Nasal vaccines

Preparation and efficacy of a live newcastle disease virus vaccine encapsulated in chitosan nanoparticles

BACKGROUND

Newcastle disease (ND) is a highly contagious viral disease of poultry caused by pathogenic strains of the Newcastle disease virus (NDV). Live NDV vaccines are administered by drinking water, eyedrops or coarse aerosol spray. To further enhance mucosal immune responses, chitosan nanoparticles were developed for the mucosal delivery of a live NDV vaccine.

METHODOLOGY/PRINCIPAL FINDINGS

A lentogenic live-virus vaccine (strain LaSota) against NDV encapsulated in chitosan nanoparticles were developed using an ionic crosslinking method. Chitosan nanoparticles containing the lentogenic live-virus vaccine against NDV (NDV-CS-NPs) were produced with good morphology, high stability, a mean diameter of 371.1 nm, an encapsulation rate of 77% and a zeta potential of +2.84 mV. The Western blotting analysis showed that NDV structural proteins were detected in NDV-CS-NPs. The virus release assay results of NDV-CS-NPs indicated that NDV was released from NDV-CS-NPs. Chickens immunized orally or intranasally with NDV-CS-NPs were fully protected whereas one out of five chickens immunized with the LaSota live NDV vaccine and three out of five chickens immunized with the inactivated NDV vaccine were dead after challenge with the highly virulent NDV strain F48E9.

CONCLUSIONS/SIGNIFICANCE

NDV-CS-NPs induced better protection of immunized specific pathogen free chickens compared to the live NDV vaccine strain LaSota and the inactivated NDV vaccine. This study lays a foundation for the further development of mucosal vaccines and drugs encapsulated in chitosan nanoparticles.

Differential localization and function of antibody-forming cells responsive to inactivated or live-attenuated influenza virus vaccines

Currently, there are two different types of licensed influenza virus vaccines available in the USA, the live attenuated cold-adapted vaccine and the inactivated vaccine. Children greater than 2 years of age and adults younger than 50 years (apart from those suffering from immunodeficiencies or lung disease) may choose between the two vaccines. Previous studies have shown that both vaccines elicit significant serum antibody responses. However, comprehensive analyses of antibody-forming cells (AFCs) in the upper respiratory tract (URT), the critical site of pathogen entry, have been lacking. We therefore compared influenza virus-specific antibody and AFC activities in systemic and mucosal tissues following immunizations of cotton rats with inactivated or live-attenuated vaccines, including vaccines from the 2009-10 and 2010-11 seasons. Results demonstrated that inactivated and live-attenuated vaccines induced virus-specific AFCs, but patterns of residence and function were highly disparate. The inactivated vaccine elicited AFCs predominantly in the spleen and bone marrow; IgG was the main isotype. In contrast, the live attenuated vaccine elicited acute and long-sustained AFC responses in the diffuse nasal-associated lymphoid tissue (d-NALT) and lung, with IgA being the predominant isotype. The appearance of these d-NALT URT responses was confirmed by a similar study of the 2009-10 live attenuated vaccine in ferrets. Data emphasize that the inactivated and live-attenuated vaccines that are each capable of protecting humans from influenza virus disease do so by very different modes of immune surveillance.

Roles of Mucosal Immunity against Mycobacterium tuberculosis Infection

Mycobacterium tuberculosis (Mtb), the causative agent of tuberculosis (TB), is one of the world's leading infectious causes of morbidity and mortality. As a mucosal-transmitted pathogen, Mtb infects humans and animals mainly through the mucosal tissue of the respiratory tract. Apart from providing a physical barrier against the invasion of pathogen, the major function of the respiratory mucosa may be to serve as the inductive sites to initiate mucosal immune responses and sequentially provide the first line of defense for the host to defend against this pathogen. A large body of studies in the animals and humans have demonstrated that the mucosal immune system, rather than the systemic immune system, plays fundamental roles in the host's defense against Mtb infection. Therefore, the development of new vaccines and novel delivery routes capable of directly inducing respiratory mucosal immunity is emphasized for achieving enhanced protection from Mtb infection. In this paper, we outline the current state of knowledge regarding the mucosal immunity against Mtb infection, including the development of TB vaccines, and respiratory delivery routes to enhance mucosal immunity are discussed.

Preliminary studies on the development of IgA-loaded chitosan-dextran sulphate nanoparticles as a potential nasal delivery system for protein antigens

This study describes the development of a biodegradable nanoparticulate system for the intranasal delivery of multiple proteins. Chitosan (CS)-dextran sulphate (DS) nanoparticles were developed and optimised for the incorporation of pertussis toxin (PTX) and a potential targeting ligand (immunoglobulin-A, IgA). In vitro characterization and in vivo uptake studies were performed for the evaluation of developed nanoparticles. The ratio of CS to DS, the order of mixing and pH of nanoparticle suspension were identified as important formulation factors governing the size and zeta potential of nanoparticles. An optimised CS-DS nanoparticle formulation prepared with the CS to DS weight ratio of 3 : 1 was used to load PTX and/or IgA. Entrapment efficiency of >90% was obtained for both. The in vivo uptake of IgA-loaded CS-DS nanoparticles in mice showed a preferential uptake of nanoparticles probably by nasal membranous or microfold cells following intranasal administration. The results of this study indicate the potential application of IgA-loaded CS-DS nanoparticles as a nasal vaccine delivery system.

