阅读说明：本技术 一种寨卡病毒e蛋白结合疫苗及其制备方法 (Zika virus E protein conjugate vaccine and preparation method thereof ) 是由 胡涛 齐金铭 于卫立 申莉娟 于 2020-04-01 设计创作，主要内容包括：本发明公开了一种寨卡病毒E蛋白结合疫苗及其制备方法,具体步骤：1)将β-葡聚糖的邻位羟基氧化为醛基,得到氧化β-葡聚糖；2)加入连接桥化合物,与氧化β-葡聚糖中的醛基反应,得到含连接桥的β-葡聚糖；3)寨卡病毒E蛋白与含连接桥的β-葡聚糖进行反应,纯化得到寨卡病毒E蛋白结合疫苗。该疫苗能诱导产生高水平的细胞免疫应答和体液免疫应答。(The invention discloses a Zika virus E protein conjugate vaccine and a preparation method thereof, and the preparation method comprises the following specific steps: 1) oxidizing the ortho-position hydroxyl of the beta-glucan into aldehyde group to obtain oxidized beta-glucan; 2) adding a connecting bridge compound to react with aldehyde groups in the oxidized beta-glucan to obtain beta-glucan containing connecting bridges; 3) and reacting the Zika virus E protein with beta-glucan containing a connecting bridge, and purifying to obtain the Zika virus E protein conjugate vaccine. The vaccine can induce high-level cellular immune response and humoral immune response.)

1. A Zika virus E protein conjugate vaccine, characterized in that beta-glucan and Zika virus E protein are covalently bound through a linker bridge.

2. The Zika virus E protein conjugate vaccine of claim 1, wherein the linker bridge is a disulfide and hydrazone bond-containing linker bridge or a maleimide group-containing linker bridge.

3. The Zika virus E protein conjugate vaccine of claim 2, wherein the chemical structure of the connecting bridge comprising a disulfide bond and a hydrazone bond is:the chemical structure of the connecting bridge containing the maleimide group is as follows:

4. the method of preparing a Zika virus E protein conjugate vaccine of claim 1, comprising the steps of:

1) oxidizing the ortho-position hydroxyl of the beta-glucan into aldehyde group to obtain oxidized beta-glucan;

2) adding a connecting bridge compound to react with aldehyde groups in the oxidized beta-glucan to obtain beta-glucan containing connecting bridges;

3) and reacting the Zika virus E protein with beta-glucan containing a connecting bridge, and purifying to obtain the Zika virus E protein conjugate vaccine.

5. The method according to claim 4, wherein in step 2), the connecting bridge compound is aminoethyl-maleimide ester or pyridyldihydropyramide.

6. The method according to claim 4, wherein in the step 2), the concentration of the oxidized β -glucan is 1 to 5mg/mL, the concentration of the bridging compound is 0.1 to 0.5mg/mL, the mass ratio of the bridging compound to the oxidized β -glucan is 1 to 10, the reaction pH is 6.0 to 8.0, and the reaction is carried out at 2 to 40 ℃ for 1 to 24 hours.

7. The process according to claim 4, wherein in the step 3), the concentration of Zika virus E protein is 0.1 to 2.0mg/mL, the concentration of β -glucan having a connecting bridge is 0.5 to 5.0mg/mL, the mass ratio of β -glucan having a connecting bridge to Zika virus E protein is 0.5 to 20.0, the reaction pH is 6.0 to 8.0, and the reaction is carried out at 2 to 8 ℃ for 1 to 24 hours.

8. The method according to claim 4, wherein the Zika virus E protein is produced by the following method:

i) performing PCR amplification on the Zika virus E protein gene, performing double enzyme digestion, and inserting the product into a multiple cloning site of an expression vector to construct a recombinant vector;

ii) expressing the E protein in the Escherichia coli by the recombinant vector, and renaturing, separating and purifying the inclusion body in the Escherichia coli to obtain the Zika virus E protein.

