Inducing efficient cross-priming using antigen-coated yeast particles

β-1,3 Glucan Microparticles & Nanoparticles: Fabrication Methods & Applications in Immunomodulation & Targeted Drug Delivery

Innate immune cells such as macrophages and dendritic cells play major roles in the progression of many cancerous, fibrotic, and autoimmune diseases, often due to environmental cues that skew these cells toward a phenotype that progresses or exacerbates the disease state. As such, a growing focus in treating such diseases is placed on exploiting the high plasticity of these cells to modify or reverse their pro-disease phenotypes using immunomodulatory materials. β-1,3 glucans are one such type of material that has exhibited diverse immunomodulatory effects on immune cells, including the mitigation or reversal of the adverse effects of dysregulated immune cells. In this review, we outline various fabrication techniques to produce β-1,3 glucan-derived microparticles and nanoparticles and discuss the diverse particle properties that can be obtained by tuning glucan chemistry, fabrication method, and formulation components. Furthermore, the immunomodulatory applications of β-1,3 glucan particles are highlighted with a focus on immune cell targeting, modulation, and the delivery of small molecule and macromolecular therapeutics.

Yeast oral vaccines against infectious diseases

Vaccines that are delivered orally have several advantages over their counterparts that are administered via injection. Despite the advantages of oral delivery, however, approved oral vaccines are currently limited either to diseases that affect the gastrointestinal tract or to pathogens that have a crucial life cycle stage in the gut. Moreover, all of the approved oral vaccines for these diseases involve live-attenuated or inactivated pathogens. This mini-review summarizes the potential and challenges of yeast oral vaccine delivery systems for animal and human infectious diseases. These delivery systems utilize whole yeast recombinant cells that are consumed orally to transport candidate antigens to the immune system of the gut. This review begins with a discussion of the challenges associated with oral administration of vaccines and the distinct benefits offered by whole yeast delivery systems over other delivery systems. It then surveys the emerging yeast oral vaccines that have been developed over the past decade to combat animal and human diseases. In recent years, several candidate vaccines have emerged that can elicit the necessary immune response to provide significant protection against challenge by pathogen. They serve as proof of principle to show that yeast oral vaccines hold much promise.

Expression of an immunocomplex consisting of Fc fragment fused with a consensus dengue envelope domain III in Saccharomyces cerevisiae

Objectives

To explore Saccharomyces cerevisiae as an expression platform for dengue oral immune complex vaccine development.

Results

Molecular engineering was applied to create a fusion gene construct (scEDIII-PIGS) consisting of a yeast codon optimized sequence encoding for a synthetic consensus dengue envelope domain III (scEDIII) followed by a modified IgG Fc domain (PIGS). Northern blot showed transcription of the target gene, with a temporal expression pattern similar to those from previous work. Western blot showed assembly of various immune complexes from monomer to hexamer. Partial purification of scEDIII-PIGS was also attempted to demonstrate the feasibility of yeast system for immune complex vaccine development. Approximately 1 mg of scEDIII-PIGS can be produced from 1 l culture.

Conclusion

This work demonstrated for the first time that various immunocomplex structures of our target protein could be efficiently produced in S. cerevisiae for future application in developing oral and injectable vaccines against various pathogens.

Supplementary Information

The online version contains supplementary material available at 10.1007/s10529-021-03161-7.

Development of a Potential Yeast-Based Vaccine Platform for Theileria parva Infection in Cattle

East Coast Fever (ECF), caused by the tick-borne apicomplexan parasite Theileria parva, remains one of the most important livestock diseases in sub-Saharan Africa with more than 1 million cattle dying from infection every year. Disease prevention relies on the so-called "Infection and Treatment Method" (ITM), which is costly, complex, laborious, difficult to standardise on a commercial scale and results in a parasite strain-specific, MHC class I-restricted cytotoxic T cell response. We therefore attempted to develop a safe, affordable, stable, orally applicable and potent subunit vaccine for ECF using five different T. parva schizont antigens (Tp1, Tp2, Tp9, Tp10 and N36) and Saccharomyces cerevisiae as an expression platform. Full-length Tp2 and Tp9 as well as fragments of Tp1 were successfully expressed on the surface of S. cerevisiae. In vitro analyses highlighted that recombinant yeast expressing Tp2 can elicit IFNγ responses using PBMCs from ITM-immunized calves, while Tp2 and Tp9 induced IFNγ responses from enriched bovine CD8⁺ T cells. A subsequent in vivo study showed that oral administration of heat-inactivated, freeze-dried yeast stably expressing Tp2 increased total murine serum IgG over time, but more importantly, induced Tp2-specific serum IgG antibodies in individual mice compared to the control group. While these results will require subsequent experiments to verify induction of protection in neonatal calves, our data indicates that oral application of yeast expressing Theileria antigens could provide an affordable and easy vaccination platform for sub-Saharan Africa. Evaluation of antigen-specific cellular immune responses, especially cytotoxic CD8⁺ T cell immunity in cattle will further contribute to the development of a yeast-based vaccine for ECF.

