Specific inhibition of granzyme B by parainfluenza virus type 3.

T-cell-mediated cytotoxicity is an important means of defense against viral pathogens; however, several viruses possess mechanisms to disrupt cytotoxicity, thereby allowing them to avoid immune clearance. These viruses have been shown to inhibit cytotoxicity by interfering with the capacity of T lymphocytes to specifically recognize infected cells. An alternative mechanism for virally induced cytotoxic dysfunction is identified in this report. We show that parainfluenza virus type 3, a negative-stranded RNA virus, can inhibit cytotoxicity by causing a defect in the cytotoxic effector apparatus. This defect is identified as a selective inhibition of granzyme B mRNA.