Application of a Novel Radioimmunoassay to Identify Baculovirus Structural Proteins That Share Interspecies Antigenic Determinants

Molecular Engineering of the Autographa californica Nuclear Polyhedrosis Virus Genome: Deletion Mutations Within the Polyhedrin Gene

We describe a method to introduce site-specific mutations into the genome of Autographa californica nuclear polyhedrosis virus. Specifically, the A. californica nuclear polyhedrosis virus gene for polyhedrin, the major protein that forms viral occlusions in infected cells, was mutagenized by introducing deletions into the cloned DNA fragment containing the gene. The mutagenized polyhedrin gene was transferred to the intact viral DNA by mixing fragment and viral DNAs, cotransfecting Spodoptera frugiperda cells, and screening for viral recombinants that had undergone allelic exchange. Recombinant viruses with mutant polyhedrin genes were obtained by selecting the progeny virus that did not produce viral occlusions in infected cells (occlusion-negative mutants). Analyses of occlusion-negative mutants demonstrated that the polyhedrin gene was not essential for the production of infectious virus and that deletion of certain sequences within the gene did not alter the control, or decrease the level of expression, of polyhedrin. An early viral protein of 25,000 molecular weight was apparently not essential for virus replication in vitro, as the synthesis of this protein was not detected in cells infected with a mutant virus.

Physical Analysis of Autographa californica Nuclear Polyhedrosis Virus Transcripts for Polyhedrin and 10,000-Molecular-Weight Protein

In Autographa californica nuclear polyhedrosis virus-infected cells, polyhedrin, the major structural polypeptide of the viral occlusions, and a low-molecular-weight viral protein with a molecular weight of approximately 10,000 (10K) accumulated to high levels late in infection. Two polyadenylated RNAs 1,200 and 630 bases in size were the most abundant viral transcripts present in the cytoplasm at 48 h postinfection. Evidence is presented that these RNAs were the transcripts for polyhedrin and 10K proteins. The 630-base RNA and five other major polyadenylated RNAs present at 48 h postinfection mapped within or near A. californica nuclear polyhedrosis virus EcoRI-P. The DNA sequences that code for polyhedrin mRNA were examined by S1 nuclease analysis. The polyhedrin gene contained no detectable introns and mapped at 3,990 to 5,200 base pairs to the right of the origin of the circular A. californica nuclear polyhedrosis virus physical map. Heterogeneity at the 5' end of polyhedrin mRNA was observed by using S1 nuclease analysis with 5' end-labeled DNA probes.

High resolution two-dimensional gel electrophoresis of structural proteins of baculoviruses of Autographa californica and Porthetria (lymantria) dispar

The structural polypeptides of baculoviruses of Autographa californica (AcMNPV) and Porthetria dispar (PdMNPV) were analyzed by two-dimensional (2-D) gel electrophoresis. Purified proteins were solubilized in urea-NP40 mix and separated by isoelectric focusing in the first dimension; electrophoresis in the presence of sodium dodecyl sulfate (SDS) separated proteins by molecular weight in the second dimension. Eighty-one acidic polypeptides ranging in molecular weight from 13,500 to 86,000 Da were resolved in AcMNPV enveloped virions. The predominant polypeptide had a molecular weight of 41,500 and was considered to be the major capsid protein. Nucleocapsids from AcMNPV were resolved into 64 polypeptides. At least 11 of the polypeptides, including most of the high molecular weight proteins, that were not resolved in nucleocapsids were considered to be envelope proteins. For PdMNPV enveloped virions, there were 95 acidic polypeptides ranging in molecular weight from 13,500 to 85,500. The predominant polypeptide had a molecular weight of 46,500 Da. Polyhedral proteins (polyhedrin) isolated from protease-inactivated polyhedra and separable into a single major polypeptide (approx. 31,000) on one-dimensional SDS-polyacrylamide gel electrophoresis were resolved into six polypeptides for both viruses. All six polyhedrin polypeptides had the same molecular weight, but their isoelectric points ranged from pH 5.3 to 5.9 for AcMNPV and from pH 5.7 to 6.2 for PdMNPV. These six polypeptides were also detected when protease-inactivated or noninactivated whole polyhedra were analyzed directly by 2-D electrophoresis. It is assumed that not all the observed baculovirus polypeptides were unique species. Some proteins, especially the polyhedrin polypeptides, appeared to be related and had altered mobilities as a consequence of post-translational modifications.

