Use of a Clostridioides difficile Murine Immunization and Challenge Model to Evaluate Single and Combination Vaccine Adjuvants Consisting of Alum and NKT Cell-Activating Ligands

Adjuvant combinations may enhance or broaden the expression of immune responses to vaccine antigens. Information on whether established Alum type adjuvants can be combined with experimental CD1d ligand adjuvants is currently lacking. In this study, we used a murine Clostridioides difficile immunization and challenge model to evaluate Alum (Alhydrogel™), α-galactosylceramide (α-GC), and one of its analogs 7DW8-5 singly and in combination as vaccine adjuvants. We observed that the Alum/α-GC combination caused modest enhancement of vaccine antigen-specific IgG1 and IgG2b responses, and a broadening to include IgG2c that did not significantly impact overall protection. Similar observations were made using the Alum/7DW8-5 combination. Examination of the impact of adjuvants on NKT cells revealed expansion of invariant NKT (iNKT) cells with modest expansion of their iNKTfh subset and little effect on diverse NKT (dNKT) cells. Side effects of the adjuvants was determined and revealed transient hepatotoxicity when Alum/α-GC was used in combination but not singly. In summary these results showed that the Alum/α-GC or the Alum/7DW8-5 combination could exert distinct effects on the NKT cell compartment and on isotype switch to produce Th1-driven IgG subclasses in addition to Alum/Th2-driven subclasses. While Alum alone was efficacious in stimulating IgG-mediated protection, and α-GC offered no apparent additional benefit in the C. difficile challenge model, the work herein reveals immune response features that could be optimized and harnessed in other vaccine contexts.

Nanodiamonds in Oil Emulsions as Effective Vaccine Adjuvants and Antitumor Therapeutic Agents

Background Composed of mineral oil and mycobacteria pathogens, complete Freund’s adjuvant (CFA) is one of the most commonly used adjuvants for antibody production and scientific research due to its high efficiency. However, the dead mycobacteria in CFA can cause many allergic reactions. We propose here a new formulation based on the use of nanodiamonds (NDs) as biocompatible non-allergic additives in incomplete Freund’s adjuvant (IFA) to avoid these adverse effects. Methods Chicken egg ovalbumin (OVA) was used as the antigens and 100-nm NDs after purification by air oxidation and strong oxidative acid washes were used as the additives. Levels of OVA-specific IgG antibody in mouse sera were measured by using enzyme-linked immunosorbent assays (ELISA) after the second and third immunizations of healthy mice with OVA and OVA/ND in IFA or CFA. Abilities of the OVA/ND/IFA vaccination to inhibit the tumor growth of mice inoculated with EL4 cells or OVA-expressing E.G7 cells were examined over 1 month. Results The new formulation worked well as a potent vaccine adjuvant, which could boost the immune responses and reduce the consumption of antigens in producing antibodies of interest in model animals like mice. Additionally, the composites showed distinct therapeutic activities, as proven by the OVA/ND/IFA treatment that effectively inhibited the tumor progression of E.G7-inoculated mice, allowing the animals to survive over 35 days post tumor-cell challenges. About 0.2% of the injected ND particles were found in mouse spleens on day 24 after vaccination of the E.G7-inoculated mice with OVA/ND/IFA. Conclusions The multiple functionality of ND makes it useful as an active and trackable component of a vaccine adjuvant not only to enhance antibody production but also to suppress tumor growth in vivo. The ND-based new formulation can be developed into single-dose vaccines with promising potential for real-world applications.

Applications of Chitosan-Alginate-Based Nanoparticles—An Up-to-Date Review

Chitosan and alginate are two of the most studied natural polymers that have attracted interest for multiple uses in their nano form. The biomedical field is one of the domains benefiting the most from the development of nanotechnology, as increasing research interest has been oriented to developing chitosan-alginate biocompatible delivery vehicles, antimicrobial agents, and vaccine adjuvants. Moreover, these nanomaterials of natural origin have also become appealing for environmental protection (e.g., water treatment, environmental-friendly fertilizers, herbicides, and pesticides) and the food industry. In this respect, the present paper aims to discuss some of the newest applications of chitosan-alginate-based nanomaterials and serve as an inception point for further research in the field.

