The positive adjuvant effect of chitosan on antigen-specific cell-mediated immunity after chickens vaccination with live Newcastle disease vaccine

Em14-3-3 delivered by PLGA and chitosan nanoparticles conferred improved protection in chicken against Eimeria maxima

Eimeria maxima (E. maxima) are an intracellular apicomplexan protozoan that causes intestinal coccidiosis in chickens. The purpose of this research was to develop a novel delivery approach for recombinant E. maxima (rEm) 14-3-3 antigen to elicit enhanced immunogenic protection using poly (D, L-lactide-co-glycolide) (PLGA) and chitosan (CS) nanoparticles (NPs) against E. maxima challenge. The morphologies of prepared antigen-loaded NPs (PLGA/CS-rEm14-3-3 NPs) were visualized by a scanning electron microscope. The rEm14-3-3 and PLGA/CS-rEm14-3-3 NPs-immunized chicken-induced changes of serum cytokines, IgY-antibody level, and T-lymphocyte subsets and protective efficacies against E. maxima challenge were evaluated. The results revealed that encapsulated rEm14-3-3 in PLGA and CS NPs presented spherical morphology with a smooth surface. The chickens immunized with only rEm14-3-3 and PLGA/CS-rEm14-3-3 NPs elicited a significant (p<0.05) higher level of IFN-γ cytokine, stimulated the proportions of CD4⁺/CD3⁺, CD8⁺/CD3⁺ T-cells, and provoked sera IgY-antibody immune response compared to control groups (PBS, pET-32a, PLGA, and CS). Whereas, PLGA-rEm14-3-3 NP-immunized chicken provoked a higher level of IFN- γ production and IgY-antibody response rather than CS-rEm14-3-3 and bare antigen, relatively. The animal experiment results ratified that PLGA-rEm14-3-3 NP-immunized chicken significantly alleviated the relative body weight gain (%), decreased lesion score, and enhanced oocyst decrease ratio compared to CS-rEm14-3-3 NPs and only rEm14-3-3. The anti-coccidial index of the chicken vaccinated with the PLGA-rEm14-3-3 NPs was (180.1) higher than that of the Cs-rEm14-3-3 NPs (167.4) and bare antigen (165.9). Collectively, our statistics approved that PLGA NPs might be an efficient antigen carrier system (Em14-3-3) to act as a nanosubunit vaccine that can improve protective efficacies in chicken against E. maxima challenge.

A Live Attenuated H9N2 Avian Influenza Vaccine Prevents the Viral Reassortment by Exchanging the HA and NS1 Packaging Signals

The H9N2 avian influenza virus is not only an important zoonotic pathogen, it can also easily recombine with other subtypes to generate novel reassortments, such as the H7N9 virus. Although H9N2 live attenuated vaccines can provide good multiple immunities, including humoral, cellular, and mucosal immunity, the risk of reassortment between the vaccine strain and wild-type virus is still a concern. Here, we successfully rescued an H9N2 live attenuated strain [rTX-NS1-128 (mut)] that can interdict reassortment, which was developed by exchanging the mutual packaging signals of HA and truncated NS1 genes and confirmed by RT-PCR and sequencing. The dynamic growth results showed that rTX-NS1-128 (mut) replication ability in chick embryos was not significantly affected by our construction strategy compared to the parent virus rTX strain. Moreover, rTX-NS1-128 (mut) had good genetic stability after 15 generations and possessed low pathogenicity and no contact transmission characteristics in chickens. Furthermore, chickens were intranasally immunized by rTX-NS1-128 (mut) with a single dose, and the results showed that the hemagglutination inhibition (HI) titers peaked at 3 weeks after vaccination and lasted at least until 11 weeks. The cellular immunity (IL-6 and IL-12) and mucosal immunity (IgA and IgG) in the nasal and trachea samples were significantly increased compared to inactivated rTX. Recombinant virus provided a good cross-protection against homologous TX strain (100%) and heterologous F98 strain (80%) challenge. Collectively, these data indicated that rTX-NS1-128(mut) lost the ability for independent reassortment of HA and NS1-128 and will be expected to be used as a potential live attenuated vaccine against H9N2 subtype avian influenza.

Chitosan Nanoparticle Based Mucosal Vaccines Delivered Against Infectious Diseases of Poultry and Pigs

Infectious disease of poultry and pig are major threat to health and cause severe economic loss to the food industry and a global food safety issue. Poultry and pig act as a mixing vessel of zoonotic transmission of disease to humans. Effective mucosal vaccines used in animals could reduce the impact of diseases in food animals. Chitosan is a biocompatible polymer, and its positive charge makes it a natural mucoadhesive agent. Therefore, since last one-decade chitosan derived nanoparticles (CS NPs) have been in use widely to deliver vaccine antigens in animals through mucosal route. Primary route of entry of most infectious disease pathogen is through oral and nasal routes, and the CS NPs based vaccines delivered through that routes enhance the immunogenicity of encapsulated vaccine antigens by targeting the cargo to mucosal microfold cells, dendritic cells and macrophages. Resulting in induction of robust secretory and systemic antibodies and/or cell mediated immune response which provides protection against infections. To date, CS NPs is being widely used for mucosal vaccine delivery in poultry and pigs to control bacterial and viral infections, and tested in several preclinical trials for vaccine delivery in humans. In this review, we highlighted the progress so far made in using CS NPs as a vehicle for mucosal vaccine delivery against infectious and zoonotic diseases of poultry and pigs. Discussed about the need of CS NPs modifications, CS NPs based vaccines induced immune responses and its role in protection, and challenges in vaccination and future directions.

