# An Oral Vaccine Derived from Attenuated Salmonella Producing Murine Cytomegalovirus M24 Protein Induces Successful Antiviral Immune Responses in Mice

## TL;DR

A new oral vaccine using weakened Salmonella bacteria that produces a CMV protein successfully boosts antiviral immunity in mice.

## Contribution

Development of a novel attenuated Salmonella strain expressing MCMV M24 protein as an effective oral vaccine candidate.

## Key findings

- The S713 strain was 500,000 times less lethal than a clinical Salmonella strain in mice.
- Vaccination with S713 boosted anti-MCMV IgA, IgG, and T cell responses in mice.
- Immunized mice showed suppressed MCMV replication and increased survival after challenge.

## Abstract

Background: Oral gene delivery vectors, such as those derived from attenuated Salmonella strains, have shown great promise in oral vaccine development against various human diseases. Human cytomegalovirus (CMV) is a herpesvirus capable of affecting the global population and establishing lifelong infection. Generation of an anti-CMV vaccine is a major public health priority. Methods: This study reports the development of a novel weakened Salmonella strain, S713, and the effects of this strain as an oral vaccine candidate against murine cytomegalovirus (MCMV) infection in mice. Results: The weakened Salmonella strain S713 was attenuated in killing mice in vivo by >500,000 fold compared to a clinical strain, following intragastric instillation in animals. Mice intragastrically immunized with S713 that produced MCMV M24 protein exhibited elevated anti-MCMV mucosal IgA and serum IgG titers and enhanced anti-MCMV T cell responses. Moreover, immunization with the generated vaccine in MCMV-challenged mice not only suppressed viral replication in lungs, spleens, livers, and salivary glands but also increased animal survival. Conclusions: These findings demonstrate strong and effective anti-MCMV immune responses induced by the generated M24-expressing vaccine. Furthermore, our results reveal the promising capability of weakened strain S713 expressing different CMV proteins to act as oral vaccines against CMV infections and diseases.