Human T-cell leukemia virus-associated membrane antigens: identity of the major antigens recognized after virus infection

Human T-cell leukemia virus type I: pseudotype neutralization of Japanese and American isolates with human and rabbit sera

CCC/2M, CCC/10Y and CCC/MT-2 cat kidney cells producing Japanese isolates of human T-cell leukemia virus type I (HTLVs) and HOS/PL human osteosarcoma cells producing an American isolate of HTLV were infected with vesicular stomatitis virus (VSV) to prepare VSV pseudotypes bearing envelope antigens of HTLVs. VSV propagated in CCC/2M cells contained plaque-forming fractions that were not neutralized by treatment with anti-VSV serum alone: VSV pseudotypes bearing envelope antigens of HTLV2M and CCC cat endogenous virus were formed by infection of CCC/2M cells with VSV. Japanese HTLV2M, HTLV10Y and HTLVMT-2 and American HTLVPL pseudotypes were neutralized by sera of Japanese, American and British patients with ATL. Each serum, including the serum of the patient from whom HTLV2M or HTLV10Y had been derived, gave similar antibody titers against Japanese and American HTLV pseudotypes. The HTLV pseudotypes were also neutralized by rabbit serum raised against HTLVMT-2. A rabbit antiserum against the C-terminal half of the HTLV env protein produced in E. coli also neutralized Japanese and American HTLV pseudotypes. Thus, VSV pseudotype analyses indicated that envelope antigens of HTLVs represent a single serotype worldwide. The env protein produced in E. coli may be used to raise neutralizing antibody against HTLVs.

A new HTLV-III/LAV encoded antigen detected by antibodies from AIDS patients

A newly identified protein from HTLV-III/LAV, the virus implicated as the etiologic agent of the acquired immune deficiency syndrome, was studied. This protein, which has a molecular weight of 27,000 (p27), was shown by amino acid sequencing to have a coding origin 3' to the env gene on the HTLV-III genome. The presence of antibodies to p27 in virus-exposed individuals indicated that this gene is functional in the natural host.

Production of a monoclonal antibody to a membrane antigen of human T-cell leukaemia virus (HTLV1/ATLV)-infected cell lines from a systemic lupus erythematosus (SLE) patient: serological analyses for HTLV1 infections in SLE patients

Human T-cell leukaemia virus (HTLV1/ATLV), which causes adult T cell leukaemia (ATL), is an infectious, lymphotrophic retrovirus unique for humans. The present study was undertaken to determine whether HTLV1 had any pathogenetic role for systemic lupus erythematosus (SLE). The incidence of antibodies to ATL cell-associated antigens (ATLA) in sera from patients with SLE and other collagen diseases was investigated by an indirect immunofluorescent cytoplasmic staining of an HTLV1-infected cell line (MT-1). A radioimmunoassay was also performed to detect antibodies to HTLV1 protein and crude membrane fraction derived from an HTLV1-producing cell line MT-2. Furthermore, an Epstein-Barr virus (EBV)-transformed B cell line (ES-1) was constructed from an SLE patient, which produced a monoclonal antibody (IgG, lambda) reactive to an HTLV1-related cell-membrane antigen expressed on MT-1 and MT-2 cells. The specific reactivity of the monoclonal antibody was analysed by an indirect immunofluorescent cell-membrane staining and a microcytotoxicity test. The incidence of anti-ATLA antibodies was not different among SLE and other collagen diseases. The monoclonal antibody produced by ES-1 stained and killed HTLV1-infected cell lines specifically, but did not react with other human lymphoid cell lines. This monoclonal antibody failed to react with peripheral blood mononuclear cells (PBMC), mitogen-induced T cell blasts, and iododeoxyuridine-treated T cells from SLE patients. Thus, a possible role of HTLV1 in the aetiology of SLE was not established.

trans-Activation of the human T-cell leukemia virus long terminal repeat correlates with expression of the x-lor protein

Cell lines established directly from adult T-cell leukemia-lymphoma patients or immortalized by human T-cell leukemia virus type I (HTLV-I) in vitro that do not produce complete HTLV virions were characterized both for the content of viral proteins and for the presence of trans-acting factors activating gene expression under the control of the HTLV long terminal repeat. The expression of the 42-kilodalton HTLV x-lor product correlated with trans-activation of the long terminal repeat. The implications of this study for understanding the role of the HTLV x-lor product in the initiation and maintenance of T-lymphocyte transformation are discussed.

