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Published on: December 19, 2020
Recombinant expression of Streptococcus pneumoniae capsular polysaccharides in Escherichia coli
Emily J Kay1, Laura E Yates1, Vanessa S Terra1
1Department of Pathogen Molecular Biology , London School of Hygiene and Tropical Medicine , Keppel Street, London WC1E 7HT , UK.
Insights
Researchers engineered E. coli to produce Streptococcus pneumoniae capsules, crucial for vaccines. This offers a cost-effective alternative to culturing the pathogen, improving vaccine accessibility.
Area of Science:
- Microbiology
- Vaccinology
- Synthetic Biology
Background:
- Streptococcus pneumoniae causes millions of pneumonia cases and deaths annually.
- The bacterial polysaccharide capsule determines serotype and is key for vaccines like PPV23 and PCV13.
- Current vaccine production relies on purified capsules, which is costly and limits global access.
Purpose of the Study:
- To develop a recombinant method for producing Streptococcus pneumoniae serotype-specific capsules.
- To identify the minimal gene set required for efficient heterologous capsule expression.
- To explore applications in vaccine production and synthetic glycobiology.
Main Methods:
- Recombinant expression of capsule-encoding loci from four S. pneumoniae serotypes in Escherichia coli.
- Identification of essential genes for heterologous capsule synthesis.
- Characterization of engineered E. coli strains for capsule production.
Main Results:
- Successfully demonstrated recombinant expression of S. pneumoniae capsules in E. coli.
- Identified key genes for efficient and reliable heterologous capsule production.
- Established E. coli strains capable of producing specific pneumococcal capsules.
Conclusions:
- Engineered E. coli provides a viable, non-pathogenic platform for producing S. pneumoniae capsules.
- This approach can reduce vaccine production costs and enhance accessibility, particularly in low-income regions.
- The developed strains have potential applications in recombinant vaccine development and synthetic glycobiology.
Abstract:
Currently, Streptococcus pneumoniae is responsible for over 14 million cases of pneumonia worldwide annually, and over 1 million deaths, the majority of them children. The major determinant for pathogenesis is a polysaccharide capsule that is variable and is used to distinguish strains based on their serotype. The capsule forms the basis of the pneumococcal polysaccharide vaccine (PPV23) that contains purified capsular polysaccharide from 23 serotypes, and the pneumococcal conjugate vaccine (PCV13), containing 13 common serotypes conjugated to CRM197 (mutant diphtheria toxin). Purified capsule from S. pneumoniae is required for pneumococcal conjugate vaccine production, and costs can be prohibitively high, limiting accessibility of the vaccine in low-income countries. In this study, we demonstrate the recombinant expression of the capsule-encoding locus from four different serotypes of S. pneumoniae within Escherichia coli. Furthermore, we attempt to identify the minimum set of genes necessary to reliably and efficiently express these capsules heterologously. These E. coli strains could be used to produce a supply of S. pneumoniae serotype-specific capsules without the need to culture pathogenic bacteria. Additionally, these strains could be applied to synthetic glycobiological applications: recombinant vaccine production using E. coli outer membrane vesicles or coupling to proteins using protein glycan coupling technology.
