Distribution of Human T Cell Lymphotropic Virus Type 1 (HTLV-1) Subtypes in Brazil: Genetic Characterization of LTR and Tax Region

Abstract

We report the molecular and epidemiological characterization of 128 human T cell lymphotropic virus type 1 (HTLV-1) isolates from Brazilian patients with different clinical manifestations of the infection. Thirty-two percent of the patients were asymptomatic, 44% had HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), and 23% had adult T cell leukemia/lymphoma (ATLL). Phylogenetic analysis performed using part of the LTR region of the viral genome revealed that all Brazilian isolates belonged to the Cosmopolitan subtype, with the following distribution within the Transcontinental subgroup: 81.6% within the Latin American cluster and 15.8% outside the Latin American cluster. Two isolates belonged to the Japanese subgroup. Molecular analysis of the tax region showed a high nucleotide similarity ( approximately 99%) with 41 prototype sequences, including the ATK-1 isolate. The mean number of nucleotide substitutions ranged from 1 to 8. Five specific nucleotide substitutions, C7401T, T7914C, C7920T, C7982T, and G8231A, were highly conserved among the Brazilian isolates (79.6%), with a frequency ranging from 81.6% to 100% in the sample group and from 18.4% to 24.1% in the prototypes used, suggesting the existence of a molecular signature. These changes were not correlated with a specific clinical status of the patients and could be a molecular characteristic of the HTLV-1 strains that circulate in Brazil.

Tax Gene Characterization of Human T-Lymphotropic Virus Type 1 Strains from Brazilian HIV-Coinfected Patients

“…10 Corroborating these data, another study from Sã o Paulo showed the same pattern of mutations and a lack of association between the tax genotype and disease progression. In addition to some regions of Brazil being considered endemic for HTLV-1 infection, 4 Brazil is considered epidemic for HIV/AIDS, with prevalence rates of 0.3% to 0.6% 13 ; as a result, HIV/HTLV-1 coinfection has been described in this country, with prevalence rates varying according to the geographic area.…”

“…In fact, this subgroup was detected in some individuals from southeastern Brazil. 10 On the basis of the molecular analysis of the tax gene, HTLV-1 strains were classified into two genotypes, taxA and taxB, whose association with clinical disease was suggested.…”

Ocular lesions in HTLV-1 infected patients from Salvador, State of Bahia: the city with the highest prevalence of this infection in Brazil

“…Clinical Diagnostic Inc. Raritan, �ew Jersey, USA) were confirmed and discriminated between HTLV-1 and HTLV-2 using Western Blot (HTLV Blot 2.4; Genelabs, Singapore). Polymerase Chain Reaction (PCR) analysis was performed in samples with undetermined results according to the technique described elsewhere 13 . The diagnosis of HAM/TSP was determined according to the WHO guidelines 28 A full ophthalmologic examination was performed, including visual acuity measurement by Snellen eye chart, with optical correction, optical motility, applanation tonometry, biomicroscopy of the anterior and posterior chambers, binocular indirect ophthalmoscopy with or without depression, in both eyes and intraocular pressure.…”

Sexual transmission of human T-cell lymphotropic virus type 1

“…The subtypes do not vary in pathogenicity and most likely refl ect the geographical origins and migrations of ancient populations [21][22][23] . In addition, genomic sequencing has confi rmed the transmission of HTLV-1 from infected spouses to uninfected spouses by revealing identical sequences in seropositive individuals and those spouses who seroconverted 24 .…”