Immunization with a Hemagglutinin-Derived Synthetic Peptide Formulated with a CpG-DNA-Liposome Complex Induced Protection against Lethal Influenza Virus Infection in Mice
BALB/c mice were immunized i.p. two times with a complex of hH1N1-WSN HA233 and Lipoplex(O) (Lipoplex(O)+hH1N1-WSN HA233). The immunized mice were challenged intranasally with the rH5N1 virus (PR8/H5Lo) or the maA/WSN/1933 virus. After the virus challenge, the survival rate (A) and the body weight (B) were recorded for 22 days (N = 8/group). Lungs were collected at 3 days or 6 days after the challenge with the rH5N1 virus or the maA/WSN/1933 virus (N = 3/group) (C). Scale bars in (C), 100 µm. The lung viral titers were measured by means of a plaque assay to estimate the viral clearance at 3 days or 6 days after the challenge with the maA/WSN/1933 virus or rH5N1 virus (D).