Vitamin A deficiency disrupts vaccine-induced antibody-forming cells and the balance of IgA/IgG isotypes in the upper and lower respiratory tract

Vaccination by intranasal (IN) inoculation with a replication-competent virus forms the basis of licensed and novel candidate respiratory viral vaccines (e.g., the cold-adapted influenza virus vaccine). A positive global impact of vaccination depends on vaccine efficacy in developing countries where dietary deficiencies are commonplace. The current study was designed using Sendai virus (SeV) as a model respiratory viral vaccine to test antibody-forming cell (AFC) residence and isotype expression in the context of a vitamin A deficiency (VAD). Samples were taken 1 mo after vaccination when AFCs generally reach their peak in healthy animals. In control animals on a healthy diet, SeV induced an antibody response with a relative bias toward IgA in the upper respiratory tract (URT, as sampled by nasal wash), and IgG in the lower respiratory tract (LRT, as sampled by bronchoalveolar lavage [BAL]). In the context of VAD, the SeV-specific IgA antibodies in the nasal wash were significantly reduced in favor of enhanced IgG antibodies in the BAL. When AFCs were examined in diffuse nasal-associated lymphoid tissues (d-NALT), lungs, cervical lymph nodes (CLN), and mediastinal lymph nodes (MLN), a similar pattern emerged. AFCs were most frequent in the d-NALT and most expressed IgA in control mice. In the context of VAD, these IgA-producing AFCs were significantly reduced in number, skewing the natural balance of IgA and IgG. Taken together, the results show that the VAD diet, which is well known for its association with immune defects in the gut, significantly alters AFC induction and isotype expression in the respiratory tract.

Heat shock proteins are therapeutic targets in autoimmune diseases and other chronic inflammatory conditions

INTRODUCTION

Exploitation of antigen-specific regulatory T cells (Tregs) as critical regulators in the control of chronic inflammatory diseases is hampered by the obscure nature of most disease-relevant autoantigens. Heat shock proteins (Hsp) are possible targets for Tregs due to their enhanced expression in inflamed (stressed) tissues and there is evidence that Hsp can induce anti-inflammatory immunoregulatory T-cell responses.

AREAS COVERED

Recent publications showing that exogenous administration of stress proteins has induced immunoregulation in various models of inflammatory disease have also been shown to be effective in first clinical trials in humans. Now, in the light of a growing interest in T-cell regulation, it is of interest to further explore the mechanisms through which Hsp can be utilized to trigger immunoregulatory pathways, capable of suppressing such a wide and diversified spectrum of inflammatory diseases.

EXPERT OPINION

Therapeutic approaches via exploitation of antigen-specific Tregs will benefit from tailor-made combination therapies. Combining current therapeutic approaches with Hsp-specific therapies thereby enhancing natural immune regulation might expedite the entry of antigen-specific regulatory T cells into the therapeutic arsenal of the anti-inflammatory therapeutics.

Strategies for intranasal delivery of vaccines

The vast majority of human pathogens colonize and invade at the mucosal surfaces. Preventing infection at these sites via mucosally active vaccines is a promising and rational approach for vaccine development. However, it is only recently that the stimulation of local immunity at the mucosal surfaces has become a primary objective in addition to inducing systemic immunity. This review describes vaccine formulations designed for mucosal delivery to the nasal-associated lymphoid tissue, via intranasal administration. The association of antigens with mucosal adjuvants and delivery systems is emphasised.

Intranasal immunization in mice with non-ionic surfactants vesicles containing HSV immunogens: a preliminary study as possible vaccine against genital herpes

The purpose of this study was to investigate the potential of intranasal immunization with non-ionic surfactant vesicles (NISV) containing either the secretory recombinant form of glycoprotein B (gBs) of herpes simplex virus type 1 or a related polylysine reach peptides (DTK) for induction of protective immunity against genital herpes infection in mice. NISV were prepared by lipid film hydration method. The mean diameter of vesicles was around 390 nm for DTK-containing NISV (DTK-NISV) and 320 nm for gB1s-containing NISV (gB1s-NISV). The encapsulation efficiency of the molecules was comprised between 57% and 70%. After 7-14 day NISV maintained stable dimensions and a drug encapsulation higher than 48%. We showed that intranasal immunization with gB1s-NISV induces gB-specific IgG antibody and lymphoproliferative responses, whereas vaccination with DTK-NISV was not able to generate a gB-specific immune response. Our results indicate that vaccination of BALB/c mice with gB1s-NISV induced Th1 responses, as characterized by increased titre of IG2a in plasma and IFN-production in CD4+ splenic cells. Intranasal immunization with gB1s-NISV could elicit 90% (almost complete) protection against a heterologous lethal vaginal challenge with herpes simplex virus type 2. These data may have implications for the development of a mucosal vaccine against genital herpes.

New pertussis vaccination approaches: en route to protect newborns?

Pertussis or whooping cough is a life-threatening childhood disease, particularly severe during the first months of life, although adolescent and adult pertussis is increasingly more noted. General vaccination has tremendously reduced its incidence but has failed to bring it completely under control. In fact, it remains one of the most poorly controlled vaccine-preventable diseases in the world. New vaccination strategies are thus being explored. These include vaccination of pregnant mothers to transmit protective antibodies to the offspring, a cocooning strategy to prevent the transmission of the disease from family members to the newborn and neonatal vaccination. All have their inherent limitations, and improved vaccines are urgently needed. Two types of pertussis vaccines are currently available, whole-cell, first-generation and second-generation, acellular vaccines, with an improved safety profile. Attempts have been made to discover additional protective antigens to the 1-5 currently included in the acellular vaccines or to include new adjuvants. Recently, a live attenuated nasal Bordetella pertussis vaccine has been developed and undergone first-in-man clinical trials. However, as promising as it may be, in order to protect infants against severe disease, a single approach may not be sufficient, and multiple strategies applied in a concerted fashion may ultimately be required.

Nicotine vaccines to assist with smoking cessation: current status of research

Tobacco smoking causes cardiovascular, respiratory and malignant disease, and stopping smoking is among the key medical interventions to lower the worldwide burden of these disorders. However, the addictive properties of cigarette smoking, including nicotine inhalation, render most quit attempts unsuccessful. Recommended therapies, including combinations of counselling and medication, produce long-term continuous abstinence rates of no more than 30%. Thus, more effective treatment options are needed.

