Epidermal powder immunization induces both cytotoxic T-lymphocyte and antibody responses to protein antigens of influenza and hepatitis B viruses

Applications of Gold Nanoparticles in Nanomedicine: Recent Advances in Vaccines

Nowadays, gold is used in (nano-)medicine, usually in the form of nanoparticles, due to the solid proofs given of its therapeutic effects on several diseases. Gold also plays an important role in the vaccine field as an adjuvant and a carrier, reducing toxicity, enhancing immunogenic activity, and providing stability in storage. An even brighter golden future is expected for gold applications in this area.

Ultrasound-enhanced transdermal delivery: recent advances and future challenges

The skin is a formidable diffusion barrier that restricts passive diffusion to small (<500 Da) lipophilic molecules. Methods used to permeabilize this barrier for the purpose of drug delivery are maturing as an alternative to oral drug delivery and hypodermic injections. Ultrasound can reversibly and non-invasively permeabilize the diffusion barrier posed by the skin. This review discusses the mechanisms of ultrasound-permeability enhancement, and presents technological innovations in equipment miniaturization and recent advances in permeabilization capabilities. Additionally, potentially exciting applications, including protein delivery, vaccination, gene therapy and sensing of blood analytes, are discussed. Finally, the future challenges and opportunities associated with the use of ultrasound are discussed. It is stressed that developing ultrasound for suitable applications is key to ensure commercial success.

Proteolistics: a biolistic method for intracellular delivery of proteins

In this work, an intracellular protein delivery methodology termed "proteolistics" is described. This method utilizes a biolistic gun apparatus and involves a simple protein/projectile preparation step. The protein to be delivered is mixed with a gold particle microprojectile suspension and is placed onto a gene gun cartridge, where it is dehydrated using either lyophilization or room-temperature air-drying. Subsequent intracellular protein delivery is achieved in plant and mammalian tissues upon bombardment. Because the method does not require modification of delivery agents or cargo biomolecules and involves a simple physical deposition of the protein onto the microprojectiles, there is no restriction on protein type in terms of molecular weight, isoelectric point or tertiary structure. Because the method delivers protein through the widely used gene gun system, it can be readily applied to any tissue or organism amenable to biolistics. A variety of proteins with molecular weight ranging from 24 to 68 kDa and isoelectric point from 4.8 to 10.1 were tested in this work. It is anticipated that this simple and versatile technique will offer biologists a powerful tool for basic research in areas such as understanding of cell and gene functions and for biotechnological applications such as genome editing.

Skin permeabilization for transdermal drug delivery: recent advances and future prospects

INTRODUCTION

Transdermal delivery has potential advantages over other routes of administration. It could reduce first-pass metabolism associated with oral delivery and is less painful than injections. However, the outermost layer of the skin, the stratum corneum (SC), limits passive diffusion to small lipophilic molecules. Therefore, methods are needed to safely permeabilize the SC so that ionic and larger molecules may be delivered transdermally.

AREAS COVERED

This review focuses on low-frequency sonophoresis, microneedles, electroporation and iontophoresis, and combinations of these methods to permeabilize the SC. The mechanisms of enhancements and developments in the last 5 years are discussed. Potentially high-impact applications, including protein delivery, vaccination and sensing are presented. Finally, commercial interest and clinical trials are discussed.

EXPERT OPINION

Not all permeabilization methods are appropriate for all applications. Focused studies into applications utilizing the advantages of each method are needed. The total dose and kinetics of delivery must be considered. Vaccination is one application where permeabilization methods could make an impact. Protein delivery and analyte sensing are also areas of potential impact, although the amount of material that can be delivered (or extracted) is of critical importance. Additional work on the miniaturization of these technologies will help to increase commercial interest.

Skin immunization with influenza vaccines

Problems with existing influenza vaccines include the strain specificity of the immune response, resulting in the need for frequent reformulation in response to viral antigenic drift. Even in years when the same influenza strains are prevalent, the duration of immunity is limited, and results in the need for annual revaccination. The immunogenicity of the present split or subunit vaccines is also lower than that observed with whole inactivated virus, and the vaccines are not very effective in high risk groups such as the young or the elderly. Vaccine coverage is incomplete, due in part to concerns about the use of hypodermic needles for delivery. Alternative approaches for vaccination are being developed which address many of these concerns. Here we review new approaches which focus on skin immunization, including the development of needle-free delivery systems which use stable dry formulations and induce stronger and longer-lasting immune responses.

Transcutaneous vaccines--current and emerging strategies

INTRODUCTION

Vaccination, which is the major fundamental prophylaxis against illness and death from infectious disease, has greatly contributed to the global improvement of human health. However, the disadvantages of conventional injection systems hamper the delivery of vaccination technologies to developing countries. The imminent practice of easy-to-use vaccination methods is expected to overcome certain issues associated with injectable vaccinations. One innovative method is the transcutaneous immunization (TCI) system.

AREAS COVERED

Two major strategies for TCI are discussed in this review. One is to promote antigen permeation of the skin barrier by patch systems or nanoparticles. The other is the delivery of antigens into the skin by electroporation and microneedles in order to physically overcome the skin barrier. Moreover, adjuvant development for TCI is discussed.

EXPERT OPINION

Many different approaches have been developed for TCI, which have the potential to be effective, easy-to-use and painless methods of vaccination. However, in practical terms, the guidelines concerning the manufacturing processes and clinical trial evaluation of the procedures have not kept pace with the development of these novel formulations. The accumulation of information regarding skin characteristics and the properties of TCI devices will help refine TCI system development guidelines and thus lead to the improvement of transcutaneous vaccination.

