Infectious bronchitis virus nucleocapsid protein suppressed type I interferon production by interfering with the binding of MDA5-dsRNA and interacting with LGP2.

The type I interferon (IFN-I) is a critical component of the innate immune responses, and Coronaviruses (CoVs) from both the Alphacoronavirus and Betacoronavirus genera interfere with the IFN-I signaling pathway in various ways. Of the gammacoronaviruses that mainly infect birds, little is known about how infectious bronchitis virus (IBV), evades or interferes with the innate immune responses in avian hosts since few IBV strains have been adapted to grow in avian passage cells. Previously, we reported that a highly pathogenic IBV strain GD17/04 has adaptability in an avian cell line, providing a material basis for further study on the interaction mechanism. In the present work, we describe the suppression of IBV to IFN-I and the potential role of IBV-encoded nucleocapsid (N) protein. We show that IBV significantly inhibits the poly I: C-induced IFN-I production, accordingly the nuclear translocation of STAT1, and the expression of IFN-stimulated genes (ISGs). A detailed analysis revealed that N protein, acting as an IFN-I antagonist, significantly impedes the activation of the IFN-ß promoter stimulated by MDA5 and LGP2 but does not counteract its activation by MAVS, TBK1, and IRF7. Further results showed that IBV N protein, verified to be an RNA-binding protein, interferes with MDA5 recognizing double-stranded RNA (dsRNA). Moreover, we found that the N protein targets LGP2, which is required in the chicken IFN-I signaling pathway. Taken together, this study provides a comprehensive analysis of the mechanism by which IBV evades avian innate immune responses.

Innenrücktitelbild: Aptamer Blocking Strategy Inhibits SARS‐CoV‐2 Virus Infection

Eine Aptamer‐Blockierungsstrategie zur Hemmung der SARS‐CoV‐2‐Infektion wird von Honglin Chen, Yanling Song, Chaoyong Yang et al. im Forschungsartikel auf S. 10354 demonstriert. Eine Aptamer‐Sonde wurde so konstruiert, dass sie an das Spike‐Protein von SARS‐CoV‐2 bindet, was die Infektion des Virus hemmt, indem es die Interaktion des Virus mit ACE2‐Rezeptoren auf der Zellmembran blockiert.

Aptamer Blocking Strategy Inhibits SARS‐CoV‐2 Virus Infection

The COVID‐19 pandemic caused by SARS‐CoV‐2 is threating global health. Inhibiting interaction of the receptor‐binding domain of SARS‐CoV‐2 S protein (SRBD) and human ACE2 receptor is a promising treatment strategy. However, SARS‐CoV‐2 neutralizing antibodies are compromised by their risk of antibody‐dependent enhancement (ADE) and unfavorably large size for intranasal delivery. To avoid these limitations, we demonstrated an aptamer blocking strategy by engineering aptamers’ binding to the region on SRBD that directly mediates ACE2 receptor engagement, leading to block SARS‐CoV‐2 infection. With aptamer selection against SRBD and molecular docking, aptamer CoV2‐6 was identified and applied to prevent, compete with, and substitute ACE2 from binding to SRBD. CoV2‐6 was further shortened and engineered as a circular bivalent aptamer CoV2‐6C3 (cb‐CoV2‐6C3) to improve the stability, affinity, and inhibition efficacy. cb‐CoV2‐6C3 is stable in serum for more than 12 h and can be stored at room temperature for more than 14 days. Furthermore, cb‐CoV2‐6C3 binds to SRBD with high affinity (Kd=0.13 nM) and blocks authentic SARS‐CoV‐2 virus with an IC50 of 0.42 nM.

Aptamer Blocking Strategy Inhibits SARS-CoV-2 Virus Infection

Eine Aptamer-Blockierungsstrategie zur Hemmung der SARS-CoV-2-Infektion wird von Honglin Chen, Yanling Song, Chaoyong Yang et?al. in ihrem Forschungsartikel demonstriert (DOI: 10.1002/ange.202100225). Eine Aptamer-Sonde wurde so konstruiert, dass sie an das Spike-Protein von SARS-CoV-2 bindet, was die Infektion des Virus hemmt, indem es die Interaktion des Virus mit ACE2-Rezeptoren auf der Zellmembran blockiert.

