Lepidopteran cells, an alternative for the production of recombinant antibodies?

Abstract

Monoclonal antibodies are used with great success in many different therapeutic domains. In order to satisfy the growing demand and to lower the production cost of these molecules, many alternative systems have been explored. Among them, the baculovirus/insect cells system is a good candidate. This system is very safe, given that the baculoviruses have a highly restricted host range and they are not pathogenic to vertebrates or plants. But the major asset is the speed with which it is possible to obtain very stable recombinant viruses capable of producing fully active proteins whose glycosylation pattern can be modulated to make it similar to the human one. These features could ultimately make the difference by enabling the production of antibodies with very low costs. However, efforts are still needed, in particular to increase production rates and thus make this system commercially viable for the production of these therapeutic agents.

Figure 1.

Baculovirus replication. During the very late stage of replication, two non-essential genes the polyhedrin (PH) and P10 are transcribed at a very high level. Polyhedrin is responsible for the formation of the polyhedra structure in which the virions are embedded. The involvement of P10 remains unclear, but it is generally assumed that it plays a role in cell lysis. These characteristics are the basis for the development of baculovirus as an expression vector.

Figure 2.

Schematic representation of the different steps involved in the construction of a baculovirus expressing a recombinant antibody. (A) General organization of specific transfer vectors used to express heavy and light chains. In this example, H and L genes are integrated at two different loci (PH and P10). (B) The cDNAs coding for the variable regions (VH and VL) are inserted in frame with the immunoglobulin signal peptide sequence and the human (or murine) heavy or light constant region. Sf9 cells were transfected with a defective non-infectious viral DNA (Bacmid or linearized viral DNA) and two transfer vectors. Infectious double-recombinant viruses generated after homologous recombination (HR) are cloned by plaque assay. (C) Polyacrylamide gel electrophoresis of the antibody purified from the cell culture supernatant of Sf9 cells which were infected with the recombinant virus (Silver staining, lane 1). Control human IgG1 (lane 2).