M-cell targeted biodegradable PLGA nanoparticles for oral immunization against hepatitis B

Optimizing the synthesis of interleukin-12-loaded PLGA nanospheres (rmIL-12ns) via ultrasonication for treatment of metastatic osteosarcoma

Clinical trials exploring bolus intravenous delivery of interleukin-12 (IL-12) for treatment of solid tumors ultimately failed due to lack of clinical response and severe dose-limiting toxicities. The present study was conducted to evaluate whether recombinant murine IL-12 (rmIL-12) could be successfully encapsulated within Poly (D, l-lactide-co-glycolide) (PLGA) nanospheres (rmIL-12ns) for safe and effective systemic delivery at pharmacologic scale. Optimal fabrication of rmIL-12ns occurs with dichloromethane as the organic solvent and emulsion formation via ultrasonication at 50% power (250 W sonicator) for 10 s (50W10s). We then determined whether utilization of synthesis modifiers including fetal bovine serum (FBS), magnesium hydroxide [Mg(OH)2 ], trehalose, or the surfactants polysorbate 80 and Span 60 alone or in combination could increase the encapsulation efficiency (EE) and/or modify the burst elution profile characteristic of the 50W10s rmIL-12ns formulation. The greatest EEs compared to the unmodified formulation were measured with modifications containing the surfactants polysorbate 80 and Span 60 (surfactant: 28.3 ± 6.10%, p = 0.29 and Surf/FBS: 85.4 ± 2.19%, p = 0.039). The Surf/FBS formulation was further modified for in vivo murine injection by substituting FBS with mouse serum albumin (MSA). The resulting Surf/MSA rmIL-12ns were then characterized before delivery at three doses (0.1, 1, and 10 mg rmIL-12ns) in our established murine model of metastatic osteosarcoma to assess efficacy. Preliminary results suggested no evidence of disease with delivery of the 0.1 mg dose in 75% of mice (3 of 4) versus a nontreated historical control (2 of 34).

Immunosuppressive Polymeric Nanoparticles Targeting Dendritic Cells Alleviate Lupus Disease in Fcgr2b-/- Mice by Mediating Antigen-Specific Immune Tolerance

Dendritic cells (DCs) are the most potent antigen-presenting cells that have multifaceted functions in the control of immune activation and tolerance. Hyperresponsiveness and altered tolerogenicity of DCs contribute to the development and pathogenesis of system lupus erythematosus (SLE); therefore, DC-targeted therapies aimed at inducing specific immune tolerance have become of great importance for the treatment of SLE. This study developed a new nanoparticle (NP) containing a biodegradable PDMAEMA-PLGA copolymer for target-oriented delivery to DCs in situ. PDMAEMA-PLGA NPs provided sustained drug release and exhibited immunosuppressive activity in FLT3L and GM-CSF-derived bone marrow in conventional DCs (BM-cDCs). PDMAEMA-PLGA NPs improved dexamethasone capability to convert wild-type and Fcgr2b^-/- BM-cDCs from an immunogenic to tolerogenic state, and BM-cDCs treated with dexamethasone-incorporated PDMAEMA-PLGA NPs (Dex-NPs) efficiently mediated regulatory T cell (Treg) expansion in vitro. Dex-NP therapy potentially alleviated lupus disease in Fcgr2b^-/- mice by mediating Foxp3⁺ Treg expansion in an antigen-specific manner. Our findings substantiate the superior efficacy of DC-targeted therapy using the PDMAEMA-PLGA NP delivery system and provide further support for clinical development as a potential therapy for SLE. Furthermore, PDMAEMA-PLGA NP may be a versatile platform for DC-targeted therapy to induce antigen-specific immune tolerance to unwanted immune responses that occur in autoimmune disease, allergy, and transplant rejection.

Surface functionalization of PLGA nanoparticles for potential oral vaccine delivery targeting intestinal immune cells

This study aimed to develop surface modified PLGA nanocarriers protecting a protein-based antigen in the stomach to enable potential release of the antigen at target intestinal sites. PLGA nanoparticles (NPs) were prepared by double emulsion and solvent evaporation techniques while surface functionalization was performed using polyethylene glycol (PEG), sodium alginate (ALG) and Eudragit L100 (EUD) with ovalbumin (OVA) as a model protein antigen. Nanoparticles were characterized by dynamic light scattering (DLS), scanning electron microscopy (SEM), Fourier-transform infrared spectroscopy (FTIR), gel permeation chromatography (GPC), and stability in simulated gastric fluid (SGF)/simulated intestinal fluid (SIF). Structural integrity of released OVA was analyzed by circular dichroism (CD) and sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE), while cytotoxicity against Jurkat cells was determined using MTT assay. Surface functionalized PLGA NPs protected the protein in SGF and SIF better than the non-functionalized NPs. Average size of OVA encapsulated NPs was between 235 and 326 nm and were spherical. FTIR band change was observed after surface modification and the surface modified NPs showed sustained OVA release compared with the uncoated NPs. The secondary structure of OVA released after 96 h remained intact and MTT assay showed >80 % cell viability after 72 h while unmodified and surface modified NPs achieved 17 % and 48 % mucin binding respectively. In conclusion, surface modified PLGA NPs have been shown to be safe for potential oral protein-based vaccine delivery.

Mucosal delivery of nanovaccine strategy against COVID-19 and its variants

Despite the global administration of approved COVID-19 vaccines (e.g., ChAdOx1 nCoV-19®, mRNA-1273®, BNT162b2®), the number of infections and fatalities continue to rise at an alarming rate because of the new variants such as Omicron and its subvariants. Including COVID-19 vaccines that are licensed for human use, most of the vaccines that are currently in clinical trials are administered via parenteral route. However, it has been proven that the parenteral vaccines do not induce localized immunity in the upper respiratory mucosal surface, and administration of the currently approved vaccines does not necessarily lead to sterilizing immunity. This further supports the necessity of a mucosal vaccine that blocks the main entrance route of COVID-19: nasal and oral mucosal surfaces. Understanding the mechanism of immune regulation of M cells and dendritic cells and targeting them can be another promising approach for the successful stimulation of the mucosal immune system. This paper reviews the basic mechanisms of the mucosal immunity elicited by mucosal vaccines and summarizes the practical aspects and challenges of nanotechnology-based vaccine platform development, as well as ligand hybrid nanoparticles as potentially effective target delivery agents for mucosal vaccines.

