Pulmonary vaccine delivery

Combinatorial development of nebulized mRNA delivery formulations for the lungs

Inhaled delivery of mRNA has the potential to treat a wide variety of diseases. However, nebulized mRNA lipid nanoparticles (LNPs) face several unique challenges including stability during nebulization and penetration through both cellular and extracellular barriers. Here we develop a combinatorial approach addressing these barriers. First, we observe that LNP formulations can be stabilized to resist nebulization-induced aggregation by altering the nebulization buffer to increase the LNP charge during nebulization, and by the addition of a branched polymeric excipient. Next, we synthesize a combinatorial library of ionizable, degradable lipids using reductive amination, and evaluate their delivery potential using fully differentiated air-liquid interface cultured primary lung epithelial cells. The final combination of ionizable lipid, charge-stabilized formulation and stability-enhancing excipient yields a significant improvement in lung mRNA delivery over current state-of-the-art LNPs and polymeric nanoparticles.

Recent advances in respiratory immunization: A focus on COVID-19 vaccines

The development of vaccines has always been an essential task worldwide since vaccines are regarded as powerful weapons in protecting the global population. Although the vast majority of currently authorized human vaccinations are administered intramuscularly or subcutaneously, exploring novel routes of immunization has been a prominent area of study in recent years. This is particularly relevant in the face of pandemic diseases, such as COVID-19, where respiratory immunization offers distinct advantages, such as inducing systemic and mucosal responses to prevent viral infections in both the upper and lower respiratory tracts and also leading to higher patient compliance. However, the development of respiratory vaccines confronts challenges due to the physiological barriers of the respiratory tract, with most of these vaccines still in the research and development stage. In this review, we detail the structure of the respiratory tract and the mechanisms of mucosal immunity, as well as the obstacles to respiratory vaccination. We also examine the considerations necessary in constructing a COVID-19 respiratory vaccine, including the dosage form of the vaccines, potential excipients and mucosal adjuvants, and delivery systems and devices for respiratory vaccines. Finally, we present a comprehensive overview of the COVID-19 respiratory vaccines currently under clinical investigation. We hope this review can provide valuable insights and inspiration for the future development of respiratory vaccinations.

Immunization with matrix-, nucleoprotein and neuraminidase protects against H3N2 influenza challenge in pH1N1 pre-exposed pigs

There is an urgent need for influenza vaccines providing broader protection that may decrease the need for annual immunization of the human population. We investigated the efficacy of heterologous prime boost immunization with chimpanzee adenovirus (ChAdOx2) and modified vaccinia Ankara (MVA) vectored vaccines, expressing conserved influenza virus nucleoprotein (NP), matrix protein 1 (M1) and neuraminidase (NA) in H1N1pdm09 pre-exposed pigs. We compared the efficacy of intra-nasal, aerosol and intra-muscular vaccine delivery against H3N2 influenza challenge. Aerosol prime boost immunization induced strong local lung T cell and antibody responses and abrogated viral shedding and lung pathology following H3N2 challenge. In contrast, intramuscular immunization induced powerful systemic responses and weak local lung responses but also abolished lung pathology and reduced viral shedding. These results provide valuable insights into the development of a broadly protective influenza vaccine in a highly relevant large animal model and will inform future vaccine and clinical trial design.

Aluminum-based metal-organic framework nanoparticles as pulmonary vaccine adjuvants

The adoption of pulmonary vaccines to advantageously provide superior local mucosal protection against aerosolized pathogens has been faced with numerous logistical and practical challenges. One of these persistent challenges is the lack of effective vaccine adjuvants that could be well tolerated through the inhaled route of administration. Despite its widespread use as a vaccine adjuvant, aluminum salts (alum) are not well tolerated in the lung. To address this issue, we evaluated the use of porous aluminum (Al)-based metal-organic framework (MOF) nanoparticles (NPs) as inhalable adjuvants. We evaluate a suite of Al-based MOF NPs alongside alum including DUT-4, DUT-5, MIL-53 (Al), and MIL-101-NH₂ (Al). As synthesized, MOF NPs ranged between ~ 200 nm and 1 µm in diameter, with the larger diameter MOFs matching those of commercial alum. In vitro examination of co-stimulatory markers revealed that the Al-based MOF NPs activated antigen presenting cells more effectively than alum. Similar results were found during in vivo immunizations utilizing ovalbumin (OVA) as a model antigen, resulting in robust mucosal humoral responses for all Al MOFs tested. In particular, DUT-5 was able to elicit mucosal OVA-specific IgA antibodies that were significantly higher than the other MOFs or alum dosed at the same NP mass. DUT-5 also was uniquely able to generate detectable IgG2a titers, indicative of a cellular immune response and also had superior performance relative to alum at equivalent Al dosed in a reduced dosage vaccination study. All MOF NPs tested were generally well-tolerated in the lung, with only acute levels of cellular infiltrates detected and no Al accumulation; Al content was largely cleared from the lung and other organs at 28 days despite the two-dose regime. Furthermore, all MOF NPs exhibited mass median aerodynamic diameters (MMADs) of ~ 1.5-2.5 µm when dispersed from a generic dry powder inhaler, ideal for efficient lung deposition. While further work is needed, these results demonstrate the great potential for use of Al-based MOFs for pulmonary vaccination as novel inhalable adjuvants.

Aerosolizable Plasmid DNA Dry Powders Engineered by Thin-film Freezing

PURPOSE

This study was designed to test the feasibility of using thin-film freezing (TFF) to prepare aerosolizable dry powders of plasmid DNA (pDNA) for pulmonary delivery.

METHODS

Dry powders of pDNA formulated with mannitol/leucine (70/30, w/w) with various drug loadings, solid contents, and solvents were prepared using TFF, their aerosol properties (i.e., mass median aerodynamic diameter (MMAD) and fine particle fraction (FPF)) were determined, and selected powders were used for further characterization.

RESULTS

Of the nine dry powders prepared, their MMAD values were about 1-2 µm, with FPF values (delivered) of 40-80%. The aerosol properties of the powders were inversely correlated with the pDNA loading and the solid content in the pDNA solution before TFF. Powders prepared with Tris-EDTA buffer or cosolvents (i.e., 1,4-dioxane or tert-butanol in water), instead of water, showed slightly reduced aerosol properties. Ultimately, powders prepared with pDNA loading at 5% (w/w), 0.25% of solid content, with or without Tris-EDTA were selected for further characterization due to their overall good aerosol performance. The pDNA powders exhibited a porous matrix structure, with a moisture content of < 2% (w/w). Agarose gel electrophoresis confirmed the chemical integrity of the pDNA after it was subjected to TFF and after the TFF powder was actuated. A cell transfection study confirmed that the activity of the pDNA did not change after it was subjected to TFF.

CONCLUSION

It is feasible to use TFF to produce aerosolizable pDNA dry powder for pulmonary delivery, while preserving the integrity and activity of the pDNA.

