Opportunities and challenges in vaccine delivery

Topical vaccination with super-stable ready to use nanovesicles

Ultradeformable archaeosomes (UDA) are nanovesicles made of total polar archaeolipids (TPA) from the archaea Halorubrum tebenquichense, soybean phosphatidylcholine and sodium cholate (3:3:1w/w). Fresh dispersions of UDA including different type of antigens are acknowledged as efficient topical vaccination agents. UDA dispersions however, if manufactured for pharmaceutical use, have to maintain colloidal stability upon liposomicidal processes such as sterilization and lyophilization (_SLRUDA), needed to extend shelf life during storage. The remaining capacity of _SLRUDA to act as adjuvants was therefore tested here for the first time. Another unexplored issue addressed here, is the outcome of replacing classical antigen inclusion into nanovesicles by their physical mixture. Our results showed that UDA behaved as super-stable nanovesicles because of its high endurance during heat sterilization and storage for 5 months at 40°C. The archaeolipid content of UDA however, was insufficient to protect it against lyophilization, which demanded the addition of 2.5% v/v glycerol plus 0.07% w/v glucose. No significant differences were found between serum anti-ovalbumin (OVA) IgG titers induced by fresh or _SLRUDA upon topical application of 4 weekly doses at 600μg lipids/75μg OVA to Balb/c mice. Finally, _SLRUDA mixed with OVA elicited the same Th2 biased plus a non-specific cell mediated response than OVA encapsulated within UDA. Concluding, we showed that TPA is key component of super-stable nanovesicles that confers resistance to heat sterilization and to storage under cold-free conditions. The finding of _SLRUDA as ready-to-use topical adjuvant would lead to simpler manufacture processing and cheaper products. .

Cancer nanoimmunotherapy using advanced pharmaceutical nanotechnology

Immunotherapy is a promising option for cancer treatment that might cure cancer with fewer side effects by primarily activating the host's immune system. However, the effect of traditional immunotherapy is modest, frequently due to tumor escape and resistance of multiple mechanisms. Pharmaceutical nanotechnology, which is also called cancer nanotechnology or nanomedicine, has provided a practical solution to solve the limitations of traditional immunotherapy. This article reviews the latest developments in immunotherapy and nanomedicine, and illustrates how nanocarriers (including micelles, liposomes, polymer-drug conjugates, solid lipid nanoparticles and biodegradable nanoparticles) could be used for the cellular transfer of immune effectors for active and passive nanoimmunotherapy. The fine engineering of nanocarriers based on the unique features of the tumor microenvironment and extra-/intra-cellular conditions of tumor cells can greatly tip the triangle immunobalance among host, tumor and nanoparticulates in favor of antitumor responses, which shows a promising prospect for nanoimmunotherapy.

Devices for dry powder drug delivery to the lung

Dry powder inhalers (DPIs) are an important and increasingly investigated method of modern therapy for a growing number of respiratory diseases. DPIs are a promising option for certain patient populations, and may help to overcome several limitations that are associated with other types of inhalation delivery systems (e.g., accuracy and reproducibility of the dose delivered, compliance and adherence issues, or environmental aspects). Today, more than 20 different dry powder inhalers are on the market to deliver active pharmaceutical ingredients (APIs) for local and/or systemic therapy. Depending on the mechanism of deagglomeration, aerosolization, dose metering accuracy, and the interpatient variability, dry powder inhalers demonstrate varying performance levels. During development, manufacturers focus on improving aspects characteristic of their specific DPI devices, depending on the intended type of application and any particular requirements associated with it. With the wide variety of applications related to specific APIs, there exists a range of different devices with distinct features. In addition to the routinely used multi-use DPIs, several single-use disposable devices are under development or already approved. The recent introduction of disposable devices will expand the range of possible applications for use by including agents such as vaccines, analgesics, or even rescue medications. This review article discusses the performance and advantages of recently approved dry powder inhalers as well as disposable single-use inhalers that are currently under development.