Antibodies to human T-lymphotropic virus type-I in patients with tropical spastic paraparesis

10 out of 17 (59%) patients with tropical spastic paraparesis (TSP) had antibodies to human T-lymphotropic virus-I (HTLV-I), as did 5 out of 5 TSP patients with systemic symptoms. Only 13 out of 303 (4%) controls, made up of blood donors, medical personnel, and other neurological patients, had such antibodies. These findings suggest either that HTLV-I is neurotropic or that the virus or a related one contributes to the pathogenesis of TSP.

Expression of the pX gene of HTLV-I: general splicing mechanism in the HTLV family

Human T-cell leukemia virus type I (HTLV-I) is an etiological agent of adult T-cell leukemia. A viral gene pX encodes for p40X and it has been proposed that this protein trans-activates the viral long terminal repeat and possibly some cellular genes; this activation may be associated with T-cell transformation. The mechanism of pX gene expression and the primary structure of p40X are now reported. Two-step splicing generates the 2.1-kilobase pX mRNA; the initiator methionine for env becomes part of the pX protein. These splicing signals are conserved among all members of the HTLV family except for the acquired immune deficiency syndrome-associated viruses.

Nucleotide sequence analysis of a variant human T-cell leukemia virus (HTLV-Ib) provirus with a deletion in pX-I

A variant of human T-cell leukemia virus subgroup I (HTLV-I), designated HTLV-Ib, has been isolated from a transformed T-lymphocytic cell line established from a Zairian patient with adult T-cell lymphoma. A recombinant phage clone of the variant provirus, denoted lambda MC-1, hybridizes under high stringency to HTLV-I DNA probes, but 17 of 43 restriction enzyme sites differ from those of HTLV-I, 10 of them clustering within 1.5 kilobases in the env-pX region. Since this variant virus retains its capacity to transform T-cells in vitro, and since a pX product is suspected to be important in transformation, we have determined the nucleotide sequence of the entire pX region of this virus for comparison to the prototype HTLV-I. In addition, the region between the gag and pol genes, parts of the pol and env genes, and a portion of the U3 region of the long terminal repeat sequence were also analyzed. We noted 141 single-base-pair changes among 3,897 base pairs, which were relatively well distributed over those portions of the provirus that were examined. In addition, an 11-base-pair deletion was found which included the potential initiator ATG codon of the first open reading frame of pX (pX-I). The next potential initiator codon predicted by the sequence is followed by 10 codons and then a termination codon. An identical deletion was also demonstrated in the only provirus present in another cell line established from the same patient on a different occasion after transformation in vitro of normal human umbilical cord blood cells. These results indicate that pX-I is not required for transformation.

Major glycoprotein antigens that induce antibodies in AIDS patients are encoded by HTLV-III

Antibodies from the serum of patients with the acquired immune deficiency syndrome (AIDS) or with the AIDS-related complex and from the serum of seropositive healthy homosexuals, recognize two major glycoproteins in cells infected with human T-cell lymphotropic virus type III (HTLV III). These glycoproteins, gp160 and gp120, are encoded by the 2.5-kilobase open reading frame located in the 3' end of the HTLV-III genome, as determined by amino terminus sequence analysis of the radiolabeled forms of these proteins. It is hypothesized that gp160 and gp120 represent the major species of virus-encoded envelope gene products for HTLV-III.

A glycopolypeptide (gp 100) is the main antigen detected by HTLV-III antisera

Sera from homosexuals and hemophiliacs in Germany were examined for antibodies to human T-lymphotropic retrovirus type III (HTLV-III) by an enzyme-linked immunosorbent assay (ELISA) against purified virus. ELISA positive sera were used to search by immunoprecipitation for HTLV-III related antigens in a persistently infected human T-cell line. A glycopolypeptide with a mol. wt. of 100 000 was regularly recognized by all positive sera. In analogy to glycosylation and high antigenicity of envelope polypeptides of other mammalian retroviruses, gp 100 seemed to be related to the env gen. Two polypeptides with mol. wts. of 24 000 and 22 000 probably representing viral core polypeptides were additionally detected by sera with high ELISA titers.

Subcellular localization of the product of the long open reading frame of human T-cell leukemia virus type I

Human T-cell leukemia virus type I (HTLV-I) is a retrovirus associated with adult T-cell leukemia and lymphoma. In addition to containing the gag, pol, and env genes of the chronic leukemia viruses, the genome of HTLV-I contains a long open reading frame (LOR) located between the 3' end of the envelope gene and the 3' long terminal repeat sequence (LTR). It has been suggested that a protein of 42 kilodaltons that is encoded by the LOR region may participate in both trans-acting transcriptional regulation of the viral LTR as well as in the transforming properties of HTLV-I. It is reported here that a significant fraction of the 42-kilodalton HTLV LOR product is located in the nucleus of HTLV-I-infected transformed lymphocytes, a finding that is consistent with its proposed functions.

