Expression,purification and immunogenicity evaluation of recombinant HPV58 virus-like particles / 中国生物制品学杂志

@#Objective To prepare recombinant human papillomavirus 58 L1 protein virus-like particles(HPV58 LI VLPs)in Pichia pastoris and immunize mice with the purified product to evaluate the immunogenicity of HPV58 L1 VLPs.Methods The HPV58 L1 multi-copy expression plasmid was constructed and transformed into Pichia pastoris KM71.The highly expressed Pichia pastoris engineering strain was screened and cultured in 5 L fermenter.The expressed HPV58 L1 VLPs were isolated and purified,which were then used to immunize 80 female BALB/c mice at different doses by intraperitoneal injection.After four weeks,the immune effect was evaluated by median effective dose(ED_(50)).Results Restriction analysis results showed that HPV58 L1 expression vectors were constructed correctly.Western blot,amino acid sequencing and transmission electron microscopy(TEM) results showed that HPV58 L1 protein was correctly expressed in Pichia pastoris and could self-assemble into VLPs at a diameter of about 50 nm.After purification by ion exchange and size exclusion chromatography,the HPV58 L1 VLPs reached a purity above 95%,and the ED_(50) in mouse model was 0.009 μg.Conclusion Recombinant HPV58 L1 VLPs with good immunogenicity were successfully prepared by using Pichia pastoris.

Evaluation of the humoral immunity in mice induced by foot-and-mouth disease virus-like particles-ZIF-8 complexes with different sizes / 生物工程学报

To further enhance the immune effect of the foot-and-mouth disease (FMD) virus-like particles (VLPs) vaccine, this study prepared FMDV VLPs-zeolitic imidazolate (framework-8, ZIF-8) complexes with different particle sizes. We used a biomimetic mineralization method with Zn2+ and 2-methylimidazole in different concentration ratios to investigate the effect of size on the immunization effect. The results showed that FMDV VLPs-ZIF-8 with three different sizes were successfully prepared, with an approximate size of 70 nm, 100 nm, and 1 000 nm, respectively. Cytotoxicity and animal toxicity tests showed that all three complexes exhibited excellent biological safety. Immunization tests in mice showed that all three complexes enhanced the titers of neutralizing and specific antibodies, and their immune effects improved as the size of the complexes decreased. This study showed that ZIF-8 encapsulation of FMDV VLPs significantly enhanced their immunogenic effect in a size-dependent manner.

Construction of foot-and-mouth disease virus like particles-induced expression vectors and screening of BHK-21 cell pools / 生物工程学报

Transient expression is the major method to express foot-and-mouth disease virus (FMDV) capsid proteins in mammalian cells. To achieve stable expression of FMDV capsid proteins and efficient assembly of virus like particles (VLPs) in cells, the plasmids of piggyBac (PB) transposon-constitutive expression and PB transposon-tetracycline (Tet) inducible expression vectors were constructed. The function of the plasmids was tested by fluorescent proteins. By adding antibiotics, the constitutive cell pools (C-WT, C-L127P) expressing P12A3C (WT/L127P) genes and the inducible cell pools (I-WT, I-L127P) expressing P12A3C (WT/L127P) genes were generated. The genes of green fluorescent protein, 3C protease and reverse tetracycline transactivator (rtTA) were integrated into chromosome, which was confirmed by fluorescence observation and PCR testing. The cell pool I-L127P has a stronger production capacity of capsid proteins and VLPs, which was confirmed by Western blotting and enzyme linked immunosorbent assay (ELISA), respectively. In conclusion, inducing the chromosomal expression of FMDV capsid proteins was firstly reported, which may facilitate the technical process of mammalian production of FMDV VLPs vaccine and the construction of mammalian inducible expression systems for other proteins.

