Complex structures and diverse functions of nuclear bodies: a review / 生物工程学报

Nuclear bodies are membrane-free nuclear substructures that are localized in the mammalian nuclear matrix region. They are multiprotein complexes that recruit other proteins to participate in various cellular activities, such as transcription, RNA splicing, epigenetic regulation, tumorigenesis and antiviral defense. It is of great significance to clarify the functions and regulatory mechanisms of nuclear bodies to probe related diseases and virus-host interactions. This review takes several nuclear bodies associated proteins as examples, summarizes the formation process, structure and functions of nuclear bodies, and focuses on their important roles in antiviral infection. It is expected to provide new insight into host antiviral mechanisms.

Transport of alphaherpesviruses in neurons--axonal"shuttling" / 生物工程学报

After a long-term co-evolution, alphaherpesviruses have established mutual adaptability with their hosts. Some alphaherpesviruses have typical neurotropic characteristics, which have received extensive attention and in-depth research. Neurotropic alphaherpesviruses can break through the host barrier to infect neurons and multiply in large numbers in the neuron cell body to complete further proliferation or establish latent infection in the cell body. Either in the process of infecting neurons or further spreading, alphaherpesviruses will undergo transmission along axons or dendrites, so this process is an integral part of the life cycle of the viruses, and is also a key factor for the viruses to spread in nervous system. Therefore, studies on transportation of alphaherpesviruses in neurons will provide new insights of the viruses and promote the development of corresponding vaccines or targeted therapeutic pharmaceuticals. In addition, the neurotropism of alphaherpesviruses is conducive to the analysis of nerve circuits. Herein, the mechanisms of alphaherpesvirus transport in axons were reviewed, and the research direction and application of the transport of alphaherpesviruses in axons were put forward, which can provide reference for the prevention and control of alphaherpesviral infections.

Microfold cells-targeting antigen delivery: a promising strategy to enhance the efficacy of mucosal vaccines / 生物工程学报

The mucosae represent the first line of defense against the invasion of most pathogens, and the mucosal immune system plays a crucial role in the control of infection. Mucosal vaccination can trigger both humoral and cell-mediated immune responses mucosally as well as systemically. Hence, protective immune responses can be elicited effectively by mucosal vaccination. Microfold (M) cells being unique to the mucosal immune system can take up luminal antigens and initiating antigen-specific immune responses. The number of antigen uptake by M cells is directly related to the immune efficacy of mucosal vaccines. Utilizing M cell ligands, M cells-targeting antigen delivery can achieve highly effective mucosal immune responses. The strategy of targeted delivery of antigens to M cells and its applications can be used for the improvement of mucosal immune responses and the development of mucosal vaccines. Despite these efforts, successful development of safe and effective mucosal vaccines remains a big challenge and needs a long way to go, and provably still resort to further researches on cellular properties and functions as well as mucosal immune mechanisms.

Generation and characterization of recombinant classical swine fever virus C-strain expressing the cap protein of porcine circovirus type 2 / 生物工程学报

Classical swine fever (CSF), caused by classical swine fever virus (CSFV), is a devastating viral disease in swine, leading to significant economic losses to the pig husbandry. C-strain is one of the best modified live vaccines against CSF. The vaccine is highly safe and efficacious and can provide rapid and complete protection against essentially all genotypes of CSFV. Co-infections of pigs with CSFV and porcine circovirus type 2 (PCV2) occur frequently in the field, making it difficult to control the associated diseases. Here, a recombinant C-strain rHCLV-Cap expressing the Cap protein of PCV2 was constructed and evaluated in vitro and in vivo. The recombinant had comparable phenotypes to C-strain in cell cultures and rabbits. At ten days post-immunization, anti-E2, but not anti-Cap, antibodies were detected in the rabbits inoculated with the recombinant virus. Our study warrants further work to construct C-strain-based bivalent vaccines.

Prevention, control and vaccine development of African swine fever: challenges and countermeasures / 生物工程学报

African swine fever (ASF) is a hemorrhagic and devastating infectious disease of pigs caused by African swine fever virus (ASFV), with mortality up to 100%. The first ASF outbreak occurred in China in August 2018, followed by 69 cases of ASF in 18 provinces in more than three months, causing a heavy burden to the pig industry. Based on the global epidemic situation of ASF and the experience of prevention and control in other countries, the ASF control and eradication situation in China is extremely complex and serious. The availability of effective and safe ASF vaccines is an urgent requirement to reinforce control and eradication strategies. Therefore, this article starts with the latest findings of ASFV, summarizes the progress in prevention and control strategies and vaccine approaches for ASFV. We also discuss the challenges of preventing and controlling ASF, focusing on current vaccine strategies, the gaps, future research directions, and key scientific issues in commercial applications. We hope to provide basic information for the development of vaccines and prevention control strategies against this disease in China.

