Cloning and cleavage site mapping of DNA from bovine herpesvirus 1 (Cooper strain)

Rapid and simple colorimetric loop-mediated isothermal amplification (LAMP) assay for the detection of Bovine alphaherpesvirus 1

As the causative agent of Infectious Bovine Rhinotracheitis (IBR) and Infectious Pustular Vulvovaginitis/Balanoposthitis (IPV/IPB), Bovine alphaherpesvirus 1 (BoHV-1) is responsible for high economic losses in the cattle industry worldwide. This study aimed to establish a fast, colorimetric loop-mediated isothermal amplification (LAMP) assay for the detection of viral DNA. Phenol red is used as pH-sensitive readout, relying on a distinct color change from pink to yellow in case of a positive reaction. LAMP reactions with different primers were compared and a newly designed set targeting the gene encoding the tegument protein V67 provided best results, enabling readout within 8-30 min. LAMP showed less cross-reactions with other ruminant alphaherpesviruses than qPCR but was 10-fold less sensitive. However, LAMP still detected down to 14 copies. The test performance was evaluated using 26 well-characterized nasal swabs from cattle with respiratory disease. All samples were correctly identified when using column-extracted DNA. Using a simple DNA precipitation method, only two weak-positive samples turned indeterminate. Combining this DNA precipitation with a makeshift water bath heated by a gastronomic immersion heater allowed successful application of the colorimetric LAMP assay under resource-limited conditions. This technique can therefore help in managing IBR/IPV outbreaks where sophisticated laboratory equipment is unavailable.

Phylogenetic analysis and characterization of bovine herpesvirus-1 in cattle of China, 2016-2019

Bovine herpesvirus type 1 (BoHV-1) is one of the most critical pathogens in cattle and is prevalent in China. BoHV-1 is divided into two gene types, BoHV-1.1 and 1.2, which are further differentiated into two subtypes, BoHV-1.2a and 1.2b. However, the phylogenetic analysis of BoHV-1 isolates has not been reported in China. To perform a molecular epidemiological survey based on isolates from cattle in China, 102 lung tissue samples of calves under ten months of age with respiratory disease (BRD) that died from 2016 to 2019 in China were used to isolate BoHV-1 with Madin-Darby bovine kidney (MDBK) cells. Part of the BoHV-1 isolates were applied to the phylogenetic analysis based on the region of the glycoprotein C (gC) gene of BoHV-1. Thirty BoHV-1 isolates were obtained, and the gC gene of 13 isolates was amplified by polymerase chain reaction (PCR) methods and sequenced. The result of the phylogenetic analysis according to the 451-nucleotide portion of the gC gene found that all of 13 isolates belonged to the BoHV-1.2b gene subtype, but these isolates had located two different phylogenetic tree branches. The gC gene sequence homology of isolates in group1 was higher with a reference strain of BoHV-1.2b EVI14 up to 98.0-100%, while in group 2, this was higher with reference strain BoHV-1.2b B589 up to 97.8-99.8%. The deduced amino acid sequence of gC from isolates in group 2 had two amino acid mutations with interference strain BoHV-1.2b K22 or BoHV-1.1 COOPER. The cytopathic effects (CPEs) of BoHV-1 isolates in group 2 were ulcered on the centration like a volcano on MDBK cell, and different from traditional CPEs of BoHV-1. Overall, BoHV-1.2b seems to be the primary strain of BoHV-1 in cattle in China and is also a critical cause of BRD. These BoHV-1.2b isolates had significant genetic variations.

Distinctive features of bovine alphaherpesvirus types 1 and 5 and the virus-host interactions that might influence clinical outcomes

Bovine herpesvirus types 1 (BoHV-1) and 5 (BoHV-5) are two closely related alphaherpesviruses. BoHV-1 causes several syndromes in cattle, including respiratory disease and sporadic cases of encephalitis, whereas BoHV-5 is responsible for meningoencephalitis in calves. Although both viruses are neurotropic, they differ in their neuropathogenic potential. This review summarizes the findings on the specific mechanisms and pathways known to modulate the pathogenesis of BoHV-1 and BoHV-5, particularly in relation to respiratory and neurological syndromes, which characterize BoHV-1 and BoHV-5 infections, respectively.

