Downregulation of host tryptophan-aspartate containing coat (TACO) gene restricts the entry and survival of Leishmania donovani in human macrophage model.

Venkateswara Reddy Gogulamudi,Mohan Lal Dubey,Deepak Kaul,Venkata Subba Rao Atluri,Rakesh Sehgal

doi:10.3389/fmicb.2015.00946

Abstract

Leishmania are obligate intracellular protozoan parasites of mammalian hosts. Promastigotes of Leishmania are internalized by macrophages and transformed into amastigotes in phagosomes, and replicate in phagolysosomes. Phagosomal maturation arrest is known to play a crucial role in the survival of pathogenic Leishmania within activated macrophages. Recently, tryptophan–aspartate containing coat (TACO) gene has been recognized as playing a central role in the survival of Mycobacterium tuberculosis within human macrophages by arresting the phagosome maturation process. We postulated that a similar association of TACO gene with phagosomes would prevent the vacuole from maturation in the case of Leishmania. In this study we attempted to define the effect of TACO gene downregulation on the entry/survival of Leishmania donovani intracellularly, by treatment with Vitamin D3 (Vit.D3)/Retinoic acid (RA) and chenodeoxycholic acid (CDCA)/RA combinations in human THP-1 macrophages (in vitro). Treatment with these molecules downregulated the TACO gene in macrophages, resulting in reduced parasite load and marked reduction of disease progression in L. donovani infected macrophages. Taken together, these results suggest that TACO gene downregulation may play a role in subverting macrophage machinery in establishing the L. donovani replicative niche inside the host. Our study is the first to highlight the important role of the TACO gene in Leishmania entry, survival and to identify TACO gene downregulation as potential drug target against leishmaniasis.

Highlights

Leishmaniasis is a major public health issue in many parts of the world, affecting over 20 million people worldwide
Optimum Concentration of PMA for Differentiation of THP-1 Monocytes to Macrophages According to the results presented in Figure 1, monocytes in suspension were converted to matured macrophages in 72 h after treatment with PMA
The present study was based on the hypothesis that the transcriptional manipulation of the tryptophan–aspartate containing coat (TACO) gene leads to phagosome maturation, which will affect the survival and replication of intracellular pathogens

Summary

Introduction

Leishmaniasis is a major public health issue in many parts of the world, affecting over 20 million people worldwide. About 350 million people are at risk of being infected with leishmaniasis, and 1.5-2 million children and adults develop the disease each year (Desjeux, 2004). This disease is caused by a parasite, which belongs to the genus Leishmania. Intracellular parasites have evolved through diverse mechanisms to enhance their survival and replication within host cells (Hackstadt, 2000). These mechanisms greatly involve adaptations for survival in different intracellular compartments that permit the parasites to avoid lysosomal killing. Functions of most of these strategies remain unclear, the majority is expressed early on infectious process, suggesting that manipulation of the vacuole is critical to the outcome of the host-parasite interaction

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