Liposome and QS-21 Combined Adjuvant Induces theHumoral and Cellular Responses of Acellular Pertussis Vaccine in a Mice Model

Abstract

The resurgence of pertussis in vaccinated communities may be related to the reduced long-term immunity induced by acellular pertussis vaccines. Therefore, developing improved pertussis vaccine candidates that could induce strong Th1 or Th17 cellular immunity is an urgent need. The use of new adjuvants may well meet this requirement. In this research, we developed a novel adjuvant candidate by combining liposome and QS-21 adjuvant. Adjuvant activity, protective efficacy, the level of neutralizing antibody against PT, and the resident memory T (T_RM) cells in lung tissue after vaccination were studied. We then performed B. pertussis respiratory challenge in mice after they received vaccination with traditional aluminum hydroxide and the novel adjuvant combination. Results showed that the liposome + QS-21 adjuvant group had a rapid antibody and higher antibody (PT, FHA, Fim) level, induced anti-PT neutralizing antibody and recruited more IL-17A-secreting CD4⁺ T_RM cells along with IL-17A-secreting CD8⁺ T_RM cells in mice, which provided robust protection against B. pertussis infection. These results provide a key basis for liposome + QS-21 adjuvant as a promising adjuvant candidate for developing an acellular pertussis vaccine that elicits protective immunity against pertussis.

Keywords: Bordetella pertussis; adjuvant; mouse model; tissue-resident memory T cell; vaccine.

Figure 1

SDS-PAGE (5–12%) stained with Coomassie blue R250. Mr, molecular weight. M, protein marker (26616#, Thermo Fisher, Waltham, MA, USA). 1, PT reference. 2, PT not detoxified. 3, PT detoxified. 4, FHA reference. 5, FHA. 6, PRN reference. 7, PRN. 8, Fim2/3 reference. 9, Fim2/3.

Figure 2

The results of the serological test in CD1 mice. CD1 mice received intraperitoneal injection (i.p.) of 100 μL different aP formulations. Serum antibody titers anti-PT (A), anti-FHA (B), anti-PRN (C), and anti-Fim2/3 (D), after 7, 21, 35 and 42 days of immunizations with vaccine were detected using ELISA. The red, blue, and black columns represent LQ-aP, AL-aP, and NS groups, respectively. Results are geometric mean ± SD of mice per group per time point. (E) Day 42 in vitro neutralization titers of anti-PT (JNIH-5) using different sera. Results are geometric mean ± SD mice per group. ns: non-significant, * p < 0.05, ** p < 0.01, *** p < 0.001 by two-way ANOVA with the Tukey’s post hoc test.

Figure 3

The proportion of IFN-γ-, IL-4-, and IL-17A-secreting CD4⁺ T cells in the spleens with flow cytometry analysis. The results shown are mean ± SD. ns: non-significant, * p < 0.05, ** p < 0.01, by two-way ANOVA with the Tukey’s post hoc test.

Figure 4

(A): The proportion of IFN-γ-, IL-4-, and IL-17A-secreting CD45^iv−CD44⁺CD62L⁻CD69⁺CD103^±CD4 T_RM cells in lungs after immunization. (B): The proportion of IFN-γ-, IL-4-, and IL-17A-secreting CD45^iv−CD44⁺CD62L⁻CD69⁺CD103^±CD8 T_RM cells in lungs after immunization. The results shown are mean ± SD. ns: non-significant, * p < 0.05, ** p < 0.01, *** p < 0.001 by two-way ANOVA with the Tukey’s post hoc test.

Figure 5

The antibody titers of IgG1 and IgG2c in C57BL/6 mice after two immunizations. The results shown are mean ± SD. * p < 0.05 by one-way ANOVA with the Tukey’s post hoc test. Only significant differences between experimental groups are indicated.

Figure 6

CFUs in the lungs were enumerated on days 3, 7, and 14 post-challenges. The results shown are mean ± SD of mice (n = 3). The results shown are mean ± SD. * p < 0.05, ** p < 0.01 by one-way ANOVA with the Tukey’s post hoc test. Only significant differences between experimental groups are indicated.