Cloning and sequencing gB, gD, and gM genes to perform the genetic variability of bovine herpesvirus-1 from Indonesia

AIM

Previous research has shown that bovine herpesvirus-1 (BHV-1) in Indonesia was closely related to subtype-1 based on glycoprotein D genes. This study aimed to analyze the genetic variability of the BHV-1 isolated from the recent case in Indonesia not only based on gD but also other genes such as gB and gM and to study the homology and similarity of the sample to other BHV-1 isolated in other countries or regions.

MATERIALS AND METHODS

Samples were drawn from the tracheal organ in recent field case and prepared for DNA extraction. The gB, gD, and gM were amplified using nested polymerase chain reaction (nPCR) with our specifically designed primer pair and based on the specified bands of 350 bp gB, 325 bp gD, and 734 bp gM confirmed as BHV-1. The PCR product was ligated into pGEM-T and transformed into competent Escherichia coli. The purified plasmid was subsequently sequenced.

RESULTS

The virus sample isolated from the recent field case of infectious bovine rhinotracheitis (IBR) from Indonesia showed variability based on the gB, gD, and gM sequences. However, all of the genes had high similarity (98-100%) to BHV-1.2.

CONCLUSION

The recent field case of IBR in Indonesia was similar to BHV-1.2.

A proteomic study of the differential protein expression in MDBK cells after bovine herpesvirus type 1 infection (BHV-1) strain treatment

Different BHV-1 strains, such as the virulent IBRV LN01/08 strains and the attenuated vaccine strain IBRV LNM, produces different clinical immune responses; however, the study of the differential protein expression in Madin-Darby bovine kidney (MDBK) cells after BHV-1-infection still remains unclear. Here, we applied a comparative proteomic strategy, based on 2D and MALDI-TOF/MS platforms, to examine the differential expression of proteins in MDBK cells that were treated and not treated with virulent IBRV LN01/08 and attenuated IBRV LNM strains. A total of eight differential proteins, including pyruvate kinase, heat shock protein (HSP) 90 (HSP90AA1 and HSP90AB1), annexin A, albumin (ALB), scinderin (SCIN), tubulin (alpha 1a) and vimentin (VIM), were identified. Among these proteins, pyruvate kinase, and HSP90 (HSP90AB1), tubulin and vimentin were identified in the virulent IBRV LN01/08 strain group, but were not identified in the attenuated IBRV LNM group. These results play an important role in tumor formation and development, cell migration, tumor cell line apoptosis, cell invasion and viral infection. The HSP90 (HSP90AA1) protein was identified in the control group and the attenuated IBRV LNM-infected group. Most studies have shown that HSP90 proteins were more of a cancer gene target, and inhibiting its function would result to oncogene degradation during cancer treatment. On the other hand, ALB is associated to cell differentiation, apoptosis, necrosis, cell death, viral infection, autophagy, interstitial tissue inflammation, and cell survival. These results provide a theoretical basis for the systematic understanding of BHV-1-infection mechanisms and BHV-1-induced immune responses.

Immunity to Bovine Herpesvirus 1: I. Viral lifecycle and innate immunity

Bovine herpesvirus 1 (BHV-1) causes a variety of diseases and is globally distributed. It infects via mucosal epithelium, leading to rapid lytic replication and latent infection, primarily in sensory ganglia. Large amounts of virus can be excreted by the host on primary infection or upon recrudescence of latent infection, resulting in disease spread. The bovine immune response to BHV-1 is rapid, robust, balanced, and long-lasting. The innate immune system is the first to respond to the infection, with type I interferons (IFNs), inflammatory cytokines, killing of infected host cells, and priming of a balanced adaptive immune response. The virus possesses a variety of immune evasion strategies, including inhibition of type I IFN production, chemokine and complement binding, infection of macrophages and neutrophils, and latency. BHV-1 immune suppression contributes to the severity of its disease manifestations and to the bovine respiratory disease complex, the leading cause of cattle death loss in the USA.

