Persistence of interleukin (IL)-17A+ T lymphocytes and IL-17A expression in treatment-resistant psoriatic plaques despite ustekinumab therapy

Colonic mucosal associated invariant T cells in Crohn's disease have a diverse and non-public T cell receptor beta chain repertoire

OBJECTIVES

Mucosal-Associated Invariant T (MAIT) cells are T cells with a semi-invariant T cell receptor (TCR), recognizing riboflavin precursors presented by a non-polymorphic MR1 molecule. As these precursors are produced by the gut microbiome, we characterized the frequency, phenotype and clonality of MAIT cells in human colons with and without Crohn's disease (CD).

METHODS

The transcriptome of MAIT cells sorted from blood and intestinal lamina propria cells from colectomy recipients were compared with other CD8+ T cells. Colon biopsies from an additional ten CD patients and ten healthy controls (HC) were analyzed by flow cytometry. TCR genes were sequenced from individual MAIT cells from these biopsies and compared with those of MAIT cells from autologous blood.

RESULTS

MAIT cells in the blood and colon showed a transcriptome distinct from other CD8 T cells, with more expression of the IL-23 receptor. MAIT cells were enriched in the colons of CD patients, with less NKG2D in inflamed versus uninflamed segments. Regardless of disease, most MAIT cells expressed integrin α4β7 in the colon but not in the blood, where they were enriched for α4β7 expression. TCR sequencing revealed heterogeneity in the colon and blood, with few public sequences associated with cohorts.

CONCLUSION

MAIT cells are enriched in the colons of CD patients and disproportionately express molecules (IL-23R, integrin α4β7) targeted by CD therapeutics, to suggest a pathogenic role for them in CD. Public TCR sequences were neither common nor sufficiently restricted to a cohort to suggest protective or pathogenic antigen-specificities.

Secukinumab versus guselkumab in the complete resolution of ustekinumab-resistant psoriatic plaques: The ARROW study

Interleukin (IL)-23-independent IL-17A production has been suggested to be involved in persistent manifestations of psoriatic disease, including anti-IL-12/23-refractory psoriatic plaques; this study aimed to test this hypothesis by investigating the clinical and molecular effects of direct IL-17A (with secukinumab) versus selective IL-23 inhibition (with guselkumab) in patients with anti-IL-12/23 (ustekinumab)-refractory psoriatic plaques. A 16-week, randomized, open-label, parallel-group, Phase IIa study (ARROW, NCT03553823) was conducted in patients with ≥1 active psoriatic plaque (total clinical score [TCS] ≥6) at screening despite treatment with ustekinumab, and a Psoriasis Area and Severity Index (PASI) score 1-10. Patients were randomized 1:1 to receive secukinumab 300 mg (n = 20) or guselkumab 100 mg (n = 20). Biopsies from one refractory ('target plaque') were obtained at baseline and Week 16. The primary endpoint was the proportion of patients whose ustekinumab-refractory target plaque achieved clear/almost clear status (TCS 0-2) at Week 16. Transcriptomic and histological analyses were conducted on target plaques to determine the molecular effects of direct IL-17A versus selective IL-23 inhibition. At Week 16, target plaque clear/almost clear status was achieved in 60.0% of patients treated with secukinumab versus 40.0% of patients treated with guselkumab (p = 0.1715). Molecular analyses identified that secukinumab modulated a greater proportion of psoriasis disease transcriptome genes (72.1% vs. 48.0%) and resulted in more histological responders (72.2% vs. 53.3%) compared with guselkumab. Secukinumab demonstrated a greater clinical and molecular effect on ustekinumab-refractory psoriatic plaques versus guselkumab. These results are consistent with the hypothesis that IL-23-independent IL-17 mechanisms may be relevant to the inflammation driving refractory manifestations of psoriasis.

The Essential Role of IL-17 as the Pathogenetic Link between Psoriasis and Metabolic-Associated Fatty Liver Disease

Interleukin 17 (IL-17) is an effector cytokine that plays a key role in the pathogenesis of both psoriasis and metabolic-associated fatty liver disease (MAFLD), a condition that is more prevalent and severe in patients with psoriasis. In liver inflammation, IL-17 is mainly produced by CD4+ T (TH17) and CD8+ T cells (Tc17), although numerous other cells (macrophages, natural killer cells, neutrophils and Tγδ cells) also contribute to the production of IL-17. In hepatocytes, IL-17 mediates systemic inflammation and the recruitment of inflammatory cells to the liver, and it is also implicated in the development of fibrosis and insulin resistance. IL-17 levels have been correlated with progression from MAFLD to steatohepatitis, cirrhosis, and even hepatocellular carcinoma. Clinical trials have shown that inhibiting IL-17A in patients with psoriasis could potentially contribute to the improvement of metabolic and liver parameters. A better understanding of the key factors involved in the pathogenesis of these chronic inflammatory processes could potentially lead to more efficient treatment for both psoriasis and MAFLD, and help to develop holistic strategies to improve the management of these patients.

