Geographical clustering of human T-cell lymphotropic virus type I in Guadeloupe, an endemic Caribbean area

Clinical and Public Health Implications of Human T-Lymphotropic Virus Type 1 Infection

Human T-lymphotropic virus type 1 (HTLV-1) is estimated to affect 5 to 10 million people globally and can cause severe and potentially fatal disease, including adult T-cell leukemia/lymphoma (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The burden of HTLV-1 infection appears to be geographically concentrated, with high prevalence in discrete regions and populations. While most high-income countries have introduced HTLV-1 screening of blood donations, few other public health measures have been implemented to prevent infection or its consequences. Recent advocacy from concerned researchers, clinicians, and community members has emphasized the potential for improved prevention and management of HTLV-1 infection. Despite all that has been learned in the 4 decades following the discovery of HTLV-1, gaps in knowledge across clinical and public health aspects persist, impeding optimal control and prevention, as well as the development of policies and guidelines. Awareness of HTLV-1 among health care providers, communities, and affected individuals remains limited, even in countries of endemicity. This review provides a comprehensive overview on HTLV-1 epidemiology and on clinical and public health and highlights key areas for further research and collaboration to advance the health of people with and at risk of HTLV-1 infection.

Silent dissemination of HTLV-1 in an endemic area of Argentina. Epidemiological and molecular evidence of intrafamilial transmission

Background

Molecular and epidemiological studies of transmission routes and risk factors for infection by HTLV-1 are extremely important in order to implement control measures, especially because of the high prevalence of HTLV-1 in several regions of the world. San Salvador de Jujuy, Northwest Argentina, is a highly endemic area for HTLV-1 and foci of tropical spastic paraparesis/HTLV-1-associated myelopathy.

Objective

To gain further insight into the role of intrafamilial transmission of HTLV-1 in a highly endemic region in Argentina.

Method

Cross-sectional study in Northwest Argentina. Epidemiological data and blood samples were collected from 28 HTLV-1 infected subjects (index cases) and 92 close relatives/cohabitants. HTLV-1 infection was diagnosed by detection of antibodies and proviral DNA. The LTR region was sequenced and analyzed for genetic distances (VESPA software), in addition to determination and identification of polymorphisms to define HTLV-1 family signatures.

Results

Fifty seven of the 120 subjects enrolled had antibodies against HTLV-1 and were typified as HTLV-1 by PCR. The prevalence rate of HTLV-1 infection in family members of infected index cases was 31.52% (29/92). The infection was significantly associated with gender, age and prolonged lactation. Identity of LTR sequences and presence of polymorphisms revealed high prevalence of mother-to-child and interspousal transmission of HTLV-1 among these families.

Conclusion

There is an ongoing and silent transmission of HTLV-1 through vertical and sexual routes within family clusters in Northwest Argentina. This evidence highlights that HTLV-1 infection should be considered as a matter of public health in Argentina, in order to introduce preventive measures as prenatal screening and breastfeeding control.

Epidemiological Aspects and World Distribution of HTLV-1 Infection

The human T-cell leukemia virus type 1 (HTLV-1), identified as the first human oncogenic retrovirus 30 years ago, is not an ubiquitous virus. HTLV-1 is present throughout the world, with clusters of high endemicity located often nearby areas where the virus is nearly absent. The main HTLV-1 highly endemic regions are the Southwestern part of Japan, sub-Saharan Africa and South America, the Caribbean area, and foci in Middle East and Australo-Melanesia. The origin of this puzzling geographical or rather ethnic repartition is probably linked to a founder effect in some groups with the persistence of a high viral transmission rate. Despite different socio-economic and cultural environments, the HTLV-1 prevalence increases gradually with age, especially among women in all highly endemic areas. The three modes of HTLV-1 transmission are mother to child, sexual transmission, and transmission with contaminated blood products. Twenty years ago, de Thé and Bomford estimated the total number of HTLV-1 carriers to be 10-20 millions people. At that time, large regions had not been investigated, few population-based studies were available and the assays used for HTLV-1 serology were not enough specific. Despite the fact that there is still a lot of data lacking in large areas of the world and that most of the HTLV-1 studies concern only blood donors, pregnant women, or different selected patients or high-risk groups, we shall try based on the most recent data, to revisit the world distribution and the estimates of the number of HTLV-1 infected persons. Our best estimates range from 5-10 millions HTLV-1 infected individuals. However, these results were based on only approximately 1.5 billion of individuals originating from known HTLV-1 endemic areas with reliable available epidemiological data. Correct estimates in other highly populated regions, such as China, India, the Maghreb, and East Africa, is currently not possible, thus, the current number of HTLV-1 carriers is very probably much higher.

