Midgut and salivary gland transcriptomes of the arbovirus vector Culicoides sonorensis (Diptera: Ceratopogonidae)

Numerous Culicoides spp. are important vectors of livestock or human disease pathogens. Transcriptome information from midguts and salivary glands of adult female Culicoides sonorensis provides new insight into vector biology. Of 1719 expressed sequence tags (ESTs) from adult serum-fed female midguts harvested within 5 h of feeding, twenty-eight clusters of serine proteases were derived. Four clusters encode putative iron binding proteins (FER1, FERL, PXDL1, PXDL2), and two clusters encode metalloendopeptidases (MDP6C, MDP6D) that probably function in bloodmeal catabolism. In addition, a diverse variety of housekeeping cDNAs were identified. Selected midgut protease transcripts were analysed by quantitative real-time PCR (q-PCR): TRY1_115 and MDP6C mRNAs were induced in adult female midguts upon feeding, whereas TRY1_156 and CHYM1 were abundant in midguts both before and immediately after feeding. Of 708 salivary gland ESTs analysed, clusters representing two new classes of protein families were identified: a new class of D7 proteins and a new class of Kunitz-type protease inhibitors. Additional cDNAs representing putative immunomodulatory proteins were also identified: 5' nucleotidases, antigen 5-related proteins, a hyaluronidase, a platelet-activating factor acetylhydrolase, mucins and several immune response cDNAs. Analysis by q-PCR showed that all D7 and Kunitz domain transcripts tested were highly enriched in female heads compared with other tissues and were generally absent from males. The mRNAs of two additional protease inhibitors, TFPI1 and TFPI2, were detected in salivary glands of paraffin-embedded females by in situ hybridization.

Molecular investigations of orbivirus/vector interactions

Defining predictors for insect-transmitted virus (arbovirus) disease cycles requires an understanding of the molecular interactions between the virus and vector insect. Studies of orbiviruses from numerous geographic regions have indicated that virus genes are affected by insect population differences. Therefore, the authors have initiated genetic studies of Culicoides sonorensis, isolating cDNAs for characterisation of differential insect gene expression, as well as a gene discovery project. Previous work identified insect transcripts elevated in orbivirus-infected female midguts at one day post infection (pI). Here, we report cDNAs that were more abundant in midguts two days following an epizootic haemorrhagic disease virus feeding, as well in head/salivary glands at three days pI. Of the cDNAs identified in midguts at two days pI, three encode translational machinery components, and three encode components that affect cellular structural features. Of the differentially expressed salivary gland cDNAs, only one was homologous to a previously identified gene, a putative odorant binding protein.

Quantifying viral propagation in vitro: toward a method for characterization of complex phenotypes

For a eukaryotic virus to successfully infect and propagate in cultured cells several events must occur: the virion must identify and bind to its cellular receptor, become internalized, uncoat, synthesize viral proteins, replicate its genome, assemble progeny virions, and exit the host cell. While these events are taking place, intrinsic host defenses activate in order to defeat the virus, e.g., activation of the interferon system, induction of apoptosis, and attempted elicitation of immune responses via chemokine and cytokine production. As a first step in developing an imaging methodology to facilitate direct observation of such complex host/virus dynamics, we have designed an immunofluorescence-based system that extends the traditional plaque assay, permitting simultaneous quantification of the rate of viral spread, as indicated by the presence of a labeled viral protein, and cell death in vitro, as indicated by cell loss. We propose that our propagation and cell death profiles serve as phenotypic read-outs, complementing genetic analysis of viral strains. As our virus/host system we used vesicular stomatitis virus (VSV) propagating in hamster kidney epithelial (BHK-21) and murine astrocytoma (DBT) cell lines. Viral propagation and death profiles were strikingly different in these two cell lines, displaying both very different initial titer and cell age effects. The rate of viral spread and cell death tracked reliably in both cell lines. In BHK-21 cells, the rate of viral propagation, as well as maximal spread, was relatively insensitive to initial titer and was roughly linear over several days. In contrast, viral plaque expansion in DBT cells was contained early in the infections with high titers, while low titer infections spread in a manner similar to the BHK-21 cells. The effect of cell age on infection spread was negligible in BHK-21 cells but not in DBTs. Neither of these effects was clearly observed by plaque assay.

Homologous and heterologous interference requires bovine herpesvirus-1 glycoprotein D at the cell surface during virus entry

Expression of glycoprotein D (gD) of alphaherpesviruses protects cells from superinfection by homologous and heterologous viruses by a mechanism termed interference. We recently showed that MDBK cells expressing bovine herpesvirus (BHV)-1gD (MDBK(gD)) resist BHV-1, pseudorabies virus (PRV) and herpes simplex virus-1 (HSV-1) but not the more closely related BHV-5 infection as determined by the number of plaques produced. However, the plaque size is reduced in all four viral infections suggesting a block in cell-to-cell transmission. Here, we show that MDBK cells expressing truncated BHV-1 gD, designated MDBK(t-gD), secreted soluble gD and were fully susceptible to infection by all the four viruses when the cells were washed prior to infection. When MDBK cells or MDBK(t-gD) cells were treated with medium containing truncated gD prior to infection, they partially resisted BHV-1, PRV and HSV-1 but not BHV-5. Interestingly, both BHV-1 and BHV-5 formed normal-sized plaques in MDBK(t-gD) cells suggesting that the viruses were able to spread efficiently. Thus BHV-1 gD is required at the cell surface at the time of infection in order to block BHV-1, HSV-1 and PRV infections, consistent with a common coreceptor for the three gDs.

Bovine herpesvirus 1 U(L)3.5 interacts with bovine herpesvirus 1 alpha-transinducing factor

The bovine herpesvirus 1 (BHV-1) U(L)3.5 gene encodes a 126-amino-acid tegument protein. Homologs of U(L)3.5 are present in some alphaherpesviruses and have 20 to 30% overall amino acid homology that is concentrated in the N-terminal 50 amino acids. Mutant pseudorabies virus lacking U(L)3.5 is deficient in viral egress but can be complemented by BHV-1 U(L)3.5 (W. Fuchs, H. Granzow, and T. C. Mettenleiter, J. Virol. 71:8886-8892, 1997). The function of BHV-1 U(L)3.5 in BHV-1 replication is not known. To get a better understanding of its function, we sought to identify the proteins that interact with the BHV-1 U(L)3.5 protein. By using an in vitro pull-down assay and matrix-assisted laser desorption ionization mass spectrometry analysis, we identified BHV-1 alpha-transinducing factor (alphaBTIF) as a BHV-1 U(L)3. 5-interacting protein. The interaction was verified by coimmunoprecipitation from virus-infected cells using an antibody to either protein, by indirect immunofluorescence colocalization in both virus-infected and transfected cells, and by the binding of in vitro-translated proteins. In virus-infected cells, U(L)3.5 and alphaBTIF colocalized in a Golgi-like subcellular compartment late in infection. In transfected cells, they colocalized in the nucleus. Deletion of 20 amino acids from the N terminus of U(L)3.5, but not 40 amino acids from the C terminus, abolished the U(L)3.5-alphaBTIF interaction both in vitro and in vivo. The interaction between U(L)3. 5 and alphaBTIF may be important for BHV-1 maturation and regulation of alphaBTIF transactivation activity.

