The spondyloarthropathies are a group of rheumatic diseases that are associated with inflammation at anatomically distal sites, particularly the tendon-bone attachments (entheses) and the aortic root. Serum concentrations of interleukin-23 (IL-23) are elevated and polymorphisms in the IL-23 receptor are associated with ankyosing spondylitis, however, it remains unclear whether IL-23 acts locally at the enthesis or distally on circulating cell populations. We show here that IL-23 is essential in enthesitis and acts on previously unidentified IL-23 receptor (IL-23R)(+), RAR-related orphan receptor γt (ROR-γt)(+)CD3(+)CD4(-)CD8(-), stem cell antigen 1 (Sca1)(+) entheseal resident T cells. These cells allow entheses to respond to IL-23 in vitro-in the absence of further cellular recruitment--and to elaborate inflammatory mediators including IL-6, IL-17, IL-22 and chemokine (C-X-C motif) ligand 1 (CXCL1). Notably, the in vivo expression of IL-23 is sufficient to phenocopy the human disease, with the specific and characteristic development of enthesitis and entheseal new bone formation in the initial complete absence of synovitis. As in the human condition, inflammation also develops in vivo at the aortic root and valve, which are structurally similar to entheses. The presence of these entheseal resident cells and their production of IL-22, which activates signal transducer and activator of transcription 3 (STAT3)-dependent osteoblast-mediated bone remodeling, explains why dysregulation of IL-23 results in inflammation at this precise anatomical site.

IL-23 induces spondyloarthropathy by acting on ROR-γt+ CD3+CD4-CD8- entheseal resident T cells

Intervertebral disc (IVD) degeneration is an often investigated pathophysiological condition because of its implication in causing low back pain. As human material for such studies is difficult to obtain because of ethical and government regulatory restriction, animal tissue, organs and in vivo models have often been used for this purpose. However, there are many differences in cell population, tissue composition, disc and spine anatomy, development, physiology and mechanical properties, between animal species and human. Both naturally occurring and induced degenerative changes may differ significantly from those seen in humans. This paper reviews the many animal models developed for the study of IVD degeneration aetiopathogenesis and treatments thereof. In particular, the limitations and relevance of these models to the human condition are examined, and some general consensus guidelines are presented. Although animal models are invaluable to increase our understanding of disc biology, because of the differences between species, care must be taken when used to study human disc degeneration and much more effort is needed to facilitate research on human disc material.

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Are animal models useful for studying human disc disorders/degeneration?

Spondyloarthropathies are a cluster of interrelated and overlapping chronic inflammatory rheumatic diseases that primarily include ankylosing spondylitis, reactive arthritis, and the arthritis associated with psoriasis and inflammatory bowel diseases. The primary pathologic sites are the entheses (the sites of bony insertion of ligaments and tendons); the axial skeleton, including the sacroiliac joints; the limb joints; and some nonarticular structures, such as the gut, skin, eye, and aortic valve. Although spondyloarthropathies are not associated with rheumatoid factor, they show a strong association with HLA-B27; however, this association varies markedly among various spondyloarthropathies and among ethnic groups. The most widely used classification criterion, from the European Spondyloarthropathy Study Group, encompasses the currently recognized wider disease spectrum, with a sensitivity and specificity that generally exceed 85%. Spondyloarthropathies occur in genetically predisposed persons and are triggered by environmental factors, but the cellular and molecular mechanisms of inflammation are not yet fully understood. Chlamydial and many enterobacterial infections can trigger reactive arthritis, but an infectious trigger for ankylosing spondylitis has not yet been established. HLA-B27 itself is involved in enhancing genetic susceptibility, but the underlying molecular basis is still unknown; additional genes include the putative susceptibility genes for Crohn disease, ulcerative colitis, and psoriasis. A specific susceptibility gene for Crohn disease, NOD2, is located on chromosome 16q12, and one of the candidate genes for psoriasis, PSORS1, has been mapped to a 60-kb fragment on chromosome 6p, which is telomeric to the HLA-C locus. This paper reviews the efficacy of anti-tumor necrosis factor-alpha therapy and other therapeutic advances.

Update on Spondyloarthropathies

https://www.thelancet.com/pdfs/journals/lancet/PIIS0140-6736(11)60071-8.pdf

Arthritis 2 Spondyloarthritis

Objective

To determine whether HLA–B27 misfolding and the unfolded protein response (UPR) result in cytokine dysregulation and whether this is associated with Th1 and/or Th17 activation in HLA–B27/human β2-microglobulin (Huβ2m)–transgenic rats, an animal model of spondylarthritis.



