Specific Immunity to Cytomegalovirus in Pediatric Cardiac Transplantation

ABSTRACTBackgroundCytomegalovirus (CMV) infection is implicated in endothelial dysfunction and graft damage after pediatric heart transplantation. CMV specific immune responses are thought to be necessary for CMV viral control but there is little data in pediatric heart transplantation.MethodsWe studied 28 consecutive pediatric heart transplant recipients for 1-year posttransplant. CMV-specific T cells expressing IFN-γ, TNF-α and IL-2 in response to ex-vivo stimulation with CMV lysates or peptides were measured. Circulating cytokines were measured in plasma. Generalised Additive Models were applied to the data to model changes of cell population dynamics over time.ResultsCMV-specific T cell mediated responses were impaired in the first 8 weeks posttransplant. During this period, 25% of patients had CMV viremia, of which those with viral loads ≥10,000 CMV DNA copies/mL were given ganciclovir. In this group, the frequency of CD4+ and CD8+ T cells producing IFN-γ and the CD8+CD57+GB+ T cell population increased at 12-24 weeks and remained elevated for the duration of the study.ConclusionsWe have shown that CMV viremia is associated with CMV specific immune responses and increased CD8+CD57+GB+ cells at 1-year posttransplant, however early responses were not predictive of impending CMV viremia. It remains to be seen if the early CMV immune response detected is associated with endothelial and allograft damage, in light of previous studies demonstrating increased vasculopathy in pediatric patients with CMV viremia. Background Cytomegalovirus (CMV) infection is implicated in endothelial dysfunction and graft damage after pediatric heart transplantation. CMV specific immune responses are thought to be necessary for CMV viral control but there is little data in pediatric heart transplantation. Methods We studied 28 consecutive pediatric heart transplant recipients for 1-year posttransplant. CMV-specific T cells expressing IFN-γ, TNF-α and IL-2 in response to ex-vivo stimulation with CMV lysates or peptides were measured. Circulating cytokines were measured in plasma. Generalised Additive Models were applied to the data to model changes of cell population dynamics over time. Results CMV-specific T cell mediated responses were impaired in the first 8 weeks posttransplant. During this period, 25% of patients had CMV viremia, of which those with viral loads ≥10,000 CMV DNA copies/mL were given ganciclovir. In this group, the frequency of CD4+ and CD8+ T cells producing IFN-γ and the CD8+CD57+GB+ T cell population increased at 12-24 weeks and remained elevated for the duration of the study. Conclusions We have shown that CMV viremia is associated with CMV specific immune responses and increased CD8+CD57+GB+ cells at 1-year posttransplant, however early responses were not predictive of impending CMV viremia. It remains to be seen if the early CMV immune response detected is associated with endothelial and allograft damage, in light of previous studies demonstrating increased vasculopathy in pediatric patients with CMV viremia. M.C. Jacobsen and M.D.I. Manunta contributed equally to this work Correspondence: E-mail: Marianne.Jacobsen@uregina.ca; Tel: (+1) 306-585-4145; Fax (+1) 306-337-2409; Address: Department of Biology, Laboratory Building, LB244, University of Regina, 3737 Wascana Parkway, Regina, Saskatchewan, S4S 0A2, Canada. Authorship MCJ and MDIM participated in the performance of the research, data analysis, result interpretation, and in the writing of the paper. ESP and MF participated in patient consent and sample acquisition, result interpretation and in writing the paper. GLS participated in data analysis and writing the paper. NJK participated in research design, result interpretation, and writing the paper. MB participated in research design, patient consent and sample collection, result interpretation and writing the paper. DISCLOSURE: The authors have no financial relationships to disclose. Funding: Authors are grateful to the Heart for Kids Charity for funding. Copyright © 2018 Wolters Kluwer Health, Inc. All rights reserved.

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