HyNPV Protein Expression Approach

As the principal BEVS viruses, AcMNPV and BmNPV each have its advantages as well as limitations. AcMNPV is easily cultured and infectious to a wide range of insects, thus suitable for large-scale cell suspension culture expression. Nevertheless, AcMNPV is not ideal for industrial production due to cell size. By contrast, BmNPV can only infect silkworm but silkworms’ superiority on size and price makes BmNPV suitable for industrial expression.

To utilize the advantage of both AcMNPV and BmNPV viruses, Creative BioMart provides a so called “HyNPV expression system”. Hybrid nuclear polyhedrosis virus (HyNPV) is the artificial hybrid virus of AcMNPV and BmNPV. In the HyNPV expression system, the protein expression is based on the HyNPV rather than AcMNPV or BmNPV. The hybrid virus can infect the hosts of both AcMNPV and BmNPV.

Technology Description

The host size of AcMNPV is generally small, which is not conducive to large-scale protein expression, but it is easy to obtain high titer baculovirus. By contrast, BmNPV is suitable for industrial protein production, but the host is single, and it is difficult to obtain high titer virus. HyNPV integrates the advantages of the two systems and avoids the disadvantages to some extent. The hybrid virus can replicate in both AcMNPV and BmNPV hosts.

The DNA helicase is not only an important enzyme which facilities the DNA replication, but also plays a very important role in deciding the baculovirus host range. The helicase gene of AcMNPV and BmNPV are located in different zone of ORF 95.

When constructing the HyNPV backbone, an AcMNPV helicase gene is added in to the ORF 95 of BmNPV backbone. Those changes of nucleotides and amino acids resulted in a host range expanded baculovirus expression system.

The working logic of the HyNPV follows the principle of Bac to Bac. In order to achieve efficient production of target protein, we suggest harvesting high titer recombinant HyNPV virus from the host insect cells of AcMNPV, and then these recombinant viruses can be used to infect silkworm or silkworm cells.

Features of HyNPV Expression System

Compared to the parental expression systems that are extensively used, the HyNPV has the following advantages:

• Expanded host range. The HyNPV is shown to be infectious to not only silkworm larvae, but also common cell lines (like Sf21, Sf9 and Tn-5).
• Rapid recombinant protein production. That harvesting high titer virus from suspension cell culture system and then infect silkworm is more rapid than using any of the parental system individually.
• Suitable for industrial production. The hybrid system has a higher production efficiency than the parental expression systems by 50%—60%.
• The HyNPV expression system will work more efficiently and enhance the stability of foreign expressed proteins making the hybrid system especially suitable for those proteins that are cysteine proteinase sensitive.