Ensuring vaccine safety in immunization programmes--a WHO perspective

Maximizing doses from multi-dose vaccine vials using the air bubble trapping technique

Purpose

Vaccine shortages present significant challenges for public health, necessitating strategies such as fractional dosing and the use of adjuvants to conserve doses. However, reducing vaccine wastage remains essential. One approach is the air bubble trapping technique (ABTT), which involves trapping an air bubble to minimize dead volume loss and maximize the number of doses extracted from multi-dose vials.

Materials and Methods

This study compares ABTT with standard methods using 3 syringe types. Healthcare workers prepared 0.1 mL and 0.5 mL saline doses both with and without ABTT.

Results

Results showed that ABTT produced comparable vaccine volumes to conventional techniques but required extra preparation time. ABTT reduced volume by 8.6% for 0.1 mL doses and 2.9% for 0.5 mL doses, with preparation times of 30.63 and 32.95 seconds, compared to 12.53 and 15.11 seconds without ABTT.

Conclusion

ABTT was consistent across different syringe types and levels of user experience, allowing for practical integration into vaccination workflows.

Multi-dose vials versus single-dose vials for vaccination: perspectives from lower-middle income countries

The choice of the vaccine packaging type either as single- or multi-dose vial is a crucial determinant of vaccine coverage. The experience of vaccination strategies in lower-middle-income countries suggests that multi-dose vaccine vials translate into greater economic-logistic advantages due to lower packaging and storage costs with significant environmental benefits accrued from reduced medical waste generation. However, the use of multi-dose vials is associated with a theoretical risk of contamination particularly from human error. Moreover, the overall economic advantage of multi-dose vials is contingent on the reduction of the extent of vaccine wastage associated with their use. Robust data collection for monitoring of vaccine wastage rates and adverse effects following immunization is therefore needed to understand the extent of economic benefit and risks involved with multi-dose vial use.

Formulation-based approaches for dermal delivery of vaccines and therapeutic nucleic acids: Recent advances and future perspectives

A growing variety of biological macromolecules are in development for use as active ingredients in topical therapies and vaccines. Dermal delivery of biomacromolecules offers several advantages compared to other delivery methods, including improved targetability, reduced systemic toxicity, and decreased degradation of drugs. However, this route of delivery is hampered by the barrier function of the skin. Recently, a large body of research has been directed toward improving the delivery of macromolecules to the skin, ranging from nucleic acids (NAs) to antigens, using noninvasive means. In this review, we discuss the latest formulation-based efforts to deliver antigens and NAs for vaccination and treatment of skin diseases. We provide a perspective of their advantages, limitations, and potential for clinical translation. The delivery platforms discussed in this review may provide formulation scientists and clinicians with a better vision of the alternatives for dermal delivery of biomacromolecules, which may facilitate the development of new patient-friendly prophylactic and therapeutic medicines.

Heterologous vaccine regimen: Stakeholder acceptance and implementation considerations

Heterologous vaccine regimens deliver antigens through different vaccine components or vector types at sequential time points. Clinical development shows promising results and several candidates may be progressing to licensure in the coming years. This study aimed at exploring future acceptance and uptake of such regimens (also called heterologous prime-boost) and to identify implementation-associated benefits and challenges. Survey tools were developed based on findings from a previous literature search shared with the study team, and exploratory interviews with global stakeholders. An online survey and key informant interviews in six countries were conducted with stakeholders at national and sub-national level, including policy-makers, regulators and implementers. The interview guide and the online survey covered: (a) awareness of, and knowledge about, heterologous vaccine regimens; (b) rating of regimen-associated perceived benefits and challenges; (c) anticipation of possible challenges in relation to four hypothetical introduction scenarios; (d) potential acceptance benefits and challenges at the policy, health facility and recipient level. Sixty-two interviews were conducted at national level. The online survey was completed by 50 participants. Across the four introduction scenarios, respondents considered the highest potential for the introduction of heterologous regimens for immunoprophylaxis was among adolescents/adults for diseases against which no vaccines are currently available. Most reservations were related to logistics, record keeping, and recipient compliance. Adding a new heterologous vaccine regimen to the routine immunization calendar for children was considered feasible if it could generate an increased and longer-term immune response. Introduction in preparation of or following a disease outbreak was considered less favourably, with respondents stressing the difficulty of logistics in emergency situations, and the potential lag in the onset of protection. The recent approval of the first heterologous vaccine regimen for the prevention of Ebola Virus Disease will soon bring new light to the topic.

Vaccine hesitancy

In summer 2019 an extracurricular activity was started at the Medical University of Vienna (MUW) with the title: “Esoterism in Medicine”, where different chapters were evaluated by students. Here we present the subheading “Vaccine Hesitancy”. Three students formulated arguments from sceptic, hesitant or anti-vaccine groups and discussed the scientific literature to rebut it. Frequent objections were partly taken from the homepage of the German Robert-Koch-Institute, the home of the “Ständige Impfkommission”. Other objections were taken from blogs and social media. The students’ rebuttal was based on current scientific literature (preferentially pubmed), but also from other scientific sources like authorities.