Nebulization of Model Hydrogel Nanoparticles to Macrophages at the Air-Liquid Interface

Nanoparticle evaluation within the pulmonary airspace has increasingly important implications for human health, with growing interest from drug delivery, environmental, and toxicology fields. While there have been widespread investigations of nanoparticle physiochemical properties following many routes of administration, nanoparticle behavior at the air-liquid interface (ALI) is less well-characterized. In this work, we fabricate two formulations of poly(ethylene)-glycol diacrylate (PEGDA)-based model nanoparticles to establish an in vitro workflow allowing evaluation of nanoparticle charge effects at the ALI. Both cationic and anionic PEGDA formulations were synthesized with similar hydrodynamic diameters around ~225 nm and low polydispersity, with expected surface charges corresponding with the respective functional co-monomer. We find that both formulations are readily nebulized from an aqueous suspension in a commercial Aeroneb® Lab Nebulizer, but the aqueous delivery solution served to slightly increase the overall hydrodynamic and geometric size of the cationic particle formulation. However, nanoparticle loading at 50 μg/ml of either formulation did not influence the resultant aerosol diameter from the nebulizer. To assess aerosol delivery in vitro, we designed a 3D printed adapter capable of ensuring aerosol delivery to transwell 24-well culture plates. Nanoparticle uptake by macrophages was compared between traditional cell culture techniques and that of ALI-cultured macrophages following aerosol delivery. Cell viability was unaffected by nanoparticle delivery using either method. However, only traditional cell culture methods demonstrated significant uptake that was dependent on the nanoparticle surface charge. Concurrently, ALI culture resulted in lower metabolic activity of macrophages than those in traditional cell culture, leading to lower overall nanoparticle uptake at ALI. Overall, this work demonstrates that base-material similarities between both particle formulations provide an expected consistency in aerosol delivery regardless of the nanoparticle surface charge and provides an important workflow that enables a holistic evaluation of aerosolizable nanoparticles.

Mechanisms and challenges of nanocarriers as non-viral vectors of therapeutic genes for enhanced pulmonary delivery

With the rapid development of biopharmaceuticals and the outbreak of COVID-19, the world has ushered in a frenzy to develop gene therapy. Therefore, therapeutic genes have received enormous attention. However, due to the extreme instability and low intracellular gene expression of naked genes, specific vectors are required. Viral vectors are widely used attributed to their high transfection efficiency. However, due to the safety concerns of viral vectors, nanotechnology-based non-viral vectors have attracted extensive investigation. Still, issues of low transfection efficiency and poor tissue targeting of non-viral vectors need to be addressed. Especially, pulmonary gene delivery has obvious advantages for the treatment of inherited lung diseases, lung cancer, and viral pneumonia, which can not only enhance lung targeting and but also reduce enzymatic degradation. For systemic diseases therapy, pulmonary gene delivery can enhance vaccine efficacy via inducing not only cellular, humoral immunity but also mucosal immunity. This review provides a comprehensive overview of nanocarriers as non-viral vectors of therapeutic genes for enhanced pulmonary delivery. First of all, the characteristics and therapeutic mechanism of DNA, mRNA, and siRNA are provided. Thereafter, the advantages and challenges of pulmonary gene delivery in exerting local and systemic effects are discussed. Then, the inhalation dosage forms for nanoparticle-based drug delivery systems are introduced. Moreover, a series of materials used as nanocarriers for pulmonary gene delivery are presented, and the endosomal escape mechanisms of nanocarriers based on different materials are explored. The application of various non-viral vectors for pulmonary gene delivery are summarized in detail, with the perspectives of nano-vectors for pulmonary gene delivery.

Polymeric Nanoparticles for Inhaled Vaccines

Many recent studies focus on the pulmonary delivery of vaccines as it is needle-free, safe, and effective. Inhaled vaccines enhance systemic and mucosal immunization but still faces many limitations that can be resolved using polymeric nanoparticles (PNPs). This review focuses on the use of properties of PNPs, specifically chitosan and PLGA to be used in the delivery of vaccines by inhalation. It also aims to highlight that PNPs have adjuvant properties by themselves that induce cellular and humeral immunogenicity. Further, different factors influence the behavior of PNP in vivo such as size, morphology, and charge are discussed. Finally, some of the primary challenges facing PNPs are reviewed including formulation instability, reproducibility, device-related factors, patient-related factors, and industrial-level scale-up. Herein, the most important variables of PNPs that shall be defined in any PNPs to be used for pulmonary delivery are defined. Further, this study focuses on the most popular polymers used for this purpose.

Development of (Inhalable) Dry Powder Formulations of AS01B-Containing Vaccines Using Thin-Film Freeze-Drying

AS01_B is a liposomal formulation of two immunostimulants namely 3-O-desacyl-4́-monophosphoryl lipid A (MPL) and QS-21. The liposomal formulation of AS01_B reduces the endotoxicity of MPL and the lytic activity of QS-21. The AS01_B-adjuvanted Shingrix vaccine is marketed in a two-vial presentation, with the liquid AS01_B liposomes in one vial and the antigen as a dry powder in another vial. In the present study, we tested the feasibility of applying thin-film freeze-drying (TFFD) to engineer dry powders of the AS01_B liposomal adjuvant alone or vaccines containing AS01_B as an adjuvant. Initially, we showed that after the AS01_B liposomal adjuvant was subjected to TFFD using sucrose as a stabilizer at 4% w/v, the particle size distribution of AS01_B liposomes reconstituted from the dry powder was identical to the liquid adjuvant before drying. We then showed using ovalbumin (OVA) as a model antigen adjuvanted with AS01_B (AS01_B/OVA) that subjecting the AS01_B/OVA vaccine to TFFD and subsequent reconstitution did not negatively affect the AS01_B liposome particle size, nor the immunogenicity of the vaccine. Importantly, the thin-film freeze-dried AS01_B/OVA vaccine, unlike its liquid counterpart, was not sensitive to repeated freezing-and-thawing. The developed AS01_B/OVA dry powder also showed the desirable aerosol properties (i.e., fine particle fraction of 66.3 ± 4.9% and mass median aerodynamic diameter of 2.4 ± 0.1 µm) for potential pulmonary administration. Finally, the feasibility of using TFFD to prepare dry powders of AS01_B-adjuvanted vaccines was further confirmed using AS01_B-adjuvanted Fluzone Quadrivalent and Shingrix, which contains AS01_B. It is concluded that the TFFD technology can enable the formulation of AS01_B-adjuvanted vaccines as freezing-insensitive, inhalable dry powders in a single-vial presentation.

Oral organic nanovaccines against bacterial and viral diseases

Vaccines have saved millions of humans and animals from deadly diseases. Many vaccines are still under development to fight against lethal diseases. Indeed, subunit vaccines are a versatile approach with several advantageous attributes, but they lack strong immunogenicity. Nanotechnology is an avenue to vaccine development because nanoparticles may serve as nanocarriers and adjuvants, which are critical aspects for oral vaccines. This review provides an update of oral organic nanovaccines, describing suitable nanomaterials for oral vaccine design and recent (last five-year view) oral nanovaccine developments to fight against those principal pathogens causing human and animal diseases.

