OVA-bound nanoparticles induce OVA-specific IgG1, IgG2a, and IgG2b responses with low IgE synthesis

Undaria pinnatifida extract attenuates combined allergic rhinitis and asthma syndrome by the modulation of epithelial cell dysfunction and oxidative stress

Undaria pinnatifida ( U. pinnatifida) has long been a part of the human diet and medicine. Although U. pinnatifida has been reported to have immunomodulatory, anti-inflammatory, anti-diabetic and antibacterial activities, its specific effect on patients with combined allergic rhinitis and asthma syndrome (CARAS) has not been clarified. In this study, the anti-allergic and anti-inflammatory effects of U. pinnatifida extract (UPE) are investigated in a mouse model of ovalbumin (OVA)-induced CARAS. The oral administration of UPE inhibits allergic responses by reducing OVA-specific immunoglobulin levels. As a result, the symptoms of early reactions are also improved. UPE inhibits the accumulation of inflammatory cells and attenuates the expression of Th2 cytokines in both nasal and bronchoalveolar lavage fluid. Furthermore, UPE treatment inhibits the NF-κB/MAPK signaling pathway in lung homogenates. Additionally, UPE prevents shedding of the nasal mucosal epithelium, protects the integrity of the epithelium, enhances the expression of E-cadherin at the junction of epithelial cells, and inhibits the degradation of ZO-1 and occludin in the airway epithelium. In addition, UPE ameliorates dysfunction of the nasal epithelial barrier by enhancing antioxidant properties and downregulating the expression of the inflammatory factor IL-33. These results suggest that UPE may treat CARAS by modulating epithelial cell dysfunction and oxidative stress.

Impact of pH-Shifting and Autoclaving on the Allergenic Potential of Red Kidney Bean (Phaseolus vulgaris L.) Lectins

The ingestion of red kidney bean products is hindered by the persistent allergenicity of lectins, even after autoclaving. This study examined the modification of lectin allergenicity in red kidney beans by pH-shifting and autoclaving treatments, utilizing BALB/c mouse sensitization, in situ recirculating perfusion, and a bone marrow-derived dendritic cell (BMDC) model for allergenicity evaluation. Compared to autoclaving alone, combined pH-shifting and autoclaving reduced allergic symptoms in BALB/c mice, as evidenced by lower serum IgE, mMCPT-1, GM-CSF, HIS, IL-2, IL-4, IL-9, IL-13, and IL-17 levels and higher IgG1, IgG2a, IL-10, IFN-γ, and IFN-α cytokine release. Moreover, lectin continued to affect intestinal permeability and damaged the barrier despite undergoing pH-shifting and autoclaving treatments. Additionally, the uptake of lectin by BMDCs through mannose receptor-mediated endocytosis was diminished, with an increased susceptibility to endolysosomal degradation. The T-cell polarization was consistent with the mouse experiments, where the balance of Th1 and Th2 cells remained in lectin with pH-shifting and autoclaving treatments though the decreased abundance ratios of peptide YKYDSNAHT and increased abundance ratios of peptide ITKGNVETN in endolysosomal degradation. Therefore, the immunogenicity of lectins could be decreased by pH-shifting and autoclaving treatments, offering insights into the development of hypoallergenic legume products.

Self-assembled protein vesicles as vaccine delivery platform to enhance antigen-specific immune responses

Self-assembling protein nanoparticles are beneficial platforms for enhancing the often weak and short-lived immune responses elicited by subunit vaccines. Their benefits include multivalency, similar sizes as pathogens and control of antigen orientation. Previously, the design, preparation, and characterization of self-assembling protein vesicles presenting fluorescent proteins and enzymes on the outer vesicle surface have been reported. Here, a full-size model antigen protein, ovalbumin (OVA), was genetically fused to the recombinant vesicle building blocks and incorporated into protein vesicles via self-assembly. Characterization of OVA protein vesicles showed room temperature stability and tunable size. Immunization of mice with OVA protein vesicles induced strong antigen-specific humoral and cellular immune responses. This work demonstrates the potential of protein vesicles as a modular platform for delivering full-size antigen proteins that can be extended to pathogen antigens to induce antigen specific immune responses.

