T cell dysfunction in lung transplant COVID-19 patients
Author: Iulia Popescu
Rationale: Lymphopenia is common in severe COVID-19 disease, yet the immune mechanisms are incompletely understood. We recently demonstrated a role for TNF-a in T-cell dysfunction in severe COVID-19 disease. As inflammatory cytokines are increased in severe SARS-CoV-2 infection, we hypothesized T-cell dysfunction with acute COVID-19 disease in lung transplant recipients (LTRs) who are maintained on immunosuppression.
Objectives: We sought to characterize the functional SARS-CoV-2 T-cell responses in LTRs with COVID-19 to determine the differences between acute infection and the recovery phase (1-6 months post-infection) and whether LTRs establish SARS-CoV-2-specific T-cell memory.
Methods: Using flow cytometry analyses we assessed SARS-CoV-2-specific responses in our LTR cohort, measuring T cell phenotype and the functional responses to COVID-19 immunodominant Spike-1 antigen (S1), including proliferation capacity and cytokine production in acute and recovered samples.
Measurements/Main Results: In the COVID-19 LTRs we found CD4+ lymphopenia predominated in moderate/severe disease in acute viral samples, with lower CD4+/CD8+ ratios (p=0.0002) and absolute lymphocyte counts (ALC) (p=0.041) compared to the recovery phase 1-6 months post-infection. The CD8+ T cell phenotype of acute moderate/severe COVID-19 LTRs compared with the primary acute viral infection was significantly increased for surface expression of CD95+ (Fas) (p=0.0002), CD38+ (p=0.005) and the senescent marker, CD57+ (p=0.0007), with these activation markers decreasing post-infection. Unexpectedly, CD8+PD1+ (p=0.0002) was significantly upregulated post-infection compared with acute primary infection disease. Similar phenotypic findings were observed in CD4+ T cells. During acute SARS-Cov-2 disease, both CD8+ and CD4+ IFNg+, TNF-a+ and CD107+ T-cell frequencies in response to S1 were significantly increased, with a contraction into the memory phase. The exception was CD4+ IL-2 production which was significantly increased in the memory phase compared with the acute infection. CD4+TNF-a+ T-cell responses were dominant and inversely correlated with absolute CD4+ counts from acute COVID-19 LTR cohort. During acute infection, LTRs demonstrated impaired S1-specific T cell proliferation (CD4+>CD8+) at 6 days, along with increased susceptibility to activation-induced cell death (AICD) following S1 antigen exposure. The impaired S1-specific proliferation in LTRs from acute infection could be rescued using the anti-TNFa agent, infliximab, or exogenous IL-2. Post-infection, the majority of LTRs demonstrated robust S1-specific CD4+ T-cell proliferation and significantly decreased susceptibility to AICD following S1 exposure. However, the addition of autologous acute plasma, but not recovery phase plasma, strikingly impaired S1-specific memory T-cell proliferation and induced S1-specific AICD in recovery T- cells from LTRs COVID-19 patients. Proliferative responses could only be partially restored with anti-TNFa suggesting other mechanism(s) of TNFa-independent suppression. Current experiments are focused on defining whether viremia itself plays a role in suppressing T-cell responses. Conclusion: Together, our findings show CD4+ dysfunction in LTRs with acute COVID-19 mediated, in part, by TNF-a. Interestingly, despite immunosuppression, LTRs establish robust SAR-Co-V2-specific T-cell memory after acute infection. Our data suggests other mechanism(s) that contribute to T-cell dysfunction during acute COVID-19 that remain to be elucidated.