New-concept animal vaccines emerging in recent years / 生物工程学报

Animal infectious diseases pose a serious and continuing threat to the animal health and cause huge economic losses throughout the world. Vaccination is one of the most effective solutions to prevent and control animal infectious diseases. With the development of biotechnologies and the need for disease prevention and control, the focus of vaccine research has been shifted to the development of safe, efficient, broad-spectrum, low-dose and marker vaccines. Novel vaccines capable of inducing high levels of both humoral and cellular immune responses are promising to provide more efficient protection against animal infectious diseases. This minireview summarizes the development, applications, advantages and disadvantages of new-concept animal vaccines emerging in recent years, including mucosal vaccines, long-acting and fast-acting vaccines, chimeric vaccines, nanoparticle vaccines, and so on. Furthermore, we discuss future directions of the vaccines, in order to provide new insights for animal vaccine development.

Alphavirus replicon-vectored plasmid DNA-based vaccine elicits protective immunity against classical swine fever virus / 生物工程学报

We have shown previously that a Semliki Forest virus (SFV) replicon vectored DNA vaccine (pSFV1CS-E2) expressing the E2 glycoprotein of classical swine fever virus (CSFV) conferred full protection for pigs immunized three times with 600 microg of the vaccine. This study aims to evaluate the efficacy of the DNA vaccine with lower dosage and fewer inoculations. Pigs were immunized twice with 100 microg pSFV1CS-E2 (n = 5) or control plasmid pSFV1CS (n = 3), respectively. Pigs immunized with pSFV1CS-E2 developed high titers of specific neutralizing antibodies against CSFV after the booster, and the antibody titers increased rapidly upon challenge. The immunized animals showed no clinical symptoms except short-term fever and low-level viremia, whereas the control pigs immunized with the control plasmid produced no detectable antibody before challenge and showed obvious clinical signs following challenge, and 2 pigs died on 10 or 11 days post-challenge. All control animals developed extended viremia as detected by nested RT-PCR and real-time RT-PCR. Severe pathologic lesions typical of CSFV infection were observed at necropsy. We conclude that the alphavirus replicon-vectored DNA-based vaccine can be potential marker vaccine against CSFV.

Selection and inhibitory effect analysis of siRNAs specific to ORF2-4 of porcine reproductive and respiratory syndrome virus / 生物工程学报

RNA interference (RNAi) is a powerful tool in gene function research. In order to investigate the role of GP2, GP3 and GP4 of porcine reproductive and respiratory syndrome virus (PRRSV) in the viral replication, small interference RNAs (siRNAs) directed to ORF2, ORF3 and ORF4 were designed and 12 short hairpin RNA (shRNA) expression vectors were constructed (designed as 21,22,23,24,31,32,33,34,41,42,43 and 44). Cells treated with shRNA expression vectors were infected by PRRSV. The effective shRNA expression vectors were selected by fluorescent quantatitive PCR (FQ-PCR). The virus titer of supernatant of the cells treated with effective shRNA expression vectors (23,24,31,34 and 41) were reduced by 184 to 4.65 folds compared with that of controls.

Differences in glycosylation of the E2 protein between virulent Shimen strain and a virulent C-strain of classical swine fever virus / 病毒学报

The E2 envelope glycoprotein of virulent Shimen strain and avirulent C-strain of Classical swine fever virus (CSFV) has 5 and 6 potential glycosylation sites, respectively, and the potential glycosylation site 986N is unique to C-strain. To study the differences in glycosylation between the virus pair, the E2 genes (removing signal sequence and transmembrane anchor regions) of the two strains fused with the melittin signal sequence were expressed in the Sf9 insect cells. The recombinant E2 proteins were secreted into the medium of Sf9 cells in dimer form with different molecular weight (MW). Deglycosylation of the recombinant E2 proteins by endo H and PNGase F showed that the deglycosalated Shimen-E2 and HCLV-E2 have the same MW, indicating that the different MW between Shimen-E2 and HCLV-E2 proteins came from different glycosylation. Site-directed mutagenesis in the potential glycosylation site at 986N demonstrated that the mutated Shimen-E2 protein had the same MW as the wild-type HCLV-E2 protein, while the mutated HCLV-E2 had the same MW as the wild-type Shimen-E2 protein. We suggest that the different MW between Shimen-E2 and HCLV-E2 is resulted from the different glycosylation on 986 N glycosylation site.