Bovine herpesvirus type 2 is closely related to the primate alphaherpesviruses

Bovine herpesvirus type 2 (BoHV-2), also known as bovine mammillitis virus, is classified in the Family Herpesviridae, Subfamily Alphaherpesvirinae, and Genus Simplexvirus along with herpes simplex viruses type 1 and 2 (HSV-1 and HSV-2) and other primate simplexviruses on the basis of similarities in 4 genes within the 15 kb U(L) 23-29 cluster. This could be explained either by a global similarity or a recombination event that brought primate herpesviral sequences into a bovine virus. Our sequences for DNA polymerase (U(L)30), a large gene adjacent to the previously identified conserved cluster, and glycoprotein G (U(S)4), a gene as distant from the cluster as possible on the circularized genome, confirm the close relationship between BoHV-2 and the primate simplexviruses, and argue for a global similarity and probably a close evolutionary relationship. Thus one can speculate that BoHV-2 may represent a greater hazard to humans than has been appreciated previously.

Vesicular stomatitis

Vesicular stomatitis is a disease of livestock caused by some members of the Vesiculovirus genus (Family Rhabdoviridae), two of which are called 'vesicular stomatitis virus'. Clinical disease presents as severe vesiculation and/or ulceration of the tongue, oral tissues, feet, and teats, and results in substantial loss of productivity. Except for its appearance in horses, it is clinically indistinguishable from foot-and-mouth disease. Unlike foot-and-mouth disease, it is very infectious for man and can cause a temporarily debilitating disease. Vesicular stomatitis occurs seasonally every year in the southeastern USA, southern Mexico, throughout Central America and in northern South America, and emerges from tropical areas to cause sporadic epidemics in cooler climates during the summer months. Other Vesiculoviruses are endemic in India and Africa. Vesiculoviruses are arthropod-borne and it is possible they are actually well adapted insect viruses that incidentally infect mammals. Vesiculoviruses are relatively simple, having a linear, single stranded, negative sense RNA genome encased in a bullet-shaped virion made from only five proteins. Upon infection of cultured cells, viral products turn off cellular gene expression and seize the entire metabolic potential of the cell. They also depolymerize the cytoskeleton to cause rapid tissue destruction. Virus infection in animals provokes interferon and nitric oxide responses, which quickly control viral replication, and an antibody response that prevents further viral replication. Vesiculovirus genome replication is error-prone, resulting in viral progeny containing many variants. This allows rapid adaptation. Nevertheless, vesicular stomatitis virus genomic sequences appear relatively stable within single endemic areas, and vary progressively on a North-South axis in the Western Hemisphere. Numerous important fundamental discoveries in immunology and virology have come from recent studies of vesicular stomatitis virus. However, these discoveries have not led to a safe and fully effective vaccine for man or beast. In the absence of a vaccine, the continual increase in rapid intercontinental travel, the increase in numbers and concentration of susceptible animals, the plasticity of the viral genome, and the underappreciation of vesiculoviruses as veterinary and zoonotic pathogens by regulators and biomedical researchers, are combining with potentially explosive consequences.

Cellular expression of bovine herpesvirus 1 gD inhibits cell-to-cell spread of two closely related viruses without blocking their primary infection

Alphaherpesviral glycoprotein D (gD) is a critical component of the cell membrane penetration system. Cells that express gD of herpes simplex virus type 1 (HSV1), pseudorabies virus (PRV), or bovine herpesvirus type 1.1 (BHV1.1) resist infection by the homologous virus due to interference with viral entry at the level of penetration. BHV1.1 gD interferes with the distantly related viruses HSV1 and PRV despite only a 30-40% sequence similarity and the complete absence of antigenic cross-reactivity among the three gDs. The six cysteines that form three intrachain disulfide bonds in HSV1 are also present in PRV and BHV1.1 gD, suggesting structural similarities among the gD homologs. Functional similarities were postulated to be responsible for cross-interference. To test this hypothesis, we constructed a BHV1.1 gD-expressing cell line (MDBKgD) and assessed its resistance to the homologous BHV1.1 and two closely related viruses, BHV1.2 and BHV5. The gDs of these viruses share 98. 3% and 86% amino acid identity with BHV1.1 gD and bound monoclonal antibodies directed against all five neutralizing epitopes mapped on BHV1.1 gD. MDBKgD cells were resistant to BHV1.1 but fully susceptible to BHV1.2 and BHV5 infection as measured by plaque numbers and single cycle growth kinetics. However, all three viruses, but not vesicular stomatitis virus, made smaller plaques on MDBKgD cells than on control cells. These data suggest that gD-mediated interference is expressed both at the level of initial infection and at the level of cell-to-cell spread and that these two levels can be distinguished by using closely related viruses.

A chimeric protein comprised of bovine herpesvirus type 1 glycoprotein D and bovine interleukin-6 is secreted by yeast and possesses biological activities of both molecules

Bovine herpesvirus type 1 (BHV-1) glycoprotein D (gD) engenders mucosal and systemic immunity and protects cattle from viral infection. Chimerization of cytokines with gD is being explored to confer intrinsic adjuvanticity on gD. Addition of the appropriate cytokine may convert gD into an antigen that specifically engenders protective mucosal immunity. Here DNA coding for the mature bovine interleukin-6 (IL-6) protein was fused through a synthetic glycine linker to the 3' end of DNA coding for the mature BHV-1 gD (tgD) external domain. It was cloned behind the yeast alpha prepro signal sequence and transfected into Pichia pastoris which secreted the chimeric protein (tgD-IL-6) as a 100 kDa molecule. This chimera combined the immunogenic properties of native gD and the in vitro biological activity of bovine IL-6 based on the following observations. A panel of BHV-1 gD-specific monoclonal antibodies recognizing five neutralizing epitopes on native gD reacted with tgD-IL-6. Sera from yeast tgD-IL-6-immunized mice neutralized BHV-1 infection in vitro. The chimeric protein enhanced total bovine immunoglobulin production 16-fold above tgD alone in pokeweed-stimulated bovine peripheral blood mononuclear cells (P < 0.05). This chimeric protein may be a potent mucosal immunogen.

Sequence, transcriptional analysis, and deletion of the bovine adenovirus type 1 E3 region

The early 3 (E3) transcriptional unit of human adenoviruses (HAV) encodes proteins that modulate host antiviral immune defenses. HAV E3 sequences are highly variable; different HAV groups encode phylogenetically unrelated proteins. The role of the E3 region of many human and animal adenoviruses is unknown because the sequences are unrelated to previously characterized viruses and the functions of proteins encoded by these regions have not been studied. We sequenced a portion of the bovine adenovirus serotype 1 (BAV-1) genome corresponding to the putative E3 region. This sequence was substantially different from other adenoviral E3 sequences, including those of two other bovine adenoviruses. However, two regions of putative sequence conservation were identified. BAV-1 E3 sequences were identified in early and late transcripts, but, unlike HAV, introns were not detected in the E3 region transcripts. Like HAV E3, a majority of the BAV-1 E3 region was not essential for growth in cell culture, as demonstrated by the construction of a recombinant BAV-1 lacking 60% of the putative E3 region.

