Passive immunization by lactobacilli expressing single-chain antibodies against Streptococcus mutans

Area of Science:

• Microbiology
• Dental Research
• Biotechnology

Background:

• Streptococcus mutans is a primary cause of dental caries.
• SA I/II adhesin is a key virulence factor for S. mutans.
• Lactobacilli are being explored as delivery vehicles for therapeutic agents.

Purpose of the Study:

• To compare the anticariogenic efficacy of lactobacilli engineered to express single-chain variable fragments (scFv) targeting S. mutans SA I/II adhesin.
• To evaluate the impact of inducible versus constitutive promoters on scFv expression and therapeutic effect.

Main Methods:

• Engineered lactobacilli expressing scFv against S. mutans SA I/II adhesin were constructed using inducible and constitutive promoters.
• Bacterial agglutination assays were performed to confirm scFv binding to S. mutans.
• A rat caries model was used to assess the anticariogenic effect of the transformed lactobacilli over time.

Main Results:

• Both inducible and constitutive promoter systems resulted in similar scFv expression and S. mutans agglutination.
• Transformed lactobacilli were detected in the oral cavity throughout the study duration in the rat model.
• Lactobacilli with a constitutive promoter demonstrated slightly superior protection against caries compared to those with an inducible promoter.

Conclusions:

• Continuous in situ production of scFv by lactobacilli may be more effective for preventing dental caries than intermittent production.
• Engineered lactobacilli show promise as a delivery system for anticariogenic agents.
• The choice of promoter significantly influences the therapeutic potential of engineered probiotics.