Preparation of bovine viral diarrhea disease virus 1 virus-like particles and evaluation of its immunogenicity in a guinea pig model / 生物工程学报

In order to obtain virus-like particles (VLPs) for prevention of bovine viral diarrhea virus 1 (BVDV-1), the C-Erns-E1-E2 region was cloned into a pFastBacDaul vector for generating the recombinant Bacmid-BVDV-1 in DH10Bac Escherichia coli. The recombinant baculovirus Baculo-BVDV-1 was produced by transfecting the Sf9 cells with Bacmid-BVDV-1. The expressed protein and the assembled VLPs were determined by immunofluorescence, Western blotting and electron microscopy. Guinea pigs were immunized with inactivated VLPs coupled with the Montanide ISA-201 adjuvant. The immunogenicity of VLPs was evaluated by monitoring the humoral immune response with neutralizing antibody titer determination, as well as by analyzing the cell-mediated immune response with lymphocyte proliferation assay. The protective efficacy of VLPs was evaluated by challenging with 106 TCID50 virulent BVDV-1 strain AV69. The results showed that the recombinant Baculo-BVDV-1 efficiently expressed BVDV structural protein and form VLPs in infected Sf9 cells. The immunization of guinea pigs with VLPs resulted in a high titer (1:144) of neutralizing antibody, indicating an activated cellular immunity. Significantly lower viral RNA in the blood of the post-challenged immunized guinea pigs was observed. The successful preparation of BVDV VLPs with insect cell expression system and the observation of the associated immunogenicity may facilitate further development of a VLPs-based vaccine against BVD.

Effect of amino acid site modification on stability of foot-and-mouth disease virus-like particles / 生物工程学报

The stability of virus-like particles (VLPs) is currently the main factor affecting the quality of foot-and-mouth disease VLPs vaccines. In order to further improve the quality of the VLPs vaccine of foot-and-mouth disease (FMD), three amino acid modification sites were designed and screened through kinetic analysis software, based on the three-dimensional structure of FMDV. The three mutant recombinant plasmids were successfully prepared by the point mutation kit, transformed into Escherichia coli strain BL21 and expressed in vitro. After purification by Ni ion chromatography column, SDS-PAGE proved that the three amino acid mutations did not affect the expression of the target protein. The results of the stability study of three FMD mutant VLPs obtained by in vitro assembly show that the introduction of internal hydrophobic side chain amino acids made the morphology of VLPs more uniform (N4017W), and their stability was significantly improved compared to the other two VLPs. The internal hydrophobic force of the capsid contributes to the formation of VLPs and helps to maintain the stability of the capsid, providing new experimental ideas for improving the quality of VLPs vaccines, and helping to promote the development of VLPs vaccines.

Generation and immunogenicity evaluation of Senecavirus A virus-like particles / 生物工程学报

To develop Senecavirus A (SVA) virus-like particles (VLPs), a recombinant prokaryotic expression plasmid pET28a-SVA-VP031 was constructed to co-express SVA structural proteins VP0, VP3 and VP1, according to the genomic sequence of the field isolate CH-FJ-2017 after the recombinant proteins were expressed in E .coli system, and purified by Ni+ ion chromatographic method. The SVA VLPs self-assemble with a high yield in vitro buffer. A typical VLPs with an average diameter of 25-30 nm which is similar to native virions by using TEM detection. Animals immunized by SVA VLPs shown that the VLPs induced high titers neutralizing antibodies in Guinea pigs. This study indicated that the VLPs produced with co-expressing SVA structural proteins VP0, VP3 and VP1 in prokaryotic system is a promising candidate and laid an important foundation for the development of a novel SVA VLPs vaccine.

Preparation and immunogenicity evaluation of recombinant poliomyelitis type 2 virus-like particles / 中华微生物学和免疫学杂志

Objective:To express virus-like particles of poliovirus type 2 (PV2-VLP) in insect cells using a recombinant baculovirus expressing P1 and 3CD and to preliminarily evaluate its immunogenicity.Methods:Based on the codon preference of High 5 cells, the sequences of P1 gene and 3CD gene of PV2 were optimized and inserted into pUC57-Amp to construct pUC57-PV2-P1 and pUC57-PV2-3CD. UC57-PV2-P1s mutant that carried P1 gene mutation affecting thermostability was then constructed. Recombinant baculovirus strains of rBac-PV2-P1s-3CD and rBac-PV2-P1-3CD (wild type) were constructed using homologous recombination. The expression of target proteins was detected by Western blot. PV2-VLP was purified by ion exchange chromatography. The structure of VLP was observed under transmission electron microscopy to evaluate the assembly efficiency. The immunogenicity of PV2-VLP was assessed in a rat model.Results:The recombinant baculovirus with stable expression of P1s and 3CD proteins was successfully constructed. Western blot results showed that the yield of VLP was higher after thermostability mutation than that of the wild type. A three-dimensional structure with a diameter of about 30 nm was observed under electron microscopy, indicating that the VLP was successfully assembled. Animal experiment showed that the recombinant PV2-VLP had immunogenicity and could effectively induce the production of neutralizing antibodies.Conclusions:Effective VLP vaccines could be successfully prepared using the insect cell-baculovirus expression system, which provided reference for the development of polio VLP vaccine.