Microneedle and mucosal delivery of influenza vaccines

In recent years with the threat of pandemic influenza and other public health needs, alternative vaccination methods other than intramuscular immunization have received great attention. The skin and mucosal surfaces are attractive sites probably because of both noninvasive access to the vaccine delivery and unique immunological responses. Intradermal vaccines using a microinjection system (BD Soluvia(TM)) and intranasal vaccines (FluMist®) are licensed. As a new vaccination method, solid microneedles have been developed using a simple device that may be suitable for self-administration. Because coated microneedle influenza vaccines are administered in the solid state, developing formulations maintaining the stability of influenza vaccines is an important issue to be considered. Marketable microneedle devices and clinical trials remain to be developed. Other alternative mucosal routes such as oral and intranasal delivery systems are also attractive for inducing cross-protective mucosal immunity, but effective non-live mucosal vaccines remain to be developed.

Comparison of the immunogenicity and safety of a split-virion, inactivated, trivalent influenza vaccine (Fluzone®) administered by intradermal and intramuscular route in healthy adults

The aim of the study was to determine whether reduced doses of trivalent inactivated influenza vaccine (TIV) administered by the intradermal (ID) route generated similar immune responses to standard TIV given intramuscularly (IM) with comparable safety profiles. Recent changes in immunization recommendations have increased the number of people for whom influenza vaccination is recommended. Thus, given this increased need and intermittent vaccine shortages, means to rapidly expand the vaccine supply are needed. Previously healthy subjects 18-64 years of age were randomly assigned to one of four TIV vaccine groups: standard 15 μg HA/strain TIV IM, either 9 μg or 6 μg HA/strain of TIV ID given using a new microinjection system (BD Soluvia™ Microinjection System), or 3 μg HA/strain of TIV ID given by Mantoux technique. All vaccines contained A/New Caledonia (H1N1), A/Wyoming (H3N2) and B/Jiangsu strains of influenza. Sera were obtained 21 days after vaccination and hemagglutination inhibition (HAI) assays were performed and geometric mean titers (GMT) were compared among the groups. Participants were queried immediately following vaccination regarding injection pain and quality of the experience. Local and systemic reactions were collected for 7 days following vaccination and compared. Ten study sites enrolled 1592 subjects stratified by age; 18-49 years [N=814] and 50-64 years [N=778]. Among all subjects, for each of the three vaccine strains, the GMTs at 21 days post-vaccination for both the 9 μg and the 6 μg doses of each strain given ID were non inferior to GMTs generated after standard 15 μg doses/strain IM. However, for the 3 μg ID dose, only the A/Wyoming antigen produced a GMT that was non-inferior to the standard IM dose. Additionally, in the subgroup of subjects 50-64 years of age, the 6μg dose given ID induced GMTs that were inferior to the standard IM TIV for the A/H1N1 and B strains. No ID dose produced a GMT superior to that seen after standard IM TIV. Local erythema and swelling were significantly more common in the ID groups but the reactions were mild to moderate and short-lived. No significant safety issues related to intradermal administration were identified. Participants given TIV ID provided favorable responses to questions about their experiences with ID administration. In conclusion, for the aggregated cohorts of adults 18-64 years of age, reduced doses (6 μg and 9 μg) of TIV delivered ID using a novel microinjection system stimulated comparable HAI antibody responses to standard TIV given IM. The reduced 3 μg dose administered ID by needle and syringe, as well as the 6 μg ID for subjects aged 50-64 years of age generated poorer immune responses as compared to the 15 μg IM dose.

Progress towards a needle-free hepatitis B vaccine

Hepatitis B virus (HBV) infection is a worldwide public health problem. Vaccination is the most efficient way to prevent hepatitis B. Despite the success of the currently available vaccine, there is a clear need for the development of new generation of HBV vaccines. Needle-free immunization is an attractive approach for mass immunization campaigns, since avoiding the use of needles reduces the risk of needle-borne diseases and prevents needle-stick injuries and pain, thus augmenting patient compliance and eliminating the need for trained medical personnel. Moreover, this kind of immunization was shown to induce good systemic as well as mucosal immunological responses, which is important for the creation of both a prophylactic and therapeutic vaccine. In order to produce a better, safer, more efficient and more suitable vaccine, adjuvants have been used. In this article, several adjuvants tested over the years for their potential to help create a needle-free vaccine against HBV are reviewed.

Needle-free influenza vaccination

Vaccination is the cornerstone of influenza control in epidemic and pandemic situations. Influenza vaccines are typically given by intramuscular injection. However, needle-free vaccinations could offer several distinct advantages over intramuscular injections: they are pain-free, easier to distribute, and easier to give to patients, and their use could reduce vaccination costs. Moreover, vaccine delivery via the respiratory tract, alimentary tract, or skin might elicit mucosal immune responses at the site of virus entry and better cellular immunity, thus improving effectiveness. Although various needle-free vaccination methods for influenza have shown preclinical promise, few have progressed to clinical trials-only live attenuated intranasal vaccines have received approval, and only in some countries. Further clinical investigation is needed to help realise the potential of needle-free vaccination for influenza.

Spray-freeze-drying of nanosuspensions: the manufacture of insulin particles for needle-free ballistic powder delivery