Short CV
I am a Associate Professor in the Division of Pulmonary, Allergy, and Critical Care Medicine at the University of Pittsburgh in Dr. John McDyer’s laboratory. I have significant experience in transplant and viral immunology. My work has focused on T cell mechanisms of rejection, tolerance, and host immunity to viruses such as CMV, EBV and HIV, including the measurement of lung mucosal responses. I have focused on CMV-specific T cell immunity in lung transplant recipients in a leading clinical transplant program. I am CO-I on a U01 award (AI125050-Dr. McDyer) to perform a novel clinical trial to perform tandem lung and bone marrow transplantation in select individuals with primary immunodeficiencies and end-stage lung disease, and to perform mechanistic pathogen-specific and alloimmune tolerance studies in these study participants. In U01AI125050 I measure systemic and lung pathogen-specific immune responses. As immunologist my focuses are on mechanisms of CMV-specific lung mucosal/systemic immunity and viral control, demonstrating an important role for the Type-1 transcription factor T-bet and other immune parameters. I also study immune mechanisms of allograft rejection/tolerance in lung transplantation with an established divisional research group performing studies in the human studies. I also perform work on Dr. McDyer and Dr. Kirks’ collaborative U01 award (HL121814) to study immune mechanisms of HIV-associated COPD. I am the Co-I on an R01 award HL133184-01 (Dr. McDyer), “Role of F-box Proteins in Lung Transplantation.” In addition, common to these experimental systems above, Dr. McDyer’s laboratory is highly proficient in measuring lung mucosal and systemic viral-specific and allospecific multifunctional T cell immunity and phenotyping in lung transplant recipients. I have a good track record of training medical students and fellows and junior faculty in Dr. McDyer’s lab. the field of lung transplant immunology. Pertinent to this proposal I also have significant experience assessing human alloimmunity, using flow cytometry, in addition to viral immunity, and evaluate the phenotype of T cells, proliferation and effector multifunction. In addition, I am very experienced in ELISA and ELISPOT assays to measure inflammatory responses. Recently, we showed that IPF lung transplant recipients with short telomeres have impaired CMV T cell immunity. Here at Pitt, Dr. Alder, Dr. Snyder, Dr. Chen, Dr. Iasella and Dr. Popescu have a track record of working closely together. Therefore, based on my established and current role in Dr. McDyer’s laboratory and my expertise in transplant immunology in the field of lung transplantation makes me well-suited to fulfill my role as Co-I on this project R01 project, “The Role of Telomeres in Lung Transplant Recipient Immunity and Outcomes”.
Positions and Employment
2020-pres. Research Associate Professor, Pulmonary, Allergy and Critical Care Division, Department Medicine, University of Pittsburgh, Pittsburgh, PA
2014-2020 Research Assistant Professor, Pulmonary, Allergy and Critical Care Division, Department Medicine, University of Pittsburgh, Pittsburgh, PA
2019-pres. Member – International Society of Heart and Lung Transplantation
2012-2014 Research Associate/Manager Flow Cytometry Core, Pulmonary, Allergy and Critical Care Division, Department Medicine, University of Pittsburgh, Pittsburgh, PA
2010-2011 Senior Scientist/Technical Application Specialist, Cellular Technology Limited, Shaker Heights, OH
2006-2010 Faculty Research Instructor, Dept of Surgery Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA
2006-pres. Member – American Society of Transplantation (AST)
2007-pres. Member – American Immunology Association (AIA)
2001-2006 Postdoctoral Research Associate, Dept of Surgery Thomas E. Starzl Transplantation Institute, University of Pittsburgh, Pittsburgh, PA
2000-2001 Research Scientist, Dept. of Cellular Immunology and Signal Transduction, Center of Immunology, Institute of Virology Bucharest, Romania
1997- 2000 Junior Research Scientist, Department Clinical Immunology, Center for Immunology, Bucharest, Romania
1998-pres. Member – European Association for Cancer Research (EACR)
1997 3 months Visiting Research PhD, Doctoral Scientist, Cancer Institute, University of Pittsburgh, Pittsburgh, PA.
1994-1997 Research Associate – Dept. of Cellular Immunology and Signal Transduction, Center of Immunology, Institute of Virology, Bucharest, Romania
1991-1994 Resident Scientist- Department Clinical Immunology, Center for Immunology, Bucharest, Romania
1986-1991 Research Assistant, Department of Interferon Research / Immune-modulators, V. Babes Institute, Bucharest, Romania
1990-pres. Member – Federation of European Biochemical Societies (FEBS)
1986-pres. Member – Romanian Society of Immunology (SNI)
Memberships
Member – American Society of Transplantation (AST) 2006-present
Member – American Immunology Association (AIA) 2007-present
Member – European Association for Cancer Research (EACR) 1998-present
Member – Federation of European Biochemical Societies (FEBS) 1990-present
Member – Romanian Society of Immunology (SNI) 1986-present
Member – International Society of Heart and Lung Transplantation 2019-present
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