# Evolution of SARS-CoV-2 antibody repertoire after successive mRNA vaccinations under immunosuppressive treatment

## TL;DR

This study examines how repeated mRNA vaccinations affect the antibody response to SARS-CoV-2 in patients with immune diseases and different treatments.

## Contribution

The study reveals how immunosuppressive treatments influence the evolution of the antibody repertoire after successive vaccinations.

## Key findings

- Emerging anti-BA.1 RBD reactivity was observed over time, especially after a third vaccination.
- Affinity maturation partially explains the increased cross-reactivity between variants.
- Anti-CD20 therapy, but not MTX or TNFi, alters the antibody repertoire evolution.

## Abstract

Repeated antigen exposure can result in a shifting antibody repertoire. The mechanisms by which this occurs and consequences for cross-variant protection against evolving pathogens remain incompletely understood, particularly in the context of immunosuppressive treatments used in patients with immune-mediated inflammatory diseases (IMID).

To investigate this, we characterised longitudinal changes in the anti-SARS-CoV-2 antibody repertoire over the course of three SARS-CoV-2 mRNA vaccinations in patients with IMIDs treated with methotrexate (MTX) and/or tumour necrosis factor-inhibitors (TNFi), anti-CD20 monoclonal antibodies, no systemic therapy, and healthy controls (total N = 878). We determined serum antibody titres against the receptor-binding domain (RBD) of Wuhan-Hu-1 (WH1) and Omicron BA.1 spike proteins, and assessed ratios thereof between groups as a proxy for cross-reactivity.

We observe emerging anti-BA.1 RBD reactivity over time, notably following a third vaccination. This may be partly explained by affinity maturation, as evaluated by inhibition of ACE2-RBD interactions. Similar trends were seen in patients treated with MTX and/or TNFi, but not in patients on anti-CD20 therapy. SARS-CoV-2 infection prior to vaccination accelerated these effects initially while leading to comparable results after three vaccinations.

MTX and TNFi do not qualitatively alter the evolution of the antibody repertoire in response to repeated antigen exposure, whereas anti-CD20 does. These insights may help to optimise vaccination strategies for patients with immune-mediated inflammatory diseases.

This study was supported by 10.13039/501100001826ZonMw (The Netherlands Organization for Health Research and Development) and SGF (Collaborating Health Funds).