Preparation and adjuvanticity against PCV2 of Viola philippica polysaccharide loaded in Chitosan-Gold nanoparticle

The present Porcine circovirus type 2 virus (PCV2) vaccine adjuvants suffer from numerous limitations, such as adverse effects, deficient cell-mediated immune responses, and inadequate antibody production. In this study, we explored the potential of a novel nanoparticle (CS-Au NPs) based on gold nanoparticles (Au NPs) and chitosan (CS) that modified Viola philippica polysaccharide (VPP) as efficient adjuvants for PCV2 vaccine. The characterization demonstrated that CS-Au-VPP NPs had a mean particle size of 507.42 nm and a zeta potential value of -21.93 mV. CS-Au-VPP NPs also exhibited good dispersion and a stable structure, which did not alter the polysaccharide properties. Additionally, the CS-Au-VPP NPs showed easy absorption and utilization by the organism. To investigate their immune-enhancing potential, mice were immunized with a mixture of CS-Au-VPP NPs and PCV2 vaccine. The evaluation of relevant immunological indicators, including specific IgG antibodies and their subclasses, cytokines, and T cell subpopulations, confirmed their immune-boosting effects. The in vivo experiments revealed that the medium-dose CS-Au-VPP NPs significantly elevated the levels of specific IgG antibodies and their subclasses, cytokines, and T cell subpopulations in PCV2-immunized mice. These findings suggest that CS-Au-VPP NPs can serve as a promising vaccine adjuvant due to their stable structure and immunoenhancement capabilities.

Effect of Antigen Structure in Subunit Vaccine Nanoparticles on Humoral Immune Responses

Subunit vaccines offer numerous attractive features, including good safety profiles and well-defined components with highly characterized properties because they do not contain whole pathogens. However, vaccine platforms based on one or few selected antigens are often poorly immunogenic. Several advances have been made in improving the effectiveness of subunit vaccines, including nanoparticle formulation and/or co-administration with adjuvants. Desolvation of antigens into nanoparticles is one approach that has been successful in eliciting protective immune responses. Despite this advance, damage to the antigen structure by desolvation can compromise the recognition of conformational antigens by B cells and the subsequent humoral response. Here, we used ovalbumin as a model antigen to demonstrate enhanced efficacy of subunit vaccines by preserving antigen structures in nanoparticles. An altered antigen structure due to desolvation was first validated by GROMACS and circular dichroism. Desolvant-free nanoparticles with a stable ovalbumin structure were successfully synthesized by directly cross-linking ovalbumin or using ammonium sulfate to form nanoclusters. Alternatively, desolvated OVA nanoparticles were coated with a layer of OVA after desolvation. Vaccination with salt-precipitated nanoparticles increased OVA-specific IgG titers 4.2- and 22-fold compared to the desolvated and coated nanoparticles, respectively. In addition, enhanced affinity maturation by both salt precipitated and coated nanoparticles was displayed in contrast to desolvated nanoparticles. These results demonstrate both that salt-precipitated antigen nanoparticles are a potential new vaccine platform with significantly improved humoral immunity and a functional value of preserving antigen structures in vaccine nanoparticle design.

Use of protective antigen of Bacillus anthracis as a model recombinant antigen to evaluate toll-like receptors 2, 3, 4, 7 and 9 agonists in mice using established functional antibody assays, antigen-specific antibody assays and cellular assays

Toll-like receptor (TLR) agonists can act as immune stimulants alone or as part of alum or oil formulations. Humoral and cellular immune responses were utilized to assess quantitative and qualitative immune response enhancement by TLR agonists using recombinant protective antigen (rPA) of B. anthracis as a model antigen. To rPA, combined with aluminum hydroxide (Alhydrogel; Al(OH)3) or squalene (AddaVax™), was added one of 7 TLR agonists: TLR2 agonist Pam3CysSK4 (PamS), TLR3 agonist double stranded polyinosinic:polycytidylic acid (PolyIC), TLR4 agonists Monophosphoryl lipid A (MPLA) or glucopyranosyl lipid A (GLA), TLR7-8 agonists 3M-052 or Resiquimod (Resiq), or TLR9 agonist CPG 7909 (CPG). CD-1 or BALB/c mice received two intraperitoneal or intramuscular immunizations 14 days apart, followed by serum or spleen sampling 14 days later. All TLR agonists except PamS induced high levels of B. anthracis lethal toxin-neutralizing antibodies and immunoglobulin G (IgG) anti-PA. Some responses were >100-fold higher than those without a TLR agonist, and IP delivery (0.5 mL) induced higher TLR-mediated antibody response increases compared to IM delivery (0.05 mL). TLR7-8 and TLR9 agonists induced profound shifts of IgG anti-PA response to IgG2a or IgG2b. Compared to the 14-day immunization schedule, use of a shortened immunization schedule of only 7 days between prime and boost found that TLR9 agonist CPG in a squalene formulation maintained higher interferon-γ-positive cells than TLR4 agonist GLA. Variability in antibody responses was lower in BALB/c mice than CD-1 mice but antibody responses were higher in CD-1 mice. Lower serum 50% effective concentration (EC50) values were found for rPA-agonist formulations and squalene formulations compared to Al(OH)3 formulations. Lower EC50 values also were associated with low frequency detection of linear peptide epitopes. In summary, TLR agonists elicited cellular immune responses and markedly boosted humoral responses.