The feasibility of preparing microparticles with high insulin loading suitable for needle-free ballistic drug delivery by spray-freeze-drying (SFD) was examined in this study. The aim was to manufacture dense, robust particles with a diameter of around 50 microm, a narrow size distribution and a high content of insulin. Atomization using ultrasound atomizers showed improved handling of small liquid quantities as well as narrower droplet size distributions over conventional two-fluid nozzle atomization. Insulin nanoparticles were produced by SFD from solutions with a low solid content (<10 mg ml(-1)) and subsequent ultra-turrax homogenization. To prepare particles for needle-free ballistic injection, the insulin nanoparticles were suspended in matrix formulations with a high excipient content (>300 mg ml(-1)) consisting of trehalose, mannitol, dextran (10 kDa) and dextran (150 kDa) (abbreviated to TMDD) in order to maximize particle robustness and density after SFD. With the increase in insulin content, the viscosity of the nanosuspensions increased. Liquid atomization was possible up to a maximum of 250 mg of nano-insulin suspended in a 1.0 g matrix. However, if a narrow size distribution with a good correlation between theoretical and measurable insulin content was desired, no more than 150 mg nano-insulin could be suspended per gram of matrix formulation. Particles were examined by laser light diffraction, scanning electron microscopy and tap density testing. Insulin stability was assessed using size exclusion chromatography (SEC), reverse phase chromatography and Fourier transform infrared (FTIR) spectroscopy. Densification of the particles could be achieved during primary drying if the product temperature (T(prod)) exceeded the glass transition temperature of the freeze concentrate (T(g)') of -29.4 degrees C for TMDD (3331) formulations. Particles showed a collapsed and wrinkled morphology owing to viscous flow of the freeze concentrate. With increasing insulin loading, the d (v, 0.5) of the SFD powders increased and particle size distributions got wider. Insulin showed a good stability during the particle formation process with a maximum decrease in insulin monomer of only 0.123 per cent after SFD. In accordance with the SEC data, FTIR analysis showed only a small increase in the intermolecular beta-sheet of 0.4 per cent after SFD. The good physical stability of the polydisperse particles made them suitable for ballistic injection into tissue-mimicking agar hydrogels, showing a mean penetration depth of 251.3 +/- 114.7 microm.

Physicochemical and immunological characterization of N,N,N-trimethyl chitosan-coated whole inactivated influenza virus vaccine for intranasal administration

PURPOSE

The purpose of this study was the development and physicochemical and immunological characterization of intranasal (i.n.) vaccine formulations of whole inactivated influenza virus (WIV) coated with N,N,N-trimethyl chitosan (TMC).

METHODS

Synthesized TMCs with a degree of quarternization of 15% (TMC15) or 37% (TMC37) were tested in vitro for their ability to decrease the transepithelial resistance (TEER) of an epithelial cell monolayer. TMC15- and TMC37-coated WIV (TMC15-WIV and TMC37-WIV) were characterized by zeta potential measurements, dynamic light scattering, electron microscopy and gel permeation chromatography. Mice were vaccinated i.n. with selected vaccine formulations and immunogenicity was determined by measuring serum hemagglutination inhibition (HI) and serum IgG, IgG1 and IgG2a/c titers. Also a pulse-chase study with TMCs in solution administered i.n. 2 h prior to WIV was performed. Protective efficacy of vaccination was determined by an aerosol virus challenge.

RESULTS

TMC37 induced a reversible decrease in TEER, suggesting the opening of tight junctions, whereas TMC15 did not affect TEER. Simple mixing of (negatively charged) WIV with TMC15 or TMC37 resulted in positively charged particles with TMCs being partially bound. Intranasal immunization with TMC37-WIV or TMC15-WIV induced stronger HI, IgG, IgG1 and IgG2a/c titers than WIV alone. TMC37-WIV induced the highest immune responses. Both TMC15-WIV and TMC37-WIV provided protection against challenge, whereas WIV alone was not protective. Intranasal administration of TMC prior to WIV did not result in significant immune responses, indicating that the immunostimulatory effect of TMC is primarily based on improved i.n. delivery of WIV.

CONCLUSIONS

Coating of WIV with TMC is a simple procedure to improve the delivery and immunogenicity of i.n. administered WIV and may enable effective i.n. vaccination against influenza.

Micro-scale devices for transdermal drug delivery

Skin makes an excellent site for drug and vaccine delivery due to easy accessibility, immuno-surveillance functions, avoidance of macromolecular degradation in the gastrointestinal tract and possibility of self-administration. However, macromolecular drug delivery across the skin is primarily accomplished using hypodermic needles, which have several disadvantages including accidental needle-sticks, pain and needle phobia. These limitations have led to extensive research and development of alternative methods for drug and vaccine delivery across the skin. This review focuses on the recent trends and developments in this field of micro-scale devices for transdermal macromolecular delivery. These include liquid jet injectors, powder injectors, microneedles and thermal microablation. The historical perspective, mechanisms of action, important design parameters, applications and challenges are discussed for each method.

A bivalent influenza VLP vaccine confers complete inhibition of virus replication in lungs

The conventional egg-grown influenza vaccines are trivalent. To test the feasibility of using multivalent influenza virus-like particles (VLPs) as an alternative influenza vaccine, we developed cell-derived influenza VLPs containing the hemagglutinin (HA) of the H1 subtype virus A/PR/8/34 or the H3 subtype virus A/Aichi/2/68 (X31). Mice immunized intramuscularly with bivalent influenza VLPs containing H1 and H3 HAs induced neutralizing activities against the homologous and closely related H1N1 strains A/PR/8/34 and A/WSN/33 as well as the H3N2 strains A/Aichi/2/68 (X31) and A/Hong Kong/68, but not the A/Philippines/2/82 strain isolated 14 years later. HA sequence and structure analysis indicated that antigenic distance could be a major factor in predicting cross-protection by VLP vaccines. The bivalent influenza VLP vaccine demonstrated advantages in broadening the protective immunity after lethal challenge infections when compared to a monovalent influenza VLP vaccine. High levels of the inflammatory cytokine IL-6 were observed in naïve or unprotected immunized mice but not in protected mice upon lethal challenge. These results indicate that multivalent influenza VLP vaccines can be an effective antigen for developing safe and alternative vaccine to control the spread of influenza viruses.

Needle-free vaccine delivery

The need for minimally invasive delivery methods is urgent. As the number of registered vaccines increases, so does the number of injections. The use of sharps can be unsafe and needle immunisation is less suitable for mass immunisations during emergencies such as pandemics or bioterrorist attacks. The approach of combining vaccines has limitations due to high development costs, risk of pharmaceutical or immunological interference and economic risks. Advancements in the development of alternatives to injection with syringes and needles are discussed in this paper, and include: mucosal vaccination, injection without needles and vaccine delivery via the skin.

