Polymorphic Nature of Human T-Cell Leukemia Virus Type 1 Particle Cores as Revealed through Characterization of a Chronically Infected Cell Line.

Human T-cell leukemia virus type 1 (HTLV-1) is the etiological agent of adult T-cell leukemia (ATL) and HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). HTLV-1 cell-to-cell transmission is dependent on the release of infectious virus particles into the virological synapse. The HTLV-1 particle structure is still poorly understood, and previous studies analyzed viruses produced by transformed lymphocytic cell lines chronically infected with HTLV-1, particularly the MT-2 cell line, which harbors truncated proviruses and expresses aberrant forms of the Gag protein. In this study, we demonstrate that the chronically infected SP cell line harbors a relatively low number of proviruses, making it a more promising experimental system for the study of the HTLV-1 particle structure. We first identified the genomic sites of integration and characterized the genetic structure of the gag region in each provirus. We also determined that despite encoding a truncated Gag protein, only the full-length Gag protein was incorporated into virus particles. Cryo-transmission electron microscopy analyses of the purified virus particles revealed three classes of particles based upon capsid core morphology: complete cores, incomplete cores, and particles without distinct electron densities that would correlate with the capsid region of a core structure. Observed cores were generally polygonal, and virus particles were on average 115 nm in diameter. These data corroborate particle morphologies previously observed for MT-2 cells and provide evidence that the known poor infectivity of HTLV-1 particles may correlate with HTLV-1 particle populations containing few virus particles possessing a complete capsid core structure.IMPORTANCE Studies of retroviral particle core morphology have demonstrated a correlation between capsid core stability and the relative infectivity of the virus. In this study, we used cryo-transmission electron microscopy to demonstrate that HTLV-1 particles produced from a distinct chronically infected cell line are polymorphic in nature, with many particles lacking organized electron densities that would correlate with a complete core structure. These findings have important implications for infectious HTLV-1 spread, particularly in the context of cell-to-cell transmission, a critical step in HTLV-1 transmission and pathogenesis.

Rat lymphoid cell lines with human T cell leukemia virus production. I. Biological and serological characterization.

Cocultivation of spleen cells, lymph node cells, and thymocytes of female Wistar-King-Aptekman rats with short-term cultured male adult T cell leukemia (ATL) cells in the presence of 5-bromo-2'-deoxyuridine (BrdUrd) resulted in the establishment of rat lymphoid cell lines, TARS-1, TARL-2, and TART-1. Cytogenetic analysis of the three cell lines showed a female rat karyotype with 42 chromosomes. The surface phenotypes of TARS-1 and TART-1 were those of rat T cells. TARL-2 was only positive for rat Ia and leukocyte common antigens. The cell lines continuously produced a type C retrovirus, human T cell leukemia virus (HTLV) and expressed ATL-associated antigens. TARS-1 and TART-1, but not TARL-2 were transplantable into newborn syngeneic rats and nude mice. These results strongly indicate that HTLV not only immortalizes, but also transforms rat T cells in vitro. Adult rats immunized with either TARS-1 or TARL-2 produced antibodies specific for HTLV. The biochemical analysis of the antigens that reacted with rat sera revealed that they are the two HTLV-specific polypeptides, p24 and p28.

Sequence homology and morphologic similarity of HTLV-III and visna virus, a pathogenic lentivirus.

A study was conducted of the genetic relation between human T-cell lymphotropic retroviruses and visna virus. The human T-cell lymphotropic viruses include those associated with T-cell malignancies (HTLV-I and HTLV-II) as well as the etiologic agent of the acquired immune deficiency syndrome (HTLV-III). Visna virus, a slowly replicating and pathogenic but nononcogenic retrovirus of sheep, is a member of the subfamily Lentivirinae. Results obtained by molecular hybridization and heteroduplex analysis indicated that a greater extent of nucleotide sequence homology exists between HTLV-III and visna virus than between HTLV-III and any of the other viruses. The homology observed under conditions of low stringency spanned the entire genome, but was strongest in the gag/pol region. The morphogenesis and fine structure of HTLV-III and visna virus also demonstrated striking similarities. The data provide strong evidence for a close taxonomic and thus evolutionary relation between HTLV-III and the Lentivirinae subfamily.

