A survey of the human T-cell lymphotropic virus type I (HTLV-I) in south-western Colombia

Lymphotropic Viruses EBV, KSHV and HTLV in Latin America: Epidemiology and Associated Malignancies. A Literature-Based Study by the RIAL-CYTED

The Epstein-Barr virus (EBV), Kaposi sarcoma herpesvirus (KSHV) and human T-lymphotropic virus (HTLV-1) are lymphomagenic viruses with region-specific induced morbidity. The RIAL-CYTED aims to increase the knowledge of lymphoma in Latin America (LA), and, as such, we systematically analyzed the literature to better understand our risk for virus-induced lymphoma. We observed that high endemicity regions for certain lymphomas, e.g., Mexico and Peru, have a high incidence of EBV-positive lymphomas of T/NK cell origin. Peru also carries the highest frequency of EBV-positive classical Hodgkin lymphoma (HL) and EBV-positive diffuse large B cell lymphoma, not otherwise specified (NOS), than any other LA country. Adult T cell lymphoma is endemic to the North of Brazil and Chile. While only few cases of KSHV-positive lymphomas were found, in spite of the close correlation of Kaposi sarcoma and the prevalence of pathogenic types of KSHV. Both EBV-associated HL and Burkitt lymphoma mainly affect young children, unlike in developed countries, in which adolescents and young adults are the most affected, correlating with an early EBV seroconversion for LA population despite of lack of infectious mononucleosis symptoms. High endemicity of KSHV and HTLV infection was observed among Amerindian populations, with differences between Amazonian and Andean populations.

The challenge of describing the epidemiology of HTLV in the Amazon region of Brazil

HTLV-1 was the first described human retrovirus and was soon found to be associated with severe clinical diseases, including a devastating lymphoma/leukemia and other inflammatory diseases. Although HTLV-2 is not usually pathogenic, it is widely distributed among native Indian populations in Brazil, particularly in the Amazon region of the country. Presently, HTLV spreads mainly by the sexual route and from mother to child, and virus persistence is an active biological factor aiding its transmission. Recently, the use of illicit drugs has been shown to be an additional risk factor, showing the influence of new habits on the epidemiology of HTLV in the region. Despite the detection of the virus in several different populations in the Amazon region of Brazil for almost 30 years, the exact prevalence of HTLV-1/2 is not well defined. The original biases in sampling and the selection of epidemiologically unsuitable populations were commonly repeated in most prevalence studies, generating unreliable and conflicting figures that do not represent the actual prevalence of HTLV. The improvements in clinical and laboratory facilities have resulted in the description of several clinical manifestations that were previously unknown in the region. The extent of the spread of the virus must be defined in this region, which is the largest geographical area of the country. As prophylaxis advances toward the use of vaccines against HTLV-1, it is important to determine who is at risk of being infected and developing a disease to successfully implement preventive measures, particularly as proposals are made to eradicate the virus among humans.

Epidemiology and Etiopathology of Human T-Lymphotropic Viruses: Diagnostic and Clinical Implications for Non-Endemic Areas

Human T-lymphotropic viruses (HTLV) type I and II were first described more than a decade ago. HTLV-I epidemiology and etiopathology are more defined than those of HTLV-II, but conflicting results have been obtained in seroepidemiologic surveys, mainly for difficulties in the discrimination between the two infections. The introduction of advanced serologic and molecular assays has recently provided sensitive and specific tools for diagnosis, and the epidemiologic and etiopathologic patterns linked to these retroviruses are being more precisely defined. Moreover, extensive nucleotide sequence analyses performed so far have mainly focused on HTLV-I isolates. The recent discovery of new HTLV-II endemic areas and the isolation of HTLV-II strains from intravenous drug users have finally provided the material for the molecular characterization of HTLV-II isolates, which is now a rapidly envolving field. We review the diagnostic strategies available and the etiologic associations reported so far for both viruses and also discuss the occurrence and significance of indeterminate serologic reactivities observed in both endemic and non-endemic areas.

