Influence of intravenous anesthesia on mucosal and systemic antibody responses to nasal vaccines

Intranasal inoculations of naked or PLGA-PEI nanovectored DNA vaccine induce systemic and mucosal antibodies in pigs: A feasibility study

Mucosa are the routes of entry of most pathogens into animals' organisms. Reducing the important global burden of mucosal infectious diseases in livestock animals is required in the field of veterinary public health. For veterinary respiratory pathogens, one possible strategy is the development of intranasal (IN) DNA vaccination. The aim of this study was to assess the feasibility of IN DNA vaccination in pigs, an important species in livestock production industry, and a source of zoonotic diseases. To achieve this goal, we used a DNA vaccine against pseudorabies virus (PrV) encoding the immunogenic glycoprotein B (pcDNA3-gB plasmid). When pigs were inoculated with the naked DNA vaccine through the IN route, PrV-specific IgG and IgA type antibodies were detected in porcine sera. Interestingly, mucosal salivary IgA antibodies against PrV were also detected, at similar levels to those measured following intramuscular injection (positive controls). Furthermore, the IN delivery of pcDNA3-gB combined with PLGA-PEI nanoparticles resulted in similar levels of antibodies but was associated with an increase in the duration of detection of mucosal IgA for 2 out of 3 pigs. Our results suggest that there is room to improve the efficacy of IN DNA vaccination in pigs through optimization of IN inoculations, for example by using nanoparticles such as PLGA-PEI. Further studies will be dedicated to optimizing and testing the protective potential of IN DNA vaccination procedures against PrV.

Directing vaccine immune responses to mucosa by nanosized particulate carriers encapsulating NOD ligands

Mucosal surfaces are a major portal of entry for many pathogens that are the cause of infectious diseases. Therefore, effective vaccines that induce a protective immune response at these sites are much needed. However, despite early success with the live attenuated oral polio vaccine over 50 years ago, only a few new mucosal vaccines have been subsequently licensed. Development of new adjuvants, comprising antigen delivery platforms and immunostimulatory molecules, are critical for the successful development of new mucosal vaccines. Among them, biodegradable nanoparticle delivery systems are promising and NOD-like receptors are considered as potential new targets for immunostimulatory molecules. In this work, different NOD1 and NOD2 ligands were encapsulated in polylactic acid (PLA) nanoparticles, coated with HIV-1 gag p24 antigen. We showed that these new formulations are able to induce proliferation of HIV-specific T cells from HIV(+) individuals as well as autophagy. In vivo, these formulations highly enhanced p24-specific systemic and mucosal immune responses in mice not only after mucosal administration but also after immunization via the parenteral route. Our results provide a rational approach for combining nanosized particulate carriers and encapsulated NOD receptor ligands as potent synergistic tools for induction of specific mucosal immunity.

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.

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.

Effective induction of protective systemic immunity with nasally administered vaccines adjuvanted with IL-1

IL-1α and IL-1β were evaluated for their ability to provide adjuvant activity for the induction of serum antibody responses when nasally administered with protein antigens in mice and rabbits. In mice, intranasal (i.n.) immunization with pneumococcal surface protein A (PspA) or tetanus toxoid (TT) combined with IL-1β induced protective immunity that was equivalent to that induced by parenteral immunization. Nasal immunization of awake (i.e., not anesthetized) rabbits with IL-1-adjuvanted vaccines induced highly variable serum antibody responses and was not as effective as parenteral immunization for the induction of antigen-specific serum IgG. However, i.n. immunization of deeply anesthetized rabbits with rPA+IL-1α consistently induced rPA-specific serum IgG ELISA titers that were not significantly different than those induced by intramuscular (IM) immunization with rPA+alum although lethal toxin-neutralizing titers induced by nasal immunization were lower than those induced by IM immunization. Gamma scintigraphy demonstrated that the enhanced immunogenicity of nasal immunization in anesthetized rabbits correlated with an increased nasal retention of i.n. delivered non-permeable radio-labeled colloidal particles. Our results demonstrate that, in mice, IL-1 is an effective adjuvant for nasally administered vaccines for the induction of protective systemic immunity and that in non-rodent species, effective induction of systemic immunity with nasally administered vaccines may require formulations that ensure adequate retention of the vaccine within the nasal cavity.

Biomedical applications of sheep models: from asthma to vaccines

Although rodent models are very popular for scientific studies, it is becoming more evident that large animal models can provide unique opportunities for biomedical research. Sheep are docile in nature and large in size, which facilitates surgical manipulation, and their physiology is similar to humans. As a result, for decades they have been chosen for several models and continue to be used to study an ever-increasing array of applications. Despite this, their full potential has not been exploited. Here, we review the use of sheep as an animal model for human vaccine development, asthma pathogenesis and treatment, the study of neonatal development, and the optimization of drug delivery and surgical techniques.