Immunoadjuvant and Humoral Immune Responses of Garlic (Allium sativum L.) Lectins upon Systemic and Mucosal Administration in BALB/c Mice

Dietary food components have the ability to affect immune function; following absorption, specifically orally ingested dietary food containing lectins can systemically modulate the immune cells and affect the response to self- and co-administered food antigens. The mannose-binding lectins from garlic (Allium sativum agglutinins; ASAs) were identified as immunodulatory proteins in vitro. The objective of the present study was to assess the immunogenicity and adjuvanticity of garlic agglutinins and to evaluate whether they have adjuvant properties in vivo for a weak antigen ovalbumin (OVA). Garlic lectins (ASA I and ASA II) were administered by intranasal (50 days duration) and intradermal (14 days duration) routes, and the anti-lectin and anti-OVA immune (IgG) responses in the control and test groups of the BALB/c mice were assessed for humoral immunogenicity. Lectins, co-administered with OVA, were examined for lectin-induced anti-OVA IgG response to assess their adjuvant properties. The splenic and thymic indices were evaluated as a measure of immunomodulatory functions. Intradermal administration of ASA I and ASA II had showed a four-fold and two-fold increase in anti-lectin IgG response, respectively, vs. the control on day 14. In the intranasal route, the increases were 3-fold and 2.4-fold for ASA I and ASA II, respectively, on day 50. No decrease in the body weights of animals was noticed; the increases in the spleen and thymus weights, as well as their indices, were significant in the lectin groups. In the adjuvanticity study by intranasal administration, ASA I co-administered with ovalbumin (OVA) induced a remarkable increase in anti-OVA IgG response (~six-fold; p < 0.001) compared to the control, and ASA II induced a four-fold increase vs. the control on day 50. The results indicated that ASA was a potent immunogen which induced mucosal immunogenicity to the antigens that were administered intranasally in BALB/c mice. The observations made of the in vivo study indicate that ASA I has the potential use as an oral and mucosal adjuvant to deliver candidate weak antigens. Further clinical studies in humans are required to confirm its applicability.

Nanocarriers-Assisted Needle-Free Vaccine Delivery Through Oral and Intranasal Transmucosal Routes: A Novel Therapeutic Conduit

Drug delivery using oral route is the most popular, convenient, safest and least expensive approach. It includes oral transmucosal delivery of bioactive compounds as the mucosal cavity offers an intriguing approach for systemic drug distribution. Owing to the dense vascular architecture and high blood flow, oral mucosal layers are easily permeable and can be an ideal site for drug administration. Recently, the transmucosal route is being investigated for other therapeutic candidates such as vaccines for their efficient delivery. Vaccines have the potential to trigger immune reactions and can act as both prophylactic and therapeutic conduit to a variety of diseases. Administration of vaccines using transmucosal route offers multiple advantages, the most important one being the needle-free (non-invasive) delivery. Development of needle-free devices are the most recent and pioneering breakthrough in the delivery of drugs and vaccines, enabling patients to avoid needles, reducing anxiety, pain and fear as well as improving compliance. Oral, nasal and aerosol vaccination is a novel immunization approach that utilizes a nanocarrier to administer the vaccine. Nanocarriers improve the bioavailability and serve as adjuvants to elicit a stronger immune response, resulting in increased effectiveness of vaccination. Drugs and vaccines with lower penetration abilities can also be delivered transmucosally while maintaining their biological function. The development of micro/nanocarriers for transmucosal delivery of macromolecules, vaccines and other substances is currently drawing much attention and a number of studies were performed recently. This comprehensive review is aimed to summarize the most recent investigations on needle-free and non-invasive approaches for the delivery of vaccines using oral transmucosal route, their strengths and associated challenges. The oral transmucosal vaccine delivery by nanocarriers is the most upcoming advancement in efficient vaccine delivery and this review would help further research and trials in this field.

Engineering Nano- and Microparticles as Oral Delivery Vehicles to Promote Intestinal Lymphatic Drug Transport

Targeted oral delivery of a drug via the intestinal lymphatic system (ILS) has the advantages of protecting against hepatic first-pass metabolism of the drug and improving its pharmacokinetic performance. It is also a promising route for the oral delivery of vaccines and therapeutic agents to induce mucosal immune responses and treat lymphatic diseases, respectively. This article describes the anatomical structures and physiological characteristics of the ILS, with an emphasis on enterocytes and microfold (M) cells, which are the main gateways for the transport of particulate delivery vehicles across the intestinal epithelium into the lymphatics. A comprehensive overview of recent advances in the rational engineering of particulate vehicles, along with the challenges and opportunities that they present for improving ILS drug delivery, is provided, and the mechanisms by which such vehicles target and transport through enterocytes or M cells are discussed. The use of naturally sourced materials, such as yeast microcapsules and their derived polymeric β-glucans, as novel ILS-targeting delivery vehicles is also reviewed. Such use is the focus of an emerging field of research. Their potential use in the oral delivery of nucleic acids, such as mRNA vaccines, is proposed.