Bovine herpesvirus 1 glycoprotein M forms a disulfide-linked heterodimer with the U(L)49.5 protein

Nine glycoproteins (gB, gC, gD, gE, gG, gH, gI, gK, and gL) have been identified in bovine herpesvirus 1 (BHV-1). gM has been identified in many other alpha-, beta-, and gammaherpesviruses, in which it appears to play a role in membrane penetration and cell-to-cell fusion. We sought to express BHV-1 open reading frame U(L)10, which encodes gM, and specifically identify the glycoprotein. We corrected a frameshift error in the published sequence and used the corrected sequence to design coterminal peptides from the C terminus. These were expressed as glutathione S-transferase fusion proteins in Escherichia coli. The fusion protein containing the 63 C-terminal amino acids from the corrected gM sequence engendered antibodies that immunoprecipitated a 30-kDa protein from in vitro translation reactions programmed with the U(L)10 gene. Proteins immunoprecipitated by this antibody from virus-infected cells ran at 36 and 43 kDa in reducing sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and 43 and 48 kDa in nonreducing SDS-PAGE. Only the larger of the pair was present in virions. A 7-kDa protein was released from gM by reducing agents. The 7-kDa protein was not recognized in Western blots probed with the anti-gM antibody but reacted specifically with antibodies prepared against BHV-1 U(L)49.5, previously reported to be a 9-kDa protein associated with an unidentified 39-kDa protein (X. Liang, B. Chow, C. Raggo, and L. A. Babiuk, J. Virol. 70:1448-1454, 1996). This is the first report of a small protein covalently bound to any herpesvirus gM. Similar patterns of hydrophobic domains and cysteines in all known gM and U(L)49.5 homologs suggest that these two proteins may be linked by disulfide bonds in all herpesviruses.

The bovine herpesvirus type 1 UL3.5 open reading frame encodes a virion structural protein

The bovine herpesvirus type 1 (BHV-1) open reading frame (ORF) UL3.5 is similar to ORFs found in pseudorabies virus, infectious laryngotracheitis virus, equine herpesvirus type 1, and varicella zoster virus, but clearly absent from herpes simplex virus. The published sequence for this ORF predicts a 126-amino-acid (13.2 kDa) protein product with an isoelectric point of 12.3. We confirmed the UL3.5 sequence, expressed the ORF as a glutathione-S-transferase fusion protein, and made rabbit antibodies against the purified fusion protein. The antiserum detected a 13-kDa protein in Western blots of MDBK cells infected with BHV-1, but not with other herpesviruses or uninfected cells. The BHV-1 UL3.5 protein was characterized as a component of the virion envelope or tegument because it was expressed as a late protein, it was present in the cytoplasm but not the nucleus of infected cells, and it was removed from purified virions by detergent extraction.

A monoclonal antibody to inclusion body disease of cranes virus enabling specific immunohistochemistry and competitive ELISA

Inclusion body disease of cranes (IBDC) herpesvirus kills some infected cranes and persists in convalescent animals. To enable further study and rapid identification of carrier animals, we developed a monoclonal antibody (MAb) to IBDC virus and used it in immunohistochemistry and a competitive enzyme-linked immunosorbent assay (ELISA). We used conventional techniques to make murine MAbs directed against IBDC virus purified from infected duck embryo cells. Hybridomas reacting in an ELISA with IBDC virus but not uninfected duck embryo cells were characterized by radioimmunoprecipitation, in situ immunohistochemistry, and competitive ELISA with neutralizing and nonneutralizing crane sera. MAb 2C11 immunoprecipitated 59-, 61-, and 110-kD proteins from IBDC virus-infected but not uninfected cells and stained glutaraldehyde-fixed IBDC virus plaques but not surrounding uninfected duck embryo cells in vitro. Antibody 2C11 did not react with duck embryo cells infected with falcon herpesvirus, psittacine herpesvirus, infectious laryngotracheitis, pigeon herpesvirus, or duck plague virus. A competitive ELISA using antibody 2C11 identified most sera that were positive in the neutralization test. This antibody will be useful in further characterizing IBDC virus, its pathogenesis, and its natural history.

Yeast-secreted bovine herpesvirus type 1 glycoprotein D has authentic conformational structure and immunogenicity

Bovine herpesvirus-1 (BHV-1) glycoprotein D (gD), an envelope glycoprotein, engenders mucosal and systemic immunity protecting cattle from viral infection. Production of gD with authentic immunogenicity is required for a subunit vaccine. We placed the truncated BHV-1 gD gene, lacking its putative transmembrane and cytoplasmic domains, under the control of the methanol-inducible AOX1 promoter in the yeast Pichia pastoris. Truncated BHV-1 gD (tgD) was efficiently secreted into the culture medium as a 68 kDa protein using either the yeast alpha prepro or native BHV-1 gD signal sequences. The yeast-secreted tgD had N-linked glycosylation and appears to have authentic conformational structure and immunogenicity based on the following observations A panel of monoclonal antibodies recognizing five neutralizing epitopes reacted with yeast tgD. Sera from yeast tgD-immunized mice immunoprecipitated native BHV-1 gD and neutralized BHV-1 infection in vitro. Yeast tgD competitively blocked all reaction between native gD and monospecific gD polyclonal sera from cattle. Based on these data, yeast-derived BHV-1 tgD is an excellent candidate for a subunit vaccine.

Vesicular stomatitis New Jersey virus RNA persists in cattle following convalescence

To test the hypothesis that vesicular stomatitis New Jersey virus (VSV-NJ) persists in convalescent cattle, we used explant cultures and reverse transcription nested polymerase chain reactions to probe for viral genomic, replicative intermediate, and mRNA in two cows experimentally inoculated in the tongue 5 months earlier and three cows naturally infected 4-14 months previously. Virus was not isolated from any tissues of any animal. Sequences of the viral polymerase and nucleocapsid genes were consistently identified in the tongue and lymph nodes draining the tongue of both experimentally infected animals but not in the three naturally infected animals. Replicative intermediate but not messenger RNA sequences were detected. These results showed for the first time the long term persistence of VSV-NJ RNA in its bovine host.

Persistence of vesicular stomatitis virus New Jersey RNA in convalescent hamsters

Persistence of vesicular stomatitis virus New Jersey (VSV-NJ) was studied in experimentally infected hamsters (Mesocricetus auratus). We used reverse transcription and nested polymerase chain reaction (RT-NPCR) to probe tissues of hamsters inoculated with VSV-NJ Hazelhurst. Viral genomic RNA was detected in the brain, cerebellum, spleen, liver, kidney, and lung 2 months after infection, but only in the central nervous system at 10 and 12 months. Viral messenger RNA was detected in the brain of one hamster at 2 months after infection. Replicative intermediate was detected in the spinal cord of one hamster at 12 months. These results suggest that VSV-RNA persists in animals for long periods following infection, disease, and convalescence. However, infectious virus was not recovered from tissues by conventional serial passages of tissue extracts in Vero cells or by cocultivation.