9. The method for preparing according to claim 8, wherein step i) comprises the steps of:

according to the genetic sequence of envelope protein of Zika virus BeH818995 strain in GenBank, the GenBank serial number is KU365777, 6 histidine residues are fused at the C terminal of E protein gene sequence source for whole gene synthesis; the synthetic gene sequence is cloned into a pET21a expression vector and then transformed into an Escherichia coli competent cell top10 to construct a recombinant vector pET21 a-E.

10. The method of claim 8, wherein step ii) comprises the steps of:

transforming the recombinant vector pET21a-E into escherichia coli BL21(DE3), and screening positive clones by colony PCR and performing sequencing identification; activating thalli, inducing by isopropyl-beta-D-thiogalactoside, performing shake culture, and centrifugally collecting thalli; the thalli is suspended in buffer solution, the thalli is broken by ultrasonic in ice bath, and inclusion bodies are collected by centrifugation; washing with inclusion body washing liquid for three times, dissolving with inclusion body dissolving liquid in 37 deg.C water bath, and diluting at 4 deg.C for renaturation; the low-concentration protein renaturation solution was purified by a NiSepharose Fast Flow affinity chromatography column, and the elution peak corresponding to the Zika virus E protein was collected.

Technical Field

The invention relates to the field of biomedicine, in particular to a beta-glucan modification-based Zika virus recombinant protein conjugate vaccine.

Background

Zika virus is an RNA virus with an icosahedral structure and an envelope, and belongs to the genus flavivirus. The Zika virus is transmitted by Aedes, can infect nerve cells, and breaks through blood fetus, blood eye, blood testis and blood brain barrier, resulting in neonatal microcephaly and adult personality Ribis syndrome. In recent years, the outbreak of Zika epidemic in Central and south America and even worldwide has seen an unusually severe clinical manifestation. Because China has close personnel exchange with the regions where the Zika viruses are popular, the continuous occurrence of the input cases of the Zika viruses poses serious threats to the public health safety of China. At present, no effective means for preventing and treating Zika virus disease exists in the global scope. Even if the infection of Zika virus is prevented by killing mosquitoes, great difficulty exists in the implementation process, and especially in summer with high mosquito density, the bite of the mosquitoes cannot be completely prevented. Vaccination plays an important role in the prevention and control of infectious diseases. Therefore, the vaccination is the most economic and effective method for preventing the Zika virus disease, and can effectively inhibit the spread and the epidemic of the Zika virus disease.

The Zika virus vaccines currently under investigation include live attenuated vaccines, inactivated vaccines, nucleic acid vaccines, adenoviral vector vaccines, chimeric virus vaccines, recombinant protein vaccines, synthetic peptide vaccines, and the like. Several stages of research progress have been made in attenuated live and inactivated vaccines. However, these two types of vaccines have problems of low safety, poor specificity, and unclear components. For example, the live attenuated Zika virus vaccine has the potential for reversion to virulence. The DNA vaccine and the adenovirus vector vaccine can provide better immune protection for primates and have small toxic and side effects. However, DNA vaccines are susceptible to degradation upon entry into the body, and also risk being integrated into the host genome; the antibiotic gene on the plasmid may cause drug resistance of host cells, which brings difficulty to the prevention and treatment of bacterial diseases. The adenovirus vector has strong immunogenicity and poor targeting, and limits the clinical application of adenovirus vector vaccines.

The rapid development of genetic engineering technology has facilitated the development of recombinant protein vaccines. The recombinant protein vaccine has become one of the hot spots of vaccine research and development because of its advantages of high safety, definite components, strong specificity, easy preparation and the like. The E protein and the prM protein are two main Zika virus envelope proteins and are also important target antigens for the development of Zika virus vaccines. Wherein, the E protein forms a protrusion on the surface of the virus particle and plays a key role in the processes of virus adsorption, endocytosis, membrane fusion and cell emergence. Although the E protein is an ideal antigen of zika virus, it is poorly immunogenic, elicits a weak antibody and cellular immune response, and does not provide effective and sustained immune protection.

