Expression of tick-borne encephalitis virus prM-E protein in insect cells and studies on its antigenicity / 中华实验和临床病毒学杂志

<p><b>BACKGROUND</b>To express the prM-E protein in Sf9 cells, and lay a basis for further study on the function of the viral proteins and development of specific diagnostic reagents.</p><p><b>METHODS</b>The recombinant prM-E protein of tick-borne encephalitis virus was expressed in insect cell Sf9 by RT-PCR amplification of prM-E gene, construction of donor plasmid of Bac-to-Bac baculovirus expression system, homologous recombination of donor plasmid with bacmid DNA at the site of Tn7 and transfection of insect cell Sf9.</p><p><b>RESULTS</b>Recombinant subviral particles, about 30 nm in diameter, consisting of prM-E were observed by electron microscope in the supernatant of infected cells, which indicated that infected cells released virus-like particles (VLPs) into the culture medium. The results of Western-blot and the indirect immunofluorescence assay (IFA) showed that the recombinant proteins retained antigenic and conformational structures similar to those of native virus proteins. Using the recombinant prM-E as antigens to detect samples of patient sera by ELISA and IFA, all of 16 sera from patients with tick-borne encephalitis were positive and all of 6 sera from other patients were negative.</p><p><b>CONCLUSION</b>The prM-E protein expressed in insect cells retains good antigenicity.</p>

Comparison and discrimination of the biological characteristics between West Nile virus and Japanese encephalitis virus / 中华实验和临床病毒学杂志

<p><b>BACKGROUND</b>To compare the biological characteristics of West Nile virus (WNV) and Japanese encephalitis virus (JEV), including cells sensitivity, pathogenicity, viral morphology, as well as the results of immunological and molecular biological detection.</p><p><b>METHODS</b>Cytopathic effect (CPE) and pathogenicity were observed in C6/36 cells and in suckling mice inoculated intracerebrally with the WNV or JEV, respectively. The sliced tissue samples for electron microscopic examination were prepared for the morphologic observation of the viruses. Serum antibody to WNV or JEV was detected using indirect immunofluorescence assay (IFA), and the viral RNA was analyzed by RT-PCR method.</p><p><b>RESULTS</b>WNV or JEV-caused CPE was characterized by cell fusion and cell shedding, respectively. There was no significant difference in the pathogenicity to suckling mice between WNV and JEV. The morphologic observation showed that the shape and size of the two virions were similar. WNV and JEV were found to have antigenic cross-reactivity. The viral RNA could be detected from both WNV and JEV samples with universal primer set, but only nucleoside fragments of corresponding virus could be amplified when specific primers were used.</p><p><b>CONCLUSION</b>CPE in C6/36 cell and detection of the viral RNA should be useful in discrimination of WNV and JEV, and simultaneously examining the titers of serum antibodies against WNV and JEV may be helpful to diagnosis of infection with these agents.</p>

Ultrastructural characteristics of SARS associated virus in infected cells / 中华病理学杂志

<p><b>OBJECTIVE</b>Electron microscopical study of infected cells to identify the pathogenic agent of SARS.</p><p><b>METHODS</b>Vero E6 cells infected with lung autopsy samples or nasopharyngeal swabs from SARS patients of Beijing and Guangzhou were inoculated. The supernatant and cultured cells exhibiting identifiable cytopathic effect (CPE) were prepared for electron microscopic study.</p><p><b>RESULTS</b>Examination of CPE cells on thin-section revealed characteristic coronavirus particles within the cisternae of endoplasmic reticulum, Golgi apparatus, vesicles and extracellular space. They were mainly spherical or oval in shape, annular or dense, about 80 nm in diameter. Negative-stain electron microscopy identified coronavirus particles in culture supernatant, 80 - 120 nm in diameter, with club-shaped surface projections. Elongated, rod-, kidney- or other irregular shaped virons with the size of 100 - 200 nm by 60 - 90 nm were also found in the cultured cells infected with the lung samples from the Guangdong patients. Infectious virons entered cells by endocytosis or membrane fusion and released through a budding process.</p><p><b>CONCLUSION</b>These data indicate a novel coronavirus as the causative agent of SARS. Most viral particles showed typical characteristics of coronavirus. The potential role of special shape viruses is expected to be further investigated.</p>