Milestones leading to the genetic engineering of baculoviruses as expression vector systems and viral pesticides

The baculovirus expression vector system (BEVS) is widely established as a highly useful and effective eukaryotic expression system. Thousands of soluble and membrane proteins that, in general, are correctly folded, modified, sorted and assembled to produce highly authentic recombinant proteins have been cloned and expressed. This historical chronology and perspective will focus on the original, peer-reviewed discoveries that were pioneering and seminal to the development of the BEVS and that provided the basis for subsequent and more recent developments and applications.

Bombyx mori nucleopolyhedrovirus ORF79 encodes a 28-kDa structural protein of the ODV envelope

Open reading frame 79 of Bombyx mori nucleopolyhedrovirus (Bm79) is a conserved gene whose homologues have been identified in all 26 of the completely sequenced baculovirus genomes, including lepidopteran NPVs and GVs, hymenopteran NPVs, and a dipteran baculovirus. Northern blot analysis showed that the Bm79 transcript was about 850 nucleotides long and was initiated 12 h p.i. Temporal expression analysis revealed a 28-kDa protein, which was detected beginning 24 h p.i. using a polyclonal antibody against GST-Bm79 fusion protein. The 28-kDa protein was detected in the occlusion-derived virus envelope (ODV-E), but not in budded viruses. This observation was confirmed by observing ultrathin sections of polyhedra using immunoelectron microscopy. This demonstrated that the protein was present within the nuclei of cells. These results suggest that Bm79 is a functional gene that encodes a structural protein associated with the envelope of occlusion-derived virus (ODV).

Determination of the protein composition of the occlusion-derived virus of Autographa californica nucleopolyhedrovirus

The occlusion derived form of baculovirus is specially adapted for primary infection of the host midgut epithelium. As such, the virion must contain the proteins essential for host range determination and initiation of infection. Because knowledge of virion composition is a prerequisite for functional investigation, this study used a combination of techniques to identify the proteins present within or associated with the occlusion-derived virus (ODV) virion. Thirty-one proteins, including proteins known to be essential for viral DNA replication, were identified with confidence. An additional 13 proteins were identified by using one of the three techniques. A comparison of gene conservation among the ODV proteins encoded in the 16 sequenced baculoviridae genomes is presented. With knowledge of the composition of ODV, it is now possible to target proteins and study their role(s) during primary infection.

Identification of two major virion protein genes of white spot syndrome virus of shrimp

White Spot Syndrome Virus (WSSV) is an invertebrate virus, causing considerable mortality in shrimp. Two structural proteins of WSSV were identified. WSSV virions are enveloped nucleocapsids with a bacilliform morphology with an approximate size of 275 x 120 nm, and a tail-like extension at one end. The double-stranded viral DNA has an approximate size 290 kb. WSSV virions, isolated from infected shrimps, contained four major proteins: 28 kDa (VP28), 26 kDa (VP26), 24 kDa (VP24), and 19 kDa (VP19) in size, respectively. VP26 and VP24 were found associated with nucleocapsids; the others were associated with the envelope. N-terminal amino acid sequences of nucleocapsid protein VP26 and the envelope protein VP28 were obtained by protein sequencing and used to identify the respective genes (vp26 and vp28) in the WSSV genome. To confirm that the open reading frames of WSSV vp26 (612) and vp28 (612) are coding for the putative major virion proteins, they were expressed in insect cells using baculovirus vectors and analyzed by Western analysis. A polyclonal antiserum against total WSSV virions confirmed the virion origin of VP26 and VP28. Both proteins contained a putative transmembrane domain at their N terminus and many putative N- and O-glycosylation sites. These major viral proteins showed no homology to baculovirus structural proteins, suggesting, together with the lack of DNA sequence homology to other viruses, that WSSV may be a representative of a new virus family, Whispoviridae.

Autographa californica nuclear polyhedrosis virus: subcellular localization and protein trafficking of BV/ODV-E26 to intranuclear membranes and viral envelopes