Vaccine adjuvants can nonspecifically enhance the immunogenicity of an antigen or alter the type of immune response. The aluminum adjuvant is a vaccine adjuvant which is most widely used at present, and can obviously enhance the humoral immune response of an organism. However, the aluminum adjuvant cannot stimulate the body to generate stronger cellular immune response, and is easy to cause pathological reaction at the inoculation position. In addition, vaccine adjuvants such AS MF59, AS03, Virosome and AS04 are also approved to be used, but all of the vaccine adjuvants have certain toxic and side effects. The polysaccharide adjuvant is more and more important and favored in the research of vaccine adjuvants in recent years due to the advantages of natural source, biodegradability, good biological safety and the like. Among them, beta-glucan is a major component of fungal cell wall, and has immunoregulatory and immunopotentiating effects. Beta-glucan is a polysaccharide formed by glucose through beta- (1 → 3) glycosidic bond, can recognize polysaccharide receptors on the surfaces of macrophages (such as CR3 and Dectin-1), activate immune cells (such as macrophages, monocytes, dendritic cells, natural killer cells and neutrophils), promote the secretion of cytokines (such as gamma-interferon, IL-2, IL-5 and IL-10) and improve the immune response level of the body.

The antigen delivery system can deliver the vaccine adjuvant and the antigen to immune cells (such as antigen presenting cells) of a body, so that the immunogenicity of the antigen is improved. For example, nanoparticles form nanoparticle vaccines by loading antigens and adjuvants, and exhibit strong immune response in mice. However, nanoparticle materials (such as carbon nanotubes and gold nanoparticles) have poor water solubility, are not easily degraded, have long-term toxicity, and are not easily produced on a large scale, which limits the clinical applications of nanoparticle vaccines. Covalent binding allows the vaccine adjuvant to bind to the antigen to form an antigen delivery system, which can deliver both to immune cells simultaneously, and be recognized, taken up and presented by the immune cells, thereby stimulating the body to generate a strong immune response. The recombinant protein vaccine (namely the recombinant protein conjugate vaccine) based on adjuvant covalent conjugation has the characteristics of good water solubility, easy degradation, low toxicity and easy large-scale production. By selecting proper antigens, vaccine adjuvants and covalent binding methods, the development of efficient Zika virus recombinant protein binding vaccines can be expected.

Disclosure of Invention

The invention aims to provide a beta-glucan modified Zika virus E protein conjugate vaccine, which gradually separates beta-glucan from E protein after reaching cells, so that the beta-glucan is prevented from shielding an epitope of the E protein, and the E protein is also prevented from shielding an adjuvant active site of the beta-glucan, so that an organism is stimulated to generate a higher-level cellular immune response and a higher-level humoral immune response.

In order to achieve the purpose, the invention adopts the following technical scheme:

a Zika virus E protein conjugate vaccine, beta-glucan and Zika virus E protein through the bridge covalent binding.

Preferably, the connecting bridge is a disulfide bond-and hydrazone bond-containing connecting bridge or a maleimide group-containing connecting bridge.

Further preferably, the chemical structure of the connecting bridge containing disulfide bond and hydrazone bond is:the chemical structure of the connecting bridge containing the maleimide group is as follows:

the invention also provides a preparation method of the Zika virus E protein conjugate vaccine, which comprises the following steps:

1) oxidizing the ortho-position hydroxyl of the beta-glucan into aldehyde group to obtain oxidized beta-glucan;

2) adding a connecting bridge compound to react with aldehyde groups in the oxidized beta-glucan to obtain beta-glucan containing connecting bridges;

3) and reacting the Zika virus E protein with beta-glucan containing a connecting bridge, and purifying to obtain the Zika virus E protein conjugate vaccine.

Preferably, in step 2), the connecting bridge compound is aminoethyl-maleimide ester or dithiopyridylpropanoyl hydrazine.

