Polyomavirus BK-Specific CD4+ T Cells Response to VP1 Stimulation in Kidney Transplant Recipients

Reactivation of Polyomavirus BK (BKPyV) is related to reduction of T cells response in kidney transplant recipients (KTRs). Here, we examined the differentiation of CD4+ T cells subsets in response to BKPyV KTRs, using the BKPyV VP1 (viral capsid protein 1) as a stimulator. We categorized our samples into three distinct groups: 1. Reactive BKPyV (BKPyV+), 2. non-reactive (BKPyV-) KTRs and 3. Healthy controls. BKPyV- KTRs and healthy controls stimulated with VP1 and BKPyV+ unstimulated with VP1. The human CD4+ T cells was stimulation with VP1-Ag. The proportion of CD4+ T lymphocytes and their various subsets, including naive T cells, central memory T cells (TCM), and effector memory T cells (TEM) was measured using flowcytometry. BKPyV- KTRs VP1+ indicated significantly lower TCM CD4+ T cells in contrast with both BKPyV+ KTRs VP1-, and healthy controls VP1+. This indicates that VP1 stimulation may reduce TCM cell levels in these patients. The percentage of TEM in the BKPyV- KTRs VP1+ group was significantly less prevalent than the BKPyV+ KTRs VP1- group. The percentage of TEM cells in BKPyV+ KTRs VP1- was significantly lower than the healthy controls VP1+. Stimulation with VP1 protein significantly increased the frequency of cytotoxic CD4+ T cells in BKPyV- KTRs VP1+ compared to BKPyV+ KTRs VP1-. The present research has shown that the VP1 stimulation of CD4+ T cells can induce cytotoxic CD4+ T cells responses that may help overcome BKPyV infection in KTRs. However, VP1 stimulation may also differentially affect TCM and TEM CD4+ T cells subsets.