Intranasal vaccination with poly(lactide-co-glycolide) microparticles containing a peptide T of Ole e 1 prevents mice against sensitization

BACKGROUND

Biodegradable microparticles, in particular poly(lactide-co-glycolide) (PLGA), have been shown as potential delivery vehicles for intranasal (i.n.) vaccines in animal models.

OBJECTIVES

To evaluate whether i.n. administration of PLGA microparticles containing a peptide with the major T cell epitope of Ole e 1, the main allergen of olive pollen, prevented mice from allergic sensitization to the whole protein.

METHODS

Peptide-PLGA microparticles were prepared by a solvent evaporation double emulsion method. Microparticles in a size range of 0.8 mum were evaluated for peptide loading and in vitro antigen release. Stability and immunogenicity of the entrapped peptide were retained, as determined by dot blot and ELISA inhibition. BALB/c mice were intranasally treated with peptide-PLGA microparticles for 3 consecutive days, 1 week before sensitization/challenge to Ole e 1. Blood, lungs and spleen were collected and analysed for immune response. Biodistribution of microparticles was investigated using confocal microscopy.

RESULTS

I.n. pretreatment of BALB/c mice with peptide-PLGA microparticles before sensitization to Ole e 1 led to a significant inhibition of serum allergen-specific IgE and IgG1 antibody levels, but a marked increase of specific IgG2a antibodies as compared with sham-pretreated mice. Moreover, IL-5 and IL-10 levels in spleen cell cultures were suppressed in peptide-PLGA pretreated mice. The airway histopathologic parameters associated with inflammation were significantly suppressed by the pretreatment.

CONCLUSION

These results demonstrate that i.n. immunization with peptide T-PLGA microparticles is effective in preventing subsequent allergic sensitization to Ole e 1. Our data indicate that peptide-PLGA microparticles may be promising candidates for the design of nasal vaccines against allergic diseases in humans.

Response of feral cats to vaccination at the time of neutering

OBJECTIVE

To determine whether administration of inactivated virus or modified-live virus (MLV) vaccines to feral cats at the time of neutering induces protective serum antiviral antibody titers.

DESIGN

Prospective study.

ANIMALS

61 feral cats included in a trap-neuter-return program in Florida.

PROCEDURES

Each cat received vaccines against feline panleukopenia virus (FPV), feline herpes virus (FHV), feline calicivirus (FCV), FeLV, and rabies virus (RV). Immediately on completion of surgery, vaccines that contained inactivated RV and FeLV antigens and either MLV or inactivated FPV, FHV, and FCV antigens were administered. Titers of antiviral antibodies (except those against FeLV) were assessed in serum samples obtained immediately prior to surgery and approximately 10 weeks later.

RESULTS

Prior to vaccination, some of the cats had protective serum antibody titers against FPV (33%), FHV (21%), FCV (64%), and RV (3%). Following vaccination, the overall proportion of cats with protective serum antiviral antibody titers increased (FPV [90%], FHV [56%], FCV [93%], and RV [98%]). With the exception of the FHV vaccine, there were no differences in the proportions of cats protected with inactivated virus versus MLV vaccines.

CONCLUSIONS AND CLINICAL RELEVANCE

Results suggest that exposure to FPV, FHV, and FCV is common among feral cats and that a high proportion of cats are susceptible to RV infection. Feral cats appeared to have an excellent immune response following vaccination at the time of neutering. Incorporation of vaccination into trap-neuter-return programs is likely to protect the health of individual cats and possibly reduce the disease burden in the community.

Evaluation of the immune response induced by a nasal anthrax vaccine based on the protective antigen protein in anaesthetized and non-anaesthetized mice

To better protect against inhalational anthrax infection, a nasal anthrax vaccine based on the protective antigen (PA) protein of Bacillus anthracis could be an attractive alternative to the current Anthrax-Vaccine-Adsorbed (AVA), which was licensed for cutaneous anthrax prevention. Previously, we have demonstrated that an anti-PA immune response comparable with that in mice subcutaneously immunized with PA protein adjuvanted with aluminium hydroxide was induced in both the systemic compartment and the mucosal secretions of the nose and lung of anaesthetized mice when they were nasally immunized with PA protein incorporated into previously reported LPD (Liposome-Protamine-DNA) particles. In this study, we evaluated the anti-PA immune response induced by the nasal PA/LPD particles in non-anaesthetized mice and compared it with that in anaesthetized mice. Our data showed that the anti-PA antibody response and the anthrax lethal toxin-neutralization activity induced by the nasal PA/LPD in non-anaesthetized mice was relatively weaker than that in anaesthetized mice. However, the splenocytes isolated from the nasally immunized mice, anaesthetized and non-anaesthetized, proliferated comparably after in-vitro re-stimulation. By evaluating the uptake of fluorescence-labelled LPD particles by phagocytes in the nasal and broncho-alveolar lavages of mice after the nasal administration, we concluded that the relatively weaker anti-PA immune response in the non-anaesthetized mice might be partially attributed to the reduced retention of the PA/LPD particles in the nasal cavity of the non-anaesthetized mice. Data collected in this study are expected to be useful for future anthrax nasal vaccine studies when mice are used as a model.