Nasal Nanovaccines for SARS-CoV-2 to Address COVID-19

COVID-19 is still prevalent around the globe. Although some SARS-CoV-2 vaccines have been distributed to the population, the shortcomings of vaccines and the continuous emergence of SARS-CoV-2 mutant virus strains are a cause for concern. Thus, it is vital to continue to improve vaccines and vaccine delivery methods. One option is nasal vaccination, which is more convenient than injections and does not require a syringe. Additionally, stronger mucosal immunity is produced under nasal vaccination. The easy accessibility of the intranasal route is more advantageous than injection in the context of the COVID-19 pandemic. Nanoparticles have been proven to be suitable delivery vehicles and adjuvants, and different NPs have different advantages. The shortcomings of the SARS-CoV-2 vaccine may be compensated by selecting or modifying different nanoparticles. It travels along the digestive tract to the intestine, where it is presented by GALT, tissue-resident immune cells, and gastrointestinal lymph nodes. Nasal nanovaccines are easy to use, safe, multifunctional, and can be distributed quickly, demonstrating strong prospects as a vaccination method for SARS-CoV-2, SARS-CoV-2 variants, or SARS-CoV-n.

Nanomedicine as a promising strategy for the theranostics of infectious diseases

Infectious diseases caused by bacteria, viruses, and fungi and their global spread pose a great threat to human health. The 2019 World Health Organization report predicted that infection-related mortality will be similar to cancer mortality by 2050. Particularly, the global cumulative numbers of the recent outbreak of coronavirus disease (COVID-19) have reached 110.7 million cases and over 2.4 million deaths as of February 23, 2021. Moreover, the crisis of these infectious diseases exposes the many problems of traditional diagnosis, treatment, and prevention, such as time-consuming and unselective detection methods, the emergence of drug-resistant bacteria, serious side effects, and poor drug delivery. There is an urgent need for rapid and sensitive diagnosis as well as high efficacy and low toxicity treatments. The emergence of nanomedicine has provided a promising strategy to greatly enhance detection methods and drug treatment efficacy. Owing to their unique optical, magnetic, and electrical properties, nanoparticles (NPs) have great potential for the fast and selective detection of bacteria, viruses, and fungi. NPs exhibit remarkable antibacterial activity by releasing reactive oxygen species and metal ions, exerting photothermal effects, and causing destruction of the cell membrane. Nano-based delivery systems can further improve drug permeability, reduce the side effects of drugs, and prolong systemic circulation time and drug half-life. Moreover, effective drugs against COVID-19 are still lacking. Recently, nanomedicine has shown great potential to accelerate the development of safe and novel anti-COVID-19 drugs. This article reviews the fundamental mechanisms and the latest developments in the treatment and diagnosis of bacteria, viruses, and fungi and discusses the challenges and perspectives in the application of nanomedicine.

The rough inhalable ciprofloxacin hydrochloride microparticles based on silk fibroin for non-cystic fibrosis bronchiectasis therapy with good biocompatibility

Non-cystic fibrosis bronchiectasis (NCFB) is a chronic respiratory disease, and the thick and viscous mucus covering on respiratory epithelia can entrap the inhaled drugs, resulting in compromised therapeutic efficiency. In order to solve this problem, the inhalable ciprofloxacin hydrochloride microparticles (CMs) based on silk fibroin (SF) and mannitol (MAN) were designed and developed. SF was applied to increase the loading efficiency of ciprofloxacin hydrochloride by strong electrostatic interactions. MAN could facilitate the penetration of drugs through mucus, which ensured the drugs could reach their targets before clearance. Furthermore, the aerodynamic performance of the inhalable microparticles could be tuned by changing the surface roughness to achieve a high fine particle fraction value (45.04%). The antibacterial effects of CMs were also confirmed by measuring the minimum inhibitory concentration against four different bacteria strains. Moreover, a series of experiments both in vitro and in vivo showed that CMs would not affect the lung function and induce the secretion of inflammatory cytokines in lungs, demonstrating their excellent biocompatibility and biosafety. Therefore, CMs might be a promising pulmonary drug delivery system for the treatment of NCFB.

Inhaled antibodies: Quality and performance considerations

The use of antibodies in the treatment of lung diseases is of increasing interest especially as the search for COVID-19 therapies has unfolded. Historically, the use of antibody therapy was based on multiple targets including receptors involved in local hyper-reactivity in asthma, viruses and micro-organisms involved in a variety of pulmonary infectious disease. Generally, protein therapeutics pose challenges with respect to formulation and delivery to retain activity and assure therapy. The specificity of antibodies amplifies the need for attention to molecular integrity not only in formulation but also during aerosol delivery for pulmonary administration. Drug product development can be viewed from considerations of route of administration, dosage form, quality, and performance measures. Nebulizers and dry powder inhalers have been used to deliver protein therapeutics and each has its advantages that should be matched to the needs of the drug and the disease. This review offers insight into quality and performance barriers and the opportunities that arise from meeting them effectively.

Stability and In Vitro Aerodynamic Studies of Inhalation Powders Containing Ciprofloxacin Hydrochloride Applying Different DPI Capsule Types

In the case of capsule-based dry powder inhalation systems (DPIs), the selection of the appropriate capsule is important. The use of gelatin, gelatin-PEG, and HPMC capsules has become widespread in marketed capsule-based DPIs. We aimed to perform a stability test according to the ICH guideline in the above-mentioned three capsule types. The results of the novel combined formulated microcomposite were more favorable than those of the carrier-free formulation for all capsule types. The use of HPMC capsules results in the greatest stability and thus the best in vitro aerodynamic results for both DPI powders after six months. This can be explained by the fact that the residual solvent content (RSC) of the capsules differs. Under the applied conditions the RSC of the HPMC capsule decreased the least and remained within the optimal range, thus becoming less fragmented, which was reflected in the RSC, structure and morphology of the particles, as well as in the in vitro aerodynamic results (there was a difference of approximately 10% in the lung deposition results). During pharmaceutical dosage form developments, emphasis should be placed in the case of DPIs on determining which capsule type will be used for specific formulations.

Synthetic protein conjugate vaccines provide protection against Mycobacterium tuberculosis in mice

The global incidence of tuberculosis remains unacceptably high, with new preventative strategies needed to reduce the burden of disease. We describe here a method for the generation of synthetic self-adjuvanted protein vaccines and demonstrate application in vaccination against Mycobacterium tuberculosis Two vaccine constructs were designed, consisting of full-length ESAT6 protein fused to the TLR2-targeting adjuvants Pam₂Cys-SK₄ or Pam₃Cys-SK₄ These were produced by chemical synthesis using a peptide ligation strategy. The synthetic self-adjuvanting vaccines generated powerful local CD4⁺ T cell responses against ESAT6 and provided significant protection in the lungs from virulent M. tuberculosis aerosol challenge when administered to the pulmonary mucosa of mice. The flexible synthetic platform we describe, which allows incorporation of adjuvants to multiantigenic vaccines, represents a general approach that can be applied to rapidly assess vaccination strategies in preclinical models for a range of diseases, including against novel pandemic pathogens such as SARS-CoV-2.

