HTLV-II among injecting drug users in Stockholm

No evidence for xenotropic murine leukemia-related virus infection in Sweden using internally controlled multiepitope suspension array serology

Many syndromes have a large number of differential diagnoses, a situation which calls for multiplex diagnostic systems. Myalgic encephalomyelitis (ME), also named chronic fatigue syndrome (CFS), is a common disease of unknown etiology. A mouse retrovirus, xenotropic murine leukemia-related virus (XMRV), was found in ME/CFS patients and blood donors, but this was not corroborated. However, the paucity of serological investigations on XMRV in humans prompted us to develop a serological assay which cover many aspects of XMRV antigenicity. It is a novel suspension array method, using a multiplex IgG assay with nine recombinant proteins from the env and gag genes of XMRV and 38 peptides based on known epitopes of vertebrate gammaretroviruses. IgG antibodies were sought in 520 blood donors and 85 ME/CFS patients and in positive- and negative-control sera from animals. We found no differences in seroreactivity between blood donors and ME/CFS patients for any of the antigens. This did not support an association between ME/CFS and XMRV infection. The multiplex serological system had several advantages: (i) biotinylated protein G allowed us to run both human and animal sera, which is essential because of a lack of XMRV-positive humans; (ii) a novel quality control was a pan-peptide positive-control rabbit serum; and (iii) synthetic XMRV Gag peptides with degenerate positions covering most of the variation of murine leukemia-like viruses did not give higher background than nondegenerate analogs. The principle may be used for creation of variant tolerant peptide serologies. Thus, our system allows rational large-scale serological assays with built-in quality control.

Phylogeny-directed search for murine leukemia virus-like retroviruses in vertebrate genomes and in patients suffering from myalgic encephalomyelitis/chronic fatigue syndrome and prostate cancer

Gammaretrovirus-like sequences occur in most vertebrate genomes. Murine Leukemia Virus (MLV) like retroviruses (MLLVs) are a subset, which may be pathogenic and spread cross-species. Retroviruses highly similar to MLLVs (xenotropic murine retrovirus related virus (XMRV) and Human Mouse retrovirus-like RetroViruses (HMRVs)) reported from patients suffering from prostate cancer (PC) and myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS) raise the possibility that also humans have been infected. Structurally intact, potentially infectious MLLVs occur in the genomes of some mammals, especially mouse. Mouse MLLVs contain three major groups. One, MERV G3, contained MLVs and XMRV/HMRV. Its presence in mouse DNA, and the abundance of xenotropic MLVs in biologicals, is a source of false positivity. Theoretically, XMRV/HMRV could be one of several MLLV transspecies infections. MLLV pathobiology and diversity indicate optimal strategies for investigating XMRV/HMRV in humans and raise ethical concerns. The alternatives that XMRV/HMRV may give a hard-to-detect “stealth” infection, or that XMRV/HMRV never reached humans, have to be considered.

Human T Lymphotropic Virus Type 1 (HTLV-1): Molecular Biology and Oncogenesis

Human T lymphotropic viruses (HTLVs) are complex deltaretroviruses that do not contain a proto-oncogene in their genome, yet are capable of transforming primary T lymphocytes both in vitro and in vivo. There are four known strains of HTLV including HTLV type 1 (HTLV-1), HTLV-2, HTLV-3 and HTLV-4. HTLV-1 is primarily associated with adult T cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-2 is rarely pathogenic and is sporadically associated with neurological disorders. There have been no diseases associated with HTLV-3 or HTLV-4 to date. Due to the difference in the disease manifestation between HTLV-1 and HTLV-2, a clear understanding of their individual pathobiologies and the role of various viral proteins in transformation should provide insights into better prognosis and prevention strategies. In this review, we aim to summarize the data accumulated so far in the transformation and pathogenesis of HTLV-1, focusing on the viral Tax and HBZ and citing appropriate comparisons to HTLV-2.

High rate of human T lymphotropic virus type IIa infection in HIV type 1-infected intravenous drug abusers in Ireland

Serological and molecular analyses of a cohort of HIV-1-infected intravenous drug abusers (IVDAs) (n = 103) in Dublin, Ireland have demonstrated that 15 of 103 (14.6%) were infected with HTLV-II, which is the highest infection rate yet recorded for any European country. Restriction fragment length polymorphism (RFLP) analysis of the env region of the provirus demonstrated that the infection involved only the HTLV-IIa subtype; the HTLV-IIb subtype was not detected. Phylogenetic analysis of the nucleotide sequences of the long terminal repeat (LTR) confirmed infection with the HTLV-IIa subtype, and demonstrated that the viruses clustered closely with HTLV-IIa isolates from North American IVDAs. Previous observations that IVDAs in southern Europe, specifically Spain and Italy, appear to be infected predominantly with the HTLV-IIb subtype, along with the present report and evidence that IVDAs in Sweden are infected with the HTLV-IIa subtype, suggest different origins of HTLV-II infection in Europe.

Prevalence and risk factors for HTLV-II infection in 913 injecting drug users in Stockholm, 1994

The prevalence and risk factors for acquisition of human T-cell lymphotropic virus type I and II (HTLV-I and II) were investigated in a prospective study of 913 injecting drug users (IDUs) in Stockholm in 1994. Epidemiologic data were recorded, and blood samples were tested for antibodies against HTLV-I and HTLV-II; human immunodeficiency virus (HIV) types 1 and 2; and hepatitis A (HAV), B (HBV), C (HCV), and D (HDV). Positive serologic results for HTLV were confirmed by Western blot (WB) and polymerase chain reaction (PCR). Of the 905 participants with conclusive HTLV-II status, 29 (3.2%) were HTLV-II positive, and all but three were of Nordic descent. None was HTLV-I infected. One person was infected as early as 1981, before HIV had reached the IDU population in Sweden. The prevalence of HTLV-II infection was 12% among HIV-1-seropositive and 1.8% among HIV-1-seronegative participants. The overall seroprevalences were 14% for HIV-1, 0% for HIV-2, 41% for HAV, 75% for HBV, 92% for HCV, and 8% for HDV. Although amphetamine has been the main injecting drug in Sweden for several decades, heroin abuse combined with a debut of injecting drugs before 1975 was identified as the most important risk factor associated with HTLV-II infection. HAV and HIV seropositivity were also independent risk factors.

