Influenza virus is a family of RNA viruses, individual virus contains eight RNAs which encodes for 11 proteins including hemagglutinin (HA), neuraminidase (NA). HA is known to mediate virus entry into the cells and is the major antigen to stimulate antibodies against it. HA is produced by the cell as a monomer; however it must be assembled as a trimmer on the surface of the virus to be functional. Antisera which can recognize the steric trimeric structure are thus crucial for serotype detection. Previously, we have successfully expressed HA protein from flu (USP 7,527,967 patent, 2009) and spike protein from coronavirus (Chang et al., 2004) onto the surface of baculovirus as functional trimeric HA and as a pseudotyped virus. The HA-displaying baculovirus (HA-Bac) can serve as a pseudotyped flu virus for antiserum production, the sera neutralization tests and vaccine potency assay. Purified HA1 was known to be useful for human vaccination, however, the purified HA lacks proper steric conformation, and cannot properly recognize its receptor, also, lost the recognition of neutralizing antibodies. HA-Bac, which displays trimeric HAs, can be purified easier together with the virus particle as convenient antigen for animal vaccination. These baculovirus-based pseudotyped viruses can also be used as a useful tool for the safe study of influenza viruses.
We have identified baculovirus IE2 as a strong activator to stimulate CMV promoter expression in mammalian cells (Fig. 2, 3). The mechanism by which IE2 activates CMV promoter expression in mammalian cells was further studied. We found that IE2 can form a unique clathrate cage-like structure, which encloses G-actin and further recruits activated RNA polymerase II. This clathrate cage-like apparatus (CCLA) can serve as a very strong micro-machine to generate large amounts of mRNA for gene expression (Fig. 2). Since the CCLA is a unique machinery for gene expression visible at the light microscopic level, the mechanism by which IE2 and G-actin work in concert with RNA polymerase II could be a notable emerging subject in the molecular biological studies. Also, since IE2 can strongly enhance baculovirus-mediated gene expression in the mammalian cells (Fig. 3), these studies also make baculovirus as a useful tool for gene delivery in the mammalian cells.
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