Humoral immune responses to different doses of bivalent norovirus vaccine in mice / 中华微生物学和免疫学杂志

Objective:To investigate the humoral immune response to GⅠ.1/GⅡ.4 norovirus (NoV) virus-like particle (VLP) vaccine of different doses in mice.Methods:The GⅠ.1/GⅡ.4 norovirus vaccine was diluted into four different concentrations, containing 50, 25, 8.3 and 2.8 μg/dose antigens, respectively. Aluminum hydroxide adjuvant was used in the control group. Ten 7-week-old BALB/c mice in each group were immunized intraperitoneally with 0.5 ml vaccine or adjuvant on 0 d and 21 d. Blood samples were collected on 35 d and the histoblood group antigen (HBGA) blocking titers of GⅠ.1 and GⅡ.4 antibodies in serum were detected. The differences in antibody levels between the groups were analyzed by SPSS23.0 software.Results:GⅠ.1 and GⅡ.4 HBGA blocking antibodies in 50, 25 and 8.3 μg/dose groups became positive on 35 d after the first dose vaccination. The geometric mean titers (GMT) of GⅠ.1 and GⅡ.4 HBGA blocking antibodies were 488 (95%CI: 249-955) and 489 (95%CI: 302-790) in 50 μg/dose group, 278 (95%CI: 106-728) and 738 (95%CI: 299-1 820) in 25 μg/dose group, 300 (95%CI: 158-570) and 486 (95%CI: 222-1 068) in 8.3 μg/dose group, respectively. The positive rates of GⅠ.1 and GⅡ.4 blocking antibodies in 2.8 μg/dose group were 40% and 70% and the GMT were 23 (95%CI: 10-51) and 85 (95%CI: 24-304), respectively. The GⅠ.1 and GⅡ.4 blocking antibodies in the control group were negative. Statistically significant differences in antibody levels were found between 50, 25, 8.3 μg/dose groups and the control group ( P<0.05), as well as in GⅠ.1 blocking antibodies between 50, 25, 8.3 μg/dose groups and 2.8 μg/dose group ( P<0.05). GⅡ.4 antibody level in 25 μg/dose group was statistically different from that in 2.8 μg/dose group ( P<0.05). Conclusions:GⅠ.1/GⅡ.4 norovirus VLP vaccine at (50-8.3) μg/dose could induce humoral immune response in mice.

Preparation and characterization of HBc virus like particles with site-directed coupling function / 生物工程学报

Hepatitis B virus core protein can self-assemble into icosahedral symmetrical viral-like particles (VLPs) in vitro, and display exogenous sequences repeatedly and densely on the surface. VLPs also have strong immunogenicity and biological activity. When the nanoparticles enter the body, they quickly induce specific humoral and cellular immune responses to exogenous antigens. In this study, we designed an HBc-VLPs that can be coupled with antigens at specific sites, and developed a set of efficient methods to prepare HBc-VLPs. Through site-specific mutation technology, the 80th amino acid of peptide was changed from Ala to Cys, a specific cross-linking site was inserted into the main immunodominant region of HBc-VLPs, and the prokaryotic expression vector pET28a(+)-hbc was constructed. After expression and purification, high purity HBc(A80C) monomer protein was assembled into HBc-VLPs nanoparticles in Phosphate Buffer. The results of particle size analysis show that the average particle size of nanoparticles was 29.8 nm. Transmission electron microscopy (TEM) showed that HBc-VLPs formed spherical particles with a particle size of about 30 nm, and its morphology was similar to that of natural HBV particles. The influenza virus antigen M2e peptide as model antigen was connected to Cys residue of HBc-VLPs by Sulfo-SMCC, an amino sulfhydryl bifunctional cross-linking agent, and M2e-HBc-VLPs model vaccine was prepared. The integrity of HBc-VLPs structure and the correct cross-linking of M2e were verified by cell fluorescence tracing. Animal immune experiments showed that the vaccine can effectively stimulate the production of antigen-specific IgG antibody in mice, which verified the effectiveness of the vaccine carrier HBc-VLPs. This study lays a foundation for the research of HBc-VLPs as vaccine vector, and help to promote the development of HBc-VLPs vaccine and the application of HBc-VLPs in other fields.