Applications of Nanovaccines for Disease Prevention in Cattle

Vaccines are one of the most important tools available to prevent and reduce the incidence of infectious diseases in cattle. Despite their availability and widespread use to combat many important pathogens impacting cattle, several of these products demonstrate variable efficacy and safety in the field, require multiple doses, or are unstable under field conditions. Recently, nanoparticle-based vaccine platforms (nanovaccines) have emerged as promising alternatives to more traditional vaccine platforms. In particular, polymer-based nanovaccines provide sustained release of antigen payloads, stabilize such payloads, and induce enhanced antibod- and cell-mediated immune responses, both systemically and locally. To improve vaccine administrative strategies and efficacy, they can be formulated to contain multiple antigenic payloads and have the ability to protect fragile proteins from degradation. Nanovaccines are also stable at room temperature, minimizing the need for cold chain storage. Nanoparticle platforms can be synthesized for targeted delivery through intranasal, aerosol, or oral administration to induce desired mucosal immunity. In recent years, several nanovaccine platforms have emerged, based on biodegradable and biocompatible polymers, liposomes, and virus-like particles. While most nanovaccine candidates have not yet advanced beyond testing in rodent models, a growing number have shown promise for use against cattle infectious diseases. This review will highlight recent advancements in polymeric nanovaccine development and the mechanisms by which nanovaccines may interact with the bovine immune system. We will also discuss the positive implications of nanovaccines use for combating several important viral and bacterial disease syndromes and consider important future directions for nanovaccine development in beef and dairy cattle.

COVID-19 and cancer: From basic mechanisms to vaccine development using nanotechnology

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Shows updated understanding of SARS-CoV-2, including the interaction between ACE 2 and the viral spike protein.

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More effective vaccines are required for immunocompromised cancer patients.

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Cancer alters the immune system through different levels of D-Dimer, albumin, prothrombin, and neutrophils.

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Nanomaterials assist vaccine delivery, including viral vector and mRNA vaccines with lipid nanoparticles.

Coronavirus disease 2019 (COVID-19), caused by severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), is a global pandemic which has induced unprecedented ramifications, severely affecting our society due to the long incubation time, unpredictably high prevalence and lack of effective vaccines. One of the interesting notions is that there is an association between COVID-19 and cancer. Cancer patients seem to exhibit exacerbated conditions and a higher mortality rate when exposed to the virus. Therefore, vaccines are the promising solution to minimise the problem amongst cancer patients threatened by the new viral strains. However, there are still limitations to be considered, including the efficacy of COVID vaccines for immunocompromised individuals, possible interactions between the vaccine and cancer, and personalised medicine. Not only to eradicate the pandemic, but also to make it more effective for immunocompromised patients who are suffering from cancer, a successful vaccine platform is required through the implementation of nanotechnology which can also enable scalable manufacturing and worldwide distribution along with its faster and precise delivery. In this review, we summarise the current understanding of COVID-19 with clinical perspectives, highlighting the association between COVID-19 and cancer, followed by a vaccine development for this association using nanotechnology. We suggest different administration methods for the COVID-19 vaccine formulation options. This study will contribute to paving the way towards the prevention and treatment of COVID-19, especially for the immunocompromised individuals.

A homogenous nanoporous pulmonary drug delivery system based on metal-organic frameworks with fine aerosolization performance and good compatibility

Pulmonary drug delivery has attracted increasing attention in biomedicine, and porous particles can effectively enhance the aerosolization performance and bioavailability of drugs. However, the existing methods for preparing porous particles using porogens have several drawbacks, such as the inhomogeneous and uncontrollable pores, drug leakage, and high risk of fragmentation. In this study, a series of cyclodextrin-based metal-organic framework (CD-MOF) particles containing homogenous nanopores were delicately engineered without porogens. Compared with commercial inhalation carrier, CD-MOF showed excellent aerosolization performance because of the homogenous nanoporous structure. The great biocompatibility of CD-MOF in pulmonary delivery was also confirmed by a series of experiments, including cytotoxicity assay, hemolysis ratio test, lung function evaluation, in vivo lung injury markers measurement, and histological analysis. The results of ex vivo fluorescence imaging showed the high deposition rate of CD-MOF in lungs. Therefore, all results demonstrated that CD-MOF was a promising carrier for pulmonary drug delivery. This study may throw light on the nanoporous particles for effective pulmonary administration.

Cyclodextrin-based metal-organic frameworks for pulmonary delivery of curcumin with improved solubility and fine aerodynamic performance

Pulmonary drug delivery has attracted considerable attention in recent years. However, it is still a major challenge to deliver poorly water-soluble drugs to lungs with good solubility and fine aerodynamic performance. In this study, curcumin was loaded into cyclodextrin-based metal-organic frameworks (CD-MOFs) for pulmonary delivery. Compared with micronized curcumin prepared by jet milling, curcumin-loaded CD-MOFs (Cur-CD-MOFs) exhibited excellent aerodynamic performance, which was attributed to the unique porous structure and lower density of CD-MOFs. The dissolution test showed that the drug release rate of Cur-CD-MOFs was much faster than that of micronized curcumin. The all-atom molecular dynamic simulation showed that curcumin molecules were loaded into the hydrophobic cavities of CD-MOFs or entered into the large hydrophilic cavities to form nanoclusters. The elevated wettability of Cur-CD-MOFs and the unique spatial distribution feature of curcumin in porous interior of CD-MOFs might be favorable for the improved dissolution rate. The DPPH radical scavenging test showed that Cur-CD-MOFs had prominent antioxidant activities. Therefore, CD-MOFs were expected to be promising carriers for pulmonary delivery of poorly water-soluble drugs.

COVID-19: Current Developments and Further Opportunities in Drug Delivery and Therapeutics

SARS-CoV-2 has affected people from all age groups, races and ethnicities. Given that many infected individuals are asymptomatic, they transmit the disease to others unknowingly, which has resulted in the spread of infection at an alarming rate. This review aims to provide an overview of the pathophysiology, preventive measures to reduce the disease spread, therapies currently in use, an update on vaccine development and opportunities for vaccine delivery. The World Health Organization has advised several precautions including social distancing, hand washing and the use of PPE including gloves and face masks for minimizing the spread of SARS-CoV-2 infection. At present, several antiviral therapies previously approved for other infections are being repositioned to study their efficacy against SARS-CoV-2. In addition, some medicines (i.e., remdesivir, chloroquine, hydroxychloroquine) have received emergency use authorisation from the FDA. Plasma therapy has also been authorised for emergency use for the treatment of COVID-19 on a smaller scale. However, no vaccine has been approved so far against this virus. Nevertheless, several potential vaccine targets have been reported, and development of different types of vaccines including DNA, mRNA, viral vector, inactivated, subunit and vaccine-like particles is in process. It is concluded that a suitable candidate delivered through an advanced drug delivery approach would effectively boost the immune system against this coronavirus.