The Autographa californica nuclear polyhedrosis virus da26 gene codes for an envelope protein of both budded virus (BV) and occlusion derived virus (ODV). Western blot and temporal analysis of infected cell extracts detected a protein of 26 kDa by 4 h postinfection (p.i.). The amount of protein increased by 16 h p.i. and remained at high levels throughout infection. By 36 h p.i. several additional immunoreactive proteins were detected which migrated at approximately 18 kDa and remained through 96 h p.i. Western blot analysis of purified virus envelope and nucleocapsid preparations revealed that both the 26- and 18-kDa proteins are structural proteins of the envelope of BV and ODV. Immunoelectron microscopy performed at a time when only the 26-kDa species of the protein was present confirmed that the protein located to ODV envelope. The protein was named BV/ODV-E26 to designate incorporation into viral progeny, envelope location, and apparent molecular weight. Studies designed to follow localization of BV/ODV-E26 demonstrated that early in infection, the protein was incorporated into cytoplasmic vesicles and by 16 h p.i., BV/ODV-E26 was detected in the nucleus associated with virus-induced intranuclear microvesicles and ODV envelope. Coimmunoprecipitation and yeast two-hybrid assays showed that BV/ODV-E26 and FP25K were capable of interacting with each other to form a complex and coimmunoprecipitation assays indicated that cellular actin was a third component of this complex. Together, these data suggest that FP25K and cellular actin may participate in the regulation, or movement through the cell, of baculovirus proteins and/or virus nucleocapsids.

Detection and identification of multiple baculoviruses using the polymerase chain reaction (PCR) and restriction endonuclease analysis

A technique using the polymerase chain reaction (PCR) and restriction analysis was developed for the simultaneous detection of eight baculoviruses. The baculoviruses detected by this technique were Autographa californica multiple-embedded nuclear polyhedrosis virus (MNPV). Anticarsia gemmatalis MNPV, Bombyx mori MNPV, Orgyia pseudotsugata MNPV. Spodoptera frugiperda MNPV, S. exigua MNPV, Anagrapha falcifera MNPV, Heliothis zea single-embedded nuclear polyhedrosis virus (SNPV). A highly conserved DNA sequence within the coding region of the polyhedrin gene was targeted for amplification. One pair of degenerate primers was designed, and PCR conditions were optimized to produce 575 base pair fragments for all eight baculoviruses. Restriction analysis of the PCR products resulted in distinct profiles for each virus. This technique would be useful in monitoring the release of wild type as well as genetically engineered baculoviruses.

Localization of the 34 kDa polyhedron envelope protein in Spodoptera frugiperda cells infected with Autographa californica nuclear polyhedrosis virus

Using immuno-electron microscopy the 34 kDa polyhedron envelope (PE) phosphoprotein (pp 34) was localized in cells infected with Autographa californica multiple-nucleocapsid nuclear polyhedrosis virus (AcMNPV). In wild-type AcMNPV-infected cells this protein was found associated with electron-dense "spacers" and the polyhedron envelopes demonstrating their structural relationship. In these cells pp 34 was also found associated with fibrillar structures present in the nucleus and cytoplasm of infected cells. However, when cells were infected with an AcMNPV mutant with an inactivated pp 34 gene, antiserum against pp 34 still localized in fibrillar structures. In cells infected with AcMNPV mutants lacking p 10, and thus devoid of fibrillar structures, pp 34 localized normally with both electron-dense "spacers" and polyhedron envelopes. These data confirm that fibrillar structures are not essential for the morphogenesis of polyhedron envelopes and demonstrate that the association of anti pp 34 serum with these structures is specific but fortuitous.

Identification of virus-specific polypeptides and translatable mRNAs in the isolated pupal abdomens of the silkworm, Bombyx mori, infected with nuclear polyhedrosis virus

Analysis by sodium dodecyl sulfate-polyacrylamide gel electrophoresis demonstrated that infection of the isolated pupal abdomens of the silkworm, Bombyx mori, with B. mori nuclear polyhedrosis virus (BmNPV) caused generation of a number of polypeptides with a concomitant decrease of cellular polypeptides. These generated polypeptides were not identified as viral structural polypeptides, but were characterized as the degradation products of cellular polypeptides, as evidenced by the reaction with specific antiserum against storage proteins 1 and 2. Immunoblot analysis using anti-BmNPV serum identified at least 14 virus-specific polypeptides in the BmNPV-structural polypeptides of the virus. In vitro translation and subsequent immunoprecipitation with anti-BmNPV serum showed that translation yielded at least 15 polypeptides at the expense of cellular polypeptides. Time-course experiments showed that the viral structural polypeptides and virus-specific translatable mRNAs were not detectable until 3 days postinoculation. On the basis of the fact that the isolated pupal abdomens are in an arrested state of development, the delayed onset of virus-specific macromolecule production in the infected isolated pupal abdomens, as compared with that in the developing intact pupae, implies that some cellular function associated with the pupal-adult development is an important prerequisite for the efficient commencement of BmNPV replication.

