Transient and stable gene expression in mammalian cells transduced with a recombinant baculovirus vector

Recombinant baculoviruses can serve as gene-transfer vehicles for transient expression of recombinant proteins in a wide range of mammalian cell types. Furthermore, by inclusion of a dominant selectable marker in the viral vector, cell lines can be derived that stably express recombinant genes. A virus was constructed containing two expression cassettes controlled by constitutive mammalian promoters: the cytomegalovirus immediate early promoter/enhancer directing expression of green fluorescent protein and the simian virus 40 (SV40) early promoter controlling neomycin phosphotransferase II. Using this virus, efficient gene delivery and expression was observed and measured in numerous cell types of human, primate, and rodent origin. In addition to commonly used transformed cell lines such as HeLa, CHO, Cos-7, and 293, this list includes primary human keratinocytes and bone marrow fibroblasts. In all cases, addition of butyrate or trichostatin A (a selective histone deacetylase inhibitor) to transduced cells markedly enhanced the levels of reporter protein expression observed. When transduced cells are put under selection with the antibiotic G418, cell lines can be obtained at high frequency that stably maintain the expression cassettes of the vector DNA and exhibit stable, high-level expression of the reporter gene. Stably transduced derivatives have been selected from a substantial number of different cell types, suggesting that stable lines can be derived from any cell type that exhibits transient expression.

The baculoviruses occlusion-derived virus: virion structure and function

Baculoviruses play an important ecological role regulating the size of insect populations. For many years, baculoviruses have been applied as targeted biocontrol agents against forestry and agriculture pests. Baculovirus insecticides are effective against insect pests such as velvetbean caterpillar (Anticarsia gemmatalis ), cotton bollworm (Helicoverpa zea ), and gypsy moth (Lymantria dispar ). Baculoviruses are transmitted to insects by the oral route mediated by the occlusion-derived virus (ODV). The ODV is also specialized to exploit the insect midgut that is one of the most extreme biological environments where the viruses are subject to caustic pH and digestive proteases. The molecular biology of the ODV reveals new frontiers in protein chemistry. Finally, ODVs establishes infection in insect gut tissues that are virtually nonsupportive to virus replication and which are continuously sloughed away. ODVs carry with them a battery of proteins that enable them to rapidly exploit and harness these unstable cells for virus replication.

Efficient transduction of mammalian cells by a recombinant baculovirus having the vesicular stomatitis virus G glycoprotein

Baculovirus vectors recently have been shown to be capable of efficient transduction of human hepatoma cells and primary hepatocytes in culture. This paper describes the generation of a novel recombinant baculovirus (VGZ3) in which the vesicular stomatitis virus glycoprotein G (VSV G) is present in the viral envelope. The gene encoding VSV G was inserted into the baculovirus genome under the control of the polyhedrin promoter such that it was expressed at very high levels in infected insect cells but not in mammalian cells. Expression of the lacZ reporter gene was driven by a promoter that is functional in mammalian cells (the Rous sarcoma virus long terminal repeat). We show by Western analysis that VSV G protein was present in purified baculovirus preparations. A VSV G monoclonal antibody blocked transduction of mammalian cells by VGZ3. This virus was morphologically distinct from baculovirus lacking VSV G, with virions adopting an oval rather than rod-shaped morphology. VGZ3 transduced human hepatoma cells in vitro at an efficiency roughly 10-fold greater than baculovirus lacking VSV G (the virus Z4). VGZ3 was also capable of transducing cell lines that could not be transduced efficiently by Z4. We provide evidence that VSV G protein may enhance transduction by increasing the efficiency of escape of baculovirus from intracellular vesicles rather than by increasing cell binding or uptake of the virus. The possible use of this and related baculoviruses in gene therapy is discussed.

