Autoantibody status is not associated with early treatment response to first-line methotrexate in patients with early rheumatoid arthritis.

Objectives: In RA, the relationship between autoantibody status and treatment response to MTX remains unclear. We investigated the association between autoantibody status and early remission in newly diagnosed RA patients treated with MTX using real-world data. Methods: RA-patients initially treated with MTX were selected from an international observational database (METEOR). Patients were stratified into autoantibody-positive (RF- and/or ACPA-positive) or autoantibody negative (RF- and ACPA-negative). The effect of autoantibody status on the chance of achieving remission within 3 to 6 months was analysed using Cox-proportional hazards regression. Results: Data from 1826 RA patients were available for analysis. DAS remission was achieved in 17% (318/1826). This was similar in autoantibody-positive [17% (282/1629)] and -negative patients [18% (36/197)]. Hence, autoantibody positivity was not associated with remission [hazard ratio (HR) 0.89, 95% CI 0.57, 1.38]. Similar findings were found when stratified for MTX monotherapy (HR 0.75, 95% CI 0.41, 1.37) or combination treatment (HR 0.76, 95% CI 0.37, 1.54). Good physical function (HAQ < 0.5) was achieved in 33% (530/1590) of all patients. Autoantibody-positivity was also not associated with HAQ < 0.5 (HR 1.05, 95% CI 0.71, 1.57). Conclusion: Autoantibody status is not associated with early remission in newly diagnosed RA-patients receiving MTX. This indicates that MTX is effective as an initial treatment strategy regardless of autoantibody status.

Breach of autoreactive B cell tolerance by post-translationally modified proteins.

OBJECTIVES: Over 50% of patients with rheumatoid arthritis (RA) harbour a variety of anti-modified protein antibodies (AMPA) against different post-translationally modified (PTM) proteins, including anti-carbamylated protein (anti-CarP) antibodies. At present, it is unknown how AMPA are generated and how autoreactive B cell responses against PTM proteins are induced. Here we studied whether PTM foreign antigens can breach B cell tolerance towards PTM self-proteins. METHODS: Serum reactivity towards five carbamylated proteins was determined for 160 patients with RA and 40 healthy individuals. Antibody cross-reactivity was studied by inhibition experiments. Mass spectrometry was performed to identify carbamylated self-proteins in human rheumatic joint tissue. Mice were immunised with carbamylated or non-modified (auto)antigens and analysed for autoantibody responses. RESULTS: We show that anti-CarP antibodies in RA are highly cross-reactive towards multiple carbamylated proteins, including modified self-proteins and modified non-self-proteins. Studies in mice show that anti-CarP antibody responses recognising carbamylated self-proteins are induced by immunisation with carbamylated self-proteins and by immunisation with carbamylated proteins of non-self-origin. Similar to the data observed with sera from patients with RA, the murine anti-CarP antibody response was, both at the monoclonal level and the polyclonal level, highly cross-reactive towards multiple carbamylated proteins, including carbamylated self-proteins. CONCLUSIONS: Self-reactive AMPA responses can be induced by exposure to foreign proteins containing PTM. These data show how autoreactive B cell responses against PTM self-proteins can be induced by exposure to PTM foreign proteins and provide new insights on the breach of autoreactive B cell tolerance.