Limited expression of poliovirus by vaccinia virus recombinants due to inhibition of the vector by proteinase 2A.

A recombinant vaccinia virus was constructed that expressed poliovirus coat precursor protein P1 fused to about two-thirds of the 2A proteinase. The truncated 2A segment could be cleaved away from the P1 region by coinfecting with poliovirus type 1, 2, or 3 or with human rhinovirus 14 but not with encephalomyocarditis virus. Further cleavage of the vector-derived P1 to yield mature poliovirus capsid proteins was not observed. Attempts to isolate vaccinia virus recombinants containing portions of the poliovirus genome that encompassed the complete gene for proteinase 2A were unsuccessful, unless expression of functional 2A was abolished by insertion of a frameshift mutation. We conclude that an activity of the 2A proteinase, probably its role in translational inhibition, prevented isolation of vaccinia virus recombinants that expressed 2A.