AIDS Res Hum Retroviruses. 2023 Jul 18. doi: 10.1089/AID.2023.0026. Online ahead of print.
HTLV-1 prevalence in Portugal is low and mainly affects immigrants from endemic areas where HIV infection represents a public health problem. Despite the majority of HTLV-1 infected individuals remains asymptomatic, severe pathologies may develop after prolonged viral persistence, namely, an aggressive form of leukemia. An increase mortality rate and faster progression to death is often related to HTLV-1/HIV coinfection. Nevertheless, studies showed that some antiretrovirals used in HIV treatment lead to a positive immune response against HTLV-1. This study aimed to analyse epidemiological and clinical data, and to assess the diversity of HTLV-1 strains circulating in infected-residents diagnosed in the Portuguese national reference laboratory between 2010 and 2021. LTR and env proviral sequences derived from 20 individuals were used to generate phylogenetic trees along with multiples reference sequences from different geographic origin retrieved from the database. Three samples belong to Portuguese natives and 17 belong to immigrants: 15 from several countries of Africa, one from South America and one from Europe; six patients (30%, mean age 40.3 years) showed HTLV-1 related diseases and six (30%, mean age 45.2 years) were coinfected with HIV/AIDS. The results show that the Cosmopolitan subtype is circulating in Portugal, with ten sequences being classified as subgroup A, that include Portuguese and natives from S. Tomé and Príncipe with a mean age of 39.4 years, and ten sequences that segregated into the Senegal cluster derived from natives born in Guinea-Bissau with a mean age of 43.5 years. A high proportion of HTLV-1 related diseases and HIV/AIDS coinfection was observed. Risk behaviour practices and the absence of specific control measures, including diagnostic and treatment, may contribute to a silent dissemination of a broad diversity of HTLV-1 strains and, therefore, the increased rate of progression to debilitating diseases. In this manner, an early diagnostic and a molecular surveillance of HTLV-1 transmission remains necessary in Portugal.