Comparative analysis of replication characteristics of BoHV-1 subtypes in bovine respiratory and genital mucosa explants: a phylogenetic enlightenment

In general, members of the Alphaherpesvirinae use the epithelium of the upper respiratory and/or genital tract as a preferential site for primary replication. Bovine herpesvirus type 1 (BoHV-1) may replicate at both sites and cause two major clinical entities designated as infectious bovine rhinotracheitis (IBR) and infectious pustular vulvovaginitis/balanoposthitis (IPV/IPB) in cattle. It has been hypothesized that subtype 1.1 invades preferentially the upper respiratory mucosa whereas subtype 1.2 favors replication at the peripheral genital tract. However, some studies are in contrast with this hypothesis. A thorough study of primary replication at both mucosae could elucidate whether or not different BoHV-1 subtypes show differences in mucosa tropism. We established bovine respiratory and genital organ cultures with emphasis on maintenance of tissue morphology and viability during in vitro culture. In a next step, bovine respiratory and genital mucosa explants of the same animals were inoculated with several BoHV-1 subtypes. A quantitative analysis of viral invasion in the mucosa was performed at 0 h, 24 h, 48 h and 72 h post inoculation (pi) by measuring plaque latitude and penetration depth underneath the basement membrane. All BoHV-1 subtypes exhibited a more profound invasion capacity in respiratory tissue compared to that in genital tissue at 24 h pi. However, at 24 h pi plaque latitude was found to be larger in genital tissue compared to respiratory tissue and this for all subtypes. These similar findings among the different subtypes take the edge off the belief of the existence of specific mucosa tropisms of different BoHV-1 subtypes.

Detection of bovine herpesvirus 1 and 5 in semen from Brazilian bulls

Bovine herpesvirus 1 (BoHV-1) and 5 (BoHV-5) are important pathogens of the respiratory and genital tract of cattle and may also affect the central nervous system and cause meningoencephalitis. Both virus types are estimated to be widely distributed in Southern Brazil. In the present study, BoHV-1 and/or BoHV-5 DNA were detected in bovine semen samples from two states of Brazil by two species-specific nested polymerase chain reactions (nPCRs). These nPCRs were used to assay 53 samples of fresh semen and 23 samples of frozen semen from breeding bulls. Viral DNA was detected in all 76 semen samples: all were positive for BoHV-5, whereas 34 of these were positive for BoHV-1 as well. Moreover, in five fresh and in 13 frozen semen samples-of a total number of 40 samples suitable for virus isolation-infectious BoHV-1 and/or BoHV-5 virus were detected. In conclusion, that both BoHV-1 and BoHV-5 were detected in bovine semen in Brazil highlighted the importance of examining bull semen in search for both agents to reduce the risk of transmitting these viruses.

Effect of foot-and-mouth disease virus capsid precursor protein and 3C protease expression on bovine herpesvirus 1 replication

Several reports have previously shown that expression of the foot-and-mouth disease virus (FMDV) capsid precursor protein encoding region P1-2A together with the 3C protease (P1-2A/3C) results in correct processing of the capsid precursor into VP0, VP1 and VP3 and formation of FMDV capsid structures that are able to induce a protective immune response against FMDV challenge after immunization using naked DNA constructs or recombinant viruses. To elucidate whether bovine herpesvirus 1 (BHV-1) might also be suitable as a viral vector for empty capsid generation, we aimed to integrate a P1-2A/3C expression cassette into the BHV-1 genome, which, however, failed repeatedly. In contrast, BHV-1 recombinants that expressed an inactive 3C protease or the P1-2A polyprotein alone could be easily generated, although the recombinant that expressed P1-2A exhibited a defect in direct cell-cell spread and release of infectious particles. These results suggested that expression of the original, active FMDV 3C protease is not compatible with BHV-1 replication. This conclusion is supported by the isolation of recombinant BHV-1/3C*, which contained mutations within the 3C ORF (3C* ORF)--probably introduced spontaneously during generation of BHV-1/3C*--instead of the authentic 3C ORF contained in the transfer plasmids. Within the 3C* ORF, the codons for glycine 38 and phenylalanine 48 were both substituted by codons for serine. The resulting 3C* protease exhibits a highly reduced activity for proteolytic processing of the P1-2A polyprotein and thus might be a good candidate for the generation of live attenuated FMDV variants.

