Low prevalence in the UK of HTLV-I and HTLV-II infection in subjects with AIDS, with extended lymphadenopathy, and at risk of AIDS

A New Flow Cytometry-Based Single Platform for Universal and Differential Serodiagnosis of HTLV-1/2 Infection

In the present work, we developed and evaluated the performance of a new flow cytometry-based single platform, referred to as “FC-Duplex IgG1 (HTLV-1/2)”, for universal and differential serodiagnosis of HTLV-1/2 infection. The proposed technology employs a system for detection of IgG1 antibodies in a single competitive immunofluorescence platform by flow cytometry using fluorescently labeled MT-2/MoT cell line mix coupled to a highly sensitive development system (Biotin/Streptavidin/Phycoerythrin). The stability of fluorescent labeling and the antigenicity of MT-2 and MoT cell lines were confirmed upon storage at −20°C for 2, 6, and 12 months. The anti-HTLV-1/2 IgG1 reactivity, expressed as percentage of positive fluorescent cells (PPFC), was evaluated for each target antigen along the titration curve of test serum samples (1:32 to 1:4,096). Upon selection of target cell line and serum dilutions with higher segregation score between groups, the performance of “FIX” and “FIX & PERM” protocols was evaluated. The “FIX” protocol presented excellent performance indices (Se = 92%/Sp = 94%/AUC = 0.96; Se = 96%/Sp = 100%/AUC = 0.99) for the universal (HTLV-1/2 vs. NI) and differential (HTLV-1 vs. HTLV-2) diagnosis of HTLV-1 infection, respectively. Optimization of the “FIX” protocol using the principle of synchronous and asynchronous pairwise analysis further improved the performance of “FC-Duplex IgG1 (HTLV-1/2)”, using the “FIX” protocol for differential diagnosis of HTLV-1 and HTLV-2 infections (Se = 100%/Sp = 100%/AUC = 1.00). In conclusion, the “FC-Duplex IgG1 (HTLV-1/2)” method represents an innovation in the biotechnology segment with the potential to compose a serological kit for differential diagnosis of HTLV-1/2 infection for reference laboratories and blood centers.

Seroprevalence and molecular epidemiology of HTLV-1 isolates from HIV-1 co-infected women in Feira de Santana, Bahia, Brazil

HTLV-1/HIV-1 co-infection is associated with severe clinical manifestations, marked immunodeficiency, and opportunistic pathogenic infections, as well as risk behavior. Salvador, the capital of the State of Bahia, Brazil, has the highest HTLV-1 prevalence (1.74%) found in Brazil. Few studies exist which describe this co-infection found in Salvador and its surrounding areas, much less investigate how these viruses circulate or assess the relationship between them. To describe the epidemiological and molecular features of HTLV in HIV co-infected women. To investigate the prevalence of HTLV/HIV co-infection in surrounding areas, as well as the molecular epidemiology of HTLV, a cross sectional study was carried out involving 107 women infected with HIV-1 from the STD/HIV/AIDS Reference Center located in the neighboring City of Feira de Santana. Patient samples were submitted to ELISA, and HTLV infection was confirmed using Western Blot and Polymerase Chain Reaction (PCR). Phylogenetic analysis using Neighbor-Joining (NJ) and Maximum Likelihood (ML) was performed on HTLV LTR sequences in order to gain further insights about molecular epidemiology and the origins of this virus in Bahia. Four out of five reactive samples were confirmed to be infected with HTLV-1, and one with HTLV-2. The seroprevalence of HTLV among HIV-1 co-infected women was 4.7%. Phylogenetic analysis of the LTR region from four HTLV-1 sequences showed that all isolates were clustered into the main Latin American group within the Transcontinental subgroup of the Cosmopolitan subtype. The HTLV-2 sequence was classified as the HTLV-2c subtype. It was also observed that four HTLV/HIV-1 co-infected women exhibited risk behavior with two having parenteral exposure, while another two were sex workers. This article describes the characteristics of co-infected patients. This co-infection is known to be severe and further studies should be conducted to confirm the suggestion that HTLV-1 is spreading from Salvador to surrounding areas.

Comparative biology of human T-cell lymphotropic virus type 1 (HTLV-1) and HTLV-2

HTLV-1 and HTLV-2 are highly related complex retroviruses that have been studied intensely for nearly three decades because of their association with neoplasia, neuropathology, and/or their capacity to transform primary human T lymphocytes. The study of HTLV also represents an attractive model that has allowed investigators to dissect the mechanism of various cellular processes, several of which may be critical steps in HTLV-mediated pathogenesis. Both HTLV-1 and HTLV-2 can efficiently immortalize and transform T lymphocytes in cell culture and persist in infected individuals or experimental animals. However, the clinical manifestations of these two viruses differ significantly. HTLV-1 is associated with adult T-cell leukemia (ATL) and a variety of immune-mediated disorders including the chronic neurological disease termed HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). In contrast, HTLV-2 is much less pathogenic with reports of only a few cases of variant hairy cell leukemia and neurological disease associated with infection. The limited number of individuals shown to harbor HTLV-2 in association with specific diseases has, to date, precluded convincing epidemiological demonstration of a definitive etiologic role of HTLV-2 in human disease. Therefore, it has become clear that comparative studies designed to elucidate the mechanisms by which HTLV-1 and HTLV-2 determine distinct outcomes are likely to provide fundamental insights into the initiation of multistep leukemogenesis.

Seroprevalence and risk factors for human T cell lymphotropic virus type 1 and 2 infection in human immunodeficiency virus-infected patients attending AIDS referral center health units in Londrina and other communities in Paraná, Brazil

The municipality of Londrina ranks second in the number of AIDS cases in the state of Paraná, Brazil, with the Ministry of Health notified of 1070 cases from 1984 to 2002. The aim of this study was to determine the seroprevalence and risk factors for HTLV-1/2 infection in HIV-infected patients attending the AIDS Reference Center serving Londrina (and surrounding region), Paraná, Brazil. Data concerning sociodemographic conditions and risk factors were collected from 784 HIV-infected patients, using a questionnaire. Blood samples were obtained from 758 of the patients and subjected to serologic screening tests for the determination of HTLV-1/2, as well as hepatitis B virus (HBV), hepatitis C virus (HCV), and syphilis. Most patients were white (mean age, 35.9 years); 55.9% were males and 44.1% were females. The most frequent sexually transmitted disease was gonorrhea (28.5%), followed by syphilis (14.3%) and condyloma (12.2%). The major risk factors associated with the acquisition of retroviruses were sexual contact (84.8%) and intravenous drug use (IDU, 11.9%). The overall infection seroprevalence was 6.4% for HTLV-1/2, 37.2% for HBV, 21.0% for HCV, and 24.4% for syphilis. HTLV-1 and HTLV-2 infections were confirmed in 0.8 and 4.9% of patients, respectively. HIV/HTLV-1/2 coinfection was more frequent in IDUs (59.2% of cases) and was strongly associated with HCV (22.60 [95% CI, 10.35-49.35]). A weak association with HBV (2.09 [95% CI, 1.13-3.90]) and no association with syphilis were observed. The results showed that human retroviruses are circulating in southern Brazil, mainly among white people of both genders of low socioeconomic conditions and educational level. Although the sexual route was considered to be the major risk factor for HIV infection, HTLV-1/2 infection was strongly associated with IDU.

