Transcription of Genes Involved in Sulfolipid and Polyacyltrehalose Biosynthesis of Mycobacterium tuberculosis in Experimental Latent Tuberculosis Infection

Jimmy E Rodríguez,Ana S Ramírez,Cecilia Helguera-Repetto,Rogelio Hernández-Pando,Carlos Y Soto,Jorge Gonzalez-Y-Merchand,Laura P Salas

doi:10.1371/journal.pone.0058378

Abstract

The Influence of trehalose-based glycolipids in the virulence of Mycobacterium tuberculosis (Mtb) is recognised; however, the actual role of these cell-wall glycolipids in latent infection is unknown. As an initial approach, we determined by two-dimensional thin-layer chromatography the sulfolipid (SL) and diacyltrehalose/polyacyltrehalose (DAT/PAT) profile of the cell wall of hypoxic Mtb. Then, qRT-PCR was extensively conducted to determine the transcription profile of genes involved in the biosynthesis of these glycolipids in non-replicating persistent 1 (NRP1) and anaerobiosis (NRP2) models of hypoxia (Wayne model), and murine models of chronic and progressive pulmonary tuberculosis. A diminished content of SL and increased amounts of glycolipids with chromatographic profile similar to DAT were detected in Mtb grown in the NRP2 stage. A striking decrease in the transcription of mmpL8 and mmpL10 transporter genes and increased transcription of the pks (polyketidesynthase) genes involved in SL and DAT biosynthesis were detected in both the NRP2 stage and the murine model of chronic infection. All genes were found to be up-regulated in the progressive disease. These results suggest that SL production is diminished during latent infection and the DAT/PAT precursors can be accumulated inside tubercle bacilli and are possibly used in reactivation processes.

Highlights

Mycobacterium tuberculosis (Mtb) is responsible for the greatest number of deaths by a bacterial pathogen worldwide [1]
The glycolipid thin-layer chromatography (TLC) profile of Mtb H37Rv in non-replicating persistent 1 (NRP1) was similar to that observed in bacilli grown under standard conditions
According to the purified glycolipid standards used in the 2D-TLC analysis, trehalose-based glycolipids in non-replicative persistence 2 (NRP2) showed deficient production of SL, an increased DAT content, and the accumulation of polar glycolipids with chromatographic behaviour similar to PAT (Figure 2)

Summary

Introduction

Mycobacterium tuberculosis (Mtb) is responsible for the greatest number of deaths by a bacterial pathogen worldwide [1]. 10% of these primary infections lead to progressive disease [2,3]; some bacilli remain in tissues in a non-replicating dormant or slowly replicating stage for the rest of the individual’s life This latent tuberculosis (LTB) is clinically asymptomatic, and in countries with low or moderate endemicity, most active tuberculosis (TB) cases arise as a result of the reactivation of latent bacilli [2,3]. It is possible to induce progressive disease or latent infection by the intratracheal inoculation of a high or low infecting dose of Mtb in BALB/c or C57bl/DBA mice, respectively [9,10] This LTB model is reproducible and it is characterized by granuloma formation, high expression of TNFa, iNOS, IL-2 and IFNc without tissue damage (pneumonia) displaying low and stable lung bacillary loads [9]. Progressive TB is produced by the intratracheal administration of high infecting dose that ensures bacilli proliferation, formation of granulomas with mild interstitial and perivascular inflammation raising maximal Th-1 protective response at day 21 of infection, followed by progressive bacilli burdens, in coexistence with tissue damage and emergence of Th2 cells [9,10]

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