Individual rotavirus-like particles containing 120 molecules of fluorescent protein are visible in living cells

Rotaviruses are large, complex icosahedral particles consisting of three concentric capsid layers. When the innermost capsid protein VP2 is expressed in the baculovirus-insect cell system it assembles as core-like particles. The amino terminus region of VP2 is dispensable for assembly of virus-like particles (VLP). Coexpression of VP2 and VP6 produces double layered VLP. We hypothesized that the amino end of VP2 could be extended without altering the auto assembly properties of VP2. Using the green fluorescent protein (GFP) or the DsRed protein as model inserts we have shown that the chimeric protein GFP (or DsRed)-VP2 auto assembles perfectly well and forms fluorescent VLP (GFP-VLP2/6 or DsRed-VLP2/6) when coexpressed with VP6. The presence of GFP inside the core does not prevent the assembly of the outer capsid layer proteins VP7 and VP4 to give VLP2/6/7/4. Cryo-electron microscopy of purified GFP-VLP2/6 showed that GFP molecules are located at the 5-fold vertices of the core. It is possible to visualize a single fluorescent VLP in living cells by confocal fluorescent microscopy. In vitro VLP2/6 did not enter into permissive cells or in dendritic cells. In contrast, fluorescent VLP2/6/7/4 entered the cells and then the fluorescence signal disappear rapidly. Presented data indicate that fluorescent VLP are interesting tools to follow in real time the entry process of rotavirus and that chimeric VLP could be envisaged as "nanoboxes" carrying macromolecules to living cells.

Detection and analysis of Autographa californica nuclear polyhedrosis virus mutants with defective interfering properties

Defective interfering particles (DIPs) were generated upon continuous production of Autographa californica nuclear polyhedrosis virus (AcNPV) in bioreactors. This configuration mimicked the serial undiluted passaging of virus, which is known to result in plaque-morphology mutants. Restriction enzyme analysis of DIP-containing preparations of extracellular virus showed the presence of many DNA fragments in less than equimolar amounts. These fragments were colinear on the physical map of AcNPV and extended from map position 1.7 to 45. These DIPs thus lacked 43% of the genetic information of the standard virus, including the polyhedrin and DNA polymerase genes. The existence of DIPs was confirmed by electron microscopy, where virions were observed with reduced length. Among the less than equimolar fragments in DIP-containing preparations, fragments were observed linking sequences from map positions 1.7 and 45 via a TGTT linker of unknown origin. The DIPs could not be plaque-purified and needed standard (helper) virus to replicate; DIP-containing preparations interfered with standard virus replication in an interference assay, which explained the reduction in productivity of an AcNPV expression vector-insect cell system in continuous bioreactor operations. The origin of these DIPs and their possible generation mechanism are discussed.

Fullerene-like organization of HIV gag-protein shell in virus-like particles produced by recombinant baculovirus

Virus-like particles produced by a recombinant baculovirus containing the HIV gag gene were examined by negative staining after delipidization. This technique demonstrated that the gag-protein shell consisted of radially arranged short rods which formed a network of ring-like structures. Similar structures were observed at the plasma membrane of infected cells which had been opened by wet-cleaving. Occasionally five or six subunits were observed forming a ring. These findings suggest that the gag-encoded precursor (pr55) is a rod-like molecule about 34 A in diameter and 85 A in length. A protein cylinder of such dimensions would have a molecular weight of 56K. The center-to-center distance of two neighboring rings formed by the rods was 66 +/- 8 A (N = 200) by direct measurements and 65 A as obtained from averaged images. This morphology and these dimensions indicate that the virus-like particles contain the gag precursor in the form of a near-spherical "fullerene-like" icosahedral shell. Our data indicate that the triangulation number of the rings equals 63. However, since one rod of pr55 is shared by two rings, the number of copies of the precursor will be 1890 as opposed to 2522 if the molecules were closely packed. The particle diameter of 102 nm deduced from the proposed model was close to the diameter obtained from thin sections of low-temperature-embedded specimens (103-108 nm).

