the method of making this antisera and even a biotinylated or labeled antisera is well known to those of ordinary skill in the art when the virus is vaccinia vp53 containing influenza ha gene inserted in the hind iii f portion of the viral genome the cells infected with progeny virions are detected by detecting the influenza hemagglutinin surface protein using a cytofluorograph moreover the expression of influenza hemagglutinin gene occurs early during infection and the antigen is inserted into the infected cell 39 s membrane thus infected cells will express a surface antigen that is not expressed in uninfected cells or cells infected with mutant virions the antigen can be identified by specific fluorescently labeled antisera the antisera can be biotinylated antisera or a second antibody specific to this antisera and which is conjugated to biotin can be added to the cell culture such an antibody can be purchased from vector labs the resulting complex is stained by the addition of avidinfluorescein this system preserves the initial recognition of the virus antigen but amplifies the number of fluorescein molecules approximately ten times over the fluorescent anti sera the quantitation of fluorescent cells infected is accomplished with a cytofluorograph the cytofluorograph detects fluorescence of individual cells for example a facs iv cytofluorograph made by becton dickinson can be used this instrument is equipped with a mercury arc lamp that.