Pattern-Recognition Receptor Agonist-Containing Immunopotentiator CVC1302 Boosts High-Affinity Long-Lasting Humoral Immunity.

Ideally, a vaccine should provide life-long protection following a single administered dose. In our previous study, the immunopotentiator CVC1302, which contains pattern- recognition receptor (PRR) agonists, was demonstrated to prolong the lifetime of the humoral immune response induced by killed foot-and-mouth disease virus (FMDV) vaccine. To elucidate the mechanism by which CVC1302 induces long-term humoral immunity, we used 4-hydroxy-3-nitrophenylacetyl (NP)-OVA as a pattern antigen and administered it to mice along with CVC1302, emulsified together with Marcol 52 mineral oil (NP-CVC1302). From the results of NP-specific antibody levels, we found that CVC1302 could induce not only higher levels of NP-specific antibodies but also high-affinity NP-specific antibody levels. To detect the resulting NP-specific immune cells, samples were taken from the injection sites, draining lymph nodes (LNs), and bone marrow of mice injected with NP-CVC1302. The results of these experiments show that, compared with mice injected with NP alone, those injected with NP-CVC1302 had higher percentages of NP+ antigen-presenting cells (APCs) at the injection sites and draining LNs, higher percentages of follicular helper T cells (TFH), germinal center (GC) B cells, and NP+ plasma-blasts in the draining LNs, as well as higher percentages of NP+ long-lived plasma cells (LLPCs) in the bone marrow. Additionally, we observed that the inclusion of CVC1302 in the immunization prolonged the lifetime of LLPCs in the bone marrow by improving the transcription expression of anti-apoptotic transcription factors such as Mcl-1, Bcl-2, BAFF, BCMA, Bax, and IRF-4. This research provides a blueprint for designing new generations of immunopotentiators.

Development of a novel oil-in-water emulsion and evaluation of its potential adjuvant function in a swine influenza vaccine in mice.

BACKGROUND: Vaccination is the principal strategy for prevention and control of diseases, and adjuvant use is an effective strategy to enhance vaccine efficacy. Traditional mineral oil-based adjuvants have been reported with post-immunization reactions. Developing new adjuvant formulations with improved potency and safety will be of great value. RESULTS: In the study reported herein, a novel oil-in-water (O/W) Emulsion Adjuvant containing Squalane (termed EAS) was developed, characterized and investigated for swine influenza virus immunization. The data show that EAS is a homogeneous nanoemulsion with small particle size (~ 105 nm), low viscosity (2.04 ± 0.24 cP at 20 °C), excellent stability (at least 24 months at 4 °C) and low toxicity. EAS-adjuvanted H3N2 swine influenza vaccine was administrated in mice subcutaneously to assess the adjuvant potency of EAS. The results demonstrated that in mice EAS-adjuvanted vaccine induced significantly higher titers of hemagglutination inhibition (HI) and IgG antibodies than water-in-oil (W/O) vaccines or antigen alone, respectively, at day 42 post vaccination (dpv) (P < 0.05). EAS-adjuvanted vaccine elicited significantly stronger IgG1 and IgG2a antibodies and higher concentrations of Th1 (IFN-γ and IL-2) cytokines compared to the W/O vaccine or antigen alone. Mice immunized with EAS-adjuvanted influenza vaccine conferred potent protection after homologous challenge. CONCLUSION: The O/W emulsion EAS developed in the present work induced potent humoral and cellular immune responses against inactivated swine influenza virus, conferred effective protection after homologous virus challenge and showed low toxicity in mice, indicating that EAS is as good as the commercial adjuvant MF59. The superiority of EAS to the conventional W/O formulation in adjuvant activity, safety and stability will make it a potential veterinary adjuvant.