Therapeutic Effects of Human Pluripotent Stem Cell-Derived Mesenchymal Stem Cells on a Murine Model of Acute Type-2-Dominated Airway Inflammation

Allergic rhinitis and allergic asthma are the most common type-2 inflammatory diseases, which are hardly curable and cause heavy burden to general well-being. Mesenchymal stem cells (MSCs) are multipotent nonhematopoietic cells with potential immunomodulatory effects that have been showning to have a therapeutic effect on allergic diseases. Here, we investigated the effects of human induced pluripotent stem cell (iPSC)-derived MSCs on airway hyperresponsiveness and acute type-2-dominated inflammation throughout the upper and lower airways. In this study, human MSCs, MSC cell culture supernatant, and culture medium (control) was injected into the acute airway inflammatory model via the tail vein. Mouse behavioristics were recorded immediately and mouse lung function was measured 24 hours after the last ovalbumin (OVA) challenge. Histological staining, Luminex, Elisa and flow cytometry were employed to evaluate the effects on the production of total/OVA-specific IgG1 and IgE, cytokines expression in lung tissues, and inflammatory cells infiltration in the lung and spleen of the experimental mice. Expressions of eotaxin, IL-4, IL-5, IL-13, IL-33 in nasal and lung lavage were evaluated by Luminex and Elisa. We found that for this acute inflammatory mouse model, human MSC transplantation significantly mitigated the decreased motoring time and the increased lung function Rrs caused by OVA challenge. Serum OVA-IgG1, OVA-IgE, and eosinophil percentages in the splenocytes were significantly decreased. Injection of the MSC supernatant also showed the same trend, but not significantly changed. After treatment, IL-4 and IL-13 were significantly decreased in the lung tissue, and IL-5 and IL-13 were significantly decreased in lung lavage. In conclusion, both human MSC culture supernatant and cell transplantation could alleviate AHR and inflammation in acute inflammatory experimental animals, which demonstrated their potential for clinical therapeutics. Human iPSC-MSCs, MSC cell culture supernatant, or culture medium (control) was injected into the OVA-induced acute airway inflammatory model via the tail vein. Behavioral changes, AHR, serum OVA-specific IgG1 and IgE concentrations, and type-2 inflammations were alleviated.

Hyaluronic Acid-Glycine-Cholesterol Conjugate-Based Nanoemulsion as a Potent Vaccine Adjuvant for T Cell-Mediated Immunity

Clinical cases of allergic reaction that are due to excipients containing polyethylene glycol (PEG), a hydrophilic molecule commonly used in drug/vaccine formulations, has attracted much attention in recent years. In order to develop PEG-free adjuvants, we investigated the feasibility of natural ingredients in the human body such as hyaluronic acid in the form of hyaluronic acid-glycine cholesterol (HACH) conjugate as an excipient for vaccine formulation. Interestingly, HACH grafted with ~13 wt.% cholesterol has good water dispersity and can serve as an emulsifier to stabilize the squalene/water interfaces, yielding a milky white and isotropic emulsion (SQ@HACH) after being passed through a high-shear microfluidizer. Our results show that SQ@HACH particles possessed a unimodal average hydrodynamic diameter of approximately 190 nm measured by dynamic light scattering and exhibited good stability upon storage at 4 °C and 37 °C for over 20 weeks. The results of immunogenicity using a mouse model with ovalbumin (OVA) as the antigen revealed that SQ@HACH significantly enhanced antigen-specific immune responses, including the polarization of IgG antibodies, the cytokine secretions of T cells, and enhancement of cytotoxic T lymphocyte (CTL) activation. Moreover, SQ@HACH revealed lower local inflammation and rapidly absorbing properties compared with AlPO₄ after intramuscular injection in vivo, indicating the potential functions of the HA-derived conjugate as an excipient in vaccine formulations for enhancement of T cell-mediated immunity.