Human T-lymphotropic virus type 1 prevalence in northeastern Iran, Sabzevar: an epidemiologic-based study and phylogenetic analysis

Human T-lymphotropic virus type 1 (HTLV-I) is an important global health problem in the world mainly in the endemic areas of HTLV-I infection. It was previously reported that Mashhad, in northeastern Iran, is a new endemic region of HTLV-I. The aim of this study was to examine the prevalence and phylogenetic analysis of HTLV-I in Sabzevar, located in the southeast of Mashhad. In this cross-sectional study 1445 individuals were selected by multistage cluster sampling. Serum samples were screened for anti-HTLV-I antibody using enzyme-linked immunosorbent assay (ELISA); all of the ELISA-positive samples were confirmed by polymerase chain reaction (PCR). Long terminal repeat (LTR) sequencing was carried out to determine the type of HTLV-I in Sabzevar. In the primary screening by ELISA, 26/1445 (1.8%) of those sampled were reactive for HTLV-I antibody. Twenty-four out of 26 samples were confirmed HTLV-I infection by PCR (24/1445). The overall prevalence of HTLV-I infection in Sabzevar is 1.66%. The prevalence of the virus infection in men and women was 2.42% (11/455) and 1.31% (13/989), respectively. Seroprevalence was associated with age, increasing significantly among those older than 30 years (p=0.015), and a history of surgery (p=0.002), imprisonment (p=0.018), and hospitalization (p=0.005). Three out of 24 positive HTLV-I samples were selected for sequencing and phylogenetic analysis of LTR. The results showed that HTLV-I in Sabzevar belonged to the cosmopolitan subtype. The present study showed Sabzevar is a new endemic area for HTLV-I infection. Our study emphasizes that systemic HTLV-I screening of blood donors in Sabzevar and other cities in Khorasan province is important and should be taken into account.

The impact of interferon-alpha treatment on clinical and immunovirological aspects of HTLV-1-associated myelopathy in northeast of Iran

Human T-lymphotropic virus type 1 (HTLV-1)-associated myelopathy/tropical spastic paraparesis (HAM/TSP) is a chronic inflammatory myelopathy. The pathophysiology of HAM/TSP is not yet fully understood; therefore, effective therapy remains a challenging issue. This study was designed to evaluate the efficacy of interferon-alpha (IFN-α) in HAM/TSP patients in the Northeast of Iran. Forty-nine patients with a definite diagnosis of HAM/TSP were enrolled in this clinical trial. For six months, the patients received three million international units of subcutaneous IFN-α-2b per each injection. The dose regimen was daily injection for the first month, three times administration per week for the months 2 and 3, twice weekly injection for the months 4 and 5 and weekly injection for the sixth month. The clinical and laboratory responses were evaluated based on neurologic examinations and immunovirological markers. IFN-α had significant but temporary effect on the motor and urinary functions of the patients. Comparing to the baseline values, proviral load was significantly decreased one month after treatment in responders (495.20±306.87 to 262.69±219.24 p=0.02) and non-responders (624.86±261.90 to 428.28±259.88 p=0.03). Anti-HTLV-1 antibody titers were significantly decreased among responders (1152.1±200.5 to 511.6±98.2 p=0.009) and non-responders (1280.1±368.1 to 537.6±187 p=0.007). Flow cytometry showed no significant changes in CD4, CD8, CD4CD25 and CD16CD56 counts with IFN-α. The positive impact of IFN-α was observed during the treatment period with significant effects on some clinical aspects of HAM/TSP.

High prevalence of HTLV-I infection in Mashhad, Northeast Iran: a population-based seroepidemiology survey

BACKGROUND

Mashhad, in the northeast of Iran has been suggested as an endemic area for human T cell lymphotropic virus type I (HTLV-I) infection since 1996.

OBJECTIVES

We performed a community-based seroepidemiology study to examine the prevalence and risk factors for HTLV-I infection in the city of Mashhad.

STUDY DESIGN

Between May and September 2009, overall 1678 subjects from all the 12 geographical area of Mashhad were selected randomly by multistage cluster sampling for HTLV antibody. The study population included 763 males and 915 females, with the mean age of 29.1 ± 18.5 years. 1654 serum samples were assessed for HTLV antibody using ELISA and reactive samples were confirmed by Western blot and PCR.

RESULTS

The overall prevalence of HTLV-I infection in whole population was 2.12% (95% CI, 1.48-2.93) with no significant difference between males and females (p = 0.093) and the prevalence of HTLV-II seropositivity was 0.12% (95% CI, 0.02-0.44). The HTLV-I Infection was associated with age (p<0.001), marital status (p<0.001), education (p = 0.047), and history of blood transfusion (p = 0.009), surgery (p<0.001), traditional cupping (p = 0.002), and hospitalization (p = 0.004). In logistic regression analysis, age was the only variable that had a significant relation with the infection (p = 0.006, OR = 4.33).

