HTLV in Sweden.

Sweden is a country with a low prevalence of human lymphotropic T-cell virus (HTLV) infection, estimated at < 0.005%, but the infection rate is notably higher in specific risk groups such as HTLV-2 among intravenous drug users (IVDU) and people originating from HTLV-1 highly endemic areas. Thus, in the most recent study from 2012, the prevalence of HTLV-2 among IVDU in Stockholm was 3.2%. However, much of the epidemiological data on HTLV in Sweden stems from studies conducted primarily between the 1990s and 2007, and the impact of migration to Sweden during the past 15 years has not been evaluated. Despite Sweden's status as a country with generally low prevalence of HTLV, it is prudent to anticipate and prepare for several potential challenges associated with HTLV infection in the future. Proactive measures to enhance awareness, alongside strategies to curtail transmission and mitigate complications, are crucial for addressing this relatively rare, but significant health issue. In this work, we review the current epidemiological knowledge about HTLV in Sweden and discuss future Swedish perspectives.

Geographic characteristics of HTLV-1 molecular subgroups and genetic substitutions in East Asia: Insights from complete genome sequencing of HTLV-1 strains isolated in Taiwan and Japan.

BACKGROUND: Although Japan is a major endemic area for human T-lymphotropic virus type 1 (HTLV-1) and the virus has been well-studied in this region, there is limited research on HTLV-1 in surrounding regions. In this study, we determined the complete genome sequences of HTLV-1 strains isolated from Taiwan and Japan and investigated the geographic characteristics of molecular subgroups and substitution mutations to understand the spread of HTLV-1 and its correlation with human migration. METHODOLOGY/PRINCIPAL FINDINGS: The complete genome sequences of 26 HTLV-1 isolates from Taiwan were determined using next-generation sequencing and were compared with those of 211 isolates from Japan in terms of subgroup and genetic mutations. In total, 15/26 (58%) isolates from Taiwan belonged to the transcontinental subgroup and 11/26 (42%) isolates belonged to the Japanese subgroup. The transcontinental subgroup was significantly more prevalent among Taiwanese isolates than Japanese isolates (58% vs 18%, P < 0.0001). The mutation rate for the complete HTLV-1 sequence was as low as 0.2%. On examining individual base substitutions, the G-to-A mutation was predominant. Bayesian phylogenetic tree analysis estimated the time to the most recent common ancestor for the transcontinental and Japanese subgroups to be 28447 years. The transcontinental subgroups from Taiwan and Japan appeared to form clusters according to their respective regions. CONCLUSIONS/SIGNIFICANCE: The transcontinental subgroup of HTLV-1 is predominant in Taiwan, while the Japanese subgroup is common in Japan. The difference in subgroup distribution may be attributed to the initial spread of the transcontinental subgroup in East Asia, followed by the influx of the Japanese subgroup.

Screening for HTLV-1 infection should be expanded in Europe.

Human T-cell lymphotropic virus type 1 (HTLV-1) infection is spreading globally at an uncertain speed. Sexual, mother-to-child, and parenteral exposure are the major transmission routes. Neither vaccines nor antivirals have been developed to confront HTLV-1, despite infecting over 10 million people globally and causing life-threatening illnesses in 10% of carriers. It is time to place this long-neglected disease firmly into the 2030 elimination agenda. Current evidence supports once-in-life testing for HTLV-1, as recommended for HIV, hepatitis B and C, along with targeted screening of pregnant women, blood donors, and people who attended clinics for sexually transmitted infections (STIs). Similar targeted screening strategies are already being performed for Chagas disease in some Western countries in persons from Latin America. Given the high risk of rapid-onset HTLV-1-associated myelopathy, universal screening of solid organ donors is warranted. To minimize organ wastage, however, the specificity of HTLV screening tests must be improved. HTLV screening of organ donors in Europe has become mandatory in Spain and the United Kingdom. The advent of HTLV point-of-care kits would facilitate testing. Finally, increasing awareness of HTLV-1 will help those living with HTLV-1 to be tested, clinically monitored, and informed about transmission-preventive measures.

How do socioeconomic determinants of health affect the likelihood of living with HTLV-1 globally? A systematic review with meta-analysis.

