Conserved arginine residues in the carboxyl terminus of the equine arteritis virus E protein may play a role in heparin binding but may not affect viral infectivity in equine endothelial cells.

The research explores the role of the Equine Arteritis virus (EAV) E protein in binding with heparin and its impact on the virus’ infectivity among equine endothelial cells. The study reveals that heparin contributes to EAV infection but isn’t the only crucial factor for EAV infection.

Research Background and Aim

• The study pivots around Equine arteritis virus (EAV), the pathogen that causes equine viral arteritis.
• The virus replicates primarily in a horse’s macrophages and endothelial cells of small blood vessels, showing a fairly broad cell tropism in vitro.
• Before this research was conducted, the specific cellular receptor(s) and the mechanism(s) of virus attachment and entry had not been fully determined.
• The aim of the study was to examine the role of heparin on EAV infection within equine endothelial cells (EECs).

Methodology and Findings

• Heparin, among other glycosaminoglycans, was found to reduce EAV infection by up to 93%.
• Sequence analysis of the EAV E minor envelope protein showed a consistent amino acid sequence at the carboxy terminus of the E protein. This sequence was predicted to be the heparin-binding domain.
• The researcher mutated the basic arginine (R) amino acid residues to glycine using site-directed mutagenesis of ORF2a. Two single mutations (R52G and R57G) did not affect the heparin-binding ability, but a double mutation(R52,60G) completely nullified the interaction between the E protein and heparin.

Conclusion and Implications

• Despite the absence of heparin-binding in the mutant R52,60G EAV, the virus could still infect, which implies that heparin isn’t the sole element for EAV infection.
• This raises the possibility of other viral envelope protein(s) or other cell-surface molecules involvement in attachment, necessitating further research in this direction.