ABSTRACT
In order to establish an infectious clone for CDV-3, a commercial vaccine strain of canine distemper virus for mink, to provide reference for the studies of pathogenesis and novel vaccine development of CDV. Thirteen pairs of primers were used to amplify the full-length genome of CDV-3 strain. Five long fragments were obtained based on single restriction site analysis of the whole genome of CDV-3 by RT-PCR. Five fragments were successively inserted into the multiple clone sites in the modified eukaryotic vector of pcDNA3.2 by restriction enzymes and splicing. Meanwhile, the hammerhead ribozyme and hepatitis delta virus ribozyme sequences were added to the beginning of F1 fragment and the ending of F5 fragment, respectively. Then, the full-length cDNA recombinant plasmid of CDV-3 was obtained and named as pcDNA3.2-CDV-3. In addition, three helper plasmids, expressing the N protein, P protein and L protein of the CDV-3 strain respectively, were constructed. The 293T cells were transfected with the full-length cDNA recombinant plasmid and three helper plasmids by Lipofectamine™ 2000. At 3 days post transfection, the supernatant was added to the monolayer of Vero cells to observe the typical syncytium of CDV. Indirect immunofluorescence and artificial label identification of recombinant virus rCDV-3 were conducted after the occurrence of lesions. Finally, the growth characteristics of wtCDV-3 and rCDV-3 were compared after passaging of rCDV-3. The identification of the full-length cDNA recombinant plasmid and three helper plasmids by restriction enzyme digestion and sequencing were consistent with expected. The Vero cells infected with the recombinant rCDV-3 showed typical syncytic. The identification of indirect immunofluorescence and labeled marker, and observation under electron microscope proved that the rCDV-3 was indeed rescued from the recombinant plasmid of pcDNA3.2-CDV-3. In comparison of the virus titers of wtCDV-3, rCDV-3 replicated massively and rapidly and reached the maximize virus titer of 10⁷·⁶⁶⁷ TCID₅₀/mL within 36 h post infection (p.i.) in Vero cells, while wtCDV-3 grew gradually to 10⁶·⁶⁶⁷ TCID₅₀/mL at 72 h p.i. in Vero cells. This reverse genetic system of CDV-3 strain has been established successfully, to provide reference for the studies of pathogenesis and novel vaccine development of CDV.
Subject(s)
Animals , Chlorocebus aethiops , Clone Cells , DNA, Complementary , Distemper Virus, Canine/genetics , Plasmids/genetics , Vero CellsABSTRACT
Objective@#To construct a stable infectious clone of live attenuated dengue virus (DENV) type 4 Ban18HK20 strain for better understanding the virulence determinants of DENV and improving the development of chimeric vaccines.@*Methods@#Specific primers were constructed according to the genome of Ban18HK20 strain and used to subclone six cDNA fragments, which were linked into a high-copy plasmid pSPTM to obtain a stable full-length cDNA clone of DENV. RNA was transcribed from the full-length cDNA in vitro and electrotransfected into Vero cells to recover the virus. Biological characteristics of the recovered virus were identified using plaque assay, indirect immunofluorescence assay, growth kinetics test and pathogenicity study in mouse brain. Genetic stability of the virus passaged 15 generations was studied using RT-PCR amplification.@*Results@#Restriction enzyme digestion and sequencing analysis indicated that the infectious clone was constructed successfully. The recovered virus was consistent with the parental virus in terms of plaque morphology, DENV E protein expression, growth characteristics and pathogenicity in mouse brain. Sequencing analysis showed that the recovered virus had the same genome sequence as the parental virus with good hereditary stability.@*Conclusions@#A stable infection clone of Ban18HK20 was constructed and a reverse genetics technology platform for DENV research was established.
ABSTRACT
As a pathogen causing many infectious diseases, Flavivirus genus arborvirus has caused public health emergencies worldwide and posed a serious threat to human health. Attenuated vaccine is the most effective vaccine type against Flavivirus genus arborvirus. The attenuated vaccines against yellow fever virus and Japanese encephalitis virus obtained by consecutive cell passages play an important role in preventing viral infections. Recently, reverse genetics technique has been used to modify the flavivirus genome to obtain the attenuated phenotype, and this technique has made significant progress in the development of Flavivirus genus arbovirus vaccines. This review summarizes the history and the current status of attenuated vaccine of Flavivirus genus arborvirus.
ABSTRACT
Reverse genetics approaches can directly manipulate the genome of virus at the gene level, making it possible to quickly, directly and thoroughly study the mechanisms of virus replication and pathogenesis. At present, many viruses of the family Reoviridae, such as mammalian orthoreovirus ( MRV) and bluetongue virus ( BTV) , have made great progress in basic viral research using the powerful tool of re-verse genetics. However, for members of the genus Rotavirus in the family Reoviridae, progress in the con-struction of reverse genetic systems has been slow. The remarkable reverse genetics system based on helper-viruses was established in 2006, and it was not until 2017 that the entirely plasmid-based reverse genetics system was successfully established. This paper briefly reviewed the development of reverse genetics systems for rotavirus and prospected the direction for future research in order to provide technical support for acceler-ating the basic research on mechanisms of rotavirus infection.
