Immune Response Elicited by DNA Vaccination Using Lactococcus lactis Is Modified by the Production of Surface Exposed Pathogenic Protein

Daniela Pontes,Vasco Azevedo,Philippe Langella,Marie-Pierre Chapot-Chartier,Silvia Innocentin,Jean-Marc Chatel,Sébastien Blugeon,Pascal Courtin,François Lefévre,Marcela Azevedo,Anderson Miyoshi,Marie-Joelle Virolle

doi:10.1371/journal.pone.0084509

Abstract

In this study, we compared immune responses elicited by DNA immunization using Lactococcus lactis or L. lactis expressing the Staphylococcus aureus invasin Fibronectin Binding Protein A (FnBPA) at its surface. Both strains carried pValac:BLG, a plasmid containing the cDNA of Beta-Lactoglobulin (BLG), and were designated LL-BLG and LL-FnBPA+ BLG respectively. A TH2 immune response characterized by the secretion of IL-4 and IL-5 in medium of BLG reactivated splenocytes was detected after either oral or intranasal administration of LL-FnBPA+ BLG. In contrast, intranasal administration of LL-BLG elicited a TH1 immune response. After BLG sensitization, mice previously intranasally administered with LL-BLG showed a significantly lower concentration of BLG-specific IgE than the mice non-administered. Altenatively administration of LL-FnBPA+ BLG didn't modify the BLG-specific IgE concentration obtained after sensitization, thus confirming the TH2 orientation of the immune response. To determine if the TH2-skewed immune response obtained with LL-FnBpA+ BLG was FnBPA-specific or not, mice received another L. lactis strain producing a mutated form of the Listeria monocytogenes invasin Internalin A intranasally, allowing thus the binding to murine E-cadherin, and containing pValac:BLG (LL-mInlA+ BLG). As with LL-FnBPA+ BLG, LL-mInlA+ BLG was not able to elicit a TH1 immune response. Furthermore, we observed that these difference were not due to the peptidoglycan composition of the cell wall as LL-FnBPA+ BLG, LL-mInlA+ BLG and LL-BLG strains shared a similar composition. DNA vaccination using LL-BLG elicited a pro-inflammatory TH1 immune response while using LL-FnBPA+ BLG or LL-mInlA+ BLG elicited an anti-inflammatory TH2 immune response.

Highlights

An innovative strategy using Lactococus lactis, a food grade bacterium, to deliver plasmids in vitro [1] and in vivo [2] was previously developed by our laboratory
We reported previously that oral administration of LL-mInlA+ BLG or LLFnBPA+ BLG will elicit the production of BLG in mice enterocytes [10,11].Differences between immune responses observed after mucosal administration of invasive and non invasive strains were not due to a difference in peptidoglycan composition
In order to know if the production of Fibronectin Binding protein A (FnBPA) at the surface of L. lactis could influence its immunomodulatory properties, mice were orally or intranasally administered with LL-wt, LL-BLG or LL-FnBPA+ BLG strains and the BLG specific primary immune response was monitored

Summary

Introduction

An innovative strategy using Lactococus lactis, a food grade bacterium, to deliver plasmids in vitro [1] and in vivo [2] was previously developed by our laboratory. To better understand the mechanism of plasmid transfer and possibly improve on it, we developed invasive L. lactis strains by expressing invasins on their cell surface. We previously constructed LL-FnBPA+, a recombinant L. lactis strain expressing Staphylococcus aureus Fibronectin Binding protein A (FnBPA) on its surface and demonstrated its potential for plasmid. A recombinant L. lactis strain producing Listeria monocytogenes Internalin A (LL-InlA+) was constructed and demonstrated to be capablefor plasmid transfer in vivo with guinea pigs [7]. As InlA binds only poorly to murine E-cadherin, the use of this strain is thereby limited to either transgenic mice expressing human E-cadherin [8] or guinea pigs. We produced mutated mInlA at the surface of L. lactis (LL-mInlA+) and showed that LL-mInlA+ did not significantly increase plasmid transfer rate in mice [10]

Methods

Results

Conclusion