Abstract 316: A Superantigen Whole Blood Challenge Test for the Quantification of Immuno-inflammation in Early Phase Drug Development

Abstract

Development of immune-modulating drugs is challenging as assessment of intended pharmacology in healthy volunteers is difficult. Commonly, ex-vivo LPS challenges of whole blood or isolated cells are applied. However, the applicability of the LPS challenge is limited as LPS primarily stimulates germ-line encoded innate-immune TLR4-receptors, and thus does not allow monitoring of pharmacological modulation of the adaptive immune compartment. We explored an alternative whole blood challenge, inducing lymphocyte-driven inflammation by the superantigen staphylococcal enterotoxin B (SEB), and compared this to LPS. Further validation was performed by assessing the inhibitory effects of different immune-modulating compounds (MAP kinase inhibitors, calcitriol, methotrexate, protein kinase C, doxycycline, simvastatin), allowing discrimination between effects on monocytes and lymphocytes. SEB induction resulted in the release of a cytokine panel that well-resembled cytokine release observed after physiological lymphocyte stimulation, with clear induction of IL-2, IFN-γ, TNF- α, IL-10 and GM-CSF. Based on TNF-α and IL-2 release, SEB’s maximal effect was reached at 100 ng/mL. Whereas inter-individual variability in EC50 was relatively small for LPS (0.32±0.10 ng/mL), for SEB inter-subject variability was distinctly higher (62±54 ng/mL). MAP kinase inhibitors and calcitriol were effective in inhibiting SEB-induced TNF-α and IL-2 release, demonstrating an inhibitory effect on the monocyte and/or lymphocyte. Importantly, whereas methotrexate, doxycycline, and simvastatin did not affect SEB-induced TNF-α release, a clear inhibiting effect on SEB-induced IL-2 release was observed, implying a direct action of these compounds on the lymphocyte. These data demonstrate that the SEB challenge can be used to estimate the immune-modulating effects of compounds directly acting on the T-lymphocyte population. As such, the whole blood SEB challenge is a useful translational tool in early drug development, especially since immune-inflammation is a target in the development of new treatment modalities for currently poorly-controlled diseases such as rheumatoid arthritis and psoriasis, and cardiovascular disease.