Chitosan and anisodamine enhance the immersion immune efficacy of inactivated Elizabethkingia miricola vaccine in black spotted frogs

Black spotted frogs have rich nutrition and delicious meat, and its market consumption has increased year by year. However, outbreaks of the diseases have caused huge losses to the breeding industry. The crooked head disease caused by Elizabethkingia miricola (E. miricola) is highly contagious and lethal, and there is no effective treatment method. Vaccination is the most promising strategy to prevent infectious diseases. Immersion vaccination has attracted many researchers because of its simplicity of operation in preventing infectious diseases. In addition, immersion vaccines can be more effective when used with adjuvants. In this study, we prepared inactivated E. miricola with 0.3% formaldehyde, and the black spotted frogs were vaccinated by soaking in inactivated E. miricola vaccine, anisodamine + vaccine mixture, β-glucan + vaccine mixture, chitosan + vaccine mixture for 60 min. PBS was used as a control. After being challenged by E. miricola, the survival rate of anisodamine + vaccine (57%) and chitosan + vaccine group (63%) was significantly higher than that of the control group (17%). By analyzing pathological sections, we found that the chitosan + vaccine and anisodamine + vaccine groups protected the brain, eye, liver and kidney tissues of the black spotted frogs compared to the control group, which was consistent with the trend of survival rate. In addition, chitosan + vaccine and anisodamine + vaccine groups had better effects on LZM, TSOD and C3 in serum than control group. Meanwhile, the numbers of the percentage of leukocytes/haemocytes in the peripheral blood of immunized black spotted frogs increased. The anisodamine + vaccine group (5.3%) and chitosan + vaccine (5.38%) group were significantly higher than the blank control group (2.24%), which indicate that the two groups induced a more significant immune response and were more resistant to bacterial invasion. The tissue bacterial loads in liver, brain, kidney and eye were significantly lower in the anisodamine + vaccine and chitosan + vaccine groups than that of the control group. This study explored and demonstrated the good efficiency of chitosan and anisodamine as adjuvants for immunization by immersion and provided a reference for improving the efficiency of immunization by immersion.

Potential role of dietary chitosan nanoparticles against immunosuppression, inflammation, oxidative stress, and histopathological alterations induced by pendimethalin toxicity in Nile tilapia

A 21-days feeding screening period was conducted to highlight the protective efficacy of dietary chitosan nanoparticles (CSNPs) on pendimethalin (PD)-induced toxicity in Nile tilapia (Oreochromis niloticus). Hematology, non-specific immune response, the antioxidative enzymes [superoxide dismutase (SOD) and catalase (CAT), glutathione reduced (GSH), and glutathione peroxidase (GPx)] in the liver and anterior kidney, changes of pro-inflammatory cytokine genes [interleukins-8 (IL-8), interleukins-1β (IL-1β), and tumor necrosis-α (TNF-α)] in the anterior kidney and histopathological alterations were assessed. Fish (50 ± 7.5 g) were randomly assigned into four groups (Three replicates), the first group served as the negative control and fed on the control diet only, and the second group served as the positive control and fed on the control diet supplemented with CSNPs (1 g kg^-1 diet). The two other groups were exposed to 1/10 96-h LC₅₀ PD (0.5 mg L^-1) in rearing water and simultaneously fed the control diet alone or supplemented with CSNPs (1 g kg^-1 diet), respectively. Fish were fed on the experimental diets twice a day for 21 days. The results revealed that PD exposure caused a significant decline in the survival rate of the Nile tilapia, as well as in most of the hematological indices, respiratory burst activity, phagocytic activity, total immunoglobulin levels, lysozyme, and bactericidal activity. Additionally, PD toxicity markedly suppressed most of the antioxidative enzymatic activities in both tissues together with upregulation of immune genes (IL-8 and TNF-α); however, IL-1β expression remained unaffected. The histopathological results revealed marked pathological changes in spleen, liver and intestine with a notable decrease of intestinal goblet cells in PD-exposed groups. Conversely, CSNPs exerted protective effects through improving the above mentioned parameters. Thus, CSNPs supplementation exhibited defensive effects against PD toxicity in Nile tilapia that might provide an insight into the promising role of CSNPs as a potential immunomodulatory feed additive for tilapia in aquaculture.

Oral delivery of pVAX-OMP and pVAX-hly DNA vaccine using chitosan-tripolyphosphate (Cs-TPP) nanoparticles in Rohu, (Labeo rohita) for protection against Aeromonas hydrophila infection

The present study examines the effectiveness of DNA vaccine against Aeromonas hydrophila through oral route using chitosan-tripolyphosphate (Cs-TPP) nanoparticles encapsulation. The virulent gene of outer membrane protein (OMP) and hemolysin (hly) related to pathogenicity of A. hydrophila was used to construct a DNA vaccine using pVAX1, and the construct was named as pVAX-OMP and pVAX-hly DNA vaccines. The pVAX-OMP and pVAX-hly DNA vaccines were encapsulated by Cs-TPP nanoparticles and size measured by field emission scanning electron microscopy (FE-SEM). The encapsulation efficiency of Cs-TPP nanoparticles was found to be 79.6% for pVAX-OMP DNA and 82.3% for pVAX-hly DNA binding with Cs-TPP nanoparticles. The stability and invitro release profile of plasmid DNA was also determined after encapsulation using DNase and chitosanase. DNA vaccines distribution in tissues was investigated in fish fed with the pVAX-OMP, pVAX-hly and pVAX-OMP+pVAX-hly encapsulated in Cs-TPP nanoparticles and confirmed by PCR and multiplex PCR. The results suggest that Cs-TPP nanoparticles encapsulated DNA vaccine delivered into fish by feeding. After oral vaccination of Labeo rohita were challenged with A. hydrophila by intraperitoneal injection. Relatively, gene expression of c- and g-type lysozyme followed by pro- and anti-inflammatory cytokines (Interlukin-10 and Tumor Growth Factor β) was up-regulated in heart and kidney for pVAX-OMP+pVAX-hly vaccinated group. Moreover, fish fed with pVAX-OMP+pVAX-hly encapsulated in Cs-TPP nanoparticles had a significantly higher survival rate (76.2%) against A. hydrophila. This study concludes that pVAX-OMP and pVAX-hly DNA vaccines can be delivered orally using Cs-TPP nanoparticles for protection against A. hydrophilainfection.

Immunity and Protective Efficacy of Mannose Conjugated Chitosan-Based Influenza Nanovaccine in Maternal Antibody Positive Pigs

Parenteral administration of killed/inactivated swine influenza A virus (SwIAV) vaccine in weaned piglets provides variable levels of immunity due to the presence of preexisting virus specific maternal derived antibodies (MDA). To overcome the effect of MDA on SwIAV vaccine in piglets, we developed an intranasal deliverable killed SwIAV antigen (KAg) encapsulated chitosan nanoparticles called chitosan-based NPs encapsulating KAg (CS NPs-KAg) vaccine. Further, to target the candidate vaccine to dendritic cells and macrophages which express mannose receptor, we conjugated mannose to chitosan (mCS) and formulated KAg encapsulated mCS nanoparticles called mannosylated chitosan-based NPs encapsulating KAg (mCS NPs-KAg) vaccine. In MDA-positive piglets, prime-boost intranasal inoculation of mCS NPs-KAg vaccine elicited enhanced homologous (H1N2-OH10), heterologous (H1N1-OH7), and heterosubtypic (H3N2-OH4) influenza virus-specific secretory IgA (sIgA) antibody response in nasal passage compared to CS NPs-KAg vaccinates. In vaccinated upon challenged with a heterologous SwIAV H1N1, both mCS NPs-KAg and CS NPs-KAg vaccinates augmented H1N2-OH10, H1N1-OH7, and H3N2-OH4 virus-specific sIgA antibody responses in nasal swab, lung lysate, and bronchoalveolar lavage (BAL) fluid; and IgG antibody levels in lung lysate and BAL fluid samples. Whereas, the multivalent commercial inactivated SwIAV vaccine delivered intramuscularly increased serum IgG antibody response. In mCS NPs-KAg and CS NPs-KAg vaccinates increased H1N2-OH10 but not H1N1-OH7 and H3N2-OH4-specific serum hemagglutination inhibition titers were observed. Additionally, mCS NPs-KAg vaccine increased specific recall lymphocyte proliferation and cytokines IL-4, IL-10, and IFNγ gene expression compared to CS NPs-KAg and commercial SwIAV vaccinates in tracheobronchial lymph nodes. Consistent with the immune response both mCS NPs-KAg and CS NPs-KAg vaccinates cleared the challenge H1N1-OH7 virus load in upper and lower respiratory tract more efficiently when compared to commercial vaccine. The virus clearance was associated with reduced gross lung lesions. Overall, mCS NP-KAg vaccine intranasal immunization in MDA-positive pigs induced a robust cross-reactive immunity and offered protection against influenza virus.

