IN-VITRO REDUCTION OF VIRUS INFECTIVITY BY ANTIBODY-DEPENDENT CELL-MEDIATED-IMMUNITY

Antibody-dependent cellular cytotoxicity (ADCC), an important defense against viral infections, is generally measured in Cr-51-release assay s. However, the effect of ADCC on viral burden is more relevant in viv o. An assay was developed to determine the impact of antibody and cyto toxic cells on reducing the amount of measles virus cultured from infe cted cells. Although the components of this assay are the same as thos e involved in ADCC, the endpoint is a reduction in virus infectivity r ather than cytotoxicity. The immune function measured in the assay has therefore been termed antibody-dependent cell-mediated immunity (ADCM I). Measles virus-infected Raji cells and blood mononuclear cells serv ed as target and effector cells, respectively. Effector cells were inc ubated with antibody-labeled or unlabeled target cells for 24 h, and v irus infectivity determined. Adding effector cells to unlabeled target cells reduced virus titer by 81.8%. Labeling target cells with measle s-seronegative serum had little further effect. However, labeling targ et cells with measles-seropositive serum reduced infectivity an additi onal 96.5%. By allowing serum to remain in the supernatant fluid after labeling target cells, neutralizing and cell-mediated antibody functi ons were simultaneously measured. Finally, arming cytokine-activated e ffector cells with measles-seropositive serum also reduced virus infec tivity. This novel assay provides an important tool for evaluating the anti-viral effects mediated by antibody and effector cells. (C) 1998 Elsevier Science B.V. All rights reserved.