Characterization of skin blebs from intradermal jet injection: Ex-vivo studies

This paper presents results from an ex-vivo study of intradermal jet injections, which is an attractive method to achieve both needle-free and fractional dose delivery of vaccines. Due to the fact that fluid properties of many novel therapeutics and vaccines can vary significantly, a key parameter for our study is the fluid viscosity, whilst the main focus is on determining the best correlation between the delivered volume and geometrical dimensions of the fluid deposit. For this we use a combination of top-view (skin wheal), underside (below the dermis), and cross-section (true skin bleb) perspectives and find that the top-view alone, as done in clinical practice, is insufficient to estimate the volume deposited in the dermis. Overall, the best correlation is found between the injection volume and cross-sectional diameter, however there is significant variation amongst the different fluids. For mean injection volumes of 60 μL the mean bleb diameter is ≈8 mm, with mean aspect ratio h¯/d=0.38, indicating the blebs are mostly oblate. However, the shape varies with viscosity and the higher viscosity does not spread laterally to the same degree as lower viscosity fluids. In addition, our high-speed video observations of the injection process, reveal some interesting dynamics of the jet injection method, and we modeled the bleb growth with an exponential saturation.

Characterization of jet injection efficiency with mouse cadavers

Needle-free drug delivery is highly sought after for reduction in sharps waste, prevention of needle-stick injuries, and potential for improved drug dispersion and uptake. Whilst there is a wealth of literature on the array of different delivery methods, jet injection is proposed as the sole candidate for delivery of viscous fluids, which is especially relevant with the advent of DNA-based vaccines. The focus of this study was therefore to assess the role of viscosity and jet configuration (i.e. stand-off relative to the skin) upon injection efficiency for a fixed spring-loaded system (Bioject ID Pen). We performed this assessment in the context of mouse cadavers and found that the dominant factor in determining success rates was the time from euthanasia, which was taken as a proxy for the stiffness of the underlying tissue. For overall injection efficiency, ANOVA tests indicated that stiffness was highly significant (P <  < 0.001), stand-off was moderately significant (P < 0.1), and viscosity was insignificant. In contrast, both viscosity and standoff were found to be significant (P < 0.01) when evaluating the percentage delivered intradermally. Using high-resolution micro-computed tomography (μ-CT), we also determined the depth and overall dispersion pattern immediately after injection.

Intranasal inactivated influenza vaccines for the prevention of seasonal influenza epidemics

INTRODUCTION

Intranasal influenza vaccines are expected to confer protection among vaccine recipients by successful induction of mucosal immune response in the upper respiratory tract. Though only live attenuated influenza virus vaccines (LAIVs) are licensed and available for intranasal use in humans today, intranasal inactivated influenza vaccines (IIVs) are currently under reconsideration as a promising intranasal influenza vaccine.

AREAS COVERED

This review addresses the history of intranasal IIV research and development, along with a summary of the studies done so far to address the mechanism of action of intranasal IIVs.

EXPERT COMMENTARY

From numerous in vitro and in vivo studies, it has been shown that intranasal IIVs can protect hosts from a broad spectrum of influenza virus strains. In-depth studies of the mucosal antibody response following intranasal IIV administration have also elucidated the detailed functions of secretory IgA (immunoglobulin A) antibodies which are responsible for the mechanism of action of intranasal vaccines. Safe and effective intranasal IIVs are expected to be an important tool to combat seasonal influenza.

Dual-chamber injection device for measles-rubella vaccine: The potential impact of introducing varying sizes of the devices in 3 countries

Introduction

By pairing diluent with vaccines, dual-chamber vaccine injection devices simplify the process of reconstituting vaccines before administration and thus decrease associated open vial wastage and adverse events. However, since these devices are larger than current vaccine vials for lyophilized vaccines, manufacturers need guidance as to how the size of these devices may affect vaccine distribution and delivery.

Methods

Using HERMES-generated immunization supply chain models of Benin, Bihar (India), and Mozambique, we replace the routine 10-dose measles-rubella (MR) lyophilized vaccine with single-dose MR dual-chamber injection devices, ranging the volume-per-dose (5.2–26 cm³) and price-per-dose ($0.70, $1.40).

Results

At a volume-per-dose of 5.2 cm³, a dual-chamber injection device results in similar vaccine availability, decreased open vial wastage (OVW), and similar total cost per dose administered as compared to baseline in moderately constrained supply chains. Between volumes of 7.5 cm³ and 26 cm³, these devices lead to a reduction in vaccine availability between 1% and 14% due to increases in cold chain storage utilization between 1% and 7% and increases in average peak transport utilization between 2% and 44%. At the highest volume-per-dose, 26 cm³, vaccine availability decreases between 9% and 14%. The total costs per dose administered varied between each scenario, as decreases in vaccine procurement costs were coupled with decreases in doses administered. However, introduction of a dual-chamber injection device only resulted in improved total cost per dose administered for Benin and Mozambique (at 5.2 cm³ and $0.70-per-dose) when the total number of doses administered changed <1% from baseline.