The epidemiology of human retrovirus-associated illnesses

Human T-cell leukemia/lymphoma virus type 1 (HTLV-1) was the first oncogenic human retrovirus discovered in 1980. It is estimated that around 10-20 million people are infected with HTLV-1 worldwide. However, HTLV-1 is not a ubiquitous virus. Indeed, HTLV-1 is present throughout the world with clusters of high endemicity including mainly southern Japan, the Caribbean region, parts of South America and intertropical Africa, with foci in the Middle East and Australia. The origin of this puzzling geographical repartition is probably linked to a founder effect in certain human groups. In the high endemic areas, 0.5 to 50% of the people have antibodies against HTLV-1 antigens. HTLV-1 seroprevalence increases with age, especially in women. HTLV-1 has 3 modes of transmission: mother to child, mainly through prolonged breastfeeding (> 6 months); sexual, mainly but not exclusively occurring from male to female; and by blood products contaminated by infected lymphocytes. HTLV-1 is mainly the etiological agent of two very severe diseases: a malignant T CD4+ cell lymphoproliferation of very poor prognosis, named adult T-cell leukemia/lymphoma (ATLL), and a chronic neuro-myelopathy named tropical spastic paraparesis/HTLV-1-associated myelopathy (TSP/HAM). HTLV-1 is also associated with rare anterior uveitis, infective dermatitis and myositis in some high HTLV-1 endemic areas. The repartition of the different molecular subtypes or genotypes is mainly linked to the geographical origin of the infected persons but not to the associated pathology. HTLV-1 possesses a remarkable genetic stability probably linked to viral amplification via clonal expansion of infected cells rather than by reverse transcription. This stability can be used as a molecular tool to gain better insights into the origin, evolution and modes of dissemination of HTLV-1 and infected populations. HTLV-1 originated in humans through interspecies transmission from STLV-1, a very closely related retrovirus, highly endemic in several populations of apes and Old World monkeys.

Identification of clonally rearranged T-cell receptor beta chain genes in HTLV-I carriers as a potential instrument for early detection of neoplasia

We analyzed the genetic recombination pattern of the T-cell receptor beta-chain gene (TCR-beta) in order to identify clonal expansion of T-lymphocytes in 17 human T-lymphotropic virus type I (HTLV-I)-positive healthy carriers, 7 of them with abnormal features in the peripheral blood lymphocytes. Monoclonal or oligoclonal expansion of T-cells was detected in 5 of 7 HTLV-I-positive patients with abnormal lymphocytes and unconfirmed diagnosis by using PCR amplification of segments of TCR-beta gene, in a set of reactions that target 102 different variable (V) segments, covering all members of the 24 V families available in the gene bank, including the more recently identified segments of the Vbeta-5 and Vbeta-8 family and the two diversity beta segments. Southern blots, the gold standard method to detect T-lymphocyte clonality, were negative for all of these 7 patients, what highlights the low sensitivity of this method that requires a large amount of very high quality DNA. To evaluate the performance of PCR in the detection of clonality we also analyzed 18 leukemia patients, all of whom tested positive. Clonal expansion was not detected in any of the negative controls or healthy carriers without abnormal lymphocytes. In conclusion, PCR amplification of segments of rearranged TCR-beta is reliable and highly suitable for the detection of small populations of clonal T-cells in asymptomatic HTLV-I carriers who present abnormal peripheral blood lymphocytes providing an additional instrument for following up these patients with potentially higher risk of leukemia.

