Immunization against porcine epidemic diarrhea virus and vaccine development / 生物工程学报

Porcine epidemic diarrhea (PED) is a major disease of pigs that inflicts heavy losses on the global pig industry. The etiologic agent is the porcine epidemic diarrhea virus (PEDV), which is assigned to the genus Alphacoronavirus in the family Coronaviridae. This review consists of five parts, the first of which provides a brief introduction to PEDV and its epidemiology. Part two outlines the passive immunity in new born piglets and the important role of colostrum, while the third part summarizes the characteristics of the immune systems of pregnant sows, discusses the concept of the "gut-mammary gland-secretory IgA(sIgA) axis" and the possible underpinning mechanisms, and proposes issues to be addressed when designing a PEDV live vaccine. The final two parts summarizes the advances in the R&D of PEDV vaccines and prospects future perspectives on prevention and control of PEDV, respectively.

Production of high-purity recombinant human vascular endothelial growth factor (rhVEGF165) by Pichia pastoris / 生物工程学报

Vascular endothelial growth factor (VEGF165) is a highly specific vascular endothelial growth factor that can be used to treat many cardiovascular diseases. The development of anti-tumor drugs and disease detection reagents requires highly pure VEGF165 (at least 95% purity). To date, the methods for heterologous expression and purification of VEGF165 require multiple purification steps, but the product purity remains to be low. In this study, we optimized the codons of the human VEGF165 gene (vegf165) according to the yeast codon preference. Based on the Pichia pastoris BBPB vector, we used the Biobrick method to construct a five-copy rhVEGF165 recombinant expression vector using Pgap as the promoter. In addition, a histidine tag was added to the vector. Facilitated by the His tag and the heparin-binding domain of VEGF165, we were able to obtain highly pure rhVEGF165 (purity > 98%) protein using two-step affinity chromatography. The purified rhVEGF165 was biologically active, and reached a concentration of 0.45 mg/mL. The new design of the expression vector enables production of active and highly pure rhVEGF165 ) in a simplified purification process, the purity of the biologically active natural VEGF165 reached the highest reported to date.

The 40-91 aa sequence of porcine epidemic diarrhea virus ORF3 protein is the key structural domain controlling its location in cytoplasm / 生物工程学报

ORF3 protein, the single accessory protein encoded by porcine epidemic diarrhea virus (PEDV), is related to viral pathogenicity. In order to determine the cytoplasmic location signal of PEDV ORF3, we constructed a series of recombinant plasmids carrying full-length or truncated segments of PEDV DR13 ORF3 protein. When the acquired plasmids were transfected into Vero cells, expression and distribution of the EGFP-fused full-length ORF3 protein and its truncated forms in the cells were observed by laser confocal microscopy. The results showed that ORF3 protein or their truncated forms containing 40-91 aa segment including two transmembrane domains were localized in the cytoplasm, whereas ORF3 truncated peptides without the 40-91 aa segment were distributed in the whole cell (in both cytoplasm and nucleus). This suggests that the 40-91 aa is the key structural domain determining cytoplasmic location of PEDV ORF3 protein. The discovery provides reference for further clarifying intracellular transport and biological function of PEDV ORF3 protein.

Establishment and application of visual LAMP detection method of infectious bovine rhinotracheitis virus / 生物工程学报

Three pairs of primers were designed according to the conserved region of IBRV gB gene published in GenBank(GenBank Accession No. DQ006857.1) using the software Primer Explorer V4. The loop mediated isothermal amplification (LAMP) assay was established by optimization of the reaction system and then evaluated through sensitivity and specificity tests. In total 393 clinical specimens were detected for IBRV using the established LAMP assay performed at 65℃ for 50 min, which produced a ladder-like pattern of amplification bands and the detection result could be judged by color change. The sensitivity of the assay was 10 copies/μL plasmid DNA which was 1000 times higher than that by PCR method and equivalent to nested-PCR. There was no cross-reactivity of the assay with bovine viral diarrhea virus (BVDV), pseudorabies virus (PRV) and vesicular stomatitis virus (VSV). The positive rate of 301 nasal swabs and 92 serum specimens were 87.6% and 58.8%, respectively, which meant nasal swab specimen was more suitable for clinical IBRV detection by the method. The IBRV LAMP method established in this study has the advantages of visualization, quickness, specificity and sensitivity and be suitable for rapid detection of clinical IBRV detection on the spot.