Conclusion

In 3 different country supply chains, a single-dose MR dual-chamber injection device would need to be no larger than 5.2 cm³ to not significantly impair the flow of other vaccines.

Nanotechnology: Revolutionizing the Science of Drug Delivery

Growing interest in the field of nanotechnology has led to its emergence in the field of medicine too. Nanomedicines encompass the various medical tools, diagnostic agents and the drug delivery vehicles being evolved with the advancements in the aura of nanotechnology. This review emphasizes on providing a cursory literature on the past events that led to the procession of nanomedicines, various novel drug delivery systems describing their structural features along with the pros and cons associated with them and the nanodrugs that made a move to the clinical practice. It also focuses on the need of the novel drug delivery systems and the challenges faced by the conventional drug delivery systems.

Intranasal Immunization Using Mannatide as a Novel Adjuvant for an Inactivated Influenza Vaccine and Its Adjuvant Effect Compared with MF59

Intranasal vaccination is more potent than parenteral injection for the prevention of influenza. However, because the poor efficiency of antigen uptake across the nasal mucosa is a key issue, immunostimulatory adjuvants are essential for intranasal vaccines. The immunomodulator mannatide or polyactin (PA) has been used for the clinical treatment of impaired immunity in China, but its adjuvant effect on an inactivated trivalent influenza vaccine (ITIV) via intranasal vaccination is unclear. To explore the adjuvant effect of PA, an inactivated trivalent influenza virus with or without PA or MF59 was instilled intranasally once a week in BALB/c mice. Humoral immunity was assessed by both the ELISA and hemagglutination inhibition (HI) methods using antigen-specific antibodies. Splenic lymphocyte proliferation and the IFN-γ level were measured to evaluate cell-mediated immunity. The post-vaccination serum HI antibody geometric mean titers (GMTs) for the H1N1 and H3N2 strains, antigen-specific serum IgG and IgA GMTs, mucosal SIgA GMT, splenic lymphocyte proliferation, and IFN-γ were significantly increased in the high-dose PA-adjuvanted vaccine group. The seroconversion rate and the mucosal response for the H3N2 strain were significantly elevated after high-dose PA administration. These adjuvant effects of high-dose PA for the influenza vaccine were comparable with those of the MF59 adjuvant, and abnormal signs or pathological changes were not found in the evaluated organs. In conclusion, PA is a novel mucosal adjuvant for intranasal vaccination with the ITIV that has safe and effective mucosal adjuvanticity in mice and successfully induces both serum and mucosal antibody responses and a cell-mediated response.

Intranasal co-delivery of IL-6 gene enhances the immunogenicity of anti-caries DNA vaccine

AIM

To investigate the effects of co-delivering IL-6 expressing plasmid pCI-IL-6 on the immunogenicity of the anti-caries DNA vaccine pCIA-P, which encodes the surface protein antigen PAc of Streptococcus mutans.

METHODS

Plasmid pCI-IL-6 was constructed by inserting the murine IL-6 gene into the pCI vector. Expression of IL-6 in vitro was assessed using Western blot analysis. BALB/c mice were intranasally co-immunized with pCIA-P plus pCI-IL-6 on d 0 and 14. Anti-PAc IgG and secretory IgA (sIgA) were assessed by ELISA. Splenocytes from the mice were re-stimulated with the PAc protein, and IFN-γ and IL-4 production was measured using ELISA. Splenocyte proliferation was analyzed with flow cytometry. Rats were similarly immunized, and dental caries scores were determined using the Keyes method.

RESULTS

Marked expression of IL-6 was found in COS-7 cells transfected with pCI-IL-6. In the pCI-IL-6 co-immunized mice, the specific IgG antibodies in serum and sIgA antibodies in saliva were significantly higher than those in the control mice at weeks 4 and 8. Moreover, the secretion of IFN-γ from splenocytes in response to re-stimulation with PAc protein was significantly higher in the pCI-IL-6 co-immunized mice than that in the control mice, whereas the secretion of IL-4 had no significant difference. The proliferation of splenocytes from the pCI-IL-6 co-immunized mice was significantly higher than that from the mice immunized with pCIA-P and pCI vector. In the rat caries model, the pCI-IL-6 co-immunization rats displayed lower caries scores than the control rats.

CONCLUSION

Intranasal co-delivery of IL-6 gene significantly enhances the immunogenicity of the anti-caries DNA vaccine.

Vaccine presentations and delivery technologies – what does the future hold?