Introduction: Human T Lymphotropic Virus type 1 (HTLV-1) is a neglected retrovirus associated with many clinical disorders, most notably Adult T-cell Leukemia/Lymphoma and HTLV-1-Associated Myelopathy (HAM). Found in endemic clusters across the world, high prevalence has been reported in minoritized groups who suffer from health inequities. This study investigates the association between HTLV-1 prevalence and the following socioeconomic determinants of health: education, income, and employment, which are markers of health inequity. Methods: A systematic review was conducted by searching the following databases: Ovid/Medline, Embase, Global Health Database, Web of Science, LILACS and SciELO. Primary studies in English, Spanish and Portuguese mentioning HTLV-1 and one of education, income and/or employment were included. A random-effects meta-analysis was performed, and odds ratios (OR) were calculated to determine the association between these socioeconomic determinants of health and HTLV-1 prevalence. Results: 42 studies were included. The likelihood of having HTLV-1 was higher in individuals with less than completed primary education compared to those who completed primary education (OR 1.86 [95% CI 1.34-2.57]; p < 0.01). This may be because individuals with low education have reduced access to and understanding of health information, thus increasing the prevalence of risk factors associated with HTLV-1 infection. No other determinants were found to be statistically significant. Conclusion: Fewer years of schooling are associated with increased likelihood of contracting HTLV-1. Therefore, health promotion materials and public health policies regarding HTLV-1 must consider those with lower educational levels to effectively reduce disease transmission. Systematic review registration: https://www.crd.york.ac.uk/prospero/display_record.php?RecordID=335004, identifier (CRD42022335004).

Performance evaluation of Espline HTLV-I/II, a newly developed rapid immunochromatographic antibody test for different diagnostic situations.

IMPORTANCE: The World Health Organization estimated that 5-10 million people are infected with human T-cell leukemia virus type 1 (HTLV-1). This number is likely to be underestimated because reliable endemic data are available for only approximately 1.5 billion people worldwide. The point-of-care test is a powerful tool for the easy and quick detection of infections without the requirement for expensive instruments and laboratory equipment. Espline HTLV-I/II, a newly developed rapid immunochromatographic antibody test that was evaluated in this study, might significantly advance our understanding of the global epidemiology of HTLV-1 infection.

HTLV-1-associated myelopathy in Spain.

BACKGROUND: HTLV-1 infection is a neglected disease. Over 10 million people are infected worldwide, with hot spots of high endemicity across all continents. Roughly 5% of HTLV-1 carriers develop HTLV-1-associated myelopathy (HAM), a progressive subacute neurological disabling disease. METHODS: We report the main features of patients diagnosed with HAM up to date in Spain, a non-endemic country with a relatively high migrant flow from Latin America and Equatorial Africa, where HTLV-1 is endemic. RESULTS: A total of 451 cases of HTLV-1 had been recorded in Spain until the end of year 2022. HAM had been diagnosed in 58 (12.9%). The current incidence is of 2-3 new cases per year. Women represent 76%. Mean age at diagnosis is 49 years-old. Nearly 60% are Latin Americans. Although sexual transmission is the most likely route of HTLV-1 acquisition, up to 6 individuals had been infected following solid organ transplantation. Rapid onset myelopathy developed in all but one of these transplant recipients from three HTLV-1-positive donors. HTLV-1 subtype 1a transcontinental was the only variant recognized in HAM patients. HTLV-1 proviral load was significantly greater in HAM patients than in asymptomatic HTLV-1 carriers (677 vs 104 HTLV-1 DNA copies/104 PBMC; p = 0.012). Symptom relief medications and physiotherapy have been the only treatment providing some benefit to HAM patients. Neither significant clinical nor virological efficacy was noticed using antiretrovirals in at least 9 HAM patients. Two thirds of HAM patients ended up in a wheelchair and with urinary/fecal sphincter incontinence. CONCLUSION: HAM is the most frequent clinical manifestation of HTLV-1 infection in Spain, a non-endemic country. Middle aged women migrants from Latin America are the most frequently affected. Two thirds end up in a wheelchair despite using antiretroviral therapy.

