Rescue of disabled infectious single-cycle (DISC) Equine arteritis virus by using complementing cell lines that express minor structural glycoproteins

Equine arteritis virus (EAV) contains seven structural proteins that are all required to produce infectious progeny. Alphavirus-based expression vectors have been generated for each of these proteins to explore the possibilities for their constitutive expression in cell lines. This approach was successful for minor glycoproteins GP(2b), GP(3) and GP(4) and for the E protein. Subsequently, it was demonstrated that cell lines expressing these proteins could rescue EAV mutants that were disabled in the expression of the corresponding gene, resulting in the production of virus particles carrying the mutant genome. This system was particularly efficient for GP(2b)- and GP(4)-knockout mutants. Upon infection of non-complementing cells with these mutants, a self-limiting single cycle of replication was initiated, resulting in the expression of all but one of the viral proteins. These disabled infectious single-cycle (DISC) arteriviruses can also be used to express foreign sequences and are potentially useful in both fundamental research and vaccine development.