HTLV-V: a new human retrovirus isolated in a Tac-negative T cell lymphoma/leukemia.

A new human retrovirus was isolated from a continuous cell line derived from a patient with CD4+ Tac- cutaneous T cell lymphoma/leukemia. This virus is related to but distinct from human T cell leukemia/lymphoma virus types I and II (HTLV-I and HTLV-II) and human immunodeficiency virus (HIV-1). With the use of a fragment of provirus cloned from one patient with T cell leukemia, closely related sequences were found in DNA of the cell line and of tumor cells from seven other patients with the same disease; these sequences were only distantly related to HTLV-I. The phenotype of the cells and the clinical course of the disease were clearly distinguishable from leukemia associated with HTLV-I. All patients and the wife of one patient showed a weak serological cross-reactivity with both HTLV-I and HIV-1 antigens. None of the patients proved to be at any apparent risk for HIV-1 infection. The name proposed for this virus is HTLV-V, and the date indicate that it may be a primary etiological factor in the major group of cutaneous T cell lymphomas/leukemias, including the sporadic lymphomas known as mycoses fungoides.

Productive infection and cell-free transmission of human T-cell leukemia virus in a nonlymphoid cell line.

Human T-cell leukemia virus (HTLV), American PL isolate, was transmitted by cocultivation and by cell-free filtrates to a nonlymphoid human osteogenic sarcoma (HOS) cell line, designated HOS/PL, but not to nine other lines bearing receptors for HTLV. HOS and HOS/PL cells are not dependent on interleukin-2 and do not express interleukin-2 receptors that are recognized by anti-Tac monoclonal antibody. HTLV released by the Japanese MT2 cell line was also transmitted to HOS cells. The infected HOS cells release substantial titers of progeny HTLV which is antigenically indistinguishable from parental virus and is able to transform T cells.

Selective tropism of lymphadenopathy associated virus (LAV) for helper-inducer T lymphocytes.

Lymphadenopathy associated virus ( LAV ) has been isolated from patients with the acquired immunodeficiency syndrome (AIDS) or lymphadenopathy syndrome. Since the immune deficiency in AIDS seems to be primarily related to the defect of the helper-inducer T lymphocyte subset, the possibility that LAV is selectively tropic for this subset was investigated. Fractionation of T lymphocytes was achieved by cellular affinity chromatography with monoclonal antibodies. In a hemophilic patient who was a healthy carrier of LAV , reverse transcriptase activity and virus particles detected by electron microscopy were found only in cultures of helper-inducer lymphocytes. When infected with LAV in vitro, lymphocyte subsets from normal individuals yielded similar results. Virus production was associated with impaired proliferation, modulation of T3-T4 cell markers, and the appearance of cytopathic effects. The results provide evidence for the involvement of LAV in AIDS.

Isolation of lymphocytopathic retroviruses from San Francisco patients with AIDS.

Infectious retroviruses have been detected in 22 of 45 randomly selected patients with acquired immune deficiency syndrome (AIDS) and in other individuals from San Francisco. The AIDS-associated retroviruses (ARV) studied in detail had a type D morphology, Mg2+-dependent reverse transcriptase, and cytopathic effects on lymphocytes. The viruses can be propagated in an established adult human T cell line, HUT-78. They cross-react with antiserum to the lymphadenopathy-associated retrovirus isolated from AIDS patients in France. Antibodies to ARV were found in all 86 AIDS patients and in a high percentage of 88 other homosexual men in San Francisco. This observation indicates the widespread presence of these lymphocytopathic retroviruses and their close association with AIDS.

Frequent detection and isolation of cytopathic retroviruses (HTLV-III) from patients with AIDS and at risk for AIDS.

Peripheral blood lymphocytes from patients with the acquired immunodeficiency syndrome (AIDS) or with signs or symptoms that frequently precede AIDS (pre-AIDS) were grown in vitro with added T-cell growth factor and assayed for the expression and release of human T-lymphotropic retroviruses (HTLV). Retroviruses belonging to the HTLV family and collectively designated HTLV-III were isolated from a total of 48 subjects including 18 of 21 patients wih pre-AIDS, three of four clinically normal mothers of juveniles with AIDS, 26 of 72 adult and juvenile patients with AIDS, and from one of 22 normal male homosexual subjects. No HTLV-III was detected in or isolated from 115 normal heterosexual subjects. The number of HTLV-III isolates reported here underestimates the true prevalence of the virus since many specimens were received in unsatisfactory condition. Other data show that serum samples from a high proportion of AIDS patients contain antibodies to HTLV-III. That these new isolates are members of the HTLV family but differ from the previous isolates known as HTLV-I and HTLV-II is indicated by their morphological, biological, and immunological characteristics. These results and those reported elsewhere in this issue suggest that HTLV-III may be the primary cause of AIDS.

