Bovine adenovirus type 3 virions cannot be rescued in vivo after full-length viral genome transfection in the absence of detectable polypeptide IX

Bovine adenovirus type 3 (BAdV3) is being used in the development of potential vehicles for gene therapy and vectored vaccine. To that end, a more comprehensive description of BAdV3 biology is essential. In this study, we focused on the role of pIX in BAdV3 virion rescue after full-length BAdV3 genome transfection. Initially, pIX deletion or initiation codon mutation abolished the production of progeny virions, which suggested that pIX was essential for the rescue of BAdV3 containing a full-length genome. Moreover, through transfection of a panel of pIX mutant BAdV3 genomes, we observed that the conserved N-terminus and the putative leucine zipper element (PLZP) were essential for virion rescue, whereas the C-terminus following the coiled-coil domain was non-essential. In addition, swap of the PLZP element and its following region of BAdV3 pIX to corresponding domains of human adenovirus type 5 (HAdV5) did not affect virion production, whereas swap of the entire pIX abolished production of progeny virions. We suggest that failure of the full-length BAdV3 pIX swap might be due to species specificity of its N-terminus region before the PLZP element.

Construction of recombinant infectious clones of HCoV-OC43 expressing green fluorescent protein and viral rescue / 中华微生物学和免疫学杂志

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.