Quaternized Chitosan Nanoparticles in Vaccine Applications

Different natural and synthetic biodegradable polymers have been used in vaccine formulations as adjuvant and delivery system but have faced various limitations. Chitosan is a new delivery system with the potential to improve development of nano vaccines and drugs. However, chitosan is only soluble in acidic solutions of low concentration inorganic acids such as dilute acetic acid and dilute hydrochloric acid and in pure organic solvents, which greatly limits its application. Chemical modification of chitosan is an important way to improve its weak solubility. Quaternized chitosan not only retains the excellent properties of chitosan, but also improves its water solubility for a wider application. Recently, quaternized chitosan nanoparticles have been widely used in biomedical field. This review focuses on some quaternized chitosan nanoparticles, and points out the advantages and research direction of quaternized chitosan nanoparticles. As shown by the applications of quaternized chitosan nanoparticles as adjuvant and delivery carrier in vaccines, quaternized chitosan nanoparticles have promising potential in application for the development of nano vaccines in the future.

Recent Approaches for Solid Dose Vaccine Delivery

Recent studies on vaccine delivery systems are exploring the possibility of replacing liquid vaccines with solid dose vaccines due to the many advantages that solid dose vaccines can offer. These include the prospect of a needle-free vaccine delivery system leading to better patient compliance, cold chain storage, less-trained vaccinators and fewer chances for needle stick injury hazards. Some studies also indicate that vaccines in a solid dosage form can result in a higher level of immunogenicity compared to the liquid form, thus providing a dose-sparing effect. This review outlines the different approaches in solid vaccine delivery using various routes of administration including, oral, pulmonary, intranasal, buccal, sublingual, and transdermal routes. The various techniques and their current advancements will provide a knowledge base for future work to be carried out in this arena.

Chitosan, hydroxypropyltrimethyl ammonium chloride chitosan and sulfated chitosan nanoparticles as adjuvants for inactivated Newcastle disease vaccine

Chitosan (CS) and its water-soluble derivatives, hydroxypropyltrimethyl ammonium chloride chitosan (HACC) and sulfated chitosan (SCS), were used as adjuvants of inactivated Newcastle disease (ND) vaccine. First, NDV-loaded and blank CS, HACC/CS and SCS nanoparticles were prepared. The particle sizes were respectively 343.43 ± 4.12, 320.03 ± 0.84, 156.2 ± 9.29 nm and the zeta potentials were respectively +19.67 ± 0.58, +18.3 ± 0.5, -17.8 ± 2.65 mV under the optimal conditions. Then chickens were immunized with nanoparticles or commercial inactivated oil emulsion vaccine. After immunization, the humoral immunity levels of the chickens were evaluated. The cellular immunity levels were determined by the quantification of cytokines, lymphocyte proliferation assay, the percentages of CD4⁺ and CD8⁺ T lymphocytes. Finally, the chickens were challenged with highly virulent virus. The results demonstrated that the humoral immunity levels in NDV-loaded CS and HACC/CS nanoparticles groups were lower than commercial vaccine but the cellular immunity levels are better. Moreover, the prevention effects of NDV-loaded CS and HACC/CS nanoparticles against highly virulent NDV are comparable to commercial vaccine. Our study provides the basis of developing HACC and CS as effective vaccine adjuvants.

Chitosan-adjuvanted Mycoplasma gallisepticum bacterin via intraocular administration enhances Mycoplasma gallisepticum protection in commercial layers

Mycoplasma gallisepticum (MG) causes respiratory signs and economic losses in the poultry industry. MG vaccination is one of the effective prevention and control measures that have been used around the world. Our previous study demonstrated that chitosan-adjuvanted MG bacterin could effectively reduce pathological lesions induced by MG and that chitosan could be used as an adjuvant in MG bacterin. The present study determining the efficacy of MG bacterins against the Thai MG strain was based on vaccine programs. Seven groups (25 layers/group) were received MG bacterins containing 0.5% chitosan or a commercial bacterin via intramuscular (IM) or intraocular (IO) route at 6 and 10 wk of age. Sham-negative and sham-positive controls were groups 1 and 2, respectively. Group 3: IM route of chitosan bacterin followed by IM route of chitosan bacterin; group 4: commercial bacterin via IM route followed by chitosan bacterin via IO route; group 5: commercial bacterin via IM route followed by commercial bacterin via IM route; group 6: chitosan bacterin via IM followed by chitosan bacterin via IO route; and group 7: chitosan bacterin via IO route followed by chitosan bacterin via IO route were determined. At 16 wk of age, all groups, excluding group 1, were challenged intratracheally with 0.1 mL containing Thai MG strain 107 colony-forming unit. At 17, 18, and 20 wk of age, 5 birds in each group were bled for serological testing and swabbed at the choanal cleft for the quantitative real-time PCR assay, the euthanized and necropsied. The results showed that birds vaccinated with a commercial intramuscular bacterin followed by an intraocularly chitosan adjuvant bacterin showed the best protection against the MG challenge. The study indicated that chitosan could be the effective mucosal adjuvant and increased the effectiveness of MG bacterin.

