Lipid-based antigen delivery systems

Nanograms of SARS-CoV-2 spike protein delivered by exosomes induce potent neutralization of both delta and omicron variants

Exosomes are emerging as potent and safe delivery carriers for use in vaccinology and therapeutics. A better vaccine for severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) is needed to provide improved, broader, longer lasting neutralization of SARS-CoV-2, a more robust T cell response, enable widespread global usage, and further enhance the safety profile of vaccines given the likelihood of repeated booster vaccinations. Here, we use Capricor's StealthXTM platform to engineer exosomes to express native SARS-CoV-2 spike Delta variant (STX-S) protein on the surface for the delivery of a protein-based vaccine for immunization against SARS-CoV-2 infection. The STX-S vaccine induced a strong immunization with the production of a potent humoral immune response as demonstrated by high levels of neutralizing antibody not only against the delta SARS-CoV-2 virus but also two Omicron variants (BA.1 and BA.5), providing broader protection than current mRNA vaccines. Additionally, both CD4+ and CD8+ T cell responses were increased significantly after treatment. Quantification of spike protein by ELISA showed that only nanograms of protein were needed to induce a potent immune response. This is a significantly lower dose than traditional recombinant protein vaccines with no adjuvant required, which makes the StealthXTM exosome platform ideal for the development of multivalent vaccines with a better safety profile. Importantly, our exosome platform allows novel proteins, or variants in the case of SARS-CoV-2, to be engineered onto the surface of exosomes in a matter of weeks, comparable with mRNA vaccine technology, but without the cold storage requirements necessary for mRNA vaccines. The ability to utilize exosomes for cellular delivery of proteins, as demonstrated by STX-S, has enormous potential to revolutionize vaccinology by rapidly facilitating antigen presentation at an extremely low dose resulting in a potent, broad antibody response.

Adjuvant physiochemistry and advanced nanotechnology for vaccine development

Vaccines comprising innovative adjuvants are rapidly reaching advanced translational stages, such as the authorized nanotechnology adjuvants in mRNA vaccines against COVID-19 worldwide, offering new strategies to effectively combat diseases threatening human health. Adjuvants are vital ingredients in vaccines, which can augment the degree, extensiveness, and longevity of antigen specific immune response. The advances in the modulation of physicochemical properties of nanoplatforms elevate the capability of adjuvants in initiating the innate immune system and adaptive immunity, offering immense potential for developing vaccines against hard-to-target infectious diseases and cancer. In this review, we provide an essential introduction of the basic principles of prophylactic and therapeutic vaccination, key roles of adjuvants in augmenting and shaping immunity to achieve desired outcomes and effectiveness, and the physiochemical properties and action mechanisms of clinically approved adjuvants for humans. We particularly focus on the preclinical and clinical progress of highly immunogenic emerging nanotechnology adjuvants formulated in vaccines for cancer treatment or infectious disease prevention. We deliberate on how the immune system can sense and respond to the physicochemical cues (e.g., chirality, deformability, solubility, topology, and chemical structures) of nanotechnology adjuvants incorporated in the vaccines. Finally, we propose possible strategies to accelerate the clinical implementation of nanotechnology adjuvanted vaccines, such as in-depth elucidation of nano-immuno interactions, antigen identification and optimization by the deployment of high-dimensional multiomics analysis approaches, encouraging close collaborations among scientists from different scientific disciplines and aggressive exploration of novel nanotechnologies.

A subunit vaccine candidate based on the Spike protein of SARS-CoV-2 prevents infectious virus shedding in cats

Of the numerous animal species affected by the SARS-CoV-2 virus, cats are one of the most susceptible, and cat-to-cat transmission has been described. Although cat-to-human infection has not, as yet, been demonstrated, preventive measures should be taken in order to avoid both viral infection in cats and transmission among them. In this respect, the application of an effective vaccine to at-risk populations would be a useful tool for controlling the disease in this species. Here, we test a new vaccine prototype based on the Spike protein of the virus in order to prevent infection and infectious virus shedding in cats. The vaccine employed in experimentation, and which is easily produced, triggered a strong neutralizing antibody response in vaccinated animals. In contrast to that which occurred with control animals, no infectious virus was detected in the oropharyngeal or rectal swabs of vaccinated cats submitted to a SARS-CoV-2 challenge. These results are of great interest as regards future considerations related to implementing vaccination programs in pets. The value of cats as vaccination trial models is also described herein.