Baculovirus--insect cell interactions

Baculovirus interactions with host cells range from the physical interactions that occur during viral binding and entry, to the complex and subtle mechanisms that regulate host gene expression and modify and regulate cellular and organismal physiology and defenses. Fundamental studies of baculovirus biochemistry and molecular biology have yielded many interesting and important discoveries on the mechanisms of these virus-host interactions. Information from such studies has also resulted in exciting new strategies for environmentally sound insect pest control, and in the development and improvement of a valuable eukaryotic expression vector system. In addition a number of important and valuable model biological systems have emerged from studies of baculoviruses. These include robust systems for studies of eukaryotic transcription, viral DNA replication, membrane fusion, and apoptosis. Because functions have been identified for only a small number of baculovirus genes, we can expect many exciting new discoveries in the future and an unfolding of the complex and intricate relationship between baculoviruses and insect cells.

Multiple interactions control the intracellular localization of the herpes simplex virus type 1 capsid proteins

Herpes simplex virus type 1 (HSV-1) capsid assembly takes place in the nucleus of infected cells. However, when each of the outer capsid shell proteins, VP5, VP23 and VP26, is expressed in the absence of any other HSV-1 proteins, it does not localize to the nucleus but is distributed throughout the cell. We have previously shown that the HSV-1 capsid scaffolding protein, preVP22a, can relocate VP5 into the nucleus but does not influence the distribution of VP23. We now demonstrate that the outer capsid shell protein, VP19C, is able to relocate both VP5 and VP23 separately into the nucleus. However, nuclear localization of VP26 is only observed when VP5 is present together with either VP19C or preVP22a. Thus, pair-wise interactions involving all of the abundant capsid proteins have now been identified. Electron microscope examination of insect cells coinfected with recombinant baculoviruses expressing VP19C and VP5 reveals the presence of 70 nm diameter 'capsid-like' structures, suggesting that these two proteins can form the basic capsid shell.

Avian influenza virus hemagglutinin display on baculovirus envelope: cytoplasmic domain affects virus properties and vaccine potential

Hemagglutinin (HA) is the major immunogen on the envelope of avian influenza virus (AIV). Therefore we constructed two recombinant baculoviruses: Bac-HA, expressing histidine-tagged HA with the cytoplasmic domain (CTD) derived from HA, and Bac-HA64, expressing histidine-tagged HA with the CTD derived from baculovirus envelope protein gp64. After infection, HA with either CTD was expressed and anchored on the plasma membrane of Sf-9 cells, as revealed by confocal microscopy. Immunogold electron microscopy demonstrated that both Bac-HA and Bac-HA64 displayed HA on the viral surface. However, analyses of purified viruses revealed that significantly more HA was incorporated into Bac-HA64 than into Bac-HA. In comparison with Bac-HA, Bac-HA64 significantly improved the gene delivery and transgene expression in mammalian cells, as determined by quantitative real-time polymerase chain reaction and flow cytometry. Bac-HA64 elicited significantly higher hemagglutination inhibition titers in mouse models than Bac-HA and the negative controls. These data collectively confirmed that the gp64 CTD, in comparison with HA CTD, resulted in more efficient HA incorporation into baculovirus, more efficient transgene delivery and expression, and elevated immunogenicity. This is the first report demonstrating the potential of HA-pseudotyped baculovirus as an avian influenza vaccine and that the choice of CTD tremendously affects baculovirus properties and vaccine efficacy.

