65 kDa cell wall Antibody

Definition and Biological Context

The term "65 kDa cell wall antibody" broadly refers to monoclonal or polyclonal antibodies raised against 65 kDa proteins located in the cell walls or extracellular matrices of bacteria, fungi, or plants. These proteins often serve as virulence factors, structural components, or immunodominant antigens .

Bacterial Pathogens

• Mycobacterium tuberculosis:
  The 65-kDa antigen (also called HSP65) is a heat-shock protein critical for bacterial survival. Antibodies against this protein are detected in tuberculosis and leprosy patients .

  • Structure: Encoded by a 540-amino-acid gene with a downstream open reading frame (ORF) encoding a 517-amino-acid protein .

  • Immune Response: Triggers T-cell proliferation and antibody production in infected individuals .

Fungal Pathogens

• Candida albicans:
  The 65-kDa mannoprotein (MP65) is a fungal cell wall constituent critical for adhesion and immune evasion.

  • Biochemical Properties:

    • Composed of 54 kDa protein core with O-glycosylated mannose/glucose polysaccharides (12.7:1 ratio) .

    • Resistant to endoglycosidases H/F but sensitive to α-mannosidase .

  • Immunogenicity: Activates human peripheral blood mononuclear cells at nanogram doses .

Autoimmune Cross-Reactivity

The 65-kDa antigen of M. tuberculosis shares 47% sequence homology with the human mitochondrial P1 protein. Monoclonal antibodies against the bacterial antigen cross-react with the 63-kDa P1 protein in vertebrates, suggesting a mechanism for autoimmune diseases like rheumatoid arthritis .

Applications in Plant Biology

A monoclonal antibody targeting a 65-kDa plant membrane polypeptide (associated with callose synthase) has been used to study:

• Cation-dependent enzyme activity: The antibody immobilizes callose synthase in a cation-dependent manner .

• Subcellular localization: Binds sieve plates and plasmodesmata in cucumber and onion cells, sites of stress-induced callose deposition .

Table 1: Biochemical Characterization of 65-kDa Antigens

Key Studies

1. Immunoaffinity Purification: MP65 from C. albicans was isolated using monoclonal antibodies, revealing its role in adaptive immunity .

2. Gene Cloning: The M. tuberculosis 65-kDa antigen gene was sequenced, enabling recombinant protein production for diagnostic assays .

3. Cross-Reactivity Assays: Anti-65-kDa mycobacterial antibodies stained mitochondrial proteins in human cells, linking infections to autoimmunity .

Clinical and Biotechnological Implications

• Diagnostics: Used in ELISA and Western blot assays for tuberculosis and candidiasis .

• Therapeutic Targets: Antibodies against MP65 are being explored for antifungal vaccines .

• Autoimmunity Research: Serves as a model for studying molecular mimicry in rheumatoid arthritis .

Limitations and Research Gaps

• Species-Specific Variability: Structural differences in 65-kDa proteins across organisms complicate antibody cross-application.

• Functional Redundancy: Multiple isoforms (e.g., MAP65 family in plants) may obscure targeted studies .