Advances in the treatment of human T-cell lymphotropic virus type-I associated myelopathy.

INTRODUCTION: Nearly 2-3% of those 10 to 20 million individuals infected with the Human T-cell lymphotropic virus type-1 (HTLV-1); are predisposed to developing HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). It is a neuro-inflammatory disease; differentiated from multiple sclerosis based on the presence of typical neurologic symptoms, confirmation of HTLV-1 infection, and other molecular biomarkers. AREAS COVERED: A brief review of the epidemiology, host immune responses, and molecular pathogenesis of HAM/TSP is followed by detailed discussions about the host-related risk factors for developing HAM/TSP and success/failure stories of the attempted management strategies. EXPERT OPINION: Currently, there is no effective treatment for HAM/TSP. Anti-retroviral therapy, peculiar cytokines (IFN-α), some anti-oxidants, and allograft bone marrow transplantation have been used for treating these patients with limited success. Under current conditions, asymptomatic carriers should be examined periodically by a neurologist for early signs of spinal cord injury. Then it is crucial to determine the progress rate to adapt the best management plan for each patient. Corticosteroid therapy is most beneficial in those with acute myelitis. However, slow-progressing patients are best managed using a combination of symptomatic and physical therapy. Additionally, preventive measures should be taken to decrease further spread of HTLV-1 infection.

Human T-lymphotropic virus 1/2 infection among immigrants and refugees in Central Brazil, an emerging vulnerable population.

Introduction: Migratory flows play a significant role in the spread of human T-lymphotropic virus 1/2 (HTLV-1/2). In the last decade, a substantial migration of individuals occurred from Haiti and Venezuela to Brazil. However, data on the prevalence of HTLV-1/2 infection among these international migrants in Brazil are scarce. This study describes the prevalence of this infection among immigrants and refugees in Central Brazil. Methods: A cross-sectional study was conducted with 537 international migrants in the State of Goiás, Central Brazil. Participants were interviewed, and blood samples were collected. Serological screening for anti-HTLV-1/2 was performed using an enzyme-linked immunosorbent assay (ELISA; Murex HTLV-I + II, DiaSorin, Dartford, UK), and seropositive samples were submitted for confirmation by a line immunoassay (INNO-LIA HTLV I/II, Fujirebio, Europe N.V., Belgium). Results: The majority of participants were males (54.4%), between 18 and 50 years old (78%; mean age: 29.1 years), self-declared black (55.1%), reported 1 to 12 years of formal education (70.9%), and were either Venezuelans (47.9%) or Haitians (39.7%). Additionally, 50.1% were immigrants, 49% were refugees, and five were Brazilian children (0.9%) born to Haitian immigrant parents. The overall prevalence of anti-HTLV-1/2 was 0.95% (95% CI: 0.31-2.28), with HTLV-1 at 0.19% and HTLV-2 at 0.76%. All seropositive individuals (n = 5) were refugees from Venezuela, resulting in a rate of 2.26% for anti-HTLV-1/2, HTLV-1 (0.45%) and HTLV-2 (1.81%) among Venezuelan refugees. Of the demographic and behavioral characteristics evaluated, unprotected sexual intercourse and having more than one sexual partner (≥2) in the previous 12 months were associated with HTLV-1/2 seropositivity among Venezuelans. Conclusion: This study revealed, despite the low seroprevalence of HTLV-1/2 among international migrants in Central Brazil, evidence of HTLV-1 and HTLV-2 infections in Venezuelan refugees. In addition, their characteristics highlight that specific social and health programs should be implemented for these emergent and socially vulnerable migrant groups.

Seroprevalence of Human T-Cell Lymphotropic Virus-1 in a Jamaican Antenatal Population and Assessment of Pooled Testing as a Cost Reduction Strategy for Implementation of Routine Antenatal Screening.

