Background: Cytomegalovirus (CMV) infection causes significant morbidity including allograft damage in transplant patients. Primary infection with CMV is rapidly resolved in healthy individuals; memory T cells control reactivation of latent virus. IFNg production by CD8 T cells is important for control of CMV, but additional CD8 effector functions have not been evaluated in detail in the context of immunosuppression. Polyfunctionality, or production of multiple cytokines and effector molecules, is important in the control of several chronic viral infections, including CMV, HIV and EBV. These studies were designed to assess T cell polyfunctionality longitudinally post-transplant.

Methods: Blood was obtained from cardiac and renal transplant patients pre-transplant as well as one, three, six, nine, and twelve months post-transplant. Patients were treated according to the standard of care, which included anti-viral prophylaxis and three-drug immunosuppression consisting of steroid, calcineurin inhibitor, and cell cycle inhibitor. Renal transplant patients also received induction therapy with rabbit ATG. Blood mononuclear cells were isolated and cryopreserved prior to analysis. Cells were stimulated with PMA and ionomycin or pooled libraries of CMV polypeptides IE-1 or pp65, and then stained for 16 color flow-cytometry.

Results: Polyfunctionality was defined as co-expression of IFNg, TNFa, and the degranulation marker CD107a. Our results indicate that cells expressing IFNg are more likely to be polyfunctional than monofunctional. Interestingly, expression of TNFa is more predictive of expression of a second marker. Pre-transplant, patients can be divided into three groups based on specificity: IE-1 dominant, pp65 dominant, and no dominant antigen specificity. This fine specificity is maintained over the first year post-transplant in a majority of patients. The percentage of CD8 T cells with CMV reactivity returned to pre-transplant levels by day 180 following lymphodepletion.

Conclusions: TNFa production pre-transplant can be used to predict CD8 T cell polyfunctionality toward CMV post-transplant, but not IE-1 vs pp65 specificity. These results confirm that detailed study of T cells responsive to CMV can provide insight into mechanisms to control the virus post-transplant.

CITATION INFORMATION: Higdon L, Margulies K, Maltzman J. Polyfunctionality of CD8 T Cell Responses to Cytomegalovirus in Transplant Patients. Am J Transplant. 2016;16 (suppl 3).

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