Executive Summary : | Post-kala-azar dermal leishmaniasis (PKDL) generally occurs as a sequel to Visceral Leishmaniasis (VL) wherein the macular/papulo-nodular lesions are parasite-rich, fuelling speculation that PKDL plays a pivotal role in the inter-epidemic transmission of VL. The magnitude of PKDL was estimated in VL affected districts of West Bengal using immunological tests and DNA based markers following either passive case detection or active case detection, wherein patients were identified during a house to house survey. The identification of cases of PKDL was more during active case detection rather than passive detection which emphasized the importance of undertaking active surveillance for potential elimination of Leishmaniasis. The presence of parasite DNA was detected by the ITS-1PCR and subsequently, the quantification of parasite load by real time PCR indicated that these DNA based assays have excellent sensitivity and specificity and should be applied for monitoring of anti-leishmanial chemotherapy. The cellular infiltrate in the dermal lesions was primarily comprised of CD8+, CD20+ and CD68+ cells. With treatment, the CD8+, CD68+ and CD20+ cell population significantly decreased, whereas the proportion of LCs increased. Monocytes/macrophages demonstrated polarization towards alternate activation, evident by impaired expression of TLR-2/4, a decreased oxidative burst, enhanced generation of anti-inflammatory cytokines and classical markers of alternate activation e.g. arginase and mannose receptor. The co-stimulatory function of T-cells in PKDL was attenuated as circulating CD3+ T-cells demonstrated a significantly decreased frequency of CD26+ cells. Furthermore, these patients showed a significant decrease in the frequency of CD45RO+ /CD8+ T-cells, along with a significantly higher proportion of CD45RA+ /CD8+ T-cells which could collectively translate into reduced formation of the immunological synapse of CD26 with CD45RO and ADA, leading to an attenuation of Th1 responses. |