Advancedoral vaccine delivery strategies for improving the immunity

Infectious diseases continue to inflict a high global disease burden. The consensus is that vaccination is the most effective option against infectious diseases. Oral vaccines have unique advantages in the prevention of global pandemics due to their ease of use, high compliance, low cost, and the ability to induce both systemic and mucosal immune responses. However, challenges of adapting vaccines for oral administration remain significant. Foremost among these are enzymatic and pH-dependent degradation of antigens in the stomach and intestines, the low permeability of mucus barrier, the nonspecific uptake of antigens at the intestinal mucosal site, and the immune suppression result from the elusive immune tolerance mechanisms. Innovative delivery techniques promise great potential for improving the flexibility and efficiency of oral vaccines. A better understanding of the delivery approaches and the immunological mechanisms of oral vaccine delivery systems may provide new scientific insight and tools for developing the next-generation oral vaccine. Here, an overview of the advanced technologies in the field of oral vaccination is proposed, including mucus-penetrating nanoparticle (NP), mucoadhesive delivery vehicles, targeting antigen-presenting cell (APC) nanocarriers and enhanced paracellular delivery strategies and so on. Meanwhile, the mechanisms of delivery vectors interact with mucosal barriers are discussed.

Molecular and cellular cues governing nanomaterial-mucosae interactions: from nanomedicine to nanotoxicology

Mucosal tissues constitute the largest interface between the body and the surrounding environment and they regulate the access of molecules, supramolecular structures, particulate matter, and pathogens into it. All mucosae are characterized by an outer mucus layer that protects the underlying cells from physicochemical, biological and mechanical insults, a mono-layered or stratified epithelium that forms tight junctions and controls the selective transport of solutes across it and associated lymphoid tissues that play a sentinel role. Mucus is a gel-like material comprised mainly of the glycoprotein mucin and water and it displays both hydrophilic and hydrophobic domains, a net negative charge, and high porosity and pore interconnectivity, providing an efficient barrier for the absorption of therapeutic agents. To prolong the residence time, absorption and bioavailability of a broad spectrum of active compounds upon mucosal administration, mucus-penetrating and mucoadhesive particles have been designed by tuning the chemical composition, the size, the density, and the surface properties. The benefits of utilizing nanomaterials that interact intimately with mucosae by different mechanisms in the nanomedicine field have been extensively reported. To ensure the safety of these nanosystems, their compatibility is evaluated in vitro and in vivo in preclinical and clinical trials. Conversely, there is a growing concern about the toxicity of nanomaterials dispersed in air and water effluents that unintentionally come into contact with the airways and the gastrointestinal tract. Thus, deep understanding of the key nanomaterial properties that govern the interplay with mucus and tissues is crucial for the rational design of more efficient drug delivery nanosystems (nanomedicine) and to anticipate the fate and side-effects of nanoparticulate matter upon acute or chronic exposure (nanotoxicology). This review initially overviews the complex structural features of mucosal tissues, including the structure of mucus, the epithelial barrier, the mucosal-associated lymphatic tissues and microbiota. Then, the most relevant investigations attempting to identify and validate the key particle features that govern nanomaterial-mucosa interactions and that are relevant in both nanomedicine and nanotoxicology are discussed in a holistic manner. Finally, the most popular experimental techniques and the incipient use of mathematical and computational models to characterize these interactions are described.

An ex vivo investigation of the intestinal uptake and translocation of nanoparticles targeted to Peyer's patches microfold cells

Diverse nanoparticulate systems have been engineered as vehicles towards enhancing the bioavailability of orally administrated vaccines. Substantial evidence suggests that targeting microfold cells (M cells) within Peyer's patches (PPs) is a prerequisite for vaccine-loaded nanocarriers to induce an effective antigen-specific immune response. Improved understanding of the contribution of M cells to sampling luminal nanoparticles into the underlying gut associated lymphoid tissues would accelerate the development of oral vaccine formulations. Herein, a novel clearing-based whole tissue mount/imaging technique was developed to enable the specific distribution of nanoparticles within ex vivo murine PPs to be quantitatively determined at the cellular level. This revealed that 200 nm nanoparticles modified with M cell targeting ligands (lectin Ulex europaeus agglutinin-1, UEA-1) were translocated into subepithelial domes 7.6 and 16.3 times greater than the non-targeted ones at 60 min and 120 min, respectively. This approach provides a new methodology to quantitatively investigate the transcytotic activity of M cells for particulate formulations, which may aid in the design of improved oral vaccines.

The construction of in vitro nasal cavity-mimic M-cell model, design of M cell-targeting nanoparticles and evaluation of mucosal vaccination by nasal administration

In order to better evaluate the transport effect of nanoparticles through the nasal mucosa, an in vitro nasal cavity-mimic model was designed based on M cells. The differentiation of M cells was induced by co-culture of Calu-3 and Raji cells in invert model. The ZO-1 protein staining and the transport of fluorescein sodium and dexamethasone showed that the inverted co-culture model formed a dense monolayer and possessed the transport ability. The differentiation of M cells was observed by up-regulated expression of Sialyl Lewis A antigen (SLAA) and integrin β1, and down-regulated activity of alkaline phosphatase. After targeting M cells with iRGD peptide (cRGDKGPDC), the transport of nanoparticles increased. In vivo, the co-administration of iRGD could result in the increase of nanoparticles transported to the brain through the nasal cavity after intranasal administration. In the evaluation of immune effect in vivo, the nasal administration of OVA-PLGA/iRGD led to more release of IgG, IFN-γ, IL-2 and secretory IgA (sIgA) compared with OVA@PLGA group. Collectively, the study constructed in vitro M cell model, and proved the enhanced effect of targeting towards M cell with iRGD on improving nasal immunity.

