A nanoparticle vaccine displaying varicella-zoster virus gE antigen induces a superior cellular immune response than a licensed vaccine in mice and non-human primates.

Herpes zoster (HZ), also known as shingles, remains a significant global health issue and most commonly seen in elderly individuals with an early exposure history to varicella-zoster virus (VZV). Currently, the licensed vaccine Shingrix, which comprises a recombinant VZV glycoprotein E (gE) formulated with a potent adjuvant AS01B, is the most effective shingles vaccine on the market. However, undesired reactogenicity and increasing global demand causing vaccine shortage, prompting the development of novel shingles vaccines. Here, we developed novel vaccine candidates utilising multiple nanoparticle (NP) platforms to display the recombinant gE antigen, formulated in an MF59-biosimilar adjuvant. In naïve mice, all tested NP vaccines induced higher humoral and cellular immune responses than Shingrix, among which, the gEM candidate induced the highest cellular response. In live attenuated VZV (VZV LAV)-primed mouse and rhesus macaque models, the gEM candidate elicited superior cell-mediated immunity (CMI) over Shingrix. Collectively, we demonstrated that NP technology remains a suitable tool for developing shingles vaccine, and the reported gEM construct is a highly promising candidate in the next-generation shingles vaccine development.

Chitosan particle-emulsion complex adjuvants: The effect of particle distribution on the immune intensity and response type.

Particle-emulsion complex adjuvants as a new trend in the research of vaccine formulation, can improve the immune strength and balance the immune type. However, the location of the particle in the formulation is a key factor that has not been investigated extensively and its type of immunity. In order to investigate the effect of different combining modes of emulsion and particle on the immune response, three types of particle-emulsion complex adjuvant formulations were designed with the combination of chitosan nanoparticles (CNP) and an o/w emulsion with squalene as the oil phase. The complex adjuvants included the CNP-I group (particle inside the emulsion droplet), CNP-S group (particle on the surface of emulsion droplet) and CNP-O group (particle outside the emulsion droplet), respectively. The formulations with different particle locations behaved with different immunoprotective effects and immune-enhancing mechanisms. Compared with CNP-O, CNP-I and CNP-S significantly improve humoral and cellular immunity. CNP-O was more like two independent systems for immune enhancement. As a result, CNP-S triggered a Th1-type immune bias and CNP-I had more of a Th2-type of the immune response. These data highlight the key influence of the subtle difference of particle location in the droplets for immune response.

Acid-Responsive Immune-Enhancing Chitosan Formulation Capable of Transforming from Particle Stabilization to Polymer Chain Stabilization.

Chitosan with pH sensitivity and biocompatibility was selected to prepare chitosan nanoparticle-stabilized Pickering emulsion (CSPE). The flexibility of CSPE enables stress deformation when in contact with cell membranes, thereby mimicking the deformability of natural pathogens and facilitating their efficient uptake by cells. In the acidic environment of lysosomes, the amino groups of chitosan molecules are protonated, and the water solubility increases. CSPE transforms from particle-stabilized to polymer chain-stabilized, its subsequent swelling and proton accumulation lead to lysosome rupture. The experimental results evaluating CSPE as an adjuvant shows that CSPE could efficiently load antigens, promote endocytosis and antigen cross-presentation, recruit antigen-presenting cells at the injection site, boost T-cell activation, and enhance both humoral and cellular immune responses. In the prophylactic and therapeutic tumor models of E.G7-OVA lymphoma and B16-MUC1 melanoma, CSPE significantly inhibited tumor growth and prolonged the survival of mice. In summary, antigenic lysosomal escape resulted from the chitosan molecular state transition is the key to the enhancement of cellular immunity by CSPE, and CSPE is a promising vaccine adjuvant.

Chitosan hydrochloride salt stabilized emulsion as vaccine adjuvant.

Traditional emulsion adjuvants are stabilized by non-ionic surfactants and promote high humoral immunity. However, because of their electroneutrality, they cannot effectively carry negatively charged antigens and enter the cell to elicit cellular immunity. To overcome this problem, we developed an emulsion using chitosan hydrochloride salt (CSCL) as stabilizer. After optimization, CSCL was successfully adsorbed on the surface of the emulsion (CPSE), and stabilized for two months. CPSE could effectively loading the antigen and slow down the rate of the antigen release. We evaluated the effectiveness of CPSE through intramuscular immunization in mice after cytotoxicity assay proved its safety. CPSE not only induced strong antibody-mediated immune responses, but also generated memory T cells in the spleen as a marker of adaptive immunity. Importantly, CPSE showed advantages over the conventional vaccine formulations in promoting IFN-γ secretion. CPSE may act as a promising candidate to enhance the efficacy of vaccines with acceptable biocompatibility and safety.

Intranasal immunization with inactivated chlamydial elementary bodies formulated in VCG-chitosan nanoparticles induces robust immunity against intranasal Chlamydia psittaci challenge.

