Adoptive transfer of ex vivo expanded SARS-CoV-2-specific cytotoxic lymphocytes: A viable strategy for COVID-19 immunosuppressed patients?

Respiratory virus infections after allogeneic stem cell transplantation: Current understanding, knowledge gaps, and recent advances

Before the COVID-19 pandemic, common community-acquired seasonal respiratory viruses (CARVs) were a significant threat to the health and well-being of allogeneic hematopoietic cell transplant (allo-HCT) recipients, often resulting in severe illness and even death. The pandemic has further highlighted the significant risk that immunosuppressed patients, including allo-HCT recipients, face when infected with SARS-CoV-2. As preventive transmission measures are relaxed and CARVs circulate again among the community, including in allo-HSCT recipients, it is crucial to understand the current state of knowledge, gaps, and recent advances regarding CARV infection in allo-HCT recipients. Urgent research is needed to identify seasonal respiratory viruses as potential drivers for future pandemics.

Potency assessment of IFNγ-producing SARS-CoV-2-specific T cells from COVID-19 convalescent subjects

The development of new therapies for COVID-19 high-risk patients remains necessary to prevent additional deaths. Here, we studied the phenotypical and functional characteristics of IFN-γ producing-SARS-CoV-2-specific T cells (SC2-STs), obtained from 12 COVID-19 convalescent donors, to determine their potency as an off-the-shelf T cell therapy product. We found that these cells present mainly an effector memory phenotype, characterized by the basal expression of cytotoxicity and activation markers, including granzyme B, perforin, CD38, and PD-1. We demonstrated that SC2-STs could be expanded and isolated in vitro, and they exhibited peptide-specific cytolytic and proliferative responses after antigenic re-challenge. Collectively, these data demonstrate that SC2-STs can be a suitable candidate for the manufacture of a T cell therapy product aimed to treat severe COVID-19.

Pathogen-specific T Cells: Targeting Old Enemies and New Invaders in Transplantation and Beyond

Adoptive immunotherapy with virus-specific cytotoxic T cells (VSTs) has evolved over the last three decades as a strategy to rapidly restore virus-specific immunity to prevent or treat viral diseases after solid organ or allogeneic hematopoietic cell-transplantation (allo-HCT). Since the early proof-of-principle studies demonstrating that seropositive donor-derived T cells, specific for the commonest pathogens post transplantation, namely cytomegalovirus or Epstein-Barr virus (EBV) and generated by time- and labor-intensive protocols, could effectively control viral infections, major breakthroughs have then streamlined the manufacturing process of pathogen-specific T cells (pSTs), broadened the breadth of target recognition to even include novel emerging pathogens and enabled off-the-shelf administration or pathogen-naive donor pST production. We herein review the journey of evolution of adoptive immunotherapy with nonengineered, natural pSTs against infections and virus-associated malignancies in the transplant setting and briefly touch upon recent achievements using pSTs outside this context.

Antigen-Specific T Cells and SARS-CoV-2 Infection: Current Approaches and Future Possibilities

COVID-19, a significant global health threat, appears to be an immune-related disease. Failure of effective immune responses in initial stages of infection may contribute to development of cytokine storm and systemic inflammation with organ damage, leading to poor clinical outcomes. Disease severity and the emergence of new SARS-CoV-2 variants highlight the need for new preventative and therapeutic strategies to protect the immunocompromised population. Available data indicate that these people may benefit from adoptive transfer of allogeneic SARS-CoV-2-specific T cells isolated from convalescent individuals. This review first provides an insight into the mechanism of cytokine storm development, as it is directly related to the exhaustion of T cell population, essential for viral clearance and long-term antiviral immunity. Next, we describe virus-specific T lymphocytes as a promising and efficient approach for the treatment and prevention of severe COVID-19. Furthermore, other potential cell-based therapies, including natural killer cells, regulatory T cells and mesenchymal stem cells are mentioned. Additionally, we discuss fast and effective ways of producing clinical-grade antigen-specific T cells which can be cryopreserved and serve as an effective "off-the-shelf" approach for rapid treatment of SARS-CoV-2 infection in case of sudden patient deterioration.

ALVR109, an off-the-shelf partially HLA matched SARS-CoV-2-specific T cell therapy, to treat refractory severe COVID-19 pneumonia in a heart transplant patient: Case report

An unvaccinated adult male heart transplant recipient patient with recalcitrant COVID-19 due to SARS-CoV-2 delta variant with rising nasopharyngeal quantitative viral load was successfully treated with ALVR109, an off-the-shelf SARS-CoV-2-specific T cell therapy. Background immunosuppression included 0.1 mg/kg prednisone, tacrolimus, and mycophenolate mofetil 1 gm twice daily for historical antibody-mediated rejection. Prior therapies included remdesivir, corticosteroids, and tocilizumab, with requirement for high-flow nasal oxygen. Lack of clinical improvement and acutely rising nasopharyngeal viral RNA more than 3 weeks into illness prompted the request of ALVR109 through an emergency IND. The day following the first ALVR109 infusion, the patient's nasopharyngeal SARS-CoV-2 RNA declined from 7.43 to 5.02 log₁₀ RNA copies/ml. On post-infusion day 4, the patient transitioned to low-flow oxygen. Two subsequent infusions of ALVR109 were administered 10 and 26 days after the first; nasopharyngeal SARS-CoV-2 RNA became undetectable on Day 11, and he was discharged the following day on low-flow oxygen 5 weeks after the initial diagnosis of COVID-19. The clinical and virologic improvements observed in this patient following administration of ALVR109 suggest a potential benefit that warrants further exploration in clinical trials.

