pe class proteins of m. tuberculosis
DESCRIPTION
Studies on the implications of PE class proteins of Mycobacterium tuberculosis as determinants of pathogenicity and Immuno-prophylaxisTRANSCRIPT
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L/O/G/O
Sameer Tiwari Division of Microbiology
Studies on the implications of PE class
proteins of Mycobacterium tuberculosis
as determinants of pathogenicity and
Immuno-prophylaxis
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M. tuberculosis
Robert Koch 1882
~9 million new cases ~2 million deaths worldwide
2011
2011 ~2 million new cases in India
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M. tuberculosis genome
Cole et al. (1998)
Nature 393: 537-544
4,000 genes
40% orphans
100 highly
homologous
PE/PPE genes
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General Classification of M. tuberculosis genes
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PE/PPE proteins
100 highly homologous genes with signature sequence of Pro-Glu (PE) amino acid near amino terminus.
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PE-PGRS (polymorphic GC rich repetitive sequences)
Larger proteins domain extremely rich in Gly (~ 40%) & Ala (~ 25%)
residues PGRS domain occur as repetitive sequences (repeated >30times
within domain)
Rv3508 Average Rv0742
1901 aa 550 aa 175 aa
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Extensive functional redundancy
Close genomic & evolutionary association with ESX regions
Highly immunogenic
Properties of PE proteins
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Classification of PE/PPE
protein families
Sequence variation between M.
tuberculosis H37Rv & M. bovis
BCG
Cole et al. (1998) Nature 393: 537-544
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Role of PE_PGRS
Homeostasis of mycobacterial cell
Intracellular survival
Multiplication within its chosen environment
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Why to study?
Unique gene
family
No counterpart
in bacteria
Potential
source of
antigenic
variation
No strict
correlation with
pathogenic
strains
Little is known
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Role in virulence (Ramakrishnan et al.) pathogenic Mycobacterium
marinum expresses two PE_PGRS genes in granulomas of infected
frogs and that M. marinum mutants containing deletions in these genes
replicate poorly in macrophages
Known facts…..
Several PE_PGRS proteins have been localized to the cell
surface, and allelic diversity among M. tuberculosis isolates indicates
that they could serve as a source of antigenic variation for this
pathogen.
Microarray analysis has also suggested that variable expression of certain PE_PGRS genes occurs under conditions that mimic in vivo
pathogenesis such as nutrient depletion, low pH or oxidative stress
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Objectives
Delineation of protective immune response of the proteins,
upon challenge with MTB
Regulation of PE genes in mycobacteria in Culture grown,
persistent, Hypoxic and from infected macrophages/ from
infected lungs.
.
Evaluation of complete cellular immune responses
incurred by these proteins
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What we Achieve?
Identification of domains involved in binding to cell
surface or other intracellular components will help in
designing targets against these proteins.
Characterization of PE_PGRS gene expression
mechanisms of pathogenesis of mycobacteria in macrophages
Vaccine candidates as well as virulence factors.
Quantification of the amounts of CFP-10/ESAT-6
secreted into the macrophages during early stages of infection will give
an insight of their role in virulence.
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Impact on antigen-presentation pathways
Ensuing host immune responses, and
Also provide a mechanism for generating antigenic diversity in
mycobacteria
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Research Plan
1
2
3
4
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5
6
7
8
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Conclusions
The PE proteins/PPE functions to be the rich source of protective
antigens involved in antigenic variation and immune-pathogenic
importance.
PE/PPE genes involve in host-pathogen interactions, such as
antigenic variability, virulence, and persistence of the bacillus.
Their surface-exposed domains are also involved in the shaping of
the bacterial cell structure. These proteins are capable of forming
heterodimers which are secreted and thought to play a role in
signal transduction.
The study will investigate the characteristics of PE3 (Rv0159c) &
PE4 (Rv0160c) and their associations with ESAT-6 & CFP-10 and
finally their interactions with macrophage.
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Laboratory: Microbiology Division, CDRI, Lucknow
Equipments Bio-hood, CO2 Incubator, Refrigerated Centrifuge,
Microfuge, Fluorescent Microscope, Incubator Shaker, Water Bath,
Incubators, -860C Deep freezer, Power supplies, Gel apparatus,
Gradient Thermal Cycler, Gel Documentation System, Sonicator,
Protein Purification System, 2-D Gel Electrophoresis System, ABI Real
Time PCR.
Other resources
Animal House and BSL-III facility
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Thank you for your
patience….