Expression of ORF 7b. (A) Detection of ORF 7b-flag expression with an anti-flag antibody by Western blot analysis. The 10 kD band is non-specifically detected in all samples. (B) Vero cells were infected with the flag-tagged recombinant virus rSCV7bflag or with the recombinant virus rSCV and subjected to IFA at 24 h p.i. IFA was done with anti-flag antibody (left panel, anti-flag) or a convalescent patient serum reacting predominantly against the SARS-CoV nucleocapsid protein (right panel, anti N).