Airway-resident T cells from unexposed individuals cross-recognize SARS-CoV-2

Abstract

T cells can contribute to clearance of respiratory viruses that cause acute-resolving infections such as SARS-CoV-2, helping to provide long-lived protection against disease. Recent studies have suggested an additional role for T cells in resisting overt infection: pre-existing cross-reactive responses were preferentially enriched in healthcare workers who had abortive infections1, and in household contacts protected from infection2. We hypothesize that such early viral control would require pre-existing cross-reactive memory T cells already resident at the site of infection; such airway-resident responses have been shown to be critical for mediating protection after intranasal vaccination in a murine model of SARS-CoV3. Bronchoalveolar lavage samples from the lower respiratory tract of healthy donors obtained before the COVID-19 pandemic revealed airway-resident, SARS-CoV-2-cross-reactive T cells, which correlated with the strength of human seasonal coronavirus immunity. We therefore demonstrate the potential to harness functional airway-resident SARS-CoV-2-reactive T cells in next-generation mucosal vaccines.

Long-term respiratory mucosal immune memory to SARS-CoV-2 after infection and vaccination

“…As expected, the frequencies of circulating N-and M-speci c CD4 + and CD8 + T cells were signi cantly higher than in pre-pandemics only in the hybrid immunity group, as those vaccinees had a past SARS-CoV-2 infection (Figure 4A and 4B). In the case of RTC-speci c T cells, their frequency did not differ amongst groups, as SARS-CoV-2 cross-reactive CD4 + and CD8 + T cell responses were detected systemically in 3 out 8 pre-pandemic controls, in line with previous studies 14,40,46 . In BAL samples, the frequency of the aforementioned T cell speci cities was tested in a subset of pre-pandemic and infected, vaccinated individuals based on cell number availability.…”

“…Activation-induced markers (AIM) T cell assay Mononuclear BAL cells (1 x 10 5 cells per well) and PBMCs (1 x 10 6 cells per well) were seeded in 96-well plates in RPMI supplemented with 1% PNS and 10% AB human serum (Merck, UK) and stimulated with SARS-CoV-2 speci c peptides pools. The peptides pools used were spanning the whole Spike protein based on predicted epitopes (15-mer peptides overlapping by 10 amino acids) 64 or overlapping peptides spanning the immunogenic domains of the SARS-CoV-2 N (Prot_N) and M (Prot_M) purchased from Miltenyi Biotec 63 or combined pools spanning SARS-CoV-2 NSP7, NSP12 and NSP13 proteins (15-mer peptides overlapping by 10 amino acids) of the ancestral SARS-CoV-2 strain 14,65 . Prior to the peptide addition, cells were blocked with 0.5µg/ml of anti-CD40 mAb (Miltenyi Biotec) for 15min at 37 o C. A stimulation with an equimolar amount of DMSO was performed as a negative control and Staphylococcal enterotoxin B (SEB, 2 µg/mL) was included as a positive control.…”

Long-term respiratory mucosal immune memory to SARS-CoV-2 after infection and vaccination

“…Most of the human studies have assessed antibody and T cell responses to SARS-CoV-2 in blood, which is often not reflective of the responses in the airways. However, we and others have demonstrated the presence of pre-existing T cells that recognize SARS-CoV-2 in the lower airways or oropharyngeal lymphoid tissue of unexposed individuals respectively 14, 15 , likely induced by seasonal coronavirus infections. Presence of SARS-CoV-2 specific T cells were also reported in human nasal 16 , lung mucosa and lung-associated lymph nodes following SARS-CoV-2 infection 17,18 .…”

“…Mononuclear BAL cells (1 x 10 5 cells per well) and PBMCs (1 x 10 6 cells per well) were seeded in 96-well plates in RPMI supplemented with 1% PNS and 10% AB human serum (Merck, UK) and stimulated with SARS-CoV-2 specific peptides pools. The peptides pools used were spanning the whole Spike protein based on predicted epitopes (15-mer peptides overlapping by 10 amino acids) 64 or overlapping peptides spanning the immunogenic domains of the SARS-CoV-2 N (Prot_N) and M (Prot_M) purchased from Miltenyi Biotec 63 or combined pools spanning SARS-CoV-2 NSP7, NSP12 and NSP13 proteins (15-mer peptides overlapping by 10 amino acids) of the ancestral SARS-CoV-2 strain 14,65 . Prior to the peptide addition, cells were blocked with 0.5μg/ml of anti-CD40 mAb (Miltenyi Biotec) for 15min at 37 o C. A stimulation with an equimolar amount of DMSO was performed as a negative control and Staphylococcal enterotoxin B (SEB, 2 μg/mL) was included as a positive control.…”

Primary ChAdOx1 vaccination does not reactivate pre-existing, cross-reactive immunity

“…These are responsible for normal colds and, accordingly, ubiquitous cellular immunity to endemic coronaviruses (26-28). We and others could demonstrate that hCoV induced pre-existing pan-coronavirus-reactive immunity provides rapidly responding CD4 + and CD8 + T cells in blood and mucosa upon SARS-CoV-2 infection or COVID-19 vaccination (29)(30)(31)(32)(33)(34). Within spike, due to homology, cross-reactivity focuses on the S2 subunit.…”