Antibodies to HTLV-III in Swiss patients with AIDS and pre-AIDS and in groups at risk for AIDS

We tested serum samples from Swiss subjects by three different assays based on enzyme-linked immunosorbent assay (ELISA) and Western blot techniques for antibodies to proteins associated with the recently discovered human T-cell leukemia/lymphoma virus HTLV-III, the putative etiologic agent for the acquired immunodeficiency syndrome (AIDS). Of 10 patients with AIDS and 10 with pre-AIDS, all were antibody-positive. Furthermore, 37 of 103 intravenous-drug addicts (36 per cent), 4 of 40 healthy homosexual men (10 per cent), 7 of 83 patients with various types of hepatitis (8.4 per cent), but none of 83 healthy blood donors or 10 other controls were antibody-positive. Antibodies to the major viral protein p24 were found consistently and at high titers in the seropositive members of the groups at risk and in those with pre-AIDS but were dramatically reduced in patients with AIDS. In contrast, antibodies to another virus-associated protein, p41, were present in all cases of AIDS and pre-AIDS but were absent in nearly 10 per cent of seropositive persons at risk. Whereas p41 and p24 thus appear to be the targets of choice for future screening tests, the ELISA test that is currently available is a useful screening tool.

Etiology of AIDS: biological and biochemical characteristics of HTLV-III

The newly identified human HTLV-III virus, the etiologic agent for AIDS, shares many of the biological and physicochemical properties common to a family of retroviruses named human T-cell leukemia (lymphotropic) viruses, or HTLV. Because of the similarities, and because of the uniform nomenclature for human T-cell leukemia (lymphotropic) viruses adopted at the first Cold Spring Harbor Meeting on HTLV (19, 79), this newly discovered virus associated with AIDS as HTLV-III was named HTLV-III. Other investigators making independent isolations of virus have suggested naming the virus lymphadenopathy virus or LAV (3, 16), immunodeficiency associated virus or IADV (48), AIDS-related virus (41). Immunological and nucleic acid comparison has now demonstrated that these viruses are, not surprisingly, very similar to HTLV-III (55, 63, 78). In view of the wide range of disease manifestations caused by the virus, and previous discussions concerning a uniform nomenclature for human T-lymphotropic retroviruses, it would seem ill-advised to restrict the name of this virus to one clinical manifestation of one disease. The frequent isolation of HTLV-III from patients with AIDS and ARC, the detection of antibodies specific for HTLV-III in nearly all patients with these diseases and in a high proportion of individuals at risk, and finally its effect on cells in vitro, leaves little doubt that HTLV-III is causatively involved in the development of these diseases. This etiologic association is further strengthened by the detection of HTLV-III infection in many instances where a direct cause-and-effect association can be made, e.g., hemophiliacs and children with AIDS, and blood from HTLV-III infected donors and the otherwise normal recipients of this blood who subsequently develop AIDS.

A monoclonal antibody specific for a 52,000-molecular-weight human T-cell leukemia virus-associated glycoprotein expressed by infected cells

A monoclonal antibody, designated HT462, is described which is specific for an antigen expressed in human T-cell leukemia/lymphoma virus (HTLV) preparations and by HTLV-infected cells. In indirect immunofluorescence assays, the antigen was detected on the surface of both HTLV-transformed producer and nonproducer cells, including cells infected in vitro with either HTLV subgroup I (HTLV-I) or HTLV-II. Normal human peripheral blood lymphocytes stimulated with phytohemagglutinin, cord blood T cells cultured with T-cell growth factor, and a variety of HTLV-negative T- and B-cell lines all lacked HT462 antigen expression. The HT462 antigen is a 52,000-molecular-weight glycoprotein, as shown by Western blotting procedures and treatment of viral preparations with neuraminidase, endoglycosidase F, and trypsin. The unglycosylated molecule is approximately 42,000 daltons. That the antigen is virus associated was demonstrated by its banding at the density of HTLV in gradients of metrizamide and by its concomitant synthesis with HTLV gag proteins after short-term culture of primary HTLV-positive leukemic cells. Differential expression of the HT462 antigen and HTLV gag-pol gene products was observed. In one case, low HT462 expression was correlated with the known inability of the particular cell line to produce syncytia in vitro. The properties of the HT462 antigen are most consistent with it being a gene product of the HTLV px region or else a cellular antigen specifically induced after viral infection. We cannot rule out, however, that the antigen is a variant cleavage product of the env gene. The monoclonal HT462 will be useful in further definition of the proteins and functions encoded by the env-px genetic sequence and in studying the biological properties of HTLV-transformed cells. Furthermore, the monoclonal, by recognizing HTLV-transformed nonproducers, will allow a greater spectrum of virus-infected cells to be detected.