The Well-Developed Mucosal Immune Systems of Birds and Mammals Allow for Similar Approaches of Mucosal Vaccination in Both Types of Animals

The mucosal immune system is a compartmentalized part of the immune system that provides local immunity in the mucosa of the respiratory, gastrointestinal, and digestive tracts. It possesses secondary lymphoid tissues, which contain immune cells, such as T, B, and dendritic cells. Once the cells of the mucosal immune system are stimulated by luminal antigens, including microorganisms, they infiltrate into diffuse areas of mucosal tissues (e.g., respiratory mucosa and lamina propria of intestinal villi) and exhibit immune effector functions. Inducing the antigen-specific immune responses in mucosal tissues by mucosal vaccination would be an ideal strategy for not only humans, but also mammals and birds, to protect against infectious diseases occurring in mucosal tissues (e.g., pneumonia and diarrhea). Infectious diseases cause huge economic losses in agriculture, such as livestock and poultry industries. Since most infectious diseases occur in mucosal tissues, vaccines that are capable of inducing immune responses in mucosal tissues are in high need. In this review, we discuss the current understanding of mucosal immunity in mammals and birds, and recent progress in the development of mucosal vaccines.

Prime-boost vaccination strategy against avian influenza and Newcastle disease viruses reduces shedding of the challenge viruses

In the present study, we carried-out assessment of efficacy of different immunization strategies using two bivalent vaccine formulations containing antigens of inactivated Newcastle disease virus (NDV-genotype VIId) and reassortant highly pathogenic avian influenza virus (H5N1-HPAIV) mixed with Montanide ISA71 and Montanide Gel02 as adjuvants. The efficacy of the prepared vaccines was evaluated by determining the cellular and humoral immune responses. In addition, protection against H5N1-AIV and NDV-genotype VIId challenge viruses post vaccination was assessed when Montanide-Gel02 based vaccine was inoculated in 10-days-old specific pathogen free chicks intraocularly once, twice or once followed by a boost with the Montanide ISA71 based vaccine. The cytokines profile analysis demonstrated that the prime-boost strategy induced the highest up-regulation in interferon-gamma (11.39-fold change) and interleukin-6 (14.12-fold change) genes expression. Also, enhanced lymphocytes proliferation was recorded beside increased antibody titers with protection levels reaching 50 and 60% against H5N1 and NDV challenge; respectively. Immunization with Montanide ISA71 inactivated vaccine induced 80% protection; however, the prime-boost combination afforded complete protection (100%) in the challenged chickens against mortality, clinical signs and virus shedding. Finally, these results highlight the significance of considering not only different vaccine platforms but also vaccination strategies to maximize protection against AIV and NDV with regards to the longevity of the vaccine-induced immune response.

Quaternized chitosan nanoparticles loaded with the combined attenuated live vaccine against Newcastle disease and infectious bronchitis elicit immune response in chicken after intranasal administration

Newcastle disease (ND) and infectious bronchitis (IB) are important diseases, which cause respiratory diseases in chickens, resulting in severely economic losses in the poultry industry. In this study, N-2-hydroxypropyl trimethyl ammonium chloride chitosan (N-2-HACC) and N,O-carboxymethyl chitosan (CMC) were synthesized as adjuvant and delivery carrier for vaccine antigens. N-2-HACC-CMC/NDV/IBV nanoparticles (NPs) (NDV/La Sota and IBV/H120 encapsulated in N-2-HACC-CMC NPs) and N-2-HACC-CMC/NDV-IBV NPs (the mixing of N-2-HACC-CMC/NDV NPs and N-2-HACC-CMC/IBV NPs in a ratio of 1:1) were prepared by the polyelectrolyte composite method, respectively. Both nanoparticles exhibited lower cytotoxicity and higher stability. Their bioactivities were maintained when they were stored at 37 °C for three weeks. Release assay in vitro showed that both NDV and IBV could be sustainably released from the nanoparticles after an initial burst release. In vivo immunization of chickens showed that N-2-HACC-CMC/NDV/IBV NPs or N-2-HACC-CMC/NDV-IBV NPs intranasally induced higher titers of IgG and IgA antibodies, significantly promoted proliferation of lymphocytes and induced higher levels of interleukine-2 (IL-2), IL-4 and interferon-γ (IFN-γ) than the commercially combined attenuated live vaccine did. This is the first study in the field of animal vaccines demonstrating that intranasal administration of chickens with antigens (NDV and IBV) encapsulated with chitosan derivative could induce humoral, cellular, and mucosal immune responses, which protected chickens from the infection of highly virulent NDV and IBV. This study indicated that N-2-HACC-CMC could be used as an efficient adjuvant and delivery carrier for further development of mucosal vaccines and drugs and could have an immense application potential in medicine.