Mucosal and systemic immunity to bovine herpesvirus-1 glycoprotein D confer resistance to viral replication and latency in cattle

Mucosal immunity in the respiratory tract directed against bovine herpesvirus-1 (BHV-1) glycoprotein B forms an effective barrier against BHV-1 replication in cattle. Here we investigated the ability of a second BHV-1 glycoprotein, gD, to engender specific antibodies in nasal secretion and serum and protect against infection. We expected gD to give greater protection than gB because anti-gD antibodies prevent viral penetration into cells at much lower concentrations than anti-gB antibodies. Calves vaccinated once subcutaneously and thrice intranasally with affinity-purified BHV-1 gD had mucosal antibodies and three of five were protected against intranasal challenge by 10(7) p.f.u. of BHV-1. Four of the five vaccinated calves were proven free of BHV-1 latency by the lack of viral shedding following immunosuppression. The putative mucosal adjuvant, cholera toxin B subunit (CTB), did not significantly enhance mucosal immunity or protection against challenge or latency (P0.5) since only 4 of 6 gD plus CTB immunized calves were completely protected. Taken together, these data suggest that BHV-1 gD may be useful in a mucosal vaccine against BHV-1 infection in cattle but is less than totally effective when used alone.

Nucleotide sequence analysis of a 30-kb region of the bovine herpesvirus 1 genome which exhibits a colinear gene arrangement with the UL21 to UL4 genes of herpes simplex virus

We report the nucleotide sequence of the 19-kb HindIII fragment B of bovine herpesvirus 1 (BHV-1) DNA and adjacent parts of the HindIII A and L fragments, which together span a still completely uncharted 30-kb region located between the glycoprotein H gene and the right end of the unique long segment. The analysis revealed 17 complete open reading frames (ORFs) and 2 ORFs that were interrupted by potential splice donor and acceptor sites. All of these ORFs exhibited strong amino acid sequence homology to the gene products of other alphaherpesviruses. The BHV-1 ORFs were arranged colinearly with the prototype sequence of herpes simplex virus 1 in the range of the UL21 to UL4 genes. Colinearity was also observed with the genes of betaherpesviruses and gamma herpesviruses, although not all ORFs exhibited clear sequence homology. The possible functions of the proteins encoded within the sequenced region are assessed and features found are discussed. Unexpected findings include the following: high amino acid sequence conservation among alphaherpesviruses despite large differences in G + C content, ranging from 45% for varicella zoster virus to 72% for BHV-1; high similarity with other UL20 proteins at the predicted structural level in spite of relatively low amino acid homology; and a 2-kb open reading frame overlapping UL19 in the opposite sense and exhibiting high amino acid similarity to the same area of pseudorabies virus.

Bovine herpesvirus 1 gIV-expressing cells resist virus penetration

The interaction of bovine herpesvirus 1 (BHV-1) with the BHV-1 glycoprotein IV (gIV)-expressing cell line D1-1 was examined by radiolabelled virus adsorption assays, in situ autoradiography and electron microscopy. Adsorption of radiolabelled BHV-1 to D1-1 cells was similar to that observed in control cell lines but in situ radiography revealed that virus moved to the nucleus of control but not the gIV-expressing cells. Electron microscopy studies showed that BHV-1 attached to the cell membranes of D1-1 and control cells at 4 degrees C but penetration of virus was observed only in control cells when the temperature was shifted to 37 degrees C. These results provide further evidence that cellular expression of gIV does not prevent viral adsorption, but does prevent the entrance of the virus into the cell.

Rapid detection of vesicular stomatitis virus New Jersey serotype in clinical samples by using polymerase chain reaction

Vesicular stomatitis virus of the New Jersey serotype (VSV-NJ) causes vesicular disease in cattle, pigs, and horses throughout the Americas. Vesicular disease is clinically indistinguishable from foot-and-mouth disease (FMD). Therefore, outbreaks of vesicular disease in FMD-free areas must be rapidly diagnosed by laboratory methods and affected farms must be quarantined until laboratory results confirm the absence of FMD. Diagnosis is currently performed in high-containment (biosafety level 3) laboratories by using complement fixation and virus isolation in tissue culture. We describe here an alternative method for the detection of VSV-NJ RNA in clinical samples. This method includes a rapid acid guanidine-phenol RNA extraction procedure coupled with a one-tube polymerase chain reaction (PCR) using reverse transcriptase. By using this test, we were able to detect the largest number of positive samples (53 of 58), followed by complement (48 of 58) and isolation in tissue culture (43 of 58). The primers chosen for this assay amplify a 642-nucleotide region of the phosphoprotein gene of VSV-NJ but not of VSV-IN. Sequencing of the PCR product enables genetic typing of virus isolates and epidemiological studies. Since no infectious materials are necessary to perform this test and any infectious virus in clinical samples is destroyed by acid guanidine-phenol treatment, diagnosis can be safely performed in regular diagnostic laboratories.

Resistance and susceptibility of bovine cells expressing herpesviral glycoprotein D homologs to herpesviral infections

Bovine cell lines individually expressing two related herpesviral proteins, pseudorabies virus glycoprotein 50 and herpes simplex virus type 1 glycoprotein D, were examined for their susceptibility/resistance to infection with several alphaherpesviruses. Cell lines expressing gp50 or gD-1 resisted plaque formation by the homologous virus more than by the heterologous viruses. Bovine cells expressing bovine herpesvirus 1 glycoprotein IV (gIV) were susceptible to infection with three other bovine herpesviruses: bovine herpesvirus 2, bovine herpesvirus 4 (BHV-4) and alcelaphine herpesvirus 1. One line of gIV-expressing cells was resistant to the formation of BHV-4 plaques, suggesting that a cell-associated factor may be responsible for inhibiting cell-to-cell spread.

Mechanisms of bovine herpesvirus type 1 neutralization by monoclonal antibodies to glycoproteins gI, gIII and gIV

We examined a panel of monoclonal antibodies (MAbs) against bovine herpesvirus type 1 (BHV-1) glycoproteins gI, gIII and gIV for inhibition of virus attachment and interference with subsequent steps of infection. Attachment of radiolabelled virions was partially prevented by 600 to 700 micrograms/ml of IgM antibodies against gI and gIII and one IgG2A antibody against gIV, but not by the majority of MAbs against any of the three viral glycoproteins. Productive infection following attachment was prevented by lower concentrations of MAbs 5106 and 4807 against gI and by 0.7 to 5.5 micrograms/ml of all five MAbs against gIV. MAbs against gIV had almost the same activity whether added before or after BHV-1 was incubated with cells, suggesting that their principal activity is to prevent the penetration of virus through the cell membrane. The ability of polyethylene glycol to overcome neutralization by one anti-gIV MAb supported this concept, but an attempt to confirm this by direct electron microscopy failed. A bovine monospecific antiserum against gIV had approximately 10-fold more neutralizing activity against BHV-1 than did antisera against gI or gIII. Complement increased the activity of anti-gI and anti-gIII MAbs by 10- to 100-fold, but had little or no effect on neutralization by anti-gIV MAbs. Some antibodies against gI and gIV inhibited the enlargement of plaques in cell cultures. Taken together, these data suggest that MAbs against gIV are the principal agents of BHV-1 neutralization, and that these antibodies can be fully effective in areas such as the ocular and respiratory mucosae, from which complement is absent at the time of primary exposure to infection.