Methods

Cytokine expression in lipopolysaccharide (LPS)–stimulated macrophages was analyzed in the presence and absence of a UPR induced by chemical agents or by HLA–B27 up-regulation. Cytokine expression in colon tissue and in cells purified from the lamina propria was determined by real-time reverse transcription–polymerase chain reaction analysis, and differences in Th1 and Th17 CD4+ T cell populations were quantified after intracellular cytokine staining.



Results

Interleukin-23 (IL-23) was found to be synergistically up-regulated by LPS in macrophages undergoing a UPR induced by pharmacologic agents or by HLA–B27 misfolding. IL-23 was also increased in the colon tissue from B27/Huβ2m-transgenic rats concurrently with the development of intestinal inflammation, and IL-17, a downstream target of IL-23, exhibited robust up-regulation in a similar temporal pattern. IL-23 and IL-17 transcripts were localized to CD11+ antigen-presenting cells and CD4+ T cells, respectively, from the colonic lamina propria. Colitis was associated with a 6-fold expansion of CD4+ IL-17–expressing T cells.



Conclusion

The IL-23/IL-17 axis is strongly activated in the colon of B27/Huβ2m-transgenic rats with spondylarthritis-like disease. HLA–B27 misfolding and UPR activation in macrophages can result in enhanced induction of the pro-Th17 cytokine IL-23. These results suggest a possible link between HLA–B27 misfolding and immune dysregulation in this animal model, with implications for human disease.

HLA-B27 misfolding and the unfolded protein response augment interleukin-23 production and are associated with Th17 activation in transgenic rats.

HLA-B27 is a human major histocompatibility complex (MHC) class I allele that is found with strikingly increased prevalence in patients with the spondyloarthropathies, a group of disorders that includes ankylosing spondylitis, reactive arthritis (formerly commonly referred to as Reiter’s syndrome), arthritis and spondylitis associated with inflammatory bowel disease or psoriasis, as well as a more general diagnosis of spondyloarthropathy that shares features of the other entities (1–3). Some of these disorders are known to be directly triggered by infectious agents, and microbial agents have been implicated in most of the rest of these disorders as well. A thorough elucidation of the basis for the association between B27 and disease would enhance our understanding of the roles that both genes and environmental agents play in producing chronic inflammatory diseases.

Inflammatory disease in HLA-B27 transgenic rats

The class I MHC allele HLA-B27 is highly associated with the human spondyloarthropathies, but the basis for this association remains poorly understood. Transgenic rats with high expression of HLA-B27 develop a multisystem inflammatory disease that includes arthritis and colitis. To investigate whether CD8alphabeta T cells are needed in this disease, we depleted these cells in B27 transgenic rats before the onset of disease by adult thymectomy plus short-term anti-CD8alpha mAb treatment. This treatment induced profound, sustained depletion of CD8alphabeta T cells, but failed to suppress either colitis or arthritis. To address the role of CD8alpha(+)beta(-) cells, we studied four additional groups of B27 transgenic rats treated with: 1) continuous anti-CD8alpha mAb, 2) continuous isotype-matched control mAb, 3) the thymectomy/pulse anti-CD8alpha regimen, or 4) no treatment. Arthritis occurred in approximately 40% of each group, but was most significantly reduced in severity in the anti-CD8alpha-treated group. In addition to CD8alphabeta T cells, two sizeable CD8alpha(+)beta(-) non-T cell populations were also reduced by the anti-CD8alpha treatment: 1) NK cells, and 2) a CD4(+)CD8(+)CD11b/c(+)CD161a(+)CD172a(+) monocyte population that became expanded in diseased B27 transgenic rats. These data indicate that HLA-B27-retricted CD8(+) T cells are unlikely to serve as effector cells in the transgenic rat model of HLA-B27-associated disease, in opposition to a commonly invoked hypothesis concerning the role of B27 in the spondyloarthropathies. The data also suggest that one or more populations of CD8alpha(+)beta(-) non-T cells may play a role in the arthritis that occurs in these rats.

CD8αβ T Cells Are Not Essential to the Pathogenesis of Arthritis or Colitis in HLA-B27 Transgenic Rats

AIMS
To evaluate pharmacokinetics (PK) and safety after coadministration of nirmatrelvir/ritonavir or ritonavir alone with midazolam (a cytochrome P450 [CYP3A4] 3A4 substrate) and dabigatran (a P-glycoprotein [P-gp] substrate).