Evaluation of N-phosphonium chitosan as a novel vaccine carrier for intramuscular immunization

Chitosan, as a potential vaccine delivery material, has obtained much attention for immunization prevention and therapy. However, its poor water solubility brings inconvenience for the practical applications. To address this issue, researchers have carried out many chemical modifications to prepare water-soluble chitosan derivatives for vaccine delivery. In this work, we prepared a chitosan derivative N-phosphonium chitosan with excellent water solubility and explored its potential as an intramuscular vaccine delivery system by using ovalbumin as a model antigen. Different vaccine formulations were intramuscularly injected into test mice. Through an immunohistochemistry assay, N-phosphonium chitosan-based antigen formulation could promote antigen arrival from injection site to the secondary lymph organ spleen. Further immunization results showed that 1 mg/ml N-phosphonium chitosan-based vaccine formulation could contribute to significantly higher level of antigen-specific immune responses, including higher antigen-specific IgG antibody titer, splenocyte proliferation, and cytokines secretion (interferon-γ, interleukin-10, and interleukin-4) by the splenocytes of the immunized mice. From the results, the water-soluble chitosan derivative N-phosphonium chitosan could be developed as a potential antigen carrier for immunization prevention and therapy.

Adjuvants for Animal Vaccines

Vaccines are essential tools for the prevention and control of infectious diseases in animals. One of the most important steps in vaccine development is the selection of a suitable adjuvant. The focus of this review is the adjuvants used in vaccines for animals. We will discuss current commercial adjuvants and experimental formulations with attention to mineral salts, emulsions, bacterial-derived components, saponins, and several other immunoactive compounds. In addition, we will also examine the mechanisms of action for different adjuvants, examples of adjuvant combinations in one vaccine formulation, and challenges in the research and development of veterinary vaccine adjuvants.

Efficacy of Live-Attenuated H9N2 Influenza Vaccine Candidates Containing NS1 Truncations against H9N2 Avian Influenza Viruses

H9N2 avian influenza virus is a zoonotic agent with a broad host range that can contribute genetic information to H5 or H7N9 subtype viruses, which are significant threats to both humans and birds. Thus, there is a great need for a vaccine to control H9N2 avian influenza. Three mutant viruses of an H9N2 virus A/chicken/Taixing/10/2010 (rTX-NS1-73, rTX-NS1-100, and rTX-NS1-128) were constructed with different NS1 gene truncations and confirmed by western blot analysis. The genetic stability, pathogenicity, transmissibility, and host immune responses toward these mutants were evaluated. The mutant virus rTX-NS1-128 exhibited the most attenuated phenotype and lost transmissibility. The expression levels of interleukin 12 in the nasal and tracheal tissues from chickens immunized with rTX-NS1-128 were significantly upregulated on day 3 post-immunization and the IgA and IgG antibody levels were significantly increased on days 7, 14, and 21 post-immunization when compared to chickens that received an inactivated vaccine. rTX-NS1-128 also protected chickens from challenge by homologous and heterologous H9N2 avian influenza viruses. The results indicate that rTX-NS1-128 can be used as a potential live-attenuated vaccine against H9N2 avian influenza.

Specific antibody-mediated immunity in the reproductive tract of laying chickens immunized against Newcastle disease with conventional attenuated and inactivated vaccines

Despite the widespread and successful use of Newcastle disease (ND) vaccines, Newcastle disease virus (NDV) can seriously injure the reproductive tract of egg-laying hens, leading to rapid egg-drop and poor shell quality. Few published studies investigated local NDV-specific immune response in the reproductive tract after ND vaccination of hens. The present study investigated, for the first time, local NDV-specific antibody-mediated immunity in segments of the oviduct during the laying period. Specific pathogen-free (SPF) White Leghorn chickens were immunized following an ND vaccination programme applied in the field, which combined ND-attenuated vaccine (inoculated subcutaneously at one day, 2 weeks and 11 weeks of age) with inactivated vaccine (inoculated intramuscularly at 17 weeks). The infundibulum, magnum, isthmus and uterus (segments of the reproductive tract) were harvested at 28 weeks and 32 weeks of age (during the laying period). Supernatant from ex vivo tissue culture was collected and tested by: (i) haemagglutination inhibition (HI) test, (ii) commercial IDVet ND-enzyme-linked immunosorbent assay (ELISA) and (iii) NDV-specific IgG, IgM and IgA in-house ELISAs. For all sampling time points and oviduct segments, all samples were positive for commercial ND-ELISA and in-house ELISA-IgG. However, six of these ELISA-IgG positive samples yielded negative results when submitted to the HI test. Interestingly, NDV-specific IgM and IgA were detected frequently in the infundibulum and magnum as compared to the isthmus and uterus. These results show that the antibody immune response in the oviduct was induced by the timing of attenuated and inactivated ND vaccinations.

pH Sensitive phosphorylated chitosan hydrogel as vaccine delivery system for intramuscular immunization

In the field of immunotherapy, immune vaccinations have received more and more attention for disease prevention and treatment. In immune vaccination, efficient vaccine adjuvants are necessary due to the weak immunogenicity of vaccines. Some traditional vaccine adjuvants have been widely used but have shown obvious limitations such as poor biosafety. Therefore, researchers make a great effort to develop more functional novel immune adjuvants such as chitosan-based immune adjuvants. However, chitosan is poorly water soluble, which greatly limits its application as immune adjuvants, regardless of its good biocompatibility, biodegradability, and other biological activities. In this work, we prepared a water-soluble chitosan derivative phosphorylated chitosan (PCS) and evaluated its potential as a novel immune adjuvant. PCS was found to be pH sensitive: specifically, it was water soluble at pH < 7.0 but began to gel at pH >7.0. By virtue of this, neutral PCS aqueous solutions containing ovalbumin (OVA) antigen was intramuscularly injected into test mice, which would transform to an OVA-containing gel network for OVA immunization. The results showed that the use of 30 mg/mL PCS-based hydrogel as vaccine delivery system contributed to significantly higher level of antigen-specific immune responses, including higher level of antigen-specific IgG antibodies, IFN-γ and IL-4 cytokines secretion by splenocytes, as well as memory CD4+ and CD8+ T cells. In vivo imaging and immunohistochemistry assays suggest that the improved immunization efficacy may be attributed to the controlled release of antigen from injection site by PCS gel network, and then prolonged antigen stimuli to the immune system. From the results, PCS could be developed as a promising vaccine delivery system for immunotherapy.