Human retroviruses after 20 years: a perspective from the past and prospects for their future control

Among viruses the human retroviruses may be of special interest to immunologists, because they target cells of the immune system, particularly mature CD4+ T cells, impair their function and cause them to grow abnormally (human T-cell leukemia virus, HTLV) or to die (human immunodeficiency virus, HIV). Human retroviruses cause disease ranging from neurological disorders and leukemias (HTLV-1) to AIDS (acquired immunodeficiency virus) (HIV) and promote development of several types of malignancies (HIV). They share many common features, but their contrasts are greater, especially the far greater replication and variation of HIV associated with its greater genomic complexity. Both have evolved striking redundancy for mechanisms which promote their survival. Thus, HTLV has redundant mechanisms for promoting growth of provirus containing T cells needed for virus continuity, because it is chiefly through its cellular DNA provirus that HTLV replicates and not through production of virions. Conversely, HIV has redundancy in its mechanisms for promoting virion replication and escape from the host immune system. It is via these redundant mechanisms that they produce disease: leukemias from mechanisms promoting T-cell proliferation (HTLV-1) and AIDS from mechanisms promoting virus replication and T-cell death (HIV). The practical challenges for the future are clear. For HTLV-1, education and control of breastfeeding. For HIV, the formidable tasks now ahead in part demand new kinds of talent, talents that will foster greater insights into the development of therapy for the developing countries, new forms of less toxic therapies for all infected persons, a continued and expanded commitment to education, and a persistent 'never say die' commitment to the development of a truly preventive vaccine with all the scientific and nonscientific challenges that these objectives face.

Human retroviruses (HIV and HTLV) in Brazilian Indians: seroepidemiological study and molecular epidemiology of HTLV type 2 isolates

To investigate serological, epidemiological, and molecular aspects of HTLV-1, HTLV-2, and HIV-1 infections in Amerindian populations in Brazil, we tested 683 and 321 sera from Tiriyo and Waiampi Indians, respectively. Both HIV-1 and HTLV-2 infections were detected at low prevalence among the Tiriyos whereas only HTLV-1 was present among the Waiampis, also at low prevalence. Analysis of the nucleotide sequence of the 631 bp of the env gene obtained from the three HTLV-2 isolates detected among the Tiriyos demonstrated by restriction fragment length polymorphism that these viruses belong to subtype IIa. Phylogenetic analysis of this same fragment showed that these sequences cluster closer to HTLV-2 isolates from intravenous drug users living in urban areas of southern Brazil than to the same gene sequence studied in another Brazilian tribe, the Kayapos. Our results confirm the distribution of Brazilian HTLV-2 sequences in a unique cluster I and cluster IIa and suggest that there is a considerable degree of diversity within this cluster. We also report for the first time HIV-1 infection among Brazilian Amerindians.

Risk factors for human T cell lymphotropic virus type I among injecting drug users in northeast Brazil: possibly greater efficiency of male to female transmission

It was observed in the city of Salvador, State of Bahia, the highest seroprevalence of human T cell lymphotropic virus type 1 (HTLV-I) infection in Brazil as demonstrated by national wide blood bank surveys. In this paper, we report results of an investigation of drug use and sexual behavior associated with HTLV-I infection among male and female injecting drug users (IDUs) in Salvador. A cross sectional study was conducted in the Historical District of Salvador from 1994-1996 (Projeto Brasil-Salvador) and 216 asymptomatic IDUs were selected using the snowball contact technique. Blood samples were collected for serological assays. Sera were screened for human immunodeficiency virus (HIV-1/2) and HTLV-I/II antibodies by ELISA and confirmed by Western blot. The overall prevalence of HTLV-I/II was 35.2% (76/216). The seroprevalence of HTLV-I, HTLV-II and HIV-I was for males 22%, 11.3% and 44.1% and for females 46.2%, 10.3% and 74.4% respectively. HTLV-I was identified in 72.4% of HTLV positive IDUs. Variables which were significantly associated with HTLV-I infection among males included needle sharing practices, duration of injecting drug use, HIV-I seropositivity and syphilis. Among women, duration of injecting drug use and syphilis were strongly associated with HTLV-I infection. Multivariate analysis did not change the direction of these associations. Sexual intercourse might play a more important role in HTLV-I infection among women than in men.

HTLV-I in Northeast Brazil: differences for male and female injecting drug users

BACKGROUND

To investigate the seroprevalence of HTLV-I infection among male and female injecting drug users (IDUs).

METHODS

A cross-sectional study conducted in Salvador, Brazil, from 1994 to 1996 (Projeto Brasil-Salvador). The study population of 216 asymptomatic IDUs was selected using snowball contact technique. Data on demographics, sexual behavior, and drug use practices were obtained and blood samples collected for serologic assays. Sera were screened for HIV-1/2 and HTLV-I and HTLV-II antibodies by enzyme-linked immunosorbent assay (ELISA) and confirmed by Western blot.

RESULTS

The overall prevalence of HTLV-I/II was 35.2% (76 of 216). The seroprevalence of HTLV-I, HTLV-II, and HIV-1 was for males 22.0%, 11.3%, and 44.1%, and for females 46.2%, 10.3%, and 74.4%, respectively. Specific seroprevalence of HTLV-I infection demonstrated linear trend with increasing age and increasing duration of drug use. Using univariate analysis, the variables that were significantly associated with HTLV-I infection among males included needle sharing practices, duration of IDU, HIV-1 seropositivity, and positive test result for syphilis. Among women, duration of injecting drug use and positive test result for syphilis were strongly associated with HTLV-I infection.

CONCLUSIONS

Retrovirus infection is highly prevalent among IDUs in Salvador, Brazil and HTLV-I is more common that HTLV-II. Duration of drug use is an important correlate of HTLV-I infection.

The origin and evolution of human T-cell lymphotropic virus types I and II

Studies on human T-cell lymphotropic virus types I (HTLV-I) and II (HTLV-II) are briefly reviewed from the viewpoint of molecular evolution, with special reference to the evolutionary rate and evolutionary relationships among these viruses. In particular, it appears that, in contrast to the low level of variability of HTLV-I among different isolates, individual isolates form quasispecies structures. Elucidating the mechanisms connecting these two phenomena will be one of the future problems in the study of the molecular evolution of HTLV-I and HTLV-II.

Sensitivity of two enzyme-linked immunosorbent assay tests in relation to western blot in detecting human T-cell lymphotropic virus types I and II infection among HIV-1 infected patients from São Paulo, Brazil

We investigated the presence of human T-cell lymphotropic virus types I and II (HTLV-I and HTLV-II) infections, first searching for specific antibodies in 553 serum samples obtained from HIV-1-infected patients from São Paulo, Brazil. Sera were screened using two enzyme-linked immunosorbent assays (ELISAs): the ELISA-EM (ELISA HTLV-I/II, EMBRABIO, BR), which contains HTLV-I and HTLV-II lysates, and the ELISA-DB [ELISA HTLV-I/II, Diagnostic Biotechnology (DB), Singapore], which contains HTLV-I lysate, and HTLV-I and HTLV-II recombinant env proteins (MTA-1 and K55, respectively). Serum samples showing two positive and/or borderline results were confirmed by Western blot (WB 2.3, DB), which discriminates HTLV-I from HTLV-II. WB analyses disclosed 22 cases (4.0%) of HTLV-I and 34 (6.1%) of HTLV-II seroreactivity; 24 sera had indeterminate antibody profile (4.3%) and 2 specimens showed reactivity to both MTA-1 and K55 env proteins. Using stringent WB criteria and analyzing the population according to risk factors, the prevalence rates of HTLV-I and HTLV-II infections were 11.2% and 16.8% in i.v. drug users, 3.4% and 5.5% in heterosexual individuals, and 1.4% and 2.2% in homosexual/bisexual men, respectively. A comparison of ELISA and WB results disclosed that both ELISAs were highly sensitive in detecting HTLV-I antibodies, whereas the ELISA-DB showed 82% sensitivity and the ELISA-EM 100% sensitivity in detecting HTLV-II antibodies. PCR analyses conducted on 37 representative cells samples confirmed the presence of HTLV proviral DNA in the majority of concordant serological cases, except in one, which was HTLV-I infected and seroreacted with K55 protein of HTLV-II. Indeed, after PCR, one case of HTLV-I infection and HTLV-II coinfection, and 30% of WB-seroindeterminate or inconclusive cases infected with HTLV-II could be detected. Our data stress high prevalences of both HTLV-I and HTLV-II infections in HIV-1 coinfected i.v. drug users from São Paulo, and suggests that ELISA kits containing only K55 protein as the HTLV-II-specific antigen, may not have the appropriate sensitivity for the detection of HTLV-II infection in this geographic region, pointing out the need of improved screening tests to be used in Brazil.