Induction of a mucosal barrier to bovine herpesvirus 1 replication in cattle

Current vaccines for human and animal herpesviruses engender an immunity that may ameliorate disease but generally fails to prevent infection, latency, reactivation from latency, or spread through a population. By administering intranasally to cattle bovine herpesvirus type 1 virion envelope proteins combined with the potent mucosal immune system adjuvant, cholera toxin B subunit, we engendered a local antibody response that acted as a barrier to infection of mucosal epithelial cells and thereby prevented viral replication, consequently precluding disease, latency, and spread.

Bovine cells expressing bovine herpesvirus 1 (BHV-1) glycoprotein IV resist infection by BHV-1, herpes simplex virus, and pseudorabies virus

We expressed the bovine herpesvirus 1 (BHV-1) glycoprotein IV (gIV) in bovine cells. The protein expressed was identical in molecular mass and antigenic reactivity to the native gIV protein but was localized in the cytoplasm. Expressing cells were partially resistant to BHV-1, herpes simplex virus, and pseudorabies virus, as shown by a 10- to 1,000-fold-lower number of plaques forming on these cells than on control cells. The level of resistance depended on the level of gIV expression and the type and amount of challenge virus. These data are consistent with previous reports by others that cellular expression of the BHV-1 gIV homologs, herpes simplex virus glycoprotein D, and pseudorabies virus glycoprotein gp50 provide partial resistance against infection with these viruses. We have extended these findings by showing that once BHV-1 enters gIV-expressing cells, it replicates and spreads normally, as shown by the normal size of BHV-1 plaques and the delayed but vigorous synthesis of viral proteins. Our data are consistent with the binding of BHV-1 gIV to a cellular receptor required for initial penetration by all three herpesviruses and interference with the function of that receptor molecule.

Vesicular stomatitis New Jersey virus glycoprotein gene sequence and neutralizing epitope stability in an enzootic focus

Vesicular stomatitis New Jersey (VS NJ) virus is capable of undergoing rapid evolution in nature and therefore has the potential for antigenic variation. We selected an area of Costa Rica where VS NJ virus is enzootic to study whether this virus used the mechanism of antigenic variation to persist in nature. Three sentinel herds and three nonsentinel herds were observed from 1986 to 1988. Eleven VS NJ virus isolates were collected from naturally infected cattle. Remarkably, nine animals that were bled prior to reinfection with VS NJ virus had neutralizing antibody titers up to 1: 102,400 yet virus was isolated from, and disease was observed in, these animals. Sequence analysis of the portion of the glycoprotein gene coding for the neutralizing epitopes demonstrated that all virus isolates were 98-100% similar with no indication of specific genetic variation. The 3' end of the glycoprotein gene also remained stable in that all isolates were again 98-100% similar in nucleotide sequence. Each isolate was neutralized to equivalent titers with monoclonal antibodies directed against four neutralizing epitopes on the glycoprotein. Additionally, preisolation sera from each animal were able to neutralize the virus that caused the subsequent disease. These results provide evidence that antigenic variation is not a mechanism used by VS NJ virus to persist in an enzootic focus of Costa Rica.

Serological monitoring of vesicular stomatitis New Jersey virus in enzootic regions of Costa Rica

The activity of vesicular stomatitis viruses was monitored on 3 dairy farms in Costa Rica. Antibody levels were measured and clinical disease monitored in 165 cattle during a 20 month period (1986-1988). Vesicular stomatitis New Jersey (VS NJ) virus was shown to be enzootic on these farms by a 94.2% prevalence of neutralizing antibody; this did not vary significantly between herds. The mean prevalence of antibody to vesicular stomatitis Indiana (VS IN) virus was 15.2%, but was significantly higher in 1 herd. A total of 25 cases (annual incidence rate of 9%) of clinical vesicular stomatitis (VS) was reported. VS NJ virus was identified as the causal agent by detection of VS NJ virus antigens by the complement fixation test. VS NJ virus was isolated in 11 cases. All episodes of disease occurred between November and January, the beginning of the dry season. Most animals maintained stable neutralizing antibody titers throughout the study, and all diseased animals were previously seropositive to VS NJ virus. A total of 31 animals with neutralizing antibodies to VS NJ virus had a VS NJ virus-specific IgM response, and 6 animals had IgM responses that persisted for as long as 6 months. There was no relation between IgM responses and clinical disease occurrence. VS NJ virus persisted predominantly as a subclinical infection in cattle throughout the year in enzootic areas of Costa Rica. The humoral response did not prevent reinfection with VS NJ virus.

Effects of formalin inactivation on bovine herpes virus-1 glycoproteins and antibody response elicited by formalin-inactivated vaccines in rabbits

The possibility of using a radioimmune assay (RIA) to measure the retention of antigenic determinants on gI, gIII, and gIV, the three major bovine herpes virus 1 (BHV-1) glycoproteins, during the formalin inactivation and aluminium hydroxide adsorption commonly used in the manufacture of killed virus vaccines was investigated. Monoclonal antibodies were used to measure thirteen previously identified glycoprotein epitopes in experimental vaccines containing live BHV-1 or formalin-killed BHV-1 and a commercial formalin-inactivated BHV-1 vaccine. All four epitopes on gI lost 80-97% of their ability to bind monoclonal antibodies. Two of five epitopes on gIII were preserved but the other three epitopes on gIII and five on gIV were reduced as much as 88%. To show that the measured loss of epitopes was biologically relevant, the vaccines were administered to rabbits and the resulting antibody responses against the same epitopes were evaluated by competition RIA. Little correlation was found between the measured antigenic site destruction and the rabbit response against those antigenic sites, suggesting that monoclonal antibody reactivity of a formalin-inactivated vaccine could not provide a meaningful measure of antigenic activity.

The effect of bovine herpesvirus type 1 glycoproteins gI and gIII on herpesvirus infections

We expressed the bovine herpesvirus type 1 (BHV-1) glycoproteins, gI and gIII, in bovine cells using a bovine papillomavirus vector. The proteins expressed by these cells had the same Mr as the native BHV-1 proteins and monoclonal antibodies detected no differences in their antigenic structure. Cells expressing gI were infected with either BHV-1 or herpes simplex virus type 1 (HSV-1). The number of plaques in gI-expressing cells was similar to that seen with normal fibroblasts infected with BHV-1 or HSV-1. However, BHV-1 or HSV-1 plaques produced in gI-expressing cells were smaller and darker than those seen in normal fibroblasts indicating an interference with cell-to-cell transmission or cellular lysis. Virus growth curves and [35S]methionine labelling of BHV-1-infected gI-expressing cells showed no difference in virus production, virus protein synthesis or cellular protein shutdown when compared to BHV-1-infected normal cells. This led us to conclude that the gI protein may interfere with a cellular protein(s) responsible for the cytopathic effects of BHV-1 infection. Cells expressing gIII were fully susceptible to BHV-1 infection.

Bovine naturally cytolytic cell activation against bovine herpes virus type 1-infected cells does not require late viral glycoproteins

Freshly isolated or overnight cultured bovine peripheral blood mononuclear (PBM) cells lysed bovine herpes virus 1 (BHV-1)-infected allogeneic and xenogeneic target cells but not non-infected target cells. To determine if late viral genes contribute to target cell lysis, phosphonoacetic acid (PAA), an inhibitor of DNA polymerase activity, was used to block DNA replication that is required for expression of late viral proteins. Both adherent and non-adherent (NA) cell populations mediated lysis against PAA-treated BHV-1-infected target cells in both 4- and 20-hr assays, indicating recognition and killing occurred in the absence of expression of late BHV-1 glycoproteins. Thus recognition of BHV-1 by bovine natural cytolytic effector cells does not require recognition of late BHV-1 glycoproteins for killing virally infected target cells.