Efficacy of chitosan-based nanoparticle vaccine administered to broiler birds challenged with Salmonella

Two experiments were conducted to evaluate the immune response of broilers vaccinated with Salmonella chitosan-nanoparticle (CNP) vaccine and challenged with Salmonella. The Salmonella CNP vaccine was synthesized with Salmonella enterica outer membrane proteins (OMPs) and flagellin proteins. In Experiment I, birds were orally gavaged with PBS or 500, 1000, or 2000μg of CNP vaccine 1 and 7d-of-age. At 14d-of-age, birds were orally challenged with 1 X 10⁵ CFU/bird of live S. Enteritidis (SE). Macrophage-nitrite production 11d-post-challenge was higher (P<0.05) in the 500μg group when compared to the control. At d14 (8h-post-challenge), broilers vaccinated with 1000μg CNP had higher (P<0.05) serum anti-OMPs IgG and IgA and cloacal anti-OMP IgA amounts. At 11d-post-challenge, birds vaccinated with 1000μg CNP vaccine had greater (P<0.05) bile anti-OMP and anti-flagellin IgA amounts. At 11d-post-challenge, birds administered 1000μg CNP vaccine has increased (P<0.05) IL-1β and IL-10 mRNA in cecal tonsils. In Experiment II, birds were orally gavaged with PBS or 1000μg CNP or a live commercial vaccine at 1 and 7d-of-age. At 14d-of-age, birds were orally challenged with 1 X 10⁵ CFU/bird of live SE or S. Heidelberg (SH). Birds vaccinated with CNP showed higher (P<0.05) serum anti-OMPs IgG amounts at 8h-post-challenge. At 4d-post-SH challenge, birds vaccinated with CNP had higher (P<0.05) bile anti-flagellin IgA amounts. CNP decreased (P<0.05) anti-OMPs IgG levels in serum at 2d-post-SE challenge and 4d-post-SH or SE challenge. Salmonella Enteritidis loads in cecal content at 2d-post-challenge was decreased (P<0.05) by 65.9% in birds vaccinated with CNP, when compared to the control. Chitosan-nanovaccine had no adverse effects on bird’s production performance. In conclusion, 1000μg CNP vaccine can induce a specific immune response against Salmonella and has the potential to mitigate SE cecal colonization in broiler birds.

Immune effect of Vibrio harveyi formalin-killed cells vaccine combined with chitosan oligosaccharide and astragalus polysaccharides in ♀Epinephelus fuscoguttatus×♂Epinephelus lanceolatus

Vibrio harveyi is the pathogen causing vibriosis in marine-cultured animals, leading to massive deaths in farmed grouper around the world. It is urgent to develop an effective vaccine to prevent vibriosis. In the previous study, we developed a V. harveyi formalin-killed cells vaccine (FKC), and sought an effective adjuvant for enhancing the immune efficacy of vaccine. In this study, we aimed to evaluate the immune responses and protective effect of FKC combined with chitosan oligosaccharide (COS) or Astragalus polysaccharides (APS) in the pearl gentian grouper♀Epinephelus fuscoguttatus × ♂E. lanceolatus. The results indicated the vaccine triggered a remarkably higher expression levels of IL-1β, IL-16, TNF-α, MHC-Iα and IgM in the kidney and spleen of groupers post-vaccination. Antibody titers, lysozyme, catalase, superoxide dismutase and total protein were significantly elevated in the vaccinated fish compared with those in the control. The experimental groupers were challenged intraperitoneally by V. harveyi at 35 d post-vaccination, and the relative percentage of survival (RPS) of group FKC + COS, FKC + APS, COS, APS and FKC were 80%, 72%, 52%, 47% and 55%, respectively. These results demonstrated COS and APS was the potential adjuvants for FKC against V. harveyi in aquaculture.

Induction of systemic immunity through nasal-associated lymphoid tissue (NALT) of mice intranasally immunized with Brucella abortus malate dehydrogenase-loaded chitosan nanoparticles

Infection with Brucella abortus causes contagious zoonosis, brucellosis, and leads to abortion in animals and chronic illness in humans. Chitosan nanoparticles (CNs), biocompatible and nontoxic polymers, acts as a mucosal adjuvant. In our previous study, B. abortus malate dehydrogenase (Mdh) was loaded in CNs, and it induced high production of pro-inflammatory cytokines in THP-1 cells and systemic IgA in BALB/C mice. In this study, the time-series gene expression analysis of nasal-associated lymphoid tissue (NALT) was performed to identify the mechanism by which Mdh affect the target site of nasal immunization. We showed that intranasal immunization of CNs-Mdh reduced cell viability of epithelial cells and muscle cells at first 1 h, then induced cellular movement of immune cells such as granulocytes, neutrophils and lymphocytes at 6h, and activated IL-6 signaling pathway at 12h within NALT. These activation of immune cells also promoted signaling pathway for high-mobility group box 1 protein (HMGB1), followed by the maturation of DCs required for mucosal immunity. The CNs also triggered the response to other organism and inflammatory response, showing it is immune-enhancing adjuvant. The ELISA showed that significant production of specific IgA was detected in the fecal excretions and genital secretions from the CNs-Mdh-immunized group after 2 weeks-post immunization. Collectively, these results suggest that B. abortus Mdh-loaded CNs triggers activation of HMGB1, IL-6 and DCs maturation signaling within NALT and induce production of systemic IgG and IgA.

Chitosan and anisodamine improve the immune efficacy of inactivated infectious spleen and kidney necrosis virus vaccine in Siniperca chuatsi

Siniperca chuatsi is an economically important fish in China, but infectious spleen and kidney necrosis virus (ISKNV) causes high mortality and significant economic losses. Currently, vaccination is the most promising strategy to prevent infectious diseases, while adjuvant can effectively enhance immune responses. In this study, inactivated ISKNV vaccine was prepared, then poly (I:C), chitosan, anisodamine and ims1312 were used as adjuvants to evaluate the effect on the immune responses and ISKNV replication. Chitosan could strongly boost the protection of liver and spleen tissues by pathological sections. In serum, poly (I:C) and chitosan group had protective effect on catalase, acid phosphatase, blood urea nitrogen. mRNA expressions showed these adjuvants induced the cytokines of early immune responses (TNF-α, Viperin) in both spleen and mesonephron by real time quantitative RT-PCR assays. Meanwhile, poly (I:C), chitosan and anisodamine were significantly improved the antiviral function and inhibited ISKNV replication. Chitosan and anisodamine played a significantly protective role in the immune protective rate test. The results indicated that all the four adjuvants are valid in the inactivated ISKNV vaccine, and chitosan is recommended preferentially. The present study provides reference for other animal vaccine adjuvants.

Chitosan Acetylation Degree Influences the Physical Properties of Polysaccharide Nanoparticles: Implication for the Innate Immune Cells Response

The aim of the present contribution is twofold as it reports (i) on the role played by chitosan acetylation degree for the stability of nanoparticles (NPs) formed with hyaluronan and (ii) on the effect of the interaction of such NPs with immune cells. Chitosans with similar viscosity-average molecular weight, [Formula: see text], (i.e., 200 000) and different fractions of acetylated units ( F_A) together with low-molecular-weight hyaluronan were chosen for developing a select library of formulations via electrostatic complex coacervation. The resulting NPs were analyzed in terms of size, polydispersity, surface charge, and stability in physiological-mimicked media by dynamic light scattering. Only medium acetylated chitosan ( F_A = 0.16) guaranteed the stability of NPs. To explore the effect of NPs interaction with immune cells, the release of proinflammatory cytokines and the reactive oxygen species production by human macrophages and neutrophils, respectively, were evaluated. Strikingly, a structure-function relationship emerged, showing that NPs made of chitosans with F_A = 0.02, 0.25, 0.46, and 0.63 manifested a proinflammatory activity, linked to the instability of the system. Conversely, NPs made of chitosan with F_A = 0.16 neither modified the functional response of macrophages nor that of neutrophils. Of note, such NPs were found to possess additional properties potentially advantageous in applications such as delivery of therapeutics to target inflamed sites: (i) they are devoid of cytotoxic effects, (ii) they avoid engulfment during the early stage of interaction with macrophages, and (iii) they are muco-adhesive, thereby providing for site-specificity and long-residence effects.

Poly-Gamma-Glutamic Acid (γ-PGA)-Based Encapsulation of Adenovirus to Evade Neutralizing Antibodies

In recent years, there has been an increasing interest in oncolytic adenoviral vectors as an alternative anticancer therapy. The induction of an immune response can be considered as a major limitation of this kind of application. Significant research efforts have been focused on the development of biodegradable polymer poly-gamma-glutamic acid (γ-PGA)-based nanoparticles used as a vector for effective and safe anticancer therapy, owing to their controlled and sustained-release properties, low toxicity, as well as biocompatibility with tissue and cells. This study aimed to introduce a specific destructive and antibody blind polymer-coated viral vector into cancer cells using γ-PGA and chitosan (CH). Adenovirus was successfully encapsulated into the biopolymer particles with an encapsulation efficiency of 92% and particle size of 485 nm using the ionic gelation method. Therapeutic agents or nanoparticles (NPs) that carry therapeutics can be directed specifically to cancerous cells by decorating their surfaces using targeting ligands. Moreover, in vitro neutralizing antibody response against viral capsid proteins can be somewhat reduced by encapsulating adenovirus into γ-PGA-CH NPs, as only 3.1% of the encapsulated adenovirus was detected by anti-adenovirus antibodies in the presented work compared to naked adenoviruses. The results obtained and the unique characteristics of the polymer established in this research could provide a reference for the coating and controlled release of viral vectors used in anticancer therapy.

