A-910823, a squalene-based emulsion adjuvant, induces T follicular helper cells and humoral immune responses via α-tocopherol component

MIL-53(Al)-oil/water emulsion composite as an adjuvant promotes immune responses to an inactivated pseudorabies virus vaccine in mice and pigs

Although vaccination with inactivated vaccines is a popular preventive method against pseudorabies virus (PRV) infection, inactivated vaccines have poor protection efficiency because of their weak immunogenicity. The development of an effective adjuvant is urgently needed to improve the efficacy of inactivated PRV vaccines. In this study, a promising nanocomposite adjuvant named as MIL@A-SW01-C was developed by combining polyacrylic acid-coated metal-organic framework MIL-53(Al) (MIL@A) and squalene (oil)-in-water emulsion (SW01) and then mixing it with a carbomer solution. One part of the MIL@A was loaded onto the oil/water interface of SW01 emulsion via hydrophobic interaction and coordination, while another part was dispersed in the continuous water phase using carbomer. MIL@A-SW01-C showed good biocompatibility, high PRV (antigen)-loading capability, and sustained antigen release. Furthermore, the MIL@A-SW01-C adjuvanted PRV vaccine induced high specific serum antibody titers, increased splenocyte proliferation and cytokine secretion, and a more balanced Th1/Th2 immune response compared with commercial adjuvants, such as alum and biphasic 201. In the mouse challenge experiment, two- and one-shot vaccinations resulted in survival rates of 73.3 % and 86.7 %, respectively. After one-shot vaccination, the host animal pigs were also challenged with wild PRV. A protection rate of 100 % was achieved, which was much higher than that observed with commercial adjuvants. This study not only establishes the superiority of MIL@A-SW01-C composite nanoadjuvant for inactivated PRV vaccine in mice and pigs but also presents an effective method for developing promising nanoadjuvants. STATEMENT OF SIGNIFICANCE: We have developed a nanocomposite of MIL-53(Al) and oil-in-water emulsion (MIL@A-SW01-C) as a promising adjuvant for the inactivated PRV vaccines. MIL@A-SW01-C has good biocompatibility, high PRV (antigen) loading capability, and prolonged antigen release. The developed nanoadjuvant induced much higher specific IgG antibody titers, increased splenocyte proliferation and cytokine secretion, and a more balanced Th1/Th2 immune response than commercial adjuvants alum and biphasic 201. In mouse challenge experiments, survival rates of 73.3 % and 86.7 % were achieved from two-shot and one-shot vaccinations, respectively. At the same time, a protection rate of 100 % was achieved with the host animal pigs challenged with wild PRV.

Differential Regulation of DC Function, Adaptive Immunity, and MyD88 Dependence by MF59 and AS03-like Adjuvants

MF59 and AS03 are squalene emulsion-based vaccine adjuvants with similar compositions and droplet sizes. Despite their broad use in licensed influenza vaccines, few studies compared their adjuvant effects and action mechanisms side by side. Considering the majority of adjuvants act on dendritic cells (DCs) to achieve their adjuvant effects, this study compared MF59 and AS03-like adjuvants (AddaVax and AddaS03, respectively) to enhance antigen uptake, DC maturation, ovalbumin (OVA) and seasonal influenza vaccine-induced immune responses. Considering MF59 was reported to activate MyD88 to mediate its adjuvant effects, this study also investigated whether the above-explored adjuvant effects of AddaVax and AddaS03 depended on MyD88. We found AddaVax more potently enhanced antigen uptake at the local injection site, while AddaS03 more potently enhanced antigen uptake in the draining lymph nodes. AddaS03 but not AddaVax stimulated DC maturation. Adjuvant-enhanced antigen uptake was MyD88 independent, while AddaS03-induced DC maturation was MyD88 dependent. AddaVax and AddaS03 similarly enhanced OVA-induced IgG and subtype IgG1 antibody responses as well as influenza vaccine-induced hemagglutination inhibition antibody titers, whileAddaS03 more potently enhanced OVA-specific IgG2c antibody responses. Both adjuvants depended on MyD88 to enhance vaccine-induced antibody responses, while AddaVax depended more on MyD88 to achieve its adjuvant effects. Our study reveals similarities and differences of the two squalene emulsion-based vaccine adjuvants, contributing to our improved understanding of their action mechanisms.

CD4 T cell-activating neoantigens enhance personalized cancer vaccine efficacy

Personalized cancer vaccines aim to activate and expand cytotoxic antitumor CD8+ T cells to recognize and kill tumor cells. However, the role of CD4+ T cell activation in the clinical benefit of these vaccines is not well defined. We previously established a personalized neoantigen vaccine (PancVAX) for the pancreatic cancer cell line Panc02, which activates tumor-specific CD8+ T cells but required combinatorial checkpoint modulators to achieve therapeutic efficacy. To determine the effects of neoantigen-specific CD4+ T cell activation, we generated a vaccine (PancVAX2) targeting both major histocompatibility complex class I- (MHCI-) and MHCII-specific neoantigens. Tumor-bearing mice vaccinated with PancVAX2 had significantly improved control of tumor growth and long-term survival benefit without concurrent administration of checkpoint inhibitors. PancVAX2 significantly enhanced priming and recruitment of neoantigen-specific CD8+ T cells into the tumor with lower PD-1 expression after reactivation compared with the CD8+ vaccine alone. Vaccine-induced neoantigen-specific Th1 CD4+ T cells in the tumor were associated with decreased Tregs. Consistent with this, PancVAX2 was associated with more proimmune myeloid-derived suppressor cells and M1-like macrophages in the tumor, demonstrating a less immunosuppressive tumor microenvironment. This study demonstrates the biological importance of prioritizing and including CD4+ T cell-specific neoantigens for personalized cancer vaccine modalities.