Mother to child transmission (MTCT) of human T-cell lymphotropic virus (HTLV)-1 is associated with increased risk of adult T-cell leukemia and can be unrecognized without routine antenatal screening. We assessed the seroprevalence of HTLV-1/2 among pregnant women attending The University Hospital of the West Indies Antenatal Clinic, 2019, and validated a cost-effective strategy to screen antenatal clinic attendees for HTLV-1/2. Residual antenatal samples from 370 women were tested for HTLV-1/2 by chemiluminescence microparticle immunoassay (CMIA). Six samples were confirmed HTLV-1 positive by Western blot (none for HTLV-2) for a prevalence of 1.62%. Four mother-child pairs were able to be recruited for HTLV testing of children, with two children testing HTLV-1/2 positive. Medical records of HTLV-1-infected women revealed that all women breastfed, indicating an unrecognized risk for HTLV MTCT. To assess whether pooling of samples as a cost-reduction strategy could be introduced, we pooled all antenatal samples received between November and December 2021 into 12 pools of eight samples/pool. Two pools were CMIA positive, and de-pooling of samples identified two CMIA-positive samples (one per pool), both confirmed as HTLV-1 by Western blot. These results indicate that HTLV-1 remains prevalent in pregnant Jamaican women and that sample pooling can be a cost-effective strategy to limit MTCT in Jamaica.

Epidemiological and molecular evidence of intrafamilial transmission through sexual and vertical routes in Bahia, the state with the highest prevalence of HTLV-1 in Brazil.

INTRODUCTION: Familial clustering of HTLV-1 and related diseases has been reported in Brazil. However, intrafamilial transmission of HTLV-1 based on molecular analysis has been studied only in a few communities of Japanese immigrants and African-Brazilians. OBJECTIVE: To investigate the familial clustering of HTLV-1 infection and to determine the likely routes of transmission through epidemiological and genetic analyzes. METHODS: Medical records of 1,759 HTLV-1+ patients from de the Center for HTLV in Salvador, Brazil, were evaluated to identify first-degree relatives previously tested for HTLV-1. Familial clustering was assumed if more than one member of the same family was HTLV-1+. LTR regions of HTLV-1 sequences were analyzed for the presence of intrafamilial polymorphisms. Family pedigrees were constructed and analyzed to infer the likely transmission routes of HTLV-1. RESULTS: In 154 patients at least one other family member had tested positive for HTLV-1 (a total of 182 first-degree relatives). Of the 91 couples (182 individuals), 51.6% were breastfed, and 67.4% reported never using a condom. Of the 42 mother-child pairs, 23.8% had a child aged 13 years or younger; all mothers reported breastfeeding their babies. Pedigrees of families with 4 or more members suggests that vertical transmission is a likely mode of transmission in three families. Three families may have had both vertical and sexual transmission routes for HTLV-1. The genetic signatures of the LTR region of 8 families revealed 3 families with evidence of vertical transmission, another 3 families (spouses) with sexual transmission, and one family with both transmission routes. HTLV-1 sequences belonged to Cosmopolitan subtype HTLV-1a Transcontinental subgroup A. CONCLUSION: Sexual and vertical transmission routes contribute to the intrafamilial spread of HTLV-1 in the state of Bahia.

The slowdown of new infections by human retroviruses has reached a plateau in Spain.

The 2022 annual meeting of the HTLV & HIV-2 Spanish Network was held in Madrid on December 14. We summarize here the main information presented and discussed at the workshop and review time trends for human retroviral infections in Spain. As transmissible agents, infections by human retroviruses are of obligatory declaration. Until the end of 2022, the Spanish national registry had recorded 451 cases of HTLV-1, 821 of HTLV-2, and 416 of HIV-2. For HIV-1, estimates are of 150 000 people currently living with HIV-1 and 60 000 cumulative deaths due to AIDS. During year 2022, new diagnoses in Spain were of 22 for HTLV-1, 6 for HTLV-2, and 7 for HIV-2. The last updated figures for HIV-1 are from 2021 and counted 2786 new diagnoses. The slowdown in yearly infections for HIV-1 in Spain points out that new strategies are needed to achieve the United Nations 95-95-95 targets by 2025. For the remaining neglected human retroviral infections, their control might be pushed throughout four interventions: (1) expanding testing; (2) improving education and interventions aimed to reduce risk behaviors; (3) facilitating access to antiretrovirals as treatment and prevention, including further development of long-acting formulations; and (4) increasing vaccine research efforts. Spain is a 47 million population country in South Europe with strong migration flows from HTLV-1 endemic regions in Latin America and Sub-Saharan Africa. At this time universal HTLV screening has been implemented only in the transplantation setting, following the report of 5 cases of HTLV-associated myelopathy shortly after transplantation of organs from HTLV-1 positive donors. There are four target populations for expanding testing and unveiling asymptomatic carriers responsible for silent HTLV-1 transmissions: (1) migrants; (2) individuals with sexually transmitted infections; (3) pregnant women; and (4) blood donors.