Characterization of the nuclear import and export mechanisms of bovine herpesvirus-1 infected cell protein 27

In previous study, we have identified a nuclear localization signal (NLS) and a nucleolar localization signal (NoLS) in bovine herpesvirus-1 (BHV-1) infected cell protein 27 (BICP27), which targets predominantly to the nucleolus. Furthermore, the C-terminal 300 amino acid residues targets exclusively to the cytoplasm, suggesting that BICP27 might contain a nuclear export signal (NES). Amino acid sequence analysis revealed that there is a cluster of leucine-rich residues resembling a NES. Heterokaryon assays demonstrated that BICP27 is capable of shuttling between the nucleus and the cytoplasm of the BHV-1 infected, BICP27 and BICP27-EYFP transfected cells. Deletion mutant analysis revealed that this property is attributed to the leucine-rich NES 299LEELCAARRLSL310. Moreover, the functional NES could mediate transport of a monomer EYFP and a dimer EYFP to the cytoplasm. The nucleocytoplasmic shuttling of BICP27 and the nuclear export of NES-EYFP and NES-dEYFP could be blocked by leptomycin LMB, an inhibitor of the chromosomal region maintenance 1 (CRM1), which is the receptor for exportin-1-dependent nuclear export. In addition, the nuclear import of BICP27 was inhibited by a dominant negative Ran-GTP, namely Ran-GTP Q69L, indicating that BICP27 localized to the nucleus by means of a classic Ran dependent nuclear import mechanism. In conclusion, these results demonstrate that BICP27 shuttles between the nucleus and the cytoplasm by the functional NES and NLS through a CRM1-dependent nuclear export pathway and a Ran dependent nuclear import pathway.

The presence of a deletion sequence in the BHV-1 UL49 homolog in a live attenuated vaccine for infectious bovine rhinotracheitis (IBR)

The difference between the attenuated live vaccine strain 758-43 and its parent virulent strain 758 was investigated genetically. These viruses were propagated in Madin-Darby bovine kidney cells, and viral DNA was obtained from the culture supernatants of the infected cells. Based on a previous report, a large deleted region would seem to exist in the Hind III J fragment located between nucleotide numbers 2439 and 11,270. Three pairs of primers were designed based on the complete BHV-1 DNA sequence. With one pair of primers used, the PCR products derived from strains 758 and LA resulted in fragment sizes of 1850 bp, whereas that from the vaccine strain was smaller than those from the virulent strains. The attenuated live vaccine strain, 758-43, lacked 652 bp in the PCR product region, accounting for approximately 84% of the coding region of the UL49 homolog gene of BHV-1. The present results provide a new and important information to distinguish the vaccine strain 758-43 clearly from wild-type BHV-1 isolates in Japan. The UL49 homolog gene seems to participate in pathogenicity in herpesvirus infections.

Characterization of the nuclear localization and nuclear export signals of bovine herpesvirus 1 VP22

The bovine herpesvirus 1 (BHV-1) tegument protein VP22 is predominantly localized in the nucleus after viral infection. To analyze subcellular localization in the absence of other viral proteins, a plasmid expressing BHV-1 VP22 fused to enhanced yellow fluorescent protein (EYFP) was constructed. The transient expression of VP22 fused to EYFP in COS-7 cells confirmed the predominant nuclear localization of VP22. Analysis of the amino acid sequence of VP22 revealed that it does not have a classical nuclear localization signal (NLS). However, by constructing a series of deletion derivatives, we mapped the nuclear targeting domain of BHV-1 VP22 to amino acids (aa) 121 to 139. Furthermore, a 4-aa motif, 130PRPR133, was able to direct EYFP and an EYFP dimer (dEYFP) or trimer (tEYFP) predominantly into the nucleus, whereas a deletion or mutation of this arginine-rich motif abrogated the nuclear localization property of VP22. Thus, 130PRPR133 is a functional nonclassical NLS. Since we observed that the C-terminal 68 aa of VP22 mediated the cytoplasmic localization of EYFP, an analysis was performed on these C-terminal amino acid sequences, and a leucine-rich motif, 204LDRMLKSAAIRIL216, was detected. Replacement of the leucines in this putative nuclear export signal (NES) with neutral amino acids resulted in an exclusive nuclear localization of VP22. Furthermore, this motif was able to localize EYFP and dEYFP in the cytoplasm, and the nuclear export function of this NES could be blocked by leptomycin B. This demonstrates that this leucine-rich motif is a functional NES. These data represent the first identification of a functional NLS and NES in a herpesvirus VP22 homologue.