Preparation, characterization and evaluation of the immune effect of alginate/chitosan composite microspheres encapsulating recombinant protein of Streptococcus iniae designed for fish oral vaccination

Streptococcus iniae has caused serious harm to the fish farming industry in recent years. Vaccination is a potential approach for preventing and controlling disease, being oral vaccination the most suitable vaccination route in fish. Alginate and chitosan microspheres have been widely used as controlled release systems for oral vaccination in fish. In this study, we prepared and characterized alginate/chitosan composite microspheres encapsulating the recombinant protein serine-rich repeat (rSrr) of S. iniae. We evaluated effect of these microspheres on the immune system of channel catfish. The microsphere preparation conditions were optimized by Response Surface Method and target microspheres were obtained under 1.68% alginate (w/v), the W/O ratio 3.6:7.4 (liquid paraffin with 4% Span 80, v/v) with stirring at 1000 rpm, 9.64% CaCl₂ (w/v) and 0.95% chitosan (w/v) with an encapsulation efficiency of 92.38%. The stability and safety of rSrr-microspheres were evaluated in vitro and in vivo, respectively. Furthermore, compared with control group, oral vaccination with rSrr-microspheres induced higher serum antibody titers, higher lysozyme activity, higher total protein and higher expression of immune-related genes, and resulted in higher relative percent survival (RPS) with the value of 60% for channel catfish against S.iniae infection. Our results thus indicate that alginate/chitosan microspheres encapsulating rSrr can be used as oral vaccine for channel catfish, providing efficient immunoprotection against S. iniae infection.

Immunoadjuvant potential of cross-linked dextran microspheres mixed with chitosan nanospheres encapsulated with tetanus toxoid

CONTEXT

Nasal mucosa is a desirable route for mucosal vaccine delivery. Mucosal co-administration of chitosan nanoparticles with absorption enhancers such as cross-linked dextran microspheres (CDM, Sephadex^®) is a promising antigen delivery system.

OBJECTIVE

In the current study, the chitosan nanospheres loaded with tetanus toxoid (CHT:TT NPs) was prepared and characterized. The immune responses against tetanus toxoid after nasal administration of CHT:TT NPs alone or mixed with CDM were also determined.

MATERIALS AND METHODS

Chitosan nanospheres were prepared by ionic gelation method. Particle size, releasing profile and antigen stability were evaluated by dynamic light scattering, diffusion chamber and SDS-PAGE methods, respectively. Rabbits were nasally immunized with different formulations loaded with 40 Lf TT. After three times immunizations with 2 weeks intervals, sera IgG titres and nasal lavage sIgA titres were determined.

RESULTS

Mean size of CHT NPs and CHT:TT NPs were 205 ± 42 nm and 432 ± 85 nm, respectively. The release profile showed that 42.4 ± 10.5% of TT was released after 30 min and reached to a steady state after 1.5 h. Stability of encapsulated TT in nanospheres was confirmed by SDS-PAGE. The antibody titres showed that CHT:TT NPs-induced antibody titres were higher than TT solution. CHT NPs mixed with CDM induced the systemic IgG and nasal lavage sIgA titres higher than intranasal administration of TT solution (p < 0.001).

DISCUSSION AND CONCLUSION

As the results indicated, these CHT:TT NPs when co-administered with CDM were able to induce more immune responses and have the potential to be used in mucosal immunization.

The Positive Correlation of the Enhanced Immune Response to PCV2 Subunit Vaccine by Conjugation of Chitosan Oligosaccharide with the Deacetylation Degree

Chitosan oligosaccharides (COS), the degraded products of chitosan, have been demonstrated to have versatile biological functions. In primary studies, it has displayed significant adjuvant effects when mixed with other vaccines. In this study, chitosan oligosaccharides with different deacetylation degrees were prepared and conjugated to porcine circovirus type 2 (PCV2) subunit vaccine to enhance its immunogenicity. The vaccine conjugates were designed by the covalent linkage of COSs to PCV2 molecules and administered to BALB/c mice three times at two-week intervals. The results indicate that, as compared to the PCV2 group, COS-PCV2 conjugates remarkably enhanced both humoral and cellular immunity against PCV2 by promoting lymphocyte proliferation and initiating a mixed T-helper 1 (Th1)/T-helper 2 (Th2) response, including raised levels of PCV2-specific antibodies and an increased production of inflammatory cytokines. Noticeably, with the increasing deacetylation degree, the stronger immune responses to PCV2 were observed in the groups with COS-PCV2 vaccination. In comparison with NACOS (chitin oligosaccharides)-PCV2 and LCOS (chitosan oligosaccharides with low deacetylation degree)-PCV2, HCOS (chitosan oligosaccharides with high deacetylation degree)-PCV2 showed the highest adjuvant effect, even comparable to that of PCV2/ISA206 (a commercialized adjuvant) group. In summary, COS conjugation might be a viable strategy to enhance the immune response to PCV2 subunit vaccine, and the adjuvant effect was positively correlated with the deacetylation degree of COS.

The effects of CpG-ODNs and Chitosan adjuvants on the elicitation of immune responses induced by the HIV-1-Tat-based candidate vaccines in mice

HIV1-Tat-based vaccines could elicit broad, durable and neutralizing immune responses and are considered as potential AIDS vaccines. The present study aims to formulate CpG-ODNs adjuvant and Chitosan with Tat protein to enhance the immunogenicity of HIV-1-Tat-based candidate vaccines and to investigate their efficacies in mice. To this end, we added CpG-ODNs, Chitosan and Alum as adjuvants to the Tat-based candidate vaccine formulations. Then, we compared frequency and magnitude of both humoral and cellular immune responses from mice immunized with the adjuvant-formulated Tat candidate vaccines against those obtained from mice immunized with recombinant Tat protein alone. Mice were subcutaneously immunized three times at 2-week intervals with the candidate vaccines. Measurements of anti-Tat immune responses showed that all vaccinated groups had a good immunity compared to the control groups and developed high levels of both humoral and cellular responses. However, immunized mice with CpG-ODNs, and Chitosan-adjuvanted Tat vaccines elicited stronger T-cell responses (both humoral and cellular immunity) compared to the others. These data suggest that co-administration of recombinant Tat protein with CpG-ODNs and Chitosan may serve as a potential formulation for enhancing of the Tat vaccine-induced immunity and might have effects on shaping Th polarization induced by HIV1-Tat protein vaccines.

An oral chitosan DNA vaccine against nodavirus improves transcription of cell-mediated cytotoxicity and interferon genes in the European sea bass juveniles gut and survival upon infection

Vaccines for fish need to be improved for the aquaculture sector, with DNA vaccines and the oral administration route providing the most promising improvements. In this study, we have created an oral chitosan-encapsulated DNA vaccine (CP-pNNV) for the nodavirus (NNV) in order to protect the very susceptible European sea bass (Dicentrarchus labrax). Our data show that the oral CP-pNNV vaccine failed to induce serum circulating or neutralizing specific antibodies (immunoglobulin M) or to up-regulate their gene expression in the posterior gut. However, the vaccine up-regulated the expression of genes related to the cell-mediated cytotoxicity (CMC; tcrb and cd8a) and the interferon pathway (IFN; ifn, mx and ifng). In addition, 3 months after vaccination, challenged fish showed a retarded onset of fish death and lower cumulative mortality with a relative survival of 45%. Thus, we created a chitosan-encapsulated DNA vaccine against NNV that is partly protective to European sea bass juveniles and up-regulates the transcription of genes related to CMC and IFN. However, further studies are needed to improve the anti-NNV vaccine and to understand its mechanisms.

Protective effect of a recombinant VHSV-G vaccine using poly(I:C) loaded nanoparticles as an adjuvant in zebrafish (Danio rerio) infection model

There is a constant need to increase the efficiency of vaccines in the aquaculture industry. Although several nano-based vaccine formulations have been reported, to the best of our knowledge so far only one of them have been implemented in the industry. Here we report on chitosan-poly(I:C) nanoparticles (NPs) that could be used as a non-specific adjuvant in antiviral vaccines in aquaculture. We have characterized the physical parameters of the NPs, studied the in vivo and in vitro bio-distribution of fluorescent NPs and verified NP uptake by zebrafish leucocytes. We used the zebrafish model to test the protective efficiency of the recombinant glycoprotein G (rgpG) of VHSV compared to inactivated whole virus (iV) against VHSV using NPs as an adjuvant in both formulations. In parallel we tested free poly(I:C) and rgpG (pICrgpG), and free chitosan and rgpG (CSrgpG) vaccine formulations. While the iV group (with NP adjuvant) provided the highest overall survival, all vaccine formulations with poly(I:C) provided a significant protection against VHSV; possibly through an early induction of an anti-viral state. Our results suggest that chitosan-poly(I:C) NPs are a promising adjuvant candidate for future vaccine formulations.