There is an urgent need to change the presentations and delivery technologies of current vaccines. Until recently, these factors had not been key criteria in the selection of vaccines for program use. Recent and current changes in the field of vaccines and their delivery lead the authors to postulate that a major paradigm shift will take place over the next decade to revolutionize vaccine presentation and delivery in national immunization programs. The programmatic needs for certain vaccine presentations will increasingly dictate elements of vaccine development and manufacture. Over the next decade, an inexorable drift towards firstly, single-dose preparations, and secondly, delivery technologies other than the conventional needle and syringes is anticipated. A unified system capable of delivering multiple antigens as a single dose is urgently needed; however, changing the status quo of vaccine manufacture is not easy. The market predominantly produces vaccines delivered by needle and syringe. Profits for manufacturers from sales to developing countries are marginal at best, and there is little financial incentive to change. Global leaders will need to take bold decisions and begin demanding vaccines which have a presentation that lends them to safer, more practical delivery systems. If a strong enough case can be made to restructure the vaccine manufacturing industry, either through market forces, global bodies, such as the World Health Organization and the United Nations Children's Fund, or both, a dramatic change could be brought about that will make vaccine delivery simpler and safer. A globally coordinated approach to funding research and the introduction of a multiple-antigen, single-dose delivery system is urgently needed. The needs are clear, and this review argues that if the case is presented strongly enough, the resources will be found.

Epicutaneous Immunotherapy for Aeroallergen and Food Allergy

IgE-mediated allergies today affect up to 30 % of the population in industrialized countries. Allergen immunotherapy is the only disease-modifying treatment option with a long-term effect. However, very few patients (<5 %) choose immunotherapy, due to the long treatment duration (between 3-5 years) and possible local and systemic allergic side effects of the allergen administrations. The latter occur when an allergen accidentally reaches the blood circulation. Therefore, the ideal application route for allergen immunotherapy should be characterized by two hallmarks: firstly, by a high number of potent antigen-presenting cells, which enhance efficacy and thus shorten treatment duration. Secondly, the allergen administration site is ideally non-vascularized, so that inadvertent systemic distribution of the allergen and consequent systemic allergic side effects are minimized. The epidermis contains high numbers of potent antigen-presenting Langerhans cells and, as an epithelium, is non-vascularized. Therefore, the epidermis represents an interesting administration route. Historical evidence for the clinical efficacy of epicutaneous allergy immunotherapy (EPIT) has now been strengthened by a number of recent double-blinded placebo-controlled clinical trials performed by independent groups. We review the immunological rationale, history and clinical experience with epicutaneous allergy immunotherapy.

Intranasal vaccination with an inactivated whole influenza virus vaccine induces strong antibody responses in serum and nasal mucus of healthy adults

Haemagglutination inhibition (HI) and neutralization (NT) titers as well as haemagglutinin (HA) specific antibody responses were examined in 50 healthy adults aged between 22 and 69 y old after two intranasal administrations of an inactivated whole virus vaccine derived from A/Victoria/210/2009 virus (45 μg HA per dose) at 3 week intervals. Serum HI titers after two-doses of the nasal vaccine showed >2.5-fold rise in the ratio of geometric mean titer upon vaccination, >40% of subjects with a ≥4-fold increase in titer and >70% of subjects with a titer of ≥1:40, all parameters associated with an effective outcome of vaccination in the criteria defined by the European Medicines Agency. Serum neutralizing antibody responses correlated with HI antibody responses, although NT titers were about 2-fold higher than HI titers. These high levels of serum responses were accompanied by high levels of HI and neutralizing antibody responses in nasal mucus as measured in concentrated nasal wash samples that were about 10 times diluted compared with natural nasal mucus. Serum and nasal HI and neutralizing antibody responses consisted of HA-specific IgG and IgA antibody responses, with IgG and IgA antibodies being dominant in serum and nasal responses, respectively.

New directions in immunotherapy

Allergen immunotherapy (AIT) is effective in reducing the clinical symptoms associated with allergic rhinitis, asthma and venom-induced anaphylaxis. Subcutaneous (SCIT) and sublingual immunotherapy (SLIT) with unmodified allergen extracts are the most widely prescribed AIT regimens. The efficacy of these 2 routes appears comparable, but the safety profile with SLIT is more favorable allowing for home administration and requiring less patient time. However, both require that the treatment is taken regularly over several years, e.g., monthly in a supervised medical setting with SCIT and daily at home with SLIT. Despite the difference in treatment settings, poor adherence has been reported with both routes. Emerging evidence suggests that AIT may be effective in other allergic conditions such as atopic dermatitis, venom sting-induced large local reactions, and food allergy. Research with oral immunotherapy (OIT) for food allergies suggest that many patients can be desensitized during treatment, but questions remain about whether this can produce long term tolerance. Further studies are needed to identify appropriate patients and treatment regimens with these conditions. Efforts to develop safer and more effective AIT for inhalant allergies have led to investigations with modified allergens and alternate routes. Intralymphatic (ILIT) has been shown to produce long-lasting clinical benefits after three injections comparable to a 3-year course of SCIT. Epicutaneous (EPIT) has demonstrated promising results for food and inhalant allergies. Vaccine modifications, such as T cell epitopes or the use of viral-like particles as an adjuvant, have been shown to provide sustained clinical benefits after a relatively short course of treatment compared to the currently available AIT treatments, SLIT and SCIT. These newer approaches may increase the utilization and adherence to AIT because the multi-year treatment requirement of currently available AIT is a likely deterrent for initiating and adhering to treatment.

