Tax gene characterization of human T-lymphotropic virus type 1 strains from Brazilian HIV-coinfected patients

Abstract

The tax gene of human T-lymphotropic virus type 1 (HTLV-1) diverges among isolates according to geographic regions and has been classified into two genotypes: taxA and taxB. In Brazil, taxA is the most prevalent genotype in symptomatic and asymptomatic carriers. Few studies have been conducted in HIV-infected patients. The present study characterized the tax gene (1059 bp) in 13 Brazilian HIV-1/HTLV-1-coinfected patients from the south and southeast regions. The results confirmed the transcontinental HTLV-1 subgroup A of the Cosmopolitan subtype and showed high nucleotide similarity both among Brazilian sequences and in relation to the ATK prototype (99.5% and 99.2%, respectively). Six nucleotide substitutions were highly conserved among isolates, ranging from 76.9% to 100%: C7401T, T7914C, C7920T, C7982T, G8231A, and A8367C. The presence of the Brazilian molecular signature of genotype taxA was confirmed in all of the isolates, and they clustered into two Latin American clusters, which confirms the double introduction of HTLV-1 in Brazil.

FIG. 1.

Phylogenetic tree constructed by the neighbor-joining method using the PAUP v4b10 software for the partial tax region of 977 bp (position 7378–8354 relative to the ATK prototype) of human T-lymphotropic virus type 1 (HTLV-1) of 49 isolates, including sequences from the south and southeast regions of Brazil (GenBank AN JN887698–JN887710) in bold, generated with the TrN+G model. Bootstrap values above 65% and zero length using the likelihood ratio test with p<0.001 (**) and p≤0.05 (*) in key branches are depicted. The HTLV-1 EL isolate was used as the outgroup.