Identification of membrane antigens important for adsorption of human T-cell leukaemia virus type I

Detection of human T-lymphotropic virus type I (HTLV-I) infection during coculture of HTLV-I infected and uninfected cells using inverse long PCR

OBJECTIVE

Identifying the new integration of human T-lymphotropic virus type I (HTLV-I) proviral genome into initially uninfected cells after cocultivation with HTLV-I infected cells is important for clarifying the process of infection. We examined the usefulness of inverse long polymerase chain reaction (IL-PCR) for this purpose.

METHODS

An experimental system using IL-PCR was applied to detect the transmission of HTLV-I between irradiated HTLV-I infected cells (HUT102) and uninfected targed cells (MOLT4, K562) after short-term and long-term coculturing.

RESULTS

In every coculture experiment with irradiated HTLV-I infected cells and uninfected cells, the new integration of HTLV-I was easily identified by IL-PCR. Oligoclonal proliferation of HTLV-I-positive cells was shown among MOLT4 cells even 4 months after the cocultivation; however, no evidence of viral replication was observed by indirect immunofluorescence assay or reverse transcription-PCR. We also used IL-PCR to assess the inhibitory effects of azidothymidine, anti-gp46, anti-vascular cell adhesion molecule-1 and anti-heat shock cognate protein 70 (HSC70) monoclonal antibody. Integration of HTLV-I provirus was inhibited in all of these cases except for anti-HSC70.

CONCLUSION

This experimental method enabled the detection of cell-to-cell transmission of HTLV-I directly and was useful for studying the mechanisms of cell-associated HTLV-I infection.

Cell-free entry of human T-cell leukemia virus type 1 to mouse cells

Human T-cell leukemia virus type 1 (HTLV-1) is the etiologic agent for adult T-cell leukemia and HTLV-1-associated myelopathy / tropical spastic paraparesis. Recently we infected newborn mice by inoculating HTLV-1-producing human cells, and found that T-cells, B-cells and granulocytes were infected in vivo. To understand the mechanism of viral-cell interaction and the pathogenesis of HTLV-1 using the mouse model, it is important to clarify the cellular tropism using a cell-free HTLV-1 transmission system. We employed a highly transmissible cell-free HTLV-1 produced by a feline kidney cell line, c77, and studied the susceptibility of 9 kinds of mouse cell lines, EL4, RLm1, CTLL-2, J774.1, DA-1, Ba / F3, WEHI-3, NIH3T3 and B1, and two kinds of human cell lines, Molt-4 and Hut78. HTLV-1 proviral sequence was found by PCR in all 9 mouse cell lines as well as in 2 human cell lines and viral entry was blocked with sera from an HTLV-1 carrier and an adult T-cell leukemia patient. Unexpectedly, mouse cell lines EL4 and RLm1 and human cell lines Molt-4 and Hut78 showed similar efficiency for viral entry. These results suggest a wide distribution of HTLV-1 receptor in mouse cells.

Isolation and characterization of a monoclonal antibody that inhibits HIV-1 infection

To identify a cell surface molecule other than CD4 involved in infection of cultured cells with human immunodeficiency virus type 1 (HIV-1), mice were immunized with the CD4-negative Raji human B-cell line in order to isolate a monoclonal antibody (mAb). We isolated mAb 33A, which inhibited the infection of CD4-positive T cells, B cells, human peripheral blood lymphocytes (PBL), and brain-derived cells with HIV-1. Formation of viral DNA was also blocked when CD4-positive Raji cells were treated with 33A after adsorption of HIV-1, but not before its adsorption. mAb 33A had little effect on syncytium formation induced by cocultivation with HIV-1-producing cells. Flow cytometry revealed that 33A reacted with HTLV-I-positive T-cell lines, Burkitt's lymphoma cell lines, phytohemagglutinin (PHA) -stimulated PBL, brain-derived fibroblast-like cells, and some adherent cell lines, but hardly at all with immature T-cell lines. Immunoblotting experiments showed that 33A recognized an antigen with an apparent molecular mass of 32 kDa, but did not recognize chemokine receptors such as CXCR4, CCR5, or CCR3. The distribution characteristic of the antigen recognized by 33A on various cells and its molecular weight suggest that mAb 33A recognizes a new cellular antigen that is necessary for HIV-1 entry.