A sheep cannulation model for evaluation of nasal vaccine delivery

We have developed and validated a novel model to investigate the efficacy of nasal vaccine delivery. Based on lymphatic cannulation of the tracheal lymph trunk of sheep, the model allows collection of lymph draining from the Nasal Associated Lymphoid Tissue. The model is suitable for determining both the amount of material that is absorbed into the lymphatic system, following intra-nasal delivery and the immune response that occurs following vaccination into the nasal area. The cell populations that track in this duct were phenotyped and found to be similar to those previously reported to be present in efferent lymph draining from peripheral lymph nodes. Following intra-nasal spray, we demonstrated that the amount of material recovered in draining lymph is only a very small fraction of the total delivered. Nevertheless, intra-nasal spraying of a vaccine could activate local immune cells. The method described will be invaluable for optimising intra-nasal delivery systems by allowing a separate optimisation of vaccine uptake and immune responses induction.

Strong mucosal and systemic immunities induced by nasal immunization with anthrax protective antigen protein incorporated in liposome-protamine-DNA particles

PURPOSE

The very lengthy and complicated dosing schedule of the current anthrax vaccine adsorbed, which was licensed in the USA for the prevention of cutaneous anthrax infection, calls for the development of an efficacious and easily administrable vaccine to prevent against the most lethal form of anthrax infection, the inhalation anthrax. We propose to develop a nasal anthrax vaccine using anthrax protective antigen (PA) protein carried by liposome-protamine-DNA (LPD) particles.

METHODS

PA was incorporated in LPD particles and nasally dosed to mice. The resulting PA-specific immune response and lethal toxin neutralization activity were measured.

RESULTS

Mice nasally immunized with PA incorporated into LPD particles developed both systemic and mucosal anti-PA responses. The anti-PA immunities induced included the production of anti-PA antibodies (IgG and IgM in the serum and IgA in nasal and lung mucosal secretions) and the proliferation of splenocytes after in vitro stimulation. The anti-PA IgG subtype induced was mainly IgG1. Finally, anthrax lethal toxin neutralization activity was detected both in the serum and in the mucosal secretions.

CONCLUSIONS

The anti-PA immune response induced by nasal PA incorporated in LPD was comparable to that induced by nasal PA adjuvanted with cholera toxin or subcutaneously injected PA adjuvanted with aluminum hydroxide.

Intranasal immunization strategy to impede pilin-mediated binding of Pseudomonas aeruginosa to airway epithelial cells

Prevention of pulmonary Pseudomonas aeruginosa infections represents a critical unmet medical need for cystic fibrosis (CF) patients. We have examined the tenet that a mucosal immunization approach can reduce interactions of a piliated form of this opportunistic pathogen with respiratory epithelial cells. Vaccinations were performed using ntPEpilinPAK, a protein chimera composed of a nontoxic form of P. aeruginosa exotoxin A (ntPE), where the C-terminal loop amino acid sequence of the PAK strain pilin protein was inserted in place of the ntPE Ib domain. Intranasal (i.n.) immunization of BALB/c mice with ntPEpilinPAK generated both serum and saliva immune responses. A series of in vitro studies showed that diluted samples of saliva obtained from immunized mice reduced pilin-dependent P. aeruginosa binding to polarized human tracheal epithelial cells, protected human pulmonary epithelial cells from cytotoxic actions associated with bacterial challenge, and reduced exotoxin A toxicity. Overall, i.n. administration of ntPEpilinPAK induced mucosal and systemic immune responses that may be beneficial for blocking early stage adhesion and/or infection events of epithelial cell-P. aeruginosa interactions at oropharyngeal surfaces.

Type I IFN is a powerful mucosal adjuvant for a selective intranasal vaccination against influenza virus in mice and affects antigen capture at mucosal level

In view of the increasing interest in mucosal vaccination, we investigated whether type I IFN could act as adjuvant of an intranasally administered influenza vaccine. A single intranasal administration of IFNalphabeta-adjuvanted vaccine in anesthetized C3H/HeN mice was capable of protecting the totality of animals against virus challenge, while vaccine alone was only partially effective. To mimic intranasal vaccine administration in man and to limit vaccine delivery strictly to nasal mucosa, we used a second method of vaccination based on vaccine fractionation in six doses and intranasal instillation in non-anesthetized mice. By using this vaccination schedule, IFNalphabeta-adjuvanted vaccine also prevented mice from disease development and induced an efficient long lasting immune response. Further experiments showed that IFNalphabeta increased the percentage of antigen-associated phagocytes in the nasal mucus layer, thus suggesting a new possible mechanism of action for type I IFN as an adjuvant.