Construction, expression and identification of chimeric foot-and-mouth disease virus-like particles / 生物工程学报

To improve the specific recognition and presentation of virus-like particle (VLPs), and to develop immune-targeted VLPs vaccine, the gene fragment encoding OVA₂₅₇₋₂₆₄ peptide was inserted into the VP3 gene of foot-and-mouth disease virus (FMDV) between the 171th and 172th amino acids (aa) or 173th and 174th aa by reverse PCR. The recombinant proteins were expressed by using Escherichia coli and assembled into chimeric VLP (VLP(OVA)) in vitro after purification. The VLP(OVA) was measured by dynamic light scattering and transmission electron microscopy. The recombinant protein and the assembled VLPs were evaluated by Western blotting, enzyme-linked immunosorbent assay and laser scanning confocal microscopy to confirm the insertion of OVA₂₅₇₋₂₆₄ peptide into VP3 and its location. The results show that insertion of OVA₂₅₇₋₂₆₄ into the 173th and 174th aa of FMDV VP3 did not affect the assembly of VLPs. The VLP(OVA) in size was larger than VLPs, and the OVA₂₅₇₋₂₆₄ peptide was located on the surface of VLP(OVA).

Promotion of self-nucleic acid fragments on the assembly of foot-and-mouth disease virus-like particles / 生物工程学报

The special nucleic acid fragments, 5' untranslated region (5' UTR) and internal ribosome entry site (IRES) of foot-and-mouth disease virus (FMDV), which interact with the capsid proteins, were selected as scaffolds to investigate the assembly efficiency of foot-and-mouth disease (FMD) virus-like particles (VLPs). The assembled product was characterized by evaluation of particle size, surface potential, gel retardation assay, nuclease digestion experiments, size-exclusion chromatography, transmission electron microscopy and circular dichroism analysis. The results confirmed that the 5' UTR and IRES of FMDV co-assembled with the FMD VLPs and facilitated the assembly efficiency of FMD-VLPs. It demonstrates that the assembly efficiency of 75S particles of VLPs-5'UTR was significantly higher than those of the VLPs (P<0.001) and VLPs-IRES group (P<0.01). Comparatively the assembly efficiency of 12S particles of VLPs-IRES was significantly higher than those of the VLPs (P<0.000 1) and VLPs-5'UTR (P<0.000 1). It showed that the 5' UTR represented more effective in facilitating the assembly of VLPs. This study proposes an optimized strategy for improving the assembly efficiency of VLPs for the development of VLPs vaccine.

Virome: the next hotspot in microbiome research / 生物工程学报

Virome is the collective term for the viral collection or viral metagenomes that are distributed in various environments. Viruses can be found in bodies of water, glaciers, plants, animals, and even some viruses, which are classified as eukaryotes, prokaryotes and subviruses. Viruses play very important role in maintaining environmental homeostasis and ecosystem balance, and are especially closely related to human health. In recent years, with the advancement of sequencing technology and data analysis, we are able to gain more insights into the virome and explore its potential role in the ecological niche by metagenomic sequencing. A large amount of viral data have been obtained from glaciers, oceans, and various plants and animals, and numerous unknown viruses have been discovered. Virome has been studied mainly through metagenomic data mining, as well as virus-like particles separation and enrichment. To date, several different methods for viral isolation and enrichment exist, and numerous bioinformatic analyses of the virome have been performed. However, there is a lack of specific and complete reviews on the enrichment and data analysis methods for the virome. Thus, our review will summarize viral isolation and enrichment methods and data analysis, and present some of the landmark research conducted by the enrichment method, to provide a reference for researchers of interest and further advance the field of virome research.

