DETECTION OF TRYPTASE TL(2) AND CD26 ANTIGEN IN BRAIN-DERIVED CELLS NONPERMISSIVE TO T-CELL LINE-TROPIC HUMAN-IMMUNODEFICIENCY-VIRUS TYPE-1

Tryptase TL(2) purified from MOLT-4 human T cells binds to the envelope protein of human immunodeficiency virus type 1 (HIV-1). Tryptase TL(2) and CD26 antigen are supposed to play roles in HIV-1 entry into cells. Although CD4 is a principal receptor for HIV-1, brain cells expressing the CD4 antigen are not permissive to HIV-1 strains infectious to monocyte or T-cell lines. We examined whether the non-permissiveness of the brain-derived cells to standard HIV-1 strains could be explained by a lack of tryptase TL(2) or CD26. Western blots showed that the amounts of tryptase TL(2) expressed in cell lysates prepared from the brain-derived cells were similar to those prepared from various cells susceptible to HIV-1 strains. Furthermore, flow cytometry revealed the presence of the CD26 antigen on the cell surface of many types of cells. The resistance of the brain-derived cells to standard HIV-1 strains is not due to a lack of tryptase TL(2) or CD26.