Newcastle disease vaccines-A solved problem or a continuous challenge?

Newcastle disease (ND) has been defined by the World Organisation for Animal Health as infection of poultry with virulent strains of Newcastle disease virus (NDV). Lesions affecting the neurological, gastrointestinal, respiratory, and reproductive systems are most often observed. The control of ND must include strict biosecurity that prevents virulent NDV from contacting poultry, and also proper administration of efficacious vaccines. When administered correctly to healthy birds, ND vaccines formulated with NDV of low virulence or viral-vectored vaccines that express the NDV fusion protein are able to prevent clinical disease and mortality in chickens upon infection with virulent NDV. Live and inactivated vaccines have been widely used since the 1950's. Recombinant and antigenically matched vaccines have been adopted recently in some countries, and many other vaccine approaches have been only evaluated experimentally. Despite decades of research and development towards formulation of an optimal ND vaccine, improvements are still needed. Impediments to prevent outbreaks include uneven vaccine application when using mass administration techniques in larger commercial settings, the difficulties associated with vaccinating free-roaming, multi-age birds of village flocks, and difficulties maintaining the cold chain to preserve the thermo-labile antigens in the vaccines. Incomplete or improper immunization often results in the disease and death of poultry after infection with virulent NDV. Another cause of decreased vaccine efficacy is the existence of antibodies (including maternal) in birds, which can neutralize the vaccine and thereby reduce the effectiveness of ND vaccines. In this review, a historical perspective, summary of the current situation for ND and NDV strains, and a review of traditional and experimental ND vaccines are presented.

Significant mucosal sIgA production after a single oral or parenteral administration using in vivo CD40 targeting in the chicken

Many pathogens enter the host through mucosal surfaces and spread rapidly via the circulation. The most effective way to prevent disease is to establish mucosal and systemic immunity against the pathogen. However, current vaccination programs in poultry industry require repeated administrations of live-attenuated virus or large amounts (10 to 100μg) of antigen together with adjuvant to induce specific secretory IgA immune responses at the mucosal effector sites. In the present study, we show that a single administration of 0.4μg of oligopeptide complexed with an agonistic anti-chicken CD40 (chCD40) monoclonal antibody (Mab) effectively targets antigen-presenting cells of the bird's mucosa-associated lymphoid tissue in vivo, and induces peptide-specific secretory IgA (sIgA) in the trachea 7days post administration. Anti-chCD40 Mab-peptide complex was administered once to four-week old male Leghorns via various mucosal routes (orally, via cloacal drinking, or oculo-nasally) or via subcutaneous (s.c.) immunization. Immunization through any of the three mucosal induction routes induced significant peptide-specific mucosal sIgA responses 7 and 14days after immunization. Interestingly, s.c. injection of the complex also induced mucosal sIgA. Our data suggest in vivo targeting of CD40 as a potential adjuvant platform, particularly for the purpose of enhancing and speeding up mucosal vaccine responses in chickens, and potentially other food animals. This is the first study able to elicit specific sIgA immune responses in remote mucosal sites with a single administration of only 0.4μg of antigen.

Biological evaluation of N-2-hydroxypropyl trimethyl ammonium chloride chitosan as a carrier for the delivery of live Newcastle disease vaccine

Mucosal immune system plays a very important role in antiviral immune response. We prepared Newcastle disease viruses (NDV) encapsulated in N-2-hydroxypropyl trimethyl ammonium chloride chitosan (N-2-HACC) nanoparticles (NDV/La Sota-N-2-HACC-NPs) by an ionic cross linking method, and assessed the potential of N-2-HACC-NPs as a mucosal immune delivery carrier. The properties of the nanoparticles were determined by transmission electron microscopy, Zeta potential and particle size analysis, encapsulation efficiency and loading capacity. NDV/La Sota-N-2-HACC-NPs have regular spherical morphologies and high stability; with 303.88±49.8nm mean diameter, 45.77±0.75mV Zeta potential, 94.26±0.42% encapsulation efficiency and 54.06±0.21% loading capacity. In vitro release assay indicated that the release of NDV from NDV/La Sota-N-2-HACC-NPs is slow. The NDV/La Sota-N-2-HACC-NPs have good biological characteristics, very low toxicity and high level of safety. Additionally, specific pathogen-free chickens immunized with NDV/La Sota-N-2-HACC-NPs showed much stronger cellular, humoral and mucosal immune responses than commercial attenuated live Newcastle disease vaccine, and NDV/La Sota-N-2-HACC-NPs reached the sustainable release effect. Our study here provides a foundation for the further development of mucosal vaccines and drugs, and the N-2-HACC-NPs should be a potential drug delivery carrier with immense potential in medical applications.