Chitosan Mediates Germling Adhesion in Magnaporthe oryzae and Is Required for Surface Sensing and Germling Morphogenesis

The fungal cell wall not only plays a critical role in maintaining cellular integrity, but also forms the interface between fungi and their environment. The composition of the cell wall can therefore influence the interactions of fungi with their physical and biological environments. Chitin, one of the main polysaccharide components of the wall, can be chemically modified by deacetylation. This reaction is catalyzed by a family of enzymes known as chitin deacetylases (CDAs), and results in the formation of chitosan, a polymer of β1,4-glucosamine. Chitosan has previously been shown to accumulate in the cell wall of infection structures in phytopathogenic fungi. Here, it has long been hypothesized to act as a 'stealth' molecule, necessary for full pathogenesis. In this study, we used the crop pathogen and model organism Magnaporthe oryzae to test this hypothesis. We first confirmed that chitosan localizes to the germ tube and appressorium, then deleted CDA genes on the basis of their elevated transcript levels during appressorium differentiation. Germlings of the deletion strains showed loss of chitin deacetylation, and were compromised in their ability to adhere and form appressoria on artificial hydrophobic surfaces. Surprisingly, the addition of exogenous chitosan fully restored germling adhesion and appressorium development. Despite the lack of appressorium development on artificial surfaces, pathogenicity was unaffected in the mutant strains. Further analyses demonstrated that cuticular waxes are sufficient to over-ride the requirement for chitosan during appressorium development on the plant surface. Thus, chitosan does not have a role as a 'stealth' molecule, but instead mediates the adhesion of germlings to surfaces, thereby allowing the perception of the physical stimuli necessary to promote appressorium development. This study thus reveals a novel role for chitosan in phytopathogenic fungi, and gives further insight into the mechanisms governing appressorium development in M.oryzae.

Magnaporthe oryzae is a filamentous fungal pathogen which causes devastating crop losses in rice. Successful invasion of the host is dependent upon the ability of the fungus to remain undetected by the innate immune system of the plant, which recognizes conserved components of the fungal cell wall, such as chitin. Previous studies have demonstrated that infection-related changes in cell wall composition are necessary to allow the fungus to remain undetected during infection. One such change that has long been hypothesized to have a role as a 'stealth mechanism' is the deacetylation of the polysaccharide chitin by enzymes known as chitin deacetylases. The deacetylation of chitin produces a polysaccharide known as chitosan, which has previously been shown to accumulate specifically on infection structures in plant pathogenic fungi. However, in this study, we show that germling-localized chitosan is not required for pathogenicity, arguing against a role as a 'stealth mechanism' at this stage. Instead, chitosan is required for the development of the appressorium, a critical fungal infection structure required for the penetration of plant cells. This requirement can be attributed to chitosan mediating the adhesion of germlings to surfaces, which is required for the perception of physical stimuli.

Effect of Chitosan Properties on Immunoreactivity

Chitosan is a widely investigated biopolymer in drug and gene delivery, tissue engineering and vaccine development. However, the immune response to chitosan is not clearly understood due to contradicting results in literature regarding its immunoreactivity. Thus, in this study, we analyzed effects of various biochemical properties, namely degree of deacetylation (DDA), viscosity/polymer length and endotoxin levels, on immune responses by antigen presenting cells (APCs). Chitosan solutions from various sources were treated with mouse and human APCs (macrophages and/or dendritic cells) and the amount of tumor necrosis factor-α (TNF-α) released by the cells was used as an indicator of immunoreactivity. Our results indicate that only endotoxin content and not DDA or viscosity influenced chitosan-induced immune responses. Our data also indicate that low endotoxin chitosan (<0.01 EU/mg) ranging from 20 to 600 cP and 80% to 97% DDA is essentially inert. This study emphasizes the need for more complete characterization and purification of chitosan in preclinical studies in order for this valuable biomaterial to achieve widespread clinical application.

[Effects of cell-mediated immunity induced by intramuscular chitosan-pJME/ GM-CSF nano-DNA vaccine in BAlb/c mice]

This study aimed to investigate the immune adjuvant effect and mechanism induced by chitosan nanoparticles carrying pJME/GM-CSF. In this study, plasmid DNA (pJME/GM-CSF) was encapsulated in chitosan to prepare chitosan-pJME/GM-CSF nanoparticles using a complex coacervation process. Immunohistochemistry was used to detect the type of infiltrating cells at the site of intramuscular injection. The phenotype and functional changes of splenic DCs were measured by flow cytometry after different immunogens were injected intramuscularly. The killing activity of CTLs was assessed using the lactate dehydrogenase (LDH) release assay. The preparation of chitosan-pJME/GM-CSF nanoparticles matched the expected theoretical results. Our results also found that, after pJME/GM-CSF injection, the incoming cells were a mixture of macrophages, neutrophils, and immature DCs. Meanwhile, pJME/GM-CSF increased the expression of MHC class II molecules on splenic DCs, and enhanced their Ag capture and presentation functions. Cell-mediated immunity was induced by the vaccine. Furthermore, chitosan-pJME/GM-CSF nanoparticles outperformed the administration of standard pJME/GM-CSF in terms of DC recruitment, antigen processing and presentation, and vaccine enhancement. These findings reveal that chitosan could be used as delivery vector for DNA vaccine intramuscular immunizations, and enhance pJME/GM-CSF-induced cellular immune responses.

[Study on adjuvant effect of oral recombinant subunit vaccine formulated with chitosan against human enterovirus 71]

To evaluate the adjuvant effect of recombinant enterovirus 71 (EV71) subunit vaccine formulated with chitosan, rabbits were orally immunized with recombinant VP1 (rVP1) or rVP1 mixed with chitosan adjuvant. Levels of virus-specific IgG and IgA antibodies in sera, mucosal wash buffer (intestine, nasal cavity, and lung), and feces were determined by indirect enzyme-linked immunosorbent assay (ELISA). The titers of neutralizing antibodies against EV71 were determined using cytopathic effect-based neutralizing assay, and levels of cytokines (IFN-gamma and IL-4) secreted from in vitro-cultured rabbit splenic lymphocytes under antigen stimulation were also determined by ELISA. Results showed that immunization with rVP1 alone could only induce low levels of serum IgG and mucosal IgA, while rVP1 combined with chitosan adjuvant were able to induce significantly higher levels of antibodies, rVP1 can only induce neutralizing antibodies when used in combination with chitosan. Levels of IFN-gamma and IL-4 in the group immunized with rVP1 plus chitosan were significantly higher than those in the group immunized with rVP1 only or those in the control groups. Our study lays the foundation for development of oral VP1 vaccine against EV71 infection.

Enhanced antitumor activity of the photosensitizer meso-Tetra(N-methyl-4-pyridyl) porphine tetra tosylate through encapsulation in antibody-targeted chitosan/alginate nanoparticles

meso-Tetra(N-methyl-4-pyridyl) porphine tetra tosylate (TMP) is a photosensitizer that can be used in photodynamic therapy (PDT) to induce cell death through generation of reactive oxygen species in targeted tumor cells. However, TMP is highly hydrophilic, and therefore, its ability to accumulate intracellularly is limited. In this study, a strategy to improve TMP uptake into cells has been investigated by encapsulating the compound in a hydrogel-based chitosan/alginate nanoparticle formulation. Nanoparticles of 560 nm in diameter entrapping 9.1 μg of TMP per mg of formulation were produced and examined in cell-based assays. These particles were endocytosed into human colorectal carcinoma HCT116 cells and elicited a more potent photocytotoxic effect than free drug. Antibodies targeting death receptor 5 (DR5), a cell surface apoptosis-inducing receptor up-regulated in various types of cancer and found on HCT116 cells, were then conjugated onto the particles. The conjugated antibodies further enhanced uptake and cytotoxic potency of the nanoparticle. Taken together, these results show that antibody-conjugated chitosan/alginate nanoparticles significantly enhanced the therapeutic effectiveness of entrapped TMP. This novel approach provides a strategy for providing targeted site-specific delivery of TMP and other photosensitizer drugs to treat colorectal tumors using PDT.

[Study of immunogenicity and protective efficacy of a novel inactivated vaccine with chitosan against influenza A/H1N1/2009]

AIM

Study of immunogenicity and protective efficacy of a novel inactivated vaccine with chitosan against influenza A/H1N1/2009.

MATERIALS AND METHODS

Influenza virus A/California/7/2009 (H1N1) strain was used in the study. Mice were immunized twice (21 day interval) with experimental samples of inactivated influenza vaccine: No. 1--without the addition of chitosan, No. 2--with addition of chitosan. The blood was obtained 21 days after the first and 10 days after the second immunization with the vaccines and was treated with RDE. Antibody levels were evaluated in HI reaction.