New human T-lymphotropic retrovirus related to simian T-lymphotropic virus type III (STLV-IIIAGM).

This report describes serologic evidence for a virus similar to that known as simian T-lymphotropic virus type III of African Green monkeys (STLV-IIIAGM) infecting apparently healthy people in Senegal, West Africa, and the isolation of virus from these individuals. Serum samples from selected healthy West African people showed unusual serologic profiles when tested with antigens of HTLV-III/LAV, the etiologic agent of AIDS, and of STLV-IIIAGM. The samples reacted strongly with all of the major viral antigens of STLV-IIIAGM but showed variable or no reactivity with the major viral antigens of HTLV-III/LAV by radioimmunoprecipitation and sodium dodecyl sulfate-polyacrylamide gel electrophoresis. A new human T-lymphotropic virus (HTLV-IV) isolated from these people was grown in vitro and shown to have retroviral type particles, growth characteristics, and major viral proteins similar to those of the STLV-III and HTLV-III/LAV group of retroviruses. The gp120/160, gp32, p64, p55, p53, p24, and p15 proteins precipitated were the same size as and reactive with STLV-IIIAGM proteins. The serologic data suggest that this virus shares more common epitopes with STLV-IIIAGM than with the prototype HTLV-III/LAV that infects people in the United States and Europe. Further study of this virus and of the origin of the HTLV-III/LAV group of viruses may expand our understanding of the human AIDS virus.

Evidence for HTLV-III in T-cells from semen of AIDS patients: expression in primary cell culture, long-term mitogen-stimulated cell cultures, and cocultures with a permissive T-cell line.

The development of acquired immunodeficiency syndrome or of acquired immunodeficiency syndrome-related complex by transmission of human T-lymphotropic retrovirus III by semen has previously been implicated by epidemiological studies. In vitro investigations were performed on mononuclear cells obtained from the semen of patients with acquired immunodeficiency syndrome to identify human T-lymphotropic retrovirus III or related retrovirus. The presence of human T-lymphotropic retrovirus III was demonstrated (a) in primary cell cultures, by the detection of the Mr 24,000 protein by indirect immunofluorescence assays by Day 6; (b) in activated long-term cell culture by reverse transcriptase activity, by indirect immunofluorescence (Mr 24,000 protein); and (c) in cocultures of T-cells from semen of AIDS patients and H9 cells by reverse transcriptase activity, indirect immunofluorescence, and the presence of virus particles by electron microscopy.

Antiviral agents with activity against human retroviruses.

The ability of various known anti-HIV antivirals to inhibit four different strains of human immunodeficiency virus type 1 (HIV-1), a strain of type 2 (HIV-2), and a human T-cell lymphotropic virus type I (HTLV-I) was tested. The tested substances included two sulfated polysaccharides (lentinan sulfate and dextran sulfate) and a nonsulfated polysaccharide PSK, E-P-LEM, glycyrrhizin sulfate, and nucleoside analogues (AZT and DHT). The effects of the substances were measured quantitatively with two different assays: (i) inhibition of cell-free viral infection and (ii) inhibition of the fusion reaction induced by cell-to-cell infection. The results showed that cell-free infection of HIV-1 and HIV-2 was almost completely blocked in the presence of all of the substances tested. However, cell-to-cell infection by HIV-1, HIV-2, and HTLV-I was inhibited only by the polysaccharides, E-P-LEM, and glycyrrhizin sulfate but not by the two nucleoside analogues. Moreover, the extent of inhibition of the fusion reaction by the substances varied significantly from strain to strain in HIV-1.

In vitro infection of human B lymphocytes with adult T-cell leukemia virus.

