Figure 9. Comparison of viral titers in virus-challenged lung tissues of mice vaccinated with HA-13–263 proteins.

Viral titers of VN/1194 (clade 1) and SZ/406H (clade 2.3.4) H5N1 viruses were determined in the lung tissues of the mice vaccinated with HA-13–263 proteins, respectively, collected on 5 day post-challenge. Mice injected with PBS were used as the negative control. * indicates significant difference (P<0.05), respectively, between HA-13–263-Fdc, HA-13–263-Fc, or HA-13–263-Fd-His vaccination groups and HA-13–263-His or PBS control group. The data are expressed as mean ± SD of viral titers 50% tissue culture infective dose (Log₁₀TCID₅₀/g) of lung tissues from five mice per group. The limit of detection is 1.5 Log₁₀TCID₅₀/g of tissues.