Trend in seroprevalence of HTLV-1/2 in Taiwanese blood donors-A 10-year follow-up.

OBJECTIVES: This study evaluated the Human T-lymphotropic virus (HTLV) screening policy impact on the HTLV seroprevalence from 2009 to 2018 as well as the differences between administrative districts in terms of prevalence distribution in Taiwan. BACKGROUND: Since February 1996, the Taiwan Blood Services Foundation (TBSF) had conducted HTLV screening of blood donors. The HTLV seroprevalence was 0.032% in 1999. MATERIALS AND METHODS: This cross-sectional study included donors' data collected from blood donation centres across Taiwan from 2009 to 2018. Enzyme immunoassay and Western blot assay were used for screening and confirmation of HTLV infections. In this study, the researchers calculated the trends in the HTLV rates of first-time and repeat donors across time as well as the HTLV prevalence distribution across the 22 administrative districts of Taiwan. RESULTS: Amongst 17 977 429 employed blood donations, 739 HTLV-seropositive donations (4.11 per 100 000 donations) were identified. The HTLV-positive donors were aged between 17 and 64 years, with a median age of 49 years. The overall seropositivity rates of first-time and repeat donors were 34.36/100 000 and 1.27/100 000. HTLV seroprevalence in first-time blood donors significantly decreased by 57% (crude odds ratio [95% confidence interval] (crude OR [95% CI]) = 0.43 [0.28-0.64]) within 10 years. A slight decline was also identified in repeat donors (crude OR [95% CI] = 0.73 [0.4-1.32]). Donors from different districts showed significantly varied prevalence. Most districts with high prevalence are situated in eastern Taiwan, for both donation types. Older blood donors were more likely to be infected with HTLV than younger ones in first time and repeat donors. Middle age donors (50-65 years) had an 18.47-39.65 greater risk than those aged <20 years. Significant higher risk of female was observed in both donation types. Amongst different age groups, first-time female donors increase 1.31-1.88 times infection risk and female in repeat donor group had 1.55-3.43 times greater risk. CONCLUSION: Over years of implementation of the HTLV blood donor screening policy by the TBSF, the HTLV seroprevalence of first-time donors has decreased consistently. Moreover, the HTLV seroprevalence of repeat donors has dropped considerably. This implies that the screening policy provides continued benefit. Females and older blood donors were more likely infected with HTLV than males and younger blood donors. The influence of age on infection was greater amongst first-time donors than amongst repeat donors. Therefore, appropriate measures should be taken to ensure public safety.

Signs and symptoms of human T-lymphotropic virus 1 and 2 infections in paediatric patients.

OBJECTIVE: To determine the prevalence of signs and symptoms of HTLV-1 and 2 infection in paediatric patients. METHODS: We included cohort, case-control and descriptive observational studies that reported the prevalence of signs and symptoms of HTLV-1 and 2 infections in paediatric patients. Searches were performed in MEDLINE® (Ovid), EMBASE and LILACS from inception to the present, and we saturated information with other sources of published and unpublished literature. We decided not to perform meta-analysis according to heterogeneity. RESULTS: A total of eight studies met the inclusion criteria for qualitative analysis. No studies of HTLV-2 were found. Females predominated and there was vertical transmission in nearly 100% of cases. Infective dermatitis was a common manifestation of HTLV in paediatric patients. In addition, persistent hyperreflexia, clonus and the Babinski sign were early neurological alterations observed in patients carrying the virus. CONCLUSION: HTLV screening is recommended in patients presenting infective dermatitis, persistent hyperreflexia, walking disturbances and in those who come from endemic zones.

