T cell cross reactivity to Omicron Wendy Burgers Catherine Riou University of Cape Town Peptide pools provided by Alba Grifoni Alex Sette Omicron Ancestral Measuring T cell escape PBMC from Al ID: 939565
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Preliminary experimental data on T cell cross - reactivity to Omicron Wendy Burgers Catherine Riou University of Cape Town Peptide pools provided by Alba Grifoni & Alex Sette Omicron Ancestral Measuring T cell escape PBMC from Alex Sigal & Khadija Khan Tested response to full Ancestral or Omicron Spike Readout: IFN - g , TNF - a and IL - 2 production Pfizer vaccinees n=16 81.2% N
on Resp (n=3) Resp (n=13) N=16 2 doses median 31 days after 2 nd dose CD4 resp only (n=4) CD4 and CD8 resp (n=9) n=13 69% 31% T cell responses to Omicron PBMC from Alex Sigal Peptide pools provided by Alba Grifoni & Alex Sette FOLD CHANGE CD4 (Omicron/Ancestral) Spike - specific cells (% CD4) p=0.005 CD4 response (n=13) Ancestral Omicron Median: 30% decrease in CD4 response (50 - 8
2%) Data by: Roanne Keeton, Catherine Riou , Wendy Burgers (University of Cape Town) PBMC from Alex Sigal ; Peptide pools provided by Alba Grifoni & Alex Sette T cell responses to Omicron in Pfizer vaccinees FOLD CHANGE CD4 (Omicron/Ancestral) Spike - specific cells (% CD4) p=0.005 CD4 response (n=13) Ancestral Omicron Median: 30% decrease in CD4 response (50 - 82%) CD8 response (
n=9) FOLD CHANGE CD8 (Omicron/Ancestral) Spike - specific cells (% CD8) Ancestral Omicron p=0.20 KO (n=3) N=6: Preservation of CD8 response to Omicron N=3: CD8 T cell response to Omicron undetectable Data by: Roanne Keeton, Catherine Riou , Wendy Burgers (University of Cape Town) PBMC from Alex Sigal ; Peptide pools provided by Alba Grifoni & Alex Sette T cell responses to Omicr
on in Pfizer vaccinees Loss of HLA binding in CD8 epitopes CD8 : ++ ++ ++ + + + VTWFH A I HV VTWFH V I SG HLA - A*68:02: IC 50 45 ➣ 8237 (4 - 19%) HLA - A*02:11: IC 50 19 ➣ 8421 (1 - 8%) G VYYHKNNK D HKNNKSWM HLA - A*03:01: IC 50 26 ➣ 42738 (SA: 6 - 18%) [30% Europeans] QL N RALTGI QL K RALTGI HLA - A*02:11: IC 50 27 ➣ 441 (1 - 8%) HLA - A*02:03: IC 50 16 ➣ 26 (2%)
[14% Asians] S375F N501Y, Y505H A S F S TFKCY A P F F TFKCY HLA - B*15:03: IC 50 25 ➣ 496 (SA: 6 - 17%) HLA - A*30:02: IC 50 44 ➣ 2760 (SA: 11 - 18%) S P RRARSVA S H RRARSVA HLA - B*07:02: IC 50 5 ➣ 2591 (SA: 8 - 14%) [30% Europeans] HLA - B*42:02: IC 50 39 ➣ 8401 (SA: 2 - 3%) Summary & Conclusion • T cell responses maintained to Omicron compared to ancestral Sp
ike in Pfizer vaccinees • Although there is a consistent decrease in the CD4 T cell response to Omicron, 70% of the response is preserved • The majority of vaccinees mounting a CD8 Spike response are unaffected by Omicron mutations, with a fraction losing their CD8 response • Infection prior to vaccination gives some advantage • JnJ vaccinees (1x and 2x) currently being te