Rice ragged stunt Oryzavirus genome segment 9 encodes a 38 600 Mr structural protein

The complete nucleotide sequence of rice ragged stunt virus genome segment 9 (S9) was determined. The S9 segment is 1132 nucleotides long and has a long open reading frame starting from the first AUG codon at nucleotide position 14-16 and terminating at a UAG codon located at 1028-1030, which could encode a polypeptide with an Mr of 38 600 (P9). The encoded polypeptide has no sequence homology to polypeptides of any other plant reoviruses published previously. An immunological study demonstrated that P9 was the smallest of the structural proteins. The P9 polypeptide was expressed as a fusion protein with maltose binding protein in Escherichia coli. Antisera to purified virions and to the fusion protein reacted with both the bacterially expressed polypeptide and the smallest polypeptide of the purified virus in immunoblotting analyses.

Multimerization and transcriptional activation of the phosphoprotein (P) of vesicular stomatitis virus by casein kinase-II

Casein kinase-II (CK-II) is a widely distributed protein kinase, which plays numerous roles in the regulation of transcription through modification of transacting transcription factors. Phosphorylation of vesicular stomatitis virus (VSV) P protein by CK-II was found to be both necessary and sufficient for transcriptional activation. Upon treatment of P by CK-II, activity was acquired faster (t1/2 = 3.7 min) than were total phosphates (t1/2 = 7.4 min). Stoichiometry was 2 mol phosphate/mol P, indicating activation by phosphorylation at either one or both of two independent sites. The sites were identified by substituting aspartate (D) residues at either S60 or T62, producing proteins that were partly active without phosphorylation, but were fully active at higher concentrations; CK-II added only a single phosphate group to each of these, and conferred full activity. P protein doubly substituted with D at S60 and T62 was fully active without phosphorylation, and was not a substrate for CK-II. Active P protein, whether CK-II treated or doubly substituted, was shown by gel filtration and crosslinking to exist as a discretely multimeric, probably tetrameric, structure. The singly substituted mutants were partly multimeric, becoming fully so after CK-II treatment. Phosphorylation by CK-II thus mediates the self-association of P into the multimeric, transcriptionally active form.

Evidence of a major neutralizable conformational epitope region on VP2 of infectious pancreatic necrosis virus

A collection of neutralizing monoclonal antibodies (MAbs) produced against the LWVRT 60.1, Jasper and N1 strains of infectious pancreatic necrosis virus (IPNV) were selected for the analysis of VP2 epitopes. Previous characterization of the LW and JA MAbs allowed the identification of continuous and discontinuous epitopes but the topological localization of these sites remained obscure. The ability of these MAbs to differentiate individual epitopes was evaluated by additivity and competition assays using antigen-coated plates and by surface plasmon resonance (SPR), an automated biosensor system that is able to retain the conformation integrity of proteins. IPNV-neutralizing MAbs defined a major, conformational-dependent and immunodominant area where continuous epitopes represent portions of a larger discontinuous epitope. Moreover, weakly neutralizing MAbs could interact with internal sites, located within the foldings of the polypeptide chain. Anti-VP2 MAbs prepared against the European serotype N1 recognized and competed for epitopes present on the North American strain LWVRT 60.1 and Jasper. Attempts to establish the proximity of VP2 and VP3 epitopes have been made by SPR. Results indicate that these major structural proteins do not overlap in the virion.

Analysis of the role of the amino-terminal peptide of vaccinia virus structural protein precursors during proteolytic processing

Several VV structural proteins are produced by the removal of amino-terminal peptides from their cognate precursors. In the experiments reported here, directed genetic approaches were used to investigate the possible role of these terminal peptides in protein processing. As a model system, the FLAG epitope-tagged P25K precursor was used to prepare constructs in which the 31-amino-acid P25K N-terminal peptide was removed or replaced by heterologous sequences, while the -A-G*-A- cleavage motif was retained. Only a trace amount of the leaderless P25KF(delta 31) polypeptide was found within the mature virions, implying that proteolytic processing is necessary for the incorporation of the 25K product into mature virions. In trans-processing assays, significant levels of the 25K product were generated from wild-type P25KF and P4b:25KF, which consists of the 61-amino-acid P4b terminal peptide, and from P4b:25KF with 15, 30, or 44 residues of the amino terminus deleted. In contrast, only a small amount of 25K was produced from the TK:25KF, which contains the amino-terminal 30 residues of VV thymidine kinase, a protein which is not cleaved under normal circumstances. Furthermore, it has been hypothesized that a hydrophobic residue is required at position P4 relative to the -A-G*-A- motif for the cleavage to take place. An intermediate level of the 25K product was detected from the TK:25KF(Q29V) mutant which has the glutamine residue at P4 replaced with a valine residue, suggesting that the hydrophobic P4 residue and additional substrate determinants in the N-terminal peptide region are required for the proteolytic processing reaction to occur normally. Taken together, these data suggest that the amino-terminal peptides of the VV core proteins are to some extent interchangeable and that the residues proximal to the AGA site are of most importance.

Identification of a new viral protein containing CAp30 and NCp10 sequences in murine and feline leukemia retroviruses

Because Pr65gag is in part located in the nucleus and contains a putative bipartite nuclear targeting signal, we investigated the cellular location and structure of P55gag, a gag-encoded polyprotein known to lack the nucleocapsid (NC) protein NCp10. P55gag was found to be restricted to the cytoplasm of Moloney murine leukemia virus-infected cells. Of interest, P55gag was produced in cells infected by a viral protease deletion mutant and by a recombinant murine sarcoma virus known to lack the protease gene. Surprisingly, our structural and immunological studies indicated that P55gag also lacks carboxy-terminal residues of CAp30. During the course of studying P55gag, we detected a new viral protein within purified virus particles that contained NCp10 tryptic peptide sequences and a CAp30 tryptic peptide lacking in P55gag. This viral protein, which we have named nucleocapsid-related protein (NCRP), also contained antigenic epitopes present in CAp30 and NCp10. P55gag- and NCRP-like proteins were also observed in AKV murine leukemia virus and feline leukemia virus systems. The precise site of cleavage within Pr65gag that produces P55gag and NCRP is unknown but lies upstream of the CAp30-NCp10 junction within the carboxy-terminal domain of CAp30. The existence of a form of NCp10 containing carboxy-terminal CAp30 sequences raises interesting possibilities about its functional role in genomic RNA packaging and/or viral RNA dimerization.