A phase I study of immunization using particle-mediated epidermal delivery of genes for gp100 and GM-CSF into uninvolved skin of melanoma patients

PURPOSE

We examined in vivo particle-mediated epidermal delivery (PMED) of cDNAs for gp100 and granulocyte macrophage colony-stimulating factor (GM-CSF) into uninvolved skin of melanoma patients. The aims of this phase I study were to assess the safety and immunologic effects of PMED of these genes in melanoma patients.

EXPERIMENTAL DESIGN

Two treatment groups of six patients each were evaluated. Group I received PMED with cDNA for gp100, and group II received PMED with cDNA for GM-CSF followed by PMED for gp100 at the same site. One vaccine site per treatment cycle was biopsied and divided for protein extraction and sectioning to assess transgene expression, gold-bead penetration, and dendritic cell infiltration. Exploratory immunologic monitoring of HLA-A2(+) patients included flow cytometric analyses of peripheral blood lymphocytes and evaluation of delayed-type hypersensitivity to gp100 peptide.

RESULTS

Local toxicity in both groups was mild and resolved within 2 weeks. No systemic toxicity could be attributed to the vaccines. Monitoring for autoimmunity showed no induction of pathologic autoantibodies. GM-CSF transgene expression in vaccinated skin sites was detected. GM-CSF and gp100 PMED yielded a greater infiltration of dendritic cells into vaccine sites than did gp100 PMED only. Exploratory immunologic monitoring suggested modest activation of an antimelanoma response.

CONCLUSIONS

PMED with cDNAs for gp100 alone or in combination with GM-CSF is well tolerated by patients with melanoma. Moreover, pathologic autoimmunity was not shown. This technique yields biologically active transgene expression in normal human skin. Although modest immune responses were observed, additional investigation is needed to determine how to best utilize PMED to induce antimelanoma immune responses.

Topical vaccination: the skin as a unique portal to adaptive immune responses

Skin is an ideal tissue for vaccine administration, as it is comprised of immunocompetent cells such as keratinocytes and Langerhans cells and elicits both innate and adaptive immune responses. In this paper, we summarize the immune responses induced by topical vaccination of the skin and review the effects of adjuvants on skin vaccination. We also summarize the existing techniques for skin vaccination. New techniques such as the use of lasers to enhance skin permeability are also discussed, as well as the role of the stratum corneum in skin vaccination. A recent study demonstrating enhanced skin vaccination by using surfactants to extract partial lamellar lipids of the stratum corneum will also be introduced in this review.

Hepatocellular carcinoma: therapy and prevention

Hepatocellular carcinoma (HCC) is one of the most common malignant tumors worldwide. The major etiologies and risk factors for the development of HCC are well defined and some of the multiple steps involved in hepatocarcinogenesis have been elucidated in recent years. Despite these scientific advances and the implementation of measures for the early detection of HCC in patients at risk, patient survival has not improved during the last three decades. This is due to the advanced stage of the disease at the time of clinical presentation and limited therapeutic options. The therapeutic options fall into five main categories: surgical interventions including tumor resection and liver transplantation, percutaneous interventions including ethanol injection and radiofrequency thermal ablation, transarterial interventions including embolization and chemoembolization, radiation therapy and drugs as well as gene and immune therapies. These therapeutic strategies have been evaluated in part in randomized controlled clinical trials that are the basis for therapeutic recommendations. Though surgery, percutaneous and transarterial interventions are effective in patients with limited disease (1-3 lesions, <5 cm in diameter) and compensated underlying liver disease (cirrhosis Child A), at the time of diagnosis more than 80% patients present with multicentric HCC and advanced liver disease or comorbidities that restrict the therapeutic measures to best supportive care. In order to reduce the morbidity and mortality of HCC, early diagnosis and the development of novel systemic therapies for advanced disease, including drugs, gene and immune therapies as well as primary HCC prevention are of paramount importance. Furthermore, secondary HCC prevention after successful therapeutic interventions needs to be improved in order to make an impact on the survival of patients with HCC. New technologies, including gene expression profiling and proteomic analyses, should allow to further elucidate the molecular events underlying HCC development and to identify novel diagnostic markers as well as therapeutic and preventive targets.

A review of vaccine research and development: human acute respiratory infections

Worldwide, acute respiratory infections (ARIs) constitute the leading cause of acute illnesses, being responsible for nearly 4 million deaths every year, mostly in young children and infants in developing countries. The main infectious agents responsible for ARIs include influenza virus, respiratory syncytial virus (RSV), parainfluenza virus type 3 (PIV-3), Streptococcus pneumoniae and Haemophilus influenzae. While effective vaccines against influenza, H. influenzae type b (Hib) and S. pneumoniae infections have been available for several years, no vaccine is available at present against illnesses caused by RSV, PIV-3, metapneumovirus or any of the three novel coronaviruses. In addition, the threat constituted by the multiple outbreaks of avian influenza during the last few years is urgently calling for the development of new influenza vaccines with broader spectrum of efficacy, which could provide immunity against an avian influenza virus pandemic. This article reviews the state of the art in vaccine R&D against ARIs and attempts to address these basic public health questions.

Epidermal delivery of protein and DNA vaccines

Targeting vaccines to the skin epidermis results in the activation of an immune inductive site that is rich in antigen-presenting cells. The superficial location of the skin makes it accessible to vaccine delivery. However, it is difficult to access the epidermis using needle and syringe delivery, and vaccine antigens are too large to be effectively delivered using standard topical formulations. Needle-free vaccine delivery systems have been developed for efficient delivery of particulate vaccines into the epidermal tissue. Particle-mediated epidermal delivery of DNA vaccines is based on the delivery of DNA-coated gold particles directly into the cytoplasm and nuclei of living cells of the epidermis, facilitating DNA delivery and gene expression. Alternatively, protein vaccines can be formulated into a dense powder, which can be propelled into the skin epidermis by epidermal powder immunisation using similar delivery devices and principles, but in this instance the protein is delivered to the extracellular space. Preclinical and clinical data will be reviewed, demonstrating applications of epidermal vaccine delivery to a wide range of experimental infectious disease vaccines.

