Violin plots showing a lower cellular CMV-specific immune response in patients treated with letermovir 3 months following hematopoeitic stem cell transplant

Combinatorial polyfunctionality analysis of antigen specific T-cell subsets (COMPASS) generated CD4+ and CD8+ polyfunctionality scores (PFS) following stimulation with CMV IE-1 or pp65 overlapping libraries. Immunity measured approximately 3 months post HCT in letermovir recipients vs. controls who received preemptive therapy. Cytomegalovirus-specific T-cell Reconstitution following Letermovir Prophylaxis after Hematopoeitic Cell Transplantation. Blood 138(1):34-43, 2021

CMV (Cytomegalovirus) is a ubiquitous human herpes virus that causes adverse clinical outcomes in immunocompromised individuals, such as hematopoietic cell transplant (HCT) and solid organ transplant (SOT) recipients and those infected with human immunodeficiency virus (HIV). CMV infection is the most frequent viral complication after HCT, and current strategies using either preemptive or prophylactic antivirals have not eliminated CMV complications. CMV reactivation is also common in immunocompetent adults with critical illness, and is associated with complications including prolonged mechanical ventilation and increased duration of ICU admission and hospitalization.

Our research in immunocompromised patients takes a multifaceted approach to identifying epidemiologic risk factors for CMV infection, defining viral kinetics, and improving prevention, diagnosis and treatment strategies. Our lab has experience using multiple advanced laboratory methodologies to assess CMV-specific immune responses in immunocompetent and immunocompromised hosts. We use multiparameter flow cytometry to measure monofunctional and polyfunctional T-cell responses on a population level in response to stimulation by individual CMV antigens and peptide libraries. Our results help us to identify key differences in immune reconstitution patterns after hematopoietic cell transplantation, especially in the context of modern antiviral prophylaxis and immunosuppression strategies. We also employ more sophisticated methods that can characterize T-cell subsets clustered according to their transcriptional profile (i.e., transcriptomics) thus allowing us to measure virus-specific T-cell phenotypes at the single-cell level. Historically, CMV-specific humoral immunity was previously believed unimportant in the control of CMV infection, however, recent studies have challenged this notion. To assess pathogen-specific antibody responses, our lab has developed multiple assays that can test the capacity of immune serum to neutralize cell-free CMV and to inhibit cell-to-cell spread. We also characterize antibody responses in-depth and at the epitope level using VirScan, using phage immunoprecipitation sequencing (PhIP-Seq) technology to simultaneously detect pathogen-specific antibody epitopes to hundreds of clinically relevant pathogens, including against CMV. The ability to discriminate and integrate the combination of CMV-specific cellular and humoral immune responses in the protection against CMV could be important for designing useful predictive models or risk scores for the prediction of CMV after hematopoietic stem cell transplantation.

Recent studies by our group in this area have demonstrated the superiority of preemptive therapy over prophylaxis for preventing CMV disease in CMV-seronegative recipients of liver transplants from seropositive donors, and have shown that letermovir prophylaxis after HCT delays CMV-specific immune reconstitution. We also seek to increase the speed and efficacy of clinical trials, and toward this goal we recently helped to establish CMV viral load kinetics as a surrogate endpoint for CMV disease in HCT recipients. An additional area of focus is improved diagnostics — in an ongoing trial, we are assessing self-collection of dried blood spots as a strategy to make weekly CMV testing more feasible at late time points after HCT. Within the immunocompetent patient population, our group recently found that antiviral prophylaxis directed at CMV increases ventilator-free days in patients with sepsis-associated respiratory failure, and these results are the basis for an ongoing large randomized phase 3 trial.