Identification of structural proteins of channel catfish virus by mass spectrometry

Emerging methods that couple mass spectrometry of fragments generated from isolated proteins with database searching offer a powerful means of identifying proteins and the genes that encode them. We have applied this technology to a herpesvirus, channel catfish virus, and have identified 12 genes, 11 viral and 1 cellular, that encode 16 principal structural proteins. These proteins include three components of the mature capsid and a potential scaffolding protein present in immature capsids, three protein kinases, a C3HC4 zinc-binding protein and cellular actin located in the tegument, and a multiply hydrophobic protein associated with the envelope.

Nucleotide and deduced amino acid sequence of the structural protein genes of Japanese encephalitis viruses from different geographical locations

Strain variation among Japanese encephalitis (JE) virus isolates has been previously demonstrated by many workers using different methods. We report the nucleotide sequence of the 5' non-coding region and the nucleotide and deduced amino acid sequences of structural protein genes for eight wild-type JE virus strain isolated from different Asian countries (Vietnam, Nepal, Indonesia, Thailand, India, Japan and China). We compare these with five other published wild-type JE virus strains isolated from Japan and the mainland of China. No strain variation could be related to geographical location on the basis of the wild-type JE virus strains studied. The viruses differed from each other by between 21 (0.9%) and 111 (4.6%) nucleotides and by between 3 (0.4%) and 31 (4.2%) amino acids over the 2434 nucleotides examined. The amino acid divergence of the envelope (E) protein gene of the viruses was 4.2% or less among the 13 strains compared. Thus there is little genetic divergence in the strains studied. However, four variable E protein amino acids (E-51, E-209, E-244 and E-366) were identified. Residue positions E-51, E-244 and E-366 are found in peptides with functional T helper cell epitopes in two other flaviviruses. Therefore, these amino acids may be important in defining the various immunotypes of JE virus identified by antibody reactivity patterns.

The oligomerization reaction of the Semliki Forest virus membrane protein subunits

The Semliki Forest virus (SFV) spike is composed of three copies of a membrane protein heterodimer. The two subunits of this heterodimer (p62 and E1) are synthesized sequentially from a common mRNA together with the capsid (C) in the order C-p62-E1. In this work heterodimerization of the spike proteins has been studied in BHK 21 cells. The results indicate that: (a) the polyprotein is cotranslationally cleaved into individual chains; (b) the two membrane protein subunits are initially not associated with each other in the endoplasmic reticulum (ER); (c) heterodimerization occurs predominantly between subunits that originate from the same translation product (heterodimerization in cis); (d) the kinetics of subunit association are very fast (t1/2 = 4 min); and (e) this heterodimerization is highly efficient. To explain the cis-directed heterodimerization reaction we suggest that the p62 protein, which is made before E1 during 26S mRNA translation, is retained at its translocation site until also the E1 chain has been synthesized and translocated at this same site. The mechanism for p62 retention could either be that the p62 anchor sequence cannot diffuse out from an "active" translocation site or that the p62 protein is complexed with a protein folding facilitating machinery that is physically linked to the translocation apparatus.

Characterization of proteins encoded by ORFs 2 to 7 of Lelystad virus

The genome of Lelystad virus (LV), a positive-strand RNA virus, is 15 kb in length and contains 8 open reading frames (ORFs) that encode putative viral proteins. ORFs 2 to 7 were cloned in plasmids downstream of the Sp6 RNA polymerase promoter, and the translation of transcripts generated in vitro yielded proteins that could be immunoprecipitated with porcine anti-LV serum. Synthetic polypeptides of 15 to 17 amino acids were selected from the amino acid sequences of ORFs 2 to 7 and antipeptide sera were raised in rabbits. Antisera that immunoprecipitated the in vitro translation products of ORFs 2 to 5 and 7 were obtained. Sera containing antibodies directed against peptides from ORFs 3 to 7 reacted positively with LV-infected alveolar lung macrophages in the immunoperoxidase monolayer assay. Using these antipeptide sera and porcine anti-LV serum, we identified three structural proteins and assigned their corresponding genes. Virions were found to contain a nucleocapsid protein of 15 kDa (N), an unglycosylated membrane protein of 18 kDa (M), and a glycosylated membrane protein of 25 kDa (E). The N protein is encoded by ORF7, the M protein is encoded by ORF6, and the E protein is encoded by ORF5. The E protein in virus particles contains one or two N-glycans that are resistant to endo-beta-N-acetyl-D-glucosaminidase H. This finding indicates that the high-mannose glycans are processed into complex glycans in the Golgi compartment. The protein composition of the LV virions further confirms that LV is evolutionarily related to equine arteritis virus, simian hemorrhagic fever virus, and lactate dehydrogenase-elevating virus.

Characterization of structural proteins of Lelystad virus

The genome of Lelystad virus (LV), a positive-strand RNA virus, is 15 kb in length and contains 8 open reading frames that encode putative viral proteins. Synthetic polypeptides of 15 to 17 amino acids were selected from the amino acid sequences of ORFs 2 to 7 and anti-peptide sera were raised in rabbits. Using these anti-peptide sera and porcine anti-LV serum, we identified three structural proteins and assigned their corresponding genes. Virions were found to contain a nucleocapsid protein of 15 kDa (N), an unglycosylated membrane protein of 18 kDa (M), and a glycosylated membrane protein of 25 kDa (E). The N protein is encoded by ORF7, the M protein is encoded by ORF6, and the E protein is encoded by ORF5.

Comparison of the structural protein coding sequences of the VR-2332 and Lelystad virus strains of the PRRS virus

The 3'-portion of the genome of a U.S. isolate of the porcine reproductive and respiratory syndrome (PRRS) virus, ATCCVR-2332, was cloned and sequenced. The resultant 3358 nucleotides contain 6 open reading frames (ORFs) with homologies to ORFs 2 through 7 of the European strain of the PRRS virus and other members of the free-standing genus of arteriviruses. Both VR-2332 and the European isolate (called the Lelystad virus) have been identified as infectious agents responsible for the swine disease called PRRS. Comparative sequence analysis indicates that there are degrees of amino acid identity to the Lelystad virus open reading frames ranging from 55% in ORF 5 to 79% in ORF 6. Hydropathy profiles indicate that the ORFs of VR-2332 and Lelystad virus correspond structurally despite significant sequence differences. These results are consistent with the biological similarities but distinct serological properties of North American and European isolates of the virus.