Transdermal immunization: biological framework and translational perspectives

INTRODUCTION

The renaissance in drug delivery research during the past decade led to several new approaches toward vaccine development. Transdermal immunization (TI) is a promising modality with both practical and immunological merits. Compared with conventional routes of administration, this needle-free delivery approach with ability to target the rich immunologically milieu of the skin provides a dual-edged benefit. It not only elicits an effective immune response in both systemic and mucosal compartments but has the potential to make vaccine delivery more equitable, safer and efficient.

AREAS COVERED

Over the years, numerous studies have explored physical, chemical and nanocarrier-based strategies to develop vaccines using this attractive route of delivery. The review provides insight into the various facets including research at interface that might drive novel basic scientific ideas to translational outcomes.

EXPERT OPINION

As we continue to develop TI as a vaccine delivery method, it is important to consider the practical application of this method and device strategies that best fit the public health needs. In the authors' view, nanoengineering-based approaches holds a great promise to overcome the associated challenges in TI and might help to translate early laboratory successes into the development of effective clinical prophylactics.

New routes for allergen immunotherapy

IgE-mediated allergy is a highly prevalent disease in the industrialized world. Allergen-specific immunotherapy (SIT) should be the preferred treatment, as it has long lasting protective effects and can stop the progression of the disease. However, few allergic patients choose to undergo SIT, due to the long treatment time and potential allergic adverse events. Since the beneficial effects of SIT are mediated by antigen presenting cells inducing Th1, Treg and antibody responses, whereas the adverse events are caused by mast cells and basophils, the therapeutic window of SIT may be widened by targeting tissues rich in antigen presenting cells. Lymph nodes and the epidermis contain high density of dendritic cells and low numbers of mast cells and basophils. The epidermis has the added benefit of not being vascularised thereby reducing the chances of anaphylactic shock due to leakage of allergen. Hence, both these tissues represent highly promising routes for SIT and are the focus of discussion in this review.

Transcutaneous immunization: an overview of advantages, disease targets, vaccines, and delivery technologies

Skin is an immunologically active tissue composed of specialized cells and agents that capture and process antigens to confer immune protection. Transcutaneous immunization takes advantage of the skin immune network by inducing a protective immune response against topically applied antigens. This mode of vaccination presents a novel and attractive approach for needle-free immunization that is safe, noninvasive, and overcomes many of the limitations associated with needle-based administrations. In this review we will discuss the developments in the field of transcutaneous immunization in the past decade with special emphasis on disease targets and vaccine delivery technologies. We will also briefly discuss the challenges that need to be overcome to translate early laboratory successes in transcutaneous immunization into the development of effective clinical prophylactics.

Cytokines: the future of intranasal vaccine adjuvants

Due to its potential as an effective, needle-free route of immunization for use with subunit vaccines, nasal immunization continues to be evaluated as a route of immunization in both research and clinical studies. However, as with other vaccination routes, subunit vaccines often require the addition of adjuvants to induce potent immune responses. Unfortunately, many commonly used experimental vaccine adjuvants, such as cholera toxin and E. coli heat-labile toxin, are too toxic for use in humans. Because new adjuvants are needed, cytokines have been evaluated for their ability to provide effective adjuvant activity when delivered by the nasal route in both animal models and in limited human studies. It is the purpose of this paper to discuss the potential of cytokines as nasal vaccine adjuvants.

Transcutaneous immunization as preventative and therapeutic regimens to protect against experimental otitis media due to nontypeable Haemophilus influenzae

We have developed three nontypeable Haemophilus influenzae (NTHI) adhesin-derived immunogens that are significantly efficacious against experimental otitis media (OM) due to NTHI when delivered parenterally. We now expanded our preventative immunization strategies to include transcutaneous immunization (TCI) as a less invasive, but potentially equally efficacious, regimen to prevent OM due to NTHI. Additionally, we examined the potential of TCI as a therapeutic immunization regimen to resolve ongoing experimental OM. Preventative immunization with NTHI outer membrane protein (OMP) P5- and type IV pilus-targeted immunogens, delivered with the adjuvant LT(R192G-L211A), induced significantly earlier clearance of NTHI from the nasopharynges and middle ears of challenged chinchillas compared with receipt of immunogen or adjuvant alone. Moreover, therapeutic immunization resulted in significant resolution of established NTHI biofilms from the middle ear space of animals compared with controls. These data advocate TCI with the adhesin-directed immunogens as an efficacious regimen for prevention and resolution of experimental NTHI-induced OM.

Epicutaneous allergen administration: is this the future of allergen-specific immunotherapy?

IgE-mediated allergies, such as allergic rhinoconjunctivitis and asthma, have become highly prevalent, today affecting up to 30% of the population in industrialized countries. Allergen-specific immunotherapy (SIT) either subcutaneously or via the sublingual route is effective, but only few patients (<5%) choose immunotherapy, as treatment takes several years and because allergen administrations are associated with local and, in some cases, even systemic allergic side-effects because of allergen accidentally reaching the circulation. In order to resolve these two major drawbacks, the ideal application site of SIT should have two characteristics. First, it should contain a high number of potent antigen-presenting cells to enhance efficacy and shorten treatment duration. Secondly, it should be nonvascularized in order to minimize inadvertent systemic distribution of the allergen and therefore systemic allergic side-effects. The epidermis, a nonvascularized multilayer epithelium, that contains high numbers of potent antigen-presenting Langerhans cells (LC) could therefore be an interesting administration route. The present review will discuss the immunological rational, history and actual clinical experience with epicutaneous allergen-specific immunotherapy.