Off-the-Shelf Partial HLA Matching SARS-CoV-2 Antigen Specific T Cell Therapy: A New Possibility for COVID-19 Treatment

Background

Immunological characteristics of COVID-19 show pathological hyperinflammation associated with lymphopenia and dysfunctional T cell responses. These features provide a rationale for restoring functional T cell immunity in COVID-19 patients by adoptive transfer of SARS-CoV-2 specific T cells.

Methods

To generate SARS-CoV-2 specific T cells, we isolated peripheral blood mononuclear cells from 7 COVID-19 recovered and 13 unexposed donors. Consequently, we stimulated cells with SARS-CoV-2 peptide mixtures covering spike, membrane and nucleocapsid proteins. Then, we culture expanded cells with IL-2 for 21 days. We assessed immunophenotypes, cytokine profiles, antigen specificity of the final cell products.

Results

Our results show that SARS-CoV-2 specific T cells could be expanded in both COVID-19 recovered and unexposed groups. Immunophenotypes were similar in both groups showing CD4+ T cell dominance, but CD8+ and CD3+CD56+ T cells were also present. Antigen specificity was determined by ELISPOT, intracellular cytokine assay, and cytotoxicity assays. One out of 14 individuals who were previously unexposed to SARS-CoV-2 failed to show antigen specificity. Moreover, ex-vivo expanded SARS-CoV-2 specific T cells mainly consisted of central and effector memory subsets with reduced alloreactivity against HLA-unmatched cells suggesting the possibility for the development of third-party partial HLA-matching products.

Discussion

In conclusion, our findings show that SARS-CoV-2 specific T cell can be readily expanded from both COVID-19 and unexposed individuals and can therefore be manufactured as a biopharmaceutical product to treat severe COVID-19 patients.

One Sentence Summary

Ex-vivo expanded SARS-CoV-2 antigen specific T cells developed as third-party partial HLA-matching products may be a promising approach for treating severe COVID-19 patients that do not respond to previous treatment options.

An overview of the recent findings of cell-based therapies for the treatment and management of COVID-19

The coronavirus disease 2019 (COVID-19) caused by the severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) has become a global pandemic taking the lives of millions. The virus itself not only invades and destroys the angiotensin-converting enzyme 2 (ACE2)-expressing cells of the lungs, kidneys, liver, etc. but also elicits a hyperinflammatory immune response, further damaging the tissue leading to acute respiratory distress syndrome (ARDS) and death. Although vaccines, as a prime example of active immunotherapy, have clearly disrupted the transmission of virus and reduced mortality, hospitalization, and burden of disease, other avenues of immunotherapy are also being explored. One such approach would be to adoptively transfer modified/unmodified immune cells to the critically ill. Here, we compiled and summarized the immunopathogenesis of SARS-CoV-2 and the recent preclinical and clinical data on the potential of cell-based therapies in the fight against COVID-19.

Adoptive transfer of ex vivo expanded SARS-CoV-2-specific cytotoxic lymphocytes: A viable strategy for COVID-19 immunosuppressed patients?

Cellular and humoral response to acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) infections is on focus of research. We evaluate herein the feasibility of expanding virus‐specific T cells (VST) against SARS‐CoV‐2 ex vivo through a standard protocol proven effective for other viruses. The experiment was performed in three different donors' scenarios: (a) SARS‐CoV‐2 asymptomatic infection/negative serology, (b) SARS‐CoV‐2 symptomatic infection/positive serology, and (c) no history of SARS‐CoV‐2 infection/negative serology. We were able to obtain an expanded VST product from donors 1 and 2 (1.6x and 1.8x increase of baseline VST count, respectively) consisting in CD3 + cells (80.3% and 62.7%, respectively) with CD4 + dominance (60% in both donors). Higher numbers of VST were obtained from the donor 2 as compared to donor 1. T‐cell clonality test showed oligoclonal reproducible peaks on a polyclonal background for both donors. In contrast, VST could be neither expanded nor primed in a donor without evidence of prior infection. This proof‐of‐concept study supports the feasibility of expanding ex vivo SARS‐CoV‐2‐specific VST from blood of convalescent donors. The results raise the question of whether the selection of seropositive donors may be a strategy to obtain cell lines enriched in their SARS‐CoV‐2‐specificity for future adoptive transfer to immunosuppressed patients.