RESULTS

HI reaction method showed that antibody titers induced after immunization of vaccine No. 2 were higher than those induced after immunization with vaccine No. 1. Evaluation of protective efficacy of the vaccines against an experimental form of influenza infection in mice showed that after immunization with vaccine that does not contain chitosan the level of virus accumulation does not differ from the control statistically significantly (p < or = 0.05), at the same time the level of virus accumulation in the lungs of infected animals immunized with chitosan containing vaccine significantly (significantly with 95% probability) decreased by an average 3.01g when compared with control.

CONCLUSION

Comparative analysis of immunogenicity and protective efficacy of experimental samples of inactivated influenza vaccine against influenza A/H 1N1/2009 showed that the vaccine with the addition of chitosan stimulates the formation of a higher immune response and promotes a more significant suppression of influenza A infectious agent reproduction in the lung target-organ.

Anti-inflammatory effects of low-molecular weight chitosan oligosaccharides in IgE-antigen complex-stimulated RBL-2H3 cells and asthma model mice

The anti-inflammatory effects of low-molecular weight chitosan oligosaccharides (LM-COS) prepared from high-molecular weight chitosan by enzymatic digestion were investigated against allergic reaction and allergic asthma in vivo and in vitro. Allergic asthma is an inflammatory disease of the airways associated with enhanced degranulation and cytokine generation. The LM-COS (<1 kDa), consisting of glucosamine (GlcN)(n), n=3-5, were capable of inhibiting both antigen-stimulated degranulation and cytokine generation in rat basophilic leukemia RBL-2H3 cells. The protective effect of LM-COS against ovalbumin (OVA)-induced lung inflammation in asthma model mice was also examined. Oral administration of LM-COS (16 mg/kg body weight/day) resulted in a significant reduction in both mRNA and protein levels of interleukin (IL)-4, IL-5, IL-13, tumor necrosis factor (TNF)-α in the lung tissue and bronchoalveolar lavage fluid (BALF); The protein levels of IL-4, IL-13 and TNF-α in BALF were decreased by 5.8-fold, 3.0-fold and 9.9-fold, respectively, compared to those in the OVA-sensitized/challenged asthma control group. These results suggest that the oral administration of LM-COS is effective in alleviating the allergic inflammation in vivo and thus can be a good source material for the development of a potent therapeutic agent against mast cell-mediated allergic inflammatory responses and airway inflammation in allergic inflammatory diseases, including asthma.

Thermal-sensitive hydrogel as adjuvant-free vaccine delivery system for H5N1 intranasal immunization

For H5N1 influenza immunization, we developed a thermal-sensitive hydrogel as intranasal vaccine delivery system, which was formulated with N-[(2-hydroxy-3-trimethylammonium) propyl] chitosan chloride (HTCC) and α, β-glycerophosphate (α, β-GP). The flowing solution of HTCC/GP under room temperature could gelate rapidly at body temperature, which significantly prolonged the H5N1 split antigen residence time in nasal cavity. This system also enhanced the transepithelial transport via the paracellular routes due to the disorganization of ZO-1 protein in nasal epithelial tissue. In comparison to naked H5N1 split antigen and MF59 adjuvanted antigen, as designed hydrogel/H5N1 vaccine induced greater antigen-specific systemic immune responses and mucosal IgA immunity without adjuvants. Furthermore, a boosted cellular and humoral response was also obtained by examination of IFN-γ and IL-4 cytokines, respectively. In addition, hydrogel based formulation promoted the antigen-specific CD8(+) T cell immune memory as determined by the proportion of central and effector memory CD8(+) T cells in nasal associated lymphoid tissue (NALT). These results demonstrate that the HTCC hydrogel has potential as an adjuvant-free platform for H5N1 split antigen intranasal vaccination.

Preliminary characterization of N-trimethylchitosan as a nanocarrier for malaria vaccine

BACKGROUND & OBJECTIVES

With the current snags from the use of Artemisinin - combination therapies (ACTs) in malaria treatment in addition to fear of cross- resistance to unrelated drugs, raising the immunocompetence of individuals in malaria endemic areas by vaccination is the best approach to malaria - free world.

METHODS

Water - soluble cationic derivative, N, N, N- trimethylchitosan (TMC) was synthesized from chitosan. Nanoparticles of the TMC were prepared in various media [milliQ water, Na2CO3 (pH 10.92), Na2HPO4 (PBS, pH 9.01 and alhydrogel® ] which were characterized as adjuvants for possible vaccine delivery. The nanoparticles were characterized for particle size, surface charge and morphology using microscopy (Phase contrast microscope and Confocal laser scanning microscope), and Malvern zetasizer Nano - ZS. Time - resolved particle size analysis was performed after one month storage of the TMC nanoparticles at 4°C.

RESULTS

The result of the study showed that PBS was the best medium that produced cationic, monodispersed and stable TMC nanoparticles of < nm forming a compatibly homogeneous system even upon storage. Details of the polyelectrolyte - doped nanoparticles in PBS showed clear coatings due to Sodium poly (styrene sulfonate) [PSS, MW ~70 kDa] at the periphery of the particles and a fluorescent core with some tiny central hollow cavities implying that the nanoparticles can either entrap the vaccine candidate into the hollow cavities or adsorb them unto the surface of the peripheral polyelectrolyte coatings.

INTERPRETATION & CONCLUSION

This preliminary study established that TMC has the desired qualities for the intending antigen delivery. Further research regarding the biological activity of this TMC is indicated.

[Enhancing the immunogenicity of inactivated polio vaccines with chitosan used as an adjuvant]

Addition of chitosan to inactivated trivalent polio vaccine or inactivated preparations of attenuated poliomyelitis viruses (Sabin strains) significantly increases immunogenicity of these inactivated poliomyelitis virus preparations. High neutralizing antibody titers are detected after two immunizations of mice and a single immunization of rats, as well as when the antigen dose was reduced by 4 times. Addition of chitosan as an adjuvant significantly induces cellular immunity.

Immunostimulatory properties of glycated chitosan

Glycated chitosan (GC) is a new compound derived from chitosan by attaching galactose molecules to the chitosan molecules. GC was designed for immune stimulations in combination with phototherapies in the cancer treatment. The future clinical applications require a thorough understanding of the properties of GC. Murine macrophage cells (RAW264.7) were used to investigate NO formation and TNFα secretion stimulated by GC. Murine mammary tumor cells (EMT6) were treated in vitro and in vivo by laser irradiation with 980 nm in combination with GC stimulation. Here is the first in a series of studies designed to understand the immunological mechanisms of GC. Our in vitro results show that GC could enter into macrophages to stimulate NO generation and TNFα secretion. GC could further enhance the TNFα secretion of macrophages stimulated by laser treated tumor cells. Our in vivo results also show immunological effects of GC, particularly in inducing tumor-specific immune responses. Our results indicated that GC was a strong immunological stimulant for cancer treatment, particularly when combined with laser phototherapies.

[Increase of immunogenicity of cold-adapted influenza vaccine by using adjuvant]

AIM

To assess increase of protective efficacy of live cold-adapted (ca) influenza vaccine after addition of adjuvant chitozan.

MATERIALS AND METHODS

Used viruses: ca donor of attenuation A/Krasnodar/101/35/59 (H2N2) and epidemic strain A/Krasnodar/101/59 (H2N2); as an adjuvant--derivative of chitozan and microparticles of chitozan. Experiments were performed in outbred mice. Protective effect of immunization was measured by intranasal challenge by virulent strain of virus. Immune response was assessed by ELISA and indirect hemagglutination inhibition assay.

RESULTS

During intranasal immunization of mice with intact CA donor of attenuation A/Krasnodar/101/35/59 (H2N2) addition of 1% solution of chitozan glutamate to vaccine material resulted in increased serum IgG in immunized mice and protective effect of immunization. Addition of adjuvant to ca donor strain did not influence on its ts-characteristic. It was shown that inactivated with ultraviolet radiation ca donor strain in combination with chitozan did not protect against infection caused by virulent strain A/Krasnodar/101/59, whereas the same doses of intact ca donor strain with chitozan were protective. Chitozan did not enhance replication of donor strain in upper respiratory tract of mice.

CONCLUSION

Obtained data demonstrate that chitozan as a mucous-adhesive adjuvant could increase efficacy of live ca influenza vaccine.

Nitric oxide is involved in chitosan-induced systemic resistance in pearl millet against downy mildew disease

BACKGROUND

The nature and durability of resistance offered by chitosan and the involvement of nitric oxide (NO) in chitosan-induced defence reactions in pearl millet against downy mildew disease were investigated.

