Adjuvant Effects of L. acidophilus LW1 on Immune Responses to the Foot-and-Mouth Disease Virus DNA Vaccine in Mice

Junhong Su,Yongxi Dou,Yanan You,Xuepeng Cai,Xueqiang Li,Xusheng Ma,Xuenong Luo,Haixue Zheng,Jidong Li,Junjun Li,Yungang Li,Ding Xiang Liu

doi:10.1371/journal.pone.0104446

Abstract

The adjuvant effects of Lactobacillus acidophilus on DNA vaccination are not fully understood. It has been hypothesized that swine-derived Lactobacillus acidophilus SW1 (LASW1) could function as an immune adjuvant to enhance antigen-specific immune responses after foot-and-mouth disease (FMD) DNA vaccination in mice. To evaluate the effect of oral LASW1 on the immune response to a DNA vaccine (pRC/CMV-vp1) harboring FMD VP1 gene, anti-FMDV antibody and its isotypes, T-cell proliferation, and cytokine detection were investigated. The results showed that LASW1 was able to enhance FMDV-specific antibody levels and FMDV-neutralizing antibodies. After a booster vaccine, the anti-FMDV antibody titers and FMDV-neutralizing antibodies levels induced by pRC/CMV-vp1 were higher in mice treated with LSAW1 than in the group immunized with pRC/CMV-vp1 alone (the control). Using T-cell proliferation, the stimulation index of the LASW1 group was significantly higher in response to ConA and 146S antigen (P<0.05) than in the control group. Importantly, higher concentrations of IFN-γ and IFN-γ-producing cells were also observed in splenocytes isolated from the experimental LASW1 mice, indicating that INF-γ secretion is important to the immune response to LASW1. The results indicate that LASW1 is a promising immune adjuvant in DNA vaccination against FMD when administrated orally.

Highlights

Foot-and-mouth disease (FMD) is one of the most contagious and economically devastating viral diseases of cloven-hoofed livestock worldwide
The results demonstrated that pRc/CMV-VP1 can express footand-mouth disease virus (FMDV) VP1 protein in BHK cells
These data indicate that oral L. acidophilus SW1 (LASW1) can improve the antigen-specific humoral response in mice immunized with pRC/ CMV-VP1

Summary

Introduction

Foot-and-mouth disease (FMD) is one of the most contagious and economically devastating viral diseases of cloven-hoofed livestock worldwide. The causative agent of FMD is the footand-mouth disease virus (FMDV). It has a single-stranded, plussense RNA genome of approximately 8500 bases surrounded by four structural proteins. DNA vaccines have elicited protective immune responses against a variety of pathogenic agents, including HIV, influenza, FMDV, and tumor cells [4,5,6,7]. Despite this progress, DNA vaccines often generate weak immune responses, resulting in either partial protection or failure [8,9,10]. Cytokines and co-stimulatory molecules are potential adjuvants and may improve the efficacy of DNA vaccines [11,12]

Methods

Results

Conclusion