Serological cross-reactivity between envelope gene products of type I and type II human T-cell leukemia virus

People exposed to type I human T-cell leukemia virus (HTLV-I) develop antibodies to an antigen at the surface of virus-infected cells, designated human T-cell leukemia virus membrane antigen (HTLV-MA). In an earlier study, we demonstrated that the major component of HTLV-MA is gp61, a glycoprotein encoded by the HTLV env gene. In the current study, we found that human antibodies that react with HTLV-MA on cells infected with HTLV-I react equally well with HTLV-MA on C3-44/MO, a target cell infected with type II HTLV. A glycoprotein with an approximate size of 67 kDa, gp67, was identified in C3-44/MO using immunoprecipitation and NaDodSO4/PAGE analysis. The positions of serine and cysteine residues were determined in the amino terminus of gp67 by radiolabel sequencing analysis. Comparison with the amino acid sequence deduced from the primary nucleotide sequence of HTLV-IIMO virus reveals that gp67 is also encoded, at least in part, by the env gene. The gp67 of HTLV-IIMO, like the env gene product of HTLV-ICR, gp61, is recognized both by antibodies from a HTLV-IIMO-infected patient with a variant form of hairy cell leukemia, and by antibodies from patients with HTLV-I-associated adult T-cell leukemia/lymphoma. These results indicate that, despite the divergence between HTLV-I and HTLV-II, the major env gene products of the two types of HTLV are conserved to the degree that they are serologically cross-reactive.

Infection of human endothelial cells by human T-cell leukemia virus type I

The effects of the human T-cell leukemia virus type I (HTLV-I) on cultured human endothelial cells were evaluated. Coculture of endothelial monolayers with either irradiated HTLV-producing lymphocytes or cell-free virus resulted in the production of multinucleated syncytia. The development of syncytia was inhibited by sera from patients with adult T-cell leukemia/lymphoma (ATLL). HTLV antigens were present on endothelial syncytia passaged in culture for greater than 3 months as detected by an anti-p19 monoclonal antibody, which detects a core protein of HTLV-I, and by ATLL sera. Moreover, these HTLV-infected endothelial cells were then able to infect and transform normal cord blood T lymphocytes with HTLV. These studies demonstrate that human endothelial cells are susceptible to productive HTLV-I infection in vitro and may have relevance for the spectrum of human disease associated with this family of retroviruses.

Aetiology of AIDS--antibodies to human T-cell leukaemia virus (type III) in haemophiliacs

Human T-cell leukaemia virus type III (HTLV-III) is suspected of having a key role in the pathogenesis of acquired immune deficiency syndrome (AIDS). Epidemiological data suggest that AIDS is transmitted by an infectious agent through intimate contact with body secretions, blood or blood products. To maintain haemostasis, many haemophiliac patients depend on commercially prepared clotting concentrates made from large multi-donor plasma pools and are thus at increased risk of developing the disease. We report here that, using indirect membrane immunofluorescence and radioimmunoprecipitation with SDS-polyacrylamide gel electrophoresis, we have detected antibodies to HTLV-III in 30 of 47 (64%) asymptomatic haemophiliacs and in all of three haemophiliacs who either had or soon developed AIDS. Of 34 samples drawn before 1984, 18 (53%) were antibody-positive, whereas of 16 samples drawn during 1984, 15 (94%) were positive (P less than or equal to 0.002). These data suggest that exposure to HTLV-III antigens is widespread among asymptomatic haemophiliacs.

Antigens encoded by the 3'-terminal region of human T-cell leukemia virus: evidence for a functional gene

Antibodies in sera from patients with adult T-cell leukemia-lymphoma or from healthy carriers of type I human T-cell leukemia virus (HTLV) recognize an antigen of approximately 42 kilodaltons (p42) in cell lines infected with HTLV-I. Radiolabel sequence analysis of cyanogen bromide fragments of p42 led to the conclusion that this antigen is encoded in part by LOR, a conserved portion of the "X" region that is flanked by the envelope gene and the 3' long terminal repeat of HTLV-I. It is possible that this novel product mediates the unique transformation properties of the HTLV family.