Nanoparticle-based vaccine development and evaluation against viral infections in pigs

Virus infections possess persistent health challenges in swine industry leading to severe economic losses worldwide. The economic burden caused by virus infections such as Porcine Reproductive and Respiratory Syndrome Virus, Swine influenza virus, Porcine Epidemic Diarrhea Virus, Porcine Circovirus 2, Foot and Mouth Disease Virus and many others are associated with severe morbidity, mortality, loss of production, trade restrictions and investments in control and prevention practices. Pigs can also have a role in zoonotic transmission of some viral infections to humans. Inactivated and modified-live virus vaccines are available against porcine viral infections with variable efficacy under field conditions. Thus, improvements over existing vaccines are necessary to: (1) Increase the breadth of protection against evolving viral strains and subtypes; (2) Control of emerging and re-emerging viruses; (3) Eradicate viruses localized in different geographic areas; and (4) Differentiate infected from vaccinated animals to improve disease control programs. Nanoparticles (NPs) generated from virus-like particles, biodegradable and biocompatible polymers and liposomes offer many advantages as vaccine delivery platform due to their unique physicochemical properties. NPs help in efficient antigen internalization and processing by antigen presenting cells and activate them to elicit innate and adaptive immunity. Some of the NPs-based vaccines could be delivered through both parenteral and mucosal routes to trigger efficient mucosal and systemic immune responses and could be used to target specific immune cells such as mucosal microfold (M) cells and dendritic cells (DCs). In conclusion, NPs-based vaccines can serve as novel candidate vaccines against several porcine viral infections with the potential to enhance the broader protective efficacy under field conditions. This review highlights the recent developments in NPs-based vaccines against porcine viral pathogens and how the NPs-based vaccine delivery system induces innate and adaptive immune responses resulting in varied level of protective efficacy.

Biomimetic and bioinspired strategies for oral drug delivery

Oral drug delivery remains the most preferred approach due to its multiple advantages. Recently there has been increasing interest in the development of advanced vehicles for oral delivery of different therapeutics. Among them, biomimetic and bioinspired strategies are emerging as novel approaches that are promising for addressing biological barriers encountered by traditional drug delivery systems. Herein we provide a state-of-the-art review on the current progress of biomimetic particulate oral delivery systems. Different biomimetic nanoparticles used for oral drug delivery are first discussed, mainly including ligand/antibody-functionalized nanoparticles, transporter-mediated nanoplatforms, and nanoscale extracellular vesicles. Then we describe bacteria-derived biomimetic systems, with respect to oral delivery of therapeutic proteins or antigens. Subsequently, yeast-derived oral delivery systems, based on either chemical engineering or bioengineering approaches are discussed, with emphasis on the treatment of inflammatory diseases and cancer as well as oral vaccination. Finally, bioengineered plant cells are introduced for oral delivery of biological agents. A future perspective is also provided to highlight the existing challenges and possible resolution toward clinical translation of currently developed biomimetic oral therapies.

Chylomicron mimicking solid lipid nanoemulsions encapsulated enteric minicapsules targeted to colon for immunization against hepatitis B

The oral route is one of the most convenient routes for drug and/or vaccine delivery. Yet variable nature of gastrointestinal tract due to transient changes in pH, physiology, and flora throughout the gut together with hostile nature of peptide drugs/vaccines when given by this route results in limited success. Colon targeting is a recent area of interest for most of the research among which hard gelatin coated capsules is one such important and useful contrivance. The present study assesses the mucosal immunization with HBsAg loaded lyophilized nanoparticles delivered in the colonic region using enteric coated minicapsules. Designed minicapsules offers better compliance and oral vaccine antigen delivery to the colonic region which involving mucosal exposure thus mimicking the natural pathogen entry in the body. The present study is an extension of our reported work where nanoparticles were administered to the colon through the rectal route. Lyophilized nanoparticles were characterized for particle size, in-vitro release and antigen integrity along with cell uptake study. Particles had ~241 ± 32 nm sizes, flattened yet spherical in morphology. Enteric coated minicapsules were evaluated for size, coating thickness, and dissolution profile. In-vivo immune response assured its immunogenic potential with profound IgG (485 ± 41 mIU/ml) and IgA (885 ± 126 mIU/ml) antibody production as compared to marketed recombinant hepatitis B antigen formulation (Gene Vac-B®) which induce IgG and IgA titer; 1027 ± 62 mIU/ml and 220 ± 11 mIU/ml respectively following well established immunization protocol. Former induced significant mucosal immunity due to the involvement of Common Mucosal Immune System (CMIS). The study supports the workable novel approach for immune protection against hepatitis B.

Needle-Free Immunization with Chitosan-Based Systems

Despite successful use, needle-based immunizations have several issues such as the risk of injuries and infections from the reuse of needles and syringes and the low patient compliance due to pain and fear of needles during immunization. In contrast, needle-free immunizations have several advantages including ease of administration, high level of patient compliance and the possibility of mass vaccination. Thus, there is an increasing interest on developing effective needle-free immunizations via cutaneous and mucosal approaches. Here, we discuss several methods of needle-free immunizations and provide insights into promising use of chitosan systems for successful immunization.

M cell targeting engineered biomaterials for effective vaccination

Vaccines are one of the greatest medical interventions of all time and have been successful in controlling and eliminating a myriad of diseases over the past two centuries. Among several vaccination strategies, mucosal vaccines have wide clinical applications and attract considerable interest in research, showing potential as innovative and novel therapeutics. In mucosal vaccination, targeting (microfold) M cells is a frontline prerequisite for inducing effective antigen-specific immunostimulatory effects. In this review, we primarily focus on materials engineered for use as vaccine delivery platforms to target M cells. We also describe potential M cell targeting areas, methods to overcome current challenges and limitations of the field. Furthermore, we present the potential of biomaterials engineering as well as various natural and synthetic delivery technologies to overcome the challenges of M cell targeting, all of which are absent in current literature. Finally, we briefly discuss manufacturing and regulatory processes to bring a robust perspective on the feasibility and potential of this next-generation vaccine technology.

Peptide and protein nanoparticle conjugates: versatile platforms for biomedical applications

Peptide- and protein-nanoparticle conjugates have emerged as powerful tools for biomedical applications, enabling the treatment, diagnosis, and prevention of disease. In this review, we focus on the key roles played by peptides and proteins in improving, controlling, and defining the performance of nanotechnologies. Within this framework, we provide a comprehensive overview of the key sequences and structures utilised to provide biological and physical stability to nano-constructs, direct particles to their target and influence their cellular and tissue distribution, induce and control biological responses, and form polypeptide self-assembled nanoparticles. In doing so, we highlight the great advances made by the field, as well as the challenges still faced in achieving the clinical translation of peptide- and protein-functionalised nano-drug delivery vehicles, imaging species, and active therapeutics.

