Detection and delineation of CXCR-4 (fusin) as an entry and fusion cofactor for T-tropic [correction of T cell-tropic] HIV-1 by three different monoclonal antibodies.
A chemokine receptor, CXCR-4, has been identified as an entry cofactor for T cell line-tropic (T-tropic) HIV-1. To detect expression of CXCR-4 at the single cell level and dissect postbinding events of HIV-1 infection, we generated three mAbs against human CXCR-4. These mAbs inhibited SDF-1-induced intracellular Ca2+ mobilization, and one of the mAbs immunoprecipitated a specific 47-kDa component from CXCR-4+ cells. Flow cytometric analysis showed that most human cell lines examined expressed CXCR-4. A fraction of normal PBMC expressed CXCR-4, but neutrophils were negative. Two-color analysis revealed that the majority of T cells, virtually all B cells, and all monocytes expressed CXCR-4, while it was only weakly present on NK cells. Thus, expression of CXCR-4 is not ubiquitous but cell type specific in hemopoietic cells. The three mAbs were shown to suppress cell fusion mediated by envelope proteins of a T-tropic NL432 virus but not by those of an M-tropic JRCSF virus Likewise, they suppressed infection of NL432 but not that of an M-tropic NL162 virus. In both cases it was noted that the suppressive activity varied considerably among the mAbs. These data confirmed that CXCR-4 is directly involved in env-mediated entry and fusion of T-tropic HIV-1 and suggest that the epitopes on CXCR-4 recognized by the three mAbs may have different roles in interaction with the envelope proteins of T-tropic HIV-1.
Hori
T
T
Laboratory of AIDS Immunology, the Research Center for Immunodeficiency Virus, Kyoto University, Japan. thori@virus.kyoto-u.ac.jp
Sakaida
H
H
Sato
A
A
Nakajima
T
T
Shida
H
H
Yoshie
O
O
Uchiyama
T
T
D000818:Animals; D000911:Antibodies, Monoclonal; D015496:CD4-Positive T-Lymphocytes / Q000821:virology*; D002460:Cell Line; D005434:Flow Cytometry; D015686:Gene Products, env / Q000378:metabolism; D015497:HIV-1 / Q000254:growth & development*; D006801:Humans; D008264:Macrophages / Q000821:virology; D008561:Membrane Fusion; D051379:Mice; D019718:Receptors, CXCR4 / Q000276:immunology* / Q000378:metabolism; D014018:Tissue Distribution
D000911:Antibodies, Monoclonal; D015686:Gene Products, env; D019718:Receptors, CXCR4