Combined Poly(Lactide-Co-Glycolide) Microspheres Containing Diphtheria Toxoid for a Single-shot Immunization

To develop a single-shot vaccine containing diphtheria toxoid (DT) with a sufficient immune response, poly(lactide-co-glycolide) (PLGA) microspheres were prepared by water-in-oil-in-water double emulsification and solvent extraction techniques using low or high-molecular-weight PLGA (LMW-MS or HMW-MS). Stearic acid (SA) was introduced to HMW-MS (HMW/SA-MS) as a release modulator. Mean particle sizes (dvs, μm) varied between the prepared microspheres, with LMW-MS, HMW-MS, and HMW/SA-MS having the sizes of 29.83, 110.59, and 69.5 μm, respectively; however, the protein entrapment and loading efficiency did not vary, with values of 15.2-16.8 μg/mg and 61-75%, respectively. LMW-MS showed slower initial release (~ 2 weeks) but faster and higher release of antigen during weeks 3~7 than did HMW-MS. HMW/SA-MS showed rapid initial release followed by a continuous release over an extended period of time (~ 12 weeks). Mixed PLGA microspheres (MIX-MS), a combination of HMW/SA-MS and LMW-MS (1:1), demonstrated a sufficient initial antigen release and a subsequent boost release in a pulsatile manner. Serum antibody levels were measured by ELISA after DT immunization of Balb/c mice, and showed a greater response to MIX-MS than to alum-adsorbed DT (control). A lethal toxin challenge test with MIX-MS (a DT dose of 18 Lf) using Balb/c mice revealed complete protection, indicating a good candidate delivery system for a single-shot immunization.

2-Hydroxyoleic acid-inserted liposomes as a multifunctional carrier of anticancer drugs

Studies have shown that insertion of oleic acid into lipid bilayers can modulate the membrane properties of liposomes so as to improve their function as drug carriers. Considering that 2-hydroxyoleic acid (2OHOA), a potential antitumor agent currently undergoing clinical trials, is a derivative of oleic acid, we explored the possibility of developing 2OHOA-inserted liposomes as a multifunctional carrier of antitumor drugs in the present study. The insertion of 2OHOA into lipid bilayers was confirmed by surface charge determination and differential scanning calorimetry. 2OHOA insertion greatly decreased the order of dimyristoylphosphatidylcholine packing, produced a nanosized (<100 nm) dispersion, and improved the colloidal stability of liposomes during storage. Moreover, 2OHOA-inserted liposome forms exhibited greater growth inhibitory activity against cancer cells compared with free 2OHOA, and the growth-inhibitory activity of liposomal 2OHOA was selective for tumor cells. 2OHOA insertion greatly increased the liposome-incorporated concentration of hydrophobic model drugs, including mitoxantrone, paclitaxel, and all-trans retinoic acid (ATRA). The in vitro anticancer activity of ATRA-incorporated/2OHOA-inserted liposomes was significantly higher than that of ATRA-incorporated conventional liposomes. In a B16-F10 melanoma syngeneic mouse model, the tumor growth rate was significantly delayed in mice treated with ATRA-incorporated/2OHOA-inserted liposomes compared with that in the control group. Immunohistochemical analyses revealed that the enhanced antitumor activity of ATRA-incorporated/2OHOA-inserted liposomes was due, at least in part, to increased induction of apoptosis. Collectively, our findings indicate that 2OHOA-inserted liposomes exhibit multiple advantages as antitumor drug carriers, including the ability to simultaneously deliver two anticancer drugs - 2OHOA and incorporated drug - to the tumor tissue.

Vaccine adjuvants: smart components to boost the immune system

Vaccination is an effective approach to prevent the consequences of infectious diseases. Vaccines strengthen immunity and make individuals resistant to infections with pathogens. Although conventional vaccines are highly immunogenic, they are associated with some safety issues. Subunit vaccines are safe, but they require adjuvants to stimulate the immune system because of their weaker immunogenicity. Adjuvants are entities incorporated into vaccines to increase the immunogenic responses of antigens. They play a crucial role in increasing the potency and efficacy of vaccines. Different adjuvants have different modes of action; therefore, a better understanding of their immunology could provide guidance for the development of novel adjuvants. Numerous studies have been conducted using different types of adjuvants to characterize their potency and safety; however, in practice, only few are used in human or animal vaccines. This review aims to introduce the different modes of action of adjuvants and give insight into the types of adjuvants that possess the greatest potential for adjuvanticity.