An intriguing novel therapeutic concept is vaccination against nicotine. The basic principle of this approach is that, after entering the systemic circulation, a substantial proportion of nicotine can be bound by antibodies. Once bound to antibodies, nicotine is no longer able to cross the blood-brain barrier. As a consequence, the rewarding effects of nicotine are diminished, and relapse to smoking is less likely to occur. Animal studies indicate that antibodies profoundly change the pharmacokinetics of the drug and can interfere with nicotine self-administration and impact on the severity of withdrawal symptoms. To date, five phase I/II clinical trials using vaccines against nicotine have been published. Results have been disappointing in that an increase in quit rates was only observed in small groups of smokers displaying particularly high antibody titres.

The failure of encouraging preclinical data to completely translate to clinical studies may be partially explained by shortcomings of animal models of addiction and an incomplete understanding of the complex physiological and behavioural processes contributing to tobacco addiction. This review summarizes the current status of research and suggests some directions for the future development of vaccines against nicotine. Ideally, these vaccines could one day become part of a multifaceted approach to treating tobacco addiction that includes counselling and pharmacotherapy.

Mucosal vaccines to prevent porcine reproductive and respiratory syndrome: a new perspective

Porcine reproductive and respiratory syndrome (PRRS) is an economically important infectious disease of swine. Constant emergence of variant strains of PRRS virus (PPRSV) and virus-mediated immune evasion followed by viral persistence result in increased incidence and recurrence of PRRS in swine herds. Current live and killed PRRSV vaccines administered by a parenteral route are ineffective in inducing complete protection. Thus, new approaches in design and delivery of PRRSV vaccines are needed to reduce the disease burden of the swine industry. Induction of an effective mucosal immunity to several respiratory pathogens by direct delivery of a vaccine to mucosal sites has proven to be effective in a mouse model. However, there are challenges in eliciting mucosal immunity to PRRS due to our limited understanding of safe and potent mucosal adjuvants, which could potentiate the mucosal immune response to PRRSV. The purpose of this review is to discuss methods for induction of protective mucosal immune responses in the respiratory tract of pigs. The manuscript also discusses how PRRSV modulates innate, adaptive and immunoregulatory responses at both mucosal and systemic sites of infected and/or vaccinated pigs. This information may help in the design of innovative mucosal vaccines to elicit superior cross-protective immunity against divergent field strains of PRRSV.

Novel thermal-sensitive hydrogel enhances both humoral and cell-mediated immune responses by intranasal vaccine delivery

A novel thermal sensitive hydrogel was formulated with N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) and α, β-glycerophosphate (α, β-GP). A serial of hydrogels containing different amount of GP and HTCC with diverse quarternize degree (QD, 41%, 59%, 79.5%, and 99%) were prepared and characterized by rheological method. The hydrogel was subsequently evaluated for intranasal vaccine delivery with adenovirus based Zaire Ebola virus glycoprotein antigen (Ad-GPZ). Results showed that moderate quarternized HTCC (60% and 79.5%) hydrogel/antigen formulations induced highest IgG, IgG1, and IgG2a antibody titers in serum, as well as mucosal IgA responses in lung wash, which may attributed to the prolonged antigen residence time due to the thermal-sensitivity of this hydrogel. Furthermore, CD8(+) splenocytes for IFN-γ positive cell assay and the release profile of Th1/Th2 type cytokines (IFN-γ, IL-2, IL-10, and IL-4) showed that hydrogel/Ad-GPZ generated an overwhelmingly enhanced Th1 biased cellular immune response. In addition, this hydrogel displayed low toxicity to nasal tissue and epithelial cells even by frequently intranasal dosing of hydrogel. All these results strongly supported this hydrogel as a safe and effective delivery system for nasal immunization.

Reduced frequencies and heightened CD103 expression among virus-induced CD8(+) T cells in the respiratory tract airways of vitamin A-deficient mice

Vitamin A deficiency (VAD) has profound effects on immune responses in the gut, but its effect on other mucosal responses is less well understood. Sendai virus (SeV) is a candidate human parainfluenza virus type 1 (hPIV-1) vaccine and a candidate vaccine vector for other respiratory viruses. A single intranasal dose of SeV elicits a protective immune response against hPIV-1 within days after vaccination. To define the effect of VAD on acute responses toward SeV, we monitored both antibodies and CD8(+) T cells in mice. On day 10 following SeV infection, there was a trend toward lower antibody activities in the nasal washes of VAD mice than in those of controls, while bronchoalveolar lavage (BAL) fluid and serum antibodies were not reduced. In contrast, there was a dramatic reduction of immunodominant CD8(+) T cell frequencies in the lower respiratory tract (LRT) airways of VAD animals. These T cells also showed unusually high CD103 (the αE subunit of αEβ7) expression patterns. In both VAD and control mice, E-cadherin (the ligand for αEβ7) was better expressed among epithelial cells lining the upper respiratory tract (URT) than in LRT airways. The results support a working hypothesis that the high CD103 expression among T cell populations in VAD mice alters mechanisms of T cell cross talk with URT and LRT epithelial cells, thereby inhibiting T cell migration and egress into the lower airway. Our data emphasize that the consequences of VAD are not limited to gut-resident cells and characterize VAD influences on an immune response to a respiratory virus vaccine.

