The plates were incubated at 37 °C in 5% CO2 for 3 days. The presence of cytopathic effects (CPEs) was determined under a microscope, and viral titers were calculated as log10 of TCID50/ml. When no CPE was observed using undiluted viral solution, it
was defined as an undetectable level, which was considered to be lower than 1.4 log10 of TCID50/ml. Activation of the inflammasome in peritoneal resident macrophages was examined according to the protocol previously reported . Briefly, peritoneal resident macrophages were collected from C57BL/6 mice (Charles River Laboratories Japan, Inc., Kanagawa, Japan) and were prepared with complete RPMI1640 medium (Invitrogen). Macrophages were primed with 50 ng/ml LPS (Sigma-Aldrich) GSK126 datasheet for 18 h and then stimulated with sHZ or Alum (Invivogen)
for 8 h. The concentration of IL-1β in supernatant was measured by ELISA (R&D systems, Minneapolis, MN). Viral titers and body temperature of each animal were calculated as the area under the curve (AUC) by the trapezoidal method. Statistical significance between groups was determined by Dunnett’s multiple comparison test using the statistical analysis software SAS (version 9.2) for Windows (SAS Institute, Cary, NC). To examine the adjuvant effect of sHZ on HA split vaccine, ferrets (n = 4 per group) were twice MK-2206 price immunized with SV with or without sHZ (800 μg) or Fluad, and then their serum HI titers were measured every week. Fluad is composed of SV adjuvanted with MF59, a licensed squalene-based emulsion, widely used in clinical settings Thymidine kinase . On day 28 after the first immunization, HI titers of SV/sHZ group against H1, H3, and B virus antigens were significantly up-regulated, of which the GMT was 135, 28, and 40, respectively, comparable to those elicited by MF59 (p < 0.05, Fig. 1A–C). After the second immunization, HI titers of the SV/sHZ group against all three antigens were significantly higher than those of the SV group on day 35 (p < 0.05) ( Fig. 1A–C). The GMTs of the
HI titers against H1, H3, and B antigens in the SV/sHZ group were 905, 190, and 381, respectively. The boosting effect of sHZ was also comparable to that of MF59. By contrast, HI titers against three HA antigens of the SV group were not enhanced at every analysis point ( Fig. 1A–C). These results demonstrated that sHZ has a potent adjuvanticity to enhance the immunogenicity of SV, and its activity was comparable to that of MF59 in ferrets. Next, the dose-dependent adjuvanticity of sHZ to enhance the immunogenicity of SV was examined. Ferrets were twice immunized with SV/sHZ (50–800 μg), and HI titers were measured at every week. The adjuvanticity to enhance HI titers against HA antigens of H1 and B was observed with at least 200 μg of sHZ after the first immunization, but no boosting effect of 200 μg of sHZ was observed after the second immunization (Fig. 2).