Aptamer Blocking Strategy Inhibits SARS-CoV-2 Virus Infection.

The COVID-19 pandemic caused by SARS-CoV-2 is threating global health. Inhibiting interaction of the receptor-binding domain of SARS-CoV-2 S protein (SRBD ) and human ACE2 receptor is a promising treatment strategy. However, SARS-CoV-2 neutralizing antibodies are compromised by their risk of antibody-dependent enhancement (ADE) and unfavorably large size for intranasal delivery. To avoid these limitations, we demonstrated an aptamer blocking strategy by engineering aptamers' binding to the region on SRBD that directly mediates ACE2 receptor engagement, leading to block SARS-CoV-2 infection. With aptamer selection against SRBD and molecular docking, aptamer CoV2-6 was identified and applied to prevent, compete with, and substitute ACE2 from binding to SRBD . CoV2-6 was further shortened and engineered as a circular bivalent aptamer CoV2-6C3 (cb-CoV2-6C3) to improve the stability, affinity, and inhibition efficacy. cb-CoV2-6C3 is stable in serum for more than 12 h and can be stored at room temperature for more than 14 days. Furthermore, cb-CoV2-6C3 binds to SRBD with high affinity (Kd =0.13 nM) and blocks authentic SARS-CoV-2 virus with an IC50 of 0.42 nM.

A novel low virulent respiratory infectious bronchitis virus originating from the recombination of QX, TW and 4/91 genotype strains in China.

In China, variants of infectious bronchitis virus (IBV) evolve continually and diverse recombinant strains have been reported. Here, an IBV strain, designated as ck/CH/LJX/2017/07 (referred as JX17) was isolated from chicken vaccinated with H120 and 4/91 in Jiangxi, China, in 2017. Sequence analysis reveals of the S1 gene of JX17 the highest nucleotide identity of 98.15% with that of GI-7 genotype TW2575/98 strain. Furthermore, whole genome analysis among JX17 and other 18 IBV strains demonstrates that JX17 has the highest nucleotide identity of 95.94% with GI-19 genotype YX10 strain. Among all genes of JX17 except the S1 gene, the N gene and 3' UTR have the highest identity to GI-13 genotype 4/91 strain and the rest genes are the most identical to GI-19 genotype YX10 strain. Analyzed by the RDP and SimPlot, the recombination of JX17 strain was shown to occur in regions which include 5'-terminal S1 gene (20,344 to 22,447 nt), most N gene and 3' UTR (26,163 to 27,648 nt). The pathogenicity study shows that JX17 is a natural low virulent IBV variant which caused respiratory symptoms but no death. Taken together, these results indicate that IBV strains continue to evolve through genetic recombination and three prevalent genotypes in China including QX, TW and 4/91 have started to recombine.

Discovery of Aptamers Targeting the Receptor-Binding Domain of the SARS-CoV-2 Spike Glycoprotein.

The World Health Organization has declared the outbreak of a novel coronavirus (SARS-CoV-2 or 2019-nCoV) as a global pandemic. However, the mechanisms behind the coronavirus infection are not yet fully understood, nor are there any targeted treatments or vaccines. In this study, we identified high-binding-affinity aptamers targeting SARS-CoV-2 RBD, using an ACE2 competition-based aptamer selection strategy and a machine learning screening algorithm. The Kd values of the optimized CoV2-RBD-1C and CoV2-RBD-4C aptamers against RBD were 5.8 nM and 19.9 nM, respectively. Simulated interaction modeling, along with competitive experiments, suggests that two aptamers may have partially identical binding sites at ACE2 on SARS-CoV-2 RBD. These aptamers present an opportunity for generating new probes for recognition of SARS-CoV-2 and could provide assistance in the diagnosis and treatment of SARS-CoV-2 while providing a new tool for in-depth study of the mechanisms behind the coronavirus infection.