Fig. 1. MuHV-4 infection via footpad inoculation. (a) BALB/c mice were infected i.f. with luciferase-expressing MuHV-4 (MHV-LUC; 105 p.f.u.). Infection was monitored by intraperitoneal (i.p.) luciferin injection and charge-coupled device camera scanning of light emission. Representative images are shown at days 1 and 9 of infection. Abdominal signals at day 9 came from the spleen. (b) Quantification of live imaging for mice given MHV-LUC (105 p.f.u.) either i.f. (footpad signals) or i.n. (nose signals), showing the comparative signal strengths and kinetics of infection. ○, Individual mice; × , means. Footpad signals were significantly higher than nose signals at days 1–5 (P < 0.01), but not at days 7–11 (P >0.05). (c) To identify the sources of live imaging signals, mice were infected i.f. with MHV-LUC as in (a) and then dissected at each time point to image the relevant organs ex vivo. Footpads and PLNs were positive from day 1, whereas most spleens and para-aortic LNs were positive only from day 3. The y-axis baseline corresponds to the lower limit of assay sensitivity. (d) BALB/c mice were infected i.n. or i.f. with MHV-LUC as in (b). After 5 days, footpads, (i.f. infection) and noses (i.n. infection) were compared for infectious virus titre by plaque assay. After 9 days, PLNs (i.f. infection) and SCLNs (i.n. infection) were compared for total recoverable virus titre by infectious centre assay. Titres were higher after i.f. infection but not significantly so (P >0.05).