Spray-Dried Influenza Antigen with Trehalose and Leucine Produces an Aerosolizable Powder Vaccine Formulation that Induces Strong Systemic and Mucosal Immunity after Pulmonary Administration

BACKGROUND

Pulmonary immunization has recently gained increased interest as a means to induce both systemic and mucosal immunity while eliminating issues associated with the use of needles in parenteral vaccination. However, in contrast to the inhaled delivery of small molecule drugs, a dry powder carrier platform that is readily adaptable to the incorporation of biomacromolecules (e.g., vaccine antigens) as a common standard is lacking. Spray-dried trehalose with leucine has previously been characterized and demonstrated to produce highly aerosolizable powders containing an amorphous glassy matrix suitable for stabilization of biomacromolecules. This study aimed to further extend the understanding in the use of this formulation as a dry powder carrier platform in an in vivo setting, using influenza antigen as a model, for pulmonary delivery of biomacromolecules.

METHODS

Spray-dried influenza vaccine was produced using previously established spray-drying conditions. The formulations were characterized to examine the impact of influenza antigen on the solid-state properties of the spray-dried powders. The optimal vaccine formulation was then selected for in vivo immunogenicity study in rats to evaluate the efficacy of the reconstituted spray-dried vaccine compared to liquid vaccine administered via pulmonary and subcutaneous routes.

RESULTS

The formation of amorphous glassy matrix and morphology of the spray-dried particles, within the protein concentration range used in the study, was not affected by the incorporation of the influenza antigen. However, the amount of proteins incorporated increased water content and reduced the glass transition temperature (Tg) of the formulation. Nevertheless, the spray-dried vaccine induced strong mucosal and systemic immunity comparable to liquid vaccine after pulmonary and subcutaneous immunization without causing any inflammation to the lung parenchyma.

CONCLUSIONS

The study demonstrated the usability of the spray-dried carrier as a promising platform for pulmonary delivery of influenza vaccine. The potential utility of this delivery system for other biomacromolecules may also be further explored.

Nano polymeric carrier fabrication technologies for advanced antitumor therapy

Comparing with the traditional therapeutic methods, newly developed cancer therapy based on the nanoparticulates attracted extensively interest due to its unique advantages. However, there are still some drawbacks such as the unfavorable in vivo performance for nanomedicine and undesirable tumor escape from the immunotherapy. While as we know that the in vivo performance strongly depended on the nanocarrier structural properties, thus, the big gap between in vitro and in vivo can be overcome by nanocarrier's structural tailoring by fine chemical design and microstructural tuning. In addition, this fine nanocarrier's engineering can also provide practical solution to solve the problems in traditional cancer immunotherapy. In this paper, we review the latest development in nanomedicine, cancer therapy, and nanoimmunotherapy. We then give an explanation why fine nanocanrrie's engineering with special focus on the unique pathology of tumor microenvironments and properties of immunocells can obviously promote the in vivo performance and improve the therapeutic index of nanoimmunotherapy.

Nanocarriers targeting dendritic cells for pulmonary vaccine delivery

Pulmonary vaccine delivery has gained significant attention as an alternate route for vaccination without the use of needles. Immunization through the pulmonary route induces both mucosal and systemic immunity, and the delivery of antigens in a dry powder state can overcome some challenges such as cold-chain and availability of medical personnel compared to traditional liquid-based vaccines. Antigens formulated as nanoparticles (NPs) reach the respiratory airways of the lungs providing greater chance of uptake by relevant immune cells. In addition, effective targeting of antigens to the most 'professional' antigen presenting cells (APCs), the dendritic cells (DCs) yields an enhanced immune response and the use of an adjuvant further augments the generated immune response thus requiring less antigen/dosage to achieve vaccination. This review discusses the pulmonary delivery of vaccines, methods of preparing NPs for antigen delivery and targeting, the importance of targeting DCs and different techniques involved in formulating dry powders suitable for inhalation.

Microneedles: an emerging transdermal drug delivery system

OBJECTIVES

One of the thrust areas in drug delivery research is transdermal drug delivery systems (TDDS) due to their characteristic advantages over oral and parenteral drug delivery systems. Researchers have focused their attention on the use of microneedles to overcome the barrier of the stratum corneum. Microneedles deliver the drug into the epidermis without disruption of nerve endings. Recent advances in the development of microneedles are discussed in this review for the benefit of young scientists and to promote research in the area.

