Epidemiology of tropical spastic paraparesis in Columbia and associated HTLV-I infection

HTLV-1 uveitis in Colombia, an underrecognized complication of a hitherto neglected condition: a case series

Three Colombian patients with chronic HTLV-1 infection and severe intermediate and/or posterior uveitis are described. In one case, retinal ablation was necessary due to extensive peripheral degeneration, while the other two were successfully managed with local anti-inflammatory therapy. Gradual resolution of ocular findings was observed in all three patients on follow-up. Uveitis is a rarely recognized late complication of this infection, which represents a diagnostic and therapeutic challenge for clinicians in endemic countries. The real extension of HTLV-1 prevalence in Colombia and the frequency of its ophthalmologic complications remain to be determined.

HTLV-1 associated acute adult T-cell lymphoma/leukemia presenting as acute liver failure in Micronesian: A case report

RATIONALE

Malignant infiltration accounts for 0.5% of acute liver failure cases, with non-Hodgkin's lymphoma the predominant cause. Adult T-cell lymphoma/leukemia (ATLL) is a rarer source of acute hepatitis, with only 3 cases reported and all resulting in immediate deterioration with death. ATLL rises from human T-lymphocytic virus-1 (HTLV-1), commonly found in Japan (southern and northern islands), the Caribbean, Central and South America, intertropical Africa, Romania, and northern Iran. In Micronesia, HTLV-1 infection amongst native-born is absent or exceedingly rare.

PATIENT CONCERNS

A 77-year-old Marshallese man presented to the emergency department with a 1-week history of generalized weakness, fatigue, and nausea. The physical exam revealed a cervical papulonodular exanthem and scleral icterus.

DIAGNOSIS

Laboratory studies were remarkable for aspartate-aminotransferase of 230 IU/L (reference range [RR]: 0-40), alanine-aminotransferase of 227 IU/L (RR: 0-41), alkaline phosphatase of 133 IU/L (RR: 35-129), and total bilirubin of 4.7 mg/dL (RR: 0-1.2), supporting acute liver injury. Platelet count was 11.6x104/μL (RR: 15.1-42.4 × 104), hemoglobin was 13.8 g/dL (RR: 13.7-17.5), and white blood cell count was 7570/μL (RR: 3800-10,800) with 81.8% neutrophils (RR: 34.0-72.0) and 10.4% lymphocytes (RR: 12.0-44.0). The peripheral blood smear demonstrated abnormal lymphocytes with occasional flower cell morphology. HTLV-1/2 antibody tested positive. The skin and liver biopsies confirmed atypical T-cell infiltrate. The diagnosis of ATLL was established.

INTERVENTIONS

The patient elected for palliative chemotherapy with cyclophosphamide, vincristine, and prednisone (CVP). He began antiviral treatment with zidovudine 250 mg bis in die (BID) indefinitely. Ursodiol and cholestyramine were added for his hyperbilirubinemia.

OUTCOMES

Four weeks from admission, the patient returned to near baseline functional status and was discharged home.

LESSONS

This case highlights that ATLL can initially present as isolated acute hepatitis, and how careful examination of peripheral blood-smear may elucidate hepatitis etiology. We also present support for utilizing ursodiol with cholestyramine for treating a hyperbilirubinemia. Moreover, unlike prior reports of ATLL presenting as liver dysfunction, combined antiviral and CVP chemotherapy was effective in this case. Lastly, there are seldom demographic reports of HTLV-1 infection from the Micronesian area, and our case represents the first indexed case of HTLV-1-associated-ATLL presenting as acute liver failure in a Marshallese patient.

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.

Distribution of human T cell lymphotropic virus type 1 (HTLV-1) subtypes in Brazil: genetic characterization of LTR and tax region

We report the molecular and epidemiological characterization of 128 human T cell lymphotropic virus type 1 (HTLV-1) isolates from Brazilian patients with different clinical manifestations of the infection. Thirty-two percent of the patients were asymptomatic, 44% had HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), and 23% had adult T cell leukemia/lymphoma (ATLL). Phylogenetic analysis performed using part of the LTR region of the viral genome revealed that all Brazilian isolates belonged to the Cosmopolitan subtype, with the following distribution within the Transcontinental subgroup: 81.6% within the Latin American cluster and 15.8% outside the Latin American cluster. Two isolates belonged to the Japanese subgroup. Molecular analysis of the tax region showed a high nucleotide similarity ( approximately 99%) with 41 prototype sequences, including the ATK-1 isolate. The mean number of nucleotide substitutions ranged from 1 to 8. Five specific nucleotide substitutions, C7401T, T7914C, C7920T, C7982T, and G8231A, were highly conserved among the Brazilian isolates (79.6%), with a frequency ranging from 81.6% to 100% in the sample group and from 18.4% to 24.1% in the prototypes used, suggesting the existence of a molecular signature. These changes were not correlated with a specific clinical status of the patients and could be a molecular characteristic of the HTLV-1 strains that circulate in Brazil.