Characterization of virus-like particles produced by a recombinant baculovirus containing the gag gene of the bovine immunodeficiency-like virus

The entire gag gene of the bovine immunodeficiency-like virus (BIV) was inserted behind the strong polyhedron promoter of Autographa californica nuclear polyhedrosis virus (AcNPV). The resultant recombinant baculovirus (AcNPV-BIVgag) was used to infect insect cells in order to overexpress and characterize BIV gag gene products. The infection resulted in the high-level expression of a protein similar in size to the predicted BIV gag precursor (Pr53gag). BIV Pr53gag was detected in AcNPV-BIVgag-infected insect cells and in culture supernatants. Electron microscopy of these cells revealed an abundance of virus-like particles (VLPs) in the cytoplasm, budding from the cell membrane, and free in the culture medium. The size and morphology of the VLPs were similar to those of the immature forms of BIV observed in infected mammalian cells. The VLPs sedimented at a density of 1.16 g of sucrose per milliliter in linear gradients and were shown to contain the majority of the supernatant Pr53gag. Antigenic determinants on Pr53gag from VLPs were recognized by BIV and HIV-1 antiserum, and serum from rats immunized with VLPs reacted with recombinant and viral BIV Pr53gag and processed products. The protease (PR) activity in BIV virions was capable of processing recombinant Pr53gag; this activity was blocked by pepstatin A, a potent aspartyl PR inhibitor. Baculovirus-expressed BIV Pr53gag appears to be an excellent source of gag precursor; it may prove useful for structural studies and enable the development of assays to detect retroviral PR inhibitors. The data further suggest that unprocessed BIV Pr53gag plays a major role in the assembly of BIV particles. The expression of other BIV structural genes in insect cells may prove instructive in the study of molecular events involved in the assembly and processing of these BIV proteins.

Morphological and molecular evidence that Culex nigripalpus baculovirus is an unusual member of the family Baculoviridae

We present evidence that a newly discovered mosquito virus from Culex nigripalpus is an unusual member of the family BACULOVIRIDAE: Development of this virus was restricted to nuclei of midgut epithelial cells in the gastric caeca and posterior stomach. The globular occlusion bodies were not enveloped, measured around 400 nm in diameter, occurred exclusively in nuclei of infected cells and typically contained four, sometimes up to eight, virions. The developmental sequence involved two virion phenotypes: an occluded form (ODV) that initiated infection in the midgut epithelial cells, and a budded form that spread the infection in the midgut. Each ODV contained one rod-shaped enveloped nucleocapsid (40x200 nm). The double-stranded DNA genome was approximately 105-110 kbp with an estimated GC content of 52%. We have sequenced approximately one-third of the genome and detected 96 putative ORFs of 50 amino acids or more including several genes considered to be unique to baculoviruses. Phylogenetic analysis of the amino acid sequences of DNApol and p74 placed this virus in a separate clade from the genera NUCLEOPOLYHEDROVIRUS: and GRANULOVIRUS: We provisionally assign this virus in the genus NUCLEOPOLYHEDROVIRUS:, henceforth abbreviated as CuniNPV (for Culex nigripalpus nucleopolyhedrovirus), and suggest that, awaiting additional data to clarify its taxonomic status, it may be a member of a new genus within the family BACULOVIRIDAE:

The 1,629-nucleotide open reading frame located downstream of the Autographa californica nuclear polyhedrosis virus polyhedrin gene encodes a nucleocapsid-associated phosphoprotein

A 78-kDa protein was produced in bacteria from a clone of the 1,629-nucleotide open reading frame located immediately downstream from the polyhedrin gene of Autographa californica nuclear polyhedrosis virus. The identity of this protein was confirmed by its reactivity with peptide antiserum and amino terminal peptide sequencing after purification from transformed bacteria. The polypeptide was used to produce polyclonal antisera in rabbits. Immunoblot analysis of insect cells infected with the baculovirus indicated that two related proteins with molecular masses of 78 and 83 kDa were synthesized late in infection. Biochemical fractionation studies indicated that both of these proteins were present in purified nucleocapsids from budded and occluded virus preparations. Immunoprecipitation of 32P-labeled proteins and treatment of purified nucleocapsids with alkaline phosphatase demonstrated that the 83-kDa protein was a phosphorylated derivative of the 78-kDa protein. Furthermore, immunoelectron microscopy revealed that the proteins were localized to regions of nucleocapsid assembly within the infected cell and appeared to be associated with the end structures of mature nucleocapsids.