KEY FINDINGS

Microneedles are fabricated using a microelectromechanical system employing silicon, metals, polymers or polysaccharides. Solid coated microneedles can be used to pierce the superficial skin layer followed by delivery of the drug. Advances in microneedle research led to development of dissolvable/degradable and hollow microneedles to deliver drugs at a higher dose and to engineer drug release. Iontophoresis, sonophoresis and electrophoresis can be used to modify drug delivery when used in concern with hollow microneedles. Microneedles can be used to deliver macromolecules such as insulin, growth hormones, immunobiologicals, proteins and peptides. Microneedles containing 'cosmeceuticals' are currently available to treat acne, pigmentation, scars and wrinkles, as well as for skin tone improvement.

SUMMARY

Literature survey and patents filled revealed that microneedle-based drug delivery system can be explored as a potential tool for the delivery of a variety of macromolecules that are not effectively delivered by conventional transdermal techniques.

An overview on the field of micro- and nanotechnologies for synthetic Peptide-based vaccines

The development of synthetic peptide-based vaccines has many advantages in comparison with vaccines based on live attenuated organisms, inactivated or killed organism, or toxins. Peptide-based vaccines cannot revert to a virulent form, allow a better conservation, and are produced more easily and safely. However, they generate a weaker immune response than other vaccines, and the inclusion of adjuvants and/or the use of vaccine delivery systems is almost always needed. Among vaccine delivery systems, micro- and nanoparticulated ones are attractive, because their particulate nature can increase cross-presentation of the peptide. In addition, they can be passively or actively targeted to antigen presenting cells. Furthermore, particulate adjuvants are able to directly activate innate immune system in vivo. Here, we summarize micro- and nanoparticulated vaccine delivery systems used in the field of synthetic peptide-based vaccines as well as strategies to increase their immunogenicity.

Topical and mucosal liposomes for vaccine delivery

Mucosal (and in minor extent transcutanous) stimulation can induce local or distant mucosa secretory IgA. Liposomes and other vesicles as mucosal and transcutaneous adjuvants are attractive alternatives to parenteral vaccination. Liposomes can be massively produced under good manufacturing practices and stored for long periods, at high antigen/vesicle mass ratios. However, their uptake by antigen-presenting cells (APC) at the inductive sites remains as a major challenge. As neurotoxicity is a major concern in intranasal delivery, complexes between archaeosomes and calcium as well as cationic liposomes complexed with plasmids encoding for antigenic proteins could safely elicit secretory and systemic antigen-specific immune responses. Oral bilosomes generate intense immune responses that remain to be tested against challenge, but the admixing with toxins or derivatives is mandatory to reduce the amount of antigen. Most of the current experimental designs, however, underestimate the mucus blanket 100- to 1000-fold thicker than a 100-nm diameter liposome, which has first to be penetrated to access the underlying M cells. Overall, designing mucoadhesive chemoenzymatic resistant liposomes, or selectively targeted to M cells, has produced less relevant results than tailoring the liposomes to make them mucus penetrating. Opposing, the nearly 10 µm thickness stratum corneum interposed between liposomes and underlying APC can be surpassed by ultradeformable liposomes (UDL), with lipid matrices that penetrate up to the limit with the viable epidermis. UDL made of phospholipids and detergents, proved to be better transfection agents than conventional liposomes and niosomes, without the toxicity of ethosomes, in the absence of classical immunomodulators.

Adjuvants in tuberculosis vaccine development

Tuberculosis remains a major public health problem around the world. Because the Mycobacterium bovis Bacilli-Calmette-Guerin (BCG) vaccine fails to protect adults from pulmonary tuberculosis, there is an urgent need for improved vaccine formulations. Unlike BCG, recombinant vaccines purified from bacterial expression vectors, as well as naked DNA, require an additional adjuvant. Recent improvements in our understanding of disease immunopathology, together with advances in biochemical and molecular techniques, have permitted the successful development of promising tuberculosis vaccine delivery and adjuvant combinations for human use. Here, we summarize the current state of adjuvant development and its impact on tuberculosis vaccine progress.