RESULTS

It had previously been reported that chitosan seed priming protected pearl millet plants against downy mildew disease. Further elucidation of the mechanism of resistance showed that chitosan seed priming protects the plants systemically. A minimum 4 day time gap is required between the chitosan treatment and pathogen inoculation for maximum resistance development, and it was found to be durable. Chitosan seed priming elevated NO accumulation in pearl millet seedlings, beginning from 2 h post-inoculation, and it was found to be involved in the activation of early defence reactions such as hypersensitive reaction, callose deposition and PR-1 protein expression. Pretreatment with NO scavenger C-PTIO and nitric oxide synthase (NOS) inhibitor L-NAME before pathogen inoculation reduced the disease-protecting ability of chitosan, and defence reactions were also downregulated, which indicated a possible role for NO in chitosan-induced resistance.

CONCLUSION

Protection offered by chitosan against pearl millet downy mildew disease is systemic in nature and durable. Chitosan-induced resistance is activated via NO signalling, as defence reactions induced by chitosan were downregulated under NO deficient conditions.

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

PURPOSE

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

[Chitosan as an adjuvant for inactivated vaccines against avian influenza viruses]

AIM

To study chitozan as an adjuvant for inactivated vaccines against A/H5 influenza viruses.

MATERIALS AND METHODS

Avian A/H5 influenza viruses were grown on chicken embryos or on MDCK cell line; viruses-containing fluid was inactivated with formalin. Mice were vaccinated intramuscularly with inactivated avian influenza virus mixed with chitozan and then levels of hemagglutination-inhibiting and neutralizing antibodies as well as protective efficacy against both homologous and drifted strains of avian influenza viruses A/H5 were measured.

RESULTS

Addition of chitozan to inactivated preparations of A/H5 avian influenza viruses for immunization of mice significantly increased levels of hemagglutination-inhibiting and neutralizing antibodies to both homologous and drifted variants of A/H5 influenza viruses, including those containing neuraminidase from other subtype as well as strains isolated 10 - 20 years earlier than virus used for vaccination. Chitozan significantly improved protective efficacy of inactivated avian influenza vaccines against infection with both homologous and drifted variant of the virus. Vaccination with inactivated avian influenza viruses A/H5 and chitozan induced high levels of antibodies even after single immunization as well as after administration of 8-fold reduced dose of preparation.

CONCLUSION

Chitozan is a perspective adjuvant for inactivated vaccines against avian influenza viruses, which could significantly improve immune response and protective efficacy against both homologous and drifted variants of avian influenza viruses A/H5.

[Influence of chitosan on immunophenotype and functional activity of murine mononuclear leukocytes after immunization with inactivated influenza vaccine]

In the overwhelming majority of countries inactivated vaccines, which form mainly humoral immunity, are used for prevention of influenza. The objective of the study was to assess the combined effect of inactivated influenza vaccine and chitozan on cellular immunity in CBA line mice. Intramuscular administration of 2 doses (with 4 week interval) of inactivated influenza vaccine and chitozan resulted in increased cytotoxic activity of splenic NK cells against NK-sensitive cell line K562 as well as in increased proliferative activity of mononuclear leukocytes, and numbers of CD3 T-lymphocytes, NKT cells, B-lymphocytes in animals' spleens. Combination of inactivated influenza vaccine with chitozan modulated the number MHC II-expressing cells by eliminating the increased reactivity of immune system cells as well as increased the number of MHC I-expressing cells. This point on the activation of cellular properties, which recognize intracellular pathogens, and thus on activation of both humoral and cellular factors of immune response. It can be proposed that inclusion of chitozan in the vaccine allows to modulate switching of the immune response from Th-2 to Th-1 type.

[Chitosan as an adjuvant for parenteral inactivated influenza vaccines]

Addition of 0.5% chitosan derivative to parenteral inactivated influenza vaccines increased antibody titers in the single immunization of mice by 4-5 times while double immunization showed 6-to-10-fold increases as compared with immunization without chitosan. Moreover, chitosan-containing vaccines induced the generation of antibodies to the drift variants of influenza virus. When the mice were given inactivated influenza virus A/H5N2 vaccine containing chitosan, immunogenicity and protective efficacy were much higher than when they received a vaccine containing no chitosan.

Potential use of chitosan nanoparticles for oral delivery of DNA vaccine in Asian sea bass (Lates calcarifer) to protect from Vibrio (Listonella) anguillarum

In recent years, attention has been focused on the possibility of utilizing DNA vaccines in fish aquaculture. A successful regime for intramuscular injection of naked DNA into fish has been developed and novel methods to deliver this DNA to fish are under investigation. The potential of chitosan as a polycationic gene carrier for oral administration has been explored since 1990s. The present study examines the potential efficacy of DNA vaccine against Vibrio anguillarum through oral route using chitosan nanoparticles encapsulation. The porin gene of V. anguillarum was used to construct DNA vaccine using pcDNA 3.1, a eukaryotic expression vector and the construct was named as pVAOMP38. The chitosan nanoparticles were used to deliver the constructed plasmid. In vitro and in vivo expression of porin gene was observed in sea bass kidney cell line (SISK) and in fish, respectively by fluorescent microscopy. The cytotoxicity of chitosan encapsulated DNA vaccine construct was analyzed by MTT assay and it was found that the cytotoxicity of pVAOMP38/chitosan was quite low. Distribution of gene in different tissues was studied in fish fed with the DNA (pVAOMP38) encapsulated in chitosan by using immunohistochemistry. The results indicate that DNA vaccine can be easily delivered into fish by feeding with chitosan nanoparticles. After oral vaccination Asian sea bass were challenged with Vibrio anguillarum by intramuscular injection. A relative percent survival (RPS) rate of 46% was recorded. The results indicate that Sea bass (Lates calcarifer) orally vaccinated with chitosan-DNA (pVAOMP38) complex showed moderate protection against experimental V. anguillarum infection.

Chitosan microspheres containing Bordetella bronchiseptica antigens as novel vaccine against atrophic rhinitis in pigs

The immune-stimulating activities of Bordetella bronchiseptica antigens containing dermonecrotoxin (BBD) loaded in chitosan microspheres (CMs) have already been reported in vitro and in vivo with a mouse alveolar macrophage cell line (RAW264.7) and mice. Therefore, this study attempted to demonstrate the successful induction of mucosal immune responses after the intranasal administration of BBD loaded in CMs (BBD-CMs) in colostrum-deprived pigs. The BBD was introduced to the CMs using an ionic gelation process involving tripolyphosphate (TPP). Colostrum-deprived pigs were then directly immunized through intranasal administration of the BBD-CMs. A challenge with a field isolate of B. bronchiseptica was performed ten days following the final immunization. The BBD-specific IgG and IgA titers, evident in the nasal wash and serum from the vaccinated pigs, increased with time (p<0.05). Following the challenge, the clinical signs of infection were about 6-fold lower in the vaccinated pigs compared with the nonvaccinated pigs. The grades for gross morphological changes in the turbinate bones from the vaccinated pigs were also significantly lower than the grades recorded for the nonvaccinated pigs (p<0.001). Therefore, the mucosal and systemic immune responses induced in the current study would seem to indicate that the intranasal administration of BBD-CMs may be an effective vaccine against atrophic rhinitis in pigs.

Stimulation of mucosal and systemic antibody responses against recombinant transferrin-binding protein B of Actinobacillus pleuropneumoniae with chitosan after tracheal administration in piglets

This study evaluated the suitability of using a chitosan formulation as an adjuvant to enhance both the mucosal and systemic immune responses against recombinant transferrin-binding protein B (rTbp B) of Actinobacillus pleuropneumoniae via direct tracheal administration. The chitosan formulation was found to enhance mucosal immune response, as measured by the secretory IgA level in lung lavage fluid and lung homogenate extracts, and systemic immune response, as measured by the serum IgG level.

[Experimental study on the chitosan-DNA vaccines against campylobacter jejuni invasion]

OBJECTIVE

The immunogenicity and protective efficacy of an experimental Campylobacter jejuni (C. jejuni) chitosan-DNA vaccines were evaluated in mice.

METHODS

The chitosan-DNA vaccines were prepared by embedding pcDNA3.1(+)-cadF and pcDNA3.1(+)-peblA with chitosan respectively. BALB/c mice were intranasally immunized in a four-dose primary series (7 d intervals) at doses of 60 microg chitosan-DNA vaccines each time. The comparative immunogenicities of nine formulations were assessed on the basis of the generation of antigen-specific antibodies in serum and intestinal secretions. Mice were attacked repeatedly through intragastric administration of C. jejuni HS:19 at the 8th week after the immunization and protective efficacy was determined by detecting the degrees of protection afforded against C. jejuni invaded.

RESULTS

The mice immunized with chitosan-DNA vaccines have generated high levels of IgA and IgG from the sera and IgA from the intestinal secretions and the P/N value went up to 20.58, 30.13 and 6.87 respectively. Meanwhile, the expression of intestinal SIgA increased correspondingly. Moreover the chitosan-DNA vaccines induced strongest level of protection in BALB/c mice against challenge with C. jejuni HS:19 strain and the protective efficacies was 93.70.

CONCLUSION

The results of this study indicate that the chitosan-DNA vaccines could induce significant protective immunity against C. jejuni challenge in the mice model.

