PhoE protein as a carrier for foreign epitopes

Area of Science:

• Microbiology
• Immunology
• Biotechnology

Background:

• The outer membrane protein PhoE of Escherichia coli (E. coli) is a potential candidate for displaying foreign antigens on bacterial surfaces.
• Understanding the limits and effects of foreign peptide insertion into PhoE is crucial for developing novel vaccine strategies.

Purpose of the Study:

• To evaluate the suitability of E. coli outer membrane protein PhoE as a carrier for surface-expressed foreign antigenic determinants.
• To determine the capacity and impact of inserting amino acid stretches into PhoE on protein biogenesis, antigenicity, and immunogenicity.

Main Methods:

• Engineered E. coli PhoE by inserting foreign amino acid sequences into its cell-surface exposed loops.
• Assessed the effect of insertions on PhoE protein biogenesis and stability.
• Evaluated the antigenicity and immunogenicity of the inserted epitopes in the PhoE-associated conformation.

Main Results:

• Insertion of amino acid stretches into PhoE did not impede its biogenesis.
• Up to 50 amino acids could be inserted, depending on the loop and amino acid characteristics.
• Both B-cell and T-cell epitopes retained their antigenicity and immunogenicity.
• Flanking amino acids could potentially interfere with the antigenicity/immunogenicity of T-cell epitopes.

Conclusions:

• E. coli PhoE is a viable carrier for surface expression of foreign antigenic determinants.
• PhoE-based vaccine carriers can be expressed in attenuated Salmonella and Shigella strains, enhancing their potential as vaccine candidates.