A highly attenuated SARS-CoV-2 related pangolin coronavirus variant has a 104nt deletion at the 3'-terminus untranslated region

SARS-CoV-2 related coronaviruses (SARS-CoV-2r) from Guangdong and Guangxi pangolins have been implicated in the emergence of SARS-CoV-2 and future pandemics. We previously reported the culture of a SARS-CoV-2r GX_P2V from Guangxi pangolins. Here we report the GX_P2V isolate rapidly adapted to Vero cells by acquiring two genomic mutations: an alanine to valine substitution in the nucleoprotein and a 104-nucleotide deletion in the hypervariable region (HVR) of the 3-terminus untranslated region (3-UTR). We further report the characterization of the GX_P2V variant in in vitro and in vivo infection models. In cultured Vero and BGM cells, the GX_P2V variant produced minimal cell damage and small plaques. The GX_P2V variant infected golden hamsters and BALB/c mice but was highly attenuated. Golden hamsters infected intranasally had a short duration of productive infection. These productive infections induced neutralizing antibodies against pseudoviruses of GX_P2V and SARS-CoV-2. Collectively, our data show that the GX_P2V variant is highly attenuated in in vitro and in vivo infection models. Attenuation of the variant is likely due to the 104-nt deletion in the HVR in the 3-UTR. This study furthers our understanding of pangolin coronaviruses pathogenesis and provides novel insights for the design of live attenuated vaccines against SARS-CoV-2.

Expression and identification of human EpCAM eukaryotic recombinant plasmid / 国际检验医学杂志

Objective To construct human EpCAM eukaryotic recombinant plasmid ,and to study the expression of EpCAM pro‐tein in HepG2 cells .Methods The recombinant plasmid ,named pcDNA3 .1(+ )‐EpCAMwas constructed by cloning EpCAM gene into eukaryotic vector pcDNA3 .1(+ ) .Then HepG2 cells were transfected with EpCAMrecombinant plasmid .The eukaryotic ex‐pression of EpCAM protein was verified by immunofluorescence ,Western Blotting and flow cytometry .Results The construction of EpCAM recombinant eukaryotic plasmid was identified by restriction enzyme digestion .The results of immunofluorescence , Western Blotting ,and flow cytometry consistently indicated that EpCAM protein were successfully expressed in HepG2 cells .Con‐clusion Human EpCAM eukaryotic vector is constructed and EpCAM protein could be expressed well in HepG2 cells ,which laid a foundation for further research on the function ofhepatocarcinoma cells highly expressing EpCAM .

Immunogenicity of a vaccine of S fragments from a new type reovirus generates humoral and cellular immune responses in mice / 中国实验动物学报

Objective To explore the humoral and cellular immune responses of a vaccine of S fragments from a new type reovirus R4 strain in mice.Methods Four recombinant plasmids were constructed by respectively cloning S 1, S2, S3,S4 genes into pcDNA3.1+, and mice were intramuscularly immunized with the recombinant plasmids in a dose of 100 μg/mouse.Control vector pcDNA3.1 +and phosphate buffered saline (PBS) were used as negative controls.The spe-cific antibody level and IgG subclass (IgG1, IgG2a, and IgG2b) were detected by ELISA, and cellular immune responses to R4 were assessed using an interferon ( IFN)-γELISpot assay .Results All recombinant plasmids induced significantly higher levels of anti-R4 IgG compared with that of the controls (pcDNA3.1 +and PBS), and the titers were highest in the mice immunized with S1 and S3.On the other hand, S1 gene induced highest IgG2a antibody and the cellular immune re-sponse was best .Conclusions After the mice immunized with S 1 gene recombinant plasmid , this plasmid can initiate both cellular and humoral immune responses in mice .S1 gene recombinant plasmid is a promising vaccine candidate .