Production optimization of rotavirus-like particles: a system biology approach

Dissertation presented to obtain a Ph.D. degree in Engineering and Technology Sciences, Systems Biology at the Instituto de Tecnologia Química e Biológica, Universidade Nova de LisboaRotavirus-like particles (RLPs), a vaccine candidate against rotavirus disease, were produced by infecting Spodoptera frugiperda Sf-9 cells with genetically engineered recombinant baculoviruses. RLPs are spherically shaped particles composed by three viral proteins (vp) of rotavirus, vp2, vp6 and vp7, arranged in a triple layered structure. A diversity of protein structures, other than the correctly assembled RLP, are observed at the end of a typical production run suggesting that the protein assembly process is rather inefficient. Contaminants such as trimers of vp6 and vp7, vp6 tube-like structures, single-layered vp2 particles, double layered particles of vp2 and vp6 or RLPs lacking one or more subunits represent almost 88% of the total mass of proteins expressed. Thus, optimal control of protein expression concomitant with efficient particle assembly are critical factors for economical RLP production in the baculovirus/insect cells system