Characterization of powdered epidermal vaccine delivery with multiphoton microscopy

Multiphoton laser scanning microscopy (MPLSM) has been adapted to non-invasively characterize hand-held powdered epidermal vaccine delivery technology. A near infrared femtosecond pulsed laser, wavelength at approximately 920 nm, was used to evoke autofluorescence of endogenous fluorophores within ex vivo porcine and human skin. Consequently, sub cellular resolution three-dimensional images of stratum corneum and viable epidermal cells were acquired and utilized to observe the morphological deformation of these cells as a result of micro-particle penetration. Furthermore, the distributional pattern of micro-particles within the specific skin target volume was quantified by measuring the penetration depth as revealed by serial optical sections in the axial plane obtained with MPLSM. Additionally, endogenous fluorescence contrast images acquired at the supra-basal layer reveal cellular structures that may pertain to dendritic Langerhans cells of the epidermis. These results show that MPLSM has advantages over conventional histological approaches, since three-dimensional functional images with sub-cellular spatial resolution to depths beyond the epidermis can be acquired non-invasively. Accordingly, we propose that MPLSM is ideal for investigations of powdered epidermal vaccine delivery.

Evaluation of SIV-lipopeptide immunizations administered by the intradermal route in their ability to induce antigen specific T-cell responses in rhesus macaques

Numerous clinical and experimental observations have shown that cellular immunity, in particular CD8+ T-lymphocytes, plays an important role in the control of HIV infection. We have focused on a lipopeptide vaccination strategy that has been shown to induce polyepitopic T-cell responses in both animals and humans, in order to deliver simian immunodeficiency virus (SIV) antigens to rhesus macaques. Given the relevance of antigen administration route in the development of an effective cellular immune response, this study was designed to assess SIV lipopeptide immunizations administered either by the intradermal (ID) or the intramuscular (IM) routes in their ability to elicit GAG and NEF multispecific T-lymphocytes in the rhesus macaque. Antigen specific T-cell responses were observed between 7 and 11 weeks following vaccination in both groups. Macaques immunized by the IM route yielded antigen-specific IFN-gamma secreting lymphocytes in response to no more than two pools of peptides derived from SIV-NEF. In contrast, among the four ID-immunized macaques, two presented multi-specific T-cell responses to as many as four pools of SIV-NEF and/or GAG peptides. Responses persisted 16 weeks following the vaccination protocol in one of the ID-vaccinated macaques. The induction of such responses is of great clinical relevance in the development of an effective HIV vaccine. Given the crucial role of CD8+ T-lymphocytes in HIV/SIV containment, vaccination through the intradermal route should merit high consideration in the development of an AIDS vaccine.

Treatment of hepatocellular carcinoma

Hepatocellular carcinoma (HCC) is one of the most common malignant tumours worldwide. The major etiologies and risk factors for HCC development are well defined and some of the multiple steps involved in hepatocarcinogenesis have been elucidated in recent years. Despite these scientific advances and the implementation of measures for early HCC detection in patients at risk, patient survival has not improved during the last three decades. This is due in part to the advanced stage of the disease at the time of clinical presentation, in part due to the limited therapeutic options. These fall into four main categories: (1) surgical interventions, including tumour resection and liver transplantation, (2) percutaneous interventions, including ethanol injection and radiofrequency thermal ablation, (3) transarterial interventions, including embolisation and chemoembolisation and (4) drugs as well as gene and immune therapies. These therapeutic strategies have been evaluated in part in randomised controlled clinical trials that are the basis for therapeutic recommendations. While surgery and percutaneous as well as transarterial interventions are effective in patients with limited disease (1-3 lesions, < 5 cm in diameter) and compensated underlying liver disease (cirrhosis Child A), at the time of diagnosis more than 80% patients present with multicentric HCC and advanced liver disease or comorbidities that restrict the therapeutic measures to best supportive care. In order to reduce morbidity and mortality from HCC, therefore, early diagnosis and the development of novel systemic therapies for advanced disease, including drugs, gene and immune therapies as well as primary HCC prevention are of paramount importance. Further, secondary HCC prevention after successful therapeutic interventions needs to be improved in order to make an impact on the survival of patients with HCC. New technologies, including gene expression profiling and proteomic analyses, should further elucidate the molecular events underlying HCC development and identify novel diagnostic markers as well as therapeutic and preventive targets.

Influenza vaccine powder formulation development: spray-freeze-drying and stability evaluation

The purpose of this study was to develop a spray-freeze-drying (SFD) process for preparing an influenza vaccine dry powder formulation suitable for epidermal powder immunization. After preformulation of two types of flu vaccines, their dry-powder formulations were prepared by SFD. Powder properties and physical stability were determined using particle size analysis, tap density measurement, scanning electron microscopy, optical microscopy, and moisture content analysis. Chemical and biochemical stability of vaccine antigens was determined by sodium dodecyl sulfate-polyacrylamide gel electrophoresis, single radial immunodiffusion assay, and in vivo immunogenicity in a mouse model. We demonstrated that SFD could produce high-density particles-a critical parameter for effective skin penetration. From the stability perspective, the stress posed by SFD was mild because the antigen in the dry powder retained its stability, potency, and immunogenicity. Among several formulations screened, we noted that formulation composition has a significant role in the powder's long-term physical and biochemical stability. One formulation, in particular, containing sub-unit vaccine (45 microg of antigen in 1 mg of powder) with a tertiary mixture of trehalose, mannitol, and dextran, exhibited excellent overall stability, including acceptable biochemical stability after being exposed to a highly humid environment. After all, we have not only demonstrated the suitability of SFD to prepare powders for epidermal powder immunization but also developed a systematic formulation development strategy that allowed the optimization of an influenza vaccine dry powder formulation. More important, this study led to the selection of a formulation system that had been successfully tested in a human clinical study.

