Effects of skin UV light exposure on the immune response against a pathogen and a vaccine.

CELA E; CALVINHO LF; GONZALEZ C; FRIEDRICH A; LEDO C; PAZ M; GOMEZ MI; LEONI J; GONZALEZ MAGLIO D.

AVEIRO

Congreso; 16th Congress of the European Society for Photobiology; 2015

European Society for Photobiology

It is well knownthat ultraviolet radiation (UVr) leads to immunosuppression, inhibiting CHSreactions. However, the way UVr modulates immune responses againstmicroorganisms has been poorly explored. Considering that Staphylococcus aureus (SA) causes skin infections and this organ isthe main target of UVr, our first aim was to evaluate if UVr can modulate thehost response to SA infection, using invitro and in vivo models. BesidesSA infection, skin is also a target for vaccination. Our second objective wasto evaluate the effect of UVr on BCG vaccination in vivo. For in vitroexperiments we used UVr-exposed HaCaT cells, challenged with heat killed SA(hkSA) and purified lipoteichoic acid (LTA). For both in vivo experiments (SA and BCG), we compared 2 types of exposuresof SKH:1 mice: a single high UV dose (shUVd - 400 mJ/cm2), as aharmful exposure vs. repetitive low UV doses (rlUVD - 4 consecutive days, 20mJ/cm2), simulating daily exposures. Previously, we have found thatshUVd promotes skin inflammation while it diminishes CHS reaction and antibodyproduction, in contrast to rlUVd that does not induce inflammation andincreases CHS response and antibody production. HaCaT cells wereirradiated with 10, 25 and 50 mJ/cm2 and immediately challenged withhkSA, LTA or LPS as control. SKH:1 mice were irradiated and 24h later weresubcutaneously infected with SA strain LAC (1x107 CFU) orintradermally vaccinated with BCG (1x104 CFU). Non-irradiated cellsand mice were used as control (C). In vitro hkSA and LTAchallenge of irradiated HaCaT cells promotes greater inflammatory cytokinesproduction (TNF-α and IL-6) than E. coli LPS stimuli or the correspondingnon-irradiated challenged cells.In vivo SA infectionproduced no differences in weight loss, abscess size and bacterial countsbetween control and irradiated mice. shUVd mice did not show differences in thedissemination of bacteria or in spleen cells proliferative response, whereasthey produced higher titers of specific IgG and IgM (p<0,05 vs C).Contrarily, rlUVd mice showed a marked increase in the dissemination ofbacteria (p<0,05 vs C), specific spleen cells proliferative responses(p<0,05 vs C) with increased IL-4 secretion and presented just higher IgMtiters (p<0.05 vs. C). Regarding BCG, shUVd did not affect the response tovaccination measured as antibody production and specific T cell activity,whereas rlUVd promoted an increased production of IL-4 by specific T cells,without affecting antibody production. These results show that UVr modulatesskin infection and vaccine response, depending on the type of exposure.