Yeast Shells Encapsulating Adjuvant AS04 as an Antigen Delivery System for a Novel Vaccine against Toxoplasma Gondii

Toxoplasma gondii (T. gondii) infection causes severe zoonotic toxoplasmosis, which threatens the safety of almost one-third of the human population globally. However, there is no effective protective vaccine against human toxoplasmosis. This necessitates anti-T. gondii vaccine development, which is a main priority of public health. In this study, we optimized the adjuvant system 04 (AS04), a vaccine adjuvant constituted by 3-O-desacyl-4'-monophosphoryl lipid A (a TLR4 agonist) and aluminum salts, by packing it within natural extracts of β-glucan particles (GPs) from Saccharomyces cerevisiae to form a GP-AS04 hybrid adjuvant system. Through a simple mixing procedure, we loaded GP-AS04 particles with the total extract (TE) of T. gondii lysate, forming a novel anti-T. gondii vaccine GP-AS04-TE. Results indicated that the hybrid adjuvant can efficiently and stably load antigens, mediate antigen delivery, facilitate the dendritic uptake of antigens, boost dendritic cell maturation and stimulation, and increase the secretion of pro-inflammatory cytokines. In the mouse inoculation model, GP-AS04-TE significantly stimulated the function of dendritic cells, induced a very strong TE-specific humoral and cellular immune response, and finally showed a strong and effective protection against toxoplasma chronic and acute infections. This work proves the potential of GP-AS04 for exploitation as a vaccine against a range of pathogens.

Chemical Conjugation Strategies for the Development of Protein-Based Subunit Nanovaccines

The production of subunit nanovaccines relies heavily on the development of a vaccine delivery system that is safe and efficient at delivering antigens to the target site. Nanoparticles have been extensively investigated for vaccine delivery over the years, as they often possess self-adjuvanting properties. The conjugation of antigens to nanoparticles by covalent bonds ensures co-delivery of these components to the same subset of immune cells in order to trigger the desired immune responses. Herein, we review covalent conjugation strategies for grafting protein or peptide antigens onto other molecules or nanoparticles to obtain subunit nanovaccines. We also discuss the advantages of chemical conjugation in developing these vaccines.

Surface Immunogenic Protein of Streptococcus Group B is an Agonist of Toll-Like Receptors 2 and 4 and a Potential Immune Adjuvant

Vaccine-induced protection against pathogens, especially subunit-based vaccines, are related to antigen properties but mainly in their ability to stimulate the immune system by the use of an adjuvant. Modern vaccines are formulated with a high level of antigen purity, where an efficient adjuvant is necessary. In this context, the use of protein Toll-Like Receptor (TLR) agonists as vaccine adjuvants has been highlighted because of their optimal immunogenicity and minimal toxicity. The Surface Immunogenic Protein (SIP) from Group B Streptococcus (GBS) has gained importance as a new potential protein-based vaccine. Recently, we reported that recombinant SIP (rSIP) expressed by E. coli and purified by High Performance Liquid Chromatography (HPLC) alone induces a protective humoral immune response. In this study, we present the immunomodulatory properties of rSIP as a protein-based adjuvant, as an agonist of TLR. To this end, we showed that C57BL/6 bone marrow-derived dendritic cells pulsed by rSIP resulted in enhanced CD40, CD80, CD86, and Major Histocompatibility Complex (MHC) class II as well as increased secretion proinflammatory cytokines Interleukin (IL)-6, Interferon (IFN)-γ, Tumor Necrosis Factor (TNF)-α, and IL-10. Next, we investigated the in vivo effect of rSIP in the absence or presence of ovalbumin (OVA) on antigen-specific antibody secretion in C57BL/6 mice. Immunization with rSIP plus OVA showed that anti-OVA IgG2a and IgG1a increased significantly compared with OVA alone in C57BL/6 mice. Also, the immunization of rSIP plus OVA generates increased serum cytokines levels characterized by IL-12p70, IL-10, IL-4, and IFN-γ. Interestingly, we observed that rSIP stimulate Toll Like Receptor (TLR)2 and TLR4, individually expressed by Human embryonic kidney (HEK) 293-derived TLR reporter cells. These findings suggest that rSIP is a new potential protein TLR agonist adjuvant and may be employed in the development of new vaccines.