Sequence and phylogenetic analysis of human T cell lymphotropic virus type 1 from Tumaco, Colombia

Human T cell lymphotropic virus type 1 (HTLV-1) is a retrovirus that causes leukemia and the neurological disorder HTLV-1 associated myelopathy or tropical spastic paraparesis (HAM/TSP). Infection with this virus - although it is distributed worldwide - is limited to certain endemic areas of the world. Despite its specific distribution and slow mutation rate, molecular epidemiology on this virus has been useful to follow the movements of human populations and routes of virus spread to different continents. In the present study, we analyzed the genetic variability of a region of the env gene of isolates obtained from individuals of African origin that live on the Pacific coast of Colombia. Sequencing and comparison of the fragment with the same fragment from different HTLV-1 isolates showed a variability ranging from 0.8% to 1.2%. Phylogenetic studies permit us to include these isolates in the transcontinental subgroup A in which samples isolated from Brazil and Chile are also found. Further analyses will be necessary to determine if these isolates were recently introduced into the American continent or if they rather correspond to isolates introduced during the Paleolithic period.

Envelope sequence variation and phylogenetic relations of human T cell lymphotropic virus type 1 from endemic areas of Colombia

The HTLV-1 envelope gene of 12 TSP/HAM patients from two endemic areas of southwest Colombia (Tumaco and Buenaventura) was amplified by nested PCR, sequenced, and compared with previously reported HTLV-1 envelope sequences from isolates worldwide. In general, the sequence divergences among all Colombian samples ranged from 0.1 to 1.6%. Some amino acid substitutions, referring to the ATK-1 prototype strain in the surface domain gp46 and in p21, were highly prevalent in southwest Colombia, suggesting a geographical clustering of mutations in the envelope gene. The phylogenetic analysis showed that the Colombian isolates belong to the HTLV-1a lineage with minor subgroups. The genetic distance between Colombian and Japanese isolates ranged from 0.1 to 1.8%; in comparison, the genetic distance between Colombian and Caribbean isolates ranged from 0.4 to 2.2%. Our results strongly suggest that the actual quasispecies populations in southwest Colombia have been generated by separate, differently timed introductions of virus.

Genetic characterization and phylogeny of human T-cell lymphotropic virus type I from Chile

Infection with Human T-Cell Lymphotropic Virus type I (HTLV-I) have been associated with the development of the HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP). Phylogenetic analyses of HTLV-I isolates have revealed that HTLV-I can be classified into three major groups: the Cosmopolitan, Central African and Melanesian. In the present study, we analyzed the tax, 5' ltr, gag, pol, and env sequences of proviruses of PBMC from ten HAM/TSP patients to investigate the phylogenetic characterization of HTLV-I in Chilean patients. HTLV-I provirus in PBMC from ten Chilean patients with HAM/TSP were amplified by PCR using primers of tax, 5' ltr, gag, pol, and env genes. Amplified products of the five genes were purified and nucleotide sequence was determined by the dideoxy termination procedure. DNA sequences were aligned with the CLUSTAL W program. The results of this study showed that the tax, 5' ltr, gag, pol, and env gene of the Chilean HTLV-I strains had a nucleotide homology ranged from 98.1 to 100%, 95 to 97%, 98.9 to 100%, 94 to 98%, and 94.2 to 98.5% respect to ATK-1 clone, respectively. According to molecular phylogeny with 5' ltr gene, the Chilean HTLV-I strains were grouped with each other suggesting one cluster included in Transcontinental subgroup.

