Soluble proteolytic enzyme release by naive and HIV-infected cultured T-cells

The possible hydrolysis of leucine enkephalin was measured in the presence of cell-free supernatants obtained from naive and chronically HIV-infected immunocompetent cell lines. The data obtained indicate that, under all conditions examined, leu-enkephalin was partially degraded; its disappearance was associated with the appearance of peptides whose composition is consistent with the involvement of three enzyme classes, i.e. aminopeptidases, dipeptidylaminopeptidases and dipeptidylcarboxypeptidases. In the presence of supernatants obtained from infected cells, substrate hydrolysis was less than that measured in naive controls. This appears to result from infection-associated variations in the activity of all three enzyme classes active on the substrate, variations that were different for each class. Specifically, in unfractionated supernatants, the activity of aminopeptidases was reduced, that of dipeptidylaminopeptidase was increased, and the activity of dipeptidylcarboxypeptidases was nearly unmodified. Data obtained upon chromatographic separation of the soluble supernatants allowed for the identification of features that can be interpreted as indicating the existence of infection-associated variations in the activity of single enzymes. The sum of the data shown makes it possible to advance the hypothesis that the infection-associated modifications in the release of proteolytic enzymes may contribute to the alterations in the functionality of immunocompetent cells induced by viral infection.