Lack of tax diversity for tropical spastic paraparesis/human T-cell lymphotropic virus type 1 (HTLV-I) associated myelopathy development in HTLV-I-infected subjects in São Paulo, Brazil

The product of human T-cell lymphotropic virus type 1 (HTLV-1) tax gene has a transactivating effect of the viral and cellular gene expression. Genetic variations in this gene have been correlated with differences in clinical outcomes. Based upon its diversity, two closely related substrains, namely tax A and tax B, have been described. The tax A substrain has been found at a higher frequency among human T-cell leukemia virus type 1 (TSP/HAM) patients than among healthy HTLV-I-infected asymptomatic subjects in Japan. In this study, we determined the distribution of tax substrains in HTLV-I-infected subjects in the city of S?o Paulo, Brazil. Using the ACCII restriction enzyme site, we detected only tax A substrain from 48 TSP/HAM patients and 28 healthy HTLV-I carriers. The sequenced tax genes from nine TSP/HAM patients and five asymptomatic HTLV-I carriers showed a similar pattern of mutation, which characterizes tax A. Our results indicate that HTLV-I tax subtypes have no significant influences on TSP/HAM disease progression. Furthermore, monophyletic introduction of HTLV-I to Brazil probably occurred during the African slave trade many years ago.     

Genetic control and dynamics of the cellular immune response to the human T-cell leukaemia virus, HTLV-I.

About 1% of people infected with the human T-cell leukaemia virus, type 1 (HTLV-I) develop a disabling chronic inflammatory disease of the central nervous system known as HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP). Patients with HAM/TSP have a vigorous immune response to HTLV-I, and it has been widely suggested that this immune response, particularly the HTLV-I-specific cytotoxic T-lymphocyte (CTL) response, causes the tissue damage that is seen in HAM/TSP. In this paper we summarize recent evidence that a strong CTL response to HTLV-I does in fact protect against HAM/TSP by reducing the proviral load of HTLV-I. We conclude that HTLV-I is persistently replicating at a high level, despite the relative constancy of its genome sequence. These results imply that antiretroviral drugs could reduce the risk of HAM/TSP by reducing the viral load, and that an effective anti-HTLV-I vaccine should elicit a strong CTL response to the virus. The dynamic nature of the infection also has implications for the epidemiology and the evolution of HTLV-I.     

Genetic and phylogenetic analyses of human T-cell lymphotropic virus type I variants from Melanesians with an without spastic myelopathy

Molecular variants of human T-cell lymphotropic virus type I (HTLV-I) have been isolated recently from lifelong residents of remote Melanesian populations, including a Solomon Islander with tropical spastic paraparesis/HTLV-I-associated myelopathy (TSP/HAM) or HTLV-I myeloneuropathy. To clarify the genetic heterogeneity and molecular epidemiology of disease-associated strains of HTLV-I, we enzymatically amplified, then directly sequenced representative regions of thegag, pol, env, andpX genes of HTLV-I strains from Melanesians with and without TSP/HAM, and aligned and compared these sequences with those of HTLV-I strains from patients with TSP/HAM or adult T-cell leukemia/lymphoma and from asymptomatic carriers from widely separated and culturally disparate populations. Overall, the HTLV-I variant from the Solomon Islander with TSP/HAM, like HTLV-I strains from asymptomatically infected Melanesians, diverged by approx 7% from cosmopolitan HTLV-I strain. No disease-specific viral sequences were found. Gene phylogenies, as determined by the unweighted pair-goup method of assortment and by the maximum parsimony method, indicated that the Melanesian and cosmopolitan strains of HTLV-I have evolved along separate geographically dependent lineages, one comprised of HTLV-I strains from Papua New Guinea and the Solomon Islands, and the other composed of virus strains from Japan, India, the Caribbean, Polynesia, the Americas, and Africa. The total absence of nonhuman primates in Papua New Guinea and the Solomon Islands precludes any possibility that the Melanesian HTLV-I strains have evolved recently from the simian homolog of HTLV-I.     

The transactivator gene of human T-cell leukemia virus type I is more variable within and between healthy carriers than patients with tropical spastic paraparesis.

