Abstract The development of reactive arthritis, a sterile inflammatory polyarthropathy that primarily affects HLA–B27 positive individuals, has been associated with previous enteric infections caused by various gram‐negative bacteria. The possibility that a common bacterial epitope triggers the disease was investigated by screening a panel of documented arthritogenic Shigella strains as well as 2 epidemic‐associated nonarthritogenic Shigella controls. A 2‐Md plasmid specific to the arthritogenic strains was identified and sequenced. The plasmid encodes a number of small peptides that could be related to the development of reactive arthritis. Within 1 of these is a stretch of 5 consecutive amino acids, inferred from the DNA sequence and contained within an open reading frame, that is homologous to amino acid residues 71–75 of the polymorphic region of the α1 domain of HLA–B27. The data indicate that there is a bacterial plasmid common to arthritogenic Shigella strains that may play a role in triggering reactive arthritis. The finding that this plasmid encodes an epitope shared with HLA–B27 suggests that molecular mimicry may play a role in the induction of this disease.
We previously reported elevated serum antibody levels to a peptide representing the HLA-B27 polymorphic region (B27 peptide) in HLA-B27(+) ankylosing spondylitis (AS) patients. A plasmid (pHS-2) isolated from arthritogenic Shigella flexneri strains had been shown to encode an amino acid sequence homologous to HLA-B27. Rabbit antibody to this sequence (pHS-2 peptide) strongly cross-reacted with B27 peptide and, to a much lesser extent, with Klebsiella nitrogenase peptide. Serum antibody levels to pHS-2 peptide were studied in 160 spondylarthropathy patients. 12 of 115 (10.4%) AS patients, 2 of 45 (4.4%) patients with Reiter's syndrome or reactive arthritis as well as 6 of 147 (4.1%) normal controls were shown to have elevated anti-pHS-2 peptide antibodies. Antibody levels to B27 and pHS-2 peptides were significantly correlated in 134 HLA-B27(+) patients (r = 0.333, P less than 0.001). 13 of 15 affinity-purified anti-B27 peptide antibodies from patients strongly cross-reacted with pHS-2 peptide, whereas only 3 weakly cross-reacted to nitrogenase peptide. Leucine appeared to be a critical residue for this cross-reaction. AS patients' anti-B27 peptide antibodies reacted with HLA-B27 transfected L cells. These results may suggest that pHS-2 peptide more efficiently "mimics" B27 peptide than does nitrogenase peptide. Involvement of pHS-2 in pathogenesis of spondylarthropathy through molecular mimicry mechanisms requires further study.
The pivotal role of CD40-CD40L interactions in systemic lupus erythematosus (SLE) pathogenesis stems from the orchestration of a range of immune and inflammatory responses involving B cells, T cells, other antigen-presenting cells, and type I interferon (IFN) production.[1,2] Dapirolizumab pegol (DZP), a polyethylene glycol-conjugated antigen-binding fragment lacking a functional Fc domain that inhibits CD40L, was associated with improvements in several measures of disease activity in the phase 2b RISE trial in SLE (NCT02804763).[3] DZP is under investigation in an ongoing phase 3 trial in patients (pts) with SLE (PHOENYCS GO; NCT04294667).