CONCLUSIONS

Our results demonstrated that Mashhad still remains an endemic area for HTLV-I infection despite routine blood screening. Thus, further strategies are needed for prevention of the virus transmission in whole population.

Epidemiology, treatment, and prevention of human T-cell leukemia virus type 1-associated diseases

Human T-cell leukemia virus type 1 (HTLV-1), the first human retrovirus to be discovered, is present in diverse regions of the world, where its infection is usually neglected in health care settings and by public health authorities. Since it is usually asymptomatic in the beginning of the infection and disease typically manifests later in life, silent transmission occurs, which is associated with sexual relations, breastfeeding, and blood transfusions. There are no prospects of vaccines, and screening of blood banks and in prenatal care settings is not universal. Therefore, its transmission is active in many areas such as parts of Africa, South and Central America, the Caribbean region, Asia, and Melanesia. It causes serious diseases in humans, including adult T-cell leukemia/lymphoma (ATL) and an incapacitating neurological disease (HTLV-associated myelopathy/tropical spastic paraparesis [HAM/TSP]) besides other afflictions such as uveitis, rheumatic syndromes, and predisposition to helminthic and bacterial infections, among others. These diseases are not curable as yet, and current treatments as well as new perspectives are discussed in the present review.

Role of resident CNS cell populations in HTLV-1-associated neuroinflammatory disease

Human T cell leukemia virus type 1 (HTLV-1), the first human retrovirus discovered, is the etiologic agent for a number of disorders; the two most common pathologies include adult T cell leukemia (ATL) and a progressive demyelinating neuroinflammatory disease, HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). The neurologic dysfunction associated with HAM/TSP is a result of viral intrusion into the central nervous system (CNS) and the generation of a hyperstimulated host response within the peripheral and central nervous system that includes expanded populations of CD4+ and CD8+ T cells and proinflammatory cytokines/chemokines in the cerebrospinal fluid (CSF). This robust, yet detrimental immune response likely contributes to the death of myelin producing oligodendrocytes and degeneration of neuronal axons. The mechanisms of neurological degeneration in HAM/TSP have yet to be fully delineated in vivo and may involve the immunogenic properties of the HTLV-1 transactivator protein Tax. This comprehensive review characterizes the available knowledge to date concerning the effects of HTLV-1 on CNS resident cell populations with emphasis on both viral and host factors contributing to the genesis of HAM/TSP.

Heterogeneous geographic distribution of human T-cell lymphotropic viruses I and II (HTLV-I/II): serological screening prevalence rates in blood donors from large urban areas in Brazil

Brazil may have the highest absolute number of HTLV-I/II seropositive individuals in the world. Screening potential blood donors for HTLV-I/II is mandatory in Brazil. The public blood center network accounts for about 80.0% of all blood collected. We conducted a cross-sectional study to assess the geographic distribution of HTLV-I/II serological screening prevalence rates in blood donors from 27 large urban areas in the various States of Brazil, from 1995 to 2000. Enzyme immunoassay (EIA) was used to test for HTLV-I/II. The mean prevalence rates ranged from 0.4/1,000 in Florianopolis, capital of Santa Catarina State, in the South, to 10.0/1,000 in São Luiz, Maranhão State, in the Northeast. EIA prevalence rates are lower in the South and higher in the North and Northeast. The reasons for such heterogeneity may be multiple and need further studies.

Prevalência da infecção pelo vírus linfotrópico humano de células T e fatores de risco associados à soropositividade em doadores de sangue da cidade de Rio Branco, AC, Brasil (1998-2001)

Para cada doador de sangue soropositivo (ELISA, Abbott®) para HTLV-I/II, de dezembro de 1998 a março de 2001, também foram selecionados dois soronegativos. As amostras séricas foram re-testadas pelo ELISA (Murex®) e aquelas que permaneceram soropositivas foram testadas pelo Western Blot e pela PCR. Das 11.121 amostras séricas, 73 (0,66%) foram positivas (Abbott®), mas somente 12 (0,11%) permaneceram positivas (Murex®), enquanto que as 146 soronegativas foram confirmadas, apesar de ser sofrível o índice de concordância entre os dois ELISA. O Western Blot confirmou as 12 amostras como soropositivas: 8 (0,07%) HTLV-I; duas (0,02%) HTLV-II e duas (0,02%) indeterminadas - sendo pela PCR uma pelo HTLV-I e a outra pelo HTLV-II. Em conclusão, nessa população da Amazônia Ocidental foi muito baixa a soroprevalência de HTLV-I/II, apesar de ser esperada maior prevalência do HTLV-II devido a grande miscigenação racial indígena.