Progress in vaccine development based on baculovirus expression vector system / 生物工程学报

Baculovirus expression vector system (BEVS) has been successfully applied to the over-expression of various proteins, thus providing sufficient materials for vaccine research. Compared to other systems, BEVS has many advantages: baculovirus solely being parasitic in invertebrates, the resultant products conferring high safety to mammalian, high expression level of recombinant proteins, preferable folding for eukaryotic protein, proper post-translational modification required for biological function, suitable for multiple genes co-expression and large-scale production with serum-free culture media. To better understand the advantages and prospective of BEVS for the vaccine research, this article will review the development of BEVS and its application on vaccine research.

Expression and purification of the chimeric virus-like particles displaying enterovirus 71 epitopes / 中华实验和临床病毒学杂志

Objective@#To study the expression and purification of the chimeric virus-like particles displaying epitopes of EV71 as a candidate of enterovirus 71 gene recombined vaccinet.@*Methods@#The fusion protein hepatitis B core (HBc)-SP70 was constructed by inserting SP70 into the main immunogenic region of truncated hepatitis B core antigen (HBcAg) sequence, expressed in E. Coli, and purified through sonication, ion exchange chromatography, CsCl cushion centrifugation and density gradient centrifugation. Then its antigenicity was detected by ELISA and Western blot assay.@*Results@#Recombinant plasmid pHBc-SP70 was successfully constructed. And the soluble fusion protein was efficiently expressed induced by IPTG. The purity of the chimeric virus-like particles (VLPs) was up to 90% after the purification process described in method . The purified fusion protein HBc-SP70 could be spontaneously folded and assembled into empty virus-like particles and react with the monoclonal antibodies against HBc and SP70.@*Conclusions@#The chimeric VLPs displaying epitopes of EV71 were efficiently expressed and purified in E. Coli. with excellent antigenicity, which laid a foundation for evaluation of the immune effect evoked by this EV71 gene recombined vaccine.

Efficient Humoral and Cellular Immune Responses Induced by a Chimeric Virus-like Particle Displaying the Epitope of EV71 without Adjuvant / 生物医学与环境科学（英文）

<p><b>OBJECTIVE</b>To eliminate the side effects of aluminum adjuvant and His-tag, we constructed chimeric VLPs displaying the epitope of EV71 (SP70) without His-tagged. Then evaluating whether the VLPs could efficiently evoke not only humoral but also cellular immune responses against EV71 without adjuvant.</p><p><b>METHODS</b>The fusion protein was constructed by inserting SP70 into the MIR of truncated HBcAg sequence, expressed in E. Coli, and purified through ion exchange chromatography and density gradient centrifugation. Mice were immunized with the VLPs and sera were collected afterwards. The specific antibody titers, IgG subtypes and neutralizing efficacy were detected by ELISA, neutralization assay, and EV71 lethal challenge. IFN-γ and IL-4 secreted by splenocytes were tested by ELISPOT assay.</p><p><b>RESULTS</b>HBc-SP70 proteins can self-assemble into empty VLPs. After immunization with HBc-SP70 VLPs, the detectable anti-EV71 antibodies were effective in neutralizing EV71 and protected newborn mice from EV71 lethal challenge. There was no significant difference for the immune efficacy whether the aluminum adjuvant was added or not. The specific IgG subtypes were mainly IgG1 and IgG2b and splenocytes from the mice immunized produced high levels of IFN-γ and IL-4.</p><p><b>CONCLUSION</b>The fusion proteins without His-tagged was expressed and purified as soluble chimeric HBc-SP70 VLPs without renaturation. In the absence of adjuvant, they were efficient to elicit high levels of Th1/Th2 mixed immune response as well as assisted by aluminum adjuvant. Furthermore, the chimeric VLPs have potential to prevent HBV and EV71 infection simultaneously.</p>

Evaluation of immune effects of virus-like particles of recombinant GⅡ. 17 norovirus / 中华微生物学和免疫学杂志