[Cross reactivity and amino acid structural homology of immunodominant peptide fragments of structural viruses from the human retroviruses HTLV-I, HTLV-II, HIV-1, and HIV-2]

Twelve synthetic peptides corresponding to 9 immunodominant regions of structural proteins of human retroviruses HTLV-I, HIV-1, and HIV-2 were studied in enzyme-linked immunosorbent assay for cross reactivity with heterotypical for each peptide anti-retroviral antibodies. The search of amino acid homologies was carried using the special computer program followed by the correspondence analysis of the discovered homologies and immunodominant fragments. It was found that peptides 100-130 p19 gag HTLV-I, 376-392 gp21 env HTLV-I, 381-400 gp21 env HTLV-I, 306-328 gp120 env HIV-1, 495-516 gp120 env HIV-1, 584-612 gp41 env HIV-1, and 581-603 gp36 env HIV-2 have type-specific reactivity and also cross react with 3-54% human sera containing antibodies against heterotypical retroviruses. On the other hand, peptides 120-130 p19 gag HTLV-I, 176-201 gp46 env HTLV-I, 291-312 gp46 env HTLV-I, 330-363 p24 gag HIV-1, and 602-624 gp41 env HIV-1 have shown no cross reactive properties; they may be effectively used for type-specific and differential serodiagnosis of human retroviral infections.

Function of minor polypeptides in foot-and-mouth disease virus and poliovirus

Foot-and-mouth disease virus and poliovirus each contain several minor polypeptides, in addition to the four structural proteins. One of these, the viral RNA polymerase, can also act as a nuclease, hydrolysing the RNA and thus destroying viral infectivity. It is tightly bound to the RNA and may be the packaging signal for assembly of the particle.

Localization of antigenic sites on human cytomegalovirus virion structural proteins encoded by UL48 and UL56

Two human cytomegalovirus (HCMV) virion structural proteins and their associated reading frames have been identified with two human-derived monoclonal antibodies (HMAbs), X2-16 and X-16. HMAb X2-16 identified recombinant protein expressing molecular clones that mapped to the open reading frame (ORF) of the UL48 gene of HCMV, between amino acids 584 and 646 (nucleotides 65,084 and 65,272, Chee et al., 1990, "Current Topics in Microbiology and Immunology," Vol. 154, pp. 125-169). The UL48 gene product has an apparent molecular weight of 216 kDa. HMAb X-16 identified clones derived from the UL56 ORF between amino acids 380 and 425 (nucleotides 84,733 and 84,870). On immunoblots, HMAb X-16 detected two HCMV proteins of 96 and 60 kDa. Both UL48 and UL56 are highly conserved among the human herpesviruses and their products have been predicted to have essential functions for virus production and maturation. These results confirm that UL48 and UL56 are functional genes encoding essential viral proteins which also generate an immune response in the immunocompetent host.

Genes for DNA cytosine methyltransferases and structural proteins, expressed during lytic growth by the phage phi H of the archaebacterium Halobacterium salinarium

Lytic genes and transcription from the Halobacterium salinarium phage phi H were studied. Genes for three structural proteins were located to the left arm of the linear phage genome. The right arm was shown to encode three DNA cytosine methyltransferases, the first such sequences reported from an archaebacterium. One cytosine methyltransferase is of the N(4)-methyltransferase type. The other two open reading frames (ORFs) seem to be parts of the same gene, which has been split by a recombination event. This gene product is of the C5-methyltransferase type. The methyltransferase genes are the first phi H genes detected showing high homology to eubacterial proteins. Five of the six described gene products have a higher proportion acidic over basic amino acid residues, a common characteristic of halobacterial proteins. Lytic phi H transcription was shown to produce three RNA species, two shorter species encoding the methyltransferase genes and one large species transcribed from both the right and the left phage arm and subsequently being processed upstream of the region encoding the structural proteins.

Characterization of the N-terminal part of the neutralizing antigenic site I of coxsackievirus B4 by mutation analysis of antigen chimeras

Coxsackievirus B3 (CVB3) as a potential RNA virus vector for the presentation of foreign antigenic epitopes was further characterized. Insertion mutagenesis of infectious CVB3 cDNA yielded viable antigen chimeras containing variant BC loops of VP1 of coxsackievirus B4 (CVB4). Analysis of three antigen chimeras allowed the mapping of the N-terminal part of the neutralizing antigenic site 1 (N-Ag1) of CVB4 which is located in the BC loop of the structural protein VP1. A significant neutralization of a viable chimera with the deletion of CVB4-specific amino acid Ser-83 at the amino terminus of the VP1 BC loop was obtained with CVB4 serotype-specific polyclonal antisera. This neutralization was reduced after further deletion of the adjacent Ala-84, suggesting that this amino acid either constitutes the beginning of N-Ag1 of CVB4 or is essential for the conformation of the adjacent epitope. In contrast, exchange of amino acid Ser-86 to alanine, in the middle of the BC loop, led to complete loss of reactivity with CVB4-specific antibodies, demonstrating the importance of this residue for binding of CVB4 neutralizing antisera. Furthermore, we observed that manipulations of the VP1 BC loop resulted in increased thermolability of the viable chimeras in comparison to CVB3, although replication efficiencies were similar.

Transcription, translation, and cellular localization of PDV-E66: a structural protein of the PDV envelope of Autographa californica nuclear polyhedrosis virus

A late gene encoding a 66-kDa structural protein of Autographa californica nuclear polyhedrosis virus was mapped and sequenced (26.9-29.7 MU). Transcription initiates from two conserved TAAG motifs (-15 and -37) with transcripts detected from 12 to 72 hr pi. The protein is detected in infected Spodoptera frugiperda (Sf9) cells from 24 to 72 hr pi. Western-blot and immunoelectron microscopic data identify this protein as specific for the polyhedra-derived virus (PDV) envelope. This protein has been named PDV-E66 to identify its viral origin, envelope location, and apparent molecular weight. In addition to being a structural protein of the PDV envelope, PDV-E66 is enriched in foci of microvesicles in the nuclei of infected Sf9 cells.

Detection of the readthrough protein of barley yellow dwarf virus

The single open reading frame (ORF) 5 encoding the 50-kDa protein of barley yellow dwarf virus PAV-IL (BYDV-PAV-IL) was expressed in bacteria, purified, and used as an immunogen/antigen to produce/screen antibodies specific to the 50-kDa protein. Two monoclonal antibodies (MAb PAV-IL-22 kDa and MAb PAV-IL-50 kDa) raised against BYDV-PAV-IL could specifically detect the presence of the 72-kDa readthrough protein in extracts from the BYDV-infected leaf tissue. The results suggest that ORF 5 (50-kDa protein) is translated by readthrough of ORF 3 (22-kDa coat protein) to produce the 72-kDa protein. The readthrough protein is thought to be a structural protein on the external surface of BYDV.