Evaluation of the immune response following a short oral vaccination schedule with hepatitis B antigen encapsulated into alginate-coated chitosan nanoparticles

The purpose of this work was to assess the ability of recombinant hepatitis B vaccine, encapsulated in alginate-coated chitosan nanoparticles, to induce local and systemic immune responses following oral vaccination. The antigen was administered either alone or in combination with the immunopotentiator, synthetic oligodeoxynucleotide containing immunostimulatory CpG motif (CpG ODN) as adjuvant, and associated or not with the alginate-coated chitosan nanoparticles. After two immunizations the group I (HBsAg associated with nanoparticles) and the group VI (HBsAg and CpG, both associated with nanoparticles) showed enhanced immune responses. Both groups showed significant higher values of the CD69 expression in CD4+ and CD8+ T-lymphocytes and lower values of this marker in B lymphocytes. Moreover, a strongest proliferative response of the splenocytes, ex vivo stimulated with concanavalin A, was observed in the same groups. Although with a presence of non-responder mice within the groups, only mice of the groups I and VI elicited the generation of anti-HBsAg antibodies detected in serum (IgG) and in the intestinal washings (sIgA). The results demonstrated that coated chitosan nanoparticles might have potential for being used as a deliver system for oral vaccination with the recombinant hepatitis B surface antigen.

Chitosan and trimethyl chitosan chloride (TMC) as adjuvants for inducing immune responses to ovalbumin in mice following nasal administration

Chitosan of different molecular weights (Chi-P, MW=2.7x10(5) g/mol and Chi-A, MW=5.0x10(5) g/mol) and trimethyl chitosan chloride (TMC) of various degree of quaternization (DQ) including TMC-20, TMC-40 and TMC-60 were evaluated as adjuvants for inducing of immune responses to ovalbumin (OVA). OVA in solution and in alum were used as controls. Groups of BALB/c mice were immunized on days 0, 7 and 14. The IgG and IgA titers were examined on days 0, 13 and 21. It was found that for both days 13 and 21, Chi-A could elicit higher IgG responses to OVA than Chi-P. On day 13, OVA in TMC-40 induced IgG responses significantly higher than that in solution, Chi-P and TMC-60. Moreover, OVA in TMC-40 could induce IgG responses higher than OVA in alum. Although a significant difference was not observed at day 21, OVA in TMC-40 was shown to induce higher IgG responses than that in TMC-20, TMC-60 and solution. The IgA responses were the most pronounced on day 21. Again, Chi-A could elicite higher IgA responses than Chi-P and TMC-40 induced the highest IgA responses. In conclusion, these findings demonstrate that both MW of chitosan and DQ of TMC influence the level of immune induction. TMC-40 shows to be the most potent adjuvant for intranasal administration.

[Study on immune efficacy of Newcastle disease chitosan microsphere vaccine]

Newcastle disease is an acute and highly contagious disease caused by Newcastle disease virus (NDV), one of which does great harms to the poultry industry. The most basic measure of controlling New Castle disease is to alid vaccine, now we usually use La Sota live vaccine and inactivated NDV vaccine, but these two vaccines both have more or less limitation. It can produce higher mucosal immunity titers by taking vaccine orally, meanwhile it can induce humoral and cell-mediated immune response and mucosal immunity strongly. Therefore, it becomes the focus of the research, which prepare new pattern vaccines taking orally. NDV chitosan microsphere vaccine was prepared using chitosan as capsule wall material, NDV as core material, glutaraldehyde as cross-linking material, and its even particle diameter was 5.83um, and its surface was smooth and glossy, no obviously pore space, yellow brown pykno-ball, and its safety and potency were evaluated. The SPF chickens were immunized with NDV chitosan microsphere vaccine, La Sota live vaccine and inactivated NDV vaccine respectively. To evaluate vaccine's immune efficacy, using MTT to measure lymphocytes proliferation in vitro, using HI to measure serum special IgG and using ELISA tests to detect mucosal sIgA titers. The results show that NDV chitosan microsphere vaccine was safe, could induce humoral and cell-mediated immune response and mucosal immunity strongly. The results of the potency tests conformed that the vaccine could produce good protective effect.

[Cellular immunity induced by H.pylori vaccine with chitosan as adjuvant]

AIM

To study the cellular immunity induced by H.pylori vaccine with chitosan as adjuvant and the mechanism of immunological protection.

METHODS

BALB/c mice were randomly divided into nine groups and immunized by (1)PBS alone, (2)chitosan solution alone, (3)chitosan particles alone, (4)H.pylori antigen alone, (5)H.pylori antigen plus chitosan solution, (6)H.pylori antigen plus chitosan particles, (7)H.pylori antigen plus cholera toxin (CT), (8)H.pylori antigen plus chitosan solution and CT, (9)H.pylori antigen plus chitosan particles and CT orally respectively once a week for four weeks. At 4 weeks after the last immunization, mice were challenged by alive H.pylori (1x10(9) CFU/mL) twice at two days intervals. Before and after the challenge, mice were killed in batches and the H.pylori-infection in gastric mucosa was detected by H.pylori culture and Giemsa stain. ELISA and HE stain were used to detect IL-2, IL-4, IL-10 levels and pathologic change in gastric mucosa.

RESULTS

(1)In the groups with chitosan as an adjuvant, 60% mice could achieve immunological protection, which was consistent with using CT as an adjuvant (58.33%), and was more than that when using H.pylori antigen alone or without H.pylori antigen. (2)After challenge, the IL-2 levels in gastric mucosa in the groups with adjuvants were significantly higher than those in the control group (P<0.001-0.05). Moreover, IL-2 levels in the groups with adjuvants after challenge were significantly higher than those before challenge (P<0.05). Before challenge, the IL-10 and IL-4 levels in gastric mucosa were significantly higher in the groups with chitosan as adjuvant than those in non-adjuvant groups (P<0.05). After challenge, IL-10 levels were significantly higher in the groups with chitosan particles as adjuvant than those in other groups (P<0.05); IL-4 levels were significantly higher in the groups with chitosan particles as an adjuvant than those in the group with CT as an adjuvant, and those in the group with chitosan solution as an adjuvant were significantly higher than those in control group, non-adjuvant group and the groups with CT (P<0.05). IL-10 and IL-4 in the groups with adjuvants after challenge were significantly lower than those before challenge (P<0.05). (3)The degree of inflammation in gastric mucosa was significantly lower in the groups with chitosan and chitosan particles as adjuvant than those with CT as adjuvant(P<0.05).

CONCLUSION

(1)H.pylori vaccine with chitosan as an adjuvant has the immune protective effect against H.pylori infection. (2)H.pylori vaccine with chitosan as an adjuvant could reverse the inhibition of Th2 induced by H.pylori infection and recover the Th1/Th2 imbalance, which might contribute to the immune protection against H.pylori. (3)The rate of gastritis induced by H.pylori vaccine with chitosan as adjuvant was significantly lower than those with CT as adjuvant.

The antibacterial and immunostimulative effect of chitosan-oligosaccharides against infection by Staphylococcus aureus isolated from bovine mastitis

Based on our previous study evaluating the in vivo cure efficacy of chitosan on bovine mastitis, a more water-soluble chitosan-oligosaccharide (OCHT) with a high degree of deacetylation and low molecular weight was prepared to obtain high antibiotic efficacy. The growth of Staphylococcus aureus isolated from bovine mastitis was inhibited within 10 min of treatment with OCHT in concentrations ranging from 0.0001 to 0.5%. Additionally, electron microscopic observation indicated that the surface of the OCHT-treated bacteria was expanded, distorted, and lysed compared to that of the control bacteria. In mice, the proportion of monocytes was elevated, and the levels of interleukin-6 and interferon-gamma sharply increased l h after the peritoneal inoculation of the OCHT (0.5 to 1 mg per mouse). Mice challenged intraperitoneally with S. aureus (2.5 x 10(8) colony forming units) after oral treatment with OCHT (0.5 to 2 mg per day) for 7 days showed a higher survival rate (70-100%) than that of the control (10%). We suggest that the OCHT prepared in this study is a potential agent for the prevention and treatment of bovine mastitis based on its strong antibacterial activity against S. aureus as well as the immunostimulative effect it exhibits on murine infection by S. aureus.

Novel chitosan derivative nanoparticles enhance the immunogenicity of a DNA vaccine encoding hepatitis B virus core antigen in mice

BACKGROUND

Chitosan has been shown to possess useful properties such as non-toxicity, high biocompatibility and non-antigenicity that offer advantages for vaccine delivery systems. In this study, we prepared novel chitosan derivative nanoparticles as DNA vaccine carriers and the potential and mechanism of the DNA-nanoparticle complexes in inducing augmented immune responses were explored.

METHODS

The pVAX(HBc)DNA-nanoparticle complexes as vaccine delivery systems were studied in several aspects: the protection against DNase I degradation was measured by an in vitro inhibition assay; the sustained expression of the plasmid in vivo was determined by RT-PCR; the elevated uptake efficiency by phagocytes was observed with confocal microscopy; the biocompatibility was evaluated by cytotoxicity and histology assay; the complexes were administrated to C57BL/6 mice and the humoral and cellular immune responses were evaluated by ELISA, IFN-gamma production and cytolytic T lymphocyte (CTL)-specific lysis assay.