Monoclonal antibodies define a cellular antigen involved in HTLV-I infection

The exact mechanism by which the human T cell leukemia viruses (HTLV) infects target cells remains unclear; although some molecules have been identified to be important in viral infection and entry. To investigate these phenomena, we generated a panel of monoclonal antibodies (MAb) against a B cell line (BJAB-WH) which is highly permissive for infection with HTLV. These MAb have been used to further characterize the membrane molecules important for HTLV infection. Three of these MAb designated 4.2.3, 3.3.10, and 11.2.3 were capable of inhibiting syncytium formation induced in human B and T cell lines (i.e., BJAB-WH and SupT-1, respectively) by co-culture with HTLV-I infected MT-2 cells. All of these MAbs immunoprecipitated a 80-85 kDa antigen from the lysates of metabolically labeled BJAB-WH but not from BJAB-CC/84, a noninfectible target cell. The binding of these MAb with different HTLV target cells was analyzed and compared with binding of polyclonal monospecific antisera to the same cell lines. A 80-85 kDa membrane glycoprotein was isolated with an immunoaffinity chromatographic column constructed with MAbs 4.2.3 and 3.3.10. This cellular antigen was capable of inhibiting HTLV I/MT-2 induced fusion. This is the first direct demonstration that a 80-85 kDa cellular glycoprotein is directly involved in HTLV I/II infection and syncytium formation.

The tax gene sequences form two divergent monophyletic lineages corresponding to types I and II of simian and human T-cell leukemia/lymphotropic viruses

Evolutionary associations of human and simian T-cell leukemia/lymphotropic viruses I and II (HTLV-I/II and STLV-I/II) are inferred from phylogenetic analysis of tax gene sequences. Samples studied consisted of a geographically diverse assemblage of viral strains obtained from 10 human subjects and 20 individuals representing 12 species of nonhuman primates. Sequence analyses identified distinct substitutions, which distinguished between viral types I and II, irrespective of host species. Phylogenetic reconstruction of nucleotide sequences strongly supported two major evolutionary groups corresponding to viral types I and II. With the type I lineage, clusters were composed of strains from multiple host species. A genetically diverse, monophyletic lineage consisting of eight new viral strains from several species of Asian macaques was identified. The second lineage consisted of a monophyletic assemblage of HTLV-II/STLV-II strains from Africa and the New World, including an isolate from a pygmy chimp (Pan paniscus) as an early divergence within the lineage. High levels of genetic variation among strains from Asian STLV-I macaque suggest the virus arose in Asia. Evidence of the origin of the type II virus is less clear, but diversity among HTLV-II variants from a single isolated population of Mbati villagers is suggestive but not proof of an African origin.

Molecular phylogeny of human T-cell leukemia virus type I and II of Amerindians in Colombia and Chile

Six human T-cell leukemia virus type I (HTLV-I) and eight human T-cell leukemia virus type II (HTLV-II) cases newly isolated from the South American countries of Colombia and Chile were analyzed together with the two Amerindian HTLV-I isolates previously reported. All of the HTLV-I isolates belonged to the transcontinental subgroup of the "cosmopolitan" group, and Colombian isolates, including those from native Amerindians and Negroes, formed a single tight cluster within this subgroup. The transcontinental subgroup consisted of isolates from various regions such as the Caribbean basin, India, Iran, South Africa, Sakhalin, and Japan, and included isolates from the "Ainu" and "Okinawa" people, regarded as relatively pure Japanese descended from the prehistoric "Jomon" period which began more than 10,000 years ago. This implied a dissemination of the subgroup associated with the movement of human beings in ancient times. On the other hand, all of the HTLV-II isolates from native Amerindians in Colombia and Chile belonged to the HTLV-IIb subtype which has previously been reported to be mainly endemic in certain populations of native Amerindians. The southernmost isolate from Chile, showing wide distribution of the IIb subtype in native South Amerindians and largest heterogeneity of the subtype in Colombian isolates, supported the idea that the HTLV-IIb subtype has been endemic for a long time in native Indians of South America.

Three-dimensional structure of the HTLV-II matrix protein and comparative analysis of matrix proteins from the different classes of pathogenic human retroviruses

The matrix protein performs similar roles in all retroviruses, initially directing membrane localization of the assembling viral particle and subsequently forming a stable structural shell associated with the inner surface of the mature viral membrane. Although conserved structural elements are likely to perform these functions in all retroviral matrix proteins, invariant motifs are not evident at the primary sequence level and three-dimensional structures have been available for only the primate lentiviral matrix proteins. We have therefore used NMR spectroscopy to determine the structure of the matrix protein from human T-cell leukemia virus type II (HTLV-II), a member of the human oncovirus subclass of retroviruses. A total of 577 distance restraints were used to build 20 refined models that superimpose with an rmsd of 0.71 A for the backbone atoms of the structured regions. The globular HTLV-II matrix structure is composed of four alpha-helices and a 3(10) helix. Exposed basic residues near the C terminus of helix II form a putative membrane binding surface which could act in concert with the N-terminal myristoyl group to anchor the protein on the viral membrane surface. Clear structural similarities between the HTLV-II and HIV-1 matrix proteins suggest that the topology and exposed cationic membrane binding surface are likely to be conserved features of retroviral matrix proteins.

Human T lymphotropic virus type II (HTLV-II): epidemiology, molecular properties, and clinical features of infection

Human T lymphotropic virus, type II (HTLV-II), infection has been shown to be endemic in a number of American Indian populations, and high rates of infection have also been documented in intravenous drug abusers in urban areas throughout the world. Although the role of HTLV-II in human disease has yet to be clearly defined, there is accumulating evidence that like HTLV-I, infection may also be associated with rare lymphoproliferative and neurological disorders. In this article we review and summarize the epidemiology, molecular properties and clinical features of HTLV-II infection.