Human T-cell leukemia virus type I (HTLV-1) causes T-cell leukemia and tropical spastic paraparesis (TSP) in a minority of infected people, whereas the majority remain healthy. No association between a particular HTLV-I sequence and disease manifestation has been found in previous studies. We studied here the sequence variability of the gene for the HTLV-I Tax protein, which is the dominant target antigen of the very strong cytotoxic T-lymphocyte response to the virus. In HTLV-I infection, the intraisolate nucleotide variability is much greater than the variability between isolates. The predicted protein sequence of Tax was significantly more variable in the healthy seropositive individuals' provirus than in those of the patients with TSP. Thus, tax sequence heterogeneity, rather than the presence of particular sequences, distinguishes healthy HTLV-I-seropositive individuals from patients with TSP.     

Soluble HTLV-I Tax1 protein stimulates proliferation of human peripheral blood lymphocytes.

Human T-cell leukemia virus type I (HTLV-I) is associated with two human diseases, adult T-cell leukemia (ATL) and tropical spastic paraparesis/HTLV-I associated myelopathy (TSP/HAM). Lymphocytes from patients with ATL or TSP/HAM display abnormal proliferation properties in culture. Here we report that purified, soluble Tax1 protein can be taken up by, and stimulate proliferation of, uninfected human peripheral blood lymphocytes (PBLs) that have been stimulated with phytohemagglutinin (PHA). Tax1 was 40 to 70% as active as interleukin-2 (IL-2) in stimulating proliferation of PBLs. Heat inactivation, chloroform extraction, and immunoprecipitation with antisera specific for Tax1 each abolished the ability of the protein to stimulate lymphocyte proliferation. Tax1 failed to stimulate PBL proliferation in the absence of PHA. After an initial round of cell division, Tax1-treated PBLs exhibited prolonged sensitivity to IL-2-induced proliferation. These results indicate that Tax1 can stimulate lymphocyte proliferation in culture and imply that extracellular Tax1 may be involved in the spontaneous proliferation of TSP/HAM lymphocytes and the IL-2-dependent proliferation of ATL lymphocytes.     

Tax mutation associated with tropical spastic paraparesis/human T-cell leukemia virus type I-associated myelopathy.

Tumaco, Colombia, is an area with elevated rates of tropical spastic paraparesis/human T-cell leukemia virus type I (HTLV-I)-associated myelopathy (TSP/HAM). We have identified a mutation in nucleotide 7959 of the tax gene of 14 Tumaco HTLV-I isolates (14 positive of 14 tested) that was present in 5 of 14 (35%) TSP/HAM patients from Japan and in 8 of 11 (72%) TSP/HAM patients from other geographic locations. In contrast, this mutation was found in only 2 of 21 (9.5%) HTLV-I-infected subjects outside of Tumaco who did not have TSP/HAM. tax clones with nucleotide mutations including one at nucleotide 7959 showed a greater ability to transactivate the HTLV-I U3 promoter. However, this effect was not observed when two clones that differed only in nucleotide 7959 were compared. These results suggest that HTLV-I-infected individuals carrying isolates with this tax mutation are at higher risk for developing TSP/HAM.     

HIV and HTLV-I antibody studies: pregnant women in the 1960s, patients with AIDS, homosexuals, and individuals with tropical spastic paraparesis

To investigate the possible occurrence of human immunodeficiency virus (HIV) or human T-cell lymphotropic virus, type I (HTLV-I) infections in the United States prior to 1979-1981, when acquired immune deficiency syndrome (AIDS) was first recognized, we tested sera from 310 pregnant women who participated in the Collaborative Perinatal Project during the period 1959-1964 for HIV and HTLV-I antibody. These samples included sera from 53 pregnant women who were intravenous drug users. The remainder were from women who had cervical epithelial abnormalities, who developed cervical carcinomas, who had had children with erythroblastosis fetalis, who had had children that developed malignant neoplasms early in life, or normal pregnant women. None of the 310 women had confirmed HIV or HTLV-I antibody. The rate of false-positive reactions with the HIV enzyme-linked immunosorbent assay (ELISA) antibody test in these long-frozen samples was similar to that observed in fresh sera. HIV antibody was detected in homosexual patients with AIDS; HTLV-I antibody was not detected in any of these sera. HTLV-I antibody was detected in 17 of 20 patients with tropical spastic paraparesis (TSP) and in two of seven patients with other neurological diseases diagnosed as transverse myelopathy and multiple sclerosis, and in none of nine normal controls; HIV antibody was not detected in any of these sera patients. Thus, we conclude that there was no serological evidence of infection with HIV or HTLV-I in the pregnant women studied; however, HIV antibody was present in all AIDS patients tested, and HTLV-I antibody was found in the majority of patients with TSP.     