Electron tomography and simulation of baculovirus actin comet tails support a tethered filament model of pathogen propulsion

Several pathogens induce propulsive actin comet tails in cells they invade to disseminate their infection. They achieve this by recruiting factors for actin nucleation, the Arp2/3 complex, and polymerization regulators from the host cytoplasm. Owing to limited information on the structural organization of actin comets and in particular the spatial arrangement of filaments engaged in propulsion, the underlying mechanism of pathogen movement is currently speculative and controversial. Using electron tomography we have resolved the three-dimensional architecture of actin comet tails propelling baculovirus, the smallest pathogen yet known to hijack the actin motile machinery. Comet tail geometry was also mimicked in mixtures of virus capsids with purified actin and a minimal inventory of actin regulators. We demonstrate that propulsion is based on the assembly of a fishbone-like array of actin filaments organized in subsets linked by branch junctions, with an average of four filaments pushing the virus at any one time. Using an energy-minimizing function we have simulated the structure of actin comet tails as well as the tracks adopted by baculovirus in infected cells in vivo. The results from the simulations rule out gel squeezing models of propulsion and support those in which actin filaments are continuously tethered during branch nucleation and polymerization. Since Listeria monocytogenes, Shigella flexneri, and Vaccinia virus among other pathogens use the same common toolbox of components as baculovirus to move, we suggest they share the same principles of actin organization and mode of propulsion.

Nuclear transport of baculovirus: revealing the nuclear pore complex passage

Baculoviruses are one of the largest viruses that replicate in the nucleus of their host cells. During an infection the capsid, containing the DNA viral genome, is released into the cytoplasm and delivers the genome into the nucleus by a mechanism that is largely unknown. Here, we used capsids of the baculovirus Autographa californica multiple nucleopolyhedrovirus in combination with electron microscopy and discovered this capsid crosses the NPC and enters into the nucleus intact, where it releases its genome. To better illustrate the existence of this capsid through the NPC in its native conformation, we reconstructed the nuclear import event using electron tomography. In addition, using different experimental conditions, we were able to visualize the intact capsid interacting with NPC cytoplasmic filaments, as an initial docking site, and midway through the NPC. Our data suggests the NPC central channel undergoes large-scale rearrangements to allow translocation of the intact 250-nm long baculovirus capsid. We discuss our results in the light of the hypothetical models of NPC function.

Characterization of a non-occluded baculovirus-like agent pathogenic to penaeid shrimp

A non-occluded baculovirus-like agent recently isolated by this laboratory from moribund Penaeus japonicus shrimps obtained from China and named Chinese baculovirus (CBV) was purified and some of its properties characterized. Under the electron microscope, negatively stained virus particles were rod-shaped, enveloped, and measured 322 to 378 nm in length and 130 to 159 nm in diameter. The nucleoprotein core exhibited a unique striated structure and measured 316 to 350 nm in length and 65 to 66 nm in diameter. The striations appear to be the result of the stacking of ring-like structures. These rings consisted of 2 rows of 12 to 14 globular subunits. Each globular subunit measured approximately 10 nm in diameter. SDS-PAGE gels of purified virus preparations showed, among several, 4 prominent protein bands with approximate molecular weights of 19, 23.5, 27.5 and 75 kDa. The structural viral proteins were identified by western blot analysis using polyclonal hyperimmune serum made against purified CBV. The 19, 27.5, and 75 kDa structural proteins were determined to be non-glycosylated components associated with the viral envelope. The 23.5 kDa protein, also non-glycosylated, was identified with the capsid structure. Viral genomic DNA digested with Hind III restriction endonuclease revealed at least 29 different fragments with a conservatively estimated total size of at least 183 kb.

