High prevalence of human T-lymphotropic virus 2 (HTLV-2) infection in villages of the Xikrin tribe (Kayapo), Brazilian Amazon region

Abstract

Background Studies have shown that the human T-lymphotropic virus 2 (HTLV-2) is endemic in several indigenous populations of the Brazilian Amazon and molecular analyses have shown the exclusive presence of HTLV-2 subtype 2c among the indigenous groups of this geographical region. Methods The present study characterizes the prevalence of HTLV-2 infection in three new villages of the Xikrin tribe, in the Kayapo group, according to their distribution by sex and age. The study included 263 samples from individuals from the Kateté, Djujeko and Oodjã villages. Plasma samples were tested for the presence of anti-HTLV-1/2 antibodies using enzyme-linked immunosorbent assays (ELISA). Seropositive samples were confirmed using real-time PCR, nested PCR and sequencing. Results The serological and molecular results confirmed the sole presence of HTLV-2 in 77 (29%) samples, with a prevalence of 38% among women and 18% among men. In these communities, it was found that the prevalence of HTLV-2 infection increased with age. Nucleotide sequences (642 bp, 5’LTR) from eight samples were subjected to phylogenetic analysis by the neighbor-joining method to determine the viral subtype, which confirmed the presence of HTLV-2c. Conclusions The results of the present study establish the presence of HTLV-2 infection in three new villages of the Xikrin tribe and confirm the high endemicity of the infection in the Kayapo indigenous group of the Brazilian Amazon.

The challenge of describing the epidemiology of HTLV in the Amazon region of Brazil

“…The initial figures indicated that the prevalence rates measured by immunoenzymatic assays ranged from 3.6% to more than 30% for HTLV-1, mostly among Indians populations [84,85], that the rate was 0.91% among those undergoing blood donation screening [100]. A large distribution of HTLV-2 was shown among Indians communities not only in the State of Para but also in the Amazon area of Brazil, reaching confirmed prevalence rates of more than 40% [6,51,56,63] among some Indian communities and the detection of a new molecular subtype (HTLV-2c) that was soon also described in urban areas outside of the ARB [6,33,50,51,116]. Prevalence studies also provide interesting information, such as the description of HTLV-2b among blood donors in Belém, which stresses the need for ongoing molecular epidemiology investigations [116].…”

“…Human infections by HTLV in the Amazon region of Brazil have been recorded by several studies involving blood donors [82,[98][99][100][101][102], pregnant women [103][104][105][106], urban familial aggregates [42] and native Indians [6,56] (Fig. 1).…”

“…In urban areas, HTLV infection is more common among women [42,57,58]. Within epidemiologically closed communities such as Indian populations, the distribution of antibodies against HTLV shows that the prevalence increases with increasing age and is not different between males and females; this is evidence of an equal efficiency of transmission from men to women and from women to men [6,28,56] with the aid of vertical transmission acting by chance to infect both sexes equally. It is worth mentioning that it is not commonly observed in urban areas [42].…”

“…Sexual transmission is certainly the most important transmission route for HTLV-1 and HTLV-2 and serves as an efficient mechanism for the spread of HTLV-2c among native Indian groups [6,28,56]. In urban areas, HTLV infection is more common among women [42,57,58].…”

HTLV in South America: Origins of a silent ancient human infection

“…This information is useful for detecting the occurrence and frequency of the viruses in order to determine the pathways through which the virus moves and the possible routes for future spread. HTLV-1 and HTLV-2 are largely distributed around the world ( Gessain and Cassar 2012 ; Braço et al. 2019 ; Li et al.…”