Risk of transfusion-transmitted human T-cell lymphotropic virus-type I in Latin America

In a recent publication, G. Schmunis et al presented data from Latin America on blood quality and on important approaches to preventing human immmunodeficiency virus (HIV), acquired immunodeficiency syndrome (AIDS), and other infectious diseases that may be transmitted by blood transfusion. Mass screening between 1987 and 1988 in Peru of blood from more than 90,000 donors highlighted potential problems in the donor population, and it also uncovered inappropriate practices related to the use of blood transfusions. Since then, adequate screening of the blood supply for HIV was implemented and new transfusion-related AIDS cases have been prevented during the past 8 years.

Human T-cell lymphotropic virus-I in Latin America

HTLV-1 infection is endemic in several Latin American countries. HTLV-1-associated myelophathy/tropical spastic paraparesis (HAM/TSP) and adult T-cell leukemia lymphoma (ATLL) are emerging diseases in the region. Documented risk factors for acquiring the virus include breast-feeding, contaminated blood transfusion, and sexual intercourse, all of which are amenable to prevention efforts. Strongyloides stercoralis hyperinfection syndrome and therapeutic failure in apparently healthy patients with nondisseminated strongyloidiasis may be markers of HTLV-1 infection. HTLV-1 co-infection may adversely effect the clinical course of scabies and HIV disease. The new enzyme-linked immunosorbent assays (ELISA) are sensitive and specific, and Western blot technology is reliable for differentiating HTLV-1 from less common HTLV-2. HTLV-1 screening of blood donors and individuals with any disorder that suggests infection has become a necessity in Latin America to prevent the spread of this important emerging pathogen.

Sequence analysis of human T cell lymphotropic virus type I (HTLV-I) Env genes amplified from central nervous system tissues of patients with HTLV-I-associated myelopathy or leukemia

Human T cell lymphotropic virus type I (HTLV-I) is a retrovirus that has been linked to HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP), a chronic or inflammatory neurological disease with some resemblance to multiple sclerosis. We used the polymerase chain reaction to amplify viral env genes in foci of inflammation and demyelination in the nervous system to adduce additional evidence of the association of HTLV-I with the neuropathological changes in HAM/TSP, and document in this report such an association. We also sought evidence of a distinct viral species in the lesions by amplifying, cloning and sequencing the env genes from tissues sections in which there were pathological changes. We did not find changes in the env gene that correlated with HTLV-I-associated neurological disease vs adult T cell leukemia or with the nervous system vs peripheral blood and lymphoid organs. We did, however, find evidence of extensive mutation and possibly deletions in the env gene in HTLV-I-associated neurological disease. We interpret these findings of increased genetic diversity as a reflection of higher rates of viral replication in HTLV-I-associated myelopathy that support a model of pathogenesis in which increased viral replication activates immune cells that subsequently enter the nervous system and cause injury by immunopathological mechanisms.

Human T-lymphotropic virus type 1 in coastal natives of British Columbia: phylogenetic affinities and possible origins

Human T-lymphotropic virus type 1 (HTLV-1) infection has been discovered recently in people of Amerindian descent living in coastal areas of British Columbia, Canada. DNA sequencing combined with phylogenetic analysis and restriction fragment length polymorphism (RFLP) typing of HTLV-1 strains recovered from these British Columbia Indians (BCI) was conducted. Sequence-based phylogenetic trees distributed the BCI isolates among the Japanese subcluster (subcluster B) and the geographically widely distributed subcluster (subcluster A) of the large HTLV-1 cosmopolitan cluster. Long terminal repeat (LTR) RFLP typing revealed three distinct, equally frequent LTR cleavage patterns, two of which were of previously recognized Japanese and widely dispersed cosmopolitan types. A third, new cleavage pattern was detected which may have arisen by recombination between two other HTLV-1 genotypes. Our results suggest multiple origins for HTLV-1 in BCI, which are equally consistent with (i) a cluster of recent sporadic infections, (ii) ancient endemic vertical transmission through Amerindian lineages, or (iii) both.

Lymphomatous meningoencephalitis in a patient with HAM/TSP

A case of lymphomatous meningoencephalitis in a 23 year old Brazilian patient with HTLV-I/II associated myelopathy is reported. The patient was admitted to the hospital with a clinical picture of decreased consciousness level, stiffness of the neck and previous diagnosis of myeloneuropathy. CSF examination showed lymphocytosis with blastic cells and antibodies against HTLV-I/II.