Development of an effective delivery system for intranasal immunization against Mycobacterium tuberculosis ESAT-6 antigen

Introduction The early secreted antigenic target 6-kDa protein (ESAT-6) plays an important role in immune protection against Tuberculosis. Owing to its great potential to increase immune response, chitosan can be considered as a suitable biodegradable polymer for intranasal administration. Methods The physiochemical properties of the nanoparticle were measured in vitro. Two weeks after the last intranasal administration, blood samples were collected and specific IgG, IFN-gama, and IL-4 levels were measured by ELISA. Results Chitosan nanoparticles containing ESAT-6 demonstrated stronger ability to induce IFN-gama, IL-4, and IgG antibody level than the control groups. Conclusion Administration of chitosan nanoparticles can be a suitable method to induce more appropriate immune responses against low inherent immunogenic tuberculosis proteins through intranasal routs.

Adjuvant-dependent immunogenicity of Staphylococcus aureus Efb and Map proteins in chickens

The avian IgY antibodies generated in hens and isolated from egg yolk have gained in popularity as they present an alternative source of antibodies for diagnostic as well as therapeutic applications. One of the advantages of IgY technology are the large amounts of produced antibodies from a single animal combined with their high reactivity representing an attractive alternative for mammalian antibodies. Despite many known protocols for the immunization of chickens, the administration of new antigens often requires additional modification such as antigen dose or use of an adjuvant in order to elicit a significant immune response. We investigated the immunogenicity of three Staphylococcus aureus antigens including two extracellular proteins Map and Efb and one selected Efb105-124 epitope conjugated to KLH that were administered to the animals. Additionally, the immunization protocol included two adjuvant systems: Freund's complete adjuvant and Emulsigen-D. The results demonstrated a high immunostimulatory potency of Freund's complete adjuvant, especially in case of Efb compared to the immune response elicited by Emulsigen-D. However, after immunization with the KLH-Efb105-124 conjugate, the obtained antibodies showed similar reactivity regardless of adjuvant system used with the only exception being their avidity.

Newcastle disease virus vaccine encapsulated in biodegradable nanoparticles for mucosal delivery of a human vaccine

An overwhelming number of medicines on the market are oral medicine with the disadvantage of lower bioavailability universally. Newcastle disease (ND) has become a serious disease that threatens the poultry industries in many countries, and there are no treatments available for ND. The biodegradable materials could be surface modified and protect antigen or DNA from damage. Furthermore, nanoparticles are also a potential drug delivery with proper size. However, Newcastle disease virus (NDV) vaccines encapsulated in nanoparticles were widely used due to their proved a high safety and induced quicker and better mucosal and humoral immune responses. Here we review the results of mucosal immune delivery system for ND. Due to the safety, low toxicity, and better immunogenicity of the mucosal immune delivery system, our studies provide a clearly view that used the biodegradable materials to research and develop the human vaccines to save more patients' lives. These promising results provide a foundation for testing the approach in humans.

O-2'-hydroxypropyltrimethyl ammonium chloride chitosan nanoparticles for the delivery of live Newcastle disease vaccine

A novel complex chitosan derivative, O-2'-hydroxypropyltrimethyl ammonium chloride chitosan (O-2'-HACC), was synthesized and used to make nanoparticles as a delivery vehicle for live attenuated Newcastle disease vaccine. We found that O-2'-HACC had high antimicrobial activity, low toxicity, and a high safety level. Newcastle disease virus (NDV) was then encapsulated in the O-2'-HACC nanoparticles (NDV/La Sota-O-2'-HACC-NPs) by the ionic crosslinking method, and the properties of the resulting nanoparticles were determined by transmission electron microscopy, Zeta potential analysis, Fourier transform infrared spectroscopy, proton nuclear magnetic resonance spectroscopy, and X-ray diffraction. NDV/La Sota-O-2'-HACC-NPs had regular spherical morphologies and high stability, with an encapsulation efficiency of 95.68 ± 2.2% and a loading capacity of 58.75 ± 4.03%. An in vitro release assay indicated that release of NDV from NDV/La Sota-O-2'-HACC-NPs occurred slowly. Specific pathogen-free chickens immunized with NDV/La Sota-O-2'-HACC-NPs intranasally had much stronger cellular, humoral and mucosal immune responses than did those immunized intramuscularly or with live attenuated Newcastle disease vaccine. NDV/La Sota-O-2'-HACC-NPs are a novel drug delivery carrier with immense potential in medical applications.

CpG oligonucleotides and Astragalus polysaccharides are effective adjuvants in cultures of avian bone-marrow-derived dendritic cells

1. The potential use of CpG oligodeoxynucleotides and/or Astragalus polysaccharide (APS) as adjuvants for the culture of chicken bone-marrow-derived dendritic cells (chBM-DCs) was investigated. 2. Chicken dendritic cells (DCs) were isolated and cultured in the presence of recombinant chicken granulocyte-macrophage colony-stimulating factor (GM-CSF) and interleukin (IL)-4. The chBM-DC displayed typical DC morphology and expressed DC surface markers (MHC-II and CD11c). 3. Cultured chBM-DC showed effective T-cell activation in vitro, based on a mixed lymphocyte response (MLR). Flow cytometry analysis showed an increased proportion of cells expressing CD40 and CD80 in the APS-stimulated culture, compared to the control culture. In the MLR, the APS- and CpG-stimulated chBM-DC could activate T-cells more than control chBM-DC. Real-time PCR assays showed that CpG can activate the TLR21 and an inflammatory response, while APS just reduced the expression of IRF-3. 4. The results demonstrated that in vitro the adjuvant CpG can stimulate chBM-DC to mature by activation of the TLR-signalling pathway, whereas the adjuvant APS stimulates maturation of chBM-DC in vitro to a lesser degree and by another mechanism.

