Background Ustekinumab blocks the action of IL-12 and IL-23 by interfering with binding of the p40 subunit to the IL-12Rβ1 subunit used by IL-12 and IL-23 receptors. IL-12 and IL-23 are important cytokines that promote Th1 and Th17 responses. They are produced by monocytes in response to bacterial products such as LPS.
Objectives This study aimed to clarify if therapeutic blockade of p40 modulates frequencies of Th1 and Th17 effector cells and/or if it affects innate responses to LPS.
Methods 20 AS Patients were treated with 90 mg Ustekinumab s.c. at baseline, week 4 and week 16 . Heparinized peripheral venous blood was collected at baseline and at week 24 from these patients and from 20 healthy donors.
To determine T effector cell frequencies, we performed in vitro stimulation of whole blood with either phorbol myristate acetate/ionomycin (PMA/I) or with the superantigen SEB for 6 hours with Brefeldin A added after 2 hours. IFNg and TNFa production by CD4+ T cells was determined after intracellular staining and detection by FACS. The frequency of Th17 cells was determined by FACS after enrichment of CD40L+ T cells directly after stimulation according to the method of Bacher et al. .
To analyse innate cytokine responses to bacterial stimuli whole blood was mixed with media and incubated with or without LPS for 20 hours. IL-23 and IL-22 (a cytokine induced by IL-23) was detected in the supernatants by ELISA.
Results Ustekinumab treatment did not result in changes of the frequency of Th1 cells according to IFNg or TNFa secretion or in Th17 cells (Table 1).
In 20h whole blood stimulations we observed elevated spontaneous (w.o. LPS) IL-22 secretion in AS patients at baseline compared to healthy controls. This elevated spontaneous IL-22 secretion decreased upon Ustekinumab treatment (Table 2). Also the LPS-induced IL-23 levels were lower after treatment with Ustekinumab at week 24 compared to baseline (p<0.05).
Conclusions Ustekinumab treatment did not affect Th1 or Th17 effector cell frequencies in AS patients. However, reduction of IL-22 and IL-23 production upon Ustekinumab treatment may point to effects rather on innate immune functions.
Poddubnyy D, Hermann KG, Callhoff J, Listing J, Sieper J: Ustekinumab for the treatment of patients with active ankylosing spondylitis: results of a 28-week, prospective, open-label, proof-of-concept study (TOPAS). Annals of the rheumatic diseases 2014.
Bacher P, Schink C, Teutschbein J, Kniemeyer O, Assenmacher M, Brakhage AA, Scheffold A: Antigen-reactive T cell enrichment for direct, high-resolution analysis of the human naive and memory Th cell repertoire. J Immunol 2013, 190(8):3967-3976.
Acknowledgements This study was supported by an unrestricted research grant from Janssen-Cilag.
Disclosure of Interest None declared