Effect of pepsin treatment on the HIV envelope and core antigens

In order to clarify whether HIV-1 core and env antigens are destroyed during pepsin treatment, used previously for detecting HIV-1 core and env antibodies hidden in circulating immune complexes, purified recombinant env and core antigen preparations were treated with pepsin. Core antigen was found to be extremely sensitive to this enzyme. By contrast, the antigenicity of the purified env antigen was not destroyed and was even increased after pepsin treatment, performed under identical conditions. These findings suggest that after pepsin digestion the core-anti-core immune complexes do not reconstitute because of the loss of antigenicity of the core antigen. By contrast, the lack of binding after neutralization to the env antigen of the F(ab')2 fragment of the anti-env antibody, cleaved by pepsin from the immune complexes, is probably due to other factors.