An antigen-independent but not antigen-specific T(H)1 response provides protection in the murine airway inflammation model

BACKGROUND

Atopic disorders are associated with an imbalanced T(H) cell response biased toward a strong T(H)2 type, resulting in excessive production of IgE antibodies, eosinophil recruitment and activation, and mast cell degranulation. Restoring the T(H)1-T(H)2 balance by increasing the antigen-specific T(H)1 response has been pursued for specific allergy immunotherapy. Synthetic oligodeoxynucleotides containing unmethylated CG dinucleotides (CpG) are strong T(H)1 adjuvants and are being investigated for allergy immunotherapy.

OBJECTIVE

This study was designed to investigate the protective role of antigen-specific T(H)1 responses induced by epidermal powder immunization with ovalbumin (OVA) and CpG in a murine airway inflammation model.

METHODS

An allergy model was used in which BALB/c mice were sensitized and then challenged with OVA. Mice received prophylactic or therapeutic immunizations with OVA, CpG, or both. After challenge, pulmonary inflammation and cell infiltration were measured on the basis of BAL cell counts and lung histology. Immune response was determined by measuring the levels of lavage cytokines and serum antibodies.

RESULTS

Coadministration of OVA and CpG by means of subcutaneous injection or epidermal powder immunization, although inducing a strong T(H)1 response, neither suppressed T(H)2 cytokines nor offered protection against pulmonary eosinophilia and histopathology in a mouse challenge model. However, when CpG was used as a stand-alone treatment of previously sensitized animals, protection against allergic airway inflammation was observed. After challenge with OVA, eosinophilia was suppressed in the lungs of the CpG-treated mice.

CONCLUSION

This finding argues against the approach of boosting an allergen-dependent T(H)1 response and favors induction of an antigen-independent T(H)1 response for allergy immunotherapy.

Epidermal powder immunization against influenza

Epidermal powder immunization (EPI) can efficiently deliver powdered protein vaccines to the epidermis. A phase I clinical trial was conducted to evaluate powdered trivalent influenza vaccine delivered using the PowderJect ND5.2 delivery system. Subjects received either Fluvirin IM injection (15 microg of each influenza strain), a single EPI vaccination (15 microg of each influenza strain) or two adjacent EPI (total of 30 microg of each influenza strain). Systemic reactogenicity was similar between control and EPI vaccines. Site reactions following EPI were primarily mild and self-limiting. Seroconversions, titer increases and geometric mean titers to all strains were equivalent or higher in EPI-immunized groups than in controls. Powdered influenza vaccine delivered by EPI is safe and elicits humoral immune responses in humans.

Identification of second harmonic optical effects from vaccine coated gold microparticles

This study investigates the optical effects observed from uncoated and protein vaccine coated gold microparticles while imaging with two-photon excitation in the Mie scattering regime. When observed with time correlated single photon counting fluorescence lifetime microscopy, the emission from the gold microparticles appeared as an intense instrument-limited temporal response. The intensity of the emission showed a second-order dependence on the laser power and frequency doubling of the emitted light was observed for fundamental light between 890 and 970 nm. The optical effect was attributed to two-photon induced second harmonic generation. The vaccine coated gold microparticles had a much weaker second harmonic signal than the uncoated gold microparticles. Chemical analysis of the surface of the gold microparticles revealed that the vaccine coating decreases the surface charge thereby diminishing the observed second harmonic signal. These optical properties can be exploited to identify both the location of the protein vaccine coating as well as the gold microparticles in vitro and potentially to investigate the vaccine delivery kinetics in vivo.

Epidermal powder immunization: cellular and molecular mechanisms for enhancing vaccine immunogenicity

Epidermal powder immunization (EPI) of mice with an influenza vaccine elicited consistently a higher hemagglutination inhibition (HI) antibody titers than intramuscular (IM) injection using the same dose of vaccine. The epidermal Langerhans cells (LCs) at the site of EPI were found to play an important role in the immune responses. Indeed, depletion of LCs from the immunization site prior to EPI caused a significant reduction in the antibody response. Transfer of LCs isolated from the EPI sites to naive mice induced a robust antigen-specific antibody response. Cytokines produced by target site cells appear to be important for the augmented immune responses induced by EPI. LTR72, a genetically detoxified heat-labile toxin from Escherichia coli with a strong adjuvant effect in EPI, was found to bind the keratinocytes of the epidermis, but not the LCs, and caused the production of elevated TNF-alpha and IL-12 cytokines in emigrating epidermal cells. These results have important implications for the development of a more efficacious human influenza vaccine.

Transcutaneous immunization induces mucosal CTLs and protective immunity by migration of primed skin dendritic cells

Transcutaneous immunization (TCI), the application of vaccines on the skin, induces robust systemic and mucosal antibodies in animal models and in humans. The means by which mucosal immune responses to vaccine antigens are elicited by TCI has not been well characterized. We examined the effect of TCI with an HIV peptide vaccine on the induction of mucosal and systemic CTL responses and protective immunity against mucosal challenge with live virus in mice. Robust HIV-specific CTL responses in the spleen and in the gut mucosa were detected after TCI. The responses were dependent upon the addition of an adjuvant and resulted in protection against mucosal challenge with recombinant vaccinia virus encoding HIV gp160. Although it is clear that adjuvant-activated DCs migrated mainly to draining lymph nodes, coculture with specific T cells and flow cytometry studies with DCs isolated from Peyer's patches after TCI suggested that activated DCs carrying skin-derived antigen also migrated from the skin to immune-inductive sites in gut mucosa and presented antigen directly to resident lymphocytes. These results and previous clinical trial results support the observation that TCI is a safe and effective strategy for inducing strong mucosal antibody and CTL responses.

