Cytomegalovirus-specific Immune Reconstitution after Hematopoietic Cell Transplantation in the Era of Modern Antiviral Prophylaxis

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Project Summary/Abstract Cytomegalovirus (CMV) is one of the most important causes of infectious complications following hematopoietic cell transplantation (HCT). Letermovir is an effective antiviral and was recently approved for prophylaxis to prevent CMV reactivation after HCT. Graft-versus-host disease (GVHD) prophylaxis has advanced alongside CMV prophylaxis, but the effects of novel GVHD therapies on infectious complications and immune reconstitution patterns are unclear. Current data suggest that modern GVHD prophylaxis with post-transplantation cyclophosphamide and sirolimus may offer an immunologic advantage over traditional prophylaxis with calcineurin inhibitors. In this proposal, Dr. Zamora will prospectively examine how these GVHD prophylaxis strategies influence CMV-specific T-cell and humoral immunity after HCT, and how these immunological changes can affect overall clinical outcomes. In the first aim of this proposal, Dr. Zamora will examine the effects of viral, host, and transplantation factors, including GVHD prophylaxis, on polyfunctional CMV-specific cellular immune reconstitution. He will use advanced analytical methods to compute polyfunctional T-cell responses and compare differences in immune responses between GVHD prophylaxis regimens. Dr. Zamora will also compare the accuracy of these analytical methods, versus traditional methods of measuring polyfunctionality, in predicting late clinically significant CMV infection after HCT. Furthermore, he will study the immunologic influence of regulatory T cells on the development of polyfunctional T-cell immune reconstitution after HCT and investigate whether this may be affected by the presence or absence of CMV reactivation. Historically, humoral immunity was not felt to be important in CMV prevention after HCT; however, recent animal studies have challenged this notion. Therefore, in the second aim Dr. Zamora will characterize factors influencing functional CMV-specific humoral immune reconstitution after HCT, using state-of-the-art neutralizing antibody and cell-to-cell spread inhibition assays. He will also evaluate the kinetics of CMV-specific antibody responses at the epitope level, using a novel serological profiling technology that can detect antibody responses to thousands of pathogen epitopes (VirScan). Dr. Zamora will investigate the associations of CMV-specific humoral immunity, as measured by these novel immune platforms, with the prevention of late clinically significant CMV reactivation after HCT. Dr. Zamora aims to define CMV-specific T-cell and humoral immune reconstitution kinetics in the current era of advanced GVHD prophylaxis regimens and effective antiviral prophylaxis. This study has the potential to define immunologic parameters to optimize CMV prophylaxis strategies and provide the basis for novel immunotherapy and immune monitoring approaches.