Baculovirus expression systems for production of recombinant proteins in insect and mammalian cells

Baculovirus vector systems are extensively used for the expression of foreign gene products in insect and mammalian cells. New advances increase the possibilities and applications of the baculovirus expression system, which makes it possible to express multiple genes simultaneously within a single infected insect cell and to obtain multimeric proteins functionally similar to their natural analogs. Recombinant viruses with expression cassettes active in mammalian cells are used to deliver and express genes in mammalian cells in vitro and in vivo. Further improvement of the baculovirus expression system and its adaptation to specific target cells can open up a wide variety of applications. The review considers recent achievements in the use of modified baculoviruses to express recombinant proteins in eukaryotic cells, advantages and drawbacks of the baculovirus expression system, and ways to optimize the expression of recombinant proteins in both insect and mammalian cell lines.

Horseradish peroxidase-labelled probes and enhanced chemiluminescence to detect baculoviruses in gypsy moth and eastern spruce budworm larvae

Horseradish peroxidase-labelled whole genomic DNA probes and enhanced chemiluminescence procedures were utilized to detect baculovirus in insect macerates blotted on nylon membranes. Detection levels were similar to those found using 32P-labelled probes; 5 x 10(3) occlusion bodies (OBs), 2 x 10(3) OBs and 4 x 10(4) OBs of Lymantria dispar (L.) nuclear polyhedrosis virus (LdNPV), Choristoneura fumiferana (Clem.) NPV (CfNPV) and C. fumiferana granulosis virus (CfGV) respectively using 10 ng/ml LdNPV DNA probe and 20 ng/ml CfNPV and CfGV probe concentrations. Quantities of purified viral DNA detected were 0.56 ng LdNPV, 0.20 ng CfNPV and 0.10 ng CfGV at similar probe concentrations. Cross reactions were observed between LdNPV DNA probes and CfNPV. Multiple probing of membranes blotted with insect macerates was capable of diagnosing the presence of NPV and GV on membranes. This procedure appears to be useful in the diagnosis of large numbers of insects for several baculoviruses.

The structural and functional organization of the Autographa californica nuclear polyhedrosis virus genome

Baculoviruses are used as biological control agents of insect pests in agriculture and forestry. The multiple-nucleocapsid nuclear polyhedrosis virus of Autographa californica (AcMNPV) is the prototype baculovirus. Recently, this virus has become widely used as vector for the high-level expression of foreign genes in insect cells. An updated physical map of restriction sites as well as the location of open reading frames (ORFs) and transcripts are presented. Most characteristic is the dispersal of "early", "late", and "very late" genes over the genome and the presence of nested sets of 3' and 5' coterminal transcripts.

An insertion of insect cell DNA in the 81-map-unit segment of Autographa californica nuclear polyhedrosis virus DNA

In this report, a transposonlike insertion of Spodoptera frugiperda insect cell DNA was analyzed in single-plaque isolate E of the insect baculovirus Autographa californica nuclear polyhedrosis virus (AcNPV). The 634-base-pair insertion is characterized by an 18-base-pair terminal inverted repeat and carries an EcoRI site. This additional EcoRI site in the 81-map-unit segment of the DNA of plaque isolate E of AcNPV explains the difference between the EcoRI restriction map of the DNA from this isolate and those of the virus stocks used in other laboratories. Except for this insertion, the nucleotide sequence at the site of insertion in the DNA of plaque isolate E is identical to that of AcNPV E2 (G. E. Smith and M. D. Summers, Virology 89:517-527, 1978). The cellular DNA insertion in the AcNPV genome is represented many times in the S. frugiperda cell genome but has no detectable homology with DNAs from species other than lepidopteran insects. In S. frugiperda cells, the transposonlike insertion sequences are transcribed into cytoplasmic RNA. The transcription of these sequences is initiated within the cellular insertion element. As reported previously (C. Oellig, B. Happ, T. Müller, and W. Doerfler, J. Virol. 61:3048-3057, 1987), in S. frugiperda cells infected with plaque isolate E of AcNPV, at least nine different size classes of AcNPV-specific RNAs are synthesized; in AcNPV E2-infected cells, similar size classes have been detected. The cellular insertion of plaque isolate E provides the initiation site for the synthesis of an additional RNA size class which is transcribed off viral DNA.

