Mutant bacteriophage with non-catalytic endosialidase binds to both bacterial and eukaryotic polysialic acid and can...

Area of Science:

• Microbiology
• Neuroscience
• Biochemistry

Background:

• Polysialic acid (PSA) is a key virulence factor in bacterial pathogens like E. coli K1, causing sepsis and meningitis.
• PSA on bacteria mimics carbohydrate units of neural cell adhesion molecule (NCAM), crucial for neural development.
• This molecular mimicry complicates host immune responses and pathogen detection.

Purpose of the Study:

• To investigate bacteriophage mutants with disabled endosialidase for binding to bacterial and eukaryotic PSA.
• To determine if these mutants can serve as probes for detecting PSA in biological samples.
• To explore the potential of these phages in diagnostics for PSA-related conditions.

Main Methods:

• Development of catalytically disabled endosialidase bacteriophage mutants.
• Nitrocellulose dot blot assays to assess binding to PSA-containing bacteria (e.g., E. coli K1, Neisseria meningitidis).
• Western blot analysis to evaluate binding to embryonic and adult NCAM.
• Fluorescence and light microscopy for visualizing PSA in cultured cells and tissue sections.

Main Results:

• Mutant phages specifically bound to PSA-expressing bacteria and not wild-type phages.
• A minimum of 10 sialyl residues were required for effective binding.
• Mutant phages recognized the embryonic, highly sialylated form of NCAM but not the adult, less sialylated form.
• Successful application of mutant phages as probes in microscopy for detecting eukaryotic PSA.

Conclusions:

• Catalytically disabled bacteriophage mutants are effective tools for recognizing and binding bacterial and eukaryotic PSA.
• These phages specifically target the molecular mimicry between bacterial PSA and NCAM.
• Mutant phages offer a novel approach for detecting PSA in host tissues, with potential applications in diagnosing infections and neurological conditions.