Fig. 4. Virus replication in the respiratory tract.

Virus titers in the throat, 2 and 3 days post challenge (d.p.c.) and in the trachea and lung 3 d.p.c. in ferrets vaccinated with placebo (black squares), split vaccines alone (45 µg HA—blue circles, 15 µg HA—red triangles) or SWE-adjuvanted split vaccines (15 µg HA—green open circles, 7.5 µg HA—purple diamonds). The virus titers in the transport buffer of the swabs or homogenized tissue samples were determined by end-point titration on MDCK cells using a fivefold serial dilution. Presented are the individual 10 log-transformed titers, their averages (bar) and SD (error bar). Dotted horizontal lines indicate limit of detection. One animal of the placebo group was excluded as this animal died ~1 day before section. Another animal of the placebo group that died prior to section was still included as the time of death was only a few hours before section. WMW test: *p < 0.05; **p < 0.01.