RESULTS

The remaining relative activity of DNase I after inhibition varied from 32.3% to 77.6%. The complexes were observed with higher uptake efficiency by phagocytes than naked DNA. Three types of nanoparticles did not induce significant cytotoxicity at concentrations<or=400 microg/ml. No specific histological alteration related to the injection of the complexes was observed. The formulations of DNA-nanoparticle complexes significantly enhanced the immunogenicity in several parameters: elevated antibody production, higher level of IFN-gamma secretion, and augmented specific cell lysis.

CONCLUSIONS

This study demonstrated the potential of the novel chitosan derivative nanoparticles for safe and effective DNA vaccine delivery.

Chitosan solution enhances both humoral and cell-mediated immune responses to subcutaneous vaccination

The development of safe, novel adjuvants is necessary to maximize the efficacy of new and/or available vaccines. Chitosan is a non-toxic, biocompatible, biodegradable, natural polysaccharide derived from the exoskeletons of crustaceans and insects. Chitosan's biodegradability, immunological activity and high viscosity make it an excellent candidate as a depot/adjuvant for parenteral vaccination. To this end, we explored chitosan solution as an adjuvant for subcutaneous vaccination of mice with a model protein antigen. We found that chitosan enhanced antigen-specific antibody titers over five-fold and antigen-specific splenic CD4+ proliferation over six-fold. Strong increases in antibody titers together with robust delayed-type hypersensitivity (DTH) responses revealed that chitosan induced both humoral and cell-mediated immune responses. When compared with traditional vaccine adjuvants, chitosan was equipotent to incomplete Freund's adjuvant (IFA) and superior to aluminum hydroxide. Mechanistic studies revealed that chitosan exhibited at least two characteristics that may allow it to function as an immune adjuvant. First, the viscous chitosan solution created an antigen depot. More specifically, less than 9% of a protein antigen, when delivered in saline, remained at the injection site after 8 h. However, more than 60% of a protein antigen delivered in chitosan remained at the injection site for 7 days. Second, chitosan induced a transient 67% cellular expansion in draining lymph nodes. The expansion peaked between 14 and 21 days after chitosan injection and diminished as the polysaccharide was degraded. These mechanistic studies, taken together with the enhancement of a vaccine response, demonstrate that chitosan is a promising and safe platform for parenteral vaccine delivery.

Chitosan nanoparticles encapsulated vesicular systems for oral immunization: preparation, in-vitro and in-vivo characterization

BSA-loaded chitosan nanoparticles were prepared and encapsulated in vesicles (liposomes and niosomes) to make them acid resistant upon oral administration. Prepared systems were characterized in-vitro for shape, size, entrapment efficiency and stability in simulated gastric fluid (SGF, pH 1.2) and simulated intestinal fluid (SIF, pH 7.5). The immune stimulating activity was studied by measuring serum IgG titre and secretory IgA (sIgA) levels in mucosal secretions following oral administration of various formulations in albino rats. Significantly higher (P < 0.05) serum IgG titres were achieved following oral administration of novel nanoparticulate vesicular formulations as compared with unmodified chitosan nanoparticles. Further, high sIgA levels in mucosal secretions advocated a possible application of chitosan nanoparticle encapsulated in vesicles as an oral vaccine delivery carrier-adjuvant system.

Protective immune responses to meningococcal C conjugate vaccine after intranasal immunization of mice with the LTK63 mutant plus chitosan or trimethyl chitosan chloride as novel delivery platform

Chitosan and its derivative N-trimethyl chitosan chloride (TMC), given as microparticles or powder suspensions, and the non-toxic mucosal adjuvant LTK63, were evaluated for intranasal immunization with the group C meningococcal conjugated vaccine (CRM-MenC). Mice immunized intranasally with CRM-MenC formulated with chitosan or TMC and the LTK63 mutant, showed high titers of serum and mucosal antibodies specific for the MenC polysaccharide. Neither significant differences were observed between microparticle formulations and powder suspensions nor when LTK63 was pre-associated to the delivery system or not. The bactericidal activity measured in serum of mice immunized intranasally with the conjugated vaccine formulated with the delivery systems and the LT mutant was superior to the activity in serum of mice immunized sub-cutaneously. Importantly, intranasal but not parenteral immunization, induced bactericidal antibodies at the nasal level, when formulated with both delivery system and adjuvant.

Forming and immunological properties of some lipopolysaccharide–chitosan complexes

The complex formation of lipopolysaccharide (LPS) with chitosan (Ch) was demonstrated using sedimentation velocity analysis in the analytical ultracentrifuge, centrifugation in glycerol gradient and isopicnic centrifugation in cesium chloride. An addition of Ch to the Escherichia coli and Yersinia pseudotuberculosis LPS solutions was found to result in formation of the stable LPS-Ch complexes. The interaction is a complicated process and depends on time and reaction temperature, as well as on the molecular weight of chitosan. A stable LPS-Ch complex could be formed only after preliminary incubation of the initial components at an elevated temperature (37 degrees C). It should be noted that process of LPS complexation with Ch is accompanied by additional dissociating of LPS. The complex formation was shown to be a result not only of ionic binding, but also of other types of interactions. The interaction of Ch with LPS was shown to modulate significantly the biological activity of LPS. The LPS-Ch complex (1:5 w/w) was shown to possess much lower toxicity in a comparison with the parent LPS at injection to mice in the similar concentration. The LPS-Ch complex was shown to maintain an ability to induce of IL-8 and TNF, but induction of IL-8 and TNF biosynthesis by the LPS-Ch complex was lower than that by the parent LPS. The complex LPS-Ch, similarly to the parent LPS, was found stimulated the formation of the IL-8 in the dose-dependent manner in the human embryonal kidney cells (HEK 293 cells) transfected with TLR4 in combination with MD2.

The protective effect of chitin and chitosan against Vibrio alginolyticus in white shrimp Litopenaeus vannamei

White shrimp, Litopenaeus vannamei, which had been injected with chitin at 4, 6 and 8 microg g(-1) or chitosan at 2, 4 and 6 microg g(-1), were challenged with pathogen Vibrio alginolyticus at 2 x 10(6) colony-forming units (cfu) shrimp(-1) and then placed in seawater of 34 per thousand. The survival of shrimp that received chitin or chitosan at either dose was significantly higher than that of control shrimp after 1 day, and at the termination of the experiment (6 days after the challenge). In another experiment, the total haemocyte count (THC), phenoloxidase activity, respiratory burst, superoxide dismutase (SOD) activity, and phagocytic activity to V. alginolyticus were measured when L. vannamei (10.4 +/- 0.7 g) were injected individually with chitin at 4 and 6 microg g(-1) or chitosan at 2 and 4 microg g(-1). L. vannamei received chitin at 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) increased significantly its THC and respiratory burst after 2 days. L. vannamei received chitin at 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) still maintained significantly higher phenoloxidase activity after 6 days. L. vannamei received chitin at 4 and 6 microg g(-1) or chitosan at 2 and 4 microg g(-1) increased its phagocytic activity against V. alginolyticus after 1 day, respectively. It is therefore concluded that L. vannamei that received chitin at 6 microg g(-1) or chitosan at 4 microg g(-1) or less increased its immune ability and resistance to V. alginolyticus infection.

Local and systemic activity of the polysaccharide chitosan at lymphoid tissues after oral administration

Chitosan is a cationic polysaccharide derived from the partial deacetylation of chitin, which exhibits particular properties: interacts with negatively charged sites on the cell surface; changes the permeability of intestinal epithelium, enhancing the uptake of peptides and proteins; and activates leukocytes. Antigens coadministered or encapsulated with the polysaccharide show improved mucosal and systemic humoral immune responses, although the mechanism is poorly understood. Herein, we characterized in Peyer's patches mesenteric lymph nodes and spleen molecular events triggered after oral administration of chitosan in the absence of protein antigen. Sixteen hours after feeding, we studied the uptake and distribution of the polysaccharide, the phenotype of recruited antigen-presenting cells (APC), the induction of cytokines such as tumor necrosis factor alpha, interleukin (IL)-12, IL-4, IL-10, and transforming growth factor-beta (TGF-beta), and the activation of T lymphocytes. We show here that the uptake of chitosan at inductive mucosal sites involves CD11b/c+ APC and that chitosan feeding increases the percentage of OX62+ dendritic cells, which up-regulate the major histocompatibility complex class II antigens without changing the expression of costimulatory CD80 or CD86 molecules. The polysaccharide elicits the release of IL-10 as well as the expression of IL-4 and TGF-beta in mucosa, and in spleen, the activation of CD3+ T cells occurs. Our results demonstrate that chitosan acts by enhancing the T helper cell type 2 (Th2)/Th3 microenvironment in the mucosa. A single dose of this polysaccharide exhibits local and systemic effects, and its activity could be relevant in the maintenance of the intestinal homeostasis.