Saccharomyces cerevisiae (Baker's Yeast) as an Interfering RNA Expression and Delivery System

The broad application of RNA interference for disease prevention is dependent upon the production of dsRNA in an economically feasible, scalable, and sustainable fashion, as well as the identification of safe and effective methods for RNA delivery. Current research has sparked interest in the use of Saccharomyces cerevisiae for these applications. This review examines the potential for commercial development of yeast interfering RNA expression and delivery systems. S. cerevisiae is a genetic model organism that lacks a functional RNA interference system, which may make it an ideal system for expression and accumulation of high levels of recombinant interfering RNA. Moreover, recent studies in a variety of eukaryotic species suggest that this microbe may be an excellent and safe system for interfering RNA delivery. Key areas for further research and development include optimization of interfering RNA expression in S. cerevisiae, industrial-sized scaling of recombinant yeast cultures in which interfering RNA molecules are expressed, the development of methods for large-scale drying of yeast that preserve interfering RNA integrity, and identification of encapsulating agents that promote yeast stability in various environmental conditions. The genetic tractability of S. cerevisiae and a long history of using this microbe in both the food and pharmaceutical industry will facilitate further development of this promising new technology, which has many potential applications of medical importance.

Evaluation of cell-surface displayed synthetic consensus dengue EDIII cells as a potent oral vaccine candidate

BACKGROUND

Dengue is a rapidly spreading mosquito borne tropical viral disease affecting hundreds of millions of people across the globe annually. The dengue virus (DENV) includes four genetically distinct serotypes that cause serious life-threatening infections, including dengue hemorrhagic fever/dengue shock syndrome. Dengue vaccine development is complicated by the possibility of vaccine-enhanced severe dengue disease due to antibody-dependent enhancement by pre-existing cross-reactivity, as well as homotypic antibodies. Thus, the development of an efficacious dengue vaccine conferring simultaneous and durable immunity to each of the four DENV serotypes has not yet been developed despite years of research. For mass immunization in deeply affected resource-limited countries, oral vaccination is considered more beneficial than conventional approaches. Therefore, in a continuing effort towards designing economical and potent vaccine candidates, the current study applied yeast surface display technology to develop an oral dengue vaccine candidate using whole recombinant yeast cells displaying the recombinant fusion protein of M cell targeting ligand Co1 fused to the synthetic consensus dengue envelope domain III (scEDIII). Female Balb/c mice were orally fed with recombinant yeast cells and immunogenicity in terms of systemic and mucosal immune responses was monitored.

RESULTS

Immunofluorescence microscopy with dengue specific antibody and fluorescein isothiocyanate-conjugated anti-mouse IgG antibody clearly showed that recombinant protein Co1-scEDIII-AGA was localized on the cell surface of the respective clones in comparison with scEDIII-Co1 and Mock cells with no fluorescence. Oral dosage applications of surface displayed Co1-scEDIII-AGA stimulated a systemic humoral immune response in the form of dengue-specific serum IgG, as well as a mucosal immune response in the form of secretory immunoglobulin A (sIgA). Antigen-specific B cell responses in isolated lymphoid cells from the spleen and Peyer's patches further supported an elevated mucosal immune response. In addition, surface displayed Co1-scEDIII-AGA feeding elicited strong immune responses in comparison with scEDIII-Co1 and Mock following intraperitoneal booster with purified scEDIII antigen.

CONCLUSIONS

Surface displayed preparations of Co1-scEDIII-AGA induced strong immunogenicity compared with non-displayed scEDIII-Co1. Prior studies have supported the neutralization potential of scEDIII constructs against all four serotypes. Thus, the oral administration of genetically engineered yeast whole cells displaying biologically active Co1-scEDIII fusion protein without any further processing shows prospective as a potent oral vaccine candidate against dengue viral infection.

Microparticulate β-glucan vaccine conjugates phagocytized by dendritic cells activate both naïve CD4 and CD8 T cells in vitro

Microparticulate β-glucan (MG) conjugated to vaccine antigen has been shown to serve as an effective adjuvant in vivo. To further study antigen presentation by MG:vaccine conjugates, bone marrow-derived dendritic cells (BMDC) were treated with MG conjugated to ovalbumin (OVA), then interacted with splenocytes from DO11.10 transgenic mice expressing an OVA peptide-specific T cell receptor. BMDC treated with MG:OVA induced significantly higher numbers of activated (CD25+CD69+) OVA-specific CD4+ T cells than BMDC treated with OVA alone. BMDC treated with MG:OVA upregulated CD86 and CD40 expression as well as MG alone, indicating that conjugation of OVA does not alter the immunostimulatory capacity of MG. Activation of CD8+ OVA-specific OT-1 cells showed that MG:OVA is also capable of enhancing cross-presentation by BMDC to CD8+ cytotoxic T cells. These results show that MG acts as an adjuvant to enhance antigen presentation by dendritic cells to naïve, antigen-specific CD4 and CD8 T cells.

