Global Mutational Sweep of SARS-CoV-2: from Chaos to Order

Analysis of large-scale genome sequences demonstrates the mutation of SARS-CoV-2 has been undergoing significant sweeps. Driven by emerging variants, global sweeps are accelerated and purified over time. This may prolong the pandemic with repeating epidemics, presenting challenges to the control and prevention of SARS-CoV-2.

Interactions of highly pathogenic avian influenza H5N1 nucleoprotein with NF-κB-inducing kinase(NIK) / 军事医学

Objective To study the interactions between the highly pathogenic avian influenza H5N1 nucleoprotein (H5N1 NP) and NF-κB-inducing kinase (NIK),and to reveal the effect of H5N1 NP on NIK-induced NF-κB transcriptional activity.Methods The gene encoding NIK protein was amplified by RT-PCR from total RNA of HeLa cell line.Eukaryotic expression plasmid pCMV-Myc-NIK and prokaryotic expression plasmid pGEX-4T-1-NP (GST-NP) were constructed by cloning from HeLa cell cDNA and pcDNA3-Flag-NP vector,respectively.Co-immunoprecipitation (co-IP) and GST pull-down were used to test the interactions between H5N1 NP and NIK.Dual-luciferase reporter gene analysis system was used to test the effect of H5N1 NP on NIK-induced NF-κB transcriptional activity.Results Co-IP and GST pull-down showed that pCMV-Myc-NIK and pGEX-4T-1-NP (GST-NP) could express Myc tagged NIK protein and GST tagged NP protein in HEK293T cells and E.coli,respectively,and that H5N1 NP was associated with NIK in vivo and in vitro.Dual-luciferase reporter gene analysis suggested that H5N1 could inhibit NIK-induced NF-κB transcriptional activity.Conclusion H5N1 NP interacts with NIK and inhibits NIK-induced NF-κB transcriptional activity.This finding can facilitate further study of H5N1.

Construction and preliminary study of biological functions of O157∶H7 typeⅢsecre-tion system effector NleF gene knockout mutant / 军事医学

Objective To construct Escherichia coli O157∶H7 T3SS effector NleF gene knockout mutant and its com-plementary strain, and probe its effects on bacterial growth and cell death .Methods T3SS Effector NleF gene knockout mutant ΔnleF was constructed with λ-Red homologous recombination .Complementary strain ΔnleF/NleF was constructed by transferring pET-24a(+)-NleF into ΔnleF competent cells.Wild type,ΔnleF and ΔnleF/NleF were cultured in LB and DMEM(10%FBS) respectively,D600 was measured every hour , and the growth curve was drawn .HeLa cells were infected with three kinds of strains , the supernatant of LDH release was detected with cytotoxicity detection kit ,and the cytotoxicity was calculated .Results ΔnleF and ΔnleF/NleF were constructed .The growth rates of wild type , ΔnleF and ΔnleF/NleF was not significantly different .Wild type O157 infection induced cell death .Cytotoxicity was increased as much in ΔnleF in-fected cells as in ΔnleF/NleF infected cells.Conclusion EHEC O157∶H7 T3SS Effector NleF has no significant effect on bacterial growth ,but might inhibit host cell death caused by bacterial infection .

Prokaryotic expression, purification, identification, and polyclonal antibody prepa-ration of enterohemorrhagic Escherichia coli effector NleB1 / 军事医学

Objective To construct a prokaryotic plasmid expressing the recombinant protein of enterohemorrhagic Escherichia coli(EHEC) effector NleB1 and to prepare the polyclonal antibody of mouse anti-NleB1.Methods The nleB1 (990 bp) gene was amplified from the genome EHEC O157∶H7 and cloned into the expression plasmid pET24a to construct the recombinant plasmid pET24a-nleB1 that was transformed into E.coli BL21(DE3).After induction with isopropylthio-gelactoside( IPTG) , the His-tag fusion proteins were purified by Ni+affinity chromatography and gel slices.The polyclonal antibody was prepared by immunizing BALB/c mice with purified recombinant proteins and analyzed by Western blotting and ELISA.Results The pET24a-nleB1 recombinant plasmid was successfully constructed, the fusion protein was ex-pressed and purified,and the polyclonal antibody was obtained by immunizing mice with purified fusion protein.Western blotting and ELISA staining demonstrated that the polyclonal antibody was successfully obtained.Conclusion The prepara-tion of the polyclonal antibody against EHEC O157∶H7 NleB1 will be of help for further studies on the function of NleB1 protein.