Figure 2. Immune responses and protection following addition of exogenous 5mer4 to the H5N1-HA DNA vaccine.

Exogenous 5mer4 was added to the H5N1-HA DNA vaccine and administered to groups of BALB/c mice. (a) T-cell responses. Groups of 4 BALB/c mice were immunized with H5N1-HA DNA vaccine (50 µg) and increasing concentrations of 5mer4 adjuvant (5, 10, or 50 µg). Cellular immune responses were screened 10 days post-immunization through detection of IFN-γ secretion. Responses from the HA-5mer4 conjugate vaccine (Figure 1b) are presented in grey for comparison. (b) Hemagglutination inhibition antibody responses. Serum was individually evaluated from 8–10 BALB/c mice immunized with 5mer4 (50 µg), H5N1-HA (1 µg) + 5mer4 (50 µg), H5N1-HA (1 µg), H5N1-HA (50 µg), or PBS. HI antibody responses were detected using horse red blood cells. (*p = 0.004) The HI antibody titre from the HA-5mer4 conjugate vaccine (Figure 1c) is presented in grey for comparison. (c) Survival against lethal homologous challenge. Groups of 10 BALB/c mice were vaccinated with H5N1-HA (1 µg) + 5mer4 (5 ▴, 50 ♦, or 100 µg •), 5mer4 (50 µg ○), H5N1-HA (1 µg ▾) + DMSO, or a PBS control ▪. Animals were challenged with 100LD₅₀ of lethal homologous H5N1-H05 virus and monitored for 18 days. (*p = 0.006, **p<0.01) (d) Survival against lethal heterologous challenge. Groups of 10 BALB/c mice were vaccinated with H5N1-HA (100 µg) + 5mer4 (50 µg) ▴, H5N1-HA (100 µg) ▾, or a PBS control ▪. Animals were infected with 100LD₅₀ of heterologous H5N1-HK97 virus. Error bars represent ± SEM.