P1056 T cell responses to repeated SARS-CoV-2 vaccination and breakthrough infections in patients with inflammatory bowel disease on TNF inhibitor treatment, a prospective cohort study
Authors: Bjørlykke K H , Wolf A S , Ørbo H S , Bhandari S , Solum G , Kjønstad I F , Lund K P , Tveter A T , Sexton J , Jyssum I , Kro G B , Jahnsen J , Haavardsholm E A , Grødeland G , Provan S A , Kared H , Lund-Johansen F , Munthe L A , Syversen S W , Goll G L , Mjaaland S , Jørgensen K K 
Published: January 2024

Abstract

Background
Understanding T cell responses to SARS-CoV-2 immunisation in patients on immunosuppressive treatment is important for future vaccine recommendations. Our aim was to investigate the magnitude and quality of T cell responses following repeated SARS-CoV-2 vaccine doses and COVID-19 (breakthrough infections).

Methods
In this prospective, observational study of responses to SARS-CoV-2 vaccines (Nor-vaC)1, patients with inflammatory bowel disease (IBD) on TNF inhibitor (TNFi) therapy receiving up to four SARS-CoV-2 vaccine doses, and healthy controls receiving three vaccine doses were included. CD4 and CD8 T cell responses to SARS-CoV-2 peptides were measured by flow cytometry before and 2-4 weeks following vaccination and breakthrough infection. Antibodies to the receptor binding domain (RBD) of the Wuhan-Hu-1 and BA.1 (omicron) strains were measured.

Results
Between March 2, 2021, and December 20, 2022, 118 IBD patients, and 21 healthy controls were included in the study (Table). Following three vaccine doses, the humoral immune response was attenuated in IBD patients compared to healthy controls (median 3954 BAU/ml vs. 6280 BAU/ml, p=0.008). However, both the percentage of spike-specific T cells (CD4 median 0.11% vs. 0.10%, p=0.259, CD8 0.030% vs. 0.046%, p=0,333) and T cell polyfunctionality scores (a measure of quality of vaccine response) (CD4 median 0.403 vs. 0.371, p=0.386, CD8 0.105 vs. 0.101, p=0.871), showed comparable quality in IBD patients and controls following three doses. CD4 T cell responses increased rapidly and plateaued after two vaccine doses whereas CD8 T cell responses continued to improve up to four vaccine doses (Figure). Breakthrough infection in patients following the third or fourth vaccine dose increased CD8 polyfunctionality and generated broad CD4 and CD8 T cell responses against non-spike peptides. There was no difference in T cell responses between patients using TNFi mono- and combo therapy after primary vaccination (three vaccine doses) (p=0.648).

Conclusion
Despite attenuated antibody responses, IBD patients on TNFi treatment demonstrated T cell responses comparable to healthy controls following three SARS-CoV-2 vaccine doses. Repeated vaccination and breakthrough infection increased the quality and breadth of T cell responses, reaching a plateau. Distinguishing between CD4 and CD8 immune compartments and dynamics of activation after SARS-CoV-2 immunisation may provide nuanced understanding of protective cellular responses The study results indicate that IBD patients on TNFi treatment may in future follow the same recommendations for further SARS-CoV-2 vaccines as the general population.
1Clinialtrials.gov NCT04798625