Immunomodulatory effects of Rhipicephalus haemaphysaloides serpin RHS2 on host immune responses

Background

Rhipicephalus haemaphysaloides is a widespread tick species in China and other South East Asian countries, where it is the vector of many pathogens. The objective of this study was to study the role of serpin (serine protease inhibitor) during the tick-host interaction.

Methods

The differentiation of bone marrow-derived dendritic cells (BMDC) was induced in vitro, and the effect of RHS2 on the maturation of DCs was evaluated. The effects of RHS2 on T cell activation and cytotoxic T lymphocytes’ (CTLs) activity were analyzed by flow cytometry. Antibody subtypes after immunization of mice with RHS2 and OVA were determined.

Results

RHS2 can inhibit the differentiation of bone marrow-derived cells into DCs and promote their differentiation into macrophages. RHS2 can inhibit the maturation of DCs and the expression of CD80, CD86 and MHCII. The number of CD3⁺CD4⁺ and CD3⁺CD8⁺ T cells secreting IFN-γ, IL-2 and TNF-α was decreased, and the number of CD3⁺CD4⁺ T cells secreting IL-4 was increased, indicating that RHS2 can inhibit the activation of CD4 T cells and CD8 T cells, leading to inhibition of Th1 immune response. RHS2 inhibits the elimination of target cells by cytotoxic T lymphocytes. After immunization of mice with RHS2 and OVA, serum IgG2b was significantly reduced and IgM was increased.

Conclusions

The results show that RHS2 has an inhibitory effect on the host immune response. Ticks have evolved various ways to circumvent adaptive immunity. Their serpin inhibits BMDC differentiation to reduce immune responses.

Lower-Sized Chitosan Nanocapsules for Transcutaneous Antigen Delivery

Transcutaneous vaccination has several advantages including having a noninvasive route and needle-free administration; nonetheless developing an effective transdermal formulation has not been an easy task because skin physiology, particularly the stratum corneum, does not allow antigen penetration. Size is a crucial parameter for successful active molecule administration through the skin. Here we report a new core-shell structure rationally developed for transcutaneous antigen delivery. The resulting multifunctional carrier has an oily core with immune adjuvant properties and a polymeric corona made of chitosan. This system has a size of around 100 nm and a positive zeta potential. The new formulation is stable in storage and physiological conditions. Ovalbumin (OVA) was used as the antigen model and the developed nanocapsules show high association efficiency (75%). Chitosan nanocapsules have high interaction with the immune system which was demonstrated by complement activation and also did not affect cell viability in the macrophage cell line. Finally, ex vivo studies using a pig skin model show that OVA associated to the chitosan nanocapsules developed in this study penetrated and were retained better than OVA in solution. Thus, the physicochemical properties and their adequate characteristics make this carrier an excellent platform for transcutaneous antigen delivery.

PilVax - a novel peptide delivery platform for the development of mucosal vaccines

Peptide vaccines are an attractive strategy to engineer the induction of highly targeted immune responses and avoid potentially allergenic and/or reactogenic protein regions. However, peptides by themselves are often unstable and poorly immunogenic, necessitating the need for an adjuvant and a specialised delivery system. We have developed a novel peptide delivery platform (PilVax) that allows the presentation of a stabilised and highly amplified peptide as part of the group A streptococcus serotype M1 pilus structure (PilM1) on the surface of the non-pathogenic bacterium Lactococcus lactis. To show proof of concept, we have successfully inserted the model peptide Ova_324–339 into 3 different loop regions of the backbone protein Spy0128, which resulted in the assembly of the pilus containing large numbers of peptide on the surface of L. lactis. Intranasal immunisation of mice with L. lactis PilM1-Ova generated measurable Ova-specific systemic and mucosal responses (IgA and IgG). Furthermore, we show that multiple peptides can be inserted into the PilVax platform and that peptides can also be incorporated into structurally similar, but antigenically different pilus structures. PilVax may be useful as a cost-effective platform for the development of peptide vaccines against a variety of important human pathogens.

