Protection against Multiple Subtypes of Influenza Viruses by Virus-Like Particle Vaccines Based on a Hemagglutinin Conserved Epitope

Figure 2

Schematic of the vaccine regimen. BALB/c mice were anesthetized and immunized three times (2 weeks apart) intranasally with different doses of LAH-HBc VLP alone or in combination with CTB^* adjuvant. Three weeks after the last immunization, three mice from each group were randomly chosen for sample collection to analyze the adaptive immune response (sera, nasal wash, and splenocytes). Meanwhile, the remaining mice were anesthetized and challenged intranasally with 5 × LD₅₀ of influenza viruses. At 3 days after the challenge, 3 mice of each group were randomly taken out for lung lavage and virus titer determination and the remaining 10 mice in each group were observed for survival rates and body weight changes.