Association of Post Kala-Azar Dermal Leishmaniasis pathogenesis with prolonged sunlight (ultraviolet radiations) exposure in VL endemic population of Bihar.

Post Kala-azar Dermal Leishmaniasis (PKDL) is a complication of Visceral Leishmaniasis (VL) and acts as a reservoir for Leishmania parasites. With climatic changes and ozone depletion increasing ultraviolet radiation (UVR), we investigated the connection between UVR and PKDL development. We have measured sun-light UVR intensities by UV light meters and satellite-based methods. Our data showed a concerning increase in the UV index (> 12.0-14.5) during summer and pre-monsoon season. A cohort of 283 PKDL patients revealed a strong correlation between prolonged sun-light (UVR) exposure (4-8 h/day) and worsening skin lesions, with many patients, particularly labourers and farm workers, reporting sunburn and/or irritation, skin sensitivity. Additionally, in vitro studies with human THP-1 cells showed UVB-induced cytotoxicity and immuno-suppression, that likely to be associated with PKDL development. Serum analysis showed significant alterations in key cytokines concentrations (IL-10, IL-12), IFN-γR and Vitamin-D, iron level among PKDL and VL patients versus healthy controls. Specifically, PKDL patients exhibited upregulated expressions of TLRs-2/4 and TNFR-2, but down-regulation of TNFR-1 were observed in PKDL patients than the healthy controls. In essence, our findings implicate the risk posed by increasing sunlight UVR exposure for PKDL development in vulnerable populations from VL endemic regions of Bihar.