Objective To evaluate the immune effects of virus-like particles ( VLPs) assembled from the capsid protein VP1 of a recombinant norovirus ( NoV) GⅡ. 17 genotype. Methods The recombi-nant NoV GⅡ. 17 VP1 VLPs were purified, and then tested by SDS-PAGE and Western blot to analyze the purity. The size, morphology and diameter distribution of the recombinant VLPs were detected by transmis-sion electron microscopy ( TEM) and dynamic light scattering ( DLS) analyzer. The recombinant VP1 VLPs adsorbed by aluminium adjuvant were used to immunize BALB/c mice. Serum samples were collected after immunization. Specific antibody level and neutralizing antibody activity were evaluated with enzyme linked immunosorbent assay ( ELISA) and histo-blood group antigen ( HBGA)-VLP blocking test. Cross-reactivity of serum samples with GⅠ. 1 and GⅡ. 4 VP1 VLPs were detected. Moreover, cross-protection against GⅠ. 1 and GⅡ. 4 VP1 VLPs was analyzed. Results The purity of the recombinant NoV GⅡ. 17 VP1 VLP was greater than 90％ and specific bands were detected by Western blot. TEM images and DLS experiments showed that VLPs were 30-50 nm in size with good morphology and uniformity, indicating that the recombi-nant VLPs were similar to the wildtype virus. High titers of specific antibodies were detected in serum sam-ples of the immunized mice. A certain degree of cross-reactions between serum samples and VP1 VLPs of NoV GⅠ. 1 and GⅡ. 4 were observed, but no cross-protection was detected. Conclusion The recombinant GⅡ. 17 VP1 VLPs in combination with aluminum adjuvant can induce higher titers of HBGA blocking anti-bodies in mice, suggesting that it could be used as a candidate target antigen for norovirus vaccine.

Secreted expression of Japanese encephalitis virus prME in Pichia pastoris and immunogenicity evaluation of the virus-like particles in mice / 生物工程学报

The study was to express prME protein of Japanese encephalitis virus (JEV) in Pichia pastoris and then to evaluate the immunological properties of the recombinant protein in mice, so as to explore a new way for subunit vaccine development of JEV. The JEV prME gene was amplified by RT-PCR with genome RNA of JEV vaccine strain SA14-14-2 and subcloned into pPICZa-A vector, designated as pPICZα-prME. pPICZα-SprME was constructed same as pPICZα-prME besides with the additional 19 Aa signal peptides coding gene of the JEV cap protein C terminal. The linearized expression vector was integrated into the genome of Pichia pastoris X33 under the control of the alcohol oxidase (AOX1) promoter and induced with methanol during fermentation expression. The expression of JEV prME protein was identified by SDS-PAGE and Western blotting, and then it was purified by S-400 High Resolution HiPrep 16/60 Sephacry. The expressed products of Pichia pastoris were visualized by electron microscopy. In the immunization test, four groups of four-week old female mice were immunized subcutaneously with different doses purified JEV prME protein with complete Freund's adjuvant at a volumetric ratio of 1:1 and a control group was injected with sterile PBS. 10 μg/dose purified JEV prME protein mixing different doses nucleic acid adjuvant (Naa) was vaccinated in mice as the same mode. SDS-PAGE and Western blotting indicate that JEV prME was not cleaved between prM and E during secreted expression in Pichia pastoris. The purified recombinant prME was eluted in the first eluting peak which indicated that its molecular weight about 1×10⁶ Da to 20×10⁶ Da and may form a multimeric. Both the culture supernatant and the purified protein, examined by electron microscopy, we found to contain JEV virus like particles (VLPs) with diameters of 30-50 nm. The anti-JEV VLPs antibody titration reached peak at 3 wpi and still maintained in mice at 7 wpi inoculated with 10 μg and 15 μg prME. The strong antibody response was observed when the mice immunized with prME mixing nucleic acid adjuvant, which elicited high neutralizing antibody titer among 1:80 to 1:160. In conclusion, although JEV prME protein expressed in Pichia pastoris was not cleaved, which formed VLPs and showed efficient immunological properties in mice experiments.