PLGA, PLGA-TMC and TMC-TPP nanoparticles differentially modulate the outcome of nasal vaccination by inducing tolerance or enhancing humoral immunity

Development of vaccines in autoimmune diseases has received wide attention over the last decade. However, many vaccines showed limited clinical efficacy. To enhance vaccine efficacy in infectious diseases, biocompatible and biodegradable polymeric nanoparticles have gained interest as antigen delivery systems. We investigated in mice whether antigen-encapsulated PLGA (poly-lactic-co-glycolic acid), PLGA-TMC (N-trimethyl chitosan) or TMC-TPP (tri-polyphosphate) nanoparticles can also be used to modulate the immunological outcome after nasal vaccination. These three nanoparticles enhanced the antigen presentation by dendritic cells, as shown by increased in vitro and in vivo CD4⁺ T-cell proliferation. However, only nasal PLGA nanoparticles were found to induce an immunoregulatory response as shown by enhanced Foxp3 expression in the nasopharynx associated lymphoid tissue and cervical lymph nodes. Nasal administration of OVA-containing PLGA particle resulted in functional suppression of an OVA-specific Th-1 mediated delayed-type hypersensitivity reaction, while TMC-TPP nanoparticles induced humoral immunity, which coincided with the enhanced generation of OVA-specific B-cells in the cervical lymph nodes. Intranasal treatment with Hsp70-mB29a peptide-loaded PLGA nanoparticles suppressed proteoglycan-induced arthritis, leading to a significant reduction of disease. We have uncovered a role for PLGA nanoparticles to enhance CD4⁺ T-cell mediated immunomodulation after nasal application. The exploitation of this differential regulation of nanoparticles to modulate nasal immune responses can lead to innovative vaccine development for prophylactic or therapeutic vaccination in infectious or autoimmune diseases.

Delivery of antigens used for vaccination: recent advances and challenges

Pasteur’s principle ‘isolate, inactivate, inject’ was the starting point for the successful development of many vaccines, but now, new ways for antigen discovery and vaccine administration present a challenge. Whereas vaccines against polio, measles and influenza are common for many parts of the world, the development of thermostable vaccines not being injected would ease vaccine distribution in developing countries. This review summarizes the general principles of vaccination and looks at common and novel vaccination targets. It also gives a rationale for using other routes than parenteral administration, such as mucosal or transdermal vaccination, and focuses on novel vaccination vehicles, as well as their formulation and stability aspects. Additionally, the review looks at novel application devices for the administration of vaccines.

Intranasal administration of an inactivated Yersinia pestis vaccine with interleukin-12 generates protective immunity against pneumonic plague

Inhalation of Yersinia pestis causes pneumonic plague, which rapidly progresses to death. A previously licensed killed whole-cell vaccine is presently unavailable due to its reactogenicity and inconclusive evidence of efficacy. The present study now shows that vaccination intranasally (i.n.) with inactivated Y. pestis CO92 (iYp) adjuvanted with interleukin-12 (IL-12) followed by an i.n. challenge with a lethal dose of Y. pestis CO92 prevented bacterial colonization and protected 100% of mice from pneumonic plague. Survival of the vaccinated mice correlated with levels of systemic and lung antibodies, reduced pulmonary pathology and proinflammatory cytokines, and the presence of lung lymphoid cell aggregates. Protection against pneumonic plague was partially dependent upon Fc receptors and could be transferred to naïve mice with immune mouse serum. On the other hand, protection was not dependent upon complement, and following vaccination, depletion of CD4 and/or CD8 T cells before challenge did not affect survival. In summary, the results demonstrate the safety, immunogenicity, and protective efficacy of i.n. administered iYp plus IL-12 in a mouse model of pneumonic plague.

Clonally related CD8+ T cells responsible for rapid population of both diffuse nasal-associated lymphoid tissue and lung after respiratory virus infection

The immune system has evolved to use sophisticated mechanisms to recruit lymphocytes to sites of pathogen exposure. Trafficking pathways are precise. For example, lymphocytes that are primed by gut pathogens can, in some cases, be imprinted with CCR9 membrane receptors, which can influence migration to the small intestine. Currently, little is known about T cell trafficking to the upper respiratory tract or the relationship between effectors that migrate to the diffuse nasal-associated lymphoid tissue (d-NALT), the lower airways, and the lung. To determine whether a T cell primed by Ag from a respiratory pathogen is imprinted for exclusive trafficking to the upper or lower respiratory tract or whether descendents from that cell have the capacity to migrate to both sites, we inoculated mice by the intranasal route with Sendai virus and conducted single-cell-sequencing analyses of CD8(+) T lymphocytes responsive to a K(b)-restricted immunodominant peptide, FAPGNYPAL (Tet(+)). Cells from the d-NALT, lung airways (bronchoalveolar lavage), lung, and mediastinal lymph node were examined 10 d postinfection to determine TCR usage and clonal relationships. We discovered that 1) Tet(+) cells were heterogeneous but preferentially used TCR elements TRAV6, TRAV16, and TRBD1; 2) both N and C termini of Vα and Vβ TCR junctions frequently encompassed charged residues, perhaps facilitating TCR αβ pairing and interactions with a neutral target peptide; and 3) T cells in the d-NALT were often clonally related to cells in the lower respiratory tract.

Surfactant protein C is an essential constituent for mucosal adjuvanticity of Surfacten, acting as an antigen delivery vehicle and inducing both local and systemic immunity

We have reported that Surfacten(®) (St), a bovine pulmonary surfactant free of antigenic c-type lectins, is a useful mucosal adjuvant for nasal vaccination. To prepare ample supplies a synthetic adjuvant that mimics St, we analyzed essential constituents of St for mucosal adjuvanticity. Intranasal inoculation of influenza virus hemagglutinin (HA) vaccine combined with St free of surfactant protein (SP)-C resulted in failure of HA vaccine delivery to dendritic cells and loss of local and systemic immune responses. Naïve bovine SP-C, synthetic human or bovine SP-C peptide reconstituted with three major St lipids restored delivery activity and local and systemic immune responses to levels similar to those of St and provided almost complete protection against lethal doses of influenza virus challenge in mice. The delivery of fluoresceinated HA vaccine to cultured dendritic cells was significantly enhanced by co-administration of St or synthetic adjuvant, and moderately stimulated the expression of MHC class II and CD86. In addition, both St and synthetic adjuvant markedly sustained HA vaccine and achieved a wide antigen distribution in murine nasal cavity. These results suggest that synthetic mucosal adjuvant reconstituted with SP-C peptide and major St lipids is useful for ample supply of the potent mucosal adjuvant as an antigen delivery vehicle for intranasal vaccination.