The presence of HTLV-I proviral DNA in the central nervous system of patients with HTLV-I-associated myelopathy/tropical spastic paraparesis

Human T-lymphotropic virus type 1 (HTLV-I) is a pathogenic retrovirus associated with a chronic progressive myelopathy, termed HTLV-I-associated myelopathy (HAM)/tropical spastic paraparesis (TSP), as well as adult T-cell leukemia (ATL). A chronic inflammatory process has been implicated in HAM/TSP by a pathological study, but the exact mechanism still remains unknown. To understand better the complex mechanism of disease induction by HTLV-I, I studied the spreading pattern of HTLV-I in both peripheral blood mononuclear cells (PBMNCs) and central nervous system (CNS) tissues in patients with HAM/TSP using a quantitative polymerase chain reaction (PCR) method. My results indicated the primary event to be the efficient replication of HTLV-I in vivo, whereas HTLV-I is likely to be present in the constituent cells of the CNS in addition to the infiltrating mononuclear cells.     

Human T-cell lymphotropic virus type I infection and disease in the Pacific basin.

Human T-cell lymphotropic virus type I (HTLV-I), the cause of adult T-cell leukemia/lymphoma (ATLL) and HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), is widespread in the Pacific basin. Modes of virus transmission include blood transfusion (and intravenous drug use), breast milk, and sexual intercourse. High prevalences of HTLV-I infection and disease occur among the inhabitants of southwestern Japan and among first- and second-generation (issei and nisei) Japanese-Americans in the Hawaiian Islands. Other Pacific populations with high prevalences of HTLV-I infection include several remote groups in West New Guinea, Papua New Guinea, the Solomon Islands, and Vanuatu, which have had no contact with Japanese or Africans. By contrast, Micronesian and Polynesian populations, even those with prolonged contact with Japanese, exhibit low prevalences or no evidence of HTLV-I infection. Low prevalences of infection are also found in Australia, except among some aboriginal populations. Changing patterns of HTLV-I infection and disease are no better exemplified than in Japan, where striking reductions in transfusion-acquired infection and subsequent development of HAM/TSP have followed the institution of nationwide screening of blood donors for HTLV-I infection. Furthermore, virus transmission from mother to infant by means of infected breast milk has been markedly curtailed in HTLV-I-hyperendemic regions in Japan by interrupting the practice of breast feeding by HTLV-I-infected mothers. The next frontier of HTLV-I research is in Melanesia, where highly divergent sequence variants of HTLV-I have been discovered.     

Increase in T-Cells Bearing CD25 in Bronchoalveolar Lavage Fluid from HAM/TSP Patients and HTLV-I Carriers

To determine the immunologic characteristics of T-cells in local pulmonary lesions of human T-cell lymphotropic virus type I (HTLV-I) carriers, we investigated lymphocyte surface markers in peripheral blood and bronchoalveolar lavage fluid (BALF) of 38 HTLV-I carriers, 8 HTLV-I associated myelopathy/tropical spastic paraparesis (HAM/TSP) patients, 44 HTLV-I seronegative patients with pulmonary diseases and 7 healthy volunteers using two-color flow cytometric analysis. In peripheral blood, activated T-cells, CD4+HLA-DR +, CD8 + HLA-DR + and CD3 + CD25 +, and CD4+CD29+ cells increased significantly in carriers and HAM/TSP patients compared with healthy volunteers and seronegative patients. In BALF, T-cells, especially CD25+ cells, increased significantly in carriers and HAM/TSP patients, compared with healthy volunteers and seronegative patients. These findings indicated that T-cells in the lungs, as well as in peripheral blood, are activated in carriers and HAM/TSP patients. Interestingly, there was dissociation between expression of CD3 + CD25+ cells in BALF and peripheral blood from these patients. These results suggest that T-cells activated probably by HTLV-I accumulate in the lungs in some carriers and HAM/TSP patients, and HTLV-I may be involved in the immunologic dysfunction in the lungs of these patients. However, we did not find any correlation between the degree of clinical features and the elevation of CD3 + CD25+ cells in BALF, or its characteristic features on chest roentgenograms.     