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.

Mucosal targeting of a BoNT/A subunit vaccine adjuvanted with a mast cell activator enhances induction of BoNT/A neutralizing antibodies in rabbits

BACKGROUND

We previously reported that the immunogenicity of Hcβtre, a botulinum neurotoxin A (BoNT/A) immunogen, was enhanced by fusion to an epithelial cell binding domain, Ad2F, when nasally delivered to mice with cholera toxin (CT). This study was performed to determine if Ad2F would enhance the nasal immunogenicity of Hcβtre in rabbits, an animal model with a nasal cavity anatomy similar to humans. Since CT is not safe for human use, we also tested the adjuvant activity of compound 48/80 (C48/80), a mast cell activating compound previously determined to safely exhibit nasal adjuvant activity in mice.

METHODS

New Zealand White or Dutch Belted rabbits were nasally immunized with Hcβtre or Hcβtre-Ad2F alone or combined with CT or C48/80, and serum samples were tested for the presence of Hcβtre-specific binding (ELISA) or BoNT/A neutralizing antibodies.

RESULTS

Hcβtre-Ad2F nasally administered with CT induced serum anti-Hcβtre IgG ELISA and BoNT/A neutralizing antibody titers greater than those induced by Hcβtre + CT. C48/80 provided significant nasal adjuvant activity and induced BoNT/A-neutralizing antibodies similar to those induced by CT.

CONCLUSIONS

Ad2F enhanced the nasal immunogenicity of Hcβtre, and the mast cell activator C48/80 was an effective adjuvant for nasal immunization in rabbits, an animal model with a nasal cavity anatomy similar to that in humans.

Formulation, characterization and optimization of hepatitis B surface antigen (HBsAg)-loaded chitosan microspheres for oral delivery

CONTEXT

Approximately 400 million persons worldwide have chronic hepatitis B. This is due to problems associated with vaccine delivery, stability and cost. Hence the present challenge in vaccinology is to develop safer, cheaper and easy-to-deliver forms of vaccines. A novel needle-free oral vaccine will be an ideal tool to fight this silent killer disease.

OBJECTIVE

The aim of this work was to prepare and evaluate chitosan-loaded HBsAg microspheres for oral delivery.

MATERIALS AND METHODS

Chitosan microspheres were prepared by emulsion solvent evaporation technique. To overcome the enzymatic and permeation barrier, protease inhibitors and permeation enhancers were also added. Studies were conducted to find the effect of stabilizer concentration, stirring speed, cross-linking agent and polymer concentration on microsphere size and entrapment efficiency. Formulations were characterized for their particle size, entrapment efficiency. They were also evaluated for the in vitro drug release, in vivo performances and the effect of different storage conditions.

RESULTS

HBsAg-loaded chitosan microspheres with bacitracin as protease inhibitor showed better protective levels of immunity after oral administration comparing with aprotinin as protease inhibitor. Stability at room temperature up to a period of four months reduces incomplete vaccine coverage and logistic requirements.

CONCLUSION

The study signifies the potential of the formulated chitosan microspheres for effective oral administration of HBsAg.

Pediatric vaccination errors: application of the "5 rights" framework to a national error reporting database

Little is known about vaccination errors. We analyzed 607 outpatient pediatric vaccination error reports from MEDMARX, a nationwide, voluntary medication error reporting system, occurring from 2003 to 2006. We used the "5 Rights" framework (right vaccine, time, dose, route, and patient) to determine whether vaccination error types were predictable. We found that "wrong vaccine" errors were more common among look-alike/sound-alike groups than among vaccines with no look-alike/sound-alike group. Scheduled vaccines were more often involved in "wrong time" errors than seasonal and intermittent vaccines. "Wrong dose" errors were more common for vaccines whose dose is weight-based and age-based than for vaccines whose dose is uniform. "Wrong route" and "wrong patient" errors were rare. In this largest-ever analysis of pediatric vaccination errors, error types were associated with predictable vaccine-related human factors challenges. Efforts to reduce pediatric vaccination errors should focus on these human factors.

Nanoparticles for nasal vaccination

The great interest in mucosal vaccine delivery arises from the fact that mucosal surfaces represent the major site of entry for many pathogens. Among other mucosal sites, nasal delivery is especially attractive for immunization, as the nasal epithelium is characterized by relatively high permeability, low enzymatic activity and by the presence of an important number of immunocompetent cells. In addition to these advantageous characteristics, the nasal route could offer simplified and more cost-effective protocols for vaccination with improved patient compliance. The use of nanocarriers provides a suitable way for the nasal delivery of antigenic molecules. Besides improved protection and facilitated transport of the antigen, nanoparticulate delivery systems could also provide more effective antigen recognition by immune cells. These represent key factors in the optimal processing and presentation of the antigen, and therefore in the subsequent development of a suitable immune response. In this sense, the design of optimized vaccine nanocarriers offers a promising way for nasal mucosal vaccination.