Identification of a vaccinia virus penetration protein

A vaccinia virus structural protein responsible for infection was identified by monoclonal antibodies (mAb). Two mAbs (2D5 and 8C2) neutralized the virus at a dilution of about 10(5). The 2D5 mAb reacted with VP29K under standard immunoblotting conditions and with a 23-kDa protein when virus was dissociated under nonreducing conditions. The 8C2 mAb reacted with the 23-kDa protein, but not with VP29K. Two-dimensional electrophoresis demonstrated that the 23-kDa protein was the nonreduced form of VP29K. Since they possess the same N-terminal amino acid sequence, the protein was renamed VP23-29K. The gene that encoded it was HindIII A17L ORF. The VP23-29K-dependent process of infection did not occur during the adsorption phase at 4 degrees, and trypsin-treated virus could complete the process within 10 min at 37 degrees. One half of the trypsin-treated intracellular mature virus (IMV) achieved the process within 20 min, but for normal IMV this time period was 2 hr. VP23-29K had function for the early step of penetration, and the functional site in the nonreduced 23-kDa form was masked to some extent in normal virus. The late cell fusion by the fusion positive (F+) D1 mutant proceeded in neutral pH. Cells infected with F- IHD-J strain virus did not fuse, but a short treatment with pH 5 medium developed cell fusion. Both of the cell fusions were inhibited by the 2D5 and 8C2 mAbs. Virion VP23-29K was suggested to be the fusion protein for the early penetration and the late cell fusion phases of vaccinia infection cycle.

N-terminal amino acid sequences of vaccinia virus structural proteins

The N-terminal amino acid sequences of vaccinia virus structural proteins were determined by direct sequencing following separation of the proteins of purified intracellular mature virus by SDS-polyacrylamide gels. By comparing the sequences obtained with the published vaccinia virus DNA sequences, specific open reading frames (ORFs) were identified. The structural proteins were encoded by the ORFs of HindIII, A3L (VP57K, 32K), A10L (VP62K, VP28K, VP22K), A12L (VP10K, VP4K), A13L (VP14K), A14L (VP17-25K), A17L (VP23-29K), A27L (VP13.8K), D8L (VP32K), H3L (VP34-37K), L4R (VP27K), G7L (VP16K), and 15L (VP13K). Four virus membrane proteins contained transmembrane signals. The N-termini of proteins indicated four types of cleavages. Ala-Gly-specific cleavage associated with products of six ORFs. Phe-specific cleavage was found in two, Met-specific in three, and Arg-specific in the product of one ORF. Ala-Gly-specific cleavage processes seven core proteins encoded by five ORFs and one membrane protein. The Met- and Arg-specific cleavages are suggested to be nonessential for virus assembly because the major portions of the target membrane proteins remain unaffected.

Molecular comparison of dengue type 1 Mochizuki strain virus and other selected viruses concerning nucleotide and amino acid sequences of genomic RNA: a consideration of viral epidemiology and variation

Dengue-1 (D1) Mochizuki strain was examined for its nucleotide and amino acid sequences of genomic RNA and the data obtained were compared with those of other selected virus strains reported previously. Genomic regions corresponding to C, preM and M proteins were the major subjects of study. Parts of E protein were additionally examined. Among the D1 viruses investigated, the Mochizuki virus which was isolated in 1943 in Japan was shown to be close to Philippine 836-1 strain isolated in 1984 and Nauru Island strain isolated in 1974 at the respective places, in contrast with Thai AHF 82-80 strain isolated in 1980 and Caribbean CV1636/77 strain isolated in 1977. At the same time, a difference was noted between the Mochizuki and Philippine/Nauru strains at the cleavage site of preM/M junction: Mochizuki possessed RRGKR/S sequence whereas the Philippine/Nauru had RRDKR/S. The glycosylation site in preM and hydrophobic regions at the carboxyl termini of M and E were well conserved. Significances of the data are discussed in connection with viral epidemiology and variation.

Comparison of structural proteins among antigenically different Japanese encephalitis virus strains

Based on the reactivities of monoclonal antibodies, we have reported previously that 25 Japanese encephalitis virus (JEV) strains fell into five antigenic groups: Nakayama, Beijing-1, Kamiyama, 691004 and Muar. In the present study, we compared the nucleotide and deduced amino acid sequences of the structural proteins of these strains. Four strains, Nakayama-RFVL, Beijing-1, Kamiyama and 691004, shared > 96.4% identity in the nucleotide sequence and > 94.7% identity in the amino acid sequence. However, the Muar strain had only an 80.3-87.7% homology for nucleotides and an 85.7-93.5% homology for amino acids, compared with the other four strains. The following strain-specific amino acid differences were found in the envelope protein: two in Nakayama-RFVL; three in Beijing-1; one in Kamiyama; five in 691004; 42 in Muar. These findings showed that the Muar strain was the most structurally different from the other four strains, and that it would be possible to compare antigenic differences among the JEV strains by using monoclonal antibodies which showed different specificities.

Identification of GPCMV infected cells in vitro and in vivo with a monoclonal antibody

A monoclonal antibody was made which identifies a 160-180 kDa structural protein in guinea pig cytomegalovirus (GPCMV) infected cells by Western blot using non-reducing conditions. This protein was shown to be a virion structural protein by purification of GPCMV on a density viscosity gradient and Western blot analysis. Phosphoanacetic acid (PAA) experiments suggest that the protein is a late GPCMV protein. In vitro the monoclonal antibody labels a cytoplasmic protein in infected guinea pig embryo fibroblasts by 12 h postinfection. The monoclonal antibody also identifies GPCMV infected cells in vivo in paraffin embedded formalin fixed tissue.

Need for cellular and humoral immune responses in bovines to ensure protection from foot-and-mouth disease virus (FMDV)--a point of view

The published studies on immunization of experimental animals, cattle, and sheep with synthetic peptides containing the antigenic domains in FMDV structural protein VP1 were analyzed. The results obtained with various FMDV synthetic peptides designed to stimulate the humoral immune response in bovines were compared to the current knowledge on MHC class I and class II, and the properties of the peptide binding grooves in each of them. X-ray crystallography of MHC class I proteins provided the three-dimensional structure of the peptide binding groove and led to the isolation and identification of "self" and viral peptides that naturally associate with the peptide binding grooves of both types of MHC and HLA molecules. The available knowledge of the amino acid motifs in MHC and HLA class I-bound viral peptides priming the CD8+ cytotoxic T cell responses must be coupled with the understanding of the three-dimensional structure of BoLA class I. This would aid in the development of an experimental approach to induce bovine anti-FMDV CD8+ cytotoxic cells to complement the humoral immune response to FMDV, which is currently achieved by a killed virus vaccine and, at the experimental level, by a peptide vaccine. Stimulation of both cellular and humoral immune responses against FMDV in cattle may reduce the risk of disease and virus shedding.