Intranasal delivery of Norwalk virus-like particles formulated in an in situ gelling, dry powder vaccine

The development of a vaccine to prevent norovirus infections has been focused on immunization at a mucosal surface, but has been limited by the low immunogenicity of self-assembling Norwalk virus-like particles (NV VLPs) delivered enterically or at nasal surfaces. Nasal immunization, which offers the advantage of ease of immunization, faces obstacles imposed by the normal process of mucociliary clearance, which limits residence time of applied antigens. Herein, we describe the use of a dry powder formulation (GelVac) of an inert in situ gelling polysaccharide (GelSite) extracted from Aloe vera for nasal delivery of NV VLP antigen. Powder formulations, with or without NV VLP antigen, were similar in structure in dry form or when rehydrated in simulated nasal fluids. Immunogenicity of the dry powder VLP formulation was compared to equivalent antigen/adjuvant liquid formulations in animals. For the GelVac powder, we observed superior NV-specific serum and mucosal (aerodigestive and reproductive tracts) antibody responses relative to liquid formulations. Incorporation of the TLR7 agonist gardiquimod in dry powder formulations did not enhance antibody responses, although its inclusion in liquid formulations did enhance VLP immunogenicity irrespective of the presence or absence of GelSite. We interpret these data as showing that GelSite-based dry powder formulations (1) stabilize the immunogenic structural properties of VLPs and (2) induce systemic and mucosal antibody titers which are equal or greater than those achieved by VLPs plus adjuvant in a liquid formulation. We conclude that in situ gelation of the GelVac dry powder formulation at nasal mucosal surfaces delays mucociliary clearance and thereby prolongs VLP antigen exposure to immune effector sites.

Vaccination against nicotine alters the distribution of nicotine delivered via cigarette smoke inhalation to rats

Preclinical models of nicotine vaccine pharmacology have relied on i.v. or s.c. administration of nicotine. Models using cigarette smoke inhalation might more accurately simulate nicotine exposure in smokers. Nicotine vaccine effects were examined in rats using two cigarette smoke exposure models: a 10 min nose-only exposure (NSE) producing serum nicotine levels equivalent to the nicotine boost from 1 cigarette in a smoker, and a 2h whole-body exposure (WBE) producing serum nicotine levels similar to those associated with regular mid-day smoking. Vaccination prior to 10min smoke NSE reduced nicotine distribution to brain by 90%, comparable to its effect on nicotine administered i.v. Vaccination prior to 2 h smoke WBE reduced nicotine distribution to brain by 35%. The nicotine concentration in broncheoalveolar lavage (BAL) fluid obtained after 2 h WBE was increased by 230% in vaccinated rats but was also increased in rats passively immunized with a nicotine-specific monoclonal antibody, and so was likely due to transfer of antibody from serum rather than local production at the pulmonary mucosa. Nicotine-specific IgA was not detectable in BAL fluid, but titers in serum were appreciable at 21-25% of the IgG titer and could contribute to vaccine efficacy. Both vaccination and passive immunization are effective in reducing nicotine distribution to brain in rats when nicotine is delivered via inhaled cigarette smoke. These data validate results previously obtained in rodents for nicotine vaccines using i.v. or s.c. nicotine dosing and provide a quantitative method for studying aspects of nicotine exposure which are unique to cigarette smoke inhalation.

Single shot tetanus vaccine manufactured by a supercritical fluid encapsulation technology

Single shot vaccines of tetanus toxoid (TT) were manufactured using the NanoMix process - a low temperature solvent free encapsulation technology using supercritical fluids. The formulations were injected into mice, and compared to multiple injections of a commercially available alum adsorbed TT vaccine. After 5 months the antibody titres were found to be similar for both the alum adsorbed and microparticle formulations, demonstrating for the first time the potential of formulating antigens in PLA microparticles using the supercritical fluid (NanoMix) technique to produce single shot vaccines. The results are likely to be due to the maintenance of toxoid bioactivity and some degree of sustained release of the encapsulated antigens, resulting in repeated stimulation of antigen presenting cells eliminating the need for multiple immunisations. This demonstrates the potential of this supercritical fluid processing technique to reduce the need for booster doses in a vaccine regimen.

Passive immunoprotection targeting a secreted CAMP factor of Propionibacterium acnes as a novel immunotherapeutic for acne vulgaris

Propionibacterium acnes (P. acnes) bacteria play a key role in the pathogenesis of acne vulgaris. Although our previous studies have demonstrated that vaccines targeting a surface sialidase or bacterial particles exhibit a preventive effect against P. acnes, the lack of therapeutic activities and incapability of neutralizing secretory virulence factors motivate us to generate novel immunotherapeutics. In this study, we develop an immunotherapeutic antibody to secretory Christie-Atkins-Munch-Peterson (CAMP) factor of P. acnes. Via agroinfiltration, P. acnes CAMP factor was encapsulated into the leaves of radishes. ICR mice intranasally immunized with whole leaves expressing CAMP factor successfully produced neutralizing antibodies that efficiently attenuated P. acnes-induced ear swelling and production of macrophage-inflammatory protein-2. Passive neutralization of CAMP factor enhanced immunity to eradicate P. acnes at the infection site without influencing bacterial growth elsewhere. We propose that CAMP factor is a novel therapeutic target for the treatment of various P. acnes-associated diseases and highlight the concept of neutralizing P. acnes virulence without disturbing the bacterial commensalism in human microbiome.

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.

