A live attenuated Salmonella Enteritidis secreting detoxified heat labile toxin enhances mucosal immunity and confers protection against wild-type challenge in chickens.

Jonathan Lalsiamthara,Nitin Machindra Kamble,John Hwa Lee

doi:10.1186/s13567-016-0348-7

Jonathan Lalsiamthara, Nitin Machindra Kamble + Show 1 more

Open Access

https://doi.org/10.1186/s13567-016-0348-7

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Journal: Veterinary Research	Publication Date: Jun 4, 2016
Citations: 43	License type: cc-by

Affiliation: Jeonbuk National University

Abstract

A live attenuated Salmonella Enteritidis (SE) capable of constitutively secreting detoxified double mutant Escherichia coli heat labile toxin (dmLT) was developed. The biologically adjuvanted strain was generated via transformation of a highly immunogenic SE JOL1087 with a plasmid encoding dmLT gene cassette; the resultant strain was designated JOL1641. A balanced-lethal host-vector system stably maintained the plasmid via auxotrophic host complementation with a plasmid encoded aspartate semialdehyde dehydrogenase (asd) gene. Characterization by western blot assay revealed the dmLT subunit proteins in culture supernatants of JOL1641. For the investigation of adjuvanticity and protective efficacy, chickens were immunized via oral or intramuscular routes with PBS, JOL1087 and JOL1641. Birds immunized with JOL1641 showed significant (P ≤ 0.05) increases in intestinal SIgA production at the 1st and 2nd weeks post-immunization via oral and intramuscular routes, respectively. Interestingly, while both strains showed significant splenic protection via intramuscular immunization, JOL1641 outperformed JOL1087 upon oral immunization. Oral immunization of birds with JOL1641 significantly reduced splenic bacterial counts. The reduction in bacterial counts may be correlated with an adjuvant effect of dmLT that increases SIgA secretion in the intestines of immunized birds. The inclusion of detoxified dmLT in the strain did not cause adverse reactions to birds, nor did it extend the period of bacterial fecal shedding. In conclusion, we report here that dmLT could be biologically incorporated in the secretion system of a live attenuated Salmonella-based vaccine, and that this construction is safe and could enhance mucosal immunity, and protect immunized birds against wild-type challenge.

Highlights

Salmonella enterica serovar Enteritidis is one of the most frequently isolated bacteria from human infections worldwide [1]
To improve the vaccinebiological adjuvant system and to surpass the multistep processing of double mutant Escherichia coli heat labile toxin (dmLT)-conjugations, we investigated the use of a highly immunogenic live attenuated Salmonella Enteritidis (SE) strain that secretes dmLT adjuvant molecules constitutively as a vaccine candidate
The ability of Salmonella to evade killing by phagocytic cells and its pan tropism towards a variety of non-phagocytic cells leads to massive bacterial replication, resulting in high bacterial loads and systemic Salmonella infection [27]

Summary

Introduction

Salmonella enterica serovar Enteritidis is one of the most frequently isolated bacteria from human infections worldwide [1]. Meat and meat products are the most common transmission vehicles of Salmonella infections [3]. Due to the ubiquitous presence and rapid spread of Salmonellae in poultry premises, enforcing control measures can be expensive and. The heat-labile enterotoxin (LT) of E. coli is a potent oral adjuvant boosting both the humoral and cellular immune responses when co-administered with antigens. It induces secretory diarrhea, even at low doses [7, 8]. The usefulness of native LT as an adjuvant is eclipsed by its toxicity

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Conclusion