Role of key amino acids in the transmembrane domain of the Newcastle disease virus fusion protein

Development of a novel cholesterol tag-based system for trans-membrane transport of protein drugs

The main technological difficulties of developing an intracellular (transmembrane) transport system for protein drugs lie in two points: i) overcoming the barriers in the cellular membrane, and ii) loading enough protein drugs, and particularly high-dose proteins, into particles. To address these two technological problems, we recently developed a novel cholesterol tag (C-Tag)-based transmembrane transport system. This pilot study found that the C-Tag dramatically improved the cellular uptake of Fab (902-fold, vs. Fab alone) into living cells, indicating that it successfully achieved transmembrane transport. Moreover, C-Tag-mediated membrane transport was verified using micron-scale large unilamellar vesicles (LUVs, approximately 1.5 μm)-based particles. The C-Tagged Fab was able to permeate the liposomal bilayer and it greatly enhanced (a 10.1-fold increase vs. Fab alone) internalization of proteins into the LUV-based particles, indicating that the C-Tag loaded enough proteins into particles for use of high-dose proteins. Accordingly, we established a novel C-Tag-based transport system that has overcome the known technological difficulties of protein transmembrane delivery, and this might be a useful technology for drug development in the future.

Establishment of reverse genetics for genotype VII Newcastle disease virus and altering the cell tropism by inserting TMPRSS2 into the viral genome

Newcastle disease (ND) is the most important infectious disease in poultry, which is caused by avian orthoavulavirus type 1 (AOAV-1), previously known as Newcastle disease virus (NDV). In this study, an NDV strain SD19 (GenBank accession number OP797800) was isolated, and phylogenetic analysis suggested the virus belongs to the class II genotype VII. After generating wild-type rescued SD19 (rSD19), the attenuating strain (raSD19) was generated by mutating the F protein cleavage site. To explore the potential role of the transmembrane protease, serine S1 member 2 (TMPRSS2), the TMPRSS2 gene was inserted into the region between the P and M genes of raSD19 to generate raSD19-TMPRSS2. Besides, the coding sequence of the enhanced green fluorescent protein (EGFP) gene was inserted in the same region as a control (rSD19-EGFP and raSD19-EGFP). The Western blot, indirect immunofluorescence assay (IFA), and real-time quantitative PCR were employed to determine the replication activity of these constructs. The results reveal that all the rescued viruses can replicate in chicken embryo fibroblast (DF-1) cells; however, the proliferation of raSD19 and raSD19-EGFP needs additional trypsin. We next evaluated the virulence of these constructs, and our results reveal that the SD19, rSD19, and rSD19-EGFP are velogenic; the raSD19 and raSD19-EGFP are lentogenic; and the raSD19-TMPRSS2 are mesogenic. Moreover, due to the enzymatic hydrolysis of serine protease, the raSD19-TMPRSS2 can support itself to proliferate in the DF-1 cells without adding exogenous trypsin. These results may provide a new method for the NDV cell culture and contribute to ND's vaccine development.