Shweta Joshi

Despite the critical role of lipid-mediated signaling in regulating host immunity, endorsed by growing evidence, the interaction between lipid metabolism and immune response remains largely unknown. This review aims to elucidate the immunomodulatory role of a lung-enriched lipid metabolic pathway mediated by the phospholipase A2 (PLA₂) family, which comprises a diverse range of lipid-hydrolyzing enzymes. Based on their location, structure, substrate specificity and physiological roles, PLA₂s can be classified into secreted PLA₂s (sPLA₂s), cytosolic PLA₂s (cPLA₂s), calcium-independent PLA₂s (iPLA₂s), and lysosomal-associated PLA₂s (lPLA₂s). These PLA₂ isoforms are similar in that they can all cleave cellular membrane-associated phospholipids, releasing free lysophospholipids and fatty acids such as arachidonic acid, which subsequently serve as precursors for a wide range of bioactive mediators responsible for physiological functions and pathological changes. Respiratory infections, especially those caused by bacteria and viruses, represent a substantial threat to the health of the population worldwide and cause billions of disease cases and millions of deaths annually. Respiratory infections provoke airway inflammation, characterized by increased vascular permeability and the influx of immune cells, resulting in tissue damage, impaired gas exchange, acute respiratory distress syndrome (ARDS) and even death. During infections and inflammatory milieu, airway-expressed PLA₂ can further increase and exhibit protection by restricting pathogens and inflammation or, in contrast, exacerbate the pathogenesis. In this manuscript, we will provide an overview of the current knowledge on the biological functions of PLA₂ isoforms, especially concerning membrane-associated isoforms in respiratory infections, and offer insight into the spatial and temporal regulation of immune responses mediated by PLA₂ and the subsequent modulation of host–pathogen interactions and the balance between protective effects and pathological outcomes.

: Leprosy and post–kala-azar dermal leishmaniasis (PKDL) are co-endemic neglected tropical diseases often misdiagnosed because of close resemblance in their clinical manifestations. The test that aids in differential diagnosis of leprosy and PKDL would be useful in endemic areas. Here, we report development of a multiplex loop-mediated isothermal amplification (m-LAMP) assay for differential detection of Mycobacterium leprae and Leishmania donovani using a real-time fluorometer. The m-LAMP assay was rapid with a mean amplification time of 15 minutes, and analytical sensitivity of 1 fg for L. donovani and 100 fg for M. leprae. The distinct mean Tm values for M. leprae and L. donovani allowed differentiation of the two organisms in the m-LAMP assay. Diagnostic sensitivity of the assay was evaluated by using confirmed cases of leprosy (n = 40) and PKDL (n = 40) (tissue and slit aspirate samples). All the leprosy and PKDL samples used in this study were positive by organism-specific QPCR and loop-mediated isothermal amplification assays. The diagnostic sensitivity of the m-LAMP assay was 100% (95% CI: 91.2–100.0%) for detecting PKDL and 95% for leprosy (95% CI: 83.1–99.4%). Our m-LAMP assay was successfully used to detect both M. leprae and L. donovani in a patient coinfected with leprosy and macular PKDL. The m-LAMP assay is rapid, accurate, and applicable for differential diagnosis of leprosy versus PKDL, especially in endemic areas.