Detection of tryptase TL2 and CD26 antigen in brain‐derived cells non‐permissive to T ‐cell line‐tropic human immunodeficiency virus type 1

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Abstract
Tryptase TL2 purified from MOLT‐4 human T cells binds to the envelope protein of human immunodeficiency virus type 1 (HIV 1). Tryptase TL2 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 TL2 or CD26. Western blots showed that the amounts of tryptase TL2 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 TL2 or CD26.