Phenotypes and functions of persistent Sendai virus-induced antibody forming cells and CD8+ T cells in diffuse nasal-associated lymphoid tissue typify lymphocyte responses of the gut

Lymphocytes of the diffuse nasal-associated lymphoid tissue (d-NALT) are uniquely positioned to tackle respiratory pathogens at their point-of-entry, yet are rarely examined after intranasal (i.n.) vaccinations or infections. Here we evaluate an i.n. inoculation with Sendai virus (SeV) for elicitation of virus-specific antibody forming cells (AFCs) and CD8(+) T cells in the d-NALT. Virus-specific AFCs and CD8(+) T cells each appeared by day 7 after SeV inoculation and persisted for 8 months, explaining the long-sustained protection against respiratory virus challenge conferred by this vaccine. AFCs produced IgM, IgG1, IgG2a, IgG2b and IgA, while CD8+ T cells were cytolytic and produced low levels of cytokines. Phenotypic analyses of virus-specific T cells revealed striking similarities with pathogen-specific immune responses in the intestine, highlighting some key features of adaptive immunity at a mucosal site.

Dry powder vaccines for mucosal administration: critical factors in manufacture and delivery

Dry powder vaccine formulations have proved effective for induction of systemic and mucosal immune responses. Here we review the use of dry vaccines for immunization in the respiratory tract. We discuss techniques for powder formulation, manufacture, characterization and delivery in addition to methods used for evaluation of stability and safety. We review the immunogenicity and protective efficacy of dry powder vaccines as compared to liquid vaccines delivered by mucosal or parenteral routes. Included is information on mucosal adjuvants and mucoadhesives that can be used to enhance nasal or pulmonary dry vaccines. Mucosal immunization with dry powder vaccines offers the potential to provide a needle-free and cold chain-independent vaccination strategy for the induction of protective immunity against either systemic or mucosal pathogens.

Characterization of immune responses following intranasal immunization with the Mycobacterium bovis CFP-10 protein expressed by attenuated Salmonella typhimurium

Culture filtrate protein 10 (CFP-10) from Mycobacterium bovis or Mycobacterium tuberculosis (MTB) is an immunodominant T-cell antigen expressed during the early stages of infection. Because lungs are most commonly associated with primary M. bovis infections, specific immunity at this site is desirable for protection. Therefore, in this study, immune responses generated in mouse lung, spleen and Peyer's patches were examined following intranasal (i.n.) immunization with Salmonella typhimurium- expressing CFP-10. Cells harvested from the lungs and Peyer's patches of immunized mice and then stimulated with CFP-10 produced significant levels of IFN-γ and these mice developed elevated serum IgG and lung IgA anti-CFP-10 responses, suggesting that this approach induced potent anti-CFP-10 mucosal immunity. Our study demonstrates that i.n. administration of CFP-10 expressed by S. typhimurium represents an effective way to induce efficient immune response to M. bovis antigen.

Liposomes as delivery systems for nasal vaccination: strategies and outcomes

IMPORTANCE OF THE FIELD

Among the particulate systems that have been envisaged in vaccine delivery, liposomes are very attractive. These phospholipid vesicles can indeed deliver a wide range of molecules. They have been shown to enhance considerably the immunogenicity of weak protein antigens or synthetic peptides. Also, they offer a wide range of pharmaceutical options for the design of vaccines. In the past decade, the nasal mucosa has emerged as an effective route for vaccine delivery, together with the opportunity to develop non-invasive approaches in vaccination.

AREAS COVERED IN THIS REVIEW

This review focuses on the recent strategies and outcomes that have been developed around the use of liposomes in nasal vaccination.

WHAT THE READER WILL GAIN

The various formulation parameters, including lipid composition, size, charge and mucoadhesiveness, that have been investigated in the design of liposomal vaccine candidates dedicated to nasal vaccination are outlined. Also, an overview of the immunological and protective responses obtained with the developed formulations is presented.

TAKE HOME MESSAGE

This review illustrates the high potential of liposomes as nasal vaccine delivery systems.

Probing local innate immune responses after mucosal immunisation

Background

Intranasal immunisation is potentially a very effective route for inducing both mucosal and systemic immunity to an infectious agent.

Methods

Balb/c mice were intranasally immunised with the mucosal adjuvant heat labile toxin and the Mycobacterium tuberculosis fusion protein Ag85B-ESAT6 and early changes in innate immune responses within local mucosal tissues were examined using flow cytometry and confocal microscopy. Antigen-specific humoral and cellular immune responses were also evaluated.

Results

Intranasal immunisation induced significant changes in both number and distribution of dendritic cells, macrophages and neutrophils within the nasal-associated lymphoid tissue and cervical lymph nodes in comparison to controls as early as 5 h post immunisation. Immunisation also resulted in a rapid and transient increase in activation marker expression first in the nasal-associated lymphoid tissue, and then in the cervical lymph nodes. This heightened activation status was also apparent from the pro-inflammatory cytokine profiles of these innate populations. In addition we also showed increased expression and distribution of a number of different cell adhesion molecules early after intranasal immunisation within these lymphoid tissues. These observed early changes correlated with the induction of a T_H1 type immune response.

Conclusions

These data provide insights into the complex nature of innate immune responses induced following intranasal immunisation within the upper respiratory tract, and may help clarify the concepts and provide the tools that are needed to exploit the full potential of mucosal vaccines.

Advances in effective vaccine development against hepatitis B: focus on mucosal vaccine delivery strategies

Hepatitis B virus causes chronic necroinflammatory liver disease, which is known as hepatitis B. This inflammatory condition may further aggravate liver cirrhosis or hepatocellular carcinoma. Currently available conventional hepatitis B vaccine contains one of the viral envelope proteins, hepatitis B surface antigen, which develops a humoral immune response and hence protects against the infection. However, it fails in developing the desired cellular immune response, which is one of the most important bioresponses contributing to virus elimination from infected hepatocytes. At the same time, moderate humoral response developed following conventional vaccination do not protect the mucosal surfaces through serosal response. The mucosa is a predominant entry site for most of the infectious pathogens. Several strategies, including the use of adjuvants, development of surface functionalized novel antigen carriers and mucosal immunization for example, have been explored to investigate their role in addressing the limitations associated with the current hepatitis B vaccine. This review focuses on recent advances that have been made in order to develop an effective vaccine against hepatitis B.

