The baculovirus expression vector system (BEVS) is an emerging tool for the production of recombinant proteins, vaccines and bio-pesticides. However, a system-level understanding of the complex infection process is important in realizing large-scale production at a lower cost. The entire baculovirus infection process is summarized as a combination of various modules and the existing mathematical models are discussed in light of these modules. This covers a systematic review of the present understanding of virus internalization, viral DNA replication, protein expression, budded virus (BV) and occlusion-derived virus (ODV) formation, few polyhedral (FP) and defective interfering particle (DIP) mutant formation, cell cycle modification and apoptosis during the viral infection process. The corresponding theoretical models are also included. Current knowledge regarding the molecular biology of the baculovirus/insect cell system is integrated with population balance and mass action kinetics models. Furthermore, the key steps for simulating cell and virus densities and their underlying features are discussed. This review may facilitate the further development and refinement of mathematical models, thereby providing the basis for enhanced control and optimization of bioreactor operation.

The baculovirus expression vector system has emerged as the system of choice for the expression of a number of heterologous genes of both prokaryotic and eukaryotic origin. This system utilizes the baculovirus very late, hyperactive polyhedrin and p10 promoters to drive the transcription of foreign genes. Regulation of transcription from these promoters is presently not well understood even though a number of viral gene products that may be important for transcription have been identified. Fresh insight into host-virus interactions during baculovirus pathogenesis is now offered by the identification of insect host factors that interact with transcriptionally essential motifs of these promoters as well as cis-acting enhancer-like elements upstream from the promoter.

The availability of cDNA and genomic clones for the subcomponents of C1, as well as the recognition of the modular organization of serine-proteases have opened up exciting new possibilities for approaching structural problems. In this review the latest achievements of combined protein engineering, functional and structural studies are summarized. The concept of this research is to construct deletion, point and hybrid mutants of the highly homologous C1r and C1s subcomponents, to reveal the functional role of individual modules, map the interaction sites between subcomponents of the C1 complex and refine the structural model of C1. The first prerequisite of such an approach was the expression of the subcomponents in a eukaryotic system, in biologically active form. This was followed by expression of various mutants. Autographa californica nuclear polyhedrosis virus was used as vector to express human C1r and C1s in Spodoptera frugiperda cell culture and in lepidopteran larvae. The yield of expression was high enough to isolate recombinant subcomponents for structural and functional studies. Recombinant viruses containing the A-, B-, and C-chains of C1q were also constructed. The insect cells are able to beta-hydroxylate the Asn residue of the EGF domain in the C1r but with a low efficiency. It is clear now, that this post-translational modification does not play a role in the Ca2+ dependent C1r-C1s interaction. The results with deletion mutants of C1r show that both, domain I, and II are absolutely necessary for the tetramer formation and both have regulatory role in the autoactivation. The C1s alpha R hybrid does not dimerize in presence of Ca2+, however it can form a tetramer with C11(2) that can bind to C1q. This observation indicates that the function of the C1s alpha part in the hybrid is modulated by the C1r part (gamma B) of the molecule. The C1Rs hybrid behaves like C1r, providing haemolytically active C1 with C1q and C1s. This observations shows that the regulatory domains determine the high functional specificity of the serine-protease subcomponents of C1. In order to control the autoactivation process point mutant cDNAs were constructed by altering the Arg-Ile bond in the catalytic domain of the C1r. The Gln-Ile construction is a stable zymogen while the Arg-Phe mutant has a lower rate of autoactivation.