Preferably, in the step 2), the concentration of the oxidized beta-glucan is 1-5mg/ml, the concentration of the bridging compound is 0.1-0.5mg/ml, the mass ratio of the bridging compound to the oxidized beta-glucan is 1-10, the reaction pH value is 6.0-8.0, and the reaction is carried out at 2-40 ℃ for 1-24 hours.

Preferably, in the step 3), the concentration of the Zika virus E protein is 0.1-2.0mg/mL, the concentration of the beta-glucan containing the connecting bridge is 0.5-5.0mg/mL, the mass ratio of the beta-glucan containing the connecting bridge to the Zika virus E protein is 0.5-20.0, the reaction pH value is 6.0-8.0, and the reaction is carried out at 2-8 ℃ for 1-24 hours.

Preferably, the Zika virus E protein is prepared by the following method:

i) performing PCR amplification on the Zika virus E protein gene, performing double enzyme digestion, and inserting the product into a multiple cloning site of an expression vector to construct a recombinant vector;

ii) expressing the E protein in the Escherichia coli by the recombinant vector, and renaturing, separating and purifying the inclusion body in the Escherichia coli to obtain the Zika virus E protein.

Further preferably, step i) comprises the steps of:

according to the genetic sequence of envelope protein of Zika virus BeH818995 strain in GenBank, the GenBank serial number is KU365777, 6 histidine residues are fused at the C terminal of E protein gene sequence source for whole gene synthesis; the synthetic gene sequence is cloned into a pET21a expression vector and then transformed into an Escherichia coli competent cell top10 to construct a recombinant vector pET21 a-E.

Further preferably, step ii) comprises the steps of:

transforming the recombinant vector pET21a-E into escherichia coli BL21(DE3), and screening positive clones by colony PCR and performing sequencing identification; activating thalli, inducing by isopropyl-beta-D-thiogalactoside, performing shake culture, and centrifugally collecting thalli; the thalli is suspended in buffer solution, the thalli is broken by ultrasonic in ice bath, and inclusion bodies are collected by centrifugation; washing with inclusion body washing liquid for three times, dissolving with inclusion body dissolving liquid in 37 deg.C water bath, and diluting at 4 deg.C for renaturation; the low-concentration protein renaturation solution was purified by Ni Sepharose Fast Flow affinity chromatography, and the elution peak corresponding to the Zika virus E protein was collected.

The invention provides a beta-glucan modified Zika virus E protein conjugate vaccine, which is formed by covalently bonding beta-glucan and Zika virus E protein by using a hydrazone bond and a disulfide bond as a connecting bridge through a chemical modification method.

The invention relates to a preparation method of Zika virus E protein, which comprises the following steps:

(1) e protein gene sequence is selected, pET-21a (+) plasmid vector is constructed, and the plasmid vector is transformed into escherichia coli competent cells. The strain containing the E protein gene was selected by the plate coating method. And (3) carrying out amplification culture on the screened strains, carrying out induced expression, carrying out low-speed centrifugation, and collecting thalli.

(2) Resuspending the thallus, stirring uniformly, and then crushing the thallus by using an ultrasonic cell crusher. After the ultrasonic treatment is finished, the inclusion bodies and the supernatant are separated by a centrifugal separation mode. Taking the inclusion body, washing, adding an inclusion body dissolving solution, and performing water bath treatment to obtain an inclusion body denaturation solution. The inclusion body denaturation liquid is dripped into 10 times of the inclusion body renaturation liquid drop by drop. Finally, the mixture is stirred and renatured overnight at 4 ℃.

(3) And (3) separating and purifying the E protein renaturation solution by using a Ni Sepharose Fast Flow affinity chromatography, and removing impurity proteins to obtain high-purity E protein.

The invention relates to a preparation method of Zika virus E protein conjugate vaccine, which comprises the following steps:

(1) the E protein is provided with cysteine residues and is positioned on the surface of a protein molecule; the thiol group of cysteine can be used to covalently bind beta-glucan. Oxidizing beta-glucan with sodium periodate; adding aminoethyl-maleimide ester according to a certain proportion; the amino group of the aminoethyl-maleimide ester reacts with the aldehyde group of the beta-glucan under the reduction action of sodium cyanoborohydride; adding the E protein according to a certain proportion, and reacting the sulfydryl of the E protein with maleimide ester of beta-glucan to generate the combined vaccine (E-PS-1) without disulfide bonds and hydrazone bonds.

