Anti-CD4-binding domain antibodies complexed with HIV type 1 glycoprotein 120 inhibit CD4(+) T cell-proliferative responses to glycoprotein 120

HIV-specific CD4(+) helper T cell responses, particularly to the envelope g lycoproteins, are usually weak or absent in the majority of HIV-seropositiv e individuals. Since antibodies, by their capacity to alter antigen uptake and processing, are known to have modulatory effects on CD4(+) T cell respo nses, we investigated the effect of antibodies produced by HIV-infected ind ividuals on the CD4(+) T cell response to HIV-1 gp120, Proliferative respon ses of gp120-specific CD4(+) T cells were inhibited in the presence of eith er serum immunoglobulin from HIV-infected individuals or human monoclonal a ntibodies specific for the CD4-binding domain (CD4bd) of gp120, Human monoc lonal antibodies to other gp120 epitopes did not have the same effect. The anti-CD4bd antibodies complexed with gp120 suppressed T cell lines specific for varying gp120 epitopes but did not affect T cell proliferation to non- HIV antigens, Moreover, inhibition by the anti-CD4bd/gp120 complexes was ob served regardless of the types of antigen-presenting cells used to stimulat e the T cells. These results indicate that the presence of anti-CD4bd antib odies complexed with gp120 can strongly suppress CD4(+) helper T responses to gp120.