ABSTRACT
The limited efficacy of DNA vaccines against foot-and-mouth disease (FMD) in cattle and other natural hosts has prompted a search for a more effective vaccination regimen. In this study we tested a DNA prime-protein boost vaccination strategy against FMD in bovine calves. We used purified recombinant FMDV specific multi-epitope protein (rMEG990) and an optimized sindbis virus replicase-based DNA vaccine expressing this protein (pSinCMV-Vac-MEG990). We demonstrate that vaccination with a low dose of pSinCMV-Vac-MEG990 (10 µg/animal) and subsequently boosting with rMEG990 resulted in induction of neutralizing antibodies, IFN-γ production and protection against homologous virus challenge. However, vaccination with a high dose of pSinCMV-Vac-MEG990 (100 µg/animal) and boosting with rMEG990 resulted in significantly lower immune responses and more severity to the challenge test. Additionally, we show that the post-vaccinal IFN-γ levels in animals correlated positively to their protection against FMDV challenge. These findings suggest that a replicase-based DNA vaccine in proper prime-boost combination may offer an efficient vaccine strategy against FMDV and that IFN-γ could be used as an additional immune parameter to predict protection against FMDV infection.
Subject(s)
Foot-and-Mouth Disease Virus/immunology , Foot-and-Mouth Disease/prevention & control , Vaccines, DNA/immunology , Viral Vaccines/immunology , Animals , Antibodies, Neutralizing/blood , Antibodies, Viral/blood , Cattle , Cell Line , Cricetinae , DNA-Directed DNA Polymerase/metabolism , Epitopes/biosynthesis , Epitopes/immunology , Foot-and-Mouth Disease/immunology , Foot-and-Mouth Disease Virus/genetics , Interferon-gamma/blood , Male , Vaccination/standards , Vaccination/veterinary , Vaccines, DNA/genetics , Viral Vaccines/geneticsABSTRACT
BACKGROUND: Foot and mouth disease (FMD) can be controlled by regular vaccination and restriction of the movement of infected animals in the endemic countries. Although presently used, tissue culture inactivated vaccine gives protection, it has several limitations, including a short duration of immunity. DNA vaccine delivered through microparticles could comprise an alternative approach to conventional vaccine when aiming to circumvent these limitations. METHODS: We constructed the expression plasmid (pVAC-1D) containing 1D gene FMD virus serotype Asia 1. Poly(D,L-lactide-co-glycolide) (PLG) microparticles were prepared and coated with the pVAC-1D plasmid. Guinea pigs were vaccinated with PLG-coated and naked DNA vaccine constructs intramuscularly. The humoral response was measured by an enzyme-linked immunosorbent assay (ELISA) and the serum neutralization test (SNT). Analysis of the persistence and the expression of pVAC-1D plasmid construct was carried out by quantitative polymerase chain reaction (qPCR). RESULTS: The humoral response lasted for 1 year, as measured by ELISA and SNT. Analysis of the persistence and the expression of pVAC-1D plasmid construct by qPCR has shown that pVAC-1D expression was seen for a longer duration compared to the naked DNA vaccine. Microparticles coated plasmid DNA-injected guinea pigs were protected when challenged with FMD virus. CONCLUSIONS: The present study has shown that the delivery of plasmid coated on cationic PLG microparticles enhance the duration of immunity of the DNA vaccine constructs.
Subject(s)
Capsid Proteins/immunology , Foot-and-Mouth Disease , Genetic Vectors/administration & dosage , Immunity, Active/genetics , Vaccines, DNA , Animals , Capsid Proteins/genetics , Cell-Derived Microparticles/chemistry , Foot-and-Mouth Disease/genetics , Foot-and-Mouth Disease/therapy , Foot-and-Mouth Disease Virus/genetics , Foot-and-Mouth Disease Virus/immunology , Genetic Vectors/chemistry , Guinea Pigs , Injections, Intramuscular , Lactic Acid/chemistry , Lactic Acid/immunology , Polyglycolic Acid/chemistry , Polylactic Acid-Polyglycolic Acid Copolymer , Vaccines, DNA/administration & dosage , Vaccines, DNA/immunologyABSTRACT
Foot-and-mouth disease (FMD) is a highly contagious disease of cloven-hoofed animals causing considerable economic loss in the affected countries. The presently used tissue-cultured inactivated vaccine protects the vaccinated animals for a short duration of immunity. As one of the approaches to develop alternative vaccines, P12A3C-pcDNA (containing P12A and 3C coding sequences of foot-and-mouth disease virus) and bovine IL18 pcDNA plasmids were constructed and the immune response of these constructs was evaluated when they were coinoculated in guinea-pigs. The humoral response was analyzed using enzyme-linked immunosorbent assay (for levels of IgG1, IgG2) and a serum neutralization test (SNT), and the cellular response using an MTT assay. Significantly higher humoral and cell-mediated immune responses were seen in the P12A3C and the IL-18 coinoculated group than that in P12A3C-pcDNA alone and inactivated virus vaccine inoculated groups. Similarly, a higher population of CD4(+) , CD8(+) and T-helper type 1 (Th1), and Th2 cytokine levels were seen in the former group in comparison with the other groups. P12A3C+IL-18 protected all the six animals when challenged with a homologous virus compared with five and four in an inactivated virus vaccine and the P12A3C-pcDNA groups, respectively. These results have shown that the plasmid encoding for P12A3C-pcDNA, when coinoculated with IL-18, induced higher responses and protected the animals from a virus challenge.
