Increased Cytotoxic CD4+ T Cells with Reduced Cytotoxic Gene Profile Expression in Cytomegalovirus Reactivated Kidney Transplant Patients

Cytotoxic CD4+ T cells eliminate human cytomegalovirus (HCMV)-infected cells through direct cytotoxic granules exocytosis. We aimed to evaluate the functional cytotoxic gene profile of CD4+ T cells alongside the frequency of the cytotoxic phenotype in renal transplant recipients with cytomegalovirus reactivation. Blood samples were collected from twenty renal recipients with and without HCMV reactivation (HCMV+ and HCMV- groups) and ten healthy adults (control group). CD4+ T cells were isolated to assess the frequency of cytotoxic CD4+ T cells via CD107a surface staining using flow cytometry and to evaluate gene expression of perforin, granzyme B, Runt-related transcription factor 3 (RUNX3), and Eomesodermin (Eomes) by quantitative PCR. The frequency of CD4+ CD107a+ T cells was higher in the HCMV+ group compared to the HCMV- group and significantly higher than in the control group (22.69 ± 3.47 vs 16.41 ± 2.24 and 11.60 ± 1.17, respectively). Perforin gene levels were reduced in the HCMV+ group compared to the other two groups, while granzyme B gene levels were similar between HCMV+ and HCMV- groups but lower than in the control group (0.63 ± 1.24 vs 0.67 ± 2.27 and 1.00 ± 0.00, respectively). This study demonstrated an increased frequency of cytotoxic CD4+ T cells with potentially reduced functionality in kidney transplant patients with HCMV infection. It also suggests that these cells might employ other mechanisms, such as death receptor-mediated killing, or the production of other granules.