ABSTRACT
Abstract The open reading frame of a Brazilian bovine viral diarrhea virus (BVDV) strain, IBSP4ncp, was recombined with the untranslated regions of the reference NADL strain by homologous recombination in Saccharomyces cerevisiae, resulting in chimeric full-length cDNA clones of BVDV (chi-NADL/IBSP4ncp#2 and chi-NADL/IBSP4ncp#3). The recombinant clones were successfully recovered, resulting in viable viruses, having the kinetics of replication, focus size, and morphology similar to those of the parental virus, IBSP4ncp. In addition, the chimeric viruses remained stable for at least 10 passages in cell culture, maintaining their replication efficiency unaltered. Nucleotide sequencing revealed a few point mutations; nevertheless, the phenotype of the rescued viruses was nearly identical to that of the parental virus in all experiments. Thus, genetic stability of the chimeric clones and their phenotypic similarity to the parental virus confirm the ability of the yeast-based homologous recombination to maintain characteristics of the parental virus from which the recombinant viruses were derived. The data also support possible use of the yeast system for the manipulation of the BVDV genome.
Subject(s)
Animals , Cattle , Yeasts/genetics , Genome, Viral , DNA, Complementary , Diarrhea Viruses, Bovine Viral/genetics , Homologous Recombination , Virus Replication , Yeasts/metabolism , Cell Line , Open Reading Frames , Sequence Analysis, DNA , Diarrhea Viruses, Bovine Viral/physiology , Diarrhea Viruses, Bovine Viral/ultrastructureABSTRACT
Objective To rapidly construct hepatitis B virus(HBV)adefovir(ADV)‐resistant strain(RT A181T)infectious clone by using SOE‐PCR ,to observe the expression of recombinant plasmids in Huh7 cells and to establish the in vitro cell model of HBV ADV‐resistant strain(RT A181T) .Methods The conservative primers were designed ,the full‐length HBV genome was amplified from serum in the patients with ADV‐resistant chronic hepatitis B .Then ,the 1 .3‐fold genome‐length infectious clone pHBV1 .3 was constructed by using the SOE‐PCR technique ,which was transfected into human hepatoma cells Huh7 cell line .ELISA ,Western Blot and Real‐time PCR were adopted to detect infectious cloning replication and expression ,meanwhile the antiviral drugs lamivu‐dine(LAM ) and ADV were used to verify the infectious clone copy and inhibition of expression .Results The HBV ADV‐resistant infectious cloning plasmids pHBV1 .3 was successfully constructed .This plasmid could be effectively replicated ,transcripted and ex‐pressed in Huh7 cell lines .LAM could effectively inhibit the replication and expression of the infectious clone ,while ADV could not inhibit the replication and expression of the infectious clone .Conclusion The constructed infectious clone plasmids pHBV1 .3(RT A181T ) of HBV ADV‐resistant strain can efficiently replicate and express protein in vitro ,its transfected cells can be used in the study of HBV replication mechanism and antiviral study .
ABSTRACT
Objective To investigate the feasibility of using recombinant infectious clones of hu-man coronavirus OC43 (HCoV-OC43) as a vector for the expression of exogenous genes and to analyze the insertion sites. Methods Based upon pBAC-OC43FL, a full-length cDNA infectious clone of HCoV-OC43, three recombinant expression plasmids ( pBAC-OC43-GFPΔNS2, pBAC-OC43-GFPΔNS12. 9 and pBAC-OC43-N-GFP) were respectively constructed by replacing NS2 and NS12. 9 genes with the reporter gene en-coding the green fluorescent protein ( GFP ) and inserting the reporter gene after the N gene by using the overlapping-PCR and in vitro ligation. Reverse genetics techniques were used for viral rescue. All of the res-cued virus strains were characterized by immunofluorescence assay ( IFA) and Western blot ( WB) assay af-ter transfecting BHK-21 cells with the recombinant viruses. Results Two recombinant viruses, OC43-GFPΔNS2 and OC43-GFPΔNS12. 9, could be successfully rescued by transfection the BHK-21 cells with pBAC-OC43-GFPΔNS2 and pBAC-OC43-GFPΔNS12. 9 plasmids. The expressed GFP was observed in BHK-21 cells transfected with pBAC-OC43-GFPΔNS2 or pBAC-OC43-GFPΔNS12. 9 plasmids, but not in the cells transfected with the pBAC-OC43-N-GFP plasmid. An efficient and stable expression of GFP was observed in the pBAC-OC43-GFPΔNS2 plasmid-transfected cells. The 10th generation of OC43-GFPΔNS2 virus was ob-tained after repeated freezing and thawing. The expression of GFP and N protein were detected in cells infec-ted with the OC43-GFPΔNS2 virus after 10 passages. Conclusion The NS2 gene of HCoV-OC43 could be used as a promising insertion site of the pBAC-OC43 FL infectious clone for the expression of exogenous genes. This study might provide a platform for further researches on the replication of HCoV-OC43 and the development of human coronavirus-based vectors.