Identification and characterization of a novel structural glycoprotein in pseudorabies virus, gL

Herpesvirus envelope glycoproteins play important roles in the interaction between virions and target cells. In the alphaherpesvirus pseudorabies virus (PrV), seven glycoproteins that all constitute homologs of glycoproteins found in herpes simplex virus type 1 (HSV-1) have been characterized, including a homolog of HSV-1 glycoprotein H (gH). Since HSV-1 gH is found associated with another essential glycoprotein, gL, we analyzed whether PrV also encodes a gL homolog. DNA sequence analysis of a corresponding part of the UL region adjacent to the internal inverted repeat in PrV strains Kaplan and Becker revealed the presence of two open reading frames (ORF). Deduced proteins exhibited homology to uracil-DNA glycosylase encoded by HSV-1 ORF UL2 (54% identity) and gL encoded by HSV-1 ORF UL1 (24% identity), respectively. To identify the PrV UL1 protein, rabbit antisera were prepared against two synthetic oligopeptides that were predicted by computer analysis to encompass antigenic epitopes. Sera against both peptides reacted in Western blots of purified virions with a 20-kDa protein. The specificity of the reaction was demonstrated by peptide competition. Since the PrV UL1 sequence did not reveal the presence of a consensus N-linked glycosylation site, concanavalin A affinity chromatography and enzymatic deglycosylation of virion glycoproteins were used to ascertain that the PrV UL1 product is O glycosylated. Therefore, we designated this protein PrV gL. Analysis of mutant PrV virions lacking gH showed that concomitantly with the absence of gH, gL was also missing in purified virions. In summary, we identified and characterized a novel structural PrV glycoprotein, gL, which represents the eighth PrV glycoprotein described. In addition, we show that virion location of PrV gL is dependent on the presence of PrV gH.

Structural proteins of mycobacteriophage I3: cloning, expression and sequence analysis of a gene encoding a 70-kDa structural protein

The structural proteins of mycobacteriophage I3 have been analysed by sodium dodecyl sulfate-polyacrylamide-gel electrophoresis (SDS-PAGE), radioiodination and immunoblotting. Based on their abundance the 34- and 70-kDa bands appeared to represent the major structural proteins. Successful cloning and expression of the 70-kDa protein-encoding gene of phage I3 in Escherichia coli and its complete nucleotide sequence determination have been accomplished. A second (partial) open reading frame following the stop codon for the 70-kDa protein was also identified within the cloned fragment. The deduced amino-acid sequence of the 70-kDa protein and the codon usage patterns indicated the preponderance of codons, as predicted from the high G+C content of the genomic DNA of phage I3.

Partial nucleotide sequence of Japanese encephalitis virus ling strain genome and comparison of the encoded structural proteins and nonstructural protein NS1 among Japanese encephalitis virus strains

Approximately 4000 nucleotides of the 5'-terminal portion of Japanese encephalitis virus (JEV) Ling strain genome were cloned and sequenced. This nucleotide sequence and its encoded C-PrM-E-NS1 polyprotein sequences were also compared with the corresponding sequences of other JE virus strains. Results demonstrated that the nucleotide sequence homology varied from 97.1 to 99.3% and the amino acid homology 98.6 to 98.9%. Based on homology, the Ling strain was closer to the Beijing-1 strain than to the SA14 and JaOArS982 strains. However, only on comparison of the E sequence, which neutralization, hemagglutination-inhibition and complement fixation antigenic determinants are located, between Ling and other JEV strains demonstrated that nucleotide sequence homology varied from 97.1% to 99.3% and amino acid homology from 98.6% to 99.2%. The Ling strain JEV is more closely related to the Beijing-1 strain than to the Nakayama NIH, SA14 and JaOArS982 strains in that order. Based on this analysis, the Taiwanese JEV strain appears to be more closely related to the Chinese strain than to the Japanese strain. Also, JEV strains isolated in humans are more closely related to each other than to JEV strains of mosquito isolates.

Preliminary characterization of the structural proteins of the coronaviruses, sialodacryoadenitis virus and Parker's rat coronavirus

A procedure was developed for the partial purification of the rat coronaviruses, sialodacryoadenitis virus (SDAV) and Parker's rat coronavirus (PRC). The SDAV and PRC were replicated in L-2 cell monolayer cultures, precipitated with ammonium sulphate, and further concentrated using sucrose density gradient centrifugation. The major SDAV and PRC proteins were identified by immunoblotting and compared with those of the JHM strain of mouse hepatitis virus (MHV-JHM). Monoclonal antibodies (MAb) against the M protein of JHM recognized proteins interpreted to be slightly smaller in immunoblots of SDAV and PRC (22.8 vs 23K for JHM). Similarly, a monoclonal antibody against the JHM N protein reacted with proteins of 53K in SDAV and PRC (vs 56 K for JHM). Polyclonal antisera to all three viruses also cross-reacted with the M and N proteins. Some cross-reactivity amongst the S proteins was observed. Based on these data, the structural proteins of the rat coronaviruses, SDAV and PRC are closely related to those of MHV-JHM.

Nucleotide sequence and genetic organization of a 7.3 kb region (map unit 47 to 52.5) of Autographa californica nuclear polyhedrosis virus fragment EcoRI-C

The nucleotide sequence and genetic organization of a 7297 bp region within the EcoRI-C fragment of Autographa californica multiple nucleocapsid nuclear polyhedrosis virus (AcMNPV) are presented. Eight putative open reading frames were found and their respective amino acid sequences compared with a number of data libraries. ORF 1227 corresponded with gp41 and its predicted protein sequence was found to be 55 amino acids longer at its C terminus than reported previously. Moreover the main part of the ORF 1227 product, including the additional 55 amino acids, showed a high degree of homology with protein p40 of Helicoverpa zea single nucleocapsid nuclear polyhedrosis virus (HzSNPV). Three other ORFs in the analysed AcMNPV region showed homology with ORFs in the HzSNPV sequence, indicating that the general organization of this region is similar in both viruses. However one ORF found in the AcMNPV sequence was absent from the corresponding HzSNPV sequence.