Properties and applications of nanoparticle/microparticle conveyors with adjuvant characteristics suitable for oral vaccination

Vaccination is one of the most effective approaches in the prevention and control of disease worldwide. Oral vaccination could have wide applications if effective protection cannot be achieved through traditional (eg, parenteral) routes of vaccination. However, oral administration is hampered by the difficulties in transferring vaccines in vivo. This has led to the development of materials such as carriers with potential adjuvant effects. Considering the requirements for selecting adjuvants for oral vaccines as well as the advantages of nanoparticle/microparticle materials as immune effectors and antigen conveyors, synthetic materials could improve the efficiency of oral vaccination. In this review, nanoparticles and microparticles with adjuvant characteristics are described with regard to their potential importance for oral immunization, and some promising and successful modification strategies are summarized.

Characterization of Vibrio cholerae neuraminidase as an immunomodulator for novel formulation of oral allergy immunotherapy

To improve current mucosal allergen immunotherapy Vibrio cholerae neuraminidase (NA) was evaluated as a novel epithelial targeting molecule for functionalization of allergen-loaded, poly(D,L-lactide-co-glycolide) (PLGA) microparticles (MPs) and compared to the previously described epithelial targeting lectins wheat germ agglutinin (WGA) and Aleuria aurantia lectin (AAL). All targeters revealed binding to Caco-2 cells, but only NA had high binding specificity to α-L fucose and monosialoganglioside-1. An increased transepithelial uptake was found for NA-MPs in a M-cell co-culture model. NA and NA-MPs induced high levels of IFN-γ and IL10 in naive mouse splenocytes and CCL20 expression in Caco-2. Repeated oral gavage of NA-MPs resulted in a modulated, allergen-specific immune response. In conclusion, NA has enhanced M-cell specificity compared to the other targeters. NA functionalized MPs induce a Th1 and T-regulatory driven immune response and avoid allergy effector cell activation. Therefore, it is a promising novel, orally applied formula for allergy therapy.

Virus-Like Particle, Liposome, and Polymeric Particle-Based Vaccines against HIV-1

It is acknowledged that vaccines remain the best hope for eliminating the HIV-1 epidemic. However, the failure to produce effective vaccine immunogens and the inability of conventional delivery strategies to elicit the desired immune responses remains a central theme and has ultimately led to a significant roadblock in HIV vaccine development. Consequently, significant efforts have been applied to generate novel vaccine antigens and delivery agents, which mimic viral structures for optimal immune induction. Here, we review the latest developments that have occurred in the nanoparticle vaccine field, with special emphasis on strategies that are being utilized to attain highly immunogenic, systemic, and mucosal anti-HIV humoral and cellular immune responses. This includes the design of novel immunogens, the central role of antigen-presenting cells, delivery routes, and biodistribution of nanoparticles to lymph nodes. In particular, we will focus on virus-like-particle formulations and their preclinical uses within the HIV prophylactic vaccine setting.

Chemical Modification of Chitosan for Efficient Vaccine Delivery

Chitosan, which exhibits good biocompatibility, safety, microbial degradation and other excellent performances, has found application in all walks of life. In the field of medicine, usage of chitosan for the delivery of vaccine is favored by a wide range of researchers. However, due to its own natural limitations, its application has been constrained to the beginning of study. In order to improve the applicability for vaccine delivery, researchers have carried out various chemical modifications of chitosan. This review summarizes a variety of modification methods and applications of chitosan and its derivatives in the field of vaccine delivery.

Thermostability of the coating, antigen and immunostimulator in an adjuvanted oral capsule vaccine formulation

Oral vaccines present an attractive alternative to injectable vaccines for enteric diseases due to ease of delivery and the induction of intestinal immunity at the site of infection. However, susceptibility to gastrointestinal proteolysis, limited transepithelial uptake and a lack of clinically acceptable adjuvants present significant challenges. A further challenge to mass vaccination in developing countries is the very expensive requirement to maintain the cold chain. We recently described the effectiveness of a Single Multiple Pill^® (SmPill^®) adjuvanted capsule approach to enhance the effectiveness of a candidate enterotoxigenic Escherichia coli (ETEC) oral vaccine. Here it was demonstrated that this delivery system maintains the antigenicity of ETEC colonisation factor antigen I (CFA/I) and the immunostimulatory activity of the orally active α-Galactosylceramide (α-GalCer) adjuvant after storage of SmPill^® minispheres under room temperature and extreme storage conditions for several months. In addition, the internal structure of the cores of SmPill^® minispheres and antigen release features at intestinal pH were found to be preserved under all these conditions. However, changes in the surface morphology of SmPill^® minispheres leading to the antigen release at gastric pH were observed after a few weeks of storage under extreme conditions. Those modifications were prevented by the introduction of an Opadry^® White film coating layer between the core of SmPill^® minispheres and the enteric coating. Under these conditions, protection against antigen release at gastric pH was maintained even under high temperature and humidity conditions. These results support the potential of the SmPill^® minisphere approach to maintain the stability of an adjuvanted whole cell killed oral vaccine formulation.

Current state and challenges in developing oral vaccines

While vaccination remains the most cost effective strategy for disease prevention, communicable diseases persist as the second leading cause of death worldwide. There is a need to design safe, novel vaccine delivery methods to protect against unaddressed and emerging diseases. Development of vaccines administered orally is preferable to traditional injection-based formulations for numerous reasons including improved safety and compliance, and easier manufacturing and administration. Additionally, the oral route enables stimulation of humoral and cellular immune responses at both systemic and mucosal sites to establish broader and long-lasting protection. However, oral delivery is challenging, requiring formulations to overcome the harsh gastrointestinal (GI) environment and avoid tolerance induction to achieve effective protection. Here we address the rationale for oral vaccines, including key biological and physicochemical considerations for next-generation oral vaccine design.