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Full-length dengue virus (DENV) cDNA clones are an invaluable tool for many studies, including those on the development of attenuated or chimeric vaccines and on host-virus interactions. Furthermore, the importance of low passage DENV infectious clones should be highlighted, as these may harbour critical and unique strain-specific viral components from field-circulating isolates. The successful construction of a functional Brazilian low passage DENV serotype 2 full-length clone through homologous recombination reported here supports the use of a strategy that has been shown to be highly useful by our group for the development of flavivirus infectious clones and replicons.
.Subject(s)
DNA, Complementary/genetics , Dengue Virus/genetics , RNA, Viral/genetics , Brazil , Cloning, Molecular , Molecular Sequence Data , Sequence Analysis, DNA , Virus ReplicationABSTRACT
Objective To construct 1.3-fold-overlength infectious clone of hepatitis B virus isolated from Chinese patients , observe the expression of plasmid in Huh7 of liver cancer cells and establish genome of HBV in vitro. Methods HBV DNA in serum was extracted from HBV patient. SOE-PCR was performed to produce a 1.3-fold-overlength genome of HBV. The plasmid was named pHBV1.3 (C). After that,pHBV1.3 (C) was transfected into Huh7 cells, HBV related viral antigens and DNA were detected by ELISA,Western Blot and Fluorescence quantitative PCR. Furthermore, adefovir dipivoxil, a clinic anti-viral drug, was utilized to test the sensitivity of the new infectious clone. Results An infectious clone of pHBV1.3 (C) was successfully constructed. HBV gene carried in pHBV1.3 (C) could be efficiently replicated and expressed in Huh7 cells. Adefovir could inhibit HBV replication in this HBV cell model. Conclusions A recombinant plasmid containing 1.3-fold-overlength of HBV genotype C was successfully constructed. This construct is competent to support viral transcription and replication in vitro , suggesting that infectious cells are expected to be a new model of HBV infection in vitro.
ABSTRACT
The bacteriophage T7 RNAP gene was amplified via PCR from -lysogen DE3, and the gene was cloned into pBABEpuro retrovial vector, a recombinant plasmid named as pT7BABEpuro was constructed and sequenced. Then the pT7BABEpuro and pVSV-G plasmids were cotransfected into GP2-293 packaging cells by liposomese, some pseudotype viruses were ingathered and transfected into IBRS-2 cell under polybrene. The IBRS-2 cell was propagated in DMEM with puromycin. The genome extraction from the cells transfected different times, the T7 RNAP gene was amplified from the genome by PCR, the mRNA of T7 RNAP protein expressed in IBRST7 cells was analyzed by RT-PCR, respectively, the results showed the T7 RNAP gene had been integrated into the chromosome of IBRS-2 cell and expressed stably at high level. To study whether T7 RNAP is of transcriptional activity in the established IBRST7 cell line, a plasmid pIERS-EGFP-ET with a reporter gene (EGFP) under control of the T7 promoter was constructed. IRES element from FMDV (for CAP-independent translation) was cloned into plasmid pET-43.1a-c(+) downstream of the T7 promoter sequence, then EGFP gene was cloned in frame downstream of the AUG codon of the FMDV IRES, resulting in the plasmid. IBRST7 cells were transfected with plasmid pIERS-EGFP-ET using lipfection, EGFP was expressed, the results showed the T7 RNAP in IBRST7 cells has transcriptional activity. IBRST7 cell line was directly transfected with linearized full-length cDNA of swine vesicular disease virus (SVDV) HK/70, infectious SVDV was efficiently recovered from the cDNA. The reverse genetic procedure is simplified to a faster, one step protocol to recover RNA virus and will be useful to understand the mechanisms of molecular pathology of RNA virus and develop effective vaccines.
ABSTRACT
The genetic analysis of herpesviruses has been a constant challenge, due to the large, complex genomes of herpesviruses and mutagenesis of viral genes by conventional recombination methods in cell culture. Recently, a completely new approach for full-length infectious clones of herpesviruses based on bacterial artificial chromosomes (BACs) has been developed. This technique allows the maintenance, propagation and genetic modification of the viral genome as a BAC plasmid in E.coli, thus making the procedures fast, safe and effective in prokaryotic cells. This technique also makes it possible for the reconstitution of viral progeny or mutants by transfection of the BAC plasmid into eukaryotic cells, thereby facilitating the analysis of viral gene functions in the context of genome. In this presentation, Epstein-Barr virus was used as an example to describe the principle, establishment of the technique and mutation introduction into the BAC plasmid, and to discuss the perspective in the use of BAC-cloned herpesviruses.