Identification, sequence, and transcriptional mapping of the major capsid protein gene of the baculovirus Autographa californica nuclear polyhedrosis virus

The gene encoding the major capsid protein of the baculovirus Autographa californica nuclear polyhedrosis virus (AcMNPV) was identified, sequenced, and transcriptionally mapped. The location of the gene was determined by immunological screening of an expression library of AcMNPV open reading frame-beta-galactosidase fusions with an antibody raised to virus structural proteins. The DNA sequence of the corresponding region, which mapped within 56.6 and 58.0 map units on the AcMNPV genome, revealed a 1,040-base-pair open reading frame capable of encoding a 39-kilodalton polypeptide. The identity of the polypeptide was determined by Western blot (immunoblot) analysis of purified empty capsids with an antibody raised to the capsid-beta-galactosidase fusion protein. The identity of the peptide encoded by the gene was confirmed by immunoprecipitation of an in vitro translation product with RNA selected by hybridization to DNA sequences from the coding region of the gene. Transcripts of the capsid gene were analyzed by Northern (RNA) blots and mapped by nuclease protection and primer extension analysis. The capsid gene is transcribed maximally at 12 and 24 h postinfection but not in the presence of cycloheximide, a protein synthesis inhibitor, or aphidicolin, a viral DNA synthesis inhibitor, and is therefore classified as a late gene. The gene is transcribed in a counterclockwise direction with respect to the circular map. There are three transcriptional start sites, all containing the AGTAAG consensus sequence found at the start site of all late AcMNPV genes.

An epitope common to HLA class I and class II antigens, Ig light chains, and beta 2-microglobulin

The homology of class I major histocompatibility complex (MHC) antigens, class II MHC antigens, and immunoglobulin molecules has suggested their divergence from a common ancestral gene. We report here a monoclonal antibody (mAb), PAC.M1, which reacts with HLA class I heavy chains, HLA class II alpha and beta chains, and the light chain of human immunoglobulin by Western blot analysis. PAC.M1 reacted with 44 kd, 33 kd, and 29 kd species when tested on membrane glycoproteins from TRal, a B-lymphoblastoid cell line (B-LCL). Two-dimensional electrophoresis and Western blotting of TRal glycoproteins showed that these species had the appropriate electrophoretic mobilities for class I heavy chain and class II alpha and beta subunits. The presence of the epitope was verified on class II alpha and beta subunits by Western blotting of purified alpha beta-invariant chain complexes, and on class I heavy chains by Western blotting of purified class I antigens. The PAC.M1 mAb also reacted with immunoglobulin light chains when Western blotting was performed with normal human serum and purified IgG and IgM as antigens. While reactivity of the mAb with beta-2 microglobulin (beta 2m) was difficult to detect by Western blotting, binding of PAC.M1 to purified beta 2m was detectable in a solid-phase binding assay. Thus, PAC.M1 reacts with a determinant shared by a number of members of the immunoglobulin superfamily.

Use of the photoaffinity cross-linking agent N-hydroxysuccinimidyl-4-azidosalicylic acid to characterize salivary-glycoprotein-bacterial interactions

The present study has utilized the iodinatable cross-linking agent N-hydroxysuccinimidyl-4-azidosalicylic acid (ASA) to examine the specific interaction between the proline-rich glycoprotein (PRG) of human parotid saliva and Streptococcus sanguis G9B. The binding of 125I-ASA-PRG to Streptococcus sanguis G9B displayed saturation kinetics, reversibility and was inhibited by unlabelled PRG. Inhibition studies with other glycoproteins and saccharides indicated that binding was mediated by a bacterial adhesin with specificity towards N-acetylneuraminic acid, galactose, and N-acetylgalactosamine. After cross-linking, the 125I-ASA-PRG-adhesin complex could be extracted with SDS and separated from uncoupled 125I-ASA-PRG by gel filtration on Sepharose CL-6B. Approx. 1% of the 125I-ASA-PRG was cross-linked to the bacterial surface. Examination of the 125I-ASA-PRG-adhesin complex by SDS/polyacrylamide-gel electrophoresis/fluorography on 5% -(w/v)-polyacrylamide gels revealed that PRG was bound to two bacterial components. These findings support our previous suggestion that human salivary glycoproteins can specifically interact with oral streptococci and that these interactions occur between the glycoprotein's carbohydrate units and lectin(s) on the bacterial cell surface.