The epidemiology of HTLV-I in Europe

Although human T-lymphotropic virus type I (HTLV-I) infection in Europe is thought to be unusual except amongst people who have immigrated from countries where HTLV-I is endemic, the screening of blood donors has revealed a low seroprevalence across Europe, not only in donors originating from endemic areas but also in the indigenous population. Data from blood donors should not be extrapolated to other groups because blood donors are selected to be at low risk of parenterally transmissible infections. Unfortunately only small studies have been conducted in other population groups, including women attending antenatal clinics, despite the importance of breast-feeding in vertical transmission. Data from metropolitan areas of the United Kingdom and France suggest that the seroprevalence of HTLV-I in pregnant women is up to 100 times higher than in blood donors. HTLV-I infection is also more common in patients attending sexually transmitted disease clinics, whilst HTLV-II is endemic in many cities amongst intravenous drug users. There are few incidence data for diseases associated with HTLV-I, even though cases of adult T-cell leukemia/lymphoma and HTLV-I-associated myelopathy have been described in many European countries. Data on the seroprevalence of HTLV-I in central and eastern Europe are scanty but the few published studies suggest a higher rate than has been documented in western Europe.

Nucleotide sequence and restriction fragment length polymorphism analysis of the long terminal repeat of human T cell leukemia virus type II

Molecular studies have demonstrated the existence of two major subtypes of human T cell leukemia virus type II: HTLV-IIa and HTLV-IIb. In attempts to further classify this family of viruses we have carried out nucleotide sequence and restriction fragment length polymorphism (RFLP) analysis of the long terminal repeat (LTR), a region that has been shown in previous studies to have the greatest intra- and intersubtype genomic divergence. Analysis of the nucleotide sequences suggested the existence of distinct phylogenetic groups in each subtype and, on the basis of predicted differences in restriction endonuclease sites, RFLP analysis allowed the identification of four groups within the IIa subtype (a1-a4) and six within the IIb subtype (b1-b6). Nucleotide sequence analysis also suggested the possible existence of HTLV-II quasispecies. However, this appeared not to be significant, and preliminary studies suggest that these would not be expected to influence the results of RFLP analysis appreciably. The validity of the RFLP method was demonstrated in an analysis of 36 randomly chosen samples from HTLV-II seropositive blood donors from the New York City Blood Center, where it could be shown that all could be successfully classified. Moreover, the RFLP analysis correctly matched the viruses in donors and recipients of contaminated blood in four situations in which HTLV-II was inadvertently transmitted by transfusion. RFLP analysis of the LTR appears to be a rapid and reliable method by which to identify HTLV-II infection. This should prove useful in studies of the epidemiology and the characterization of viruses present both in nonindigenous and indigenous populations.

Genotypic characteristics of HTLV-II isolates from Amerindian and non-Indian populations

The Amerindian human T-cell lymphotropic virus type II isolate HTLV-IIG12 has been demonstrated to be an HTLV-IIb with several unique features, including several restriction enzyme site changes, a distinctive pre-gag region, a stop codon within the pol gene, and an extended Tax protein. In this study, HTLV-II isolates from Amerindian and non-Indian populations were characterized by restriction enzyme site analysis to determine the prevalent HTLV-II subtype. In addition, DNA amplification by the polymerase chain reaction and Southern blot analyses were used to probe for the HTLV-IIG12 pre-gag region. Our results showed that of 13 Guaymi Indian isolates subtyped, all were HTLV-IIb, and that approximately one third of 17 isolates had the unique pre-gag region. While other HTLV-II-infected groups contained both HTLV-IIa and HTLV-IIb isolates, none of these isolates showed evidence of the distinctive HTLV-IIG12 pre-gag region. Lastly, DNA sequence analysis was used to determine the prevalence of the stop codon within the pol gene open reading frame. These analyses revealed that the occurrence of a stop codon within this sequence appeared to be characteristic of most HTLV-IIb subtypes. These results further our understanding of the genetic variations and evolution of the HTLV-II viruses within the endemically infected Amerindian populations, as well as U.S. intravenous drug users and other non-Indian populations.

Phylogenetic relationship and geographic distribution of multiple human T-cell lymphotropic virus type II subtypes

The current env-based subtyping of human T-cell lymphotropic virus type II (HTLV-II) identifies only two heterogenetic groups, HTLV-IIa and HTLV-IIb. To better understand the genetic diversity and phylogeny of HTLV-II, we examined the most divergent genomic region of HTLV-II, the long terminal repeat, by using restriction fragment length polymorphism (RFLP) and sequence analysis. Long terminal repeat sequences were amplified from peripheral blood mononuclear cells by PCR and digested with seven restriction endonucleases that differentiated HTLV-II into five HTLV-IIa (IIa0 to IIa4) and six HTLV-IIb (IIb0 to IIb5) restriction types, with HTLV-IIa0 and HTLV-IIb0 being prototypes for the MoT and NRA isolates, respectively. We examined 169 HTLV-II-infected samples, including 123 from blood donors and intravenous drug users (IDU) from the Americas, 16 from IDU from Europe, and 30 from Amerindians. Of the 169 samples, 109 (64.5%) were categorized as HTLV-IIa and 60 (35.5%) were categorized as HTLV-IIb. The predominant restriction types seen among the U.S. blood donors and U.S. IDU were IIa0 (68.7%) and IIb4 (10.4%). Four Spanish and seven Italian samples were IIb4, while five Norwegian samples were IIa2. Twelve Guaymi and all ten Seminole samples were single restriction types (IIb1 and IIb5, respectively), whereas the two Navajo and six Pueblo samples had a mixture of restriction types IIa0, IIa4, and IIb5. Of the HTLV-IIb restriction types observed in the U.S. non-Indians, 42.8% appear to have originated from the North Amerindian (IIb5), while 57.2% were similar to the European IIb4 restriction type. Sequences of 15 selected HTLV-II samples were determined and phylogenetically compared with 7 previously published HTLV-II LTR sequences. The derived topologies revealed three HTLV-IIa phylogroups (A-I to A-III) and four HTLV-IIb phylogroups (B-I to B-IV). Furthermore, the HTLV-IIa phylogroups appear to have evolved from the HTLV-IIb phylogroups. In the HTLV-IIa cluster, a Navajo (A-I) and a Brazilian (A-II) sequence formed separate phylogroups, while the remaining IIa sequences formed a single phylogroup (A-III). The four HTLV-IIb phylogroups were represented predominantly by a New York IDU (B-I), European IDU (B-II), North Amerindian and NRA (B-III), and Central Guaymi Indian (B-IV) sequence(s). Comparison of the phylogenetic data with the RFLP results revealed that results of the two methods correlated completely, demonstrating the ability of the RFLP method to predict the phylogroup of HTLV-II-infected samples accurately and quickly. GENBANK/U10258

HTLV-I and HTLV-II infections among HIV-1 seropositive patients in Sao Paulo, Brazil

To estimate the presence of, and the risk factors for HTLV-I and HTLV-II infections among HIV-1 infected subjects in Sao Paulo, Brazil, a serosurvey was performed in 471 HIV-1 infected patients, including 216 intravenous drug addicts (IVDA), 229 homosexual/bisexual men, and 26 with other risk factors. Serum samples were screened for HTLV seroreactivity by ELISA; reactive samples were analyzed by Western Blot (WB), using whole HTLV-I lysate as antigen. To confirm and discriminate HTLV-I and HTLV-II infections, sera presenting any bands on WB were further analyzed by a WB containing recombinant HTLV-I and HTLV-II proteins (WB 2.3), and by enzyme immunoassays using synthetic peptides specific for envelope proteins (Synth-EIA). In 22 cases, cell samples were available for polymerase chain reaction (PCR) studies. On WB, 114 sera were reactive and, of these, 37 and 25 were concordantly positive on both WB 2.3 and Synth-EIA procedures for HTLV-I and HTLV-II specific antibodies, respectively; 37 specimens were negative on both assays, and 15 gave discordant or indeterminate results. PCR findings confirmed concordant results obtained in the discriminatory serological assays. The prevalence rates of HTLV-I and HTLV-II infections were 15.3% and 11.1% in IVDA, and 0.9% and 0.4% in homosexual/bisexual men, respectively. No case of HTLV-I/HTLV-II co-infection was found.