Molecular basis of antigenic variation in infectious bursal disease virus

Four antigenically different strains of infectious bursal disease virus (IBDV), characterized by their reactivities with a panel of neutralizing monoclonal antibodies (MAbs), were selected to determine the molecular basis of antigenic variation. The large genome segment A, encoding the structural proteins of the U.S. variants GLS, DS326, E/Del and the vaccine strain D78, was cloned and sequenced. Comparison of the deduced amino acid sequences of the U.S. variants with other IBDV strains showed that most of the amino acid substitutions occur in the central region between residues 212 to 332, especially in the two hydrophilic regions between residues 212 to 223 and residues 314 to 324 of VP2 protein. By comparing the amino acid sequences of these variant viruses and their reactivities with IBDV specific MAbs, the putative amino acids involved in the formation of virus-neutralizing epitopes were identified. Comparison of the D78 versus PBG98 sequence showed that Gln at position 249 (Gln249) appears to be critical in binding with MAb B69. Similarly, comparison of the U.S. variant sequences with other serotype 1 sequences showed unique substitution(s) at residue Glu321 in GLS, residues Ile286, Asp318, Glu323 in E/Del, and residues Glu311 and Gln320 in DS326, which could be potential residue(s) involved in the recognition of MAb57, MAb67, and MAb179 epitopes, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunogens of rotaviruses

Rotaviruses cause gastroenteritis in neonates of many animal species including cattle, swine, horses, dogs, cats, chickens and turkeys. Rotavirions are nonenveloped, are about 75 nm in diameter, have a double capsid, and contain 11 double-stranded RNA segments as their genome. Several antigenically distinct groups of rotaviruses have been identified and have been alphabetically designated as A through G. Group A rotaviruses were the first group of rotaviruses isolated and are the most commonly detected rotaviruses in diarrheic animals. Group A rotaviruses have two surface proteins, VP4 and VP7, both of which are important in serotype determination and in inducing neutralizing antibodies and protective immunity. Multiple serotypes of group A rotavirus based on glycoprotein VP7 (designated as G types) and based on VP4 (P types) have been identified. The immune response to rotaviruses is essentially serotype specific, however, cross-reactive or heterotypic epitopes have also been identified. Currently acceptable methods for immunogen quantitation include the induction of neutralizing antibody in host or laboratory animals. The in vivo efficacy of vaccines against rotavirus-associated gastroenteritis remains the standard method against which in vitro methods must be compared. Several animal models have been developed which could potentially be used in evaluating the efficacy of candidate vaccines. Monoclonal antibodies to rotavirus immunogens are also currently available and serve as valuable reagents for in vitro quantitation of rotaviral immunogens.

Characterization of structural and non-structural proteins of hog cholera virus by means of monoclonal antibodies

A panel of 15 monoclonal antibodies, produced against the hog cholera virus, were characterized by radioimmunoprecipitation assays. Using this panel, we were able to identify 4 sets of monoclonal antibodies precipitating each a different viral protein with relative molecular weight of 40, 46, 120 kDa, respectively, and a protein complex containing 15, 16, 27, and 55 kDa polypeptides which were further characterized. One monoclonal antibody recognized an antigenic determinant at the C-terminal cleavage product of the non-structural p 125 of BVDV. The 40 kDa protein was precipitated from the pelleted virions, indicating its structural importance. On the contrary the 46 kDa protein could only be precipitated from the cell lysate and not from the pelleted virions. The glycosylated 15/16 kDa-55 kDa proteins form a disulfide linked heterodimer on the virus particle with a relative molecular weight of 65 kDa.

Cysteine conformation and sulfhydryl interactions in proteins and viruses. 3. Quantitative measurement of the Raman S-H band intensity and frequency

The bond stretching vibration of the cysteine sulfhydryl (SH) group in a typical protein generates a Raman band in the spectral interval 2500-2600 cm-1, a region devoid of interference from any other fundamental mode of vibration of the protein. The relatively high Raman cross section associated with the S-H stretching vibration, the sensitivity of the vibrational frequency to hydrogen bonding interactions and side chain configurations, and the dependence of the Raman intensity on thiol-thiolate equilibria, combine to make the Raman SH band a potentially valuable marker of protein sulfhydryl interactions and a unique indicator of sulfhydryl participation in thiol-disulfide oxidoreductase activity. In order to exploit Raman spectroscopy for these purposes, accurate and precise measurements of Raman SH band profiles are required. We show here that the required precision and accuracy can be achieved by use of the Raman band corresponding to the stretching vibration of in situ nitrogen gas as a quantitative intensity and frequency standard. The Raman Q-branch center of the N2 band occurs at 2330.7 cm-1.

Identification of a structural glycoprotein of an RNA virus as a ribonuclease

One of the three structural glycoproteins of classical swine fever virus (CSFV) is E0, a disulfide-bonded homodimer that induces virus-neutralizing antibodies and occurs in a virion-bound as well as a secreted form. E0 was shown to be similar to a family of fungal and plant ribonucleases. Purified E0 from CSFV-infected cells was a potent ribonuclease specific for uridine and inhibitable by zinc ions.

Cottontail rabbit papillomavirus L1 protein-based vaccines: protection is achieved only with a full-length, nondenatured product

Papillomas induced by the cottontail rabbit papillomavirus (CRPV) progress at a high frequency to carcinomas. In this regard, CRPV and its tumors can serve as an animal model for highly oncogenic human papillomaviruses. We have previously shown that immunization with major structural protein L1 elicits neutralizing antibodies and protects rabbits from papilloma development (Y.-L. Lin, L.A. Borenstein, R. Selvakumar, R. Ahmed, and F.O. Wettstein, Virology 187:612-619, 1992). In this study, we demonstrated that vaccination with the TrpE-L1 fusion protein not only protected rabbits from papilloma development but also prevented latent infection. This was indicated by the failure to amplify CRPV sequences by polymerase chain reaction in biopsies from infection sites of immunized animals. Furthermore, we showed that TrpE-L1 immunization protected rabbits from papilloma formation induced by virus but not from that induced by viral DNA. To explore the possibility of developing vaccines based on L1 subfragments, we mapped the linear L1 epitopes recognized by TrpE-L1-immunized rabbits and by virus-infected rabbits resistant to superinfection. Sera from papilloma-bearing rabbits reacted with one major epitope located at the carboxy-terminal end of L1, between amino acids (aa) 480 and 505. A second epitope, and in some animals a third one, was located in the amino-terminal region, between aa 78 and 101, as well as between aa 37 and 62. Sera from TrpE-L1-immunized animals recognized only one major epitope, located between aa 6 and 37. Immunization of rabbits with L1 subfragment fusion proteins led to seroconversion, but no neutralizing antibodies were produced and the animals were not protected against papilloma formation. The data indicate that a successful papillomavirus vaccine must be based on immunization with full-length native L1 and that further simplification to smaller peptides containing major linear epitopes is not feasible.

Dissociation of the lipid-containing bacteriophage PRD1: effects of heat, pH, and sodium dodecyl sulfate

The double-stranded DNA bacteriophage PRD1 replicates in Escherichia coli and Salmonella typhimurium. It has an outer protein coat surrounding a membrane. The phage lipids are derived from the host, but the membrane proteins are of phage origin. In this investigation we studied the effects of heat, pH, and sodium dodecyl sulfate on the integrity of phage particles. Heat and high pH result in the release of the main coat protein, P3, as trimers, whereas treatment of phage particles with detergent results in the solubilization of the membrane. Our results enable a distinction to be made between the phage structural proteins that are embedded in the lipid bilayer and those that appear to be more loosely associated with the membrane.