Parents' vaccination comprehension and decisions

We report on 30 in-depth mental models interviews with parents discussing vaccination for their children, both in general terms and in response to communications drawn from sources supporting and opposing vaccines. We found that even parents favourable to vaccination can be confused by the ongoing debate, leading them to question their choices. Many parents lack basic knowledge of how vaccines work, and do not find the standard information provided to them to be particularly helpful in explaining it. Those with the greatest need to know about vaccination seem most vulnerable to confusing information. Opportunities for education may be missed if paediatricians do not appreciate parents' specific information needs.

Antigen co-encapsulated with adjuvants efficiently drive protective T cell immunity

Compared to "live" vaccines, the immunogenicity of "subunit" vaccines based on recombinant antigen (Ag) is poor, presumably because exogenous Ag fails to effectively access the endosomal Ag-processing pathways of Ag-presenting cells (APC). To overcome this limitation, we exploited biodegradable poly(lactic-co-glycolic) microspheres (MP) co-entrapping Ag and Toll-like receptor (TLR) 9 or 7 ligands as an endosomal delivery device. In vitro, microspheres were rapidly phagocytosed by APC and translocated into phago-endosomal compartments, followed by degradation of the Ag and concurrent activation of endosomal TLR. As a consequence, full maturation of and cytokine secretion by APC as well as Ag-cross-presentation ensued. In vivo, "loaded" microspheres triggered clonal expansion of primary and secondary Ag-specific CD4 and CD8 T cells. The efficacy of CD8 T cell cross-priming was comparable to that of live vectors. The potency of T cell vaccination was demonstrated by protective and therapeutic interventions using infection- and tumor-model systems. These preclinical "subunit" vaccination data thus recommend MP as a generally applicable and powerful endosomal delivery device of exogenous Ag plus TLR-based adjuvants to vaccinate for protective and therapeutic CD4 and CD8 T cell immunity.

Mannosylated niosomes as carrier adjuvant system for topical immunization

The aim of this study was to develop mannosylated niosomes as a topical vaccine delivery carrier and adjuvant for the induction of both humoral and cellular immunity. Bovine serum albumin (BSA)-loaded niosomes composed of sorbitan monostearate/sorbitan trioleate (Span 60/Span 85), cholesterol and stearylamine as constitutive lipids were prepared by the reverse-phase evaporation method. The niosomes were coated with a modified polysaccharide O-palmitoyl mannan (OPM) to target them to Langerhan's cells, the major antigen presenting cells found in abundance beneath the stratum corneum. Prepared niosomes were characterized in-vitro for their size, shape, entrapment efficiency and ligand binding specificity. The immune stimulating activity was studied by measuring serum IgG titre and its subclasses (IgG2a/IgG1 ratio) following topical application of various niosomal formulations in albino rats. The results were compared with alum-adsorbed BSA following topical application and intramuscular injection. It was observed that niosomal formulations elicited a significantly higher serum IgG titre upon topical application as compared with topically applied alum adsorbed BSA (P<0.05). The serum IgG levels were significantly higher for the mannosylated niosomes as compared with plain uncoated niosomes (P<0.05). All formulations displayed a combined serum IgG2a/IgG1 response, which suggested that the formulations were capable of eliciting both humoral and cellular responses. The study signified the potential of OPM-coated niosomes as a topical vaccine delivery carrier and adjuvant. The proposed system would be simple, stable, and cost effective and might be clinically acceptable.

Transcutaneous immunization in mice: Induction of T-helper and cytotoxic T lymphocyte responses and protection against human papillomavirus-induced tumors

Previous reports have shown that transcutaneous immunization (TCI) with proteins or peptides in combination with adjuvants efficiently induces specific cellular and humoral immune responses. However, depending on the kind of skin pretreatment, induction of cellular immune responses was restricted to generation of either specific cytotoxic T lymphocytes (CTLs) or T-helper (Th) cells. In this study, we induced antigen-specific CTL responses together with the appropriate Th responses by TCI of C57BL/6 mice. We applied ovalbumin protein or an ovalbumin-derived fusion peptide containing a CTL and Th epitope together with a combination of cholera toxin (CT) and CpG oligodeoxynucleotide (CpG) onto cold wax-depilated and hydrated bare skin. TCI with the ovalbumin fusion peptide induced more robust CTL and Th responses than that with ovalbumin protein. The fusion peptide in combination with the nontoxic CT derivative CTA1-D2D1 and CpG induced an antigen-specific CTL response, albeit less efficiently than in combination with complete CT. Further, we compared the potency of HPV-16 E7 oncoprotein-derived peptides containing single (CTL) or multiple (CTL + Th + B cell) epitopes to induce effective CTL responses. Strong E7-specific CTL responses were detected only after TCI with the E7 multiepitope peptide. This peptide was also shown to protect mice against tumor growth after challenge with HPV-16 E7-positive tumor cells. TCI with E7 protein and CT/CpG led to formation of an E7-specific humoral immune response.