METHODS
Pharmacokinetics were studied in two phase 1, open-label, fixed-sequence studies in healthy adults. Single oral doses of midazolam 2 mg (n=12) or dabigatran 75 mg (n=24) were administered alone and after steady-state (ie, ≥2 days) of nirmatrelvir/ritonavir 300 mg/100 mg and ritonavir 100 mg. Midazolam and dabigatran plasma concentrations and adverse events (AEs) were analyzed for each treatment.


RESULTS
After administration of midazolam with nirmatrelvir/ritonavir (test) or alone (reference), midazolam geometric mean AUCinf and Cmax increased 14.3-fold and 3.7-fold respectively. Midazolam co-administered with ritonavir (test) or alone (reference), resulted in 16.5-fold and 3.9-fold increases in midazolam geometric mean AUCinf and Cmax , respectively. After administration of dabigatran with nirmatrelvir/ritonavir (test) or alone (reference), dabigatran geometric mean AUCinf and Cmax increased 1.9-fold and 2.3-fold, respectively. Dabigatran coadministered with ritonavir (test) or alone (reference), resulted in a 1.7-fold increase in dabigatran geometric mean AUCinf and Cmax . Midazolam or dabigatran exposures were generally comparable when coadministered with nirmatrelvir/ritonavir or ritonavir alone, with a slightly higher dabigatran Cmax with nirmatrelvir/ritonavir vs ritonavir alone. Nirmatrelvir/ritonavir was generally safe when administered with or without midazolam or dabigatran. No serious or severe AEs were reported.


CONCLUSION
Coadministration of midazolam (a CYP3A4 substrate) or dabigatran (a P-gp substrate) with nirmatrelvir/ritonavir increased systemic exposure of midazolam or dabigatran. Midazolam exposures were comparable when coadministered with nirmatrelvir/ritonavir or ritonavir alone, suggesting no incremental effect of nirmatrelvir. Dabigatran Cmax was slightly higher when coadministered with nirmatrelvir/ritonavir compared with of ritonavir alone suggesting a minor incremental effect of nirmatrelvir.


CLINICALTRIALS
gov NCT05032950, NCT05064800.

Effects of Nirmatrelvir/Ritonavir on Midazolam and Dabigatran Pharmacokinetics in Healthy Participants.

Objectives This exploratory analysis investigated the potential use of the multibiomarker disease activity (MBDA) score to support biosimilarity assessments using data from two randomised controlled trials (RCTs) of biosimilar infliximab (IFX-qbtx) and biosimilar adalimumab (ADL-afzb) versus EU-sourced infliximab (Remicade; IFX-EU) and adalimumab (Humira; ADL-EU) reference products, respectively, both conducted in adult patients with active rheumatoid arthritis. Methods In one study, patients (N=650) were randomised 1:1 to IFX-qbtx or IFX-EU (3 mg/kg intravenous at weeks 0, 2 and 6, then every 8 weeks). In the other, patients (N=597) were randomised 1:1 to ADL-afzb or ADL-EU (40 mg subcutaneous every other week). All treatments were given with MTX. Mean values of MBDA scores were calculated at baseline (BL), based on the concentrations of 12 serum proteins using the Vectra disease activity algorithm, and at timepoints throughout treatment period 1 (TP1) of the IFX (weeks 6, 14, 30) and ADL (weeks 6, 12, 26) studies. Data were summarised using descriptive statistics for the intent-to-treat population, without imputation for missing data. Results At BL, mean (±SD) MBDA scores were 61.3 (±12.5) and 58.8 (±13.2) for IFX-qbtx (n=236) and IFX-EU (n=248), respectively, and 57.2 (±14.44) and 58.3 (±15.34) for ADL-afzb (n=292) and ADL-EU (n=293), respectively. Mean MBDA scores were highly comparable between IFX-qbtx and IFX-EU and between ADL-afzb and ADL-EU at all measured timepoints during TP1 in each study. Conclusions These RCTs are the first to incorporate MBDA score as an exploratory assessment of biosimilarity. MBDA scores may provide objective, quantitative evidence of biosimilarity using an assessment of disease activity that is independent of the potential subjectivity inherent in joint counts, or in patient or physician global assessments. Trial registration numbers NCT02222493 and NCT02480153.

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Muhammad I. Rehman

Papers

Inflammatory disease in HLA-B27 transgenic rats

CD8αβ T Cells Are Not Essential to the Pathogenesis of Arthritis or Colitis in HLA-B27 Transgenic Rats

Effects of Nirmatrelvir/Ritonavir on Midazolam and Dabigatran Pharmacokinetics in Healthy Participants.

Use of multibiomarker disease activity scores in biosimilarity studies for the treatment of patients with rheumatoid arthritis