Adjuvant effects of mannose-binding lectin ligands on the immune response to infectious bronchitis vaccine in chickens with high or low serum mannose-binding lectin concentrations

Mannose-binding lectin (MBL) plays a major role in the immune response as a soluble pattern-recognition receptor. MBL deficiency and susceptibility to different types of infections have been subject to extensive studies over the last decades. In humans and chickens, several studies have shown that MBL participates in the protection of hosts against virus infections. Infectious bronchitis (IB) is a highly contagious disease of economic importance in the poultry industry caused by the coronavirus infectious bronchitis virus (IBV). MBL has earlier been described to play a potential role in the pathogenesis of IBV infection and the production of IBV-specific antibodies, which may be exploited in optimising IBV vaccine strategies. The present study shows that MBL has the capability to bind to IBV in vitro. Chickens from two inbred lines (L10H and L10L) selected for high or low MBL serum concentrations, respectively, were vaccinated against IBV with or without the addition of the MBL ligands mannan, chitosan and fructooligosaccharide (FOS). The addition of MBL ligands to the IBV vaccine, especially FOS, enhanced the production of IBV-specific IgG antibody production in L10H chickens, but not L10L chickens after the second vaccination. The addition of FOS to the vaccine also increased the number of circulating CD4+ cells in L10H chickens compared to L10L chickens. The L10H chickens as well as the L10L chickens also showed an increased number of CD4-CD8α-γδ T-cells when an MBL ligand was added to the vaccine, most pronouncedly after the first vaccination. As MBL ligands co-administered with IBV vaccine induced differences between the two chicken lines, these results indirectly suggest that MBL is involved in the immune response to IBV vaccination. Furthermore, the higher antibody response in L10H chickens receiving vaccine and FOS makes FOS a potential adjuvant candidate in an IBV vaccine.

A novel combined adjuvant strongly enhances mucosal and systemic immunity to low pathogenic avian influenza after oral immunization in ducks

As natural reservoirs of avian influenza viruses, waterfowl play an important role in the generation, spread, and enzootic transmission of avian influenza. To prevent avian influenza in waterfowl through a simple, noninvasive, and needle-free route, ducks were immunized orally with an inactivated avian influenza virus (H9N2, IAIV) combined with CpG DNA and high-dose glucose, and then the local and systemic immune responses of these ducks were investigated. In addition, the immune protection was assayed after viral challenge. After the oral administration of IAIV combined with CpG DNA and glucose, the expression levels of interleukin-2 and interleukin-6 in the small intestine tissues increased significantly in the early period after booster immunization relative to the levels after immunization with IAIV and a single adjuvant. Significant increases were also observed in the IgA and IgG antibody levels in the local intestinal tract tissues and serum at wk 3, 5, and 7 after the first immunization. Furthermore, enhanced hemagglutination inhibition titers were also detected in serum samples taken between the third and seventh weeks after immunization with IAIV and both adjuvants. In the viral challenge and transmission study, the prior administration of IAIV combined with both CpG DNA and glucose reduced the viral titers observed for the cloaca swabs and colon tissues of challenged ducks and prevented virus transmission between ducks. Our study suggests that the combination of CpG DNA and high-dose glucose can improve immunization with inactivated H9N2 virus by enhancing the local and systemic immune responses and reducing viral shedding.

Vaccination of gallinaceous poultry for H5N1 highly pathogenic avian influenza: current questions and new technology

Vaccination of poultry for avian influenza virus (AIV) is a complex topic as there are numerous technical, logistic and regulatory aspects which must be considered. Historically, control of high pathogenicity (HP) AIV infection in poultry has been accomplished by eradication and stamping out when outbreaks occur locally. Since the H5N1 HPAIV from Asia has spread and become enzootic, vaccination has been used on a long-term basis by some countries to control the virus, other countries have used it temporarily to aid eradication efforts, while others have not used it at all. Currently, H5N1 HPAIV is considered enzootic in China, Egypt, Viet Nam, India, Bangladesh and Indonesia. All but Bangladesh and India have instituted vaccination programs for poultry. Importantly, the specifics of these programs differ to accommodate different situations, resources, and industry structure in each country. The current vaccines most commonly used are inactivated whole virus vaccines, but vectored vaccine use is increasing. Numerous technical improvements to these platforms and novel vaccine platforms for H5N1 vaccines have been reported, but most are not ready to be implemented in the field.

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.

Chitosan-based delivery systems for mucosal vaccines

INTRODUCTION

Mucosal vaccine development faces several challenges and opportunities. Critical issues for effective mucosal vaccination include the antigen-retention period that enables interaction with the lymphatic system, choice of adjuvant that is nontoxic and induces the required immune response and possibly an ability to mimic mucosal pathogens. Chitosan-based delivery systems are reviewed here as they address these issues and hence represent the most promising candidates for the delivery of mucosal vaccines.