Seroepidemiology of human T-lymphotropic virus type I infection among intravenous drug abusers in Taiwan

In order to assess seroprevalence of human T-lymphotropic virus type I (HTLV-I) infection among intravenous drug abusers in Taiwan, serum samples were collected from 858 male study subjects. Antibodies against HTLV-I (anti-HTLV-I) in sera were tested by enzyme-linked immunosorbent assay and confirmed by Western blotting. The overall prevalence of anti-HTLV-I (2.3%) in drug abusers was significantly higher than that in the general population in Taiwan with a relative risk of 4.9, but it was only slightly higher than that in prostitutes (1.9%). There was a statistically significant increase in prevalence with age. Drug abusers engaged in prostitution had a significantly higher prevalence (18.2%) than those who were not (2.1%). No significant association with anti-HTLV-I positivity was observed with marital status and educational level. Tatooed abusers had an increased prevalence (2.7%) compared with the untattooed (1.4%). Drug abusers tattooed before 1980 had a significantly higher prevalence (3.5%) than those tattooed after 1980 (0.8%). Anti-HTLV-I prevalence was higher for those who had been blood transfused (4.5%) than untransfused abusers (2.0%).

Identification of an 80-kilodalton membrane glycoprotein important for human T-cell leukemia virus type I and type II syncytium formation and infection

Human T-cell leukemia virus type I and type II (HTLV-I and HTLV-II, respectively) infect certain sublines of the BJAB human B-cell line. We observed that the WH subline, but not the CC/84 subline, of BJAB cells were infectible by cell-free HTLV-I or HTLV-II and formed syncytia with cells infected by these retroviruses. This suggests that the BJAB-CC/84 cells possibly lack a membrane molecule(s) important for syncytium formation and infectibility. In order to identify this antigen, we generated polyclonal anti-BJAB-WH antisera which were adsorbed on BJAB-CC/84 cells. The adsorbed antisera bound only BJAB-WH and BJAB-CC/79 cells as demonstrated by complement-dependent cytotoxicity and flow cytometric assays. Furthermore, this adsorbed antisera bound several human T-cell clones, including SupT-1, as determined by flow cytometric assays. The adsorbed antiserum was monospecific as it immunoprecipitated only one 78- to 80-kDa protein from lysates of metabolically labeled BJAB-WH, BJAB-CC/79, and SupT-1, but not BJAB-CC/84, cells. The monospecific antisera detected a glycoprotein composed of a 64- to 66-kDa core protein containing tunicamycin-sensitive N-linked oligosaccharides. This membrane glycoprotein appears to be involved in HTLV-I- and HTLV-II-induced fusion and infection, as the monospecific antisera were capable of inhibiting both of these processes. The monospecific antisera diluted 1:50 and 1:90 inhibited 85 to 90% of syncytium formation induced in BJAB-WH, BJAB-CC/79, and SupT-1 cells cultured with HTLV-I- or HTLV-II-infected MT2, MoT, or FLW human T- or B-cell lines. At the same dilution, antisera inhibited 70 to 80% of infection of BJAB-WH cells by cell-free HTLV-I or HTLV-II. Thus, these studies indicate a role for a 78- to 80-kDa glycoprotein in HTLV-I or HTLV-II infection and syncytium formation.

Molecular cloning, expression, and biological characterization of an HTLV-II envelope glycoprotein: HIV-1 expression is permissive for HTLV-II-induced cell fusion

The human T cell leukemia virus II (HTLV-II) is a type C retrovirus closely related to the human transforming retrovirus HTLV-I. In contrast to HTLV-I, the role of HTLV-II in human disease is controversial. However, HTLV-II infection has been documented in several cases of a clinically benign hairy cell leukemia and has also been suggested as a cofactor for HIV-1 disease progression. We report that an HTLV-II isolate (designated FLW) derived from a serum-positive white male can induce cell fusion and significant cytopathic effects in tissue culture. This HTLV-II isolate induced syncytium formation with human T and B cell lines, several human fibroblast cell lines, and, interestingly, HIV-1- and HIV-2-infected cell lines. To elucidate the role in the FLW envelope in this phenomenon, we have cloned the envelope glycoproteins gp46 and gp21 of this isolate. The envelope glycoproteins expressed in the absence of the rest of the viral genome were sufficient to drive syncytium formation in vitro, and preserved the cellular tropism for syncytium formation observed with the native retroviral isolate. Amino acid (aa) sequence analysis demonstrated 88% overall similarity with other HTLV-II envelope glycoproteins. Interestingly, only cells infected by HIV-I, but not parental H9 cells, form syncytia with FLW env-transfected cells as well as with HTLV-II/FLW-infected BJAB-WH cells. Furthermore, antibodies directed at the CD4 receptor failed to inhibit the induction of giant cell formation, implying that the FLW envelope protein was responsible for driving syncytium formation in this system. These observations may be important for the understanding of the processes involved in human retroviral-mediated syncytium formation and may suggest a mechanism whereby HTLV-II could influence the disease process in individuals dually infected with HIV-1 and HTLV-II.

HTLV-II seroprevalence in pygmies across Africa since 1970

HTLV-II-specific antibodies, with patterns similar to those in the Americas, were present in sera collected about 1970 from Bambuti pygmies in Zaire (14/102; 14%) and from pygmies in Cameroon (5/214; 2.3%), and were more prevalent than HTLV-I. In the Central African Republic, 504 pygmies were HTLV negative. After finding of 4 HTLV-II seropositives among 12 Bambuti pygmies sampled in 1991, this established that HTLV-II or a related retrovirus is present as an ancient endemic in some, but not all, insulated groups of African pygmies, similar to the HTLV-II distribution in Amerindian populations. The endemic among the oldest inhabitants of central Africa, and the occasional and scattered occurrence of apparent HTLV-II among predominant HTLV-I in other Africans, fit well with an ancient African virus and not with importation from the New World. Theories on the origin and evolution of the primate T-lymphotropic viruses (PTLVs) should take into account the longstanding presence of HTLV-II-type viruses in both the Old and New World. Present serology suggests identity of the African viruses with HTLV-II, but their assignment to a new HTLV type is open should genetic analysis show strong divergence from American HTLV-II. Clinical expression, if any, remains to be studied.

Nucleotide sequence analysis of human T cell leukemia virus, type II (HTLV-II) isolates

A study by Hall et al. (J Virol 1992;66:2456-2463; Ref. 11) has suggested the existence of two closely related molecular subtypes of HTLV-II, which were tentatively designated HTLV-IIa and HTLV-IIb. To confirm this nucleotide sequence analysis of 986 bp of the env gene region encoding the entire surface glycoprotein, gp46, and the amino terminus of the transmembrane glycoprotein, gp21, of 10 HTLV-II isolates was carried out. The results clearly established the existence of two subtypes and demonstrated a 4.3% divergence in sequence in this region. Analysis of other gene regions of the provirus, including the pol (1544 bp), gag (448 bp), and the entire LTR (743 bp) of two representative isolates of each subtype, showed a sequence divergence of 3.8 to 5.7%, with greatest divergence occurring in the LTR. In addition to single nucleotide changes, the gag regions encoding the structural protein, p19, of the HTLV-IIb isolates were also found to have a 66-bp deletion that would be expected to result in a p19 protein having a 22-amino acid deletion in the carboxy-terminus region. Attempts to exploit this to differentiate the two subtypes serologically were unsuccessful in that recombinant p19 proteins of both subtypes were found to be antigenically cross-reactive. The finding of two molecular subtypes of HTLV-II may have important implications for a better understanding of the biological and pathogenic properties of the virus, and will be useful in characterizing the viruses present in endemic foci in American Indian populations.

