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From 2012.igem.org

Production of VLPs

To produce VLPs in vitro we need a protocol. A protocol was given to us by Richard Kormelink and was for the production of the wild type CCMV in vitro. This protocol was built around the lab of Richard Kormelink and some of the apparatus and techniques weren’t available to us. After modifying the protocol we were able to produce large quantities of wild type CCMV VLPs in our own lab. But we wanted more, we would like to have a standard protocol in which we can produce any VLP in vitro from any virus, without changing the protocol drastically. After looking at our already modified protocol we saw that it already was a standardized protocol, we tested with other VLPs from viruses and it worked.

The production protocol has seven major steps. The first step is to grow the cells in which the gene for the VLP-protein contains. The second step is after a few hours to induce the culture with an agent to produce our proteins. In front of our gene we put the .... brick, this brick contains the LacI-promoter and a RBS. So we induced our cells with IPTG. 4 hours after induction we centrifuge our cells and wash them with MQ-water, so that we can store them overnight at minus 20 degree Celsius. After storage overnight we dissolve our cells in disassembly buffer and lyse the cells to get our protein into the medium. We lysed our cells with a French press, which works with high pressure to disrupt the cells. After lysation we centrifuge the disrupted cells again to pellet the cell debris in which our proteins contain. After centrifugation we resuspend the pellet with disassembly buffer that contains 8M urea, This done to denature the proteins so that we can fold it correctly in vitro and form it into VLPs. After treatment with urea we dialyse the solution with our proteins, first we dialyse with dialysis buffer to get the urea out this takes 6 times 4 hours to reduce the urea concentration. When the urea concentration is low enough the unfolded proteins will slowly fold into the correct state. The second dialysis step is with reassembly buffer, this takes 2 times 4 hours. We reduce the pH so that the subunits will fold together into a VLP.

This production process is able to produce large quantities of VLPs in vitro. We succeeded in to form VLPs of the CCMV wild type, variations of the CCMV wild type and HepB wild type. We are close to produce another type of virus and multiple variations of CCMV and HepB.