Pre-exposure with low-dose UVA suppresses lesion development and enhances Th1 response in BALB/c mice infected with Leishmania (Leishmania) amazonensis

This study was conducted to determine w(h alpha)ether exposing mice to ultr aviolet (UV) radiation would alter the pathogenesis of infection with Leish mania (Leishmania) amazonensis (L. amazonensis) which causes progressive cu taneous disease in susceptible mouse strains. BALB/c mice were irradiated w ith 10 and 30 J/cm(2) UVA on shaved skin of the back from Dermaray (M-DMR-1 00) for 4 consecutive days before infection with Leishmania promastigotes. The course of disease was recorded by measuring the size of lesions at vari ous times after infection. Mice groups irradiated with UVA 10 and 30 J/cm(2 ) showed significantly suppressed lesion development compared with the non- irradiated mice. Light and electron microscopy revealed a few parasites at the site of inoculation in UVA-irradiated subjects. Sandwich enzyme-linked- immunosorbent-assay (ELISA) examination of sera showed dose dependently upr egulated interferon-gamma (IFN-gamma), tumor necrosis factor-alpha (TNF-alp ha) and interleukin (IL)-12, and downregulated interleukin (IL)-4 and inter leukin (IL)-10 levels in UVA-irradiated as compared with the non-irradiated mice. Positive signals for IFN-gamma mRNA in irradiated mice were obtained by RT-PCR. while non-irradiated mice showed negative results. None of the examined samples showed signal for IL-4 mRNA. The present study disclosed t hat exposure of mice to different low-doses of UVA irradiation prior to inf ection may interfere with immunity to L. amazonensis in the murine model. T his indicates that the cell-mediated response switch from Th2 to Th1 patter n suppressed the cutaneous lesions of L. amazonensis. (C) 1001 Elsevier Sci ence Ireland Ltd. All rights reserved.