Differential diagnosis of HTLV-I and HTLV-II infections by restriction enzyme analysis of 'nested' PCR products

A 'nested' polymerase chain reaction (PCR) assay is described which is capable of detecting single copies of human T-cell lymphotropic virus (HTLV) in genomic DNA extracted from peripheral blood mononuclear cells (PBMCs). A single set of 'nested' oligonucleotide primers, based on the highly conserved tax/rex region of the viral genome, was able to detect both HTLV-I and HTLV-II proviral sequences in clinical samples of diverse geographical origins, from the United States, Great Britain, Japan, the Caribbean, Italy, Greece, Iraq and West Africa. Rapid discrimination between HTLV-I and HTLV-II infections was achieved by restriction enzyme analysis of unpurified second-round PCR products, even in those cases in which serological assays had failed to provide a definitive result. Over a 2-year period, a total of 53 HTLV infections (37 HTLV-I and 16 HTLV-II) were identified by this technique and complete concordance with serological typing, available in 41 cases, was observed.

Prevalence of HTLV-I antibody among two distinct ethnic groups inhabiting the Amazon region of Brazil

HTLV-I seroprevalences of 3.63% (02/55), 12.19% (10/82) and 13.88% (10/72) were demonstrated among Tiryio, Mekranoiti and Xicrin Amazonian Indians, respectively, by the Western blotting enzyme assay (WBEI). By indirect immunoelectron microscopy (IIEM), 2 Tiriyo, 9 Mekranoiti and 6 Xicrin Amerindians were reactive. Of 44 serum samples from Japanese immigrants, none reacted by any of the techniques before mentioned. One, 8 and 6 serum samples from Tiryio, Mekranoiti and Xicrin Indians, respectively, were both WBEI and IIEM positive. Our results strongly suggest that HTLV-I and/or an HTLV-I antigenic variant circulate (s) among populations living in the Amazon region of Brazil.

Multiple isolates and characteristics of human T-cell leukemia virus type II

Human T-cell leukemia (or lymphotropic) virus type II (HTLV-II) was isolated from eight HTLV-seropositive patients, six of whom were also infected with human immunodeficiency virus, by cocultivation of peripheral blood mononuclear cells (PBMCs) with BJAB, a continuous B-cell line. Restriction endonuclease mapping of the proviruses demonstrated consistent differences among isolates, and two distinct physical map patterns were observed. The results suggest the existence of two closely related molecular subtypes of HTLV-II, which are tentatively designated HTLV-IIa and HTLV-IIb. This finding was supported by preliminary nucleotide sequence analysis of the env gene region encoding the transmembrane glycoprotein gp21, which showed consistent differences between the two proposed virus subtypes. Exploitation of differences in restriction endonuclease sites allowed polymerase chain reaction amplification to detect and differentiate the two subtypes in fresh PBMCs of HTLV-seropositive intravenous drug abusers (IVDAs). The results of these studies confirm that HTLV-II infection is the prominent HTLV infection in seropositive IVDAs and also show that infection with both subtypes occurs. The finding of genetic heterogeneity in the HTLV-II group of viruses may have important implications for studies on its role in human disease and will be useful in characterizing the viruses present in newly discovered endemic foci in New World indigenous populations.

Sequence variation of functional HTLV-II tax alleles among isolates from an endemic population: lack of evidence for oncogenic determinant in tax

Human T-cell leukemia-lymphoma virus type II (HTLV-II) has been isolated from patients with hairy cell leukemia (HCL). We previously described a population with longstanding endemic HTLV-II infection, and showed that there is no increased risk for HCL in the affected groups. We thus have direct evidence that the endemic form(s) of HTLV-II cause HCL infrequently, if at all. By comparison, there is reason to suspect that the viruses isolated from patients with HCL had an etiologic role in the disease in those patients. One way to reconcile these conflicting observations is to consider that isolates of HTLV-II might differ in oncogenic potential. To determine whether the structure of the putative oncogenic determinant of HTLV-II, tax2, might differ in the new isolates compared to the tax of the prototype HCL isolate, MO, four new functional tax cDNAs were cloned from new isolates. Sequence analysis showed only minor (0.9-2.0%) amino acid variation compared to the published sequence of MO tax2. Some codons were consistently different from published sequences of the MO virus, but in most cases, such variations were also found in each of two tax2 clones we isolated from the MO T-cell line. These variations rendered the new clones more similar to the tax1 of the pathogenic virus HTLV-I. Thus we find no evidence that pathologic determinants of HTLV-II can be assigned to the tax gene.

Human T-cell leukemia virus type II Rex binding and activity require an intact splice donor site and a specific RNA secondary structure

The human T-cell leukemia virus type II (HTLV-II) regulatory protein Rex augments cytoplasmic levels of unspliced gag-pol mRNA by acting through a Rex-responsive element (RxRE) in the long terminal repeat. Purified Rex protein binds to long terminal repeat mRNA. Here, using an immunobinding assay to measure the binding of Rex protein to mutated RxRE RNAs, we show that efficient Rex binding requires a stem-bulge-loop RNA secondary structure (nucleotides [nt] 465 to 500) and specific sequences both within the stem-bulge (nt 470 to 476) and within a conserved upstream splice donor site (nt 449 to 455). Rex function in a transient transfection expression system correlates with Rex protein-RxRE RNA binding. The ability of HTLV-II Rex to interact directly with the HTLV-II splice donor site suggests that HTLV-II Rex may increase expression of unspliced gag-pol mRNA, in part, by inhibiting splicing.

HTLV-1 envelope sequences from Brazil, the Caribbean, and Romania: clustering of sequences according to geographic origin and variability in an antibody epitope

We sequenced the envelope genes of Human T-cell leukemia type I viruses (HTLV-I) derived from five Brazilian, two Caribbean, and one Romanian case of adult T-cell leukemia after amplification of the complete env gene by PCR. A comparison with previously reported HTLV-I sequences revealed that, although highly homologous, no two env sequences were identical. All envelope sequences differed from each other by 0.3-2.1% nucleotide differences. The five Brazilian sequences clustered together and were about as different from each other (0.5-0.75% nucleotide difference) as were three previously reported Japanese sequences (0.7-0.95%). In contrast, sequences of Caribbean origin were less homogeneous (0.5-1.9% nucleotide differences within this group). The Romanian sequence was not significantly more divergent than any of the others and was closest to our two Caribbean sequences. We observed two changes in a region (aa 176-209) which has previously been shown to contain a linear antibody epitope recognized by most human sera from seropositive individuals. One of these changes affects the binding of monoclonal antibodies to this epitope demonstrating the variability of an antibody epitope in the HTLV-I envelope.

