Deep Profiling of the CD8+ T cell Compartment identifies Activated cell subsets and Multifunctional Responses Associated with Control of Cytomegalovirus Viremia

Background Human cytomegalovirus (HCMV) is a common opportunistic pathogen in transplant recipients. Patterns of viremia and reactivation are influenced by the host immune response, including CD8+ T cells. However, the cellular deficits or phenotypic differences that account for differential outcomes during HCMV viremia are incompletely understood. Methods PBMCs were collected from 20 transplant recipients (10 viremia controllers and 10 noncontrollers) at onset of HCMV viremia and 4-weeks post. We utilized mass cytometry to perform in-depth characterization of cell-surface and intracellular CD8+ T cell markers and to compare frequencies of these cells between groups. Results Deep profiling identified 2 TCM subsets at onset and 5 TEMRA subsets at 4 weeks that were associated with control of HCMV viremia, in addition to 6 TEMRA subsets at onset and 4 weeks associated with relapsing or remitting HCMV viremia. In general, CD8+ T cell clusters associated with poorly controlled HCMV viremia lacked markers of activation or terminal differentiation including CD38, CD69, CD25, CD57 and HLA-DR. We also measured the production of 8 HCMV-specific effector molecules (TNFα, IFNγ, IL2, granzyme B, perforin, MIP1β, IL10 and CD107a) in CD8+ T cells. Viremia controllers had greater diversity of HCMV-specific multi-functional responses at both time points, including significantly higher frequencies of HCMV-specific TNFα+IFNγ+ CD8+ T cells at onset. These multifunctional cells had a phenotype consistent with activated TEM/TEMRA cells. Conclusions Uncontrolled CMV viremia is associated with specific clusters of memory T cell subsets and lower frequencies of HCMV-specific multifunctional CD8+ T cells. *Indicates joint senior authorship. Corresponding Author: Atul Humar MD MSc FRCPC, PMB 11-175, 585 University Avenue, Toronto, Canada M5G 2N2; tel: (416) 340-4241; fax (416) 340-4043; email: atul.humar@uhn.ca AUTHORSHIP PAGE Authors: Victor H. Ferreira – victor.ferreira@uhnresearch.ca Deepali Kumar – deepali.kumar@uhn.ca Atul Humar – atul.humar@uhn.ca Author Contributions: V.H.F. - participated in performance of the research, data analysis, and writing of the paper. D.K. – participated in research design, data interpretation, data collection, and writing of the paper. A.H. – participated in research design, data interpretation, data collection, and writing of the paper. Disclosure: A.H. has received a research grant from Roche and Qiagen, consulting fees from Astellas and Chimerix. D.K. has received research grants from Roche, Qiagen and Oxford Immunotec and consulting fees from Qiagen and Oxford Immunotec. Funding: This study was funded by the Canadian National Transplant Research Program (CNTRP). Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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