throughout South America [282,304,[484][485][486][487]. On the other hand, Amerindians with high HTLV-2 prevalence almost exclusively carry the HTLV-2B genotype [442,445,446,488,489].…”

Prevalence and Molecular Epidemiology of Human T-Lymphotropic Virus (HTLV) Infection in People Living With HIV/AIDS in the Pará State, Amazon Region of Brazil

“…Molecular studies based on the long terminal repeat (LTR) region have classified HTLV-1 in seven genetic subtypes (1a-1g) and HTLV-2 in four subtypes (2a-2d) (Vandamme et al, 1998;Gessain and Cassar, 2012). The HTLV-1a or Cosmopolitan subtype is the most prevalent worldwide (Gessain and Cassar, 2012), as well as in Brazil (Castro et al, 2018;Ribeiro et al, 2018) and in Pará state (Vallinoto et al, 2006;Nobre et al, 2018). The prevalence of HTLV coinfecting people living with HIV/AIDS (PLWHA) varies according to the studied population and the geographical region.…”

Molecular Biology and Diversification of Human Retroviruses

“…Research on the determinants of viral mutagenesis and evolution suggest that the diversification of retroviruses is driven by a complex interplay of internal and external factors. For example, while the error rate of HTLV-1 RT has been found to be several orders of magnitude lower than that of HIV-1 RT (147,148), studies analyzing virus replication suggest that the substitution rate of HTLV-1 is comparable with those observed in HIV-1 and HIV-2 (137,139,149,150). These results suggest that human retroviral evolution is driven by multiple factors beyond intrinsic replication errors alone.…”