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. twice with a complex of hH5N1 HA233 encapsulated in indicated combination. The immunized mice were challenged intranasally with the rH5N1 virus (PR8/H5Lo) (A–C). After the virus challenge, the survival rate (A) and the body weight (B) were recorded for 20 days (N = 8/group). The lungs were collected at 3 days, 6 days or 30 days after the challenge with the rH5N1 virus (PR8/H5Lo) (C) (N = 3/group). Scale bars in (C), 100 µm. To estimate the viral clearance, the lung viral titers were measured by means of a plaque assay at 3 days or 6 days after the challenge with the rH5N1 virus (D). Lipoplex(O), MB-ODN 4531(O) encapsulated in DOPE:CHEMS (1∶1 ratio) complex; LipoplexGC(O), MB-ODN 4531GC(O) encapsulated in DOPE:CHEMS (1∶1 ratio) complex.