Detection of HTLV-I in peripheral blood lymphocytes from patients with chronic HTLV-I-associated myelopathy/tropical spastic paraparesis and asymptomatic carriers by PCR-in situ hybridization

Less than 5% of people infected with human T-lymphotropic virus type I (HTLV-I) develop HTLV-I-associated myelopathy/tropical spastic paraparesis (HAM/TSP), a chronic progressive neurologic disease. A number of factors have been implicated in the development of HAM/TSP including heterogeneity of viral sequences, host-genetic background, viral-specific cellular immune responses and viral load. This study examined the presence of HTLV-Itax DNA in peripheral blood lymphocytes (PBL) from 2 chronic HAM/TSP patients and 2 asymptomatic HTLV-I carriers by using PCR-in situ hybridization (PCR-ISH) for the in situ presence of proviral HTLV-Itax DNA. By this technique, rare PBL from these HTLV-I-infected individuals contained HTLV-I DNA. PCR-ISH did not detect any difference in the number of infected cells between HAM/TSP patients and asymptomatic carriers.     

Modelling the Role of Tax Expression in HTLV-I Persistence in vivo

Human T-lymphotropic virus type I (HTLV-I) is a persistent human retrovirus characterized by life-long infection and risk of developing HAM/TSP, a progressive neurological and inflammatory disease, and adult T-cell leukemia (ATL). Chronically infected individuals often harbor high proviral loads despite maintaining a persistently activated immune response. Based on a new hypothesis for the persistence of HTLV-I infection, a three-dimensional compartmental model is constructed that describes the dynamic interactions among latently infected target cells, target-cell activation, and immune responses to HTLV-I, with an emphasis on understanding the role of Tax expression in the persistence of HTLV-I.     

The influence of HLA class I alleles and heterozygosity on the outcome of human T cell lymphotropic virus type I infection

The inflammatory disease human T cell lymphotropic virus type I (HTLV-I)-associated myelopathy (HAM/TSP) occurs in only 1-2% of HTLV-I-infected individuals and is associated with a high provirus load of HTLV-I. We hypothesize that a person's risk of developing HAM/TSP depends upon the efficiency of their immune response to the virus, which differs between individuals because of polymorphism in genes that influence this response. Previously we showed that the possession of HLA-A*02 was associated with a lower risk of HAM/TSP, and with a lower provirus load in healthy carriers of HTLV-I. However, HLA-A*02 did not account for all the observed difference in the risk of HAM/TSP. Here we present evidence, in the same study population in Japan, that HLA-Cw*08 was also associated with disease protection (probability value, two-tailed test = 0.002) and with a lower proviral load in healthy carriers. Possession of the A*02 and/or Cw*08 genes prevented 36% of potential HAM/TSP cases. In contrast, HLA-B*5401 was associated with a higher susceptibility to HAM/TSP (probability value, two-tailed test = 0.0003) and with a higher provirus load in HAM/TSP patients. At a given provirus load, B*5401 appeared to increase the risk of disease. The fraction of HAM/TSP cases attributable to B*5401 was 17%. Furthermore, individuals who were heterozygous at all three HLA class I loci have a lower HTLV-I provirus load than those who were homozygous at one or more loci. These results are consistent with the proposal that a strong class I-restricted CTL response to HTLV-I reduces the proviral load and hence the risk of disease.     

Chipping at large, potent human T-cell leukemia virus type 1 protease inhibitors to uncover smaller, equipotent inhibitors

The human T-cell leukemia virus type 1 (HTLV-I) causes adult T-cell leukemia and several severe chronic diseases. HTLV-I protease (PR) inhibition stops the propagation of the virus. Herein, truncation studies were performed on potent octapeptidic HTLV-I PR inhibitor KNI-10161 to derive small hexapeptide KNI-10127 with some loss in activity. After performing residue-substitution studies on compound KNI-10127, HTLV-I PR inhibitory activity was recovered in inhibitor KNI-10166.