Regulatory aspects in the pharmaceutical development of nanoparticle drug delivery systems designed to cross the intestinal epithelium and M-cells

This article reviews the field of oral uptake of nanoparticles across the gastrointestinal epithelium for the period 2006-2016. Analysis is conducted from the viewpoint of i) M-cell genetics and model development, ii) drug targeting to Peyer's patches and M-cells, and iii) physicochemical interactions of nanoparticles in the intestinal milieu. In light of these recent developments, regulatory considerations in the development of orally-absorbable nanoparticle drug products are discussed and focused on Module 3.2.P sub-sections of the Common Technical Document. Particular attention is paid to novel excipients, ligands and the non-standard method of manufacture. The novelty of this drug delivery system demands not only a multi-disciplinary scientific and regulatory approach but also a risk-adjusted consideration for a system defined by both processes and specifications. Given the current state of scientific development in the field it is suggested (in the author's personal opinion) that the design of nanoparticulate drug delivery systems should be kept as simple as possible (from a regulatory and manufacturing perspective) and to target the entire gastrointestinal epithelium.

Chemical Synthesis, Versatile Structures and Functions of Tailorable Adjuvants for Optimizing Oral Vaccination

Oral vaccines have become a recent focus because of their potential significance in disease prevention and therapy. In the development of oral vaccine-based therapeutics, synthetic materials with tailorable structures and versatile functions can act as antigen conveyers with adjuvant effects, reduce the time cost for vaccine optimization, and provide high security and enhanced immunity. This review presents an overview of the current status of tailoring synthetic adjuvants for oral vaccination, modification strategies for producing effectors with specific structures and functions, enhancement of immune-associated efficiencies, including the barrier-crossing capability to protect antigens in the gastrointestinal tract, coordination of the antigens penetrating mucosa and cell barriers, targeting of concentrated antigens to immune-associated cells, and direct stimulation of immune cells. Finally, we focus on prospective synthetic adjuvants that facilitate the use of oral vaccines via two approaches, namely, in vivo antigen expression and cancer immunotherapy.

Immunological evaluation of colonic delivered Hepatitis B surface antigen loaded TLR-4 agonist modified solid fat nanoparticles

Hepatitis B is one of the leading liver diseases and remains a major global health problem. Currently available vaccines provide protection but often results in weaker/minimal mucosal immunity. Thus the present study is devoted to the development and in-vivo exploration of the colonically delivered biomimetic nanoparticles which capably enhance humoral as well as cellular immune response. In present work, Hepatitis B surface antigen (HBsAg) entrapped nanoparticles containing Monophosphoryl lipid A (MPLA) (HB+L-NP) were prepared by solvent evaporation method and characterized for particle size (~210nm), shape, zeta potential (-24mV±0.68), entrapment efficiency (58.45±1.68%), in-vitro release and antigen integrity. Dose escalation study was done to confirm prophylactic immune response following defined doses of prepared nanoparticulate formulations with or without MPLA. Intramuscular administered alum based marketed HBsAg (Genevac B) was used as standard (10μg) and were able to induce significant systemic (IgG) but remarkably low mucosal immune (IgA) response. Notably, HB+L-NP (0.5ml-10μg) induced strong systemic and robust mucosal immunity (510 and 470 mIU/ml respectively, p<0.001) from which mucosal was more significant due to the involvement of Common Mucosal Immune System (CMIS). Likewise, significant cellular immune response was elicited by HB+L-NP through T-cell activation (mixed Th1 and Th2) as confirmed by significantly increased cytokines level (IL-2 and Interferon-γ) in spleen homogenates. This study supports that delivery of HBsAg to the colon may open new vista in designing oral vaccines later being one of most accepted route for potential vaccines in future.

Biomimetic strategies for targeted nanoparticle delivery

Nanoparticle‐based drug delivery and imaging platforms have become increasingly popular over the past several decades. Among different design parameters that can affect their performance, the incorporation of targeting functionality onto nanoparticle surfaces has been a widely studied subject. Targeted formulations have the ability to improve efficacy and function by positively modulating tissue localization. Many methods exist for creating targeted nanoformulations, including the use of custom biomolecules such as antibodies or aptamers. More recently, a great amount of focus has been placed on biomimetic targeting strategies that leverage targeting interactions found directly in nature. Such strategies, which have been painstakingly selected over time by the process of evolution to maximize functionality, oftentimes enable scientists to forgo the specialized discovery processes associated with many traditional ligands and help to accelerate development of novel nanoparticle formulations. In this review, we categorize and discuss in‐depth recent works in this growing field of bioinspired research.

Chitosan-Alginate Microcapsules Provide Gastric Protection and Intestinal Release of ICAM-1-Targeting Nanocarriers, Enabling GI Targeting In Vivo

When administered intravenously, active targeting of drug nanocarriers (NCs) improves biodistribution and endocytosis. Targeting may also improve oral delivery of NCs to treat gastrointestinal (GI) pathologies or for systemic absoption. However, GI instability of targeting moieties compromises this strategy. We explored whether encapsulation of antibody-coated NCs in microcapsules would protect against gastric degradation, providing NCs release and targeting in intestinal conditions. We used nanoparticles coated with antibodies against intercellular adhesion molecule-1 (anti-ICAM) or non-specific IgG. NCs (~160-nm) were encapsulated in ~180-μm microcapsules with an alginate core, in the absence or presence of a chitosan shell. We found >95% NC encapsulation within microcapsules and <10% NC release from microcapsules in storage. There was minimal NC release at gastric pH (<10%) and burst release at intestinal pH (75-85%), slightly attenuated by chitosan. Encapsulated NCs afforded increased protection against degradation (3-4 fold) and increased cell targeting (8-20 fold) after release vs. non-encapsulated NCs. Mouse oral gavage showed that microencapsulation provided 38-65% greater protection of anti-ICAM NCs in the GI tract, 40% lower gastric retention, and 4-9-fold enhanced intestinal biodistribution vs. non-encapsulated NCs. Therefore, microencapsulation of antibody-targeted NCs may enable active targeting strategies to be effective in the context of oral drug delivery.

