Human T-lymphotropic virus type 1 (HTLV-1) deregulates the immune system and cell cycle, resulting in loss of immune tolerance and disease, including HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Three prime repair exonuclease 1 (TREX1) maintains innate immune tolerance of the host and host-cell permissiveness to retroviral infections. TREX1 polymorphisms may influence the course of infection and autoimmune manifestations. The influence of TREX1 531C/T polymorphism was investigated in HTLV-1 infection and development of symptoms among 151 persons infected with HTLV-1 (32 HAM/TSP, 19 rheumatologic manifestations, two dermatitis, five more than one diagnosis, two probable HAM/TSP, and 91 asymptomatic individuals) and 100 uninfected persons in the control group. Polymorphism genotyping and proviral load quantification were performed by real-time polymerase chain reaction (PCR) and antinuclear antibodies (ANAs) were screened by an indirect immunofluorescence assay. No statistically significant difference was found in polymorphism genotype and allele frequencies between the infected and control groups. HAM/TSP patients showed higher frequency of TT genotype than asymptomatic persons (p = 0.0339). Proviral load was significantly higher among individuals with CT/TT genotypes and CC genotype carriers had lower proviral load and higher levels of proinflammatory cytokines. ANAs were present only in the HAM/TSP group. TREX1 531C>T polymorphism seems to be associated with TREX-1 regulation and HTLV-1 infection.

This descriptive, observational, cross-sectional study evaluated HTLV-1 and HTLV-2 infections in Ananindeua, northern Brazil. Individuals were screened for anti-HTLV-1/2 using ELISA (Murex HTLV-I + II, DiaSorin). Reactive or indeterminate samples underwent confirmation via Western blot (HTLV Blot 2.4 kit, MP Diagnostics) and/or RT-qPCR. A questionnaire examined behavioral and risk factors for HTLV-1/2 infection. HTLV-positive individuals received counseling, nurse follow-up, and specialized medical care. Among the 228 individuals investigated, 6 (2.7%) were infected with HTLV-1: 4 men (66.67%) and 2 women (33.33%), aged 51–73 years. The only significant risk factor observed was blood transfusion. Additionally, 80 other individuals residing in the municipality of Ananindeua independently visited the laboratory for an HTLV-1/2 diagnosis. Among them, 23 were diagnosed with HTLV-1 infection, and 1 with HTLV-2. Among the 30 positive individuals, 80% were asymptomatic, while 20% exhibited clinical manifestations associated with HTLV infection, including HAM and Sézary syndrome. These results indicate a notable prevalence of HTLV-1 infection in the municipality of Ananindeua emphasizing the significance of diagnosing the infection to assess its prevalence across the country accurately.

Genetic variations in components of the immune response seem to be an important factor that contributes to the manifestation of symptoms of some diseases related to HTLV-1 infection. Nerve growth factor (NGF) and the p75 neurotrophin receptor (p75^NTR) are related to the maintenance of neurons and the activation of the immune response. In this study, we evaluated the association of the NGF -198C/T, NGF Ala35Val, and p75^NTR Ser205Leu polymorphisms with HTLV-1 infection and plasma cytokine levels in 166 samples from individuals infected with HTLV-1 (59 symptomatic and 107 asymptomatic). The genotyping and quantification of the proviral load were performed by real-time PCR, and cytokine levels were measured by ELISA. The NGF -198C/T and NGF Ala35Val polymorphisms were not associated with HTLV-1 infection. The frequency of the Ser/Leu genotype of p75^NTR Ser205Leu was more frequent in the control group (p = 0.0385), and the Ser/Leu genotype and allele Leu were more frequent among the asymptomatic (p < 0.05), especially with respect to the HTLV-1-associated myelopathy (HAM) group (p < 0.05). The symptomatic showed a higher proviral load and higher TNF-α and IL-10 levels (p < 0.05). Asymptomatic carriers of the Ser/Leu genotype (p = 0.0797) had lower levels of proviral load and higher levels of TNF-α (p = 0.0507). Based on the results obtained, we conclude that the p75^NTR Ser205Leu polymorphism may be associated with reduced susceptibility to HTLV-1 infection, a lower risk of developing symptoms, including HAM, and better infection control.