Seroprevalence and risk factors for human T-cell lymphotropic virus (HTLV-I) infection among ethnically and geographically diverse Peruvian women

OBJECTIVE

To assess the seroprevalence and risk factors for HTLV-I infection in Peruvian women.

METHODS

Five hundred and sixty-eight healthy women >20 years of age from three Peruvian regions were randomly selected and screened for HTLV-I. ELISA-reactive sera were confirmed via immunofluorescence assay, recombinant immunoblot assay, Western blot, and PCR. Women from Huanta (n=303), an Andean city inhabited by indigenous Quechuans, El Carmen (n=132), a primarily African-American coastal town, and Lima (n=133), with its Mestizo population, were selected.

RESULTS

HTLV-I antibodies were present in 2.5% (14/568) of women (1.3% in Huanta, 3.8% in El Carmen, and 3.8% in Lima); 2.5%, 2.7% and 2.6% of Quechuans, Mestizas and African-Americans, respectively, were infected. History of a blood transfusion (P <0.00002), chronic scabies (P <0.02), having a relative with leukemia (P <0.04), age +/- 38 years (P <0.03), young age at first intercourse (P <0.04), lifetime partners >4 (P <0.04), educational status (P <0.02) and >4 pregnancies (P <0.03) were significantly associated with infection.

CONCLUSIONS

HTLV-I is endemic among asymptomatic Peruvian women. Parenteral, vertical and heterosexual transmission are associated with infection.

Spatial distribution of the Human T-Lymphotropic Virus types I and II (HTLV-I/II) infection among blood donors of Hemominas Foundation, Belo Horizonte, Minas Gerais State, Brazil, 1994-1996

We conducted a cross-sectional study of the spatial distribution of HTLV-I/II infection among blood donors of Hemominas Foundation, living in Belo Horizonte, from 1994 to 1996. Study population (1,022) was composed by 533 cases (positive Western Blot (WB), indeterminate WB and ELISA positive without WB result) and a random sample of 489 non-cases (HTLV-I/II serum negative). Cases and non-cases were georeferenced using the exact or an approximation of the household address reported at the blood donation interview. Using multivariate analysis, cases with WB result are less likely to be reposition blood donors compared to voluntary ones (OR = 0.70; CI 95%: 0.50-0.99). Using the difference between univariate K functions, we found no evidence that cases and non-cases differ in their spatial distribution. We found no evidence that cases with and without WB result differ in the distance between their residence and Hemominas Foundation. No donors without WB result were georeferenced by the exact address. These donors could not have received the Hemominas letter inviting them to return to collect the second blood sample.

Os vírus linfotrópicos de células T humanos (HTLV) na última década (1990-2000): aspectos epidemiológicos

Vinte anos após o isolamento do vírus linfotrópico humano tipo I, muitos aspectos epidemiológicos, patogênicos e filogenéticos já estão esclarecidos. Sabe-se que em regiões endêmicas a prevalência aumenta com a idade e é maior no sexo feminino. Três patologias estão claramente relacionadas a ele: paraparesia espástica tropical / mielopatia associada ao HTLV, leucemia de células T do adulto e uveíte. Os modos de infecção, semelhantes aos dos outros retrovírus, são: transfusão de sangue, relações sexuais não protegidas, transplacentária e durante o aleitamento materno. A história natural das doenças relacionadas ao HTLV-I ainda não está bem estabelecida. O risco de portadores da infecção desenvolverem patologias depende de mais estudos de incidência para serem corretamente estimados. Menos se conhece sobre o HTLV-II. A despeito do alto grau de homologia entre os dois tipos, os vírus interagem de forma bem diversa com os infectados, não havendo uma associação clara de doença com o HTLV-II. Relatos recentes têm apontado sua participação em casos de mielopatia crônica semelhante à TSP/HAM. As implicações incertas do prognóstico para pessoas infectadas pelo vírus linfotrópico humano (HTLV-I/II) e suas formas de transmissão constituem um problema de saúde pública, principalmente em áreas consideradas endêmicas para esse vírus.

Inflammatory myopathy on HTLV-I infection: case report

We describe a 41 years old woman who 17 years ago presented hypotonia and proximal muscular weakness in the upper and lower limbs. On neurological examination, the biceps, triceps and Achilles reflexes were absent; the brachioradialis reflexes were decreased and the patellar reflexes were normal. There was bilateral Babinski sign. The remainder of the neurological examination was unremarkable. In the investigation a myopathic pattern was found in the electromyography. The nerve-conduction study was normal; a ELISA method for HTLV-I antibodies was positive in the blood and in the cerebral spinal fluid. The muscle biopsy showed inflammatory myopathy, compatible with polymyositis. This paper focuses the polymyositis in the beginning of an HTLV-I infection case.

