Purification Process for a Secreted Protein Produced in Insect Cells.

The Baculovirus Expression Vector System (BEVS) is used with cultured insect cells to produce a wide variety of heterologous proteins, which can be secreted into the culture medium during the transient infection process (Smith et al. Mol Cell Biol 12:2156-2165, 1983). When the infection process is complete, centrifugation is often used to separate the desired protein from the spent insect cells. The desired product in the harvested supernatant is contaminated with baculovirus, amino acids, lipids, detergents, oils, lysed cells from the infection process, genomic DNA from the insect cells, and proteases due to the lytic nature of the baculovirus infection process and many other contaminants (Ikonomou et al. Appl Microbiol Biotechnol 62:1-20, 2003). All these contaminants that are present in the centrifuged supernatant with the desired secreted protein make the initial chromatographic capture step critical for effective purification of the desired protein. A purification scheme will be outlined for a slightly acidic secreted protein using cation exchange chromatography (Lundanes et al. Chromatography: basic principles, sample preparations and related methods, 1st edn. Wiley, 2013).

A recombinant West Nile virus envelope protein vaccine candidate produced in Spodoptera frugiperda expresSF+ cells.

In this study, a recombinant truncated West Nile virus envelope protein antigen (rWNV-E) was produced in serum-free cultures of the expresSF+ insect cell line via baculovirus infection. This production system was selected based on its use in the production of candidate human and animal vaccine antigens. A defined fermentation and purification process for the rWNV-E antigen was established to control for purity and immunogenicity of each protein batch. The material formulated with aluminum hydroxide was stable for greater than 8months at 4 degrees C. The recombinant vaccine candidate was evaluated for immunogenicity and protective efficacy in several animal models. In mouse and hamster WNV challenge models, the vaccine candidate induced viral protection that correlated with anti-rWNV-E immunogenicity and WNV neutralizing antibody titers. The rWNV-E vaccine candidate was used to boost horses previously immunized with the Fort Dodge inactivated WNV vaccine and also to induce WNV neutralizing titers in naïve foals that were at least 14weeks of age. Furthermore, the vaccine candidate was found safe when high doses were injected into rats, with no detectable treatment-related clinical adverse effects. These observations demonstrate that baculovirus-produced rWNV-E can be formulated with aluminum hydroxide to produce a stable and safe vaccine which induces humoral immunity that can protect against WNV infection.