Evaluation of vaccine potential of 2-Cys peroxiredoxin from the hard tick Haemaphysalis longicornis

Ticks require blood feeding on vertebrate animals throughout their life cycle, and also concentrate the iron-containing blood, resulting in a high concentration of hydrogen peroxide (H2O2). High concentrations of H2O2 are harmful to organisms, due to their serious damage of macromolecules. Ticks have antioxidant enzymes, such as peroxiredoxins (Prxs), that scavenge H2O2. Prxs may have important roles in regulating the H2O2 concentration in ticks during blood feeding and oviposition. Moreover, Prxs are considered potential vaccine candidates in other parasites, such as Leishmania and Fasciola. In the present study, the efficacy of a tick Prx (HlPrx2) as a vaccine candidate antigen was evaluated. First, recombinant HlPrx2 (rHlPrx2) was expressed in Escherichia coli, and then, its purity and endotoxin levels were confirmed prior to administration. The rHlPrx2 proteins were of high purity with acceptably low endotoxin levels. Second, the ability of rHlPrx2 administration to stimulate mouse immunity was evaluated. The rHlPrx2 protein, with or without an adjuvant, could stimulate immunity in mice, especially the IgG1 of Th2 immune response. Using Western blot analysis, we also observed whether rHlPrx2-immunized mice sera could recognize native HlPrx2 protein in crude tick midgut proteins. Western blot analysis demonstrated that rHlPrx2-administrated mouse sera could detect the native HlPrx2. Finally, the effects of rHlPrx2 immunization in mice were studied using nymphal ticks. Although the challenged ticks were not affected by rHlPrx2 immunization, rHlPrx2 still might be considered as a vaccine candidate against ticks because of its high immunogenicity.

Adjuvant Activity of Poly-ε-caprolactone/Chitosan Nanoparticles Characterized by Mast Cell Activation and IFN-γ and IL-17 Production

Polymeric nanoparticles (NPs) are extremely attractive vaccine adjuvants, able to promote antigen delivery and in some instances, exert intrinsic immunostimulatory properties that enhance antigen specific humoral and cellular immune responses. The poly-ε-caprolactone (PCL)/chitosan NPs were designed with the aim of being able to combine the properties of the 2 polymers in the preparation of an adjuvant for the hepatitis B surface antigen (HBsAg). This article reports important results of an in vitro mechanistic study and immunization studies with HBsAg associated with different concentrations of the nanoparticles. The results revealed that PCL/chitosan NPs promoted mast cell (MC) activation (β-hexosaminidase release) and that its adjuvant effect is not mediated by the TNF-α secretion. Moreover, we demonstrated that HBsAg loaded PCL/chitosan NPs, administered through the subcutaneous (SC) route, were able to induce higher specific antibody titers without increasing IgE when compared to a commercial vaccine, and that the IgG titers are nanoparticle-dose dependent. The results also revealed the NPs' capability to promote a cellular immune response against HBsAg, characterized by the production of IFN-γ and IL-17. These results demonstrated that PCL/chitosan NPs are a good hepatitis B antigen adjuvant, with direct influence on the intensity and type of the immune response generated.

3M-052 as an adjuvant for a PLGA microparticle-based Leishmania donovani recombinant protein vaccine

It is believed that an effective vaccine against leishmaniasis will require a T helper type 1 (T_H 1) immune response. In this study, we investigated the adjuvanticity of the Toll-like receptor (TLR) 7/8 agonist 3M-052 in combination with the Leishmania donovani 36-kDa nucleoside hydrolase recombinant protein antigen (NH36). NH36 and 3M-052 were encapsulated in separate batches of poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs). The loading efficiency for NH36 was 83% and for 3M-052 was above 95%. In vitro stimulation of bone marrow-derived dendritic cells, measured by IL-12 secretion, demonstrated that 3M-052 (free or MP-formulated) had a concentration-dependent immunostimulatory effect with an optimum concentration of 2 µg/mL. In immunogenicity studies in BALB/c mice, MP-formulated NH36 and 3M-052 elicited the highest serum titers of T_H 1-associated IgG2a and IgG2b antibodies and the highest frequency of IFNγ-producing splenocytes. No dose dependency was observed among MP/NH36/3M-052 groups over a dose range of 4-60 µg 3M-052 per injection. The ability of MP-formulated NH36 and 3M-052 to elicit a T_H 1-biased immune response indicates the potential for PLGA MP-formulated 3M-052 to be used as an adjuvant for leishmaniasis vaccines. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part B: Appl Biomater, 106B: 1587-1594, 2018.