Significant Unresolved Questions and Opportunities for Bioengineering in Understanding and Treating COVID-19 Disease Progression

COVID-19 is a disease that manifests itself in a multitude of ways across a wide range of tissues. Many factors are involved, and though impressive strides have been made in studying this novel disease in a very short time, there is still a great deal that is unknown about how the virus functions. Clinical data has been crucial for providing information on COVID-19 progression and determining risk factors. However, the mechanisms leading to the multi-tissue pathology are yet to be fully established. Although insights from SARS-CoV-1 and MERS-CoV have been valuable, it is clear that SARS-CoV-2 is different and merits its own extensive studies. In this review, we highlight unresolved questions surrounding this virus including the temporal immune dynamics, infection of non-pulmonary tissue, early life exposure, and the role of circadian rhythms. Risk factors such as sex and exposure to pollutants are also explored followed by a discussion of ways in which bioengineering approaches can be employed to help understand COVID-19. The use of sophisticated in vitro models can be employed to interrogate intercellular interactions and also to tease apart effects of the virus itself from the resulting immune response. Additionally, spatiotemporal information can be gleaned from these models to learn more about the dynamics of the virus and COVID-19 progression. Application of advanced tissue and organ system models into COVID-19 research can result in more nuanced insight into the mechanisms underlying this condition and elucidate strategies to combat its effects.

Severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) infection: let the virus be its own demise

There has been a collaborative global effort to construct novel therapeutic and prophylactic approaches to SARS-CoV-2 management. Although vaccine development is crucial, acute management of newly infected patients, especially those with severe acute respiratory distress syndrome, is a priority. Herein we describe the rationale and potential of repurposing a dual plasmid, Vigil (pbi-shRNA^furin-GM-CSF), now in Phase III cancer trials, for the treatment of and, in certain circumstances, enhancement of the immune response to SARS-CoV-2.

Emerging trends in inhaled drug delivery

Ideally, inhaled therapy is driven by the needs of specific disease management. Lung biology interfaces with inhaler performance to allow optimal delivery of therapeutic agent for disease treatment. Inhalation aerosol products consist of the therapeutic agent, formulation, and device. The manufacturing specifications on each of the components, and their combination, allow accurate and reproducible control of measures of quality and in-vitro performance. These product variables in combination with patient variables, including co-ordination skill during inhaler use, intrinsic lung biology, disease and consequent pulmonary function, contribute to drug safety and efficacy outcomes. Due to the complexity of pulmonary drug delivery, predicting biological outcomes from first principles has been challenging. Ongoing research appears to offer new insights that may allow accurate prediction of drug behavior in the lungs. Disruptive innovations were characteristic of research and development in inhaled drug delivery at the end of the last century. Although there were relatively few new inhaled products launched in the first decade of the new millennium it was evident that the earlier years of exploration resulted in maturation of commercially successful technologies. A significant increase in new and generic products has occurred in the last decade and technical, regulatory and disease management trends are emerging. Some of these developments can trace their origins to earlier periods of creativity in the field while others are a reflection of advances in other areas of basic and computer, sciences and engineering. Select biological and technical advances are highlighted with reflections on the potential to impact future clinical and regulatory considerations.

Therapeutic efficacy of nanoparticles and routes of administration

In modern-day medicine, nanotechnology and nanoparticles are some of the indispensable tools in disease monitoring and therapy. The term “nanomaterials” describes materials with nanoscale dimensions (< 100 nm) and are broadly classified into natural and synthetic nanomaterials. However, “engineered” nanomaterials have received significant attention due to their versatility. Although enormous strides have been made in research and development in the field of nanotechnology, it is often confusing for beginners to make an informed choice regarding the nanocarrier system and its potential applications. Hence, in this review, we have endeavored to briefly explain the most commonly used nanomaterials, their core properties and how surface functionalization would facilitate competent delivery of drugs or therapeutic molecules. Similarly, the suitability of carbon-based nanomaterials like CNT and QD has been discussed for targeted drug delivery and siRNA therapy. One of the biggest challenges in the formulation of drug delivery systems is fulfilling targeted/specific drug delivery, controlling drug release and preventing opsonization. Thus, a different mechanism of drug targeting, the role of suitable drug-laden nanocarrier fabrication and methods to augment drug solubility and bioavailability are discussed. Additionally, different routes of nanocarrier administration are discussed to provide greater understanding of the biological and other barriers and their impact on drug transport. The overall aim of this article is to facilitate straightforward perception of nanocarrier design, routes of various nanoparticle administration and the challenges associated with each drug delivery method.

Mucosal Vaccination with a Self-Adjuvanted Lipopeptide Is Immunogenic and Protective against Mycobacterium tuberculosis

Tuberculosis (TB) remains a staggering burden on global public health. Novel preventative tools are desperately needed to reach the targets of the WHO post-2015 End-TB Strategy. Peptide or protein-based subunit vaccines offer potential as safe and effective generators of protection, and enhancement of local pulmonary immunity may be achieved by mucosal delivery. We describe the synthesis of a novel subunit vaccine via native chemical ligation. Two immunogenic epitopes, ESAT6_1-20 and TB10.4_3-11 from Mycobacterium tuberculosis (Mtb), were covalently conjugated to the TLR2-ligand Pam₂Cys to generate a self-adjuvanting lipopeptide vaccine. When administered mucosally to mice, the vaccine enhanced pulmonary immunogenicity, inducing strong Th17 responses in the lungs and multifunctional peripheral T-lymphocytes. Mucosal, but not peripheral vaccination, provided substantial protection against Mtb infection, emphasizing the importance of delivery route for optimal efficacy.

Mucosal Vaccination via the Respiratory Tract

Vaccine delivery via mucosal surfaces is an interesting alternative to parenteral vaccine administration, as it avoids the use of a needle and syringe. Mucosal vaccine administration also targets the mucosal immune system, which is the largest lymphoid tissue in the human body. The mucosal immune response involves systemic, antigen-specific humoral and cellular immune response in addition to a local response which is characterised by a predominantly cytotoxic T cell response in combination with secreted IgA. This antibody facilitates pathogen recognition and deletion prior to entrance into the body. Hence, administration via the respiratory mucosa can be favoured for all pathogens which use the respiratory tract as entry to the body, such as influenza and for all diseases directly affecting the respiratory tract such as pneumonia. Additionally, the different mucosal tissues of the human body are interconnected via the so-called “common mucosal immune system”, which allows induction of an antigen-specific immune response in distant mucosal sites. Finally, mucosal administration is also interesting in the area of therapeutic vaccination, in which a predominant cellular immune response is required, as this can efficiently be induced by this route of delivery. The review gives an introduction to respiratory vaccination, formulation approaches and application strategies.

