Cross-linking of Fas by antibodies to a peculiar domain of gp120 V3 loop can enhance T cell apoptosis in HIV-1-infected patients.
Previous studies have demonstrated that T cell-reactive antibodies in HIV-1 infection contribute to lymphocyte depletion by cytotoxicity that involves differential membrane targets, such as the 43.5-kD receptor on CEM cells. Here, we show that these antibodies bind Fas as result of a molecular mimicry of the gp120. Both flow cytometry and immunoblotting using the human Fas-transfected mouse WC8 lymphoma revealed positive binding of immunoglobulin G from several patients to a 43.8-kD membrane receptor that also reacts with the CH11 anti-Fas monoclonal antibody. Specificity to Fas was further confirmed to chimeric recombinant human Fas-Fc by ELISA, whereas overlapping peptide mapping of a Fas domain (VEINCTR-N) shared by gp120 V3 loop demonstrated a predominant affinity to the full-length 10-mer peptide. Four anti-Fas affinity preparations greatly increased the subdiploid DNA peak of CEM cells similar to agonist ligands of Fas. In addition, anti-Fas immunoglobulin G strongly inhibited the [3H]thymidine uptake of CEM cells in proliferative assays, inducing a suppression as high as provoked by both CH11 mAb and recombinant human Fas ligand. Since anti-Fas were reactive to gp120, it is conceivable that antibodies binding that domain within the V3 region are effective cross-linkers of Fas and increase apoptosis in peripheral T cells. These results suggest that autologous stimulation of the Fas pathway, rather than of lymphocytotoxic antibodies, may aggravate lymphopenia in a number of HIV-1+ subjects.
Silvestris
F
F
Department of Biomedical Sciences and Human Oncology, University of Bari, Italy.
Nagata
S
S
Cafforio
P
P
Silvestris
N
N
Dammacco
F
F
D000163:Acquired Immunodeficiency Syndrome / Q000276:immunology*; D000595:Amino Acid Sequence; D000818:Animals; D000911:Antibodies, Monoclonal; D017209:Apoptosis; D001666:Binding Sites, Antibody; D002460:Cell Line; D019084:Fluorescent Antibody Technique, Indirect; D015483:HIV Antibodies / Q000276:immunology*; D015699:HIV Envelope Protein gp120 / Q000737:chemistry* / Q000276:immunology*; D015497:HIV-1 / Q000276:immunology*; D006801:Humans; D008223:Lymphoma; D051379:Mice; D017433:Protein Structure, Secondary; D011993:Recombinant Fusion Proteins / Q000737:chemistry / Q000276:immunology; D011994:Recombinant Proteins / Q000737:chemistry / Q000276:immunology; D013601:T-Lymphocytes / Q000276:immunology*; D014162:Transfection; D019014:fas Receptor / Q000737:chemistry / Q000276:immunology*
D000911:Antibodies, Monoclonal; D015483:HIV Antibodies; D015699:HIV Envelope Protein gp120; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; D019014:fas Receptor