Nucleotide sequence analysis of the serotype-specific epitope of infectious pancreatic necrosis virus

The cDNA nucleotide sequences of the infectious pancreatic necrosis virus (IPNV) serotype-specific epitope of the major structural protein VP 2 were determined for a Scottish strain (Sp serotype), and an IPNV field isolate from Shetland. Comparison of the sequence data indicated that the field isolate was of the Sp serotype. The Scottish Sp strain and the field isolate showed less than 3% difference in nucleotide sequence over this region compared to the Norwegian N 1 strain, and all three European viruses differed by approximately 23% from the Canadian Jasper strain.

Suppression of tuftsin activity by the partial sequences of adenovirus type 2 proteins

The synthesis of tuftsin inhibitor-like partial sequences of adenovirus type 2 proteins: TVPPR (1), TRPPR (2), TGPPT (3), PRPPT (4), FVPPR (5), ARPPA (6) and YGPPK (7) are described. The choice of peptides for synthesis was performed by using a simple computer-aided method for predicting antigenic determinants of proteins. For all these peptides an inhibitory activity against tuftsin was found.

Mapping cell-mediated immunodominant domains of the rubella virus structural proteins using recombinant proteins and synthetic peptides

Although it is known that rubella-immune individuals have T cells that proliferate in vitro in response to rubella virus (RV), the determinants that evoke this response have not been identified. This study utilized recombinant proteins that express overlapping sequences of the RV structural open reading frame to identify domains of the structural proteins that contain cell-mediated immunodominant sequences. Lysates enriched with RV fusion proteins (RecA-RV-LacZ) were prepared from Escherichia coli transformed with plasmids which contained specific RV cDNA inserts. Approximately 62% of RV-immune individuals gave RV-specific responses to one or more of the RV fusion proteins. Over 10% of immune individuals recognized the capsid sequence C1-C29. Lymphoproliferation data from studies using six overlapping synthetic peptides representing this sequence suggested that as much as 70% of the immune population may recognize this domain. An E1 sequence, E1(202)-E1(283), was recognized by 15% of the RV-immune individuals with the fusion proteins. Five synthetic peptides representing this sequence had an overall response rate of 50%. The sequence C64-C97 failed to evoke any RV-specific responses with the fusion proteins and synthetic peptides representing this sequence were used to verify that the RV fusion proteins and the criteria used to identify RV-specific responses were adequate. These peptides gave a response rate of only 6%. In general, significant responses to specific fusion proteins correlated with high responses (stimulation index > or = 4.0) to representative synthetic peptides. This study suggests that the recombinant proteins were beneficial in identifying cell-mediated immunodominant domains of the RV structural proteins which could be further characterized with synthetic peptides.

Comparison of the nucleotide and deduced amino acid sequences of the structural protein genes of the yellow fever 17DD vaccine strain from Senegal with those of other yellow fever vaccine viruses

The nucleic acid and deduced amino acid sequences of the structural proteins of the 17DD vaccine strain of yellow fever (YF) virus originating from Senegal are compared with those published for other vaccine strains of YF virus. Even though the 17D-204 and 17DD substrains of 17D diverged at passage 195 of 17D, they show a very high degree of nucleotide (99.5%) and amino acid (99.5%) homology over this region. The sequences are discussed with respect to monoclonal antibodies that can distinguish between 17DD and 17D-204 substrains of YF vaccines.

Terminating a macromolecular helix. Structural model for the minor proteins of bacteriophage M13

Analysis of the results of X-ray diffraction, electron microscopy and s sequence studies of filamentous bacteriophage M13 are used to construct structural models for the minor proteins gp7 and gp9 at the end of the virus assembled first, and a portion of gp6 at the end of the virus that binds host. Comparison of the sequence of the major coat protein, gp8, with those of gp7, gp9 and gp6 indicates that significant portions of these three proteins have sequences similar to that of gp8. Assuming that sequence similarity is indicative of structural similarity, gp7, gp9 and portions of gp6 are modeled based on what is known about the structure of gp8. These molecular models are analyzed to predict the packing of the minor proteins with the terminal gp8 proteins (the last gp8 proteins at either end of the helix). This analysis indicates that the gp8 proteins integrated into the virus first may have a structure distinct from those in the body of the virus particle. The gp8 proteins at the end assembled last appear to have a conformation very similar to that of the integral coat proteins. These models place specific constraints on models for the process of viral assembly.

Structural proteins of equine arteritis virus

We have recently shown that the genome of equine arteritis virus (EAV) contains seven open reading frames (ORFs). We now present data on the structural proteins of EAV and the assignment of their respective genes. Virions are composed of a 14-kDa nucleocapsid protein (N) and three membrane proteins designated M, GS, and GL. M is an unglycosylated protein of 16 kDa, and GS and GL are N-glycosylated proteins of 25 and 30 to 42 kDa, respectively. The broad size distribution of GL results from heterogeneous N-acetyllactosamine addition since it is susceptible to digestion by endo-beta-galactosidase. Using monospecific antisera as well as an antivirion serum, and by expression of individual ORFs, the genes for the structural proteins were identified: ORF 7 codes for N, ORF 6 for M, ORF 5 for GL, and ORF 2 for GS. With the exception of GS, the proteins are about equally abundant in EAV virions, being present at a molar ratio of 3 (N):2 (M):3 (GL). The GS protein, which is expressed at a level similar to that of M in infected cells, is strikingly underrepresented in virus particles (1 to 2%). Our data justify a distinct taxonomic position for EAV, together with lactate dehydrogenase-elevating virus and simian hemorrhagic fever virus; although coronavirus- and toroviruslike in features of transcription and translation, the virion architecture of EAV is fundamentally different.

Structural proteins of classic and variant strains of infectious bursal disease viruses

Structural polypeptides of six tissue-culture-origin (BGM-70 continuous cell line) infectious bursal disease viruses representing classic and variant strains of serotype 1 and one serotype 2 strain were analyzed and compared by sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Additionally, two of the variant strains were propagated in vivo in bursa of Fabricius and compared with those grown in cell culture. Differences among the structural proteins of serotype 1 viruses were minor and probably of no value in differentiating these viruses. However, distinct differences were observed between serotype 1 and 2 viruses. The bursa-derived viruses were different from those propagated in cell culture in molecular weights and in proportions of the proteins. The bursa-derived strains had protein migration patterns similar to those described for tissue-culture-incomplete virus particles.

