Search

The adult T-cell leukemia (ATL)-associated antigen complex (ATLA) was first discovered with indirect immunofluorescence by Hinuma et al. (1981). Biochemical analysis with MT-2 cells revealed that ATLA consisted mainly of human T-cell leukemia virus (HTLV) structural polypeptides and their precursors (Yamamoto and Hinuma 1982a; Schneider et al. 1984). In this study, we have investigated the molecular nature of the ATLA antigen complex in various HTLV-positive human cell lines established by different methods including independently established HTLV-infected HUT 102 cells. We found that HTLVs infecting these cell lines have similar core polypeptides, p24 and p19, as well as an envelope glycopolypeptide, gp46, in all these cells. The intracellular gp61 and p53 appear to be precursors of the viral envelope and core polypeptides, respectively. Interestingly, MT-2 and MT-2 related T-cell lines contain two different species of envelope proteins, gp68 and gp61, whereas cell lines not related to MT-2 express only gp61.

Seventy-one sera from Japanese individuals infected with human T cell leukemia virus type I (HTLV-I) were examined for the presence of antibodies to HTLV-III by an enzyme-linked immunosorbent assay (ELISA) and by a strip radioimmunoassay based on the Western blot technique. The sera were from 23 healthy carriers and from 48 patients, including 18 with smoldering adult T cell leukemia (ATL), 13 with chronic ATL, and 17 with acute ATL. All people tested lived in the southwestern part of Japan, a known endemic area for HTLV-I infection. Antibodies against HTLV-I were detected in all sera both by indirect immunofluorescent methods and strip radioimmunoassay using cell lysates. Six sera were reactive in the ELISA assay for HTLV-III. But these sera did not react specifically to HTLV-III-related proteins (p15, p24, gp41) when analyzed by strip radioimmunoassay. Our data suggest that coincidental infection of HTLV-I and HTLV-III is quite rare in Japan.

Antibodies against human T-cell lymphotropic virus type I (HTLV-I) in the sera from 60 patients with adult T-cell leukemia and 21 carriers who were suspected of having HTLV-I infection were investigated by indirect immunofluorescence assay (IFA), enzyme-linked immunosorbent assay (ELISA), membrane immunofluorescence assay (MIA) and strip radio immunoassay based on the western blotting technique (SRIA). The sera of 2 of the carriers who were seropositive in IFA and ELISA were negative in MIA and did not react with virus-specific proteins by SRIA. Two sera were negative in IFA and ELISA. These sera were positive in MIA and reacted with only the envelope-related glycoprotein (gp46) and not with gag-related proteins (p28, p24, p19) by SRIA. These findings suggest that the main antigens defined by IFA and ELISA are gag-related proteins and some sera which do not contain anti-HTLV-I antibodies give false-positive results because of the reaction to unknown cellular components. Also some sera may have antibodies against only envelope glycoproteins, and these sera may give false-negative results in IFA and ELISA.

A newly found human retrovirus, adult T-cell leukemia virus (ATLV) was shown by means of membrane immunofluorescence to bind to various hematopoietic cells including T-, B- and non-T, non-B-cell lines. Partially purified viral gp46 from culture fluids of ATL virus producer lines also bound efficiently to an ATLV-negative T-cell line, CCRF-CEM cells. When the viruses were pre-incubated with anti-ATLV-positive human sera, ATLV binding to the cells was clearly inhibited but not by pre-incubation with anti-ATLV-negative sera. These data suggest that: (1) ATLV binds not only to T-cells but also to multiple types of cells of hematopoietic origin; (2) anti-ATLV antibody-positive human sera have the blocking antibody for the binding of ATLV to lymphoid cells.

