[Masking of HIV antigen by specific antibodies in a model experiment]

An immuno-diagnostic test system of competitive EIA detecting HIV antigen in a concentration up to 1 ng/ml has been developed. Using this system, a phenomenon of binding of HIV antigen by antibody in sera from infected persons consisting in masking of antigenic determinants was demonstrated. The "undetectability" of HIV antigen in the system of competitive EIA caused by this phenomenon is considered to be a model of clearance of antigen at the excess of antibody in vitro. The experimental results are in agreement with the suggestion that repeated HIV antigenemia occurs as a result of exhaustion of specific immune responses.