FIG. 5.

Proline-rich region is not important for CVB3 growth. (A) Effect of the indicated 3A mutations on virus growth. Mutations were introduced into the infectious cDNA clone p53CB3/T7. Copy RNA transcripts were transfected into BGM cells and examined for the ability to yield viruses. All mutations resulted in viable viruses except the P17A/P18A/P19A mutations, which caused a quasi-infectious (q.i.) phenotype. (B) Single-cycle growth analysis of mutant viruses. BGM cells were infected at an MOI of 1 and incubated at 37°C. At 2, 4, 6, or 8 h postinfection, viruses were released from the infected cells by three cycles of freezing and thawing. Virus titers were determined by titration on BGM cells and expressed in TCID₅₀ values.