AB0100 TO STUDY THE T CELL AND CYTOKINE PROFILE IN ANKYLOSING SPONDYLITIS WITH EFFECTS OF TACROLIMUS AND TADALAFIL ON THE CYTOKINES IN-VITRO

Background

Most studies have shown mixed results of Interleukin (IL)17 and IL-23 levels in patients with Ankylosing Spondylitis (AS) compared to controls; with animal studies showing a good correlation between activation of IL 23-IL 27 pathway and radiologic progression. Targeting this pathway in humans has yielded benefits with reduced inflammation and radiologic progression in AS. Controlling inflammation and fibrosis is the key to prevent osteoproliferation. Tacrolimus and tadalafil have shown to inhibit the Th17 pathway and profibrotic pathways respectively.

Objectives

To study the T cell (Th17, PD1, CD25+ CD4 T cells) and cytokine profile (IL-17, IL-23, TGF- β) in AS with influence of disease duration and activity on the above profile. To also study the effect of tacrolimus and tadalafil in ex-vivo peripheral blood monocyte (PBMC) cultures to study their anti-inflammatory and anti-fibrotic potential.

Methods

Patients with AS (ASAS classification criteria) without peripheral disease and not on biologic therapy were recruited and their demographic, clinical profile, disease activity and radiologic indices were recorded. Age and sex matched healthy controls (HC, n=21) were also recruited. Peripheral blood was drawn and sera stored; PBMCs were isolated and cultured. Serum and PBMC culture supernatant (CS) were measured for IL-17, IL-23 and TGF-β. These cytokines were measured at baseline, after stimulation with anti-CD3CD28 antibodies, and after treatment with tacrolimus(10mM/ml), tadalafil(10mM/ml) and both the drugs combined by ELISA(R&D systems, USA). The T cell profile was characterized by flow cytometry (CD4 Th17, CD4 PD1, CD4 Th17 PD1 and CD4 CD25). Statistical analysis was done using GraphPad prism v9.

Results

Twenty-five patients [28(24-36),M:F, 7.3:1] were enrolled with 90% HLA-B27 positivity. The majority had moderate-high disease activity as per ASDAS CRP and were on NSAIDs(24), complementary medications (7) and two each on methotrexate and sulfasalazine. Serum IL-17 and TGF-β, CS TGF- β were significantly elevated in AS compared to controls. All the measures cell populations were significantly elevated in AS compared to HC. When stratified by duration of disease, clinical parameters, disease activity indices, cytokine and T-cell profile was similar across the two groups. ASDAS CRP showed a significant correlation with CD4Th17+ cells (r=0.7, p=0.009) and CD4 PD1/T reg (r=-0.6, p=0.03). A positive association as observed with some cells but not with the cytokines on generalized linear modeling (Table 1). No significant correlation was observed between cytokines or T cell profiling with Modified Stokes Ankylosing Spondylitis Score. There was a significant decline in TGF- β levels in the culture supernatant with tacrolimus and tadalafil combined, however, no such difference was observed with IL-17 or IL-23. (Figure 1)

Conclusion

Serum IL-17 and TGF- β were elevated in the peripheral blood in AS. There was no difference in the cytokine and T-cell profile across early and late disease. A significant decline in TGF- β levels was seen with combined tacrolimus and tadalafil. This needs further exploration in a larger sample size with subgroup characterization as well as testing on synovial fluid and joint tissue samples.

REFERENCES:

NIL.

Acknowledgements:

NIL.

Disclosure of Interests

None Declared.