Granzyme B is an essential mediator in CD8+ T cell killing of Theileria parva-infected cells

Journal article

There is established evidence that cytotoxic CD8+ T cells are important mediators of immunity against the bovine intracellular protozoan parasite Theileria parva. However, the mechanism by which the specific CD8+ T cells kill parasitized cells is not understood. Although the predominant pathway used by human and murine CD8+ T cells to kill pathogen-infected cells is granule exocytosis, involving the release of perforin and granzyme B, there is to date a lack of published information on the biological activities of bovine granzyme B. The present study set out to define the functional activities of bovine granzyme B and determine its role in mediating the killing of T. parva-parasitized cells. DNA constructs encoding functional and nonfunctional forms of bovine granzyme B were produced, and the proteins expressed in Cos-7 cells were used to establish an enzymatic assay to detect and quantify the expression of functional granzyme B protein. Using this assay, the levels of killing of different T. parva-specific CD8+ T cell clones were found to be significantly correlated with the levels of granzyme B protein but not the levels of mRNA transcript expression. Experiments using inhibitors specific for perforin and granzyme B confirmed that CD8+ T cell killing of parasitized cells is dependent on granule exocytosis and, specifically, granzyme B. Further studies showed that the granzyme B-mediated death of parasitized cells is independent of caspases and that granzyme B activates the proapoptotic molecule Bid.

Authors: Yang, J; Pemberton, A; Morrison, WI; Connelley, T

• Publication status: Published
• Peer review status: Peer reviewed
• Publisher: American Society for Microbiology
• Journal: Infection and Immunity
• Volume: 87
• Issue: 1
• Article number: e00386-18
• Publication date: 2018-12-19
• Acceptance date: 2018-09-14
• DOI: 10.1128/IAI.00386-18
• EISSN: 1098-5522
• ISSN: 0019-9567
• Language: English
• Keywords: theileriasis; cattle diseases; substrate specificity; cytotoxicity; granzymes; cd8-positive t-lymphocytes; t cells; granzyme b; cell survival; cytotoxins; cells; cultured; theileria parva