Figure 3.

Reverse-genetics method for generating segmented, negative-sense RNA viruses entirely from cloned cDNA. Plasmids containing the RNA polymerase I promoter, a cDNA for each of the eight viral RNA segments, and the RNA polymerase I terminator are transfected into cells together with protein expression plasmids. Although infectious viruses can be generated with plasmids expressing PA, PB1, PB2, and NP, expression of all remaining structural proteins (shown in brackets) increases the efficiency of virus production (see text).