Community-based molecular epidemiology of HTLV type I in Taiwan and Kinmen: implication of the origin of the cosmopolitan subtype in northeast Asia

To understand the possible origin and dissemination of HTLV-I infection in northeast Asia, community-based molecular epidemiological studies were conducted on the Kinmen Islands (off the coast of Fukien Province, China) and in Taiwan. A total of 3831 Taiwanese from 3 townships (Pu-Li, Chu-Dung, and Pu-Tze) and 993 aborigines from 4 tribes in Taiwan participated in this study. The prevalence rates of HTLV-I infection in adult residents from Pu-Li, Chu-Dung, and Pu-Tze were 0.82, 1.72, and 1.63%, respectively. None of the aborigines had HTLV-I infection. Previously, 0.73% of the adult population of Kin-Hu, Kinmen were found to have HTLV-I infection. Peripheral blood mononuclear cells were collected from HTLV-I carriers identified both in Taiwan and Kinmen and the HTLV-I LTR sequences were PCR amplified, subcloned, and sequenced for phylogenetic tree analysis. The results showed that all 6 HTLV-I isolates from Kinmen and 13 of 18 (72.2%) isolates from Taiwan were group a (transcontinental) of Cosmopolitan subtype, while 5 of 18 (27.8%) isolates from Taiwan were group b (Japanese) of Cosmopolitan subtype. Since all of the HTLV-I-infected persons were descendants of immigrants from mainland China, the origin of the Cosmopolitan subtype in Taiwan and Kinmen may not have been Japan, as previously theorized, but China, possibly the result of the migration of an infected population in the past several centuries.

Risk factors for human T-cell lymphotropic virus types I and II (HTLV-I and -II) in blood donors: the Retrovirus Epidemiology Donor Study. NHLBI Retrovirus Epidemiology Donor Study

In the United States, blood donors have been routinely screened for human T-cell lymphotropic virus (HTLV) since 1988. HTLV-I and -II seropositive blood donors have been identified through confirmatory testing at five participating blood centers and frequency-matched seronegative controls provided information on potential HTLV sociodemographic, parenteral, and sexual risk factors during structured interviews. After adjustment, low educational attainment; accidental needlesticks or cuts; prior blood transfusion; > or = 7 sex partners; and a sex partner from an HTLV-I endemic area were significantly associated with both HTLV-I and -II. Gender did not modify the odds ratios (OR) in the final logistic regression models, despite apparent male-female differences in gender-specific bivariable analysis. Injection drug use (IDU) or having sex with an IDUs were significant risks for HTLV-II, but not for HTLV-I. The OR for donors who had IDU sex partners was 20.6 times higher than those who did not. For IDUs, the OR was increased 10.5 times over nonusers. Abortion was a significant HTLV-II risk factor for women. Our findings indicate that IDU and sex with IDUs are important risk factors for HTLV-II transmission, even among low-risk populations such as blood donors.

Six Colombian patients with adult T-cell leukemia/lymphoma

Six Colombian patients with adult T-cell leukemia/lymphoma (ATL) are presented. The clinical and hematological features, the familial clusters of human T lymphotropic virus type 1 (HTLV-I) carriers and the prognoses of the Colombian ATL patients were similar to those previously reported for Japanese ATL patients. The only difference was the mean age of onset, which was more than 20 years younger than in Japanese patients. Three patients with ATL were suffering from strongyloidiasis. In one patient it was suggested that ATL developed after horizontal transmission from his wife. In addition, there was a familial case of ATL and HAM/TSP. It seems that in some areas of Colombia, not only HTLV-I infection and HAM/TSP but also ATL are highly endemic.

T-cell lymphoma in Singapore: pathology, clinical findings and association with HTLV-1 antibodies

Of 128 cases of malignant lymphomas studied in Singapore between 1986 and 1988, 28 were identified as peripheral T-cell lymphomas. Sera from two of the 128 cases were positive for HTLV-1 antibodies and both cases had the clinical and pathological features of adult T-cell leukaemia/lymphoma. The pathological and clinical features of the 28 cases of peripheral T-cell lymphoma are presented in detail. Survival data indicated no significant difference between the low grade and high grade histological types. Three of the patients had previous or concomitant malignancies. The percentage of T-cell lymphomas associated with HTLV-1 infection in Singapore is low compared to those areas in which HTLV-1 is endemic.

