Molecular Epidemiology and Phylogenetic Analysis of HTLV-1 in HIV-1-infected Patients in Tehran, Iran

Human T-lymphotropic virus 1 (HTLV-1) and Human Immunodeficiency Virus 1 (HIV-1) can be transmitted through similar routes, so co-infection may occur, especially in endemic regions. Since there is limited data on this co-infection, its genotypes, and genetic variations in Iran, we aimed to investigate HTLV-1/HIV-1 co-infection to gain a better understanding of its epidemiology. Whole blood and plasma of 282 HIV-1-infected patients were sampled in Tehran, Iran. Briefly, plasma samples were used to investigate HTLV I/II antibody seroprevalence by ELISA, and PBMCs were used for molecular analysis of Tax, LTR, and ENV regions. Then, amplified LTR and ENV were subjected to sequencing, phylogenetic analysis, and variation determination. Out of 282 HIV-1-infected individuals (31.9% female and 68.1% male, with a mean age of 43.80 ± 11.25), 6 samples (2.1%) were seropositive, and provirus was detected in 2 samples (0.7%). Both samples belonged to HTLV-1aTC, and after genetic variation analysis for both LTR and ENV regions, the ENV region displayed 6 and 7 point mutations in each isolate, respectively, relative to the ATK HTLV-1 prototype, with 5 and 4 of these mutations being nonsynonymous. Analysis of the LTR region identified 8 mutations in each isolate, comprising 7 point mutations and one deletion. This survey confirms the prevalence of HTLV-1 among people living with HIV-1, highlighting the need for ongoing monitoring of this population. Additionally, the findings in this study indicate that HTLV-1aTC is predominant among the studied population, consistent with previous reports worldwide, and nucleotide variations are present in both investigated HTLV-1 regions.