Epizootiology and transmission of a newly discovered baculovirus from the mosquitoes Culex nigripalpus and C. quinquefasciatus

Reports of mosquito baculoviruses are extremely uncommon and epizootics in field populations are rarely observed. We describe a baculovirus that was responsible for repeated and extended epizootics in field populations of Culex nigripalpus and C. quinquefasciatus over a 2 year period. These mosquito species are important vectors of St Louis and Eastern equine encephalitis in the United States. Our initial attempts to transmit this baculovirus to mosquitoes in the laboratory were unsuccessful. A salt mixture similar to that found in water supporting infection in the field was used in laboratory bioassays and indicated that certain salts were crucial to transmission of the virus. Further investigations revealed conclusively that transmission is mediated by divalent cations: magnesium is essential, whereas calcium inhibits virus transmission. These findings represent a major advancement in our understanding of the transmission of baculoviruses in mosquitoes and will allow characterization of the virus in the laboratory. In addition, they can explain, in great part, conditions that support epizootics in natural populations of mosquitoes that vector life-threatening diseases of man and animals.

Magnetic resonance imaging of viral particle biodistribution in vivo

We describe here a technique for the visualization of viral vector delivery by magnetic resonance imaging (MRI) in vivo. By conjugating avidin-coated baculoviral vectors (Baavi) with biotinylated ultra-small superparamagnetic iron oxide particles (USPIO), we are able to produce vector-related MRI contrast in the choroid plexus cells of rat brain in vivo over a period of 14 days. Ten microlitres of 2.5 x 10(10) PFU/ml nuclear-targeted LacZ-encoding Baavi with bUSPIO coating was injected into rat brain ventricles and visualized by MRI at 4.7 T. As baculoviruses exhibit restricted cell-type specificity in the rat brain, altered MRI contrast was detected in the choroid plexus of the injected ventricles. No specific signal loss was detected when wild-type baculoviruses or intact biotinylated USPIO particles were injected into the lateral ventricles. Cryosectioned brains were stained for nuclear-targeted beta-galactosidase gene expression, which was found to colocalize with MRI contrast. This study provides the first proof of principle for robust and non-invasive viral vector MRI by using avidin-displaying viruses in vivo. Considering the widespread use of MRI in current medical imaging, the approach is likely to provide numerous future applications in imaging of therapeutic gene transfer.

Assembly of single-shelled cores and double-shelled virus-like particles after baculovirus expression of major structural proteins P3, P7 and P8 of Rice dwarf virus

Expression of the core capsid protein P3 of Rice dwarf virus in a baculovirus system resulted in the formation of single-shelled core-like particles in insect cells in the absence of any other capsid proteins. Double-shelled virus-like particles were also observed upon mixing or co-expression of P3 and the major outer capsid protein P8, suggesting that P3 and P8 have the ability to form double-shelled particles both in vivo and in vitro. Core protein P7 expressed in a similar manner was incorporated into the virus-like particles.

Physicochemical analysis of the hepatitis B virus core antigen produced by a baculovirus expression vector

The hepatitis B virus particle consists of an envelope carrying the surface antigen of the virus and an internal capsid consisting of the core antigen (HBcAg). The internal capsid contains the circular, partially dsDNA genome and the viral polymerase. Empty core particles have been produced in Spodoptera frugiperda cells using a recombinant baculovirus vector, YM1KTc, that expresses a 21.4K derivative of the HBcAg gene. The particles have been purified to homogeneity by caesium chloride density gradient centrifugation followed by glycerol gradient centrifugation. Physicochemical analysis of the core particles showed that they exhibited a sedimentation coefficient (s20,(0)w) of 82.5S and a diffusion coefficient (D) of 1.28 x 10(-7) cm2/s. The Mr obtained by substitution of these values in the Svedberg equation was 5.8 x 10(6), using a partial specific volume of 0.73 ml/g for the viral protein as estimated from the amino acid composition. The Mr determined from sedimentation equilibrium analyses was 6.3 x 10(6). Spectrophotometric and metabolic labelling analyses failed to detect nucleic acids in the core preparations. The data are at variance with the prediction that cores exhibit a T = 3 symmetry and contain some 180 subunits. The results suggest that the baculovirus-expressed cores may contain up to 300 subunits of HBcAg protein.

