Comparison of antibody-dependent cell-mediated cytotoxicity and virus neutralization by HIV-1 Env-specific monoclonal antibodies

Although antibodies to the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein have been studied extensively for their ability to block viral infectivity, little data are currently available on nonneutralizing functions of these antibodies, such as their ability to eliminate virus-infected cells by antibody-dependent cell-mediated cytotoxicity (ADCC). HIV-1 Env-specific antibodies of diverse specificities, including potent broadly neutralizing and nonneutralizing antibodies, were therefore tested for ADCC against cells infected with a lab-adapted HIV-1 isolate (HIV-1_NL4-3), a primary HIV-1 isolate (HIV-1_JR-FL), and a simian- human immunodeficiency virus (SHIV) adapted for pathogenic infection of rhesus macaques (SHIV_AD8-EO). In accordance with the sensitivity of these viruses to neutralization, HIV-1_NL4-3-infected cells were considerably more sensitive to ADCC, both in terms of the number of antibodies and magnitude of responses, than cells infected with HIV-1_JR-FL or SHIV_AD8-EO. ADCC activity generally correlated with antibody binding to Env on the surfaces of virus-infected cells and with viral neutralization; however, neutralization was not always predictive of ADCC, as instances of ADCC in the absence of detectable neutralization, and vice versa, were observed. These results reveal incomplete overlap in the specificities of antibodies that mediate these antiviral activities and provide insights into the relationship between ADCC and neutralization important for the development of antibody- based vaccines and therapies for combating HIV-1 infection.