(2) Oxidizing beta-glucan with sodium periodate; adding dithiopyridine propionohydrazide according to a certain proportion; reacting a hydrazide group of the dithiopyridine propionohydrazide with an aldehyde group of the beta-glucan to generate a hydrazone bond; adding the E protein according to a certain proportion, and reacting the sulfydryl of the E protein with the disulfide bond of the beta-glucan to generate the combined vaccine (E-PS-2) with the disulfide bond and the hydrazone bond.

(3) The reaction mixture containing E-PS-1 or the reaction mixture containing E-PS-2 was purified by Superdex 200 gel filtration column. Two elution peaks appeared after elution after loading. Small elution peaks correspond to binders with higher binding. The large elution peak corresponds to E-PS-1 or E-PS-2. And collecting the corresponding elution peak of the E-PS-1 or the E-PS-2 to obtain the Zika virus E protein conjugate vaccine.

More specifically, the preparation method of Zika virus E protein comprises the following steps:

(1) based on the gene sequence of envelope protein (Genebank serial number: KU365777) of Zika virus BeH818995 strain in GenBank, 6 histidine residues were fused at the C-terminal of E protein gene sequence source (amino acid residues 1-409) to carry out whole gene synthesis;

(2) cloning the synthetic gene sequence into a pET21a expression vector, then transforming the synthetic gene sequence into an escherichia coli competent cell top10, and constructing a recombinant vector pET21 a-E;

(3) transforming the recombinant vector pET21a-E into escherichia coli BL21(DE3), and screening positive clones by colony PCR and performing sequencing identification;

(4) activating thalli, inducing by isopropyl-beta-D-thiogalactoside, performing shake culture, and centrifugally collecting thalli;

(5) the thalli is suspended in buffer solution, the thalli is broken by ultrasonic in ice bath, and inclusion bodies are collected by centrifugation;

(6) carrying out ultrasonic crushing on the thalli, centrifuging and collecting inclusion bodies, washing the inclusion bodies for three times by using an inclusion body washing solution, dissolving the inclusion bodies in a water bath at 37 ℃, and then diluting and renaturing the inclusion bodies at 4 ℃;

(7) the low concentration protein renaturation liquid is purified by Ni Sepharose Fast Flow affinity chromatography column, and the elution peak corresponding to E protein is collected.

A method of covalently binding β -glucan to zika virus E protein comprising the steps of:

(1) oxidizing beta-glucan by sodium periodate, and oxidizing hydroxyl at the ortho position of the beta-glucan into aldehyde group;

(2) adding aminoethyl-maleimide ester to react with aldehyde group of beta-glucan, introducing maleimide group into beta-glucan, wherein the concentration of oxidized beta-glucan is 1-5mg/ml, the concentration of aminoethyl-maleimide ester is 0.1-0.5mg/ml, the mass ratio of aminoethyl-maleimide ester to oxidized beta-glucan is 1-10, the reaction pH value is 6.0-8.0, and the reaction is carried out at 2-40 ℃ for 1-24 hours;

(3) adding E protein, reacting the sulfydryl of the E protein with maleimide ester of beta-glucan to generate a conjugate vaccine (E-PS-1) without a disulfide bond and a hydrazone bond, wherein the concentration of the E protein is 0.1-2.0mg/mL, the concentration of the beta-glucan is 0.5-5.0mg/mL, the mass ratio of the beta-glucan to the E protein is 0.5-20.0, the reaction pH value is 6.0-8.0, and the reaction is carried out at 2-8 ℃ for 1-24 hours;

(4) the conjugate vaccine was purified by Superdex 200 gel filtration column.