Serological discrimination between HTLV-I and HTLV-II antibodies by ELISA using synthetic peptides as antigens

Using the peptides from amino acids 100-130 of the HTLV-I gag protein, 175-199 of the HTLV-I env protein and the corresponding peptides of HTLV-II (amino acids 106 to 135 of the gag protein and 171 to 196 of the env protein), we tested for reactivity against antibodies by enzyme immunoassay in sera from HTLV-I and HTLV-II carriers. The peptides derived from the env proteins have high specificity for antibody binding. The peptide based on amino acids 175-199 of HTLV-I reacted with antibodies in sera from all HTLV-I carriers, and the peptide composed of amino acids 171-196 of HTLV-II reacted with antibodies in sera from all HTLV-II carriers. For the peptides derived from the gag proteins, we observed some cross-reactivity in sera from persons with anti-HTLV-I and anti-HTLV-II, due to antibody binding to the peptide corresponding to 12 amino acids from the C-terminal end of the gag protein. Separate enzyme immunoassays that used the four synthetic peptides as antigens clearly distinguished between serum with antibodies to HTLV-I or HTLV-II in various individuals and excluded false positive results using the particle agglutination assay that used a whole-virus lysate of HTLV-I as antigen.

Syndrome of severe skin disease, eosinophilia, and dermatopathic lymphadenopathy in patients with HTLV-II complicating human immunodeficiency virus infection

Two intravenous drug users dually infected with human immunodeficiency virus type 1 (HIV-1) and human T-cell leukemia virus type II (HTLV-II) developed an unusual severe dermatitis characterized by progressive brawny induration, fissuring, and ulceration of the skin, with an associated CD8 cell infiltration in one patient. Both patients had persistent eosinophilia. Lymph node biopsy revealed dermatopathic lymphadenopathy, an unusual pathologic finding in HIV-1 infection but one seen in association with mycosis fungoides and other skin disorders. Two new isolates of HTLV-II virus were established from these patients and were identified as HTLV-II by Southern blotting. This type of skin disease and lymph node pathology has not been found in other intravenous drug users who have been infected with HIV-1 alone or in patients in other risk groups for HIV-1 infection. HTLV-II may play a role in this unique new disease pattern in patients infected with HIV-1.

Identification of type-specific linear epitopes in the glycoproteins gp46 and gp21 of human T-cell leukemia viruses type I and type II using synthetic peptides

Synthetic peptides of 20-25 amino acids were employed in enzyme-linked immunosorbent assays to identify linear epitopes in the external glycoprotein gp46 and the transmembrane glycoprotein gp21 of human T-cell leukemia/lymphotropic viruses type I (HTLV-I) and II (HTLV-II). Ten linear epitopes were identified in the HTLV-I glycoproteins, seven in gp46 and three in gp21. Three major linear epitopes were identified in the gp46 of HTLV-II. Peptides representing linear epitopes of gp46 were found to be sensitive and specific for the detection of antibody and permit serological identification and differentiation of HTLV-I and HTLV-II infections.

Serological and molecular evidence of infection by human T-cell lymphotropic virus type II in Italian drug addicts by use of synthetic peptides and polymerase chain reaction

Infection with human T lymphotropic virus type I (HTLV-I) is associated with specific forms of tumours and neurological disorders, but the pathogenic activity of HTLV-II is not yet established. Moreover, due to high crossreactivity between the two viruses, differential diagnosis is not readily achieved. To discriminate between HTLV-I and HTLV-II infections, we employed synthetic peptides specific for HTLV-I and HTLV-II env regions, and the polymerase chain reaction (PCR). In a series of 962 intravenous drug addicts (IVDAs) and 50 patients with haematological malignancies, 51 and 2 samples, respectively, were reactive against HTLV-I proteins; among these, HTLV-I infection was confirmed only in 1 patient with adult T-cell lymphoma, while HTLV-II infections were identified in 6 out of 14 PCR-tested IVDAs. These findings provide evidence of HTLV-II infection among Italian IVDAs. The differentiation between HTLV-I and HTLV-II infections may contribute to a better understanding of HTLV-II pathogenicity in man.

Relative prevalence and risk factors of HTLV-I and HTLV-II infection in US blood donors

The clinical significance of human T-cell lymphotropic virus type II (HTLV-II) infection, unlike that of HTLV-I, is unknown, and the major known association of HTLV-II seropositivity is with intravenous drug abuse. Screening of blood donors for HTLV-I, now routine in North America, does not distinguish this retrovirus from HTLV-II. To find out more about the seroepidemiology of and risk factors for HTLV I and II, blood from 480,000 volunteer donors in five geographically separate US urban centres was tested for antibodies to HTLV-I/II and HIV-1. Confirmed HTLV-I/II seropositive donors were then followed up by DNA amplification to distinguish type I from type II and by interviews focusing on possible risk factors. HTLV seroprevalence was 3.3 times greater than that for HIV-1 (0.043% vs 0.013%). DNA amplification on 65 of the 207 HTLV-I/II seropositive donors revealed that 34 (52%) had HTLV-II infection and 28 (43% had HTLV-I; 3 samples were uninformative. Interviews of 49 donors showed that whereas HTLV-I was principally associated with donor origin from endemic regions, the major risk factor for HTLV-II infection was intravenous drug use. The surprisingly high rate of HTLV-II infection in US blood donors raises important public health and donor counselling issues since HTLV-I infection is associated with adult T-cell leukaemia and a neurological disorder while the pathogenicity of HTLV-II is as yet unclear.

Low prevalence of human T-cell leukaemia virus-I and -II infection among drug users in Amsterdam, The Netherlands

The prevalence of human T-cell leukaemia virus-I and -II infection was studied in a cohort of 346 intravenous and nonintravenous drug users in Amsterdam. Three participants (0.86%) had antibodies to HTLV-I by two commercially available HTLV-I enzyme immunoassays (EIA). Infection in these three subjects was confirmed by radioimmunoprecipitation assay. In the immunoblot study, only two of the three subjects were considered positive, since the serum of the third subject had antibodies to p24 only. By means of the polymerase chain reaction two participants (male intravenous drug users infected with human immunodeficiency virus; HIV) appeared to be infected with HTLV-I and one subject (a male nonintravenous drug user from Surinam) with HTLV-II. It is concluded that HTLV-I and HTLV-II circulate sporadically among drug users in Amsterdam and that risky injecting behaviour, which led to an HIV epidemic among intravenous drug users, has not led so far to an appreciable transmission of the other retroviruses among this group.

Human T-cell leukemia virus (HTLV) type II Rex protein binds specifically to RNA sequences of the HTLV long terminal repeat but poorly to the human immunodeficiency virus type 1 Rev-responsive element

The human T-cell leukemia viruses (HTLVs) encode a trans-regulatory protein, Rex, which differentially regulates viral gene expression by controlling the cytoplasmic accumulation of viral mRNAs. Because of insufficient amounts of purified protein, biochemical characterization of Rex activity has not previously been performed. Here, utilizing the baculovirus expression system, we purified HTLV type II (HTLV-II) Rex from the cytoplasmic fraction of recombinant baculovirus-infected insect cells by heparin-agarose chromatography. We directly demonstrated that Rex specifically bound HTLV-II 5' long terminal repeat RNA in both gel mobility shift and immunobinding assays. Sequences sufficient for Rex binding were localized to the R-U5 region of the HTLV-II 5' long terminal repeat and correlate with the region required for Rex function. The human immunodeficiency virus type 1 (HIV-1), has an analogous regulatory protein, Rev, which directly binds to and mediates its action through the Rev-responsive element located within the HIV-1 env gene. We demonstrated that HTLV-II Rex rescued an HIV-1JR-CSF Rev-deficient mutant, although inefficiently. This result is consistent with a weak binding activity to the HIV-1 Rev-responsive element under conditions in which it efficiently bound the HTLV-II long terminal repeat RNA.