Recombinant Baculoviruses as Mammalian Cell Gene-delivery Vectors:a Review / 中国生物工程杂志

The baculovirus expression system has been used extensively for the expression of recombinant proteins in insect cells.Recently,recombinant baculoviruses containing mammalian cell-active promoter element have been used to transduce a broad spectrum of primary and established mammalian cells,including non-hepatic cells.Recombinant baculoviruses have been used successfully for transient or stable gene delivery in mammalian cells in vitro,while the efficiency of delivering gene in vivo is inhibited obviously by complements,but efforts have been made to overcome the problems,for instance,VSV-G-pseudotyped baculoviruses display complement resistance.The mechanism of the transduction is still not clearly understood,though many researches have been done.The baculovirus is able to replicate only in insect cells,but it is incapable of initiating replication cycle in mammalian cells,which guarantees high biosafety of this gene delivery system.In addition,this system is easily manipulated and able to carry large inserts.These attributes will undoubtedly lead to the increased application and continued development of this system for highly effective gene delivery into mammalian cells.

Expression of truncated gE gene of pseudorabies virus (PRV) and primary application in differential diagnosis of PRV vaccination and infection / 生物工程学报

With the application of gE gene deleted pseudarabies virus (PRV) vaccine worldwide, a corresponding differential diagnosis based on gE glycoprotein is needed in the project of PRV eradication. In this study, PRV gE gene without signal and transmembrane region was amplified by PCR and cloned into pGEX-6P-1, generated pGEX-gE. After transformation of BL21 with pGEX-gE, an expressed fusion protein(about 63kD) was identified by SDS-PAGE. The recombinant proteins are produced as inclusion bodies. By changing the inductive conditions, the formation of inclusion bodies was inhibited and tended to increase the percentage of soluble recombinant protein. The antigenic reactivity of the recombinant protein was confirmed by Western blotting with polyclonal antibodies against PRV. Using purified recombinant tgE as antigen, an ELISA was developed to detect sera of PRV infected pigs and sera of pigs immunized with gE-deleted PRV vaccine. The total of 400 serum samples collected from field were comparatively tested with the tgE-ELISA and a commercial competitive ELISA based on monoclonal antibody against gE, the results indicated that the coincidental rate between the two tests is about 94%.

Multi-epitope DNA vaccines against avian influenza in chickens / 生物工程学报

Multiple epitopes from one or more viruses can be lined up and co-expressed in one vector to generate multi-epitopes DNA vaccines. In the study, four recombinant plasmids were constructed based on HA and NP gene of avian influenza virus (AIV) (H5N1): (1) pIRES/HA, carrying the complete HA gene; (2) pIRES/tHA, carrying a truncated HA gene fragment of major neutralizing antigenic epitopes; (3) pIRES/tHA-NPep, in which three CTL epitopes of NP gene of AIV were fused to the truncated HA from the C-terminal; and (4) pIRES/tHA-NPep-IFN-gamma, which was constructed by replacing neo gene in pIRES/ tHA-NPep with IFN-y of chicken. Fifty five SPF chickens were randomly divided into five groups and immunized with the above four constructs and control plasmid. Each chicken was intramuscally immunized with 200 microg plasmid DNA three times in a two-week interval. Two weeks after the third immunization, chickens were injected with H5N1 subtype avian influenza virus. Before the virus loading no detectable antibodies to HA were found in the chicken serum; but high levels of HI antibodies were detected in the serum of the survived chickens. The percentages of CD4+ and CD8+ T lymphocyte in peripheral blood of immunized chickens increased steadily after the vaccination. After virus loading all chickens in the control group died within three to eight days, and the survival rates of the four DNA vaccine groups were as follows: pIRES/HA, 54.5%; pIRES/tHA, 30%, pIRES/ tHA-NPep, 36.3%, pIRES/tHA-NPep-IFN-gamma, 50%. These results indicated that multi-epitopes DNA immunization can induce immune response and protect chickens from homologous virus loading.