HTLV-negative and HTLV type I-positive tropical spastic paraparesis in northeastern Brazil

A type-specific serological survey among 1042 random nonneurological outpatients in two cities in the state of Ceara (northeastern Brazil) shows a low prevalence of HTLV-I (0.34% in Fortaleza; 0.44% in Crato) and of HTLV-II (0.34% in Fortaleza; 0% in Crato). Among 62 chronic myelopathic patients seen in Fortaleza 27 patients were found with clinical features of tropical spastic paraparesis (TSP); 10 of 27 were found HTLV-I seropositive (37%; 95% confidence limits, 19-58%). Proviral genome detection by polymerase chain reaction in 5 seropositive and 12 seronegative patients confirmed the serological findings. This excludes HTLV-I or -II infection as a cause in the seronegative TSP patients. The HTLV-positive and -negative patients did not differ clinically and by history, except that seropositives had a longer mean disease duration, a female predominance, and a higher proportion of white Caucasians. In this population with low HTLV-I and HTLV-II prevalences, HTLV-negative TSP is at least as frequent as the HTLV-I-associated TSP.

Human T-lymphotropic virus type I (HTLV-I)-specific antibodies and cell-free RNA in crevicular fluid-rich saliva from patients with tropical spastic paraparesis/HTLV-I-associated myelopathy

Despite the likely role of mucosae in human T cell leukemia virus type I (HTLV-I) transmission, little is known about the mucosal immune response to HTLV-I. The present study evaluated the antibody response to HTLV-I in oral mucosa and the value of crevicular fluid rich saliva (CFRS) for diagnosing HTLV-I infection. CFRS and sera from patients with tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM), asymptomatic carriers, and HTLV-I seronegative individuals from Tumaco, Colombia, were analyzed for HTLV-I specific IgG, IgA, and secretory IgA (sIgA). Detection of IgG in CFRS by enzyme-linked immunosorbent assay correlated with its presence in sera for TSP/HAM patients and asymptomatic carriers. IgA and sIgA were more frequently detected in CFRS and sera from TSP/HAM patients than in those from asymptomatic carriers. An HTLV-I pol fragment could be amplified from CFRS by reverse transcriptase-PCR in 3 TSP/HAM patients and one asymptomatic carrier, all of whom had an IgA response in CFRS but not in sera. The more frequent detection of IgA and sIgA in sera and CFRS of TSP/HAM patients suggests increased viral replication. Further, the association of viral RNA in CFRS with a local IgA response may signify rounds of viral replication in the oral cavity.

Familial transmission and minimal sequence variability of human T-lymphotropic virus type I (HTLV-I) in Zaire

Our group previously reported a strong familial clustering of HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP) in Zaire, suggesting a familial transmission of the virus together with the presence of cofactors. In the present study among 84 relatives of 16 HTLV-I-positive or HAM/TSP index cases, we found that all 15 seropositive children had a seropositive mother and that all 15 children with a seropositive father but a seronegative mother were seronegative. Lymphocytes of 17 relatives from 2 families with a familial HTLV-I-associated neuropathy were tested in 2 polymerase chain reaction (PCR) assays amplifying pol and tax/rex gene fragments. The 10 seropositive individuals were PCR positive for HTLV-I and the 7 seronegatives were negative in both PCR assays. The PCR results showed no evidence for a long lag period between infection with HTLV-I and seroconversion. The HTLV-I long terminal repeat (LTR) of these 10 individuals, related in the first to the fourth degree, was amplified and sequenced. Identical sequences were found within the families except for one woman infected with two variants, one being the familial strain and the other a mutated one with a single nucleotide substitution in the 755 sequenced nucleotides of the LTR region. The family strain and the mutant were both present in two samples taken 1 year apart. Together, the HTLV-I serology, PCR, and sequencing results point toward mother-to-child transmission as the main mode of HTLV-I infection in this population. Comparison of the LTR sequences of the two families with other HTLV-I strains from different geographical regions shows that the Zairean HTLV-I strains form a separate cluster.(ABSTRACT TRUNCATED AT 250 WORDS)

Tropical spastic paraparesis/HTLV-I associated myelopathy. Etiology and clinical spectrum

