Antibody-Dependent Cellular Cytotoxicity against Primary HIV- Infected CD4 T Cells Is Directly Associated with the Magnitude of

Antibody (Ab)-dependent cellular cytotoxicity (ADCC) is thought to potentially play a role in vaccine-induced protection from HIV-1. The characteristics of such antibodies remain incompletely understood. Furthermore, correlates between ADCC and HIV-1 immune status are not clearly defined.We screened the sera of 20 HIV-1-positive (HIV-1) patients for ADCC. Normal human peripheral bloodmononuclear cells were used to derive HIV-infected CD4 T cell targets and autologous, freshly iso-lated, natural killer (NK) cells in a novel assay that measures granzyme B (GrB) and HIV-1-infected CD4 T cell elimination (ICE) by flow cytometry. We observed that complex sera mediated greater levels of ADCC than anti-HIV-1 envelope glycopro-tein (Env)-specific monoclonal antibodies and serum-mediated ADCC correlated with the amount of IgG and IgG1 bound to HIV-1-infected CD4 T cells. No correlation between ADCC and viral load, CD4 T cell count, or neutralization of HIV-1SF162 or other primary viral isolates was detected. Sera pooled from clade B HIV-1 individuals exhibited breadth in killing targets infected with HIV-1 from clades A/E, B, and C. Taken together, these data suggest that the total amount of IgG bound to an HIV-1-infected cell is an important determinant of ADCC and that polyvalent antigen-specific Abs are required for a robust ADCC response. In addition, Abs elicited by a vaccine formulated with immunogens from a single clade may generate a protectiv