Tuberculosis (TB), caused by Mycobacterium tuberculosis (Mtb), is a global infectious disease emergency. Each year an estimated 8 million people develop, and about two million people die of TB. Synergy with AIDS, the emergence of drug-resistance and the lack of effective anti-TB drugs and vaccines has worsened this situation. New drugs and vaccines are urgently needed to effectively control TB. This requires a better understanding of how Mtb adapts to a wide-variety of environmental conditions, inevitably faced by it during the various stages of infection. Nonhuman Primates (NHPs), arguably, best model critical aspects of TB. Analysis of the mechanisms employed by Mtb to successfully infect and persist in NHP lungs would therefore be very useful. We studied genes essential for growth/survival of Mtb in the NHP lungs experimentally exposed to high doses of aerosols of an Mtb transposon mutant library. In this acute model of TB, 33.13% of all tested mutants were attenuated for in-vivo growth compared to the mouse model where only ~6% of all mutants are attenuated. The Mtb mutants attenuated for in-vivo survival in primates were involved in the transport of lipid virulence factors;biosynthesis of cell-wall arabinan and peptidoglycan, fatty-acids and polyketides;DNA repair;sterol metabolism and mammalian cell-entry (mce). Our study highlights the various virulence-mechanisms employed by Mtb for infection and to overcome the hostile environment encountered during infection of NHP lungs. We would like to leverage our ability to model the various clinical phases of human TB - acute, pulmonary TB, chronic-progressive TB and latent, asymptomatic TB in NHPs - to study the growth/survival phenotype profiles of Mtb mutants. Further, we would like to better understand the role of two Mtb pathways crucial for virulence and pathogenesis, using the NHP model. These include the mce1/mce4 operons, whose members were among mutants that were attenuated for growth in NHP lungs;and members of the dos regulon, which were surprisingly not attenuated in NHP lungs, in-spite of their well-defined roles in latency, persistence and defense against hypoxia.

Public Health Relevance

Tuberculosis (TB) is a global emergency, responsible for the death of an estimated 2 million people annually. Monkeys, due to their genetic and physiological similarities to humans, are a very good animal system to model TB. Out of the several hundreds of genes present in the chromosome of the tubercle bacillus, we have determined which ones are needed to establish a successful infection in the lungs of monkeys. These results will be compared to those obtained from animals with TB/AIDS co-infection. Genes from the mce (mammalian cell entry) family were among those which were attenuated in the NHP lungs. We will perform functional studies using Mycobacterium tuberculosis (Mtb) and defined mutants in mce genes, using our monkey model, to better understand their role in disease process.

National Institute of Health (NIH)
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AIDS-associated Opportunistic Infections and Cancer Study Section (AOIC)
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Lacourciere, Karen A
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Tulane University
Schools of Medicine
New Orleans
United States
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Dutta, Noton K; McLachlan, James; Mehra, Smriti et al. (2014) Humoral and lung immune responses to Mycobacterium tuberculosis infection in a primate model of protection (.) Trials Vaccinol 3:47-51
Gautam, Uma S; Mehra, Smriti; Ahsan, Muhammad H et al. (2014) Role of TNF in the altered interaction of dormant Mycobacterium tuberculosis with host macrophages. PLoS One 9:e95220
McGillivray, Amanda; Golden, Nadia Abrahams; Gautam, Uma Shankar et al. (2014) The Mycobacterium tuberculosis Rv2745c plays an important role in responding to redox stress. PLoS One 9:e93604
Mehra, Smriti; Alvarez, Xavier; Didier, Peter J et al. (2013) Granuloma correlates of protection against tuberculosis and mechanisms of immune modulation by Mycobacterium tuberculosis. J Infect Dis 207:1115-27
Martinez, Alejandra N; Mehra, Smriti; Kaushal, Deepak (2013) Role of interleukin 6 in innate immunity to Mycobacterium tuberculosis infection. J Infect Dis 207:1253-61
Dutta, Noton K; Mehra, Smriti; Martinez, Alejandra N et al. (2012) The stress-response factor SigH modulates the interaction between Mycobacterium tuberculosis and host phagocytes. PLoS One 7:e28958
Mehra, Smriti; Golden, Nadia A; Stuckey, Kerstan et al. (2012) The Mycobacterium tuberculosis stress response factor SigH is required for bacterial burden as well as immunopathology in primate lungs. J Infect Dis 205:1203-13
Roy, Chad J; Sivasubramani, Satheesh K; Dutta, Noton K et al. (2012) Aerosolized gentamicin reduces the burden of tuberculosis in a murine model. Antimicrob Agents Chemother 56:883-6
Kaushal, D; Mehra, S; Didier, P J et al. (2012) The non-human primate model of tuberculosis. J Med Primatol 41:191-201
Mehra, Smriti; Golden, Nadia A; Dutta, Noton K et al. (2011) Reactivation of latent tuberculosis in rhesus macaques by coinfection with simian immunodeficiency virus. J Med Primatol 40:233-43

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