[Viral seroprevalence, transfusion and alloimmunization in adults with sickle cell anemia in Guadeloupe]

We retrospectively studied the prevalence of anti HIV 1 and 2, anti-HTLV-I, anti-Hepatitis B and C viruses (HBV and HCV) antibodies, anti-HBV vaccinal coverage, transfused patients and alloimmunizations frequencies among adult sickle cell patients attending the sickle cell center (SCC) of Guadeloupe. The data were collected from the medical files of the centre. Among the studied samples (n = 331) no transfusional HIV contamination was observed. All patients with HTLV-I (n = 11, 3.3% of whole sample) and anti-HCV (n = 9, 2.7%) positive serology had transfusion history. Five patients (1.5%) had an active hepatitis B. Vaccination against HBV efficiently protected 247 patients (74.4%) and 57 had post-hepatitis B antibodies. We observed that 213 patients (64%) had a history of transfusion (88% of SS patients and 36% of the SC patients, p < 0.05). Fifty-four patients (16%) presented alloimmunization, 4 of them have never been transfused. These results show that it is still necessary to optimise transfusion protocol and their safety, and to diagnose viral contamination in transfused sickle cell patients.

A case-control study of risk factors associated with human T-cell lymphotrophic virus type-I seropositivity in blood donors from Guadeloupe, French West Indies

BACKGROUND AND OBJECTIVES

An age- and gender-specific distribution characterizes human T-cell lymphotrophic virus type-I (HTLV-I) seropositivity in Guadeloupe (French West Indies). Further epidemiological studies are required to identify other possible risk factors associated with this retroviral infection.

MATERIALS AND METHODS

A nested case-control study was conducted between 1997 and 1999 among blood donors. A total of 102 HTLV-I-positive subjects were matched (at a ratio of 1 : 3) by gender, age (+/-5 years) and donor status (new or regular) to 306 HTLV-I-negative controls. Information was obtained through a questionnaire assessing both environmental and behavioural variables.

RESULTS

Factors independently associated with HTLV-I infection included a low level of education [odds ratio (OR) 6.61, confidence interval (CI) 2.89-15.15], black ethnicity (OR 3.28, CI 1.01-10.65), two or more sex partners in the previous 3 years (OR 2.43, CI 1.16-5.10), early age at first sexual intercourse (0.84 risk reduction per additional year, CI 0.76-0.93), a history of sexually transmitted diseases (OR 2.29, CI 1.0-5.34) and positive Chlamydia serology (OR 1.95, CI 1.03-3.68).

CONCLUSION

These data provide a wide spectrum of features associated with HTLV-I seropositivity, especially sexual risk factors. It strongly suggests that heterosexual intercourse is an important route of HTLV-I transmission in Guadeloupe, even among low-risk populations such as blood donors.

Serological, epidemiological, and molecular differences between human T-cell lymphotropic virus Type 1 (HTLV-1)-seropositive healthy carriers and persons with HTLV-I Gag indeterminate Western blot patterns from the Caribbean

To investigate the significance of serological human T-cell lymphotropic virus type 1 (HLTV-1) Gag indeterminate Western blot (WB) patterns in the Caribbean, a 6-year (1993 to 1998) cross-sectional study was conducted with 37,724 blood donors from Guadeloupe (French West Indies), whose sera were routinely screened by enzyme immunoassay (EIA) for the presence of HTLV-1 and -2 antibodies. By using stringent WB criteria, 77 donors (0.20%) were confirmed HTLV-1 seropositive, whereas 150 (0.40%; P < 0.001) were considered HTLV seroindeterminate. Among them, 41.3% (62) exhibited a typical HTLV-1 Gag indeterminate profile (HGIP). Furthermore 76 (50.7%) out of the 150 HTLV-seroindeterminate subjects were sequentially retested, with a mean duration of follow-up of 18.3 months (range, 1 to 70 months). Of these, 55 (72.4%) were still EIA positive and maintained the same WB profile whereas the others became EIA negative. This follow-up survey included 33 persons with an HGIP. Twenty-three of them (69.7%) had profiles that did not evolve over time. Moreover, no case of HTLV-1 seroconversion could be documented over time by studying such sequential samples. HTLV-1 seroprevalence was characterized by an age-dependent curve, a uniform excess in females, a significant relation with hepatitis B core (HBc) antibodies, and a microcluster distribution along the Atlantic coast of Guadeloupe. In contrast, the persons with an HGIP were significantly younger, had a 1:1 sex ratio, did not present any association with HBc antibodies, and were not clustered along the Atlantic façade. These divergent epidemiological features, together with discordant serological screening test results for subjects with HGIP and with the lack of HTLV-1 proviral sequences detected by PCR in their peripheral blood mononuclear cell DNA, strongly suggest that an HGIP does not reflect true HTLV-1 infection. In regard to these data, healthy blood donors with HGIP should be reassured that they are unlikely to be infected with HTLV-1 or HTLV-2.