Adult T-cell leukemia-associated membrane antigen (ATLMA) expressed on the surface of living ATL virus (ATLV)-carrying cells was investigated by an indirect membrane immunofluorescence method using natural antibodies to ATLV in human sera. All the ATLV-positive cell lines tested that had cytoplasmic ATL-associated antigen (ATLA) detectable in acetone-fixed cell smears were also positive for ATLMA, but ATLMA was not detected in any ATLV-negative cell lines. The frequencies of ATLA- and ATLMA-bearing cells in seven cell lines tested were roughly parallel. The frequency of expression of both ATLMA and ATLA in cultures of MT-1 cells increased in the presence of 5-iodo-2'-deoxyuridine. All human sera having ATLA antibody had ATLMA antibody and the titers of the two were similar in most of the sera. The anti-ATLMA titers of human sera determined by using an ATLV-bound non-ATL T-cell line as antigen were also similar to the anti-ATLA titers. Absorption of anti-ATLMA-positive sera with living MT-2 cells, in which almost 100% of the cells express ATLA and ATLMA, caused parallel decreases in the anti-ATLA and anti-ATLMA titers. Analysis of the 125I-labeled surface of MT-2 cells by immunoprecipitation with anti-ATLMA-positive human serum followed by gel electrophoresis revealed that p19, p24, p28, and p46 polypeptides were specifically precipitated. These data suggest that ATLMA on the cell surface is not distinguishable from ATLA in the cytoplasm.

Eight lymphoblastoid cell lines were established from the peripheral blood of individual African green monkeys (AGM). The AGM-2206 line grew out spontaneously. The others - AGM-6, 7, 8, 10, 12, 13, and 16 - were obtained after infection of peripheral AGM lymphocytes with cell-free culture supernatant of AGM-2206. All lines contained, and were probably transformed by, AGM-EBV. Moreover, they expressed immunoglobulins but lacked the Leu l T-cell marker. Thus they were B cells. Since a high percentage of AGMs are naturally infected with a virus similar to adult T-cell leukemia virus (ATLV), we examined these cell lines for ATLV. With immunofluorescence tests we detected ATLV-related antigens (ATLA) in three of the eight cell lines. EBV membrane antigen was present in three out of four. The highest percentage (40%) of ATLA-positive cells was found in the AGM-13 line. After metabolic labelling of these cells, ATLV-specific polypeptides p24, p19, p15, and p10 were detected. Hybridization experiments showed that both AGM-2206 and AGM-13 cell lines contained ATLV-proviral DNA. Electron micrographs of AGM-13 revealed a few type-C particles morphologically similar to the MT-2 virus. By cocultivation this AGM virus was able to infect and immortalize human peripheral blood lymphocytes. One such human cell line, NA-13, expressed polypeptides closely related to ATLV core antigens but a 68,000 mol.wt. glycopolypeptide was serologically distinct from MT-2 ATLV gp68.

We have examined expression of antigens defined by HT462 monoclonal antibody (mAb), together with other HTLV-I related antigens using phorbol 12-myristate 13-acetate treated leukemic mature T cells. Thirteen patients with adult T-cell leukemia (ATL), 3 patients in remission states of ATL and 5 patients with non-ATL were examined. All ATL cells expressed the HT462 antigen, however cells from patients in remission did not express the HT462 antigen. A low percentage of cells from 2 out of 5 patients with non-ATL mature leukemic T cells expressed the HT462 antigen, although these cells did not express other HTLV-I related antigens. Cells of HTLV-I infected human cell lines expressed the HT462 antigen. Three HTLV-I infected rat cell lines (TARS-1, TART-1, TARL-2) did not express the HT462 antigen, although cells of these lines expressed other HTLV-I related antigens. Characterization of the HT462 antigen by strip radioimmunoassay based on western blotting technique using cell lysates of HUT102 cells revealed two additional bands (p68, p35) together with previously reported proteins (gp52, p42). Only p68 was seen in western blots using cell lysates of the rat cell lines. These findings further suggest that the HT462 antigen is a cellular component induced in virus transformed human cells and not a virus encoded protein.

We have compared the structural polypeptides of an adult T-cell leukaemia (ATL) virus (ATLV) isolate from a Japanese patient with ATL with those of a similar virus derived from a Japanese macaque monkey. Both are distinct but related entities. Their core polypeptides p19 could not be distinguished, but p24, another core polypeptide, and their envelope glycopolypeptides differ. The human virus directs the synthesis of a single intracellular glycopolypeptide, gp68, while the macaque virus specifies two such glycopolypeptides, gp57 and gp50. Furthermore, the glycopolypeptides of both viruses are serologically distinct. Thus, these viruses represent subtypes of the ATLV family and the macaque virus is apparently not involved in human ATL.