FIG 6.

VSVΔG-H5N1 provides protection against H5N1 challenge. Mice vaccinated with VSVΔG-H5N1 are protected against lethal challenge with the low-pathogenicity HALo influenza challenge virus, a 6:2 gene segment reassortant virus containing HA and NA of VN1203, with the removal of the polybasic cleavage site in HA, and the internal gene segments of PR8. (A) Duration of protective immunity against HALo challenge. Groups of 5 mice vaccinated with 10⁶ PFU of VSVΔG-H5N1 by either the i.m. or i.n. route were challenged with 4 LD₅₀ of HALo influenza virus at 140 days postvaccination. Control mice were a group of 3 unvaccinated age-matched mice. (B) Challenge experiments utilizing higher-dose (1.25 × 10⁷ PFU) i.m. vaccination with VSVΔG-H5N1 and a shorter interval to challenge. Groups of 6 mice were vaccinated i.m. with 1.25 × 10⁷ PFU of either VSVΔG-H5N1 or VSVΔG-G(NiV) (VSVΔG expressing the G glycoprotein of Nipah virus) (control group). Mice were challenged with 10 LD₅₀ of HALo influenza virus at 34 days postvaccination. (C) Short-interval challenge to establish if rapid protection against lethal challenge can be achieved. Groups of 5 mice were vaccinated i.n. with either 1.25 × 10⁷ PFU of VSVΔG-H5N1 or 10⁶ PFU of VSV-EGFP (control group). Mice were challenged with 10 LD₅₀ of HALo influenza virus at 14 days postvaccination. Error bars represent 1 standard deviation above and below the average weight. Asterisks indicate the number of animals that died at the given time points.