Preincubation of bovine blood neutrophils with bovine herpesvirus-1 does not impair neutrophil interaction with Pasteurella haemolytica A1 in vitro

In this study we examined the direct effects of bovine herpesvirus-1 on the interaction of bovine blood neutrophils with Pasteurella haemolytica A1. Preincubation of neutrophils for approximately 2 h in vitro with BHV-1 at a multiplicity of infection of 5:1 had no effect on neutrophil random migration and directed migration to zymosan-activated bovine serum. Neutrophils also were unimpaired in their ability to ingest and kill P. haemolytica A1. Preincubation of neutrophils with BHV-1 did not elicit an oxidative burst, as measured by luminol-enhanced chemiluminescence, nor did it alter neutrophil chemiluminescence in response to opsonized P. haemolytica A1. Prolonged preincubation with BHV-1 for 18-24 h similarly did not affect neutrophil chemiluminescence in response to opsonized P. haemolytica A1. The susceptibility of neutrophils to the lethal effects of crude P. haemolytica cytotoxin also was unaltered by preincubation with BHV-1. We observed no evidence of BHV-1 replication in bovine neutrophils as determined by indirect immunofluorescence and electron microscopy. Previous reports have indicated that active BHV-1 infection alters certain neutrophil functions and results in hypersusceptibility to pulmonary pasteurellosis. Our results suggest that these effects are unlikely to be mediated directly by BHV-1, but instead may reflect the action of endogenous mediators that are released during active BHV-1 infection.

Effects of immunization with bovine herpesvirus-1 glycoproteins on bovine herpesvirus-1-induced alteration of bovine neutrophil chemotactic and anti-Pasteurella haemolytica activities

It has been reported previously that active bovine herpesvirus-1 (BHV-1) infection greatly enhances the susceptibility of cattle to secondary bacterial pneumonia involving Pasteurella haemolytica. The present study examines the possibility that immunization of BHV-1 naive calves with purified BHV-1 glycoproteins would protect them against changes in neutrophil function that might compromise their ability to eliminate P. haemolytica during an active BHV-1 infection. The results show that circulating neutrophil chemotactic activity was generally reduced at 7-8 days after BHV-1 challenge; immunization with a 77 kilodalton BHV-1 glycoprotein (gIV) prevented impairment of neutrophil chemotaxis. BHV-1 infection did not markedly affect the ability of neutrophils to ingest and kill P. haemolytica in vitro. Immunization and challenge with BHV-1 had little effect on the chemiluminescence response of bovine neutrophils to opsonized P. haemolytica in vitro, although in one experiment a marked increase in baseline neutrophil chemiluminescence was observed which may be relevant to understanding the pathogenesis of pulmonary damage that occurs in BHV-1 infected calves.

Passively administered neutralizing monoclonal antibodies do not protect calves against bovine herpesvirus 1 infection

Monoclonal antibodies specific for defined epitopes on the gI, gIII and gIV envelope glycoproteins of BHV-1 were used individually or in glycoprotein-monospecific pools for passive immunization of young calves. Although serum antibody titres comparable to those found in naturally infected and recovered calves were achieved, passive immunization failed to prevent the growth of BHV-1 in nasal and ocular mucosa and did not decrease the duration of viral shedding.

Epitope specificity and protective efficacy of the bovine immune response to bovine herpesvirus-1 glycoprotein vaccines

Bovine herpesvirus-1 (BHV-1) envelope glycoproteins gI, gIII and gIV were individually purified on monoclonal antibody affinity columns and injected intradermally into BHV-1 seronegative calves. The calves developed serum neutralizing antibodies that monospecifically precipitated the immunizing glycoprotein from a preparation of 125I-labelled BHV-1 envelope proteins. A competitive radioimmunoassay using the bovine antisera demonstrated that known functional epitopes had been retained in the glycoprotein vaccines. Calves immunized with the gI, gIII or gIV glycoproteins were not protected from intranasal challenge with BHV-1 and had levels and duration of viral shedding in their nasal secretions similar to those of non-immunized control calves.

Monoclonal antibody analysis of bovine herpesvirus-1 glycoprotein antigenic areas relevant to natural infection

Neutralizing antigenic areas on the glycoproteins of bovine herpesvirus-1 (BHV-1) were identified by reciprocal competition radioimmunoassays using monoclonal antibodies. Three interrelated and two independent antigenic areas were identified on the 77-kDa (K) gIV envelope glycoprotein. Antigenic analysis of this protein has not been previously described. Four interrelated and one independent antigenic areas were found on the 97K gIII envelope glycoprotein. A third group of monoclonal antibodies reacting in Western blot with the 74K subunit of gI, a 130K disulfide-linked 74K/55K heterodimer, revealed four interrelated antigenic areas. All of the antigenic areas on all three glycoproteins were reactive with neutralizing monoclonal antibodies and all were targets for antibody-complement lysis. However, antibodies against gIV were the most efficient at neutralizing the virus and rendering infected cells susceptible to antibody-complement lysis. Convalescent sera from experimentally infected calves were used in a competitive radioimmunoassay to confirm that each antigenic area on the gI, gIII, or gIV glycoproteins was a target for bovine antibodies during primary infection with BHV-1.

Temporal control of bovine herpesvirus 1 glycoprotein synthesis

The gI, gIII, and gIV glycoproteins are major bovine herpesvirus 1 antigens involved in virus neutralization. Results indicate that the gI and gIV glycoproteins were expressed as beta proteins, whereas the gIII glycoprotein was expressed strictly as a gamma protein. These findings suggest that gI and gIV may be superior to gIII as vaccine candidates.

Characterization of envelope proteins of infectious bovine rhinotracheitis virus (bovine herpesvirus 1) by biochemical and immunological methods

Ten glycoproteins of molecular weights of 180,000, 150,000, 130,000, 115,000, 97,000, 77,000, 74,000, 64,000, 55,000, and 45,000 (designated as 180K, 150K, etc.) and a single nonglycosylated 107,000-molecular-weight (107K) protein were quantitatively removed from purified bovine herpesvirus 1 (BHV-1) virions by detergent treatment. Immunoprecipitations with monospecific and monoclonal antibodies showed that three sets of coprecipitating glycoproteins, 180K/97K, 150K/77K, and 130K/74K/55K, were the major components of the BHV-1 envelope. These glycoproteins were present in the envelope of the virion and on the surface of BHV-1-infected cells and reacted with neutralizing monoclonal and monospecific antibodies. Antibodies to 150K/77K protein had the largest proportion of virus-neutralizing antibodies, followed by antibodies to 180K/97K protein. Monoclonal antibodies to 130K/74K/55K protein were neutralizing but only in the presence of complement; however, monospecific antisera produced with 55K protein did not have neutralizing activity. Analysis under nonreducing conditions showed that the 74K and 55K proteins interact through disulfide bonds to form the 130K molecule. Partial proteolysis studies showed that the 180K protein was a dimeric form of the 97K protein and that the 150K protein was a dimer of the 77K protein, but these dimers were not linked by disulfide bonds. The 107K protein was not glycosylated and induced antibodies that did not neutralize BHV-1. The 64K protein was not precipitated by anti-BHV-1 convalescent antisera, and monospecific antisera to this protein precipitated several polypeptides from uninfected cell lysates, suggesting that 64K is a protein of cellular origin associated with the BHV-1 virion envelope.