Immune-camouflaged graphene oxide nanosheets for negative regulation of phagocytosis by macrophages

Signal regulatory protein alpha (SIRPα) is highly expressed in macrophages of the reticuloendothelial system and in tumor-associated macrophages, whereas tumor cells express the surface membrane protein, CD47, which interacts with SIRPα to negatively regulate phagocytosis. In this study, we modified the surfaces of graphene oxide (GO) nanosheets with a CD47-like SIRPα-binding peptide (SP). The presence of SP on GO nanosheets reduced the macrophage uptake to a greater extent than the PEGylation of such nanosheets. This reduced uptake was found to be mediated by the activation of Src homology region 2 domain-containing phosphatase 1 (SHP-1) and the downstream inhibition of myosin assembly, which is necessary for phagosome formation. Unlike SP-coated GO nanosheets, PEGylated GO nanosheets did not affect myosin assembly or phagocytosis. After in vivo systemic administration, the clearance of SP-coated GO nanosheets was slower than that of PEGylated GO nanosheets, and this difference increased with repeated administration. Finally, SP-coated GO nanosheets showed a higher distribution to tumor tissues than PEGylated GO nanosheets or a physical mixture of SP and GO nanosheets. Our findings indicate that immune-camouflaged GO nanosheets with natural CD47-like SIRPα-binding molecules can reduce the nonspecific loss of such nanosheets through macrophage uptake, thereby enhancing their blood circulation and tumor delivery after multiple injections.

Sustained release docetaxel-incorporated lipid nanoparticles with improved pharmacokinetics for oral and parenteral administration

The aim of this study was to develop docetaxel-incorporated lipid nanoparticles (DTX-NPs) to improve the pharmacokinetic behaviour of docetaxel (DTX) after oral and parenteral administration via sustained release. DTX-NPs were prepared by nanotemplate engineering technique with palmityl alcohol as a solid lipid and Tween-40/Span-40/Myrj S40 as a surfactants mixture. Spherical DTX-NPs below 100 nm were successfully prepared with a narrow particle size distribution, 96% of incorporation efficiency and 686 times increase in DTX solubility. DTX-NPs showed a sustained release over 24 h in phosphate-buffered saline and simulated gastric and intestinal fluids, while DTX-micelles released DTX completely within 12 h. The half-maximal inhibitory concentration (IC₅₀) of DTX-NPs against human breast cancer MCF-7 cells was 1.9 times lower than that of DTX-micelles and DTX solution. DTX-NPs demonstrated 3.7- and 2.8-fold increase in the area under the plasma concentration-time curve compared with DTX-micelles after oral and parenteral administration, respectively.

High payload itraconazole-incorporated lipid nanoparticles with modulated release property for oral and parenteral administration

OBJECTIVES

The aim of this study was to develop high payload itraconazole-incorporated lipid nanoparticles (HINP) with modulated release property using a binary mixture core of solid and liquid lipid for oral and parenteral administration.

METHODS

High payload itraconazole-incorporated lipid nanoparticles were prepared by hot high-pressure homogenization method using tristearin (TS) as a solid lipid, triolein (TO) as a liquid lipid and egg phosphatidylcholine/Tween 80/DSPE-PEG₂₀₀₀ as a surfactants mixture. To investigate the effects of liquid lipid in lipid core on itraconazole (ITZ) dissolution and release, TS/TO ratio was varied as 100/0, 90/10 and 80/20 (mg/mg).

KEY FINDINGS

All HINP formulations showed particle size around 300 nm and polydispersity index below 0.3. The incorporation efficiencies of HINP formulations were above 80%, and more than 40 mg of ITZ was incorporated into each HINP formulation. In-vitro dissolution and release rate of ITZ from HINP increased as the amount of TO in lipid core increased. Compared with commercial formulations of ITZ, the pharmacokinetics of ITZ was improved after oral and parenteral administration of HINP formulations containing 0% or 10% of TO in lipid core.

CONCLUSION

High payload itraconazole-incorporated lipid nanoparticles with a binary mixture lipid core have a great potential for the development of controlled release formulation of ITZ.