AREAS COVERED

A comprehensive literature search was conducted, to locate relevant studies published within the last 5 years. Mucosal delivery via nasal and oral routes is evaluated with respect to chitosan type, dosage forms, co-adjuvanting with novel adjuvants and modulation of the immune system.

EXPERT OPINION

It is concluded that chitosan derivatives offer advantageous opportunities such as nanoparticle and surface charge manipulation that facilitate vaccine targeting. Nevertheless, these technologies represent a longer-term goal. By contrast, chitosan (unmodified form) with or without a co-adjuvant has significant toxicology and human data to support safe mucosal administration, and thus has the potential for earlier product introduction into the market.

Efficacy of intranasal and spray delivery of adjuvanted live vaccine against infectious bronchitis virus in experimentally infected poultry

Live vaccines are widely used in the avian industry. Such vaccines can be either injected or delivered on animal mucosa and are usually not adjuvanted. In this study we show that live vaccines efficacy can be improved by formulation with adjuvants in a model of mucosal delivery of live infectious bronchitis vaccine in chicken. Three adjuvant technologies have been tested using intranasal and spray delivery methods to poultry. Those technologies are water in oil in water emulsion, nanoparticles and polymer adjuvants. Intranasal delivery of polymer and nanoparticles adjuvanted live vaccines improved significantly the antibody titer and protection to challenge observed compared to a commercial non-adjuvanted reference. Moreover, spray delivery of the polymer adjuvanted vaccine showed a significantly higher protection compared to the non-adjuvanted reference. Our data demonstrates that the use of MontanideTM adjuvants in the formulation of live poultry vaccines for mucosal delivery can confer to vaccinated animals a significantly improved protection against pathogens.

Load reduction in live PRRS vaccines using oil and polymer adjuvants

PRRSV live vaccines are widely used in pig farming practice and are usually not adjuvanted. For safety issues, it would be useful to reduce the antigenic load of such vaccines while preserving their efficacy. In this study we show that the addition of polymer or oil adjuvants in a PRRS live vaccine enhanced the protection to challenge of vaccinated animals compared to a non-adjuvanted commercial reference. Moreover, for both types of adjuvants, despite lower antibody titers, the protection to challenge given by the adjuvanted vaccine containing only 50% of the antigen load was equivalent to the protection given by the non-adjuvanted vaccine. These results demonstrate that the addition of relevant adjuvants can enhance the efficacy of the protection conferred to animals by live vaccines.

A lack of antibody formation against inactivated influenza virus after aerosol vaccination in presence or absence of adjuvantia

In the poultry industry, infections with avian influenza virus (AIV) can result in significant economic losses. The risk and the size of an outbreak might be restricted by vaccination of poultry. A vaccine that would be used for rapid intervention during an outbreak should be safe to use, highly effective after a single administration and be suitable for mass application. A vaccine that could be applied by spray or aerosol would be suitable for mass application, but respiratory applied inactivated influenza is poorly immunogenic and needs to be adjuvanted. We chose aluminum OH, chitosan, cholera toxin B subunit (CT-B), and Stimune as adjuvant for an aerosolized vaccine with inactivated H9N2. Each adjuvant was tested in two doses. None of the adjuvanted vaccines induced AIV-specific antibodies after single vaccination, measured 1 and 3 weeks after vaccination by aerosol, in contrast to the intramuscularly applied vaccine. The aerosolized vaccine did enter the chickens' respiratory tract as CT-B-specific serum antibodies were detected after 1 week in chickens vaccinated with the CT-B-adjuvanted vaccine. Chickens showed no adverse effects after the aerosol vaccination based on weight gain and clinical signs. The failure to detect AIV-specific antibodies might be due to the concentration of the inactivated virus.

Review of antimicrobial and antioxidative activities of chitosans in food

Interest in chitosan, a biodegradable, nontoxic, non-antigenic, and biocompatible biopolymer isolated from shellfish, arises from the fact that chitosans are reported to exhibit numerous health-related beneficial effects, including strong antimicrobial and antioxidative activities in foods. The extraordinary interest in the chemistry and application in agriculture, horticulture, environmental science, industry, microbiology, and medicine is attested by about 17,000 citations on this subject in the Scopus database. A special need exists to develop a better understanding of the role of chitosans in ameliorating foodborne illness. To contribute to this effort, this overview surveys and interprets our present knowledge of the chemistry and antimicrobial activities of chitosan in solution, as powders, and in edible films and coating against foodborne pathogens, spoilage bacteria, and pathogenic viruses and fungi in several food categories. These include produce, fruit juices, eggs and dairy, cereal, meat, and seafood products. Also covered are antimicrobial activities of chemically modified and nanochitosans, therapeutic properties, and possible mechanisms of the antimicrobial, antioxidative, and metal chelating effects. Further research is suggested in each of these categories. The widely scattered data on the multifaceted aspects of chitosan microbiology, summarized in the text and in 10 tables and 8 representative figures, suggest that low-molecular-weight chitosans at a pH below 6.0 presents optimal conditions for achieving desirable antimicrobial and antioxidative-preservative effects in liquid and solid foods. We are very hopeful that the described findings will be a valuable record and resource for further progress to improve microbial food safety and food quality.