Figure 4

Evaluation of mutations in nsP2 and E2. The plasmid prSAV3 was modified to express either serine or proline in E2₂₀₆ and either alanine or aspartic acid in nsP2₁₉₇. (A) Infectious viruses were recovered from all plasmids after transfection into BF2 cells. The variants expressing the nsP2_197A produced CPE in CHSE cells, while viruses expressing nsP2_{197 D} did not. The E2₂₀₆ mutation did not appear to affect CPE. Representative images of CPE are shown for each mutant. (B) The E2₂₀₆ mutation did not affect antigenicity of the E2 protein notably, since both the serine and proline mutants were readily detected by IFAT. (C) RT-PCR and sequencing of passage 3 of recombinant viruses confirmed that both the serine and the proline codons were stable.