Immunoblot analyses of Candida albicans-associated antigens and antibodies in human sera

We tested 10 patient sera for the presence of immunoglobulin G (IgG) antibodies to Candida albicans and for C. albicans antigens by immunoblot analysis (i.e., electrotransfer blot radioimmunoassay) (G. E. Smith and M. D. Summers, J. Virol. 39:125-137, 1981). We evaluated sera from two patients at risk for candidiasis, five patients with systemic candidiasis documented by culture, and two patients who had experienced transient candidemia. Both the specificity and the relative amount of IgG antibodies to C. albicans in each serum sample were readily visualized by this technique, as was the absence of antibody from serum of neonatal and immunocompromised patients. No antibody species appeared to be uniquely associated with candidiasis patients (i.e., each antibody species present in the candidiasis patient was also present in sera of normal individuals or "at-risk" patients). IgG from rabbits immunized with whole cells or with a cytoplasmic fraction of C. albicans was used to detect C. albicans antigens in patient sera. Although several antigens were detected in the sera from patients with candidiasis, the same antigens were also detected in sera from patients at risk and in normal human serum. No antigens were detected in human serum when preimmune rabbit sera were used. These results suggest that the antigens detected by the rabbit antisera were human serum proteins that cross-reacted with C. albicans antigens. These findings may have important implications in studies of both the pathobiology of C. albicans and the serodiagnosis of candidiasis.

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.

Immunity against infection with Trypanosoma cruzi in mice correlates with presence of antibodies against three trypomastigote polypeptides

Repeated immunizations of CF1 mice with irradiated noninfectious Trypanosoma cruzi trypomastigotes resulted in partial protection against infection with live parasites. It also induced a limited number of antibody species that were reactive in Western blots with trypomastigote but not with epimastigote or amastigote polypeptides. These antibody species were strongly reactive with a 100,000-dalton polypeptide and much less reactive with at least two polypeptides greater than 200,000 daltons. Immunization with epimastigotes induced antibodies against a 57,000-dalton epimastigote-specific polypeptide but did not induce protective immunity.

Binding of Streptococcus mutans antigens to heart and kidney basement membranes

Using indirect immunofluorescence, alkali-extracted components of Streptococcus mutans were found to bind in vitro to capillary walls and sarcolemmal sheaths of monkey cardiac muscle and to glomerular and tubular basement membranes of monkey kidney. Adsorption of S. mutans components to tissue fragments was also detected by indirect radioimmunoassay and immunoblotting on nitrocellulose paper. Antibodies did not bind to untreated, control tissues in these experiments, proving that antigens shared by S. mutans and tissue components were not involved. Rabbit and monkey heart and kidney components bound S. mutans antigens of 24,000, 35,000, and 65,000 Mr. Monkey heart also bound molecules of 90,000 and 120,000 Mr. Rabbits immunized by intravenous injection of disrupted S. mutans cells developed severe nephritis that was characterized by the deposition of immunoglobulins, complement component C3, and S. mutans antigens in the glomeruli. Immunoglobulin G eluted from nephritic kidneys reacted in immunoblots with the 24,000, 35,000, and 65,000 Mr components of S. mutans extract, indicating that the antigens that bound to tissue in vitro also bound in vivo and reacted with antibodies in situ. Antibodies to other S. mutans antigens were not detected in the kidney eluate, although they were present in the serum of the same rabbit.

Monoclonal antibodies to a monkeypox virus polypeptide determinant

Three monkeypox virus (MPV) antibody-secreting murine monoclones were characterized as being of the immunoglobulin G1 isotype, gave a 4+ reaction in the indirect fluorescent-antibody test, gave a positive reaction in the enzyme immunoassay, and did not neutralize MPV. These monoclonal antibodies were determined by the sodium dodecyl sulfate-polyacrylamide gel electrophoresis transblot method to react to a 15,500-molecular-weight MPV polypeptide. This reactivity could not be removed by adsorption to a vaccinia virus-infected cell suspension. The three monoclonal antibodies were specific for MPV when tested against epidemiologically unrelated isolates of cowpox virus, variola virus, vaccinia virus, and MPV.

Analysis of monoclonal antibodies reactive with human class II beta chains by two-dimensional electrophoresis and Western blotting