Experimental transmission of adult T-cell leukemia (ATL) virus (ATLV) into human B lymphocytes was attempted. Cocultivation of B-cell rich fraction of peripheral blood from a healthy adult with X-ray irradiated ATLV producer MT-2 cells resulted in the establishment of OKA(B) cell line co-infected with both Epstein-Barr virus (EBV) and ATLV. OKA(B) cells and its subclones contained: (1) B cell markers exclusively; (2) both EBV-specific antigen, EBNA and ATLV-specific antigen, ATLA detected by immunofluorescence test; (3) ATLV-specific polypeptides, p24 and p19; (4) ATLV-specific mRNA in ATLA-positive clones; (5) ATLV and EBV particles detectable by electron microscopy. These data clearly show that human B lymphocytes are susceptible to ATLV infection.

HTLV-I infection of cerebrospinal fluid T cells from patients with chronic neurologic disease.

Antibodies reacting with HTLV-I, the etiologic agent of acute T cell leukemia/lymphoma and a transforming agent for T4-positive lymphocytes in vitro, have recently been described in sera of patients with chronic neurologic disease in the absence of lymphoproliferative disorders. The largest number of such cases was described in Japan and in the Caribbean and parts of South America. We report here two cases of patients with chronic neurologic disease whose cerebrospinal fluid (CSF)-derived T cells contain HTLV-I specific RNA sequences and antigens and are expressing retroviral particles. Only one of these patients has demonstrable antibody to HTLV-I in serum or CSF.

Pathologic features of AIDS encephalopathy in children: evidence for LAV/HTLV-III infection of brain.

The neuropathologic findings in 11 children with a new CNS disorder that occurs in children with the acquired immunodeficiency syndrome (AIDS) and is postulated to be due to LAV/HTLV-III, the virus that causes AIDS, are reported. The children, who ranged in age from 4 months to 11 years, died of AIDS complicated by progressive encephalopathy. Ten of the children either had positive serum antibody for LAV/HTLV-III or had received blood products from donors later found to be antibody-positive. Examination of the brains of these children at autopsy revealed a unique constellation of findings, including varying degrees of diminished brain weight in all cases, inflammatory cell infiltrates in nine brains, multinucleated cells in eight, three of which also contained multinucleated giant cells, vascular calcification in ten, vascular and perivascular inflammation in five, and white matter changes in nine. Inflammatory and vascular lesions were most prominent in basal ganglia and pons. LAV/HTLV-III retroviral particles, associated with multinucleated giant cells, were observed in two brains on electron microscopic examination. These two and one additional brain had evidence of the LAV/HTLV-III genome by hybridization studies. Only one brain had a recognizable opportunistic infection.

Morphologic and immunoelectronmicroscopic identification of human T-cell lymphotropic virus type III (HTLV-III).

The AIDS associated HTLV-III virus infected H9 cells were extensively studied using light, scanning and transmission electronmicroscopy. It was demonstrated that the morphological features of HTLV-III are different from the C-type particles and are similar to those of lentiviridae. For immunological identification high titer pre-AIDS patient sera served as the anti-HTLV-III envelope antibody source. The immunoelectronmicroscopic method was able to identify the viral envelope antigen on the surface of infected cells and in certain areas of the viral envelope. This is the first application of immunoelectronmicroscopy for the identification of the HTLV-III virus.

Biological properties of HTLVIII.

Since the first discovery of HTLVIII 2 years ago, there have been remarkable advances in the molecular characterization of the virus, our understanding of its replication and the development of serological tests. But a great deal remains to be elucidated about the natural history of viral transmission and of the spectrum of disease resulting from infection.

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.

[Ultrastructural characteristics of the blood lymphocytes in some forms of sporadic T-cell lympholeukemia and leukemia associated with the HTLV virus]. / Ul'trastrukturnye osobennosti limfotsitov krovi pri nekotorykh formakh sporadicheskogo T-kletochnogo limfoleikoza i leikoza, assotsiirovannogo s virusom HTLV.

The electron microscopic study of the blood cells in some patients with sporadic T-cell acute lymphoblastic leukemias has shown some ultrastructural peculiarities similar to T-cell lympholeukemia associated with HTLV virus, that is important for the further elucidation of etiology and pathogenesis of the T-cell lymphoproliferative diseases.