Epidermal Hyperproliferation With Less Prominent Dermal Inflammation Is the Unique Histopathological Feature of the Refractory Lesions in Psoriasis Treated With Ustekinumab

ABSTRACT

Although ustekinumab (UST) shows excellent efficacy in treating psoriasis, not all patients have a complete clearance rate. The purpose of this study was to investigate the histopathological characteristics of refractory psoriasis lesions in patients with excellent response to UST. Fifty-seven patients with newly diagnosed psoriasis and 66 patients with a 75% reduction in the Psoriasis Area and Severity Index score after UST treatment were included. Computer-aided image analysis was performed to measure the epidermal thickness, horny layer thickness, number of dermal vessels, and dermal inflammatory cell infiltration rate. Parakeratosis was scored using a 4-point scale. These measurements were compared between the refractory lesions of UST-treated patients and the untreated lesions of newly diagnosed patients after the adjustment for confounding factors. The dermal inflammatory cell infiltration rate was significantly lower in the refractory lesions (P = 0.022). Meanwhile, the epidermal thickness, horny layer thickness, grade of parakeratosis, and dermal vessel count did not differ between the groups (P = 0.125, 0.719, 0.542, and 0.758, respectively). Subgroup analyses were performed within the UST-treated group after dividing them into 2 groups according to the number of treatments or treatment response rates. None of these features were significantly different between the subgroups. This study suggests that the reduction of dermal inflammation by UST was not sufficient to ameliorate the epidermal changes and implies the role of the interleukin-23-independent downstream cytokine pathway in causing the refractory lesions among patients who responded well to UST. The continuation of UST treatment might not further improve epidermal alterations.

Persistent expression of interleukin-17 and downstream effector cytokines in recalcitrant psoriatic lesions after ustekinumab treatment

The interleukin (IL)-23/T-helper (Th)17 axis is considered central to the pathogenesis of psoriasis, with IL-36γ considered a marker for histological differential diagnosis. However, expression data regarding key cytokines in the pathogenesis of psoriasis, as well as data on the effects of IL-23 inhibition on downstream cytokines in human psoriatic skin, are limited. We investigated the expression profile of key cytokines and the effect of ustekinumab (UST) on cytokine expression in human psoriatic tissue. Tumor necrosis factor (TNF)-α, IL-23, IL-17A, and IL-22 were highly expressed in the epidermis, dermal papillae, and upper dermis in patients with psoriasis compared with controls; IL-36γ was strongly expressed in the upper epidermis. Compared with the untreated group, expression intensity and area of IL-23 were significantly decreased in the UST group; expression areas of TNF-α, IL-17A, IL-22, and IL-36γ did not differ. This study identified the distribution and quantitative expression levels of key cytokines in psoriatic lesions and demonstrated that only IL-23 was downregulated without blocking downstream effector cytokines in recalcitrant psoriatic lesions during UST treatment. Our results suggest that, although IL-23 is inhibited, the persistent expression of IL-17 through an alternative pathway maintains the vicious cycle of the TNF-α/IL-23/IL-17 axis with IL-36γ, inducing refractory psoriatic lesions in patients with well-controlled psoriasis.

Persistence of Inflammatory Phenotype in Residual Psoriatic Plaques in Patients on Effective Biologic Therapy

Many psoriasis patients treated with biologics do not achieve total skin clearance. These patients possess residual plaques despite ongoing biologic treatment. To elucidate mechanisms of plaque persistence despite overall good drug response, we studied 50 subjects: psoriasis patients with residual plaques treated with one of three different biologics, untreated patients, and healthy controls. Skin biopsies from all subjects were characterized using three methods: mRNA expression, histology, and FACS of hematopoietic skin cells. Although all three methods provided evidence of drug effect, gene expression analysis revealed the persistence of key psoriasis pathways in treated plaques, including granulocyte adhesion and diapedesis, T helper type17 activation pathway, and interferon signaling with no novel pathways emerging. Focal decreases in parakeratosis and keratinocyte proliferation and differential reduction in IL-17 producing CD103- T cells, but no change in CD103+ tissue-resident memory T cells were observed. Of note, antitumor necrosis factor increased the interferon signaling pathway already present. Interestingly mast cells were the dominant source of IL-22 in all psoriasis subjects. These data suggest that while subtle differences can be observed in drug-treated plaques, underlying biologic mechanisms are similar to those present in untreated psoriatic lesions.