Developing Understanding of CMI. Dr Tom Wilkinson Associate Professor of Respiratory Medicine Faculty of Medicine University of Southampton UK

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1 Pre-existing influenza-specific CD4+ T cells correlate with homologous and heterotypic response and disease protection against influenza challenge in humans Do At Risk Groups Rely more on CMI to Viruses? TIV efficacy sub- optimal in elderly and particularly patients with chronic lung disease Distribution of protective antibody abnormal in COPD lung Predominance of T cells in mucosa correlates with deficiency in antibody distribution Dr Tom Wilkinson Associate Professor of Respiratory Medicine Faculty of Medicine University of Southampton UK Polosukhin AJRCCM 2011 CTL protects against flu infection (McMichael 1983) Challenge with H1N1 Developing Understanding of CMI CTL and antibody CTL without antibody Open circles, born before 1957 Closed circles, born after 1957 (probably exposed to H3N2 only) 1

2 Quarantined Human Challenge Studies in the UK Human Viral Challenge Models Key Questions Question- do we know the cellular immune correlates of protection against influenza in man? What is the evidence for the role of CD8+ s as key effectors of CMI? What are the drivers to variable disease severity ( in a seronegative population)? Could answering these questions lead us to a novel approach to vaccine design? Study design 2 Challenge Cohorts of healthy volunteers Seronegative to challenge virus 1. Initial H3N2 n=17 (1 drop out) (14 infected ) 2. Subsequent H1N1 n=24 (9 infected) 2 Day run in 7 day quarantine Day 28 FU Oseltamivir 2

3 CD38 CD8 CD4 Laboratory Methods- ELISPOT T Cell IFN-y Assays Clinical Study Results PBMC at baseline (day -1), day 7 and day 28 CD8-MHC1-9 and 10mers CD4- MHC2- Open ended binding groove eluted peptides aa T cells separated and stimulated using a pan-influenza genome peptide stimulation matrix and ELISPOT interferon- assay. 18 mers c 10 overlapping MHC agnostic T cell Responses by Flu Protein IFNy Response T cell kinetics R=0.9 p= H3N2 Day -2 Day 7 Day 28 H1N1 CD4 Ki67 CD Day 3

4 H3N2 Pre- existing memory T cells and illness measures Total T cells CD4 (NP+M) H1N1 n=9 R= P= R= P=0.0209* Total T cells R= P=0.0369* CD4 (NP+M) R= P=0.0433* R= P= R= P=0.047* R= P= R= P= R= P=0.0318* R= P=0.0008* CD4 Cytotoxic Activity CD4 Targets? MHC Class II Expression on Respiratory Epithelium Autologous target cell killing EBV B cell line 4

5 Summary and Limitations The human challenge model provides a tool for mechanistic discovery The model Nasal infection with demonstrable systemic symptoms High doses of inoculum (PCR ve at 24hours) GMP strain Detailed mechanistic and kinetic studies Pre-existing T cell memory plays a role in limiting influenza severity in sero-negative individuals T cells targeted against core flu proteins mediate this response Clinic effects are driven by CD4 cells in this model CD4 cells mediating protective responses have cytotoxic characteristics Epitope mapping of protective responses may aid vaccine development Next challenge: Mucosal ( nasal and pulmonary correlates of protection)- human experimental model approach key Acknowledgements Dr Karl Staples Dr Ben Nicholas Professor John Oxford Dr Rob Lambkin Williams Dr Anthony Gilbert Professor Andrew McMichael & Xiaoning Xu Chris Li CD4 T Cells a Fresh look Nature Med Commentary 5