High prevalence of human T-cell leukemia virus type-1b genotype among blood donors in Gabon, Central Africa.

BACKGROUND: The African continent is considered to be the largest endemic area of HTLV-1 infection, with at least several million infected individuals. Systematic screening of blood donors can prevent the transmission of HTLV-1 in blood. Gabon is one of the countries with the highest prevalence of HTLV-1 worldwide, and yet the routine testing of blood donors has still not been introduced. METHODS: All blood donations collected between April and July 2017 at the Centre National de Transfusion Sanguine of Gabon were studied. Plasma samples were screened by ELISA for the presence of HTLV-1/2 antibodies. Western blot (WB) and polymerase chain reaction (PCR) tests were used for confirmation. RESULTS: In total, 3123 blood donors were tested, including 1740 repeat and 1378 first-time blood donors (FTBDs). Of them, 132 samples tested positive for HTLV-1/2 by ELISA (4.2%). WB and PCR confirmed HTLV-1 infection for 23 individuals. The overall prevalence of HTLV-1 was 0.74% [95% CI 0.47%-1.10%], 1% in FTBD, and 0.5% in repeat donors. Age and sex-adjusted prevalence was five-fold lower in FTBD than in the general adult population of rural areas of Gabon. All detected HTLV-1 strains belonged to the central African HTLV-1b genotype but were highly diverse. CONCLUSION: We report an overall prevalence of HTLV-1 of 0.74%, one of the highest values reported for blood donors in Africa. Given the high risk of HTLV-1 transmission in blood, it is necessary to conduct cost-effectiveness studies to determine the need and feasibility of implementing screening of HTLV-1 in blood donors in Gabon.

Human T-Lymphotropic virus type 1 and human immunodeficiency virus co-infection in rural Gabon.

INTRODUCTION: Human T-cell lymphotrophic virus type-1 (HTLV-1) and human immunodeficiency virus (HIV-1) co-infection occur in many populations. People living with HIV-1 and infected with HTLV-1 seem more likely to progress rapidly towards AIDS. Both HTLV-1 and HIV-1 are endemic in Gabon (Central Africa). We investigated HTLV-1 and HIV-1 co-infection in the Haut-Ogooué province, and assessed factors that may favor the rapid evolution and progression to AIDS in co-infected patients. METHODS: Plasma samples from HTLV-1 patients were tested using ELISA, and positive samples were then tested by western blot assay (WB). We used the polymerase chain reaction to detect HTLV-1 Tax/Rex genes using DNA extracted from the buffy coat of ELISA-positives samples. RESULTS: We recruited 299 individuals (mean age 46 years) including 90 (30%) men and 209 (70%) women, all of whom are under treatment at the Ambulatory Treatment Centre of the province. Of these, 45 were ELISA HTLV-1/2 seropositive. According to WB criteria, 21 of 45 were confirmed positive: 20 were HTLV-1 (44%), 1 was HTLV-1/2 (2%), 2 were indeterminate (4%) and 22 were seronegative (49%). PCR results showed that 23 individuals were positive for the Tax/Rex region. Considering both serological and molecular assays, the prevalence of HTLV-1 infection was estimated at 7.7%. Being a woman and increasing age were found to be independent risk factors for co-infection. Mean CD4+ cell counts were higher in HTLV-1/HIV-1 co-infected (578.1 (± 340.8) cells/mm3) than in HIV-1 mono-infected (481.0 (± 299.0) cells/mm3) Individuals. Similarly, the mean HIV-1 viral load was Log 3.0 (± 1.6) copies/ml in mono-infected and Log 2.3 (± 0.7) copies/ml in coinfected individuals. CONCLUSION: We described an overall high prevalence of HTLV-1/HIV-1 co-infection in Gabon. Our findings stress the need of strategies to prevent and manage these co-infections.

Risk factors for HTLV-1 infection in Central Africa: A rural population-based survey in Gabon.

BACKGROUND: Human T-Lymphotropic Virus type 1 (HTLV-1) is a human oncoretrovirus that infects at least 5 to 10 million people worldwide and is associated with severe diseases. Africa appears as the largest HTLV-1 endemic area. However, the risk factors for the acquisition of HTLV-1 remain poorly understood in Central Africa. METHODS: We conducted an epidemiological survey between 2013 and 2017, in rural areas of 6 provinces of Gabon, in a rainforest environment. Epidemiological data were obtained and blood samples were collected after informed consent. Plasma were screened for HTLV-1 antibodies by ELISA and the positive samples were then tested by Western blot (WB). Genomic DNA derived from buffy-coat was subjected to two semi-nested PCRs amplifying either HTLV-1 env gene or LTR region fragments. RESULTS: We recruited 2,060 individuals over 15 years old, including 1,205 men and 855 women (mean age: 49 years). Of these, 299 were found to be ELISA HTLV-1/2 seropositive. According to WB criteria, 136 were HTLV-1 (6.6%), 25 HTLV-1/2 (1.2%) and 9 HTLV seroreactive (0.4%). PCR results showed that 146 individuals were positive for at least one PCR: 104 for the env gene and 131 for the LTR region. Based on both serological and molecular results, 179 individuals were considered infected with HTLV-1, leading to an overall prevalence of 8.7%. The distribution of HTLV-1 infection was heterogeneous across the country. Based on multivariable analyses, female gender, increasing age, ethnicity (Pygmy) and multiple hospitalizations (more than 5 times) were found to be independent risk factors for HTLV-1 infection. Furthermore, a non-human primate bite appeared to be marginally associated with a higher risk of HTLV-1 infection. CONCLUSION: Based on state-of-the-art serological and molecular methods, we have demonstrated that rural adult populations in Gabon are highly endemic for HTLV-1. Our results regarding risk factors should lead to public health actions aiming to reduce HTLV-1 transmission.