In 1985 we had the first indication that human T-cell lymphotropic virus (HTLV-I) was the possible etiological agent of a chronic myelopathy that seemed to be peculiar to the tropics and that is now known as endemic tropical spastic paraparesis (TSP). IgG antibodies to HTLV-I were found in serum and cerebrospinal fluid of patients from Jamaica, Colombia, Martinique, and shortly after in southern Japan, where the disease is called HTLV-I-associated myelopathy (HAM). The HTLV-I seropositivity was first determined by enzyme-linked immunoassay and confirmed by western immunoblot and in the cerebrospinal fluid specific IgG oligoclonal bands to HTLV-I were found in cerebrospinal fluid and not in serum. These laboratory findings indicated that HTLV-I could be neuropathogenic and for the first time a single etiological agent was identified in patients from different countries. Thus, in less than a decade a century of research and speculation was seemingly resolved when this disease, which was thought to occur only in blacks of poor socioeconomic status in tropical countries, was shown to occur in all ethnic groups of varying socioeconomic status in temperate, subtropical, and tropical climates.

HTLV-1 and myelopathy in Salvador (northeastern Brazil): a case control study

The principal aim of the study was to determine the degree of association between cerebrospinal fluid (CSF) that is positive for HTLV-1 and myelopathy in Salvador, Brazil. From the same hospital, twenty-eight cases of myelopathy and twenty-eight cases showing no neurological disorder were studied using blind selection matched 1:1 by age and sex. The twenty-eight pairs underwent HTLV-1 serology tests. In those with a positive result, anti-HTLV-1 antibodies were investigated in the CSF. The ELISA method was used, complemented by the Western-blot test. Myelopathy was considered associated with HTLV-1 only when the CSF was positive indicating neurotropism of the virus. The mean age of the cases was 44.6 +/- 15.6 years and the control group was 43.5 +/- 16.0 (p > 0.05). An OR of 9.0 was detected with a reliability interval (95%) of 1.652-48.866 and chi-square significant at the 0.02 level. Despite a strong degree of association and considering the low level of precision, there is a need for analytical studies with larger samples which besides improving the precision will allow for greater control of the confounding variables.

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.

The cutaneous form of adult T-cell leukemia/lymphoma in a woman from the Ivory Coast. Clinical, immunovirologic studies and a review of the African adult T-cell leukemia/lymphoma cases

A 36-year-old woman from Ivory Coast, who has lived in France since 1976, had multiple cutaneous nodules and tumors in 1988. Histopathologic studies showed a massive infiltration of the dermis and hypodermis by a diffuse proliferation of mature activated T-cells (CD4-positive, CD25-positive, HLA-DR-positive) with irregular nuclei. The patient did not present with a leukemic picture and only few lymphoid cells with abnormally shaped nuclei were present in the blood. Human T leukemia/lymphoma virus type I (HTLV-I) antibodies were present in the serum and specific HTLV-I pol sequences were detected in the DNA extracted from the tumor nodules and peripheral blood mononuclear cells (PBMC) using the polymerase chain reaction technique. Whereas only a polyclonal integration of HTLV-I provirus was detectable in the PBMC, a clonal integration of three HTLV-I proviruses was demonstrated in the tumor nodules DNA, establishing with certainty the diagnosis of HTLV-I-induced adult T-cell leukemia/lymphoma (ATL). This case illustrates the need for molecular studies to differentiate without ambiguity an ATL from any other type of cutaneous lymphoproliferation, even when it occurs in a HTLV-I-seropositive individual. The situation of HTLV-I-associated ATL in Africa is reviewed.

Human T-cell lymphotropic virus type I and II in transfusion medicine

As a consequence of migrating populations, IV drug use and, to a lesser extent, blood transfusions, endemic HTLV-I and HTLV-II infections have spread to nonendemic geographic regions. Although the risk that a person infected with HTLV-I will develop significant disease--even over a lifetime--is estimated to be relatively low, our awareness of the serious diseases associated with other retroviruses requires a cautious approach to blood transfusion. Reports from Japan and the United States indicate that programs testing donated blood and excluding units with HTLV-I antibodies have been highly successful in interrupting the spread of HTLV-I by transfusions. One unanticipated outcome of testing large numbers of people in the United States for HTLV-I antibodies has been recognition of the relatively high prevalence of HTLV-II infection, particularly among IV drug users. The long-term effects of HTLV-II infection are also unknown. Until the natural history and clinical consequences of HTLV-II infection are clearly understood, it is only prudent that blood donated by persons identified to be HTLV-II carriers also be excluded.

