Ultraviolet-B irradiation of the skin for alteration of immunophenotype and functional responses in clinically isolated syndrome

Multiple sclerosis (MS) is an autoimmune disease characterised by demyelination in the CNS. T cells play a crucial role in the development of MS, with evidence of a T helper (Th)1/Th17 skewed phenotype, impaired regulatory T cell (Treg) function, and increased circulating follicular helper T cells (Tfh). Low exposure to ultraviolet‐B radiation (UVB) is a strong MS environmental risk factor. UVB is immunosuppressive; inducing Treg and downregulating Th1/Th17 pathways. Due to the therapeutic use of UVB in psoriasis we are investigating its efficacy as a therapy in a neurological autoimmune condition. We have a world first, NHMRC‐funded, randomised controlled trial of narrowband UVB phototherapy for Clinically Isolated Syndrome ‐ a first and single demyelinating event suggestive of MS. The hypothesis is that UVB phototherapy will slow or prevent the progression to MS via immunosuppression. Participants are randomised to receive, or not, 24 sessions of UVB phototherapy over 8 weeks. In addition, all participants receive vitamin D supplementation to control for the independent effects of vitamin D. Blood is collected at seven time points over the 12 month follow‐up for measurement of serum 25(OH)D3 and bio‐banking of peripheral blood mononuclear cells. Neurological examination and MRI scans are conducted to monitor clinical progression. Here we present longitudinal analysis of Th, Treg and Tfh phenotypes in n=12 participants and an equivalent number of age‐ and sex‐matched controls. This study will inform on the biomarkers of progression of disease from a pre‐MS condition, as well as the mechanisms by which UVB may be immunoregulatory.