Peptide/protein vaccine delivery system based on PLGA particles

Due to the excellent safety profile of poly (D,L-lactide-co-glycolide) (PLGA) particles in human, and their biodegradability, many studies have focused on the application of PLGA particles as a controlled-release vaccine delivery system. Antigenic proteins/peptides can be encapsulated into or adsorbed to the surface of PLGA particles. The gradual release of loaded antigens from PLGA particles is necessary for the induction of efficient immunity. Various factors can influence protein release rates from PLGA particles, which can be defined intrinsic features of the polymer, particle characteristics as well as protein and environmental related factors. The use of PLGA particles encapsulating antigens of different diseases such as hepatitis B, tuberculosis, chlamydia, malaria, leishmania, toxoplasma and allergy antigens will be described herein. The co-delivery of antigens and immunostimulants (IS) with PLGA particles can prevent the systemic adverse effects of immunopotentiators and activate both dendritic cells (DCs) and natural killer (NKs) cells, consequently enhancing the therapeutic efficacy of antigen-loaded PLGA particles. We will review co-delivery of different TLR ligands with antigens in various models, highlighting the specific strengths and weaknesses of the system. Strategies to enhance the immunotherapeutic effect of DC-based vaccine using PLGA particles can be designed to target DCs by functionalized PLGA particle encapsulating siRNAs of suppressive gene, and disease specific antigens. Finally, specific examples of cellular targeting where decorating the surface of PLGA particles target orally administrated vaccine to M-cells will be highlighted.

PLGA particulate delivery systems for subunit vaccines: Linking particle properties to immunogenicity

Among the emerging subunit vaccines are recombinant protein- and synthetic peptide-based vaccine formulations. However, proteins and peptides have a low intrinsic immunogenicity. A common strategy to overcome this is to co-deliver (an) antigen(s) with (an) immune modulator(s) by co-encapsulating them in a particulate delivery system, such as poly(lactic-co-glycolic acid) (PLGA) particles. Particulate PLGA formulations offer many advantages for antigen delivery as they are biocompatible and biodegradable; can protect the antigens from degradation and clearance; allow for co-encapsulation of antigens and immune modulators; can be targeted to antigen presenting cells; and their particulate nature can increase uptake and cross-presentation by mimicking the size and shape of an invading pathogen. In this review we discuss the pros and cons of using PLGA particulate formulations for subunit vaccine delivery and provide an overview of formulation parameters that influence their adjuvanticity and the ensuing immune response.

Tracking translocation of glucan microparticles targeting M cells: implications for oral drug delivery

Model glucan microparticles (GMs) targeting M cells are employed to track translocation through M cell pathways as well as to various organsviathe systemic circulation.

Respiratory nanoparticle-based vaccines and challenges associated with animal models and translation

Vaccine development has had a huge impact on human health. However, there is a significant need to develop efficacious vaccines for several existing as well as emerging respiratory infectious diseases. Several challenges need to be overcome to develop efficacious vaccines with translational potential. This review focuses on two aspects to overcome some barriers - 1) the development of nanoparticle-based vaccines, and 2) the choice of suitable animal models for respiratory infectious diseases that will allow for translation. Nanoparticle-based vaccines, including subunit vaccines involving synthetic and/or natural polymeric adjuvants and carriers, as well as those based on virus-like particles offer several key advantages to help overcome the barriers to effective vaccine development. These include the ability to deliver combinations of antigens, target the vaccine formulation to specific immune cells, enable cross-protection against divergent strains, act as adjuvants or immunomodulators, allow for sustained release of antigen, enable single dose delivery, and potentially obviate the cold chain. While mouse models have provided several important insights into the mechanisms of infectious diseases, they are often a limiting step in translation of new vaccines to the clinic. An overview of different animal models involved in vaccine research for respiratory infections, with advantages and disadvantages of each model, is discussed. Taken together, advances in nanotechnology, combined with the right animal models for evaluating vaccine efficacy, has the potential to revolutionize vaccine development for respiratory infections.

Roles of M cells in infection and mucosal vaccines

The mucosal immune system plays a crucial part in the control of infection. Exposure of humans and animals to potential pathogens generally occurs through mucosal surfaces, thus, strategies that target the mucosa seem rational and efficient vaccination measures. Vaccination through the mucosal immune system can induce effective systemic immune responses simultaneously with mucosal immunity compared with parenteral vaccination. M cells are capable of transporting luminal antigens to the underlying lymphoid tissues and can be exploited by pathogens as an entry portal to invade the host. Therefore, targeting M-cell-specific molecules might enhance antigen entry, initiate the immune response, and induce protection against mucosal pathogens. Here, we outline our understanding of the distribution and function of M cells, and summarize the advances in mucosal vaccine strategies that target M cells.

Mimicking microbial strategies for the design of mucus-permeating nanoparticles for oral immunization

Dealing with mucosal delivery systems means dealing with mucus. The name mucosa comes from mucus, a dense fluid enriched in glycoproteins, such as mucin, which main function is to protect the delicate mucosal epithelium. Mucus provides a barrier against physiological chemical and physical aggressors (i.e., host secreted digestive products such as bile acids and enzymes, food particles) but also against the potentially noxious microbiota and their products. Intestinal mucosa covers 400m(2) in the human host, and, as a consequence, is the major portal of entry of the majority of known pathogens. But, in turn, some microorganisms have evolved many different approaches to circumvent this barrier, a direct consequence of natural co-evolution. The understanding of these mechanisms (known as virulence factors) used to interact and/or disrupt mucosal barriers should instruct us to a rational design of nanoparticulate delivery systems intended for oral vaccination and immunotherapy. This review deals with this mimetic approach to obtain nanocarriers capable to reach the epithelial cells after oral delivery and, in parallel, induce strong and long-lasting immune and protective responses.

