Figure 1. Properties of the vaccine and wild-type strains.

(A) Representative photographs of viral plaques (left) and their corresponding plaque sizes in BHK-21 cells (right). (B) Plaque assay titres (left) and focus forming assay titres (right) of viral inoculum diluted to 10MOI (1 × 10⁵ per mL) for cell culture experiments, confirming that all strains have the same inoculum titres, and that the PFU and FFU titres corresponded to each other. (C) Cell-to-cell spread of virus in HuH-7 cells as measured by flow cytometry. At 24 hpi, 1MOI of PDK53 infected 10% of cells, approximately 10-fold more than 1MOI of 16681 (1%). Proportion of cells infected with PDK53 (0.1MOI) was similar to those infected with 16681 (1MOI) at 24 hpi although the latter overtook the former by day 4 of infection (left). In contrast, PGMK30 did not spread as rapidly as 16562 (right). (D) Viral RNA replication in HuH-7 cells as measured by qPCR in the first 24 hours of infection. At the earliest time point, 3 hpi, 10MOI of PDK53 produced significantly more viral RNA than 10MOI of 16681. Viral RNA levels were balanced with 16681 (10MOI) when PDK53 was infected at 1MOI. When starting levels of viral RNA are balanced, PDK53 replicated more rapidly than 16681 in the first 24 hours of infection (left). PGMK30 and 16562 replicated at the same rate (right).