Figure 3: Growth curves of BAC-derived viruses and viruses derived from the vaccine. MRC-5 cultures were infected at MOIs of 0.1 (left) and 0.05 (right) with the vaccine virus mixture (Towne mix), varS, or varL viruses isolated from the vaccine and BAC-derived viruses lacking (-cre) or containing the BAC ori. Titers of each virus in the culture supernatants were determined on the days indicated.