Novel approaches to vaccine delivery

Although the currently available vaccines represent an outstanding success story in modern medicine and have had a dramatic effect on morbidity and mortality worldwide, it is clear that improvements are required in the current vaccine delivery technologies. Improvements are required to enable the successful development of vaccines against infectious diseases that have so far proven difficult to control with conventional approaches. Improvements may include the addition of novel injectable adjuvants or the use of novel routes of delivery, including mucosal immunization. Mucosal delivery may be required to provide protection against pathogens that infect at mucosal sites, including sexually transmitted diseases. Alternatively, novel approaches to delivery, including mucosal administration, may be used to improve compliance for existing vaccines. Of particular interest for safer mass immunization campaigns are needle-free delivery devices, which would avoid problems due to needle re-use in many parts of the world and would avoid needle-stick injuries.

The safety of vaccines

Vaccines have had a considerable impact on society by eliminating the threat from several infectious diseases. Although vaccines have generally proven to be safe, safety issues have arisen that have resulted in some members of the public having a poor perception of vaccines. However, the technological advances made in recent years make the development of even safer vaccines a possibility. The new generation of vaccines will be based on pure recombinant proteins, conjugates and killed viruses. In addition, studies can be conducted in large numbers of individuals to allay unjustified fears of vaccine safety. These data will increase public confidence and ensure that vaccines become better appreciated as valuable products. Widespread confidence will be inspired by the effective communication of the realities of the benefit-to-risk ratios for each vaccine.

Oral vaccination of mice with adenoviral vectors is not impaired by preexisting immunity to the vaccine carrier

Adenovirus vectors with E1 deleted of the human serotype 5 (AdHu5) and the chimpanzee serotype 68 (AdC68) expressing the glycoprotein of the Evelyn Rokiniki Abelseth strain of rabies virus were tested upon oral application for induction of systemic and mucosal transgene product-specific antibody responses in mice. Both vectors induced systemic and mucosal antibodies to rabies virus, including virus-neutralizing antibodies and protection against a severe intracerebral challenge with a mouse-adapted strain of rabies virus. Pre-existing immunity of AdHu5 virus, which dampens induction of transgene product-specific immunity elicited by AdHu5 vectors given systemically did not impair the response induced by oral vaccination. Oral priming-boosting regimens with either heterologous or homologous adenoviral vectors used sequentially increased both mucosal and systemic antibody titers to rabies virus [corrected]

Antigens onto bare skin: a 'painless' paradigm shift in vaccine delivery

The skin is an attractive route for delivery of vaccines because it is accessible and contains immunocompetent cells. This opens up the possibility that, in the future, vaccines could be administered in a simple, safe and practical way without requiring the use of needles and syringes. This review focuses on the methods developed to deliver vaccines via the intact skin. Candidate vaccine antigens can be delivered topically using particulate delivery systems and patch formulations containing the antigen with an ADP-ribosylating exotoxin as an adjuvant. The duration and type of elicited immune responses depend on the antigen, the adjuvant and the method of delivery. Already, the first clinical trial of transcutaneous delivery of vaccines has demonstrated the proof of the principle. However, despite these successes, there are several challenges ahead to be addressed before vaccines administered with a patch will be available over the counter.

Immunization safety priority project at the World Health Organization

In 1999, the World Health Organization's (WHO) Department of Vaccines and Biologicals launched the Immunization Safety Priority Project with the aim of establishing a comprehensive system to ensure the safety of all immunizations given in national immunization programs. Countries are the primary focus of the project. WHO has a role, not only because of its technical and normative role, but also because of its privileged relationship with country authorities and other partners, and its global vision and mandate. The four major areas of focus in the project are to (1) promote and coordinate research and development of safer and simpler delivery systems; (2) ensure vaccine safety, from vaccine development all the way through clinical trials and vaccine distribution until use; (3) broaden access to safer and more efficient systems for vaccine delivery and management of sharps waste; and (4) establish efficient mechanisms to detect serious or potentially serious adverse events following immunization, and enable prompt and effective response. The project emphasizes the importance of advocating safety and building capacity at national levels.

Ensuring injection safety during measles immunization campaigns: more than auto-disable syringes and safety boxes

Measles immunization campaigns are effective elements of a comprehensive strategy for preventing measles cases and deaths. However, if immunizations are not properly administered or if immunization waste products are not safely managed, there is the potential to transmit bloodborne pathogens (e.g., human immunodeficiency virus and hepatitis B and hepatitis C). A safe injection can be defined as one that results in no harm to the recipient, the vaccinator, and the surrounding community. Proper equipment, such as the exclusive use of auto-disable syringes and safety boxes, is necessary, but these alone are not sufficient to ensure injection safety in immunization campaigns. Equally important are careful planning and managerial activities that include policy and strategy development, financing, budgeting, logistics, training, supervision, and monitoring. The key elements that must be in place to ensure injection safety in measles immunization campaigns are outlined.