Generation of a candidate live marker vaccine for equine arteritis virus by deletion of the major virus neutralization domain.

The researchers have produced a live candidate marker vaccine for equine arteritis virus (EAV), by removing a crucial area of the virus that stimulates immune responses. However, the deletion doesn’t compromise the vaccine’s effectiveness, suggesting that another immune mechanism provides protection against infection. The modified virus could help differentiate between vaccinated and wild-type virus-infected animals.

Introduction to the Research

• The focus of the research lies in the development of a vaccine for the equine arteritis virus (EAV), a perpetrator of respiratory and reproductive diseases amongst horses. This virus belongs to the Arteriviridae family of viruses in the order of Nidovirales.
• Previously, a peptide enzyme-linked immunosorbent assay (ELISA) was developed, which effectively detected EAV presence owing to the virus-neutralizing antibodies targeting a dominant region of EAV – the G(L) domain.

Research Methodology

• The researchers utilized an infectious cDNA to create a mutant EAV that lacked the immunodominant G(L) domain. This manipulated virus expressed regular titers in cultured cells, but at a slower rate and caused no symptoms when introduced to ponies.
• The antibodies produced in response to this mutant virus effectively neutralized it in vitro but showed limited efficacy against wild-type strains of EAV.
• The researchers further exposed the vaccinated ponies to the more virulent strains of EAV and found these animals to be fully protected against disease, with only brief, low levels of viral replication noted. This protection level hints at the presence of an immune effector mechanism that provides protection against infection beyond the neutralization by antibodies.

Implications and Conclusion

• Interestingly, the infection with the mutant EAV (EAV-G(L)Delta) did not induce a measurable response in the G(L) peptide-based ELISA. However, the EAV infection did show a clear reaction in the same ELISA, enabling researchers to distinguish between vaccinated and wild-type virus-infected animals.
• Therefore, the researchers propose mutant viruses like EAV-G(L)Delta as promising marker vaccine candidates that facilitate distinguishing between vaccinated and infected animals – an essential feature for disease control and eradication strategies.