Analysis of Programmed Cell Death-1 (PD-1) Gene Variations (re11568821 and rs41386349) in HTLV-1 Infection Using One Primer Pair and Proviral Load.

About 90% of people infected with Human T lymphotropic virus type-1 (HTLV-1) virus are asymptomatic, so it can be said that the prevalence of this virus is not completely clear. During chronic infection, the expression of programmed cell death-1 (PD-1) protein increases and causes exhausted phenotype in T cells. Considering the role of host genetics and immune responses in HTLV-1 infection, in this case-control study, included 81 asymptomatic carriers (ACs) and 162 healthy controls (HCs), rs11568821 and rs41386349 polymorphisms of PD-1 gene were evaluated by Polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP) method which investigated by one primer pair for both polymorphisms also, proviral load (PVL) measured by quantitative real-time PCR (Q-RT-PCR). The results showed that the mutant allele of rs11568821 (A) and rs41386349 (T) polymorphisms is associated with an increase in HTLV-1 infection significantly (p = 0.019 and p = 0.000 respectively). But there was no significant relationship between PVL and polymorphisms.

Viral co-infections in leprosy: a scoping review.

CONTEXT: The most reported viral co-infections in leprosy are human immunodeficiency virus (HIV), human T-cell lymphotropic virus (HTLV), hepatitis B virus (HBV), hepatitis C virus (HCV), and SARS-CoV-2. In co-infections, the burden of an agent can be increased or decreased by the presence of others. To address this issue, we need to fully understand their prevalence, risk factors, immunology, clinical manifestations, and treatment. The purpose of this scoping review is to describe the clinical and epidemiological characteristics of the most reported viral co-infections in leprosy to inform clinicians and guide future research. METHODS: The authors conducted a literature search of five databases for articles on each of the aforementioned co-infections published prior to October 2022. Two independent reviewers conducted the selection process and identified 53 papers meeting the study inclusion criteria. The data extraction process and evidence synthesis were conducted by one reviewer and double-checked by a second one, consistent with best practice recommendations for scoping reviews. RESULTS: For all assessed viruses, most studies reported prevalence rates in leprosy patients higher than the general population. Studies found that HTLV, HBV, and HCV chronic infections were highest in multibacillary leprosy, whereas HIV was mostly found in paucibacillary leprosy, and SARS-Cov-2 affected leprosy subtypes equally. Overall, co-infections were also associated with higher rates of leprosy reactions, except for COVID-19. Forty-six percent of the studies discussed issues related to treatment, which led to favorable outcomes for the most part. CONCLUSIONS: This review summarizes the existing literature on viral co-infections in leprosy patients, generating valuable insights and recommending areas for future research.

Low risk of human T-lymphotropic virus infection in U.S. blood donors; Is it time to consider a one-time selective testing approach?

BACKGROUND: U.S. blood donors are tested at each donation for human T-lymphotropic virus (HTLV) antibodies. Depending on donor incidence and other mitigation/removal technologies, a strategy of one-time selective donor testing should be considered. METHODS: Antibody seroprevalence was calculated for HTLV-confirmed-positive American Red Cross allogeneic blood donors from 2008 to 2021. Incidence was estimated for seven 2-year time periods using confirmed-positive repeat donors having seroconverted in 730 days. Leukoreduction failure rates were obtained from internal data from July 1, 2008-June 30, 2021. Residual risks were calculated using a 51-day window period. RESULTS: Between 2008 and 2021, >75 million donations (>18 million donors) yielded 1550 HTLV seropositives. HTLV seroprevalence was 2.05 antibody-positives per 100,000 donations (0.77 HTLV-1, 1.03 HTLV-2, 0.24 HTLV-1/2), and 10.32 per 100,000 among >13.9 million first-time donors. Seroprevalence differed significantly by virus type, sex, age, race/ethnicity, donor status, and U.S. census region. Over 14 years and 24.8 million person-years of observation, 57 incident donors were identified (25 HTLV-1, 23 HTLV-2, and 9 HTLV-1/2). Incidence decreased from 0.30 (13 cases) in 2008-2009 to 0.25 (7 cases) in 2020-2021. Female donors accounted for most incident cases (47 vs. 10 males). In the last 2-year reporting period, the residual risk was 1 per 2.8 million donations and 1 per 3.3 billion donations when coupled with successful leukoreduction (0.085% failure rate). CONCLUSIONS: HTLV donation seroprevalence for the years 2008-2021 varied by virus type and donor characteristics. Low HTLV residual risk and use of leukoreduction processes support the conclusion that a selective one-time donor testing strategy should be considered.

