Coding joint: kappa-deleting recombination excision circle ratio and B cell activating factor level: predicting juvenile dermatomyositis rituximab response, a proof-of-concept study

Elisa Ochfeld, Victoria Hans, Wil Marin, Najah Ahsan, Gabrielle Morgan, Lauren M. Pachman, Amer Mohammad Khojah*

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

Abstract

Background: This pilot study’s primary aim was to determine if oligoclonal B cell expansion in children with Juvenile Dermatomyositis (JDM) predicts response to Rituximab therapy. We evaluated: (1) tissue B cell depletion efficacy by measuring the ratio of Coding joint (CJ) to Kappa-deleting recombination excision circle (KREC) DNA, and (2) serum BAFF level upon B cell recovery. Methods: CJ and KREC values were measured via qPCR assessment of serial PBMC stored (− 80 °C) in the CureJM Center’s BioRepository. Serum BAFF was quantitated by Mesoscale® technology. Oligoclonal B cell expansion was defined as a CJ:KREC ≥ 8 prior to Rituximab therapy. Detection of a CJ:KREC ratio ≤ 2.5 in the first sample after Rituximab was designated as adequate B cell depletion. A significant clinical response to therapy was defined as improvement in Disease Activity Score (DAS) by at least 2 points on consecutive visits within the first 12 months of therapy. Results: Six out of nine children with JDM showed oligoclonal B cell expansion prior to Rituximab (CJ:KREC ≥ 8). Of those 6 patients, 4 had evidence of effective B cell depletion after Rituximab (CJ:KREC ≤ 2.5), and all 4 of those subjects displayed a significant clinical response to Rituximab. Serum BAFF level increased in 8/9 children after Rituximab. Conclusions: In this proof-of-concept study, JDM patients with oligoclonal B cell expansion prior to Rituximab have more favorable clinical outcomes after Rituximab. We speculate: (1) B cell depletion post-Rituximab predicts JDM clinical response; (2) increased BAFF post-Rituximab may contribute to disease flare.

Original languageEnglish (US)
Article number36
JournalBMC Rheumatology
Volume6
Issue number1
DOIs
StatePublished - Dec 2022

Keywords

  • BAFF level
  • Juvenile dermatomyositis
  • KREC evaluation
  • Rituximab response

ASJC Scopus subject areas

  • Rheumatology

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