Vaccines based on live attenuated Chlamydia elementary bodies (EBs) can cause disease in vaccinated animals and the comparably safer inactivated whole EBs are only marginally protective. Recent studies show that a vaccine formulation comprising UV-inactivated EBs (EB) and appropriate mucosal delivery systems and/or adjuvants induced significant protective immunity. We tested the hypothesis that intranasal delivery of UV-inactivated C. psittaci EB formulated in Vibrio cholerae ghosts (VCG)-chitosan nanoparticles will induce protective immunity against intranasal challenge in SPF chickens. We first compared the impact of VCG and CpG adjuvants on protective immunity following IN mucosal and IM systemic delivery of EB formulated in chitosan hydrogel/microspheres. Immunologic analysis revealed that IN immunization in the presence of VCG induced higher levels of IFN-γ response than IM delivery or the CpG adjuvanted groups. Also, vaccine efficacy evaluation showed enhanced pharyngeal bacterial clearance and protection against lung lesions with the VCG adjuvanted vaccine formulation, thereby establishing the superior adjuvanticity of VCG over CpG. We next evaluated the impact of different concentrations of VCG on protective immunity following IN mucosal immunization. Interestingly, the adjuvanticity of VCG was concentration-dependent, since protective immunity induced following IN mucosal immunization showed dose-dependent immune responses and protection. These studies reveal that formulation of inactivated chlamydial antigens with adjuvants, such as VCG and chitosan increases their ability to induce protective immune responses against challenge.

Green preparation of hydrogel particles-in-emulsions for simultaneous enhancement of humoral and cell-mediated immunity.

Emulsions are one of the most often used vaccine adjuvant formulations. Although they promote high humoral immunity, the induced cellular immunity is often poor, which restrict their application. To enhance the cellular immunity, some researchers have prepared mixed formulations by adding particles into the aqueous phase of emulsions. However, the particle preparation process usually involves the addition and removal of organic reagents, which is environmentally unfriendly and cumbersome. Moreover, the obtained vaccine adjuvant only induces limited cell-mediated immunity and humoral immunity compared with emulsion-adjuvanted vaccines. Herein, we developed a green and simple method for fabricating a novel nanoparticles-in-emulsions (NPE) formulation. Firstly, a temperature-sensitive hydrogel was used to prepare particles by self-solidification without additional crosslinking reagents. Secondly, the white oil was used as organic phase to avoid the particle washing procedures and organic solvent residues. Moreover, the effect of NPE as vaccine adjuvant was evaluated by using two veterinary vaccines as model antigens. NPE showed advantages than the conventional vaccine formulations in inducing both humoral and cellular immunity. This work provides a facile and broadly applicable approach for preparing nanoparticles-in-emulsions formulation, and presents an effective adjuvant for enhancing immunity against infectious diseases.

A novel multiple emulsion enhanced immunity via its biomimetic delivery approach.

To generate effective immunity post-vaccination, antigens need to be effectively captured and taken up by antigen-presenting cells (APCs) as a prerequisite. Biomimetic designs that mimic natural pathogen-like properties have provided platforms for antigen delivery. However, the structural dynamic properties of pathogens leading to their efficient internalization have been neglected in most platforms. Herein, we redesigned a special multiple emulsion with chitosan hydrogel nanoparticles inside, mimicking the configurational flexibility and deformational flexibility of pathogens. With the assistance of chitosan-antigen particles, the novel emulsion exhibited amplified deformability and the vaccine-cell contact zone was increased. Additionally, its configurational transitions, which offered sustained exposure of sheltered uptake signals including antigens and stimulator chitosan during endocytosis, resulted in efficient antigen delivery to APCs. Prolonged antigen depot effect, versatile antigen presentation, multiple immunocyte activation, and marked adjuvant-sparing effects were achieved as compared with those in the control groups. As a result, the intracellular emulsion formulation robustly induced both humoral and cellular immunity, especially CTL response, against the foot-and-mouth disease virus (FMDV) with improved biosafety. Our study highlights the positive impact of biomimetic structural dynamic properties on robust vaccine-cell interactions and provides a promising FMDV vaccine candidate.

Exploiting the Lymph-Node-Amplifying Effect for Potent Systemic and Gastrointestinal Immune Responses via Polymer/Lipid Nanoparticles.

Parenteral vaccinations are not able to elicit effective systemic and gastrointestinal immune protection simultaneously because the lymphocytes are typically restricted to primed tissues. Although all-trans retinoic acid (atRA) was reported to trigger the gut-homing of immunocytes, the bioavailability and systemic immune responses remain limited for use in robust enteric vaccinations. Here, we show that co-delivery of atRA, CpG oligodeoxynucleotides (CpG), and antigens via engineered polymer/lipid nanoparticles (PLNPs) could exploit the amplifying function of draining lymph nodes (DLNs) for potent gut tropism and immune activations. After intramuscular injection, forming an immune-potentiated environment at the injection site, the PLNPs induced the designated transfer of primed dendritic cells (DCs) to the DLNs instead of the gastrointestinal tissues. Within the DLNs, the immune-potentiated environment markedly amplified the antigen presentation and homing receptor switch among immunocytes, which simultaneously stimulated the preferential dissipation of activated lymphocytes in the peripheral and gastrointestinal tissues, that is, exerted a DLN-amplifying effect. Compared with current atRA-containing formulations, the PLNPs not only boosted potent IgG secretions and T cell activations in the peripheral tissue but also provoked robust T cell homing and antigen-specific IgA levels in the gastrointestinal tracts in both ovalbumin and EV71 vaccinations. These data indicate that exploiting DLN amplification can stimulate potent systemic and gastrointestinal responses for more efficient enteric vaccinations.