Poly(lactic acid) and poly(lactic-co-glycolic acid) particles as versatile carrier platforms for vaccine delivery

The development of safe and effective vaccines for cancer and infectious diseases remains a major goal in public health. Over the last two decades, controlled release of vaccine antigens and immunostimulant molecules has been achieved using nanometer or micron-sized delivery vehicles synthesized using biodegradable polymers. In addition to achieving a depot effect, enhanced vaccine efficacy using such delivery vehicles has been attributed to efficient targeting of antigen presenting cells such as dendritic cells. Biodegradable and biocompatible poly(lactic acid) and poly(lactic-co-glycolic acid) polymers belong to one such family of polymers that have been a popular choice of material used in the design of these delivery vehicles. This review summarizes research findings from ourselves and others highlighting the promise of poly(lactic acid)- and poly(lactic-co-glycolic acid)-based vaccine carriers in enhancing immune responses.

Nanomaterials for enhanced immunity as an innovative paradigm in nanomedicine

Since the advent of nanoparticle technology, novel and versatile properties of nanomaterials have been introduced, which has constantly expanded their applications in therapeutics. Introduction of nanomaterials for immunomodulation has opened up new avenues with tremendous potential. Interesting properties of nanoparticles, such as adjuvanticity, capability to enhance cross-presentation, polyvalent presentation, siRNA delivery for silencing of immunesuppressive gene, targeting and imaging of immune cells have been known to have immense utility in vaccination and immunotherapy. A thorough understanding of the merits associated with nanomaterials is crucial for designing of modular and versatile nanovaccines, for improved immune response. With the emerging prerequisites of vaccination, nanomaterial-based immune stimulation, seems to be capable of taking the field of immunization to a next higher level.

Novel therapeutic approaches for pulmonary arterial hypertension: Unique molecular targets to site-specific drug delivery

Pulmonary arterial hypertension (PAH) is a cardiopulmonary disorder characterized by increased blood pressure in the small arterioles supplying blood to lungs for oxygenation. Advances in understanding of molecular and cellular biology techniques have led to the findings that PAH is indeed a cascade of diseases exploiting multi-faceted complex pathophysiology, with cellular proliferation and vascular remodeling being the key pathogenic events along with several cellular pathways involved. While current therapies for PAH do provide for amelioration of disease symptoms and acute survival benefits, their full therapeutic potential is hindered by patient incompliance and off-target side effects. To overcome the issues related with current therapy and to devise a more selective therapy, various novel pathways are being investigated for PAH treatment. In addition, inability to deliver anti-PAH drugs to the disease site i.e., distal pulmonary arterioles has been one of the major challenges in achieving improved patient outcomes and improved therapeutic efficacy. Several novel carriers have been explored to increase the selectivity of currently approved anti-PAH drugs and to act as suitable carriers for the delivery of investigational drugs. In the present review, we have discussed potential of various novel molecular pathways/targets including RhoA/Rho kinase, tyrosine kinase, endothelial progenitor cells, vasoactive intestinal peptide, and miRNA in PAH therapeutics. We have also discussed various techniques for site-specific drug delivery of anti-PAH therapeutics so as to improve the efficacy of approved and investigational drugs. This review will provide gainful insights into current advances in PAH therapeutics with an emphasis on site-specific drug payload delivery.

Intranasal and oral vaccination with protein-based antigens: advantages, challenges and formulation strategies

Most pathogens initiate their infections at the human mucosal surface. Therefore, mucosal vaccination, especially through oral or intranasal administration routes, is highly desired for infectious diseases. Meanwhile, protein-based antigens provide a safer alternative to the whole pathogen or DNA based ones in vaccine development. However, the unique biopharmaceutical hurdles that intranasally or orally delivered protein vaccines need to overcome before they reach the sites of targeting, the relatively low immunogenicity, as well as the low stability of the protein antigens, require thoughtful and fine-tuned mucosal vaccine formulations, including the selection of immunostimulants, the identification of the suitable vaccine delivery system, and the determination of the exact composition and manufacturing conditions. This review aims to provide an up-to-date survey of the protein antigen-based vaccine formulation development, including the usage of immunostimulants and the optimization of vaccine delivery systems for intranasal and oral administrations.

Synthesis, characterization, and immune efficacy of layered double hydroxide@SiO2 nanoparticles with shell-core structure as a delivery carrier for Newcastle disease virus DNA vaccine

Layered double hydroxide (LDH)@SiO2 nanoparticles were developed as a delivery carrier for the plasmid DNA expressing the Newcastle disease virus F gene. The LDH was hydrotalcite-like materials. The plasmid DNA encapsulated in the LDH@SiO2 nanoparticles (pFDNA-LDH@SiO2-NPs) was prepared by the coprecipitation method, and the properties of pFDNA-LDH@SiO2-NPs were characterized by transmission electron microscopy, zeta potential analyzer, Fourier transform infrared spectroscopy, and X-ray diffraction analysis. The results demonstrated that the pFDNA-LDH@SiO2-NPs had a regular morphology and high stability with a mean diameter of 371.93 nm, loading capacity of 39.66%±0.45%, and a zeta potential of +31.63 mV. A release assay in vitro showed that up to 91.36% of the total plasmid DNA could be sustainably released from the pFDNA-LDH@SiO2-NPs within 288 hours. The LDH@SiO2 nanoparticles had very low toxicity. Additionally, their high transfection efficiency in vitro was detected by fluorescent microscopy. Intranasal immunization of specific pathogen-free chickens with pFDNA-LDH@SiO2-NPs induced stronger cellular, humoral, and mucosal immune responses and achieved a greater sustained release effect than intramuscular naked plasmid DNA, and the protective efficacy after challenge with the strain F48E9 with highly virulent (mean death time of chicken embryos ≤60 hours, intracerebral pathogenicity index in 1 -day-old chickens >1.6) was 100%. Based on the results, LDH@SiO2 nanoparticles can be used as a delivery carrier for mucosal immunity of Newcastle disease DNA vaccine, and have great application potential in the future.