The immunological characteristics and probiotic function of recombinant Bacillus subtilis spore expressing Clonorchis sinensis cysteine protease

Background

Clonorchiasis, a food-borne zoonosis, is caused by Clonorchis sinensis. The intestinal tract and bile ducts are crucial places for C. sinensis metacercariae to develop into adult worms. The endospore of Bacillus subtilis is an ideal oral immunization vehicle for delivery of heterologous antigens to intestine. Cysteine protease of C. sinensis (CsCP) is an endogenous key component in the excystment of metacercariae and other physiological or pathological processes.

Methods

We constructed a fusion gene of CotC (a coat protein)-CsCP and obtained B. subtilis spores with recombinant plasmid of pEB03-CotC-CsCP (B.s-CotC-CsCP). CotC-CsCP expressed on spores’ surface was detected by Western blotting and immunofluorescence. Immunological characteristics of recombinant spore coat protein were evaluated in a mouse model. The levels of CsCP-specific antibodies were detected by ELISA. Effects of recombinant spores on mouse intestine were evaluated by histological staining. The activities of biochemical enzymes in serum were assayed by microplate. Liver sections of infected mice were evaluated by Ishak score after Masson’s trichrome.

Results

The B.s-CotC-CsCP spores displayed CsCP on their coat. Specific IgG and isotypes were significantly induced by coat proteins of B.s-CotC-CsCP spores after subcutaneous immunization. IgA levels in intestinal mucus and bile of B.s-CotC-CsCP orally treated mice significantly increased. Additionally, more IgA-secreting cells were observed in enteraden and lamina propria regions of the mouse jejunum, and an increased amount of acidic mucins in intestines were also observed. There were no significant differences in enzyme levels of serum among groups. No inflammatory injury was observed in the intestinal tissues of each group. The degree of liver fibrosis was significantly reduced after oral immunization with B.s-CotC-CsCP spores.

Conclusions

Bacillus subtilis spores maintained the original excellent immunogenicity of CsCP expressed on their surface. Both local and systemic specific immune responses were elicited by oral administration of B.s-CotC-CsCP spores. The spores effectively promoted intestinal health by inducing secretion of acidic mucins, with no other side effects to the liver or intestine. Oral administration of spores expressing CsCP could provide effective protection against C. sinensis. This study may be a cornerstone for development of antiparasitic agents or vaccines against clonorchiasis based on B. subtilis spore expressing CsCP on the surface.

Electronic supplementary material

The online version of this article (doi:10.1186/s13071-016-1928-0) contains supplementary material, which is available to authorized users.

Biomimetic nanoassembly for targeted antigen delivery and enhanced Th1-type immune response

A new type of biomimetic nanoassembly for targeted antigen delivery and enhanced Th1-type response is reported for the first time, to combat the major challenges in the treatment of infected cells.

Vaccination with OVA-bound nanoparticles encapsulating IL-7 inhibits the growth of OVA-expressing E.G7 tumor cells in vivo

Immunotherapy has gained special attention due to its specific effects on tumor cells and systemic action to block metastasis. We recently demonstrated that ovalbumin (OVA) conjugated to the surface of nanoparticles (NPs) (OVA‑NPs) can manipulate humoral immune responses. In the present study, we aimed to ascertain whether vaccination with OVA-NPs entrapping IL-7 (OVA-NPs-IL-7) are able to induce antitumor immune responses in vivo. Pretreatment with a subcutaneous inoculation of OVA-NPs delayed the growth of thymic lymphoma cells expressing a model tumor antigen OVA (E.G7-OVA), and OVA-NPs-IL-7 substantially blocked the growth of E.G7-OVA tumor cells, although NPs-IL-7 alone had a meager effect, as assessed by the mean tumor size and the percentage of tumor-free mice. However, pretreatment with OVA-NPs-IL-7 failed to reduce the growth of parental thymic tumor cells, suggesting that the antitumor effect was antigen-specific. A tetramer assay revealed that vaccination with OVA-NPs-IL-7 tended to enhance the proportion of cytotoxic T cells (CTLs) specific for OVA. When the tumor-free mice inoculated with OVA-NPs-IL-7 plus EG.7 cells were rechallenged with E.G7-OVA cells, they demonstrated reduced growth compared with that in the control mice. Thus, a single subcutaneous injection of OVA-NPs-IL-7 into mice induced tumor-specific and also memory-like immune responses, resulting in regression of tumor cells. Antigens on NPs entrapping IL-7 would be a promising carrier to develop and enhance immune responses, including humoral and cellular immunity as well as a method of drug delivery to a specific target of interest.