Background: Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) pandemic poses an urgent need for the development of effective therapies for Coronavirus Disease 2019 (COVID-19).
Methods: We first tested SARS-CoV-2-specific T-cell (CοV-2-ST) immunity and expansion in unexposed donors, COVID-19 infected individuals (convalescent), asymptomatic PCR-positive subjects, vaccinated individuals, non-ICU hospitalized patients and ICU patients who either recovered and were discharged (ICU recovered) or had a prolonged stay and/or died (ICU critical). CoV-2-STs were generated from all types of donors and underwent phenotypic and functional assessment.
Results: We demonstrate causal relationship between the expansion of endogenous CoV-2-STs and the disease outcome; insufficient expansion of circulating CoV-2-STs, identified hospitalized patients at high-risk for an adverse outcome. CoV-2-STs with a similarly functional and non-alloreactive, albeit highly cytotoxic, profile against SARS-CoV-2 could be expanded from both convalescent and vaccinated donors generating clinical-scale, SARS-CoV-2-specific T-cell products with functional activity against both the unmutated virus and its B.1.1.7 variant. In contrast, critical COVID-19 patient-originating CoV-2-STs failed to expand, recapitulating the in vivo failure of CoV-2-specific T-cell immunity to control the infection. CoV-2-STs generated from asymptomatic PCR+ individuals presented only weak responses whereas their counterparts originating from exposed to other seasonal coronaviruses subjects failed to kill the virus, thus disempowering the hypothesis of protective cross-immunity.
Conclusions: Overall, we provide evidence on risk stratification of hospitalized COVID-19 patients and the feasibility of generating powerful CoV-2-ST products from both convalescent and vaccinated donors as an “off-the shelf” T-cell immunotherapy for high-risk patients.