A physical map of Spodoptera littoralis B-type nuclear polyhedrosis virus genome

A physical map for the genome of Spodoptera littoralis (Egyptian cottonworm) nuclear polyhedrosis virus of B-type (S1MNPV-B) [Cherry CL, Summers MD (1985) J Invertebr Pathol 46: 289-295] was prepared using the restriction endonucleases SmaI, SfiI, NotI, ApaI, KpnI, BstEII, PstI, SacI, and HindIII. The size of the genome was estimated to 136 kbp for the Morocco isolate (S1MNPV-M2) and to 135 kbp for the Lyon isolate (S1MNPV-L4). HindIII-K was used as the zero-point of the map because it hybridized to EcoRI-I and BamHI-F fragment of Autographa californica (AcMNPV) DNA, and the direction of transcription of the S1MNPV polyhedrin gene was chosen left to right. Hybridization of six AcMNPV cloned DNA fragments with S1MNPV-B genome shows that S1MNPV-B and AcMNPV genomic structures are not aligned.

Comparison of the p26 gene region of two baculoviruses

A 1.1-kb region of DNA containing the p26 gene of the multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata (OpMNPV) was sequenced, transcriptionally mapped, and compared to the same region in the MNPV of Autographa californica (AcMNPV). The mRNA start site of the p26 gene occurs about 22 nucleotides downstream from an A/T-rich putative promoter sequence that is highly conserved between AcMNPV and OpMNPV. The p26 mRNA is transcribed through the p26 gene and coterminates with the p10 gene resulting in a mRNA containing copies of both genes. The reading frames of the OpMNPV and AcMNPV p26 genes showed 47% amino acid sequence homology which is clustered in six regions with over 65% amino acid homology. There was a distinct bias toward incorporation of G/C-rich codons in the OpMNPV p26 gene. No DNA homology was observed between the region upstream of the p26 gene in AcMNPV and OpMNPV. In AcMNPV, this region contains the homologous repeated (hr) sequence hr5. Hybridization of a plasmid containing an AcMNPV-repeated sequence (hr5) to Southern blots of the OpMNPV genome indicated that this repeated sequence is lacking in OpMNPV.

DNA homologies between the genomes of Choristoneura fumiferana and Autographa californica nuclear polyhedrosis viruses

The DNA sequence homology between the genomes of Choristoneura fumiferana and Autographa californica multicapsid nuclear polyhedrosis viruses (CfMNPV and AcMNPV) were compared by hybridization of nick-translated [32P]CfMNP[V DNA to restricted AcMNPV genome. In the presence of 5 x SSC and 50% formamide the CfMNPV DNA exhibited extensive homology to the AcMNPV genome. When the stringency conditions of hybridization were lowered, we observed hybridization to almost all the EcoRI fragments of AcMNPV. We then utilized the cloned EcoRI fragments from both genomes to obtain more detailed information, and to localize the hybridizing fragments on the EcoRI physical map of AcMNPV. It was clear that some CfMNPV clones hybridized to more than one fragment of the AcMNPV genome indicating that there has been some DNA sequence rearrangement in the AcMNPV genome.

Conservation of genome organization in two multicapsid nuclear polyhedrosis viruses

The genome of the multicapsid nuclear polyhedrosis virus of Orgyia pseudotsugata was mapped by examining overlapping HindIII fragments from cosmid clones which had been constructed from partial HindIII digests of viral DNA. Five OpMNPV cosmid clones containing fragments encompassing the entire OpMNPV genome were hydridized to blots of DNA from the multicapsid nuclear polyhedrosis virus of Autographa californica. The hybridization pattern indicated that the genomes of these viruses are similarly organized.