Dry Formulations Enhanced Mucoadhesive Properties and Reduced Cold Chain Handing of Influenza Vaccines

To alleviate concerns in health security, emergency flu vaccine stockpiles are required for ensuring rapid availability of vaccines when needed. Cold chain preservation, at high cost and risk, is necessary to maintain vaccine efficacy. This study aimed to develop a dry, easily storable formula for influenza vaccine preparation. The formulation with mucoadhesive properties is expected to facilitate rapid delivery via nasal administration. Chitosan, a cationic polymer, was used as cryo-protectant and to promote mucoadhesion. Optimal concentrations and molecular weights of chitosan polymers were screened, with short chain chitosan (10 kDa) being most suitable. H1N1 dry powder, in different formulations, was prepared via freeze-drying. A series of cryo-protectants, trehalose (T), chitosan (C), fetal bovine serum (FBS; F), or a combination of these (TCF), were screened for their effects on prolonging vaccine shelf life. Physicochemical monitoring (particle size and zeta potential) of powders complexed with mucin revealed that the order of cryo-protectant mixing during preparation was of critical importance. Results indicated that the TCF formula retains its activity up to 1 year as indicated by TCID₅₀ analysis. This approach was also successful at prolonging the shelf life of H3N2 vaccine, and has the potential for large-scale implementation, especially in developed countries where long-term storage of vaccines is problematic.

Developments in the formulation and delivery of spray dried vaccines

Spray drying is a promising method for the stabilization of vaccines, which are usually formulated as liquids. Usually, vaccine stability is improved by spray drying in the presence of a range of excipients. Unlike freeze drying, there is no freezing step involved, thus the damage related to this step is avoided. The edge of spray drying resides in its ability for particles to be engineered to desired requirements, which can be used in various vaccine delivery methods and routes. Although several spray dried vaccines have shown encouraging preclinical results, the number of vaccines that have been tested in clinical trials is limited, indicating a relatively new area of vaccine stabilization and delivery. This article reviews the current status of spray dried vaccine formulations and delivery methods. In particular it discusses the impact of process stresses on vaccine integrity, the application of excipients in spray drying of vaccines, process and formulation optimization strategies based on Design of Experiment approaches as well as opportunities for future application of spray dried vaccine powders for vaccine delivery.

PLGA particulate subunit tuberculosis vaccines promote humoral and Th17 responses but do not enhance control of Mycobacterium tuberculosis infection

Tuberculosis places a staggering burden on human health globally. The new World Health Organisation End-TB Strategy has highlighted the urgent need for more effective TB vaccines to improve control of the disease. Protein-based subunit vaccines offer potential as safe and effective generators of protective immunity, and the use of particulate vaccine formulation and delivery by the pulmonary route may enhance local immunogenicity. In this study, novel particulate subunit vaccines were developed utilising biodegradable poly(lactic-co-glycolic acid) (PLGA) slow-release particles as carriers for the Mycobacterium tuberculosis lipoprotein MPT83, together with the adjuvants trehalose-dibehenate (TDB) or Monophosphoryl lipid A (MPL). Following delivery by the pulmonary or subcutaneous routes, the immunogenicity and protective efficacy of these vaccines were assessed in a murine model of M. tuberculosis infection. When delivered peripherally, these vaccines induced modest, antigen-specific Th1 and Th17 responses, but strong anti-MPT83 antibody responses. Mucosal delivery of the PLGA(MPT83) vaccine, with or without TDB, increased antigen-specific Th17 responses in the lungs, however, PLGA-encapsulated vaccines did not provide protection against M. tuberculosis challenge. By contrast, peripheral delivery of DDA liposomes containing MPT83 and TDB or MPL, stimulated both Th1 and Th17 responses and generated protection against M. tuberculosis challenge. Therefore, PLGA-formulated vaccines primarily stimulate strong humoral immunity, or Th17 responses if used mucosally, and may be a suitable carrier for vaccines against extracellular pathogens. This study emphasises the critical nature of the vaccine carrier, adjuvant and route of delivery for optimising vaccine efficacy against TB.

Co-Spray Dried Mannitol/Poly(amidoamine)-Doxorubicin Dry-Powder Inhaler Formulations for Lung Adenocarcinoma: Morphology, In Vitro Evaluation, and Aerodynamic Performance

nhaled chemotherapeutics have emerged as a promising regimen to combat lung cancer as they maximize local drug concentration while significantly reduce systemic exposure. However, the poor lung/systemic safety profiles and lack of clinically efficient formulations restrict the applicability of inhaled chemotherapeutics. This work developed a dry-powder inhaler (DPI) formulation that dispersed a pH-responsive poly(amidoamine) dendrimer-doxorubicin conjugate (G4-12DOX) into mannitol microparticles. The dendrimer conjugate only releases cytotoxic agents in response to intracellular pH drop, leading to reduced systemic and local toxicity. This work investigated the effect of G4-12DOX content on the microparticle size and morphology, redispersibility, in vitro cytotoxicity, and aerosol properties of the formulations. The spray-dried G4-12DOX/mannitol microparticles showed smooth and spherical morphology with 1-4 μm in diameter. As the content of the G4-12DOX conjugate in the microparticles increased, the size, and degree of aggregation of microparticles increased dramatically. The G4-12DOX/mannitol microparticles were readily redispersed in the aqueous environment, reverting to nanoscale dendrimer conjugates to escape alveolar phagocytosis. All DPI formulations demonstrated the similar cytotoxicity as the original conjugate against a lung adenocarcinoma cell line. The emitted dose (ED) and fine particle fraction (FPF) of the DPI formulations decreased as the content of G4-12DOX increased, but EDs and FPFs of all formulations fell within the range of 85-60% and 60-40%, which were higher than those of commercial products (EDs = 40-60%; FPFs = 12-40%). Therefore, the spray-dried dendrimer/mannitol microparticle is an efficient and practical DPI formulation for direct delivery of large dose of chemotherapeutics to lung tumors.

Nonpathologic Infection of Macaques by an Attenuated Mycobacterial Vaccine Is Not Reactivated in the Setting of HIV Co-Infection

Failure to replace Bacille Calmette-Guerin vaccines with efficacious anti-tuberculosis (TB) vaccines have prompted outside-the-box thinking, including pulmonary vaccination to elicit local immunity. Inhalational MtbΔsigH, a stress-response-attenuated strain, protected against lethal TB in macaques. While live mycobacterial vaccines show promising efficacy, HIV co-infection and the resulting immunodeficiency prompts safety concerns about their use. We assessed the persistence and safety of MtbΔsigH, delivered directly to the lungs, in the setting of HIV co-infection. Macaques were aerosol-vaccinated with ΔsigH and subsequently challenged with SIVmac₂₃₉. Bronchoalveolar lavage and tissues were sampled for mycobacterial persistence, pathology, and immune correlates. Only 35% and 3.5% of lung samples were positive for live bacilli and granulomas, respectively. Our results therefore suggest that the nonpathologic infection of macaque lungs by ΔsigH was not reactivated by simian immunodeficiency virus, despite high viral levels and massive ablation of pulmonary CD4⁺ T cells. Protective pulmonary responses were retained, including vaccine-induced bronchus-associated lymphoid tissue and CD8⁺ effector memory T cells. Despite acute simian immunodeficiency virus infection, all animals remained asymptomatic of pulmonary TB. These findings highlight the efficacy of mucosal vaccination via this attenuated strain and will guide its further development to potentially combat TB in HIV-endemic areas. Our results also suggest that a lack of pulmonary pathology is a key correlate of the safety of live mycobacterial vaccines.

