Solar ultraviolet radiation exposure influences the immune response to immunization: Results from an Australian clinical trial

Abstract

Background Exposure to ultraviolet radiation (UVR) causes systemic immune suppression. The effect of natural levels of UVR exposure on the primary immune response to vaccination has not been previously reported. Method The Australian Ultraviolet Radiation and Immunity Study was conducted in the Australian cities of Canberra (35o2’S) and Townsville (19o1’S) from July 1010 to August 2011. Healthy volunteers (n=222) aged 18–40 years were immunised subcutaneously with keyhole limpet haemocyanin (KLH). Acute personal UVR exposure was measured by electronic UVR wrist dosimeters worn for five days pre- and post-vaccination, and by sun exposure diary. Cumulative UVR exposure was quantified by microtopographic analysis of silicone impressions of sun-exposed skin. Potential confounders were measured (e.g. serum 25-OH vitamin D). Immune function measured over a 21-day period post-vaccination included: anti-KLH IgG1 levels; KLH-specific delayed-type hypersensitivity (DTH) response; and quantification of T-helper (CD4+) lymphocyte subsets. Results In multiple regression models, higher acute UVR exposure on the day prior (‘Day 5’) to vaccination (p=0.015), and Days 5-8 and 5-9 (p=0.039 and p=0.025, respectively) were associated with reduced DTH response to KLH challenge at day 21 post-vaccination.”Change in T-helper 17 cell percentage between pre- and post-vaccination time points differed in direction when comparing the low and high UVR exposure groups (-0.39%vs.0.31%; p=0.004). There was no association between UVR exposure and anti-KLH IgG1. 25-OH vitamin D was not associated with immune function outcomes. Conclusions Acute UVR exposures, relevant to day-to-day activities, modulates the cell-mediated primary immune responses to KLH vaccination.