ABSTRACT
Background: Intensive immunosuppression to prevent graft rejection and GvHD leads to impaired T-cell immunity in HSCT and SOT patients. These are at high risk for infection with and reactivation of opportunistic pathogens such as CMV, EBV, HHV6, ADV and BKV, which are associated with significant morbidity and mortality. The inadequacies of conventional therapies have increased interest in T-cell immunotherapy. Here, timely T-cell donor recruitment and rapid production of antiviral T cells are required. Method(s): To improve T-cell donor recruitment, the alloCELL registry was established (www.alloCELL.org), currently recording >3,500 HLAtyped donors with extensively characterized antiviral T-cell repertoire. The registry has been extended by convalescent COVID-19 donors. The alloCELL lab established protocols to consider clinical requirements of patients at high risk or with failed conventional therapy. The manufacturing license for clinical-grade virus-specific T-cell products using Cytokine Capture System and CliniMACS Prodigy was obtained. T-cell donors are considered eligible if >=0.01% specific Interferon-gamma+ T cells are detectable. A related haploidentical or >=5/10 HLA-matched alloCELL donor is recommended if the stem cell donor is not eligible. Result(s): As of April 2022, >410 multi-/monovirus-specific T-cell products were generated for clinical applications by using overlapping peptide pools that cover the complete sequence of a viral protein. For patients in need of an unrelated third-party donor, suitable donors were found and clinical grade T-cell products were provided within 1.5 weeks after request with an HLA compatibility >=5/10. The applied T cells were monitored to determine frequency, chimerism and TCR repertoire. Patients who received antiviral donor T cells did not show severe adverse effects and in 80% of the cases, antiviral T cells were detected in blood after T-cell transfer. Of note, there is evidence that adoptive T-cell transfer induces endogenous T-cell responses. Conclusion(s): Success of antiviral T-cell transfer benefits from (i) accurate monitoring of viral load and antiviral T-cell frequencies in patients, and (ii) early and fast selection of suitable T-cell donors. Our data support clinical safety and efficacy of third-party antiviral T cells.
ABSTRACT
Background: Viral infections and reactivations (e.g. cytomegalovirus (CMV)) are a major cause of morbidity and mortality after hematopoietic stem cell transplantation (HSCT) and solid organ transplantation (SOT) and in patients with immunodeficiencies. Here, antiviral drugs are the mainstay of treatment, but they have side effects and cannot achieve complete viral clearance without prior reconstitution of functional virus-specific T cells (VSTs). Method(s): We performed serological testing and measured VST frequencies against 23 viral protein-derived peptide pools of 11 clinically relevant human viruses by Interferon-gamma (IFN-gamma) ELISpot assay in a cohort of healthy donors (n=151). Moreover, we performed in-depth immune profiling in patients actively infected with SARS-CoV-2 (n=92) and in unvaccinated, recovered COVID-19 patients (n=204) by ELISA, ELISpot, multicolor flow cytometry and multiplex analysis. Result(s): Based on serological testing, IFN-gamma ELISpot results, age and sex, we established normal ranges for VST frequencies in healthy donors for better interpretation of VST frequencies observed in immunocompromised patients. While in SARS-CoV-2 recovered patients, the antiviral immune response was characterized by a broad specificity, significantly lower T-cell responses were observed during active infection. Comparison with the previously established reference values for VST frequencies revealed an overall reduced T-cell functionality based on the lack of CMV-pp65-reactive T cells in CMV-seropositive COVID-19 patients, which was associated with an inflammatory milieu, expression of inhibitory molecules, and effector caspase activity in T cells. Conclusion(s): The established reference values are an invaluable tool for immune response assessment, therapeutic agent intensity and decision making in immunocompromised patients. Further, we provide evidence that the low T-cell response observed during SARS-CoV-2 infection is not exclusively due to lymphopenia, but rather due to checkpoint- and cell death-associated mechanisms, suggesting that these patients may benefit from SARS-CoV-2-specific T-cell therapy.