Investigation of lectinized liposomes as M-cell targeted carrier-adjuvant for mucosal immunization

In the present investigation hepatitis B surface antigen (HBsAg) encapsulated liposomes were developed and coupled with Ulex europaeus agglutinin 1 (UEA-1) to increase transmucosal uptake by M-cells of the Peyer's patches. The liposomes were characterized for shape, size, polydispersity and encapsulation efficiency. Bovine submaxillary mucin (BSM) was used as a biological model for the in vitro determination of lectin activity and specificity. Dual staining technique was used to investigate targeting of lectinized liposomes to the M-cells. Anti-HBsAg IgG response in serum and anti-HBsAg sIgA level in various mucosal fluids was estimated by using ELISA, following oral immunization with lectinized and non-lectinized liposomes in Balb/c mice. Additionally, interleukin-2 (IL-2) and interferon-γ (IFN-γ) level in the spleen homogenates was determined. The results suggest that lectinized liposomes were successfully developed, exhibited increased activity with BSM as compared to non-lectinized liposomes and α-l-fucose specificity of the lectinized liposomes was also maintained. The lectinized liposomes were predominantly targeted to the M-cells. The serum anti-HBsAg IgG titre obtained after 3 consecutive days oral immunizations with HBsAg encapsulated lectinized liposomes and boosting after third week was comparable with the titre recorded after single intramuscular prime and third week boosting with alum-HBsAg. Moreover, lectinized liposomes induced higher sIgA level in mucosal secretions and cytokines level in the spleen homogenates. The results showed that the developed surface modified liposomes could be a potential module for the development of effective mucosal vaccines.

Robust IgA and IgG-producing antibody forming cells in the diffuse-NALT and lungs of Sendai virus-vaccinated cotton rats associate with rapid protection against human parainfluenza virus-type 1

Sendai virus (SeV), a natural mouse pathogen, shows considerable promise as a candidate vaccine for human parainfluenza virus-type 1 (hPIV-1), and also as a vaccine vector for other serious pathogens of infants including respiratory syncytial virus (RSV). In an effort to define correlates of immunity, we examined the virus-specific serum antibody of cotton rats inoculated intranasally (I.N.) with SeV. Virus-specific antibody forming cells (AFCs) were also measured in the bone marrow, because these are considered responsible for durable serum antibody levels in other viral systems. Results showed that a single SeV inoculation was sufficient to induce virus-specific serum antibodies and bone marrow-resident AFCs that persisted for as many as 8 months post-vaccination. Given that the predominant SeV-specific serum antibody isotype was IgG, an isotype that traffics poorly to the upper respiratory tract (URT), we asked if local nasal and lung-associated antibodies and AFCs were also present. Studies showed that: (i) SeV-specific antibodies appeared in the URT and lower respiratory tract (LRT) within 7 days after immunization, (ii) corresponding AFCs were present in the diffuse-NALT (d-NALT) and lung, (iii) AFCs in the d-NALT and lung peaked at approximately 6 weeks and persisted for the lifetime of the animal, reaching a level exceeding that of the bone marrow by an order of magnitude, (iv) IgA was the dominant isotype among AFCs in the d-NALT and lung at 4-weeks post-vaccination and thereafter, and (v) antibody and AFC responses associated with the prevention of lung infection when animals were challenged with hPIV-1 just 1 week after vaccination.

Safety and immunogenicity of a Shigella flexneri 2a Invaplex 50 intranasal vaccine in adult volunteers

Shigellosis is a leading cause of diarrhea worldwide prompting vaccine development. The Shigella flexneri Invaplex 50 is a macromolecular complex containing IpaB, IpaC, and LPS, formulated from an aqueous extract of virulent Shigella delivered via nasal administration. Preclinical vaccine testing demonstrated safety, immunogenicity and efficacy. An open-label dose-escalating phase 1 study evaluated a 3-dose (2-week intervals) regimen via nasal pipette delivery. Thirty-two subjects were enrolled into one of four vaccine dose groups (10, 50, 240, or 480 microg). The vaccine was well tolerated with minor short-lived nasal symptoms without evidence of dose effect. Antibody-secreting cell (ASC) responses were elicited at doses > or =50 microg with the highest IgG ASC, Invaplex 50 (100%) and S. flexneri 2a LPS (71%), as well as, serologic responses (43%) occurring with the 240 microg dose. Fecal IgA responses, Invaplex 50 (38.5%) and LPS (30.8%), were observed at doses > or =240 microg. The Invaplex 50 nasal vaccine was safe with encouraging mucosal immune responses. Follow-on studies will optimize dose, delivery mechanism and assess efficacy in a S. flexneri 2a challenge study.

NK cells influence both innate and adaptive immune responses after mucosal immunization with antigen and mucosal adjuvant

NK cells were found to be recruited in a temporally controlled manner to the nasal-associated lymphoid tissue and the cervical lymph nodes of mice after intranasal immunization with Ag85B-early secreted antigenic target 6 kDa from Mycobacterium tuberculosis mixed with Escherichia coli heat-labile toxin as adjuvant. These NK cells were activated and secreted a diverse range of cytokines and other immunomodulators. Using Ab depletion targeting anti-asialo GM1, we found evidence for altered trafficking, impaired activation, and cytokine secretion of dendritic cells, macrophages, and neutrophils in immunized NK cell-depleted mice compared with control animals. Analysis of Ag-specific immune responses revealed an attenuated Ab and cytokine response in immunized NK cell-depleted animals. Systemic administration of rIL-6 but not rIFN-gamma significantly restored immune responses in mice depleted of NK cells. In conclusion, cytokine production, particularly IL-6, via NK cells and NK cell-activated immune populations plays an important role in the establishment of local innate immune responses and the consequent development of adaptive immunity after mucosal immunization.