In situ hybridization detection of HTLV-I RNA in peripheral blood mononuclear cells of TSP/HAM patients and their spouses

This is the first report of the direct detection of HTLV-I RNA in uncultured peripheral blood mononuclear cells (PBMNC's) of patients with tropical spastic paraparesis and HTLV-I-associated myelopathy (TSP/HAM) and their spouses, using the technique of in situ hybridization. Twenty-one Colombian patients were tested, all of whom had antibodies to HTLV-I; the presence of HTLV-I proviral DNA in their PBMNC's was confirmed by the polymerase chain reaction technique. Of the 21 patients 15 had a clinical diagnosis of tropical spastic paraparesis (TSP/HAM), 5 were asymptomatic relatives, and 1 patient had leukemia. In situ hybridization was positive in samples from 5 patients; 2 of these were TSP/HAM patients and the other 3 were healthy wives of TSP/HAM patients. This study demonstrates for the first time that viral RNA is expressed in uncultured PBMNC's of some patients with TSP/HAM in whom proviral DNA is also present; furthermore, the detection of HTLV-I RNA in the blood of female partners of TSP/HAM patients clearly illustrates the high likelihood of HTLV-I transmission through sexual contact.

High prevalence of human T-lymphotropic virus type I infection in isolated populations of the Western Pacific region confirmed by Western immunoblot

High prevalences of antibodies against human T-lymphotropic virus type I (HTLV-I), as confirmed by Western immunoblot, were found in several remote indigenous populations of the Solomon Islands and Vanuatu and in some isolated populations of New Guinea that had no contact with Japanese or Africans and little contact with Caucasians prior to our bleedings. By contrast, zero or very low prevalences of HTLV-I infection were found in Guamanians and Carolinians, despite more than 30 years of intense contact with the Japanese. A total of 1,601 sera, collected between 1963 and 1981 from 21 population groups in the Western Pacific, was tested by enzyme-linked immunosorbent assay (ELISA) for IgG antibodies to HTLV-I. By ELISA, prevalences of antibodies against HTLV-I ranged from zero to 50%. Seropositivity could be confirmed in only 12.5% of 48 ELISA-positive sera selected for testing by Western immunoblot. However, the confirmed HTLV-I seroprevalences in some Melanesian populations were still as high as those found in HTLV-I-endemic regions, such as southwestern Japan and the Caribbean basin. HTLV-I prevalences were similar among males and females, and acquisition of antibodies increased with age. Our data indicate that infections with HTLV-I or a related retrovirus have been widespread in the southwestern Pacific for over 25 year in populations with minimal outside contact, while some populations which had extensive Japanese contact have no evidence of infection. Furthermore, based on the high frequency of indeterminate Western immunoblots, we conclude that in Melanesia this may represent either incomplete specific reactivity to HTLV-I or the existence of an antigenic variant of HTLV-I, distinct from prototype Japanese, American, and European HTLV-I strains.

A cluster of HTLV-1 associated tropical spastic paraparesis in Equateur (Zaire): ethnic and familial distribution

In Lisala, Equateur province, Zaire, 25 patients from 21 pedigrees were identified with human T-lymphotropic virus type 1 (HTLV-1) associated tropical spastic paraparesis (TSP). In the 10 (48%) pedigrees with additional genuine TSP cases established mainly by history, seven of 10 patients' mothers, no fathers or spouses, one of 59 surviving offspring, five of 105 siblings, and six other close blood relatives had TSP. A child may develop TSP before its mother. Three familial cases were in paternal relatives only. In total, 39 cases (11 men, 28 women) were identified in this population of about 50,000. Half were in the Mundunga minority of less than or equal to 10% (p less than 0.001). The data suggest maternal transmission of HTLV-1 and enhanced TSP susceptibility in those infected due to familial, probably genetic factors.

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

To evaluate altitude of birthplace and residence as factors associated with geographic clustering of HTLV-I infection in Colombia, we sampled a total of 670 current residents of the South Pacific coastal lowland and of upland regions (Cali and environs) of the Valle and Cauca Provinces, located at an altitude of 3,100 ft. Among the 255 lowland study subjects, 4.3% had antibody against HTLV-I, compared to 0.9% of the 415 upland study subjects. A hypothesis emerging from this study is that the lower socio-economic status of lowland residents and associated diseases, particularly untreated syphilis and other sexually transmitted diseases, may explain the increased HTLV-I seropositivity rates in this population.