Advances in reverse genetics to treat porcine epidemic diarrhea virus / 生物工程学报

Porcine epidemic diarrhea virus (PEDV) is one of the major etiologies responsible for the acute, highly contagious disease in the digestive tract of pigs, especially neonatal piglets. Since PEDV was first identified in Europe in the late 1970s, it has resulted in significant economic losses in many Asian swine-raising countries, including China. Recently, reverse genetics techniques including targeted RNA recombination, bacteria artificial chromosome system and in vitro ligation have been successfully used to manipulate the genome of PEDV, which providing new strategies for the clear delineation of the functions of the viral proteins, the mechanisms behind PEDV pathogenesis and the design of novel vaccines against PEDV. Here, we review the progresses of different reverse genetics platforms developed for PEDV and their applications, covering the roles of trypsin in PEDV propagation, functions of S and ORF3 protein and the development of next generation PED vaccines, and the perspectives of reverse genetics for PEDV.

Directed evolution of aflatoxin detoxifzyme in vitro by error-prone PCR / 生物工程学报

The experiment was conducted by directed evolution strategy (error-prone PCR) to improve the activity of aflatoxin detoxifzyme with the high-throughput horse radish peroxidas and recessive brilliant green (HRP-RBG) screening system. We built up a mutant library to the order of 10(4). Two rounds of EP-PCR and HRP-RBG screening were used to obtain three optimum mutant strains A1773, A1476 and A2863. We found that mutant A1773 had upper temperature tolerance of 70 degrees C and that its enzyme activity was 6.5 times higher than that of the parent strain. Mutant strains A1476 worked well at pH 4.0 and its enzyme activity was 21 times higher than that of the parent strain. Mutant A2863 worked well at pH 4.0 and pH 7.5, and its enzyme activity was 12.6 times higher than that of the parent strain. With DNA sequencing we found that mutant A1773 revealed two amino acid substitutions, Glu127Lys and Gln613Arg. Mutant A1476 revealed four amino acid substitutions: Ser46Pro, Lys221Gln, Ile307Leu and Asn471lle. Mutant A2863 revealed four amino acid substitutions: Gly73Ser, Ile307Leu, Va1596Ala and Gln613Arg. The results provided a useful illustration for the deep understanding of the relationship between the function and structure of aflatoxin detoxifzyme.

Construction of a cDNA Library and Cloning of an Arabinosidase cDNA from Armillariella tabescens / 中国生物工程杂志

The expression cDNA library of A. tabescens was constructed by SMART technique, which useλTriplEx2 as a vector. The titer and the percentage of the constructed library were about 1.0 × 106pfu/mland 98.3% respectively, and the titer and the capacity of the amplified library were about 3.1 × 108pfu/mland 4.2 × 1010. The library was used to provide expressed sequence tags (ESTs). 147 Expressed SequenceTaqs (ESTs) were gained from 176 clones, which were selected randomly and sequenced at the 5'end. Thesequences were submitted to the EMBL database. Blasting the sequences in the GenBank, 43 of them werefound that they have significant similarity with data in GenBank. EST AJ620046 was has significantsimilarity with the arabinosidase of Bacteroides thetaiotaomicron. Using SMART-RACE a full-length cDNA ofAJ620046 was successfully obtained. In order to initially characterize the biochemical properties ofAJ620046, the ORF of AJ620046 named AF was cloned and expressed in Pichia Pastoris yeast.Recombinant pHIL-S1-AF constructed by inserting AF into pHIL-S1 was transformed into Pichia PastorisGS115. Preliminary experiments indicated that AJ620046 was expressed as a 32 kDa protein in recombinantyeast.