Baculovirus expression cassette vectors for rapid production of complete human IgG from phage display selected antibody fragments

For the expression of human intact IgG antibodies, we have constructed a se t of baculovirus expression vectors designed to facilitate rapid insertion of heavy and light chain genes of Fab or scFv antibodies derived from phage display antibody libraries. By linking them to human constant or Fc region s, expression of complete human immunoglobulin molecules was achieved in in sect cells by infection with recombinant baculovirus. The IgG expression ca ssette vectors are based on the backbone vector which contains two back to back polyhedron and p10 promoters. The IgG expression cassette elements, in cluding the authentic IgG lambda or kappa and heavy chain signal sequences, as well as light chain (lambda or kappa) and heavy chain constant region g enes are combined in a single vector and are controlled by the p10 and poly hedron promoter respectively. Either of VL or Fab-L and VH or Fab-Fd genes from common phage display systems can be directly inserted into one of the cassette vectors through in-frame cloning sites. This design of a single ca ssette vector combining heavy and light chain expression elements allowed r apid production and secretion of correctly processed and assembled intact i mmunoglobulins from recombinant baculovirus infected insect cells. The reco mbinant antibodies showed the expected molecular size of the H2L2 heterodim er in non reducing SDS-PAGE. No apparent differences were found between the expression level of heavy and light chains, and antigen binding function w as preserved. For various antibodies, yields between 6 and 18 mg/l IgG were obtained. (C) 2001 Elsevier Science B.V. All rights reserved.