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Oral vaccination against enteric bacterial infections: an overview
Abstract:
The present situation and the future prospects for the use of oral vaccines against the major enteric diseases typhoid fever, shigellosis and cholera are discussed in this paper. No significant protection could be demonstrated for oral inactivated whole-cell vaccines. In contrast, an oral live vaccine based on the attenuated Salmonella typhi strain Ty 21a was highly efficacious in volunteer challenge studies and in a controlled field trial. Two attenuated strains are presently being tested in volunteer studies as candidate vaccines against shigellosis; one uses S. typhi Ty 21a and the other Escherichia coli K-12 as the carrier for shigella antigens. Experimental challenge studies in volunteers showed that recovery from clinical cholera confers solid and long-lasting protection. The goal of present research is to develop a vaccine that mimics the events of clinical cholera without causing disease.
Insights
Oral vaccines show promise for enteric diseases like typhoid and cholera. Live attenuated Salmonella typhi strain Ty 21a demonstrated high efficacy, offering hope for effective disease prevention.
Area of Science:
- Vaccinology
- Infectious Diseases
- Microbiology
Background:
- Enteric diseases such as typhoid fever, shigellosis, and cholera pose significant global health challenges.
- Current vaccine strategies for these diseases are under continuous development and evaluation.
Purpose of the Study:
- To review the current status and future potential of oral vaccines against major enteric pathogens.
- To assess the efficacy of different oral vaccine candidates for typhoid fever, shigellosis, and cholera.
Main Methods:
- Evaluation of oral inactivated whole-cell vaccines.
- Assessment of an oral live vaccine based on the attenuated Salmonella typhi strain Ty 21a.
- Review of ongoing research involving attenuated strains for shigellosis and cholera vaccine development.
Main Results:
- Oral inactivated whole-cell vaccines showed no significant protection against enteric diseases.
- The oral live vaccine utilizing Salmonella typhi strain Ty 21a proved highly efficacious in challenge studies and field trials.
- Recovery from clinical cholera confers long-lasting protection, guiding future vaccine design.
Conclusions:
- Live attenuated oral vaccines, particularly Salmonella typhi Ty 21a, represent a promising approach for preventing typhoid fever.
- Further research is focused on developing safe and effective oral vaccines for shigellosis and cholera.
- Mimicking natural immunity without causing disease is a key goal for cholera vaccine development.