A protective effect of epidermal powder immunization in a mouse model of equine herpesvirus-1 infection

To evaluate the protective effect of epidermal powder immunization (EPI) against equine herpesvirus-1 (EHV-1) infection, we prepared a powder vaccine in which formalin-inactivated virions were embedded in water-soluble, sugar-based particles. A PowderJect device was used to immunize mice with the powder vaccine via their abdominal skin. We found that twice-immunized mice were protected against challenge with the wild-type virus. This protective effect was equivalent to or better than that observed in mice immunized with other types of vaccines, including a gene gun-mediated DNA vaccine containing the glycoprotein D (gD) gene or conventional inactivated virus vaccines introduced via intramuscular or intranasal injections. These findings indicate that the powder vaccine is a promising approach for the immunological control of EHV-1 infection, either alone or as a part of prime-boost vaccination strategies.

Powder and particle-mediated approaches for delivery of DNA and protein vaccines into the epidermis

The epidermis of the skin is both a sensitive immune organ and a practical target site for vaccine administration. However, administration of vaccines into the epidermis is difficult to achieve using conventional vaccine delivery methods employing a needle and syringe. A needle-free vaccine delivery system has been developed that efficiently delivers powdered or particulate DNA and protein vaccines into the epidermal tissue. The delivery system can be used to directly transfect antigen presenting cells (APCs) by formulating DNA or protein vaccines onto gold particles (particle-mediated immunization). Antigen can be directly presented to the immune system by the transfected APCs. Antigen can also be expressed and secreted by transfected keratinocytes and picked up by resident APCs through the exogenous antigen presentation pathway. Alternatively, protein antigens can be formulated into a powder and delivered into the extracellular environment where they are picked up by APCs (epidermal powder immunization). Using any of these formulations, epidermal immunization offers the advantage of efficiently delivering vaccines into the APC-rich epidermis. Recent studies demonstrate that epidermal vaccine delivery induces humoral, cellular, and protective immune responses against infectious diseases in both laboratory animals and man.

Optimization of an alum-adsorbed vaccine powder formulation for epidermal powder immunization

PURPOSE

To develop stable and effective aluminum salt (alum)-adsorbed vaccine powder formulations for epidermal powder immunization (EPI) via a spray freeze-drying (SFD) process.

METHODS

Powder properties were determined using particle size analysis, tap density, and scanning electron microscopy. Alum coagulation was monitored via optical microscopy and particle sedimentation. Protein analysis was determined by the BCA protein assay, SDS-PAGE, and an enzyme immunoassay. In vivo immunogenicity and skin reactogenicity were performed on hairless guinea pigs and pigs, respectively.

RESULTS

SFD of hepatitis B surface antigen (HBsAg) adsorbed to aluminum hydroxide or aluminum phosphate using an excipient combination of trehalose/mannitol/dextran produced vaccine powders of dense particles and satisfactory powder flowability and hygroscopicity. This formulation also offered excellent long-term stability to the powder and the antigen. The two most important factors influencing alum particle coagulation are the freezing rate and the concentration of aluminum in the liquid formulation for SFD. The SFD vaccines, when delivered to hairless guinea pigs by EPI or injected intramuscularly after reconstitution, were as immunogenic as the original liquid vaccine. A further study showed that EPI with SFD alum-adsorbed diphtheria-tetanus toxoid vaccine was well tolerated, whereas needle injection of the liquid formulation caused persistent granuloma.

CONCLUSIONS

Stabilization of alum-adsorbed vaccine by SFD has important implications in extending vaccination to areas lacking a cold chain for transportation and storage and may also accelerate the development of new immunization technologies such as EPI.

Optimization of epicutaneous immunization for the induction of CTL

The immune system of the skin has recently been exploited for the development of non-invasive vaccine technologies. However, one of the limitations of current vaccine protocols is the inefficient priming of cytotoxic T lymphocytes (CTL). In this study, we report that the application of either an immunodominant class I MHC restricted ovalbumin peptide or whole ovalbumin protein, to tape-stripped skin together with the co-application of the bacterial enterotoxin cholera toxin (CT) induces antigen-specific CTL. Tape-stripping (TS) was found to enhance the magnitude of antibody responses to co-administered protein and to promote the generation of antigen-specific IgG(2a) responses. As well, both cholera toxin and tape-stripping enhanced epidermal dendritic cell (DC) immigration into draining lymph nodes. The adjuvant effect of co-administered cholera toxin and tape-stripping in promoting CTL priming was not dependent on IL-12. Epicutaneous immunization has previously been shown to induce robust antibody responses to administered protein antigen. We now demonstrate the induction of robust and persistent CTL responses to epicutaneously administered protein antigen. Epicutaneous immunization is cheap, simple and effective. These findings suggest the potential use of the skin for the generation of protective immune responses to both viral and tumor challenge.

Influenza hemagglutinin peptides fused to interferon gamma and encapsulated in liposomes protects mice against influenza infection

The immunogenicity of a peptide vaccine may be improved by fusing antigen to a cytokine and administering this chimeric protein in a particulate delivery system. We have investigated this using a vaccine comprising an immunodominant T cell epitope and a B cell epitope from influenza haemagglutinin (HATB) fused to interferon gamma and encapsulated in liposomes (HATB/IFN-gamma/lipo). Controls comprised groups receiving HATB/IFN-gamma mixed with liposomes, HATB incorporated in liposomes or heat inactivated PR8 influenza virus (HI PR8). IFN-gamma production in mice treated with HATB/IFN-gamma/lipo was significantly higher than in mice inoculated with either HATB/IFN-gamma mixed with liposomes or HATB incorporated in liposomes but less than HI PR8. Lung viral titres were significantly lower in mice treated with HATB/IFN-gamma/lipo compared with those treated with HATB/IFN-gamma mixed with liposomes. HI PR8-treated mice recorded a nil viral titre. There was no correlation between the level of antibody production and clearance of virus from the lungs. These data suggest that particulate delivery systems may be useful adjuncts to improve immune responses to chimeric proteins and to induce protection against disease.