Association between hepatitis C virus and hepatocellular carcinoma using assays based on structural and nonstructural hepatitis C virus peptides

Stored sera from 181 Greek patients with hepatocellular carcinoma (HCC), 35 patients with metastatic liver cancer, and 416 hospital controls with diagnoses other than malignant neoplasm or liver disease were examined with first and second generation hepatitis C virus (HCV) enzyme immunoassays as well as with five HCV supplemental assays based on structural and nonstructural HCV peptides. Second generation HCV enzyme immunoassays were more sensitive than first generation assays. However, both assays had suboptimal specificity using the standard reactivity criterion (absorbance of sample to cutoff greater than or equal to 1.0). Specificity was improved by centrifugation and by using a sample's optical density to cutoff ratio greater than or equal to 3.0 or supplemental assays; in this instance the prevalence of antibodies to HCV was 13.3% (24 of 181), 0 (0 of 35), and 1.4% (6 of 416) in HCC, metastatic liver cancer, and hospital controls, respectively. A similar estimation of prevalence of antibody to HCV in HCC (12.5% or 4 of 32) was obtained when the recombinant immunoblot assay, second generation, was used to screen a random sample of HCC patients. The relative risk linking HCV to HCC was estimated as 10.4 (95% confidence interval, 4.2-26.0; P less than 0.0001). These data suggest that the prevalence of antibodies to HCV in HCC using stored sera has been previously overestimated even though the evidence of a causal association of HCV with HCC persists.

Demonstration of low molecular weight polypeptides associated with small, round-structured viruses by western immunoblot analysis

Small, round-structured viruses (SRSV) were detected in 14 of 300 fecal specimens obtained from patients with acute gastroenteritis by electron microscopy. These SRSV strains were morphologically indistinguishable from one another. While 11 of these strains had a single usual major structural protein with molecular weight of 63,000 (63K) daltons (p63), interestingly, three strains possessed a single major structural protein with molecular weight of 33K daltons (p33). Treatments of p63-SRSV with proteolytic enzymes or denaturating reagents did not affect the molecular weight of p63, and the p33 was not detectable by Western immunoblot in the ultracentrifugal supernatant of the p63-SRSV suspension. These results suggest that the p33 is neither a definitive subunit of p63 nor disintegrated component derived from the p63-SRSV but a novel polypeptide of SRSV. Immune electron microscopy and Western immunoblot analyses indicated that p63- and p33-SRSVs may share an antigenic determinant(s).

Genetic evolution and tropism of transmissible gastroenteritis coronaviruses

Transmissible gastroenteritis virus (TGEV) is an enteropathogenic coronavirus isolated for the first time in 1946. Nonenteropathogenic porcine respiratory coronaviruses (PRCVs) have been derived from TGEV. The genetic relationship among six European PRCVs and five coronaviruses of the TGEV antigenic cluster has been determined based on their RNA sequences. The S protein of six PRCVs have an identical deletion of 224 amino acids starting at position 21. The deleted area includes the antigenic sites C and B of TGEV S glycoprotein. Interestingly, two viruses (NEB72 and TOY56) with respiratory tropism have S proteins with a size similar to the enteric viruses. NEB72 and TOY56 viruses have in the S protein 2 and 15 specific amino acid differences with the enteric viruses. Four of the residues changed (aa 219 of NEB72 isolate and aa 92, 94, and 218 of TOY56) are located within the deletion present in the PRCVs and may be involved in the receptor binding site (RBS) conferring enteric tropism to TGEVs. A second RBS used by the virus to infect ST cells might be located in a conserved area between sites A and D of the S glycoprotein, since monoclonal antibodies specific for these sites inhibit the binding of the virus to ST cells. An evolutionary tree relating 13 enteric and respiratory isolates has been proposed. According to this tree, a main virus lineage evolved from a recent progenitor virus which was circulating around 1941. From this, secondary lineages originated PUR46, NEB72, TOY56, MIL65, BR170, and the PRCVs, in this order. Least squares estimation of the origin of TGEV-related coronaviruses showed a significant constancy in the fixation of mutations with time, that is, the existence of a well-defined molecular clock. A mutation fixation rate of 7 +/- 2 x 10(-4) nucleotide substitutions per site and per year was calculated for TGEV-related viruses. This rate falls in the range reported for other RNA viruses. Point mutations and probably recombination events have occurred during TGEV evolution.

Differential detection of infectious bursal disease virus serotypes, using cDNA probes to VP2 coding region

Two nonoverlapping clones, pOH405 and pOH632, containing cDNA inserts in the VP2 coding region of genome segment A were selected from a cDNA library prepared from the double-stranded RNA genome of the OH strain of infectious bursal disease virus (IBDV) of serotype 2. Clone pOH405, which is located in the hypervariable segment of VP2, is 328 base pairs long, has nucleotide sequence homology of 72 to 73%, and amino acid sequence homology of 64 to 67% with IBDV strains of serotype 1. Clone pOH632, which is located in the highly conserved C-terminal part of VP2, is 230 base pairs long, has nucleotide sequence homology of 87 to 88%, and amino acid sequence homology of 100% with IBDV serotype 1. The lower detection limit of 32P-labeled probes prepared from both clones was 10 ng of OH-IBDV double-stranded RNA, using high-stringency conditions of hybridization (54 C, 50% formamide) and washing (55 C, 0.015M NaCl, 0.0015M trisodium citrate, pH 7.0, with 0.1% sodium dodecyl sulfate), and autoradiography for 24 hours. Under these conditions, the dot-blot hybridization assay for detection of serotype 2 IBDV double-stranded RNA, was 1,000 times more sensitive, using probe pOH632, but only 10 times more sensitive, using probe pOH405, compared with the assay for IBDV serotype 1, using the same probes. Thus, probe pOH632 could differentiate between the 2 IBDV serotypes by nucleic acid hybridization.

Microheterogeneity of S-glycoprotein of mouse hepatitis virus temperature-sensitive mutants

Mouse hepatitis virus (MHV) strain JHM (MHV-JHM) is a neurotropic coronavirus that causes acute fatal encephalomyelitis in 75-99% of infected mice. The surviving animals may subsequently develop demyelinating disease. We compared the S peplomer protein of the wild type (wt) and five temperature-sensitive (ts) mutants of MHV-JHM. In contrast with the wt, none of these five cause fatal disease (mortality less than 10%). Three of these ts mutants did not induce any demyelinating disease, a fourth caused demyelinating disease in 5% of the animals and a fifth, designated ts8, exhibited strong demyelinating properties and caused demyelination in 99% of the animals. SDS-PAGE analysis revealed no differences in the molecular weight of S peplomer protein of wt or ts MHV-JHM mutants. However, isoelectric focusing of the S protein of these five ts mutants and the wt MHV-JHM, followed by transfer to nitrocellulose sheets and immunoblotting with anti-S specific antibody revealed significant differences in the microheterogeneity of the S protein.