Generation, characterization, and application in serodiagnosis of recombinant swine vesicular disease virus-like particles

Swine vesicular disease (SVD) is a highly contagious viral disease that causes vesicular disease in pigs. The importance of the disease is due to its indistinguishable clinical signs from those of foot-and-mouth disease, which prevents international trade of swine and related products. SVD-specific antibody detection via an enzyme-linked immunosorbent assay (ELISA) is the most versatile and commonly used method for SVD surveillance and export certification. Inactivated SVD virus is the commonly used antigen in SVD-related ELISA. A recombinant SVD virus-like particle (VLP) was generated by using a Bac-to-Bac baculovirus expression system. Results of SVD-VLP analyses from electron microscopy, western blotting, immunofluorescent assay, and mass spectrometry showed that the recombinant SVD-VLP morphologically resemble authentic SVD viruses. The SVD-VLP was evaluated as a replacement for inactivated whole SVD virus in competitive and isotype-specific ELISAs for the detection of antibodies against SVD virus. The recombinant SVD-VLP assay produced results similar to those from inactivated whole virus antigen ELISA. The VLP-based ELISA results were comparable to those from the virus neutralization test for antibody detection in pigs experimentally inoculated with SVD virus. Use of the recombinant SVD-VLP is a safe and valuable alternative to using SVD virus antigen in diagnostic assays.

Fermentation, purification and immunogenicity evaluation of hepatitis E virus-like particles expressed in Hansenula polymorpha / 生物工程学报

To develop a new recombinant hepatitis E vaccine, we used Hansenula polymorpha expression system to express recombinant hepatitis E virus-like particles (HEV VLPs), to construct a recombinant engineered strain HP/HEV2.3. The fermentation conditions and purification process were studied next. The first working seed lots were fermented in liquid culture, and the fermentation products were collected, then crushed, clarified, purified by ultrafiltration, silica gel adsorbed and desorbed, concentrated by ultrafiltration, purified by liquid chromatography and sterilized by filtration. The purity reached 99% with a yield of 33%. Electron microscopy analysis revealed that both the purified recombinant HEV VLPs from HP/HEV2.3 and natural hepatitis E virus particles appear identical of being 32 nm. The resulting DNA sequence obtained from VLPs is identical to the published HEV sequence. The SDS-PAGE analysis has revealed that the protein molecular weight of the HEV VLPs is 56 kDa, and the expression product HEV VLPs were accumulated up to 26% of total cellular protein. The expression level is 1.0 g/L. Western blotting, enzyme-linked immunosorbent assay (ELISA) results of the protein and ED₅₀ of the vaccine showed that the HEV VLPs have good antigenicity and immunogenicity. In summary, the recombinant HEV VLPs from Hansenula polymorpha can be used in the manufacture of a new genetically engineered vaccine against hepatitis E.

Cyclic guanosine monophosphate-adenosine monophosphate (cGAMP) enhances humoral immune responses against norovirus(GⅡ.4) virus-like particles / 中华微生物学和免疫学杂志

Objective To evaluate the immunopotentiating effect of cyclic guanosine monophos-phate-adenosine monophosphate (cGAMP) as an adjuvant on norovirus (GⅡ. 4) virus like particles (VLPs) in the development of norovirus vaccine. Methods BALB/c mice were intramuscularly immunized with norovirus (GⅡ.4) VLPs composed of capsid protein VP1 in combination with cGAMP or Al(OH)3. Norovirus VLPs-specific antibodies in serum were detected by ELISA. A synthetic histo-blood group antigen (HBGA)-VLPs blocking assay was used to analyze neutralizing antibodies against norovirus VLPs in serum samples. Results Immunization with norovirus VLPs in the presence of cGAMP induced a strong humoral immune response in BALB/c mice. Levels of specific IgG antibodies in serum induced by using cGAMP as the adjuvant were significantly higher than those induced by using Al(OH)3adjuvant when immunization of BALB/c mice with the same dosage of VLPs. The antibody level induced by 1 μg of VLPs in combination with cGAMP was equivalent to that elicited by 10 μg of VLPs combined with Al(OH)3adjuvant. Results of the synthetic HBGA-VLPs blocking assay showed that the blocking rate in cGAMP+VLPs immunization group were significantly higher than that in Al(OH)3+VLPs immunization group when using the same dosage of VLPs. No significant difference in blocking rate was observed between cGAMP+VLPs(1 μg) and Al(OH)3+VLPs (10 μg) immunization groups. Conclusion cGAMP significantly enhanced the specific humoral immune response induced by norovirus (GⅡ.4) VLPs in mice as compared with Al(OH)3adjuvant. It might be used as a novel adjuvant to replace the traditional aluminum adjuvant in the development of norovir-us vaccine.