Large envelope glycoprotein and nucleocapsid protein of equine arteritis virus (EAV) induce an immune response in Balb/c mice by DNA vaccination; strategy for developing a DNA-vaccine against EAV-infection.

The given research examines the potential for developing a DNA vaccine to protect horses against the Equine arteritis virus (EAV). The researchers cloned the virus’s genetic material into various expression vectors and then evaluated the immune responses in mice after they’d been given this restructured DNA.

Objective of the Research

• The main goal of this study was to assess the feasibility of creating a preventative measure against EAV infection, specifically a model system for a DNA vaccine. EAV is a contagious infection that affects horses, transmitted through the respiratory or reproductive tract, and developing a vaccine could significantly reduce its spread.

Method of Research

• A cDNA bank, a repository of EAV’s RNA, was created. This bank encompasses the translation units from the virus’s open reading frames (ORFs) 1 through 7. The resultant cDNA’s identity was then validated through nucleotide sequence analysis.
• The cDNA from the virus’s ORFs were then molecularly cloned into several well-characterized expression vectors such as pCR3.1, pDisplay, and pcDNA3.1/HisC. These recombinant plasmids opened the pathway for expressing the gene products of the individual viral ORFs.
• The study then moved into its examination phase, where the researchers evaluated whether these newly formed plasmids could initiate an immune response. This was done using ten Balb/c mice in each assay, which were inoculated with the DNA of the expression vectors containing and expressing the EAV cDNA.
• Inoculation was done by injecting about 100 microg of DNA, diluted in 100 microl of PBS, subcutaneously and into the tibialis cranialis muscle. The DNA was administered to the mice multiple times (3 to 5), in the same quantity at approximately two-week intervals. For control purposes, other mice received similar doses of the original, unchanged expression vectors.
• Pre- and post-vaccination, the individual mice’s sera were screened by conducting neutralization tests (NTs).

Conclusions Reached

• Neutralizing antibodies against EAV were detected in mice inoculated with the DNA of the expression vectors containing EAV cDNA of ORFs 5 and 7.
• The highest NT-titers were seen when the animals were given the cDNA of ORF 5 and/or with the cDNA of the neutralizing parts of EAV that resides on the N-terminal ectodomain of the gene product of ORF 5 between the amino acid positions 1-121.
• Based on these findings, the study concluded that the EAV cDNA sequences, especially of the viral genes including ORFs 5 and 7, proved capable of inducing an immune response in the mice, suggesting that this approach might work in horses as well.