Figure 5.

Lung viral burdens after immunization and H5N1 challenge. Mice were immunized two times using a single MVA vaccine that encoded M1 + NP + METRC (“single insert”) or a combination of three separate MVA vaccines each encoding M1 or NP or METRC (“Blend”). “Prime” indicates previous mild infection with PR8 H1N1 INFV A, 21 days prior to vaccine administration. A TCID₅₀ assay was performed to quantify infectious H5N1 virus in lungs (N = 5 per group) 4 days after A/VN/1203/04 challenge (H5N1). The horizontal bar for each group represents the arithmetic mean Log₁₀ TCID₅₀ per gram tissue. Individual dots represent the results of each animal. The limit of detection for this assay was 1.7 Log₁₀ TCID₅₀. Lung viral burden on day 2 (data not shown) had nearly identical results compared to day 4. Without PR8 priming, only the MVA H5HA vaccine was different (p < 0.0001, ANOVA followed by Tukey–Kramer test) from the MVAtor control. If delivered after PR8 priming, MVA encoding M1 + NP + METRC as a single insert again was significantly different from MVAtor with priming (p = 0.019). Priming gave protective advantage to all test vaccines including the MVAtor negative control. Limit of detection was log 1.7.