The role of Mce proteins in Mycobacterium avium paratuberculosis infection
Rosemary Blake1, Kirsty Jensen2, Neil Mabbott2
1The Roslin Institute and Royal (Dick) School of Veterinary Studies, University of Edinburgh, Edinburgh, UK. rblake3@ed.ac.uk.
Abstract:
Mycobacterium avium subspecies paratuberculosis (MAP) is the causative agent of Johne's Disease, a chronic granulomatous enteritis of ruminants. MAP establishes an infection in the host via the small intestine. This requires the bacterium to adhere to, and be internalised by, cells of the intestinal tract. The effector molecules expressed by MAP for this purpose remain to be fully identified and understood. Mammalian cell entry (mce) proteins have been shown to enable other Mycobacterial species to attach to and invade host epithelial cells. Here, we have expressed Mce1A, Mce1D, Mce3C and Mce4A proteins derived from MAP on the surface of a non-invasive Escherichia coli to characterise their role in the initial interaction between MAP and the host. To this end, expression of mce1A was found to significantly increase the ability of the E. coli to attach and survive intracellularly in human monocyte-like THP-1 cells, whereas expression of mce1D was found to significantly increase attachment and invasion of E. coli to bovine epithelial cell-like MDBK cells, implying cell-type specificity. Furthermore, expression of Mce1A and Mce1D on the surface of a previously non-invasive E. coli enhanced the ability of the bacterium to infect 3D bovine basal-out enteroids. Together, our data contributes to our understanding of the effector molecules utilised by MAP in the initial interaction with the host, and may provide potential targets for therapeutic intervention.
Insights
Mycobacterium avium subspecies paratuberculosis (MAP) uses effector molecules like Mce1A and Mce1D to adhere to and invade host cells. These proteins show cell-type specificity and enhance infection in intestinal models, offering potential therapeutic targets.
Area of Science:
- Microbiology
- Immunology
- Veterinary Medicine
Background:
- Mycobacterium avium subspecies paratuberculosis (MAP) causes Johne's Disease in ruminants, a significant enteritis.
- MAP infection initiates in the small intestine, requiring bacterial adhesion and internalization by host cells.
- The specific MAP effector molecules mediating host cell interaction are not fully understood.
Purpose of the Study:
- To investigate the role of specific Mycobacterium avium subspecies paratuberculosis (MAP) effector molecules in host cell interaction.
- To characterize the function of MAP Mce1A, Mce1D, Mce3C, and Mce4A proteins in bacterial adhesion and invasion.
- To assess the cell-type specificity and functional relevance of these MAP effector proteins in infection models.
Main Methods:
- Expression of MAP Mce proteins (Mce1A, Mce1D, Mce3C, Mce4A) on the surface of non-invasive Escherichia coli.
- Assessing E. coli attachment, intracellular survival, and invasion in human THP-1 and bovine MDBK cells.
- Evaluating the infection capability of engineered E. coli in 3D bovine enteroid models.
Main Results:
- Expression of Mce1A significantly enhanced E. coli attachment and intracellular survival in THP-1 cells.
- Mce1D expression significantly increased E. coli attachment and invasion in MDBK cells, indicating cell-type specificity.
- Both Mce1A and Mce1D on E. coli surface enhanced infection of 3D bovine enteroids.
Conclusions:
- MAP utilizes effector molecules such as Mce1A and Mce1D for initial host interaction and invasion.
- These MAP effector proteins exhibit cell-type specificity in their interactions with host intestinal cells.
- The identified effector molecules represent potential targets for developing therapeutic interventions against Johne's Disease.
