Establishment of RIG-I knockout 293T cell line and its effect on the replication of influenza B virus / 生物工程学报

The CRISPR/Cas9 gene editing technology directs Cas9 protein to recognize, bind and cleave the target site specifically by using artificial single-guide RNA (sgRNA), through non-homologous end joining or homologous end-recombinant repair mechanisms of cells, which can be engineered to knockout or knock-in of genomes. RIG-I is a pattern recognition receptor that recognizes the 5'-triphosphate-containing RNA in the cytoplasm and activates IRF3/7 and NF-κB by interacting with the downstream signaling molecule MAVS, thus initiating the expression of type I interferons and inflammatory factors. Previous studies found that influenza B virus (IBV) can up-regulate the expression of RIG-I. In the present study, to explore whether RIG-I is the major receptor for IBV to active the antiviral innate immune response and its effect on IBV replication, RIG-I gene in 293T cells was knocked out by CRISPR-Cas9 system, and a stable RIG-I knockout 293T (RIG-I(-/-) 293T) cell line was screened by puromycin pressure. The results of Western blotting showed that RIG-I was not expressed in this cell line after IBV or Sendai virus (SeV) infection, indicating that the RIG-I(-/-) 293T cell line was successfully constructed. The transcription levels of interferons, inflammatory factors and interferon-stimulated genes in RIG-I(-/-) 293T cells which were infected by IBV decreased significantly compared with those in wild-type 293T cells. Moreover, the phosphorylation of p65 and IRF3 were not detected in IBV or SeV infected RIG-I(-/-) 293T cells. It is indicated that the expression of cytokines mainly depends on the RIG-I-mediated signaling pathway at the early stage of IBV infection. Furthermore, the multi-step growth curves of IBV in the wild type and RIG-I(-/-) 293T cells showed that RIG-I inhibited the replication of IBV. Collectively, the RIG-I knockout 293T cell line was successfully constructed. We found that RIG-I is the main receptor for IBV to active the antiviral innate immune response and is critical for inhibiting IBV replication, which lays the foundation for further study of IBV infection mechanism.

Establishment of a high sensitive indirect ELISA for detecting specific antibodies against H9 subtype avian influenza virus / 生物工程学报

H9 subtype avian influenza virus causes worldwide epidemic, resulting in enormous economic losses of poultry production. In the present study, an indirect ELISA method was established for more accurate and specific detection. The recombinant protein of the globular head domain of HA of H9 subtype avian influenza virus was used as antigen. Specific blocking buffers and dilution buffers were determined to increase the sensitivity and specificity. The sensitivity of ELISA was higher than that of hemagglutination inhibition (HI) test. The coating antigen is very specific and no cross-reactivity with positive serum against H3N2, H5N2 and H7N9 subtype influenza viruses, Newcastle disease virus, avian infectious bronchitis virus, avian infectious disease virus, and egg drop syndrome virus. Two hundred of clinical sera samples were examined. The results indicate the coincidence rate between ELISA and HI test reached 97%. In addition, there was a positive correlation between OD450 values and the logarithm of HI titer to the base 2 of an individual serum sample (R2=0.981 1).

Phage display technology and tumor targeted therapy / 肿瘤研究与临床

Phage display technology is a kind of laboratory technique by means of genetic engineering to combine phage with exogenous genes, based on the presentation of a heterogeneous peptide or protein libraries on the surface of phage along with phage coat protein expressions. The displayed proteins or peptides could maintain their own relative spatial structure and biological activity, allowing them to direct phage binding to a target of interest. Therefore, the technology can be widely used as a simple and effective screening tool to screen successfully tumor-targeted peptides, deliver tumor-targeted drugs and prepare tumor antibody, which plays an important role in tumor-targeted therapy.

Inhibition of replication and transcription of WSN influenza A virus by IFIT family genes / 生物工程学报

IFIT family genes are a kind of interferon stimulated genes (ISGs), and play important roles in antiviral sector and immunity regulation. To study the regulatory effect of IFIT family genes during influenza A virus (IAV) infection, we used RNA-sequencing analysis (RNA-Seq) technique and found that when 293T cells were infected by A/WSN/33 (WSN), the concentration of IFIT family genes were increased. Further study reveals that overexpression of IFIT2 or IFIT3 could inhibit IAV replication and transcription, and cause the dose-dependent inhibition of polymerase activity of vRNP. In addition, IFIT2 and IFIT3 encoding protein could colocalize with NS1 in 293T cells infected by WSN, indicating that they might interact with each other. The results suggest that IFIT family genes can inhibit the replication and transcription of IAV, which contributes to our understanding of the regulatory effect of host factors during influenza virus infection.