Portrait of a Pathogen: The Mycobacterium tuberculosis Proteome In Vivo

Abstract

Background Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is a facultative intracellular pathogen that can persist within the host. The bacteria are thought to be in a state of reduced replication and metabolism as part of the chronic lung infection. Many in vitro studies have dissected the hypothesized environment within the infected lung, defining the bacterial response to pH, starvation and hypoxia. While these experiments have afforded great insight, the picture remains incomplete. The only way to study the combined effects of these environmental factors and the mycobacterial response is to study the bacterial response in vivo.Methodology/Principal FindingsWe used the guinea pig model of tuberculosis to examine the bacterial proteome during the early and chronic stages of disease. Lungs were harvested thirty and ninety days after aerosol challenge with Mtb, and analyzed by liquid chromatography-mass spectrometry. To date, in vivo proteomics of the tubercle bacillus has not been described and this work has generated the first large-scale shotgun proteomic data set, comprising over 500 unique protein identifications. Cell wall and cell wall processes, and intermediary metabolism and respiration were the two major functional classes of proteins represented in the infected lung. These classes of proteins displayed the greatest heterogeneity indicating important biological processes for establishment of a productive bacterial infection and its persistence. Proteins necessary for adaptation throughout infection, such as nitrate/nitrite reduction were found at both time points. The PE-PPE protein class, while not well characterized, represented the third most abundant category and showed the most consistent expression during the infection.Conclusions/SignificanceCumulatively, the results of this work may provide the basis for rational drug design – identifying numerous Mtb proteins, from essential kinases to products involved in metal regulation and cell wall remodeling, all present throughout the course of infection.

PPE38 Modulates the Innate Immune Response and Is Required for Mycobacterium marinum Virulence

“…As such, members of the PE/PPE family of proteins may play subtly different functional roles and are required at different stages of disease. PPE38 was identified as one of the most highly expressed proteins of M. tuberculosis after a 90-day infection of guinea pig, suggesting that PPE38 plays a potentially critical role in persistent infection (43). This is in accor- dance with our finding that PPE38 plays a role in the virulence of M. marinum.…”

An Unbiased Genome-Wide Mycobacterium tuberculosis Gene Expression Approach To Discover Antigens Targeted by Human T Cells Expressed during Pulmonary Infection

“…A subsequent literature search revealed that almost all further selected IVE-TB proteins (14 of the 16) have been identified previously in M. tuberculosis proteomic studies, confirming the protein expression of the M. tuberculosis genes identified in our study (44)(45)(46)(47)(48)(49)(50)(51)(52)(53)(54)(55)(56)(57) (Table III). Indeed, we observed that M. tuberculosis- FIGURE 3.…”

bis -Molybdopterin Guanine Dinucleotide Is Required for Persistence of Mycobacterium tuberculosis in Guinea Pigs

“…The detection of NarG, NarH, and FdhF in guinea pigs during pulmonary infection (33) confirms that these proteins are expressed by M. tuberculosis in this animal model (32). Drug treatment of guinea pigs infected with M. tuberculosis results in the resolution of secondary lesions but has a reduced effect on primary lesions, where some bacteria are found in the necrotic zone, and the majority of the persisting organisms are located in the acellular rim of the lesion (34).…”