Seroprevalence and cofactors of HTLV-I infection in Tumaco, Colombia

This study presents an analysis of the factors associated with HTLV-I seroprevalence in the endemic area of Tumaco, Colombia. During June to August 1988, 1,077 individuals were selected at random from a population of 45,594. The overall prevalence rate of HTLV-I antibodies was 2.8%. Among females prevalence was significantly higher (p less than 0.02) than among males. Rates increased substantially with age. HTLV-I prevalence among individuals with history of use of intravenous medications was significantly higher (p less than 0.001) than in those without such history. Logistic regression analysis included age in years, indicators for male gender, and for i.v. injections, and their interactions. Age was very strongly associated to HTLV-I infection among females. At early ages prevalence was not different between sexes, but females presented a significantly higher rate than males after age 42. History of i.v. administered medications was very strongly associated in the univariate analysis and, although significance was borderline in the multivariate analysis, it had the effect of doubling the odds of HTLV-I infection.

Prevalence of HTLV-I and HTLV-II infection in Gabon, Africa: comparison of the serological and PCR results

A cluster sampling survey was performed in 1989 in Libreville, Gabon, to determine HTLV-I and HTLV-II prevalence and to compare the efficacy of polymerase chain reaction (PCR) and serology in detecting HTLV-I and HTLV-II infections. A total of 322 sera from adults were tested by ELISA and by Western blot (WB). The WB patterns were interpreted according to WHO criteria and those of the manufacturer. PCR analysis using primer pairs in the gag and pol region, with a specific probe for HTLV-I and HTLV-II, was performed on the lymphocytes of the 322 adults. In addition, 134/322 samples were re-tested with tax primers, in a second laboratory. Using WHO criteria, 8/322 (2.5%) samples were positive on WB and 25 were indeterminate; with the criteria of the kit, 26/322 (8.1%) were positive and 7 were indeterminate by WB. By PCR, 13 (4%) samples were positive, including 12 for HTLV-I (3.7%) and one for HTLV-II (0.3%). All 8 seropositive samples (by the WHO criteria) were positive by PCR, as were 4 out of 25 indeterminate samples. Only one out of 289 seronegative samples was positive by PCR. In contrast, only 12/26 positive samples by the kit criteria were confirmed by PCR. These results confirm the relatively high HTLV-I/II seroprevalence observed in Gabon. HTLV-I infection is preponderant, but HTLV-II is also present. The WHO criteria for WB give a better fit with PCR results than the kit criteria for WB. In the absence of a specific confirmatory test and based on the uncommon "seronegative" HTLV-I/II infection, the indication for PCR appears limited to the positive WB samples (to differentiate HTLV-I and II infection) and to the indeterminate WB samples.

The epidemiology of HTLV-I infection

It has been 10 years since the discovery of the human T-cell lymphotropic virus type I (HTLV-I), the first human retrovirus. During the past decade, significant progress has been made in understanding the transmission of the virus and defining its geographic distribution. It has been shown conclusively that HTLV-I is a causal factor in the induction of both adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy. However, the pathogenesis of each of these conditions is not clear, and in the light of the evidence of immune dysfunction seen among carriers of the infection, it is likely that other associated diseases will be identified. The challenge in the next decade will be to develop and implement therapeutic interventions among carriers to prevent such diseases as well as to curtail transmission within endemic populations.

Antibody to HTLV-I in indigenous inhabitants of the Andes and Amazon regions in Colombia

To explore the HTLV-I-carrying groups among the indigenous inhabitants in South America, a sero-epidemiological study on HTLV-I focusing on hinterland villages isolated from others in the Andes and Amazon regions was conducted. Five (2.9%) out of 171 subjects showed positive for HTLV-I antibody in the gelatin particle agglutination (PA) test. Two out of 5 positives with high antibody titer (greater than or equal to x 1024) in the PA test also showed a positive immunofluorescence (IF) test and anti-HTLV-I-specific protein products, p19, p24, p28, gp46, and p53 in sera by the Western blotting (WB) test. One of three negatives in the IF test showed positive antibodies to p19 and p24 by the WB test. Finally, two were confirmed as HTLV-I carriers and one was suspected of being a carrier. All three are Paez Indians from the central Andes; 53- and 34-year-old women and a 35-year-old man. The results show that HTLV-I carriers exist among isolated indigenous people in South America.