TPP-dendrimer nanocarriers for siRNA delivery to the pulmonary epithelium and their dry powder and metered-dose inhaler formulations

The regulation of genes utilizing the RNA interference (RNAi) mechanism via the delivery of synthetic siRNA has great potential in the treatment of a variety of lung diseases. However, the delivery of siRNA to the lungs is challenging due to the poor bioavailability of siRNA when delivered intraveneously, and difficulty in formulating and maintaining the activity of free siRNA when delivered directly to the lungs using inhalation devices. The use of non-viral vectors such as cationic dendrimers can help enhance the stability of siRNA and its delivery to the cell cytosol. Therefore, in this work, we investigate the ability of a triphenylphosphonium (TPP) modified generation 4 poly(amidoamine) (PAMAM) dendrimer (G4NH₂-TPP) to enhance the in vitro transfection efficiency of siRNA in a model of the pulmonary epithelium and their aerosol formulations in pressurized metered dose inhalers (pMDIs) and dry powder inhalers (DPIs). Complexes of siRNA and G4NH₂-TPP were prepared with varying TPP densities and increasing N/P ratios. The complexation efficiency was modulated by the presence of the TPP on the dendrimer surface, allowing for a looser complexation compared to unmodified dendrimer as determined by gel electrophoresis and polyanion competition assay. An increase in TPP density and N/P ratio led to an increase in the in vitro gene knockdown of stably green fluorescent protein (eGFP) expressing lung alveolar epithelial (A549) cells. G4NH₂-12TPP dendriplexes (G4NH₂ PAMAM dendrimers containing 12 TPP molecules on the surface complexed with siRNA) at N/P ratio 30 showed the highest in vitro gene knockdown efficiency. To assess the potential of TPP-dendriplexes for pulmonary use, we also developed micron particle technologies for both pMDIs and DPIs and determined their aerosol characteristics utilizing an Andersen Cascade Impactor (ACI). Mannitol microparticles encapsulating 12TPP-dendriplexes were shown to be effective in producing aerosols suitable for deep lung deposition for both pMDI formulations (fine particle fraction of 50-53%) and DPI formulations (fine particle fraction of 39%) with no impact on the in vitro gene knockdown efficiency of the siRNA. This work demonstrates the potential benefits of utilizing TPP-conjugated dendrimers in the formation of dendriplexes for siRNA delivery to the pulmonary epithelium and their aerosol formulation for local delivery to the lungs using portable inhalers.

Pulmonary administration of small interfering RNA: The route to go?

Ever since the discovery of RNA interference (RNAi), which is a post-transcriptional gene silencing mechanism, researchers have been studying the therapeutic potential of using small interfering RNA (siRNA) to treat diseases that are characterized by excessive gene expression. Excessive gene expression can be particularly harmful if it occurs in a vulnerable organ such as the lungs as they are essential for physiological respiration. Consequently, RNAi could offer an approach to treat such lung diseases. Parenteral administration of siRNA has been shown to be difficult due to degradation by nucleases in the systemic circulation and excretion by the kidneys. To avoid these issues and to achieve local delivery and local effects, pulmonary administration has been proposed as an alternative administration route. Regarding this application, various animal studies have been conducted over the past few years. Therefore, this review presents a critical analysis of publications where pulmonary administration of siRNA in animals has been reported. Such an analysis is necessary to determine the feasibility of this administration route and to define directions for future research. First, we provide background information on lungs, pulmonary administration, and delivery vectors. Thereafter, we present and discuss relevant animal studies. Though nearly all publications reported positive outcomes, several reoccurring challenges were identified. They relate to 1) the necessity, efficacy, and safety of delivery vectors, 2) the biodistribution of siRNA in tissues other than the lungs, 3) the poor correlation between in vitro and in vivo models, and 4) the long-term effects upon (repeated) administration of siRNA. Finally, we present recommendations for future research to define the route to go: towards safer and more effective pulmonary administration of siRNA.

Poly(amidoamine) Dendrimer-Doxorubicin Conjugates: In Vitro Characteristics and Pseudosolution Formulation in Pressurized Metered-Dose Inhalers

Lung cancers are the leading cause of cancer death for both men and women. A series of PEGylated poly(amidoamine) dendrimer-based doxorubicin (DOX) nanocarriers (G3NH2-mPEG-nDOX) were synthesized and their chemistry tailored for the development of novel pseudosolution formulations in propellant-based metered-dose inhalers (pMDIs) with enhanced aerosol characteristics. A pH-labile bond was used to conjugate DOX to dendrimer for controlled intracellular release. We employed a two-step PEGylation strategy to cover a range of DOX loading and PEGylation density. We investigated the impact of pH, PEGylation density, and DOX payload on the release of DOX from the conjugate. We also determined the cellular internalization of the conjugate, the intracellular release kinetics of DOX from the conjugate, and their ability to kill human alveolar carcinoma cells (A549). The acid-labile conjugates sustained the release of DOX in acidic medium, and also intracellularly, as determined by nuclear colocalization studies with confocal microscopy. Meanwhile, DOX was retained in the conjugate at extracellular physiological conditions, indicating their potential to achieve spatial and temporal controlled release profiles. We also observed that the kinetics of cellular entry of the conjugates with DOX increased significantly compared to free DOX. Due to controlled release, the G3NH2-mPEG-nDOX conjugates showed time-dependent cell kill, but their cell kill ability was comparable to free DOX, which suggests their potential in vivo as compared to free DOX. The conjugates were formulated in pMDIs as pseudosolution formulations, with the help of a minimum amount of cosolvent (ethanol; <0.4%; v/v). The physical stability and aerosol characteristics of the conjugates were controlled by the PEGylation density of the carriers: the higher the PEG density, the better the dispersibility and the better the deep lung deposition of the conjugates (fine particle fraction up to ca. 80%).

Nanoparticulate mediated transcutaneous immunization: Myth or reality

Transcutaneous immunization (TCI) is a promising route of vaccine delivery through skin due to many well documented advantages. The main obstacle in TCI is the skin's top dead layer i.e. stratum corneum which is difficult to penetrate. Efficiently delivery of antigen to the immune competent cells of epidermis or dermis in TCI might elicit an effective immune response. In this review, skin immunology with a particular focus on potential of immunological active receptors in influencing adaptive immune responses is highlighted. The challenges with TCI and methods to improve it using different adjuvants, chemical and physical approaches, delivery systems, and combination of above methods to further improve immune response following skin application of antigen are elaborately discussed. Nanoparticulate vaccine delivery systems with reference to their applications in TCI are classified according to their chronological development. Conclusively, clinical translations of above methods are also briefly reviewed.