We have used the Western blotting technique to examine B lymphoblastoid cell line (B-LCL) membrane proteins separated by two-dimensional gel electrophoresis specifically to analyze the binding patterns of monoclonal antibodies to separated HLA class II antigen beta (beta) subunits. The B-LCL LG-10 (homozygous for DR7), in which at least two sets of class II molecules can be distinguished on the basis of different electrophoretic mobilities, was examined with five monoclonal antibodies which detect monomorphic determinants. Four of the antibodies reacted with only DR beta subunits, while one antibody, XD5.A11, reacted with DR and with additional beta chains. Examination of two polymorphic monoclonal antibodies, SFR3-DR5, specific for HLA-DR5, and SFR3-PI.1, which reacts with a determinant absent from DR3 and DR7 homozygous lines, showed that both bind beta subunits from Swei, a DR5 homozygous line. Purification of a subpopulation of Swei class II molecules using an SFR3-PI.1 affinity column showed that the determinants recognized by SFR3-DR5, SFR3-PI.1, and a monomorphic monoclonal antibody reactive only with HLA-DR beta subunits of LG-10, reacted with identical beta subunits. Additional class II antigen subunits reactive with XD5.A11 were nonreactive with the polymorphic antibodies and the HLA-DR-specific monomorphic monoclonal antibody.

Production of human beta interferon in insect cells infected with a baculovirus expression vector

Autographa californica nuclear polyhedrosis virus (AcNPV) was used as an expression vector for human beta interferon. By using specially constructed plasmids, the protein-coding sequences for interferon were linked to the AcNPV promoter for the gene encoding for polyhedrin, the major occlusion protein. The interferon gene was inserted at various locations relative to the AcNPV polyhedrin transcriptional and translational signals, and the interferon-polyhedrin hybrid genes were transferred to infectious AcNPV expression vectors. Biologically active interferon was produced, and greater than 95% was secreted from infected insect cells. A maximum of ca. 5 X 10(6) U of interferon activity was produced by 10(6) infected cells. These results demonstrate that AcNPV should be suitable for use as a eucaryotic expression vector for the production of products from cloned genes.

Identification of immunologically cross-reactive proteins of Sindbis virus: evidence for unique conformation of E1 glycoprotein from infected cells

Hyperimmune antisera to purified Sindbis (SIN) or Semliki Forest (SF) virus were used to identify alphavirus-specific and cross-reactive proteins in virions and infected cells. The hyperimmune sera participated in homologous and cross-cytolysis of alphavirus-infected cells, and the use of monospecific antisera to SIN structural proteins suggested that E1 and E2 could serve as target proteins in cytolysis. Proteins from purified virions or infected cells were extracted with Nonidet P-40, denatured by procedures for sodium dodecyl sulfate-polyacrylamide gel electrophoresis, transferred to nitrocellulose solid supports, and reacted with hyperimmune sera and 125I-labeled protein A (immunoblotting on denatured proteins). Alternatively, native proteins extracted by mild Nonidet P-40 treatment were precipitated with hyperimmune sera before denaturation by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. After immunoblotting, homologous antiserum reacted with the virus structural proteins E1, E2, capsid extracted from purified virions, and the counterparts of these proteins extracted from infected cells. In addition, PE2 and a 92,000-molecular-weight protein from infected cells reacted with homologous antiserum. These proteins were also immunoprecipitated with homologous antiserum. After immunoblotting, the Sindbis capsid protein was shown to be cross-reactive whether derived from purified virions or from infected cells; no cross-reactivity was observed with PE2 or E2 from either source, and the E1 glycoprotein was shown to be cross-reactive only when obtained from virions. However, the E1 glycoprotein could be cross-immunoprecipitated from infected cells (as well as from disrupted virions), and, in addition, capsid and a 92,000-molecular-weight protein were cross-immunoprecipitated from infected cells. These results suggest that a native conformation of the cell-associated E1 glycoproteins may be required for immunological cross-reactivity (immune precipitation), whereas virion but not cell-associated E1 retains immunological cross-reactivity after denaturation (immunoblot technique). The findings extend our previously published evidence which suggested that alphavirus maturation is accompanied by a change in immunological cross-reactivity with respect to E1.

HLA-DR7-specific monoclonal antibodies and a chimpanzee anti-DR7 serum detect different epitopes on the same molecule

We describe here two monoclonal antibodies with HLA-DR7 serologic specificity. The antibodies, SFR16-DR7M, a cytotoxic rat IgM antibody of high affinity, and SFR16-DR7G, a noncytotoxic antibody of the rat IgG 2a class, react with only DR7-positive cells in radioimmunoassay. The cytotoxic activity of SFR16-DR7M correlates completely with the presence of the DR7 specificity, and segregates with the DR7-bearing haplotype in a family. SFR16-DR7M precipitates a class II molecule with the electrophoretic characteristics of DR molecules from LG-10, an HLA-DR7 homozygous cell line. SFR16-DR7G completely inhibits the cytotoxicity of SFR16-DR7M, but only partially inhibits the cytotoxicity of a chimpanzee antiserum with DR7 specificity, Gay/Swei. In binding-inhibition studies, binding of SFR16-DR7M to LG-10 cells is only partially inhibited by the chimpanzee antiserum and vice versa. Both SFR16-DR7M and Gay/Swei reciprocally deplete the same class II molecules from a 35S-methionine-labeled detergent-solubilized membrane preparation of the LG-10 cell line. The chimpanzee serum Gay contains antibodies reactive with epitopes on separated DR7 beta chains, while both SFR16-DR7M and SFR16-DR7G bind only to DR7 alpha-beta complexes. These data suggest that at least two allogenic epitopes exist which result in the same serologic specificity, and that these epitopes differ in their requirement for alpha-beta complex formation.