Monoclonal antibodies against African swine fever viral antigens

Monoclonal antibodies specific for African swine fever (ASF) viral proteins of 14, 32, 73, 174, and 240 kDa were produced and characterized. Immunoelectron microscopy detected the 73 kDa but not the 14-, 32-, or 240-kDa proteins at the surface of the virion. The 32-kDa protein was detected by radioimmunoassay 2 hr after infection of porcine monocytes and Vero cells, was detected in the seven widely divergent ASFV isolates tested, and stained brilliantly virus-infected cells in indirect immunofluorescence suggesting that monoclonal antibodies directed against this protein may be useful in ASFV diagnosis. Two monoclonal antibodies detected heterogeneity between ASF viruses.

Characterization of African swine fever virus antigenic proteins by immunoprecipitation

African swine fever virus is a large, complex virion in which numerous proteins have been identified by biochemical techniques. Few of these proteins have been shown to react with antibodies from recovered swine, leading to speculation that the immunological unreactivity of some viral proteins might explain the inability of immune sera from surviving animals to neutralize the virus. We used immunoprecipitation of radiolabeled viral proteins to examine these sera in more detail. Gradient sodium dodecyl sulphate polyacrylamide gel electrophoretic analysis of these immunoprecipitates revealed that at least 37 viral proteins participated in antigen-antibody reactions in this system. Differences in the molecular weights of some immunoprecipitable proteins were noted between different isolates of virus, between the same isolate grown in different cells, and between an isolate adapted to Vero cells and one not adapted to these cells.

The effect of temperature on production and function of bovine interferons

Subnormal temperatures were found to depress the production of interferon by bovid herpesvirus 2 (BHV-2)-infected bovine testicular cells, bovine peripheral blood leukocytes, and bovine monocytes, as well as by BHV-2 antigen-stimulated immune peripheral blood leukocytes. Interferon titers generated at 30 degrees C were approximately 10 percent of those at 40 degrees C. Also, subnormal temperatures depressed interferon function. Bovine testicular cells treated at 40 degrees C for 24 hours with high concentrations of BHV-2-induced bovine monocyte interferon or BHV-2 antigen-stimulated immune peripheral blood leukocyte interferon, and then infected with BHV-2 and retreated with interferon at 40 degrees C, had little or no viral growth or cytopathic effect after 72 hours. Cultures without interferon, or those treated with the same amount of interferon at 30 degrees C, had significantly more cytopathic effect and had viral titers up to 10(7) TCID50 higher than cultures at 40 degrees C. Earlier in vitro studies done without exogenous interferon showed that BHV-2 replicated to high titers at 30 degrees but not at 40 degrees C. Thus, at low temperatures (30 degrees C) in vitro, BHV-2 induced little interferon, was not highly suppressed by interferon, and replicated to high titers. At higher temperatures (40 degrees C), BHV-2 replication induced high interferon levels, was strongly suppressed by interferon, and replicated poorly. This may help explain the restriction of BHV-2 lesions to skin despite the presence of virus in both skin and internal organs in infected cattle.

Local tissue temperature: a critical factor in the pathogenesis of bovid herpesvirus 2

The effect of local tissue temperature on bovid herpesvirus 2 lesions in bovine skin was studied. Two areas of thoracic skin were multiply inoculated with virus and maintained at different temperatures; one above and the other below the rectal temperature of the animal. An entire inoculation site was removed daily from each area and subjected to virus, viral antigen, and interferon titrations and both light and electron microscopic examinations. Lesions in cold skin appeared sooner after inoculation, were larger and deeper, contained more infectious virus, viral antigen, and interferon, and lasted longer than lesions in hot skin. Differences in viral titers greater than 10(9) 50% tissue culture infective doses per gram were measured on postinfection days 5 to 9. These studies have demonstrated for the first time that temperature effects on viral pathogenesis may operate at the local level rather than by systemic modification of immune responses. The results also suggest that despite the presence of virus in internal organs of bovid herpesvirus 2-infected cattle and the ability of bovid herpesvirus 2 to replicate to very high titers in these tissues in vitro, only the skin is cool enough to permit substantial viral replication and dermal lesions in vivo. The observed restriction of bovid herpesvirus 2 skin lesions to the udder and teats of cattle and the restriction of outbreaks of disease to months when the temperature is declining may also be reflections of this temperature sensitivity.

Identification of bluetongue virus type 17 genome segments coding for polypeptides associated with virus neutralization and intergroup reactivity

Double-stranded (ds) RNA was isolated from either partially purified bluetongue virus (BTV) type 17 or BTV-17 infected cells. The RNA was denatured with either methylmercury hydroxide or dimethyl sulfoxide and translated in a reticulocyte cell-free system. The translation products were found to be similar to BTV-17 specific polypeptides in infected cells when analyzed by polyacrylamide gel electrophoresis and immunoprecipitation with BTV-17 specific polyclonal mouse ascitic fluid. The 10 dsRNA BTV-17 genome segments were resolved by preparative gel electrophoresis and the coding assignment of each segment was determined by translation in a cell-free system. Immunoprecipitation of VP3 from infected cell lysates by a type-specific neutralizing monoclonal antibody identified this polypeptide, which is coded for by genome segment 2, as being involved in virus neutralization. Immunoprecipitation of in vitro translation products directed by total BTV-17 RNA with a monoclonal antibody that reacts with all the serotypes of BTV and some other orbiviruses and precipitates VP7 directly demonstrated that gene segment 8 codes for this intergroup-specific polypeptide.

Production of interferon by bovine peripheral blood monocytes infected with bovid herpesvirus 2

The production of interferon by bovine peripheral blood leukocytes infected with bovid herpesvirus 2 (BHV-2) was investigated in preparation for studying mechanisms of resistance to BHV-2. It was found that bovine peripheral blood monocytes produced high levels of interferon in response to BHV-2 inoculated at a multiplicity of 1. Virus-induced interferon was not stable at pH 2, was destroyed at 56 degrees C or by incubation with trypsin and was active against both vesicular stomatitis virus and BHV-2. Interferon of high specific activity was produced by incubating monocytes for 5 h with BHV-2 in serum-containing medium, replacing the inoculum with serum-free medium for an additional 16 h, and concentrating the serum-free medium by dialysis against dry polyethylene glycol. Interferon concentrations of 40,000 units per mg of protein were readily attained.