Development and validation of a duplex real-time PCR for the rapid detection and quantitation of HTLV-1.

BACKGROUND: The HTLV-1 prevalence in China varies geographically, while HTLV-2 infection has rarely been found so far. Proviral load is one of the determining factors of pathogenesis and progression of HTLV-1 related diseases. However, neither molecular assays nor commercial kits are available for HTLV-1 diagnosis in China. The objective of the present study was to develop and validate a TaqMan qPCR assay for HTLV-1 proviral load quantification. RESULTS: A plasmid containing both the HTLV-1 of interest and a fragment of the RNase P (RPPH1) gene was constructed and used to establish the standard curves. The assay has a wide dynamic range (2.5 × 108 copies/reaction ~ 25 copies/reaction) and sensitive to 1 copy for HTLV-1 and RPPH1. The limit of detection for Hut102 cell concentration was 0.0218% (95% confidence interval 0.0179-0.0298%). The assay gave coefficient of variation (CV) for both the HTLV-1 and RPPH1 Ct values. All of the HTLV-1 sero-negative samples and MOT cell line (infected with HTLV-2) amplified only the RPPH1 gene by our method, presenting 100% specificity. 85 Samples confirmed positive or indeterminate by LIA were performed by established qPCR assay and WB. 90.0% (27/30) of LIA-HTLV-1-positive, 33% (2/6) of LIA-untypeable and 2% (1/49) of LIA-indeterminate samples were defined as qPCR-positive. The median PVL of LIA-positive samples (n = 27, 1.780 copies/100 cells) was much higher than that of LIA-untypeable and (n = 2, 0.271 copies/100 cells) indeterminate samples (n = 1, 0.017 copies/ 100 cells). Additionally, compared to WB, the duplex qPCR verified more positive samples, demonstrating a better sensitivity. CONCLUSION: The duplex qPCR developed here with high sensitivity, good specificity and reproducibility could accurately and quantitatively detect the HTLV-1 PVLs, which can be used to confirm the initial reactive samples for an improved cost/benefit ratio as well as to monitor the clinical progression and efficacy of therapy in patients with HTLV-1 related disease.

Epidemiological Evidence of Nosocomial and Zoonotic Transmission of Human T-Cell Leukemia Virus-1 in a Large Survey in a Rural Population of Central Africa.

BACKGROUND: Central Africa is one of the largest areas of high endemicity for human T-cell leukemia virus-1 (HTLV-1). However, no preventive measures are yet implemented to reduce its transmission, which can be sexual, from mother-to-child, or through contaminated blood products. Rare zoonotic transmissions from nonhuman primates (NHPs) have also been reported in this region. Here we investigated the HTLV-1 prevalence and associated risk factors in a rural population in Cameroon. METHODS: From 2019 to 2021, we performed a cross-sectional survey in the eastern region of Cameroon. HTLV-1 infection was first screened by ELISA, then tested by western blot and envelope gene targeted polymerase chain reaction. Risk factors associated with HTLV-1 infection were identified by logistic regression in univariable and multivariable analyses. RESULTS: Among 3400 participants, HTLV-1 prevalence was 1.1% (95% confidence interval [CI], .7-1.5). Factors independently associated with HTLV-1 infection were Pygmy ethnicity (adjusted odd ratio [aOR], 2.9; 95% CI, 1.3-6.2), history of surgery (aOR, 6.3; 95% CI, 2.2-17.8), and NHP bite (aOR, 6.6; 95% CI, 2.2-19.8). CONCLUSIONS: These results suggest both iatrogenic and zoonotic transmission of HTLV-1 in Cameroon. Further studies are needed to assess the risk of nosocomial transmission of HTLV-1, to guide public health authorities in implementing preventive measures to control HTLV-1 transmission.