Homology of genome of AIDS-associated virus with genomes of human T-cell leukemia viruses

A T lymphotropic virus found in patients with the acquired immune deficiency syndrome (AIDS) or lymphadenopathy syndrome has been postulated to be the cause of AIDS. Immunological analysis of this retrovirus and its biological properties suggest that it is a member of the family of human T-lymphotropic retroviruses known as HTLV. Accordingly, it has been named HTLV-III. In the present report it is shown by nucleic acid hybridization that sequences of the genome of HTLV-III are homologous to the structural genes (gag, pol, and env) of both HTLV-I and HTLV-II and to a potential coding region called pX located between the env gene and the long terminal repeating sequence that is unique to the HTLV family of retroviruses.

Sequence of the envelope glycoprotein gene of type II human T lymphotropic virus

The sequence of the envelope glycoprotein gene of type II human T lymphotropic virus (HTLV) is presented. The predicted amino acid sequence is similar to that of the corresponding protein of HTLV type I, in that the proteins share the same amino acids at 336 of 488 residues, and 68 of the 152 differences are of a conservative nature. The overall structural similarity of these proteins provides an explanation for the antigenic cross-reactivity observed among diverse members of the HTLV retrovirus family by procedures that assay for the viral envelope glycoprotein, for example, membrane immunofluorescence.

Antibodies reactive with human T-lymphotropic retroviruses (HTLV-III) in the serum of patients with AIDS

In cats, infection with T-lymphotropic retroviruses can cause T-cell proliferation and leukemia or T-cell depletion and immunosuppression. In humans, some highly T4 tropic retroviruses called HTLV-I can cause T-cell proliferation and leukemia. The subgroup HTLV-II also induces T-cell proliferation in vitro, but its role in disease is unclear. Viruses of a third subgroup of human T-lymphotropic retroviruses, collectively designated HTLV-III, have been isolated from cultured cells of 48 patients with acquired immunodeficiency syndrome (AIDS). The biological properties of HTLV-III and immunological analyses of its proteins show that this virus is a member of the HTLV family, and that it is more closely related to HTLV-II than to HTLV-I. Serum samples from 88 percent of patients with AIDS and from 79 percent of homosexual men with signs and symptoms that frequently precede AIDS, but from less than 1 percent of heterosexual subjects, have antibodies reactive against antigens of HTLV-III. The major immune reactivity appears to be directed against p41, the presumed envelope antigen of the virus.

Serological analysis of a subgroup of human T-lymphotropic retroviruses (HTLV-III) associated with AIDS

The two main subgroups of the family of human T-lymphotropic retroviruses (HTLV) that have previously been characterized are known as HTLV-I and HTLV-II. Both are associated with certain human leukemias and lymphomas. Cell surface antigens (p61 and p65) encoded by HTLV-I are frequently recognized, at low titers, by antibodies in the serum of patients with acquired immunodeficiency syndrome (AIDS) or with signs or symptoms that precede AIDS (pre-AIDS). This suggests an involvement of HTLV in these disorders. Another subgroup of HTLV, designated HTLV-III, has now been isolated from many patients with AIDS and pre-AIDS. In the studies described in this report, virus-associated antigens in T-cell clones permanently producing HTLV-III were subjected to biochemical and immunological analyses. Antigens of HTLV-III, specifically detected by antibodies in serum from AIDS or pre-AIDS patients and revealed by the Western blot technique, are similar in size to those found in other subgroups of HTLV. They include at least three serologically unrelated antigenic groups, one of which is associated with group-specific antigens (p55 and P24) and another with envelope-related (p65) proteins, while the antigens in the third group are of unknown affiliation. The data show that HTLV-III is clearly distinguishable from HTLV-I and HTLV-II but is also significantly related to both viruses. HTLV-III is thus a true member of the HTLV family.

Transfusion-associated AIDS: serologic evidence of human T-cell leukemia virus infection of donors

An assay for antibodies to membrane antigens of cells infected by human T-cell leukemia virus was used to examine serum from persons who donated blood to 12 patients with acquired immunodeficiency syndrome (AIDS) associated with blood transfusions. The occurrence of positive results in the assay was significantly greater among donors to the AIDS patients (9 of 117; 7.7 percent) than among random donors (1 of 298; 0.3 percent). Of 12 sets of donors examined, 9 sets included a donor whose serum gave positive results for the presence of the antibodies. In six of these nine sets, the seropositive donor was an individual who was also identified as a possible source of AIDS transmission when epidemiologic and immunologic criteria were used.