Production of human beta interferon in insect cells infected with a baculovirus expression vector

Autographa californica nuclear polyhedrosis virus (AcNPV) was used as an expression vector for human beta interferon. By using specially constructed plasmids, the protein-coding sequences for interferon were linked to the AcNPV promoter for the gene encoding for polyhedrin, the major occlusion protein. The interferon gene was inserted at various locations relative to the AcNPV polyhedrin transcriptional and translational signals, and the interferon-polyhedrin hybrid genes were transferred to infectious AcNPV expression vectors. Biologically active interferon was produced, and greater than 95% was secreted from infected insect cells. A maximum of ca. 5 X 10(6) U of interferon activity was produced by 10(6) infected cells. These results demonstrate that AcNPV should be suitable for use as a eucaryotic expression vector for the production of products from cloned genes.

Characterization of Gypsy Moth ( Lymantria dispar ) Nuclear Polyhedrosis Virus

Characterization of the proteins and nucleic acid of the gypsy moth nuclear polyhedrosis virus isolated in Ithaca, N.Y. (LdNPV-IT) is presented. A total of 29 viral structural proteins were identified by sodium dodecyl sulfate-polyacrylamide gel electrophoresis when the virus was isolated in the absence of alkaline protease activity. Fourteen surface envelope viral proteins were identified by lactoperoxidase iodination. Eleven proteins were associated with nucleocapsids prepared by Nonidet P-40 detergent treatment. Distinct alterations of viral proteins were documented when virions were purified in the presence of occlusion body-associated alkaline protease(s). Restriction enzyme digests of viral DNA indicated that this isolate was composed of a large number of genetic variants. On the basis of the major molar fragments resulting from Eco RI, Bam HI, Bgl II, and Hin dIII digests, the molecular weight of the LdNPV genome was approximately 88 � 10 6 .

A monoclonal antibody (100C5) to the Lyt-2-T cell population expanding in MRL/Mp-lpr/lpr mice detects a surface antigen normally expressed on Lyt-2+ cells and B cells

MRL/Mp-lpr/lpr (MRL-lpr) mice develop a generalized lymphadenopathy reflecting the expansion of a Lyt-2- T cell population. The present report describes the pattern of reactivity of a xenogeneic monoclonal antibody (mAb 100C5) directed against this T cell population. By single- and two-color flow cytofluorometry analysis this mAb was found to stain brightly 80-90% of T cells in enlarged MRL-lpr lymph nodes. In contrast lymph node T cells from congenic MRL-MP-+/+ (MRL-+) mice were either unstained (70%) or weakly stained (30%), these latter cells being mostly Lyt-2+. Unexpectedly, all lymph node B cells from MRL-+ or MRL-lpr mice were as strongly 100C5+ as MRL-lpr T cells. Similar observations were made in C57BL/6-lpr/lpr and C57BL/6-+/+ mice. Molecular weight determination suggested that the 100C5 mAb binds to the same molecule (Mr = 220 000) on MRL-lpr T cells and normal B cells.

Occluded and Budded Autographa californica Nuclear Polyhedrosis Virus: Immunological Relatedness of Structural Proteins

The immunological relatedness of the structural proteins of the budded and occluded phenotypes of Autographa californica nuclear polyhedrosis virus was examined by reciprocal immunoblotting and by in situ peroxidase-antiperoxidase staining of virus-induced cell surface and intracellular antigens with antisera to both phenotypes. The molecular weights (MWs) of major structural proteins of both phenotypes that reciprocally cross-reacted were 92,500, 78,000, 62,500, 54,000, and 42,000. A highly immunogenic, major structural protein of the occluded phenotype of 46,000 MW was not recognized by antiserum to the budded phenotype, and a major structural protein of the budded phenotype, 48,000 MW, was not recognized by antiserum to the occluded phenotype. Both the budded and occluded phenotypes contained a protein of 33,500 MW that comigrated with polyhedrin (the matrix protein) and reacted with antiserum and monoclonal antibody to polyhedrin. Evidence was obtained for the apparent antigenic relatedness of proteins of different MWs from the budded and occluded phenotypes, possibly indicative of different processing of some proteins for the two phenotypes. Antiserum to the occluded phenotype recognized virus-induced cell surface antigens, indicating antigenic similarities between the occluded phenotype and envelope proteins of the budded phenotype. Antiserum to the budded phenotype recognized viral proteins produced before the appearance of cytopathic effect, whereas antiserum to the occluded phenotype did not.

