Production of recombinant dengue virus‐like particles by COS‐1 cells in a serum‐free defined medium

Abstract

COS‐1 cells transfected with recombinant genes from the four dengue virus serotypes (DENV‐1, ‐2, ‐3 and ‐4) produce and secrete virus‐like particles (VLP). The recombinant DENV envelope and premembrane or membrane proteins are translated and assembled by the transfected cells into VLPs, which are noninfectious because they lack the genomic RNA. The four DENV VLPs are combined and used as antigens to clinically diagnose IgM and IgG antibodies to DENV infection in human serum by enzyme‐linked immunosorbent assays (ELISA). A serum‐free defined medium was developed to replace the fetal bovine serum (FBS) supplemented medium currently used to produce DENV VLP in COS‐1 cells, which was done on a four day harvest cycle. Different supplements in Dulbecco's Modified Eagle Medium (D‐MEM) were evaluated for COS‐1 production of DENV‐1, ‐2, ‐3 and ‐4 VLP by Western blot analysis and ELISA of the culture medium. D‐MEM supplemented with lipid‐rich bovine serum albumin (BSA) supported secretion of the four DENV VLPs for up to eight harvest cycles that was equivalent to FBS supplemented medium. Neither D‐MEM alone nor supplementation with fatty acid‐free BSA supported VLP secretion. This serum‐free defined medium will reduce cost of production, minimize variability between batches due to FBS and to facilitate DENV VLP purification for the ELISA kits. Source of research support: Focus Diagnostics, Inc.