ObjectiveTo study the effect of methotrexate (MTX) and its discontinuation on the humoral immune response after COVID-19 vaccination in patients with autoimmune rheumatic diseases (AIRD).MethodsIn this retrospective study, neutralising SARS-CoV-2 antibodies were measured after second vaccination in 64 patients with AIRD on MTX therapy, 31 of whom temporarily paused medication without a fixed regimen. The control group consisted of 21 patients with AIRD without immunosuppressive medication.ResultsPatients on MTX showed a significantly lower mean antibody response compared with patients with AIRD without immunosuppressive therapy (71.8% vs 92.4%, p<0.001). For patients taking MTX, age correlated negatively with immune response (r=−0.49; p<0.001). All nine patients with antibody levels below the cut-off were older than 60 years. Patients who held MTX during at least one vaccination showed significantly higher mean neutralising antibody levels after second vaccination, compared with patients who continued MTX therapy during both vaccinations (83.1% vs 61.2%, p=0.001). This effect was particularly pronounced in patients older than 60 years (80.8% vs 51.9%, p=0.001). The impact of the time period after vaccination was greater than of the time before vaccination with the critical cut-off being 10 days.ConclusionMTX reduces the immunogenicity of SARS-CoV-2 vaccination in an age-dependent manner. Our data further suggest that holding MTX for at least 10 days after vaccination significantly improves the antibody response in patients over 60 years of age.

Instability of simple DNA repeats has been known as a common cause of hereditary ataxias for over 20 years. Routine genetic diagnostics of these phenotypically similar diseases still rely on an iterative workflow for quantification of repeat units by PCR-based methods of limited precision. We established and validated clinical nanopore Cas9-targeted sequencing (Clin-CATS), an amplification-free method for simultaneous analysis of ten repeat loci associated with clinically overlapping hereditary ataxias. The method combines target enrichment by CRISPR/Cas9, Oxford Nanopore long-read sequencing, and a bioinformatics pipeline utilizing the tools STRIque and Megalodon for parallel detection of length, sequence, methylation, and composition of the repeat loci. Clin-CATS allowed for the precise and parallel analysis of 10 repeat loci associated with adult-onset ataxia and revealed additional parameter such as FMR1 promotor methylation and repeat sequence required for diagnosis at the same time. Using Clin-CATS we analyzed 100 clinical samples of undiagnosed ataxia patients and identified causative repeat expansions in 28 patients. Parallel repeat analysis enabled a molecular diagnosis of ataxias independent of preconceptions based on clinical presentation. Biallelic expansions within RFC1 were identified as the most frequent cause of ataxia. We characterized the RFC1 repeat composition of all patients and identified a novel repeat motif, AGGGG. Our results highlight the power of Clin-CATS as a readily expandable workflow for the in-depth analysis and diagnosis of phenotypically overlapping repeat expansion disorders.

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