Human T-cell leukemia viruses: epidemiology, biology, and pathogenesis

The human T-cell lymphotropic viruses type I and type II are closely related human retroviruses that have similar biological properties, genetic organization and tropism for T lymphocytes. Along with the simian T-cell lymphoma virus type I, they define the group of retroviruses known as the primate T-cell leukemia/lymphoma viruses. Initially identified in 1980, the human T-cell lymphotropic virus type I has been implicated as the etiologic agent of adult T-cell leukemia/lymphoma and of a degenerative neurologic disorder known as tropical spastic paraparesis or human T-cell lymphotropic virus type I-associated myelopathy. The intriguing link between human T-cell lymphotropic virus type, T-cell malignancy, and a totally unrelated and non-overlapping neurological disorder suggests divergent and unique pathogenetic mechanisms. This review will address the epidemiology, molecular biology, and pathogenesis of human T-cell leukemia viruses.

Seroepidemiology of the human T-cell leukaemia/lymphoma viruses in Europe. The HTLV European Research Network

An extensive collaboration of laboratories and investigators has been developed to define the seroprevalence of human T-cell leukaemia/ lymphoma virus type I and II (HTLV-I and -II) infection in Europe. An algorithm for serological screening for HTLV-I and -II infection has been established by consensus. Data from screening almost 4 million subjects, including many unpublished studies, which conform to this algorithm are presented. In extensive studies the seroprevalence of HTL.V-I/II in blood donors is low, ranging from < 1 in 100,000 to 30 in 100,000 donors and is due predominantly to HTLV-I. In antenatal clinics in France and the United Kingdom the seroprevalence of HTLV-I is > 0.2%, but surveillance in this setting has been limited and extensive study of the seroprevalence of HTLV-I/II infection in pregnant women in Europe is urgently required to determine the need for HTLV-I/II antenatal screening. HTLV-I is present in populations who have immigrated to Europe from endemic areas and is spreading into indigenous European populations, particularly through sexual transmission to females. HTLV-II infection is present predominantly amongst IVDU and is usually a coinfection with HIV-I. There are considerable regional differences in HTLV-II seroprevalence.

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.

Human T-cell leukemia virus type II infection among high risk groups and its influence on HIV-1 disease progression

The prevalence and the risk factors of the human T-cell leukemia virus type I/II (HTLV-I/II) infection were evaluated among 552 individuals at high risk for HIV-1. HTLV infections showed a low (1.6%) prevalence, were restricted to intravenous drug addicts and were due to HTLV-II alone. Moreover, in order to weigh the influence of HTLV-II on the natural history of HIV-1 infection, the clinical outcome of HIV-1 disease was compared between subjects with and without HTLV-II coinfection. Our findings showed that HTLV-II does not adversely affect the outcome of HIV-1 infection. Infact, a slower disease progression has been recorded in some HTLV-II coinfected subjects.

HTLV infections among Swedish intravenous drug users in 1992

Serum samples collected in 1992 from 1158 intravenous drug users (IVDUs) in Stockholm, Sweden, were tested retrospectively for antibodies to human T-lymphotropic virus type I and II (HTLV-I and II). The overall prevalence rate of HTLV infections was 2.4% (28/1158). A majority of the HTLV infections were caused by HTLV-II (27/28). A significant association between HTLV-II and HIV-1 seropositivity was found, the prevalence of HTLV-II infection being 11.4% (11/96) in HIV-seropositive individuals compared with 1.5% (16/1062) in HIV-seronegative persons (p < 0.001). All the HTLV-infected individuals were of Scandinavian origin. No significant differences in age and sex distribution were observed in HTLV-infected persons compared to seronegative individuals. This study confirms that HTLV-II infection is present in the Swedish IVDU population and the findings provide baseline information for future epidemiological studies.

Prevalence of HTLV-I/II antibodies in HIV seropositive and HIV seronegative STD patients in Vellore region in southern India

This retrospective study was designed to determine the relationship between human T-lymphotropic virus (HTLV) type-I/II infection and human immunodeficiency virus (HIV) infection among sexually promiscuous persons in southern India. Stored sera collected between 1986 and 1993 from 822 male and 488 female patients attending clinics for sexually transmitted diseases (STD), for the purpose of HIV serosurveillance, were used. They comprised 376 HIV-positive sera and 934 HIV-negative sera. They were screened for HTLV-I/II antibody by a particle agglutination test and repeatedly reactive sera were confirmed by an immunofluorescence test and a western blot test. Five (2.4%) of 212 HIV-seropositive men were confirmed positive for HTLV-I/II antibody, while none of the 610 HIV-seronegative men were positive; the difference in prevalence between HIV-seropositive and seronegative men was statistically significant (p < 0.001). Nine (5.5%) of 164 HIV-seropositive women and 3 (0.9%) of 324 HIV-seronegative women were positive for HLTV-I/II antibody (p < 0.005). All HIV-seropositives taken together, had a significantly higher prevalence of HTLV-I/II (3.7%; 14/376) compared with HIV seronegatives (0.3%; 3/934; p < 0.001). Thus, in southern India, HTLV infection, like HIV infection, is sexually transmitted, though less effectively.