E.coli: The ideal transport medium for modern-day vaccines?

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Researchers at University at Buffalo recently showed the role of harmless E. coli as effective agents in the delivery of a pneumococcal vaccine. Pneumococcal disease, caused by Streptococcus pneumoniae (S. pneumoniae), refers to infections that can lead to pneumonia, sepsis, middle ear infection and meningitis.

They developed an E. coli-based transport capsule designed to help next-generation vaccines do a more efficient and effective job than today’s immunizations.

Unlike the traditional vaccines, this new ‘hybrid capsule’ is a cocktail of E. coli cell wall components combined with a synthetic polymer, beta amino ester. Interestingly, this vaccine was shown to be more potent than traditional ones in preventing infections against pneumococcal disease.

Researchers have developed an E. coli-based transport capsule, designed to help next-generation vaccines do a more efficient and effective job than today’s immunizations. Credit: University at Buffalo.
Researchers have developed an E. coli-based transport capsule, designed to help next-generation vaccines do a more efficient and effective job than today’s immunizations. Credit: University at Buffalo.

E.coli as a vehicle for pneumococcal vaccine?

A number of diseases that were common in the early days such as polio, diphtheria, whooping cough are now easily prevented by vaccination. Vaccination elicits an immune response against the injected protein thus providing protection against the disease-causing agent. Over the past several years, a lot of effort has been put on understanding the mechanism by which immune cells respond to different antigenic substances in the vaccine. This will help in modifying existing vaccines so as to make them more effective. Especially for diseases that do not yet have a cure, development of such potent vaccines will prove to be extremely valuable.

One such modified vaccine against pneumococcal disease was used by Dr. Pfeifer’s group at Buffalo, NY. Researchers showed that using harmless E coli in combination with a chemical polymer to deliver pneumococcus antigen serves as a potent vaccine against this disease.

What makes E coli a choice for a carrier molecule? It is a less known fact that apart from infectious strains, various other harmless strains of E coli are normal inhabitants of the gut. In fact many of them aid in our daily digestive processes.

The researchers have used one such harmless strain as delivery vector for this vaccine. E coli is a type of gram-negative bacteria possessing negatively charged components in the cell wall. These components wrapped by positively charged synthetic polymer of amino ester was used to form a hybrid, yet potent antigenic capsule.

The core of the transport capsule is harmless E. coli. A synthetic polymer — poly (beta amino ester), or PBAE — wraps around the bacteria. The positive-charged polymer, combined with the negative-charged bacteria cell wall, create a hybrid capsule. Credit: University at Buffalo.
The core of the transport capsule is harmless E. coli. A synthetic polymer — poly (beta amino ester), or PBAE — wraps around the bacteria. The positive-charged polymer, combined with the negative-charged bacteria cell wall, create a hybrid capsule. Credit: University at Buffalo.

When this capsule was used to inject the pneumococcal antigen in mice, improved immune responses were obtained as compared to those using traditional vaccine formulations. Interestingly, the hybrid design of the capsule triggers the immune cells of the body via more than one pathway. The composition of this capsule provides not only an enhanced immune response but also a stronger protective effect persisting for a significantly longer duration, an effect not observed by other traditional delivery agents. In addition, manufacturing and using such capsules are relatively easy and extremely cost effective.

In short, this work stands as a key discovery in the field of vaccine development enabling the future use of this capsule not only as a preventive measure but also for delivery of therapeutics in various diseased conditions.

Original paper can be accessed here.