Mycobacterium tuberculosis employs Cpn60.2 as an adhesin that binds CD43 on the macrophage surface

Area of Science:

• Immunology
• Microbiology
• Molecular Biology

Background:

• CD43, a glycoprotein on hematopoietic cells, is vital for macrophage binding and immune responses to Mycobacterium tuberculosis.
• Molecular chaperones, typically intracellular, are increasingly recognized for extracellular roles in host-pathogen interactions.

Purpose of the Study:

• To investigate the molecular mechanisms underlying Mycobacterium tuberculosis adherence to macrophages.
• To identify specific mycobacterial components that interact with CD43 and mediate bacterial binding.

Main Methods:

• Affinity chromatography using M. tuberculosis capsular material and recombinant CD43-Fc.
• Competitive inhibition assays with recombinant proteins and antibody-mediated epitope masking.
• Macrophage binding assays comparing CD43(+/+) and CD43(-/-) cells.

Main Results:

• Cpn60.2 (Hsp65/GroEL) and, to a lesser extent, DnaK (Hsp70) from M. tuberculosis bind to CD43.
• Cpn60.2 functions as a CD43-dependent mycobacterial adhesin for macrophage binding.
• The binding affinity between Cpn60.2 and CD43 is saturable and in the low micromolar range.
• Escherichia coli GroEL, but not mammalian Hsp60, competitively inhibits M. tuberculosis binding to CD43, suggesting conserved chaperone-mediated adherence.

Conclusions:

• Cpn60.2 is a key mycobacterial adhesin that utilizes CD43 on macrophages for bacterial attachment.
• CD43 may function as a Pattern Recognition Receptor (PRR) for extracellular bacterial chaperone proteins.
• This study highlights the extracellular roles of molecular chaperones in bacterial adherence and host immunity.