Another method for covalently binding β -glucan to zika virus E protein comprising the steps of:

(1) oxidizing beta-glucan by sodium periodate, and oxidizing hydroxyl at the ortho position of the beta-glucan into aldehyde group;

(2) adding dithiopyridine propionohydrazide to react with aldehyde groups of beta-glucan, introducing disulfide bonds and hydrazone bonds into the beta-glucan, wherein the concentration of oxidized beta-glucan is 1-5mg/ml, the concentration of the dithiopyridine propionohydrazide is 0.1-0.5mg/ml, the mass ratio of the dithiopyridine propionohydrazide to the oxidized beta-glucan is 1-10, the reaction pH value is 6.0-8.0, and the reaction is carried out at the temperature of 2-40 ℃ for 1-24 hours;

(3) adding E protein, and allowing the sulfydryl of the E protein to react with the disulfide bond of the beta-glucan to generate a conjugate vaccine (E-PS-2) with disulfide bonds and hydrazone bonds, wherein the concentration of the E protein is 0.1-2.0mg/mL, the concentration of the beta-glucan is 0.5-5.0mg/mL, the mass ratio of the beta-glucan to the E protein is 0.5-20.0, the reaction pH value is 6.0-8.0, and the reaction is carried out at the temperature of 2-8 ℃ for 1-24 hours;

(4) the conjugate vaccine was purified by Superdex 200 gel filtration column.

The invention relates to a beta-glucan modified Zika virus E protein conjugate vaccine which is constructed by using E protein as an antigen and beta-glucan as a vaccine adjuvant through covalent binding of the E protein and the beta-glucan. The vaccine can induce high-level cellular immune response and humoral immune response. Wherein, the covalent combination of beta-glucan is expected to prolong the retention time of E protein in vivo and increase the action time of vaccine and immune cells; covalent binding allows for simultaneous delivery of both to immune cells and recognition and uptake by immune cells. However, this combination also has the following problems: (1) the beta-glucan can shield the epitope of the E protein; (2) protein E also masks the adjuvant active site of β -glucan; (3) the epitope of the E protein can help beta-glucan specific B cells to activate T helper cells and generate beta-glucan specific antibodies. Therefore, the invention further uses a disulfide bond and a hydrazone bond as a connecting bridge to covalently combine beta-glucan and E protein to construct the Zika virus recombinant protein conjugate vaccine. The disulfide bond and hydrazone bond of the conjugate vaccine can solve the above 3 problems in immune cells by means of hydrolysis.

Compared with the prior art, the invention has the advantages that:

the design concept of the vaccine is innovative. The beta-glucan is used as an adjuvant of the Zika virus E protein conjugate vaccine and has originality; the vaccine takes disulfide bonds and hydrazone bonds as connecting bridges, and the combining mode enables the vaccine to be different from the traditional recombinant protein combined vaccine in the action mechanism and has novelty and effectiveness.

The vaccine technology of the invention has strong universality and can be used for developing recombinant protein conjugate vaccines of other viruses. In recent years, infectious diseases caused by pathogens such as viruses and bacteria have been aggravated in China. Traditional vaccines are not sufficient to address the challenge of infectious diseases. Therefore, there is a strong need in the country to reserve a highly versatile vaccine technology to cope with the possible public health emergencies. The vaccine technology of the invention is suitable for the research of other virus vaccines and can provide a feasible solution for preventing viral diseases. For example, S protein and β -glucan of the novel coronaviruses are covalently bound to a hydrazone bond through a disulfide bond, and can be used to prevent infection by the novel coronaviruses.

The combined vaccine E-PS-1 prepared by the invention has certain defects, for example, the antigen and the adjuvant of the recombinant protein combined vaccine can not be dissociated in cells, beta-glucan can shield the epitope of E protein, and E protein can also shield the adjuvant active site of the beta-glucan, and the interaction limits the improvement of the immunogenicity of the combined vaccine; therefore, the invention further adopts a connecting bridge containing a disulfide bond and a hydrazone bond to covalently combine the E protein and the beta-glucan, and glutathione and a slightly acidic environment in cells can respectively break the disulfide bond and the hydrazone bond, so that the E protein and the beta-glucan are fully dissociated, and the interaction is avoided, thereby stimulating an organism to generate stronger immune reaction.