High efficiency gene transfer into cultured primary rat and human hepatic stellate cells using baculovirus vectors

BACKGROUND/AIMS

Gene transfer into hepatic stellate cells (HSC) is inefficient when using plasmid-based transfection methods; viral-based systems are therefore being developed. A baculovirus system has recently been shown to be useful for expressing genes in mammalian cells. The aim of this study was to determine if baculovirus vectors can infect and express target genes in rat and human HSC and to assess potential cytotoxic and modulatory effects of infection.

METHODS

A recombinant baculovirus vector (AcCALacZ) carrying the LacZ gene was used to infect HSC. beta-Galactosidase assays and electron microscopy were used to determine efficiency of infection and gene expression. Counting of trypan blue negative cells was used to assess cytotoxic/cytostatic effects of infection. Measurement of protein content of cells and alpha-smooth muscle actin expression were performed to assess the effects of baculovirus on cell function/phenotype.

RESULTS

Baculovirus infection of activated HSC was highly efficient (> 90%) and provided long-term LacZ gene expression (15 days) in the absence of cytotoxic, cytostatic or modulatory effects. Infection of freshly isolated cells was also observed but at lower levels (20%).

CONCLUSIONS

Baculovirus vectors can therefore be used to deliver target genes to cultured rat and human HSC with high efficiency and longevity in the absence of detrimental effects on cell function.

A comparative study of three different isolates of white spot virus

Three separate isolates of white spot virus (WSV) purified from 3 different penaeid shrimp species from different countries were compared morphologically, biochemically, and genomically using the following techniques; negative stain electron microscopy, sodium dodecyl-sulfate polyacrylamide gel electrophoresis/western blot, and restriction fragment length polymorphism (RFLP), respectively. Under the electron microscope, the 3 isolates were indistinguishable. Their nucleoprotein cores exhibited the unique striated structure characteristic of the baculovirus-like agents associated with white spot syndrome. The dimensions of the nucleoprotein cores were also identical for all 3 isolates. SDS-PAGE gels of purified virus preparations showed all 3 to be identical in the position of at least 3 of the most prominent protein bands of WSV, with approximate molecular weights of 19, 23.5, and 27.5 kDa. Western blot analyses also revealed these 3 same protein bands in identical positions for all 3 isolates. RFLP analyses of the viral genomes using Hind III and EcoR 1 enzymes revealed that although the 3 isolates were identical when cut with EcoR I, the isolate from Penaeus japonicus from China was distinguishable from the other 2 genomes (P. monodon from Indonesia and P. setiferus from the U.S.) when cut with Hind III.

Improved display of synthetic IgG-binding domains on the baculovirus surface

Improved display of foreign protein moieties in combination with beneficial alteration of the viral surface properties should be of value for targeted and enhanced gene delivery. Here, we describe a vector based on Autographa californica multiple nucleopolyhedrovirus (AcMNPV) displaying synthetic IgG-binding domains (ZZ) of protein A fused to the transmembrane anchor of vesicular stomatitis virus (VSV) G protein. This display vector was equipped with a GFP/EGFP expression cassette enabling fluorescent detection in both insect and mammalian cells. The virus construct displayed the biologically active fusion protein efficiently and showed increased binding capacity to IgG. As the display is carried out using a membrane anchor of foreign origin, gp64 is left intact for virus entry, which may increase gene expression in the transduced mammalian cells. In addition, the viral vector can be targeted to any desired cell type via binding of ZZ domains when an appropriate IgG antibody is available.