FROM THE CLINICAL EDITOR

Transcutaneous immunization has been investigated by many as a promising route of vaccination. In this comprehensive review article, the authors described and discussed the existing knowledge and difficulties in this approach. Furthermore, ways of improving transcutaneous delivery were also reviewed.

Optimization and Dose Estimation of Aerosol Delivery to Non-Human Primates

BACKGROUND

In pre-clinical animal studies, the uniformity of dosing across subjects and routes of administration is a crucial requirement. In preparation for a study in which aerosolized live-attenuated measles virus vaccine was administered to cynomolgus monkeys (Macaca fascicularis) by inhalation, we assessed the percentage of a nebulized dose inhaled under varying conditions.

METHODS

Drug delivery varies with breathing parameters. Therefore we determined macaque breathing patterns (tidal volume, breathing frequency, and inspiratory to expiratory (I:E) ratio) across a range of 3.3-6.5 kg body weight, using a pediatric pneumotachometer interfaced either with an endotracheal tube or a facemask. Subsequently, these breathing patterns were reproduced using a breathing simulator attached to a filter to collect the inhaled dose. Albuterol was nebulized using a vibrating mesh nebulizer and the percentage inhaled dose was determined by extraction of drug from the filter and subsequent quantification.

RESULTS

Tidal volumes ranged from 24 to 46 mL, breathing frequencies from 19 to 31 breaths per minute and I:E ratios from 0.7 to 1.6. A small pediatric resuscitation mask was identified as the best fitting interface between animal and pneumotachometer. The average efficiency of inhaled dose delivery was 32.1% (standard deviation 7.5, range 24%-48%), with variation in tidal volumes as the most important determinant.

CONCLUSIONS

Studies in non-human primates aimed at comparing aerosol delivery with other routes of administration should take both the inter-subject variation and relatively low efficiency of delivery to these low body weight mammals into account.

A nonhuman primate toxicology and immunogenicity study evaluating aerosol delivery of AERAS-402/Ad35 vaccine: Evidence for transient t cell responses in peripheral blood and robust sustained responses in the lungs

Bacille Calmette-Guérin (BCG), the only licensed vaccine for the prevention of tuberculosis (TB), provides only limited protection against certain forms of Mycobacterium tuberculosis (Mtb) infection. While infection with Mtb can be treated with antibiotics, the therapy is expensive, toxic, and requires several months for treatment. In addition, the emergence of drug resistant strains limits the impact of antibiotics and underlines the importance of developing a more effective vaccine to control this disease. Given that pulmonary TB is the most common form of the disease, a vaccine capable of inducing lung-resident immunity may be advantageous for combating this infection. New advances in pulmonary delivery make this route of vaccination feasible and affordable. Here, we evaluate the safety and immunogenicity of an aerosolized Ad35-based vaccine, AERAS-402, delivered to the lungs in nonhuman primates as part of a GLP acute and chronic toxicology and safety study. In this study, animals received three high doses (1 x 10(11) vp) of AERAS-402 by inhalation via a nebulizer at 1-week intervals. Aerosol delivery of AERAS-402 resulted in an increase in relative lung weights as well as microscopic findings in the lungs, mediastinal lymph nodes, bronchus-associated lymphatic tissue, and the naso-oropharynx that were consistent with the induction of an immune response during the acute phase. These findings resolved by the chronic phase and were considered to be non-adverse. Furthermore, we observed transient vaccine-specific immune responses in the peripheral blood as well as sustained high-level polyfunctional CD4(+) and CD8(+) T cell responses in the bronchoalveolar lavage fluid of vaccinated nonhuman primates. The data suggest that pulmonary delivery of Ad35-based vaccines can be safe and can induce potent lung-resident immunity.

Aerosolized Ebola vaccine protects primates and elicits lung-resident T cell responses

Direct delivery of aerosolized vaccines to the respiratory mucosa elicits both systemic and mucosal responses. This vaccine strategy has not been tested for Ebola virus (EBOV) or other hemorrhagic fever viruses. Here, we examined the immunogenicity and protective efficacy of an aerosolized human parainfluenza virus type 3-vectored vaccine that expresses the glycoprotein (GP) of EBOV (HPIV3/EboGP) delivered to the respiratory tract. Rhesus macaques were vaccinated with aerosolized HPIV3/EboGP, liquid HPIV3/EboGP, or an unrelated, intramuscular, Venezuelan equine encephalitis replicon vaccine expressing EBOV GP. Serum and mucosal samples from aerosolized HPIV3/EboGP recipients exhibited high EBOV-specific IgG, IgA, and neutralizing antibody titers, which exceeded or equaled titers observed in liquid recipients. The HPIV3/EboGP vaccine induced an EBOV-specific cellular response that was greatest in the lungs and yielded polyfunctional CD8+ T cells, including a subset that expressed CD103 (αE integrin), and CD4+ T helper cells that were predominately type 1. The magnitude of the CD4+ T cell response was greater in aerosol vaccinees. The HPIV3/EboGP vaccine produced a more robust cell-mediated and humoral immune response than the systemic replicon vaccine. Moreover, 1 aerosol HPIV3/EboGP dose conferred 100% protection to macaques exposed to EBOV. Aerosol vaccination represents a useful and feasible vaccination mode that can be implemented with ease in a filovirus disease outbreak situation.

Nasal and pulmonary vaccine delivery using particulate carriers

INTRODUCTION

Many human pathogens cause respiratory illness by colonizing and invading the respiratory mucosal surfaces. Preventing infection at local sites via mucosally active vaccines is a promising and rational approach for vaccine development. However, stimulating mucosal immunity is often challenging. Particulate adjuvants that can specifically target mucosal immune cells offer a promising opportunity to stimulate local immunity at the nasal and/or pulmonary mucosal surfaces.

AREAS COVERED

This review analyzes the common causes of respiratory infections, the challenges in the induction of mucosal and systemic responses and current pulmonary and nasal mucosal vaccination strategies. The ability of various particulate adjuvant formulations, including lipid-based particles, polymers and other particulate systems, to be effectively utilized for mucosal vaccine delivery is discussed.

EXPERT OPINION

Induction of antibody and cell-mediated mucosal immunity that can effectively combat respiratory pathogens remains a challenge. Particulate delivery systems can be developed to target mucosal immune cells and effectively present antigen to evoke a rapid and long-term local immunity in the respiratory mucosa. In particular, particulate delivery systems offer the versatility of being formulated with multiple adjuvants and antigenic cargo, and can be tailored to effectively prime immune responses across the mucosal barrier. The opportunity for rational design of novel subunit particulate vaccines is emerging.