Disulfide and hydrazone bonds reduce the production of beta-glucan specific antibodies. The covalent combination of the beta-glucan and the E protein can enhance the immunogenicity of the E protein; meanwhile, the epitope of the E protein can help B cells with specificity of beta-glucan to activate T-helper cells and generate antibodies with specificity of the beta-glucan, so that the immune activity of the vaccine is influenced and a certain toxic and side effect is generated. In response to this problem, the disulfide and hydrazone bonds between protein E and β -glucan dissociate both sufficiently within the cell, allowing β -glucan specific B cells to have a greatly reduced ability to activate T-helper cells, thereby avoiding or greatly reducing the production of β -glucan specific antibodies.

Drawings

FIG. 1 is the separation and purification of E protein, the left is the chromatogram of Ni Sepharose Fast Flow (5mL) purified inclusion body renaturation solution containing E protein, the right is the chromatogram of SDS-PAGE electrophoresis identification purified E protein, lane 1 is standard protein, lane 2 is E protein;

FIG. 2E-PS-1 is a schematic diagram of the preparation reaction;

FIG. 3E-PS-2 is a schematic diagram of the preparation reaction;

FIG. 4 separation and purification of E-PS-1 and E-PS-2. The reaction mixture containing E-PS-1 (left panel) and E-PS-2 (right panel) was purified by Superdex 200 gel filtration column (1.6 cm. times.60 cm), mobile phase PBS buffer (pH7.4), flow rate 2.0 ml/min, detection wavelength 280 nm;

FIG. 5 gel filtration column analysis of E-PS-1 and E-PS-2 purity. Detecting with analytical Superdex 200 gel filtration column (1cm × 30cm), mobile phase PBS buffer (pH7.4), flow rate of 0.5ml/min, and detection wavelength of 280 nm;

FIG. 6 circular dichroism spectroscopy for the structures of E-PS-1 and E-PS-2, the protein concentration is 0.1mg/mL, and the buffer system is 20mM phosphate buffer (pH 7.4);

FIG. 7 endogenous fluorescence Spectroscopy analysis of the structures of E-PS-1 and E-PS-2. The protein concentration is 0.1mg/mL, the buffer system is 20mM phosphate buffer (pH7.4), the excitation wavelength is 280nm, and the scanning range of the emission wavelength is 300-400 nm;

FIG. 8 Infrared Spectroscopy of the structures of E-PS-1 and E-PS-2;

FIG. 9E-PS-1 and E-PS-2 immune BALB/c mice after E protein specific antibody response, antibody titer by ELISA method, each group of 6 mice;

FIG. 10 beta-glucan specific antibody responses after immunization of BALB/c mice with E-PS-1 and E-PS-2, antibody titers being determined by ELISA, 6 mice per group;

FIG. 11ELISA assay for antigenicity of E-PS-1 and E-PS-2, (■) is the E protein group, (●) is the E-PS-2 group, (Delta) is the dithiothreitol-treated E-PS group;

FIG. 12 cytokine production stimulated after immunization of BALB/c mice with E-PS-1 and E-PS-2, panel a is a determination of IFN-. gamma.concentration; panel b shows the determination of IL-2 concentration; panel c shows the determination of IL-10 concentration; FIG. d is a graph showing the determination of TNF-. alpha.concentration, cytokine determination by ELISA, of 6 mice per group;

FIG. 13 metabolic changes of E-PS-1 and E-PS-2 in rats.

Detailed Description

Any feature disclosed in this specification may be replaced by alternative features serving equivalent or similar purposes, unless expressly stated otherwise. Unless expressly stated otherwise, each feature is only an example of a generic series of equivalent or similar features. The description is only for the purpose of facilitating understanding of the present invention and should not be construed as specifically limiting the present invention.

The invention is described in further detail below with reference to the figures and the detailed description.