A secretable serine proteinase with highly restricted specificity from cytolytic T lymphocytes inactivates retrovirus-associated reverse transcriptase.

TSP-1, a murine T cell specific proteinase, is expressed in cytolytic T lymphocytes and secreted upon their interaction with antigen bearing target cells. In searching for possible extracellular substrates of the enzyme in the physiological environment of cytolytic effector cells, we have investigated the proteolytic activity of TSP-1 on retroviral proteins. It is shown that reverse transcriptase derived from the retrovirus Moloney murine leukemia virus is inactivated by TSP-1 via limited proteolysis. The data suggest the possibility that cytolytic T lymphocytes are able to interfere with retroviral replication by secreting a serine proteinase which degrades viral proteins.