Fig 1.

(A) Generation and characterization of recombinant PVM expressing the LCMV-derived CTL epitope gp33 fused to GFP. Shown are the GFPgp33 gene cassette and its placement into the PVM genome. The sequence encoding LCMV gp29-43 was fused to the C terminus of GFP. The cassette represents a PVM pseudogene encoding a single open reading frame for expression of a GFP-gp33 fusion protein flanked by PVM-specific transcriptional start (gene start) and stop (gene stop) sequences. (B) Multistep growth curve of rPVM-GFPgp33 in comparison to the recombinant parental virus rPVM-GFP and its parental wild-type PVM15. BHK-21 cells were infected with the respective viruses (multiplicity of infection of 0.01 PFU/cell) at day 0. Cells and supernatants were harvested in duplicates at the indicated time points, and virus titers were determined by plaque assay. The growth kinetics were determined twice, with similar results. (C) C57BL/6 mice were intranasally infected with 100 to 200 PFU of the indicated PVM isolate, and virus titers were determined in the lung at the indicated time points after infection. n.s., not significant; **, P < 0.05. (D) Mice were weighed prior to infection and daily thereafter. The percentage (mean ± SD) of the initial weight is indicated for 3 to 20 mice per time point. ***, significant differences between PVM15- and rPVM-GFPgp33-infected groups and between PVM15- and rPVM-GFP-infected groups.