Improved Immunogenicity of Biodegradable Polymer Particles Entrapped Rotavirus Vaccine

Rotavirus (RV) entrapped in polylactide (PLA) and polylactide-coglycolide (PLGA) polymer particles were formulated and evaluated in mice for improved immunogenicity using oral, intranasal (IN), and intramuscular (IM) routes of administration. Microparticles of size ranges between 1 and 8 µm were prepared using double emulsion solvent evaporation technique. Stabilizers like mouse serum albumin, sucrose, and sodium bicarbonate that were used during particle formulation helped in minimizing the denaturation of the entrapped antigen. Immunization with 20 µg of antigen entrapped in polymeric particles through various routes of administration elicited measurable amount of antibody titer in mice. The immunoglobulin A (IgA) and immunoglobulin G (IgG) titer (≥4-fold rise between pre and post immunized sera) was analyzed by the use of enzyme-linked immunosorbent assay. PLGA encapsulated RV microparticles elicited better antibody response through IN route (90%) where as PLA encapsulated RV microparticles showed improved response when administrated through oral route (83.3%). Overall, the performance of IN route based immunization was significantly higher than oral and IM route ( p<0.001) with both the polymers. The results are of indication that, PLGA encapsulated RV microparticles have greater potential for vaccine formulation to combat rotavirus infection.

Perspectives for the development of human papillomavirus vaccines and immunotherapy

Human papillomavirus (HPV) is the most common sexually transmitted infection and is responsible for 90-99% of cervical cancer (CxCa) cases. Although effective screening programs have reduced the incidence of CxCa in developed countries, they are often not well organized. Prophylactic vaccination against HPV seems to be a good strategy for the prevention of CxCa. However, because millions of women are already infected with HPV, therapeutic HPV vaccines need to be developed further to treat these women. This review discusses the actual perspectives on both HPV vaccines and immunotherapy worldwide. In addition, some of the perspectives in France are also briefly discussed.

Chitosan-based delivery systems for protein therapeutics and antigens

Therapeutic peptides/proteins and protein-based antigens are chemically and structurally labile compounds, which are almost exclusively administered by parenteral injections. Recently, non-invasive mucosal routes have attracted interest for administration of these biotherapeutics. Chitosan-based delivery systems enhance the absorption and/or cellular uptake of peptides/proteins across mucosal sites and have immunoadjuvant properties. Chitosan is a mucoadhesive polysaccharide capable of opening the tight junctions between epithelial cells and it has functional groups for chemical modifications, which has resulted in a large variety of chitosan derivatives with tunable properties for the aimed applications. This review provides an overview of chitosan-based polymers for preparation of both therapeutic peptides/protein and antigen formulations. The physicochemical properties of these carrier systems as well as their applications in protein and antigen delivery through parenteral and mucosal (particularly nasal and pulmonary) administrations are summarized and discussed.

Modulation of protective immunity against herpes simplex virus via mucosal genetic co-transfer of DNA vaccine with beta2-adrenergic agonist

Cholera toxin, which has been frequently used as mucosal adjuvant, leads to an irreversible activation of adenylyl cyclase, thereby accumulating cAMP in target cells. Here, it was assumed that beta(2)-adrenergic agonist salbutamol may have modulatory functions of immunity induced by DNA vaccine, since beta(2)-adrenergic agonists induce a temporary cAMP accumulation. To test this assumption, the present study evaluated the modulatory functions of salbutamol co-administered with DNA vaccine expressing gB of herpes simplex virus (HSV) via intranasal (i.n.) route. We found that the i.n. co-administration of salbutamol enhanced gB-specific IgG and IgA responses in both systemic and mucosal tissues, but optimal dosages of co-administered salbutamol were required to induce maximal immune responses. Moreover, the mucosal co-delivery of salbutamol with HSV DNA vaccine induced Th2-biased immunity against HSV antigen, as evidenced by IgG isotypes and Th1/Th2-type cytokine production. The enhanced immune responses caused by co-administration of salbutamol provided effective and rapid responses to HSV mucosal challenge, thereby conferring prolonged survival and reduced inflammation against viral infection. Therefore, these results suggest that salbutamol may be an attractive adjuvant for mucosal genetic transfer of DNA vaccine.

The member of the cyclic di-nucleotide family bis-(3', 5')-cyclic dimeric inosine monophosphate exerts potent activity as mucosal adjuvant

Here we demonstrated that bis-(3',5')-cyclic dimeric inosine monophosphate (c-di-IMP) exhibits potent adjuvant properties. BALB/c or C57BL/6 mice were immunized with the model antigens beta-galactosidase (beta-Gal) or Ovalbumin (OVA) alone or co-administered with c-di-IMP by the intranasal route. Animals receiving c-di-IMP showed significantly higher anti-beta-Gal or OVA immunoglobulin G titres (IgG) in sera than those vaccinated with beta-Gal or OVA alone. Furthermore, strong local immune responses were also detectable in different mucosal territories, as shown by the high levels of beta-Gal-specific secretory IgA (sIgA). The analysis of the antigen-specific IgG isotypes in sera, together with the profiles of the cytokines and chemokines secreted by lymphocytes from vaccinated animals showed that the use of c-di-IMP resulted in stimulation of a mixed T(H)1/T(H)2/T(H)17 response. Mucosal immunization of C57BL/6 mice with OVA using c-di-IMP as adjuvant also led to the stimulation of strong in vivo CTL responses (i.e., 60% of antigen-specific lysis) [corrected].Our results demonstrated that the novel compound c-di-IMP exhibits strong adjuvant properties when co-administered with an antigen by the mucosal route, thereby representing a promising candidate adjuvant for the development of mucosal vaccination strategies.