Monoclonal antibody analysis of serotype-restricted and unrestricted bluetongue viral antigenic determinants

Twenty-one monoclonal antibodies that react with bluetongue virus (BTV) and have restricted or unrestricted serotype specificities were identified in culture supernatants of hybridomas derived from lymphocytes of mice immunized with BTV serotype 17. Hybridomas were screened and antibody specificities characterized in a solid-phase radioimmunoassay and by immunoprecipitation with radiolabeled, BTV 17-infected cell lysates. Three general serotype specificities were demonstrated by 13 antibodies that precipitated structural viral protein 9 (VP 9). One antibody precipitated VP 7, a 48,000 dalton nonstructural protein, and reacted in radioimmunoassay with 20 BTV serotypes and Epizootic Hemorrhagic Disease of Deer Virus serotype 1 (EHDV 1), EHDV 2, and Ibaraki virus, but not with uninfected cells. One serotype-specific antibody neutralized infectivity, inhibited hemagglutination by BTV 17, and precipitated VP 2 and VP 3. A second antibody, with restricted serotype specificity, precipitated VP 2 and VP 8. These results confirm those of others (Huismans and Erasmus, Onderstepoort J. Vet. Res. 48, 51-58, 1981) that BTV serotype-specific and neutralizing epitopes are associated with VP 2.

Heterogeneity of neutralization-related epitopes within a bluetongue virus serotype

Twenty-four monoclonal antibodies raised against a 1962 Wyoming isolate of blue-tongue virus serotype 17 (BTV 17) were tested against 20 other field isolates of this serotype in a solid-phase radioimmunoassay (RIA), neutralization, and mouse passive protection tests. Of the 21 antibodies that bound in RIA to acetone-fixed BTV-infected cells, 18 bound to cells infected with any of the BTV 17 isolates and 3 detected minor antigenic differences in two isolates. The remaining 3 antibodies, that bound in RIA only to unfixed virus-infected cells detected additional differences. Of the 3 antibodies binding to unfixed virus-infected cells one bound to all but 2 isolates. A second antibody, 6C3A.2, bound only to the Wyoming isolate and passively protected mice against this isolate. The third antibody, 6C2A.4.2, bound to the Wyoming isolate and to 8 isolates from the mid-South U. S., but not to 12 isolates from California. Antibody 6C2A.4.2 neutralized the Wyoming and mid-South isolates to which it bound and passively protected mice against the Wyoming isolate but provided little or no protection against 4 California isolates tested. Polyclonal serum from mice immunized against Wyoming BTV 17 bound in RIA to all BTV 17 isolates and neutralized all isolates. Thus, three neutralization-related antigenic determinants were disclosed, one (perhaps a set) recognized by immune sera on all BTV 17 isolates, a second recognized by antibody 6C2A.4.2 on the Wyoming and 8 mid-South isolates, and a third recognized by antibody 6C3A.2 only on the Wyoming isolate. These differences may be important in selection of virus strains for vaccine development.

Passive protection of mice and sheep against bluetongue virus by a neutralizing monoclonal antibody

A murine hybridoma antibody, 6C2A.4.2, previously characterized as an immunoglobulin G class 2a that binds in radioimmunoassay to bluetongue virus serotype 17 (BTV-17) but not the other 19 BTV serotypes, neutralizes BTV-17, inhibits hemagglutination with BTV-17, and precipitates viral polypeptides 2 and 3 from BTV-17-infected cells, was produced as an ascites in the peritoneal cavities of hybridoma-inoculated mice. This ascitic fluid, but not those containing other, non-neutralizing anti-BTV-17 antibodies of the same isotype, provided serotype-specific passive protection against BTV-17-induced death of neonatal mice. Antibody 6C2A.4.2-containing ascitic fluid was injected intravenously into sheep that were later inoculated with BTV-17. These sheep remained free of clinical signs, did not develop viremia or detectable levels of antibodies reactive in the immunodiffusion test used for routine BTV diagnosis in the United States, and developed only low levels of neutralizing antibodies. Control animals became viremic and developed immunodiffusion test reactions and high levels of neutralizing antibodies during recovery, and two of three had lesions and fevers. These results provide evidence that antibodies directed against a single epitope on BTV-17 can prevent bluetongue disease.

Sensitivity of bovid herpesvirus 2 replication to temperatures found in the natural host

Two isolates of bovid herpesvirus 2 replicated poorly in bovine testicular cells and fetal kidney cells at 39--40 degrees C, temperatures commonly observed in virus-infected cattle. High viral titers occurred in replicate cultures at 30--37 degrees C. Persistent viral infections were noted in cultures maintained at 40 degrees C. Interferon-like activity was not responsible for the high-temperature restriction since the level was not significantly different between virus-infected cultures incubated at 35 degrees or 40 degrees C. Spontaneous viral inactivation was only three times as rapid at 41 degrees as at 35 degrees C. Analysis of temperature shift experiments with respect to results of growth studies and electron microscopy indicated a temperature sensitive event late in replication. The sensitivity of bovid herpesvirus 2 replication to elevated temperature provides a possible explanation for the extensive viral growth and occasionally severe lesions which are limited exclusively to the skin of infected cattle.

Bovine herpes mammillitis in two New York dairy herds

Bovine herpes mammillitis was diagnosed in 2 New York dairy herds. Lesions ranged from vesiculation and ulceration of large (up to 10 cm wide) areas of udder and teat skin to single small (2-3 cm wide) plaques of edema. Some lesions resembled "umbilicated pocks" characteristic of cowpox virus infections. Recently freshened heifers were the most severely affected; older cows and heifers with less turgid udders had milder lesions. In 2 cows, incurable mastitis developed. In other cows, the lesions healed by centripetal growth of epidermis into the lesions. Diagnosis was made by isolation of bovid herpesvirus 2 from lesions in both herds and by serum-neutralization testing. Virus isolated from a cow in 1 herd was injected into 9 members of the same herd and may have been responsible for the absence of lesions on these animals; all other members of the herd were affected.

Bovid herpesvirus 2: natural spread among breeding bulls

Sera collected over a seven year period, together with detailed health and management records, were used in a retrospective study of Bovid herpesvirus 2 (BHV-2) spread within a large herd of breeding bulls. Virus spread rapidly throughout the bulls in one barn. Transfer of infected bulls to other barns was followed by further, although sporadic, spread of virus. Spread of BHV-2 from seropositive animals to susceptible bulls in close contact led to the conclusion that reactivation and transmission of latent virus had occurred. Semen from seropositive bulls did not transmit BHV-2 to seronegative calves that were purposefully inoculated by the intranasal or intravenous routes.

Bovid herpesvirus 2 latency: failure to recover virus from central sensory nerve ganglia

Latent bovid herpesvirus 2 was sought in sensory ganglia, epithelium and lymph nodes from cattle having antibodies against bovid herpes virus 2. Tissues from eight animals were maintained in vitro as explants for 49-72 days during which all expended media was tested for virus. Three animals were pretreated with corticosteroids prior to slaughter. Infectious bovine rhinotracheitis virus was recovered from one animal, but bovid herpesvirus 2 was not detected.

Monoclonal antibody-defined human lung cell surface protein antigens

Monoclonal antibodies were used to define four distinct antigens present on the surface of human lung tumors. Immunoprecipitation of the four antigens by monoclonal antibodies and sodium dodecyl sulfate:polyacrylamide gel electrophoresis reveals that they have distinct complex structures. Different patterns of expression of these antigens on cells of other than lung tumor origin were detected by the same panel of monoclonal antibodies.