Work

Investigating changes in monocyte phenotypes and functions in active visceral leishmaniasis patients

Year: 2016

Type: article

Abstract: Background: Visceral Leishmaniasis (VL) is a major public health problem in the Indian subcontinent. Mononuclear cells have direct role in initiation of inflammation, anti parasitic defences and ultimately in maintenance of tissue homeostasis. Monocytes play an important role as immune effector cells but their role in VL is not well known. We hypothesised that M2 macrophages play an important role in VL pathogenesis and aimed to characterise monocytes phenotypically and functionally. Methods & Materials: We established M1 and M2 macrophage polarization dynamics in the whole blood of active VL patients at an intervals of 7 days for four weeks until their drug treatment was complete. Monocytes were phenotypically charecterised by immunophenotyping studies for chemokine receptors CCR2, CX3CR1, CCR7 and cell adhesion molecules VCAM1, ICAM1, PECAM1. Functional charecterization includes quantitation of intracellular TNF-α, IL-6, IL-1β production, gene expression level measurement of various M1, M2 markers in CD14 enriched cells from active and cured VL cases and in endemic healthy controls. Myeloperoxidase expression, phagocytosis and intracellular Leishmania parasite killing by monocytes were also examined. Results: We found only minor changes in the frequency of M1 and M2 macrophages at the beginning and end of drug treatment, but observed several significant changes in the expression of cell surface markers (CD206, CD163) used to identify these cell subsets. In particular, we found that M2 macrophages increased in frequency and changed expression of cell surface molecules 14 days after drug treatment commenced, suggesting a potential role in tissue repair and homeostasis. We also observed significantly upregulated expression of several M2 markers (TGM2, PKM, SLC2A1) at gene level. We found reduced expression of CD14 on monocytes from active VL patients, but exacerbated TNF-α, IL-6 and dercreased production of IL-1β in response to SLA/LPS stimulation, compared with the same cells from drug cured and endemic control samples. We also found decreased myeloperoxidase expression by monocytes in VL. Conclusion: Together, our findings indicate dynamic changes to macrophage and monocytes populations in VL patients over the course of drug treatment, and suggest that the functions of these cells may change at different stages of disease. We found upregulation of some markers for monocyte deactivation.

Source: International Journal of Infectious Diseases

DOI: 10.1016/j.ijid.2016.02.815