A biochemical and biological comparison of three European isolates of nuclear polyhedrosis viruses from Agrotis segetum

Isolates of multiply-enveloped nuclear polyhedrosis viruses from Agrotis segetum (Lepidoptera: Noctuidae) populations in England (AsNPVE), France (AsNPVF) and Poland (AsNPVP), were compared biochemically and for their infectivity to A. segetum and Mamestra brassicae larvae. The electrophoretic profiles of DNA restriction endonuclease fragments and viral proteins appeared identical for AsNPVE and AsNPVF. AsNPVP was distinct by these techniques, although some of the virus particle polypeptides had the same mobilities as those of the other isolates. A serological comparison of the A. segetum NPV isolates with other baculoviruses, using indirect enzyme-linked immunosorbent assay, suggested that AsNPVP was no more closely related than M. brassicae NPV to the other A. segetum NPV isolates. AsNPVP had significantly lower infectivity for neonate A. segetum larvae (LD50 = 350 inclusion bodies) than AsNPVE (10 inclusion bodies) or AsNPVF (23 inclusion bodies). AsNPVE and AsNPVF did not appear to replicate in M. brassicae larvae, while AsNPVP produced a limited infection in this species.

Monoclonal antibodies to baculovirus structural proteins: determination of specificities by Western blot analysis

Conventional mouse hybridoma technology was utilized to produce a panel of monoclonal antibodies which reacted with baculovirus proteins. Using an enzyme-linked immunosorbent assay (ELISA), the hybridomas which were raised against polyhedrin from Autographa californica nuclear polyhedrosis virus (AcNPV) and Choristoeura fumiferana nuclear polyhedrosis virus (CfNPV) were found to cross-react differentially with polyhedrins and granulins from several species of baculoviruses. Hybridoma antibodies which reacted against the nonoccluded form (NOV) of AcNPV in an ELISA test expressed different specificities for the occluded form of the virus (OV), a mutant strain of AcNPV, and CfNPV. Four hybridoma clones produced antibody which neutralized the infectivity of AcNPV NOV. One hybridoma antibody reacted strongly with the uninfected Spodoptera frugiperda host cell line. Using Western blot analysis, it was shown that hybridoma antibodies against polyhedrin reacted differentially with the complete polypeptide and protease-generated fragments of polyhedrin. The polypeptide specificity of 19 of 28 hybridoma antibodies which reacted with OV and NOV of AcNPV was assigned using Western blot analysis.

Hybridization Selection and In Vitro Translation of Autographa californica Nuclear Polyhedrosis Virus mRNA

We isolated polyadenylated RNA from the cytoplasm of cells infected with Autographa californica nuclear polyhedrosis virus late after infection (21 h postinfection). At that time intracellular protein synthesis was directed almost exclusively toward infected cell-specific proteins. The polyadenylic acid-containing RNA sequences in the cytoplasm at 21 h postinfection were radiolabeled in vitro and hybridized to A. californica nuclear polyhedrosis virus DNA restriction fragments. The polyadenylic acid-containing RNA was derived from regions representing the entire viral genome. Translation in a reticulocyte cell-free protein-synthesizing system of cytoplasmic RNA selected by hybridization to viral DNA and polyadenylic acid-containing RNA produced almost identical polypeptide patterns, suggesting that late after infection almost all of the cytoplasmic polyadenylic acid-containing RNA present in infected cells was of viral origin. Polyhedrin protein (molecular weight, 33,000) and a number of virion structural proteins were among the translation products which were identified by immunoprecipitation and by comparing molecular weights. In addition, some tentative nonstructural infected cell-specific proteins were also detected. Using the hybridization selection technique, we determined that sequences complementary to the message coding for polyhedrin were located on Eco RI fragment I of A. californica nuclear polyhedrosis virus DNA, whereas sequences coding for a putative nonstructural protein (molecular weight, 39,000) were on Eco RI fragment J.