Application of Nanoemulsions in the Vaccination Process

Vaccination is one of the most effective approaches for the prevention of deadly and highly contagious diseases. One of the important biomedical applications of nanoemulsions is in the process of vaccination. Nanoemulsions are made from nano-sized safe, well-considered ingredients, amalgamated in a protective way to bring forth a stable emulsion. They have provided ways for vaccine delivery using intranasal or mucosal oil-based emulsions rather than using needles. Also, some nanoemulsions have effectively shown anti-pathogenic activities against several germs. Nanoemulsions are also used as vaccine adjuvants and are used to boost the effectiveness of vaccines. Nanoemulsion-based adjuvants put forward the possibility of non-irritating, needle-free vaccines, handed out as nose drops or as a simple nasal sprayer. The chapter aims to discuss the applications of nanoemulsions in the process of vaccination.

In situ real time monitoring of emulsification and homogenization processes for vaccine adjuvants

Process analytical technology was used to monitor formation of a stable emulsion product, with results providing improved understanding of emulsion-based vaccine adjuvant formation processes.

Peptide Aggregation Induced Immunogenic Rupture (PAIIR)

Under the influence of stress and membrane damage, cells undergo immunogenic cell death (ICD), which involves the release of damage associated molecular patterns (DAMPs), natural adjuvants for enhancing an immune response. In the presence of an antigen, released DAMPs can determine the type and magnitude of the immune response, and therefore the longevity and efficacy of an antigen-specific immunity. In the last decade, the immune response effect of ICD has been shown, yet there is no tool that can induce controlled ICD with predictable results, regardless of the cell type. We designed a peptide-based tool, called [II], for controlled damage to cell membrane to induce ICD and DAMPs release. Herein we describe a series of experiments that determine that the mechanism of action of [II] includes a caspase-dependent ICD and subsequent release of immune stimulating DAMPs, on various cell types. Moreover, we tested the hypothesis that controlled DAMP release via [II] in vivo was associated with enhancement of antigen-specific adaptive immunity with influenza hemagglutinin (HA) subunit vaccine. HA and [II] showed significantly higher HA specific IgG1 and IgG2a antibodies, compared to HA-only immunized mice, while the peptide itself did not elicit antibodies. In this paper, we demonstrate the first peptide-aggregation induced immunogenic rupture (PAIIR) approach as vaccine adjuvants for increasing both humoral and cellular immunity. In consideration of its ability to enhance IgG2a responses that are associated with heterosubtypic influenza virus protection, PAIIR is a promising adjuvant to promote universal protection upon influenza HA vaccination.

Trehalose amide glycolipids as Mincle ligands: Towards new vaccine adjuvants

<p>The development of new vaccines to respond to infectious diseases requires new vaccine adjuvants, which improve vaccine efficacy and shape the immune response. Trehalose glycolipids, consisting of α,α'-trehalose esterified at the 6- and 6'- positions with lipids, exhibit adjuvant activity by binding and activating Macrophage inducible C-type lectin (Mincle). However, the adjuvant activity of trehalose glycolipids could potentially be improved by substituting the ester linkages for more physiologically stable amide bonds. This thesis presents a short protecting group free route to trehalose amide glycolipids, thus allowing for the synthesis of the straight chain glycolipid amides 1a-e in four steps and in excellent (53-61%) overall yields (Figure 1). Amide glycolipids 1a-e were demonstrated to be Mincle agonists with comparable activity to their ester counterparts, as determined using a green fluorescent protein (GFP) reporter cell line assay. A second generation of trehalose amide glycolipids, the lipidated brartemicin amide analogues 2a-c, were subsequently synthesised (Figure 1). This report is the first example of trehalose amide glycolipids acting as Mincle agonists, and further studies into the potential of the amides as vaccine adjuvants will be undertaken in due course.</p>

Trehalose amide glycolipids as Mincle ligands: Towards new vaccine adjuvants

<p>The development of new vaccines to respond to infectious diseases requires new vaccine adjuvants, which improve vaccine efficacy and shape the immune response. Trehalose glycolipids, consisting of α,α'-trehalose esterified at the 6- and 6'- positions with lipids, exhibit adjuvant activity by binding and activating Macrophage inducible C-type lectin (Mincle). However, the adjuvant activity of trehalose glycolipids could potentially be improved by substituting the ester linkages for more physiologically stable amide bonds. This thesis presents a short protecting group free route to trehalose amide glycolipids, thus allowing for the synthesis of the straight chain glycolipid amides 1a-e in four steps and in excellent (53-61%) overall yields (Figure 1). Amide glycolipids 1a-e were demonstrated to be Mincle agonists with comparable activity to their ester counterparts, as determined using a green fluorescent protein (GFP) reporter cell line assay. A second generation of trehalose amide glycolipids, the lipidated brartemicin amide analogues 2a-c, were subsequently synthesised (Figure 1). This report is the first example of trehalose amide glycolipids acting as Mincle agonists, and further studies into the potential of the amides as vaccine adjuvants will be undertaken in due course.</p>