Objectives:
To conduct a post hoc pharmacodynamic analysis to explore the impact of DZP on B cell and type I IFN pathways using data from the phase 2b RISE trial.[3]
Methods:
In RISE, pts received placebo (PBO) or DZP (6/24/45 mg/kg) alongside standard of care (SOC) for 24 weeks (wks); adults with active SLE with moderate-to-severe disease manifestations receiving stable doses of SOC treatments were included in the trial.[3] Analyses focused on a subgroup of pts from RISE similar to the PHOENYCS GO population, namely those with persistent active SLE or acute worsening of SLE in the scope of frequent flaring/relapsing-remitting disease (n=131), previously identified as predictors of a lower response to SOC+PBO.[4] Results are shown for the PBO and DZP 24 mg/kg arms. RNA sequencing was performed on available blood samples at baseline, Wks 2, 4, 12, and 24 (Wks 2 and 24 only presented). Samples were not available for all pts at all timepoints. Gene expression changes were analyzed and competitive gene set analyses performed for pathways relevant to SLE immunopathology, selected from Gene Ontology Biological Processes and augmented with gene signatures that discriminate immune cell types in SLE.[5-7] Differential expression results for DZP treatment were corrected for SOC effects. Pts were also stratified post hoc by baseline type I IFN expression levels using a 4 gene type I IFN signature.[8]
Results:
DZP significantly downregulated genes related to immunoglobulin production compared with PBO, and this effect was observed as early as Wk 2 following a single dose (Figure 1A). A similar trend was observed in clinical levels of autoantibodies (anti-dsDNA), which has been previously reported.[3] Compared with PBO, DZP also significantly downregulated genes that play a critical role in B cell biology, specifically those involved in B cell-mediated immunity and B cell receptor signaling pathways (Figure 1B). At baseline, across all treatment arms, 76/120 (63.3%) pts showed a high type I IFN gene signature. In pts with high expression, DZP caused a marked and sustained inhibition of type I IFN gene signatures compared with PBO; this inhibitory effect was observed as early as Wk 2 (Figure 1C).
Conclusion:
DZP broadly suppresses B cell biology, decreasing the expression of numerous gene sets involved in B cell activation and immunoglobulin production. DZP also decreases expression of type I IFN signatures in pts with high baseline type I IFN expression. The impacts of DZP were seen as early as Wk 2 following a single dose. These findings demonstrate the potent modulatory effects of DZP in SLE immunopathology.
REFERENCES:
[1] Ramanujam M. Autoimmun Rev. 2020;19(11):102668. [2] Rönnblom L. Lupus Sci Med. 2019;6(1):e000270. [3] Furie RA. Rheumatology (Oxford). 2021;60:5397–407. [4] Askanase A. Ann Rheum Dis. 2023;82(Suppl 1):272. [5] Wu D. Nucleic Acids Res. 2012;40(17):e133. [6] Mandric I. Nat Commun. 2020;11(1):5504. [7] Gene Ontology Consortium. Nucleic Acids Res. 2021;49(D1):D325–34. [8] Felten R. Drug Des Devel Ther. 2019;13:1535–1543.
Acknowledgements:
Funded by UCB Pharma and Biogen Inc. Medical writing support provided by Costello Medical and funded by UCB Pharma and Biogen Inc.
Disclosure of Interests:
Ioana Cutcutache Shareholder of UCB Pharma, Employee of UCB Pharma, Alex S. Powlesland Former employee of UCB Pharma, Andrew Skelton Shareholder of UCB Pharma, Employee of UCB Pharma, Yunyun Sun Former employee of UCB Pharma, Matthew Page Shareholder of UCB Pharma, Employee of UCB Pharma, George Stojan Shareholder of UCB Pharma, Employee of UCB Pharma, Peter E. Lipsky Employee of AMPEL BioSolutions, LLC, Ania Skowera Shareholder of UCB Pharma, Employee of UCB Pharma, Christian Stach Shareholder of UCB Pharma, Employee of UCB Pharma.
The role of p38 mitogen-activated protein kinase in primary human T cells is incompletely understood. We analyzed in detail the role of p38 in the regulation of effector functions and differentiation of human CD4 T cells by using a p38-specific inhibitor and a dominant-negative mutant of p38. p38 was found to mediate expression of IL-10 and the Th2 cytokines IL-4, IL-5, and IL-13 in both, primary naive and memory T cells. In contrast, inhibition of p38 activity did not affect expression of the Th1 cytokines IFN-gamma and TNF induced by TCR-stimulation, but decreased IL-12-mediated IFN-gamma expression. Cytokine expression from established Th2 effector cells was also regulated by p38, however, the role of p38 was less pronounced compared to primary CD4 T cells. p38 MAPK regulated cytokine gene expression at both, the transcriptional level by activating gene transcription and the post-transcriptional level by stabilizing cytokine mRNA. As a result of the effect of p38 on IL-4 expression, p38 activity modulated differentiation of naive precursor T cells by inducing a shift of the Th1/Th2 balance toward the immuno-modulatory Th2 direction. Together, the data suggest that p38 plays a key role in human Th2 cell immune responses.