Rex transregulation of human T-cell leukemia virus type II gene expression

The Rex protein of the human T-cell leukemia virus type II (HTLV-II), Rex-II, plays a central role in regulating the expression of the structural genes of this retrovirus. Rex-II acts posttranscriptionally by inducing the cytoplasmic expression of the incompletely spliced viral mRNAs that encode the Gag and Env structural proteins and the enzymes derived from the pol gene. We now define a 295-nucleotide cis-acting regulatory element within the 3' long terminal repeat of HTLV-II that is required for the effects of Rex-II. This Rex-II response element (RexIIRE) corresponds to a predicted, highly stable RNA secondary structure and functions when present in the sense but not in the antisense orientation. The RexIIRE confers responsiveness not only to Rex-II but also to the Rex protein of HTLV-I. Deletion and substitution mutagenesis of the RexIIRE permitted identification of a small subregion within the larger element critically required for Rex-II responsiveness and further suggested that the structurally distinct RexIIREs generated from the 5' and 3' long terminal repeats of HTLV-II may differentially regulate the cytoplasmic expression of unspliced gag-pol and singly spliced env mRNAs. While the Rev protein of human immunodeficiency virus type 1 fails to function via the RexIIRE, the Rex-II protein, like Rex-I, can functionally replace the Rev protein of human immunodeficiency virus type 1 via its interaction with the Rev response element (RevRE).

The internal methionine codons of human T-cell leukemia virus type II rex gene are not required for p24rex production or virus replication and transformation

Human T-cell leukemia virus types I (HTLV-I) and II (HTLV-II) have two nonstructural trans-acting regulatory genes, tax and rex, located in the 3' region of the viral genome. The tax gene product (HTLV-I p40tax and HTLV-II p37tax) is the transcriptional activator of the viral long terminal repeat. The rex gene encodes two protein products, p27rex/p21rex and p26rex/p24rex in HTLV-I and HTLV-II, respectively. Rex acts posttranscriptionally to facilitate accumulation of full-length gag/pol and singly spliced env mRNA in the cytoplasm of HTLV-infected cells. Previous studies showed that the first ATG of the rex gene is critical for Rex production and function. The importance of the internal ATGs to Rex function is not known. However, in vitro mutagenesis of the HTLV-I rex gene has provided indirect evidence which suggests that p21rex, and by analogy HTLV-II p24rex, results from initiation at an internal AUG of the tax/rex mRNA. By using an infectious molecular clone of HTLV-II, we investigated the importance of the internal ATGs of the rex gene on Rex protein production and function. Our results indicate that p24rex of HTLV-II is not initiated at an internal AUG and that the internal methionine codons are not crucial to the function of the rex gene and, ultimately, the transforming properties of the virus.

Receptor interference groups of 20 retroviruses plating on human cells

The types of receptors on the surfaces of human and other mammalian cells for 13 C-type and 7 D-type retrovirus strains were determined by interference to the formation of syncytia and the plating of viral pseudotypes. All the D-type simian retroviruses (SRV-1-5, SMRV, PO-1-Lu) share a common receptor which is also utilized by the baboon and cat endogenous C-type viruses (BaEV, RD114). Syncytial cross-interference was also observed in human cells between the gibbon ape leukemia/simian sarcoma associated viruses (GALV/SSAV) and feline leukemia virus subgroup B (FeLV-B). Amphotropic and xenotropic murine leukemia viruses (MLV-A, MLV-X), bovine leukemia virus (BLV), and FeLV-C infect human cells via unique cell surface receptors. Human T-cell leukemia viruses types 1 and 2 (HTLV-1, HTLV-2) share a common receptor with related chimpanzee and simian viruses (STLV). Thus seven distinct receptor groups were delineated on human cells for C-type and D-type retroviruses.

Screening for prolonged incubation of HTLV-I infection in British and Jamaican relatives of British patients with tropical spastic paraparesis

OBJECTIVE

To compare the prevalence of antibody to and proviral DNA of the retrovirus HTLV-I in relatives of 11 British patients with tropical spastic paraparesis who had migrated from Jamaica before they developed symptoms, and to examine factors possibly related to transmission of HTLV-I.

DESIGN

Migrant, family study. Antibody state was determined by several methods and confirmed by western blotting; the polymerase chain reaction was used to detect proviral DNA.

SETTING

Britain and Jamaica.

SUBJECTS

All available first degree relatives: those born and still resident in Jamaica (group 1); those born in Jamaica who migrated to Britain (group 2); and index patients' children who were born and resident in Britain (group 3). All had been breast fed and none had had blood transfusions.

RESULTS

Of the 66 living relatives, 60 were traced. Seroprevalence among those born in Jamaica (irrespective of current residence) was 22% (10/46; 95% confidence limits 9 to 34%) compared with zero among British born offspring (0/14) and was higher in group 2 at 33% (7/21; 12 to 55%) than in group 1 at 12% (3/25; 0 to 25%). (Patients in group 1 had the greatest mean age.) Proviral DNA was not detected in any subject negative for HTLV-I antibody, making prolonged viral incubation in those negative for the antibody unlikely.

CONCLUSION

In this sample factors related to place of birth and early residence were more important in transmission of HTLV-I than maternal or age effects. In areas with a low to moderate prevalence policies of preventing mothers who are carriers of the virus from breast feeding would be premature.

HTLV-1 and tropical spastic paraparesis. 2. The human T-cell lymphotropic virus type 1

Human T-lymphotropic viruses (HTLV) are causally associated with adult T-cell leukaemia and with a progressive form of lower limb paralysis known as tropical spastic paraparesis. HTLV-1 is endemic in parts of Japan, the Caribbean, West Africa and probably South America, and is associated with disease in these areas. Horizontal transmission is probably most common through sexual intercourse which, it is postulated, must be more efficient from male to female because virus carriage is more prevalent in women in endemic areas. Vertical transmission appears to be principally through breast milk. Poor housing and hygiene may facilitate transmission.

Concomitant infection of HTLV-I and HIV-1: prevalence of IgG and IgM antibodies in Washington, D.C. area

Serum samples collected from four groups of individuals in the Washington, D.C. area were examined for the presence of IgG and IgM classes of antibody reacting against HTLV-I and HIV-1. These four groups were: (1) healthy adults with negative premarital VDRL test for syphilis (n = 113), (2) miscellaneous common disease patients (n = 155), (3) drug abusers (n = 130), and (4) homosexual men (n = 187). The former two groups are considered to be low-risk groups, and the latter two, high-risk groups. The prevalence of IgG antibody on ELISA/Western blot tests for these groups were respectively: (1) 5.3%/1.8%, (2) 5.2%/1.9%, (3) 13.9%/4.6%, and (4) 4.3%/1.6% for HTLV-I, and (1) 2.7%/0.9%, (2) 4.5%/0%, (3) 12.3%/5.4%, and (4) 8.0%/5.9% for HIV-1. Instances of possible concomitant infection as shown by the presence of antibodies against both HTLV-I and HIV-1 were found only in the latter two high-risk groups, i.e. two (1.5%) in group (3), and three (1.6%) in group (4) as confirmed by both Western blot and immunofluorescence tests. Out of 97 sera collected from drug abusers in 1985-86 which had IgG antibody by Western blot test against HIV-1, 23 (23.7%) were HTLV-I antibody positive by ELISA test (Group 5), and 8 of these were confirmed by Western blot test. Among these 8 persons, IgM antibody against HTLV-I was found in 2, while that against HIV-1 was positive in 7 persons.(ABSTRACT TRUNCATED AT 250 WORDS)