Immune responses to hepatitis B surface antigen following epidermal powder immunization

Langerhans cells in the epidermis of skin are potent antigen-presenting cells that trigger the immune system to respond to invading microorganisms. We have previously shown that epidermal powder immunization with a powdered inactivated influenza virus vaccine, by targeting the Langerhans cell-rich epidermis, was more efficacious than deeper tissue injection using a needle and syringe. We now report enhanced humoral and cellular immune responses to recombinant hepatitis B surface antigen following epidermal powder immunization. We observed that epidermal powder immunization with unadjuvanted hepatitis B surface antigen elicited an antibody titre equivalent to that induced by the alum-adjuvanted vaccine delivered by intramuscular injection, suggesting that epidermal powder immunization can overcome the need for adjuvantation. We demonstrated that synthetic CpG oligonucleotides (CpG DNA) could be coformulated with hepatitis B surface antigen and delivered by epidermal powder immunization to further augment the antibody response and modulate T helper cell activities. Epidermal powder immunization of hepatitis B surface antigen formulated with CpG DNA formulations resulted in 1.5-2.0 logs higher IgG antibody titres than alum-adjuvanted commercial vaccines administered by intramuscular injection. Formulation of hepatitis B surface antigen with CpG DNA elicited an augmented IgG2a antibody response and increased frequency of IFN-gamma secreting cells. In addition, CpG DNA was found to activate epidermal Langerhans cells and stimulate the production of TNF-alpha and IL-12 cytokines by epidermal cells, explaining its strong adjuvant activity following epidermal powder immunization. These results show that epidermal powder immunization is a safe and effective method to deliver hepatitis B surface antigen and the addition of new adjuvants, such as CpG DNA, may further enhance the efficacy of this vaccine.

Enabling topical immunization via microporation: a novel method for pain-free and needle-free delivery of adenovirus-based vaccines

The skin represents an excellent site for vaccine inoculation due to its natural role as a first line of contact with foreign pathogens and the high local frequency of antigen presenting cells. To facilitate skin-directed immunization, a new technique has been developed (termed microporation) whereby a vaporization process is used to remove tiny areas of the stratum corneum creating microscopic pores that allow access to the underlying viable epidermis. Reporter gene expression was 100-fold increased following application of an adenovirus vector to microporated skin when compared to intact skin. Furthermore, 10-100-fold greater cellular and humoral immune responses were observed following topical administration of an adenovirus vaccine to microporated skin versus intact skin. Hairless mice responded to the microporated adenovirus vaccine equivalently to mice with normal hair follicle distribution demonstrating the activity of the microporated vaccine was not related to follicle count. In a tumor challenge model using a surrogate antigen, microporation increased vaccine efficacy by approximately 100-fold compared to intact skin. Finally, microporation enabled delivery of an adenovirus vaccine carrying a relevant melanoma antigen resulting in the development of auto-immune vitiligo and tumor protection. Thus, the microporation technology has proven to be a reliable and easy method to enable skin-directed vaccination.

Longitudinal analysis of the T-cell receptor (TCR)-VA and -VB repertoire in CD8+ T cells from individuals immunized with recombinant hepatitis B surface antigen

Recent studies have suggested that vaccination induces alterations in the T cell receptor (TCR) repertoire. We investigate the diversity of the TCR repertoire after immunization with a recombinant hepatitis B surface vaccine in seven healthy subjects in CD8+ T cells in peripheral blood lymphocytes. Cellular immune responses were monitored over time by sorting CD8 T cells followed by TCR-VA and -VB complementarity determining region 3 (CDR3) analysis. Frequency of individual VB families was determined by flow cytometry. TCR-VA/VB repertoires obtained from CD8+ T cells drawn after vaccination were compared to the TCR repertoire determined prior to vaccination. Monoclonal TCR transcripts could be detected exclusively in CD8+, but not in CD4+ T cells. Such monoclonal TCR transcripts were either stable in some individuals, or could only be detected at certain time points after vaccination. Sorting of monoclonal TCR-VB3+ T cells, which constituted up to 5% of the CD8+ T cell population from one individual, revealed that this T cell clone recognizes an epitope provided by the recombinant hepatitis B vaccine presented by MHC-class I on autologous antigen-presenting cells. Examination of the structural anatomy, defined by the TCR, and the frequency of T cells responding to the immunizing antigen may be helpful to provide surrogate markers to monitor cellular immune responses induced by protein antigens utilized for vaccination.

Epidermal powder immunization with a recombinant HIV gp120 targets Langerhans cells and induces enhanced immune responses

The recombinant envelope gp120 (rgp120) of human immunodeficiency virus (HIV) is a weak immunogen when administered by intramuscular (IM) injection. In the present study, we report that epidermal powder immunization (EPI) elicits robust antibody responses to the rgp120. EPI of mice with a dose 0.2-5 microg of rgp120 protein elicited geometric mean antibody titers that were 18- to 240-fold higher than that elicited by IM injection using a 5.0 microg dose. Targeting antigen to and mobilization of Langerhans cells (LCs) by EPI may explain the enhanced immunogenicity of the rgp120. EPI with rgp120 using sugar and gold particles as carrier resulted in differential antigen entry into the LCs and differential IgG subclass antibody and cellular immune responses. EPI may serve as a useful tool to evaluate vaccine potential of the rgp120 protein.

Epidermal powder immunization using non-toxic bacterial enterotoxin adjuvants with influenza vaccine augments protective immunity

The non-toxic B subunit of cholera toxin (CTB) and E. coli heat-labile toxin mutant proteins with reduced toxicity (LTR72) or no toxicity (LTK63) were used as adjuvants for epidermal powder immunization (EPI) with an influenza vaccine. When administered by EPI, CTB, LTR72 and LTK63 significantly augmented antibody responses to the influenza vaccine and protection against a lethal challenge in a mouse model. The antigen dose could be reduced by 125-fold. These adjuvants were well-tolerated both locally and systemically following EPI. These results suggest that EPI with influenza vaccine and a non-toxic bacterial enterotoxin hold promise for human vaccination.