The avirulent QU strain of fowl adenovirus, a member of duck adenovirus type 1, could be a potential vector in recombinant vaccine development. To identify a non-essential region for replication of QU virus, a 3.4 kb fragment near the E4 region of QU virus genome was amplified by PCR to construct a plasmid pADGFP, in which ORF1, ORF8 and ORF9 was replaced with a system expressing enhanced green fluorescence protein. Further, a recombinant virus rQUGFP was constructed by homologous recombination after pADGFP and QU virus were co-transfected into chick embryo fibroblast. The one step growth curve of the rQUGFP was found to be identical with that of parent QU virus and the TCID50 titers of different generation recombinants maintained stable. These findings suggest that the region including ORF1, ORF8 and ORF9 of QU virus genome is dispensable for virus replication, and the foreign gene inserted into virus genome can be efficiently and stably expressed. The work lays the foundation for further studies of developing this virus as a vector of recombinant vaccine.
Adenovirus E4 Proteins ; genetics ; immunology ; Animals ; Fowl adenovirus A ; classification ; genetics ; Genes, Viral ; genetics ; Genetic Vectors ; genetics ; Open Reading Frames ; genetics ; Recombination, Genetic ; Transfection ; Vaccines, Synthetic ; biosynthesis ; genetics ; immunology ; Viral Vaccines ; biosynthesis ; genetics ; immunology ; Virus Replication

OBJECTIVETo investigate the intracellular trafficking pathway of fusion protein epidermal growth factor-adenovirus early region 4 open reading frame 4 protein (EGF-E4orf4) internalized via epidermal growth factor (EGF) receptor and its affectivity on extracellular signal-regulated kinase (ERK) phosphorylation.

METHODSMDA-MB-231 and BGC823 cells were incubated with fluorescein isothiocyanate-EGF-E4orf4 or EGF at different time points. The specific molecular mark of early endosome or late lysosome was labeled by indirect immunofluorescence, and then colocalization staining was observed using confocal laser microscopy. The levels of ERK phosphorylation were detected by Western blot.

RESULTSThe fluorescent signal of fusion protein EGF-E4orf4 accumulated within the cells and congregated to the perinuclear region. A nucleus localization of the fusion protein was only at MDA-MB-231 cell. Colocalization of EGF-E4orf4 with early endosome/late lysosome was observed. EGF-E4orf4 stimulated ERK phosphorylation, which was most obvious 10 minutes after stimulation, and then gradually attenuated, which was similar to EGF stimulation but with a less decrease.

CONCLUSIONSInternalized EGF-E4orf4 can be slowly degraded via endosome-lysosome pathway. The action features of EGF-E4orf4 are remarkably different between MDA-MB-231 and BGC823 cells, which may help explain the differences in its anti-tumor potency and in the special selectivity toward different tumor cells.

Adenovirus E4 Proteins ; pharmacokinetics ; Cell Line, Tumor ; Epidermal Growth Factor ; pharmacokinetics ; Extracellular Signal-Regulated MAP Kinases ; metabolism ; Humans ; Phosphorylation ; drug effects ; Protein Transport ; Recombinant Fusion Proteins ; pharmacokinetics ; Viral Proteins ; pharmacokinetics