GFP co-expression reduces the A33R gene expression driven by a fowlpox vector in replication permissive and non-permissive cell lines

► A new smallpox vaccine is required to protect from bioterrorism and OPV infection. ► Two fowlpox recombinants were prepared expressing the A33R gene of vaccinia virus. ► Fowlpox recombinants express correctly the transgene by real-time PCR, WB, and IF. ► GFP co-expression does not prevent but can reduce the levels of the A33R immunogen.