Considerations and protocols for the synthesis of custom protein labeling probes

Chemists and biologists have long recognized small molecule probes as powerful tools for functional genomics and proteomics studies. The possibility of specifically attaching chemical probes to individual proteins with spatial and temporal resolution has greatly improved our ability to visualize and characterize proteins in their native environment. The continued development of novel molecular probes for protein labeling is, therefore, of fundamental importance to gain new insights into biological processes in living cells and organisms. Several excellent approaches for the site-specific labeling of fusion proteins with chemical probes exist. Herein I discuss the design and generation of chemical probes for the SNAP-tag and CLIP-tag systems. The first part of this chapter is dedicated to reviewing the principles of the SNAP-tag technology, followed by a section dedicated to the development of chemical probes for unique applications, such as super-resolution imaging, protein trafficking and recycling, protein-protein interactions, and biomolecular sensing. The last part of the chapter contains experimental protocols and technical notes for the synthesis of selected SNAP-tag substrates and labeling of SNAP-tag fusion proteins in vitro and in living cells.

The phosphopantetheinyl transferases: catalysis of a post-translational modification crucial for life

Covering: up to 2013. Although holo-acyl carrier protein synthase, AcpS, a phosphopantetheinyl transferase (PPTase), was characterized in the 1960s, it was not until the publication of the landmark paper by Lambalot et al. in 1996 that PPTases garnered wide-spread attention being classified as a distinct enzyme superfamily. In the past two decades an increasing number of papers have been published on PPTases ranging from identification, characterization, structure determination, mutagenesis, inhibition, and engineering in synthetic biology. In this review, we comprehensively discuss all current knowledge on this class of enzymes that post-translationally install a 4'-phosphopantetheine arm on various carrier proteins.

HLA ligandome tumor antigen discovery for personalized vaccine approach

Every cancer is different and cancer cells differ from normal cells, in particular, through genetic alterations. HLA molecules on the cell surface enable T lymphocytes to recognize cellular alterations as antigens, including mutations, increase in gene product copy numbers or expression of genes usually not used in the adult organism. The search for cancer-associated antigens shared by many patients with a particular cancer has yielded a number of hits used in clinical vaccination trials with indication of survival benefit. Targeting cancer-specific antigens, which are exclusively expressed on cancer cells and not on normal cells, holds the promise for much better results and perhaps even a cure. Such antigens, however, may specifically appear in very few patients or may be mutated appearing just in one patient. Therefore, to target these in a molecularly defined way, the approach has to be individualized.

NY-ESO-1 protein glycosylated by yeast induces enhanced immune responses

Vaccine strategies that target dendritic cells to elicit potent cellular immunity are the subject of intense research. Here we report that the genetically engineered yeast Saccharomyces cerevisiae, expressing the full-length tumour-associated antigen NY-ESO-1, is a versatile host for protein production. Exposing dendritic cells (DCs) to soluble NY-ESO-1 protein linked to the yeast a-agglutinin 2 protein (Aga2p) protein resulted in protein uptake, processing and MHC class I cross-presentation of NY-ESO-1-derived peptides. The process of antigen uptake and cross-presentation was dependent on the glycosylation pattern of NY-ESO-1-Aga2p protein and the presence of accessible mannose receptors. In addition, NY-ESO-1-Aga2p protein uptake by dendritic cells resulted in recognition by HLA-DP4 NY-ESO-1-specific CD4(+) T cells, indicating MHC class II presentation. Finally, vaccination of mice with yeast-derived NY-ESO-1-Aga2p protein led to an enhanced humoral and cellular immune response, when compared to the bacterially expressed NY-ESO-1 protein. Together, these data demonstrate that yeast-derived full-length NY-ESO-1-Aga2p protein is processed and presented efficiently by MHC class I and II complexes and warrants clinical trials to determine the potential value of S. cerevisiae as a host for cancer vaccine development.

Cytosolic delivery mediated via electrostatic surface binding of protein, virus, or siRNA cargos to pH-responsive core-shell gel particles

We recently described a strategy for intracellular delivery of macromolecules, utilizing pH-responsive "core-shell" structured gel particles. These cross-linked hydrogel particles disrupt endosomes with low toxicity by virtue of physical sequestration of an endosome-disrupting "proton sponge" core inside a nontoxic hydrophilic shell. Here we tested the efficacy of this system for cytosolic delivery of a broad range of macromolecular cargos, and demonstrate the delivery of proteins, whole viral particles, or siRNA oligonucleotides into the cytosol of dendritic cells and epithelial cells via core-shell particles. We assessed the functional impact of particle delivery for vaccine applications and found that cytosolic delivery of protein antigens in dendritic cells via the core-shell particles promotes priming of CD8(+) T-cells at 100-fold lower doses than soluble protein. Functional gene knockdown following delivery of siRNA using the particles was demonstrated in epithelial cells. Based on these findings, these materials may be of interest for a broad range of biomedical applications.