Characterization of nuclear localization and export signals of the major tegument protein VP8 of bovine herpesvirus-1

Bovine herpesvirus-1 (BHV-1) VP8 is found in the nucleus immediately after infection. Transient expression of VP8 fused to yellow fluorescent protein (YFP) in COS-7 cells confirmed the nuclear localization of VP8 in the absence of other viral proteins. VP8 has four putative nuclear localization signals (NLS). Deletion of pat4 ((51)RRPR(54)) or pat7 ((48)PRVRRPR(54)) NLS2 abrogated nuclear accumulation, whereas deletion of (48)PRV(50) did not, so pat4 NLS2 is critical for nuclear localization of VP8. Furthermore, NLS1 ((11)RRPRR(15)), pat4 NLS2, and pat7 NLS2 were all capable of transporting the majority of YFP to the nucleus. Finally, a 12-amino-acid peptide with the sequence RRPRRPRVRRPR directed all of YFP into the nucleus, suggesting that reiteration of the RRPR motif makes the nuclear localization more efficient. Heterokaryon assays demonstrated that VP8 is also capable of shuttling between the nucleus and cytoplasm of the cell. Deletion mutant analysis revealed that this property is attributed to a leucine-rich nuclear export sequence (NES) consisting of amino acids (485)LSAYLTLFVAL(495). This leucine-rich NES caused transport of YFP to the cytoplasm. These results demonstrate that VP8 shuttles between the nucleus and cytoplasm.

Recombinant virus-expressed bovine cytokines do not improve efficacy of a bovine herpesvirus 1 marker vaccine strain

Cytokines play a key role as regulators of the immune response. To elucidate whether the efficacy of a live virus vaccine can be improved by co-expression of cytokines, expression cassettes for bovine interleukins (boIL)-2, -4, -6, and -12 and bovine interferon-gamma (boIFN-gamma) were integrated into the glycoprotein E (gE)-locus of the bovine herpesvirus 1 (BHV-1) vaccine virus strain GK/D. Cell culture analyses demonstrated that expression of the cytokines did not impair the replication of the recombinant viruses. To test safety and efficacy, groups of 4-6 months old BHV-1 seronegative calves were vaccinated intranasally with the parental virus strain GK/D or the recombinants, and challenged intranasally 3 weeks later with virulent BHV-1. The animals were monitored for clinical signs, virus excretion and antibody status after vaccination and challenge. All vaccines were well tolerated and protected the immunised calves from clinical disease following challenge, and reduced duration and titres of challenge virus shedding. Calves inoculated with the boIL-6, boIL-12 and boIFN-gamma expressing recombinants showed a significant reduction in vaccine virus shedding but secreted more challenge virus than the other vaccinees. These findings indicate that expression of these cytokines mediates a better control of the vaccine virus replication which, however, interferes with the immunogenicity of the vaccine. In summary, all recombinant viruses were safe and effective, but protection afforded by the recombinants was not improved as compared to vaccination with the parental virus strain GK/D.

The structures of bovine herpesvirus 1 virion and concatemeric DNA: implications for cleavage and packaging of herpesvirus genomes

Herpesvirus genomes are often characterized by the presence of direct and inverted repeats that delineate their grouping into six structural classes. Class D genomes consist of a long (L) segment and a short (S) segment. The latter is flanked by large inverted repeats. DNA replication produces concatemers of head-to-tail linked genomes that are cleaved into unit genomes during the process of packaging DNA into capsids. Packaged class D genomes are an equimolar mixture of two isomers in which S is in either of two orientations, presumably a consequence of homologous recombination between the inverted repeats. The L segment remains predominantly fixed in a prototype (P) orientation; however, low levels of genomes having inverted L (I(L)) segments have been reported for some class D herpesviruses. Inefficient formation of class D I(L) genomes has been attributed to infrequent L segment inversion, but recent detection of frequent inverted L segments in equine herpesvirus 1 concatemers [Virology 229 (1997) 415-420] suggests that the defect may be at the level of cleavage and packaging rather than inversion. In this study, the structures of virion and concatemeric DNA of another class D herpesvirus, bovine herpesvirus 1, were determined. Virion DNA contained low levels of I(L) genomes, whereas concatemeric DNA contained significant amounts of L segments in both P and I(L) orientations. However, concatemeric termini exhibited a preponderance of L termini derived from P isomers which was comparable to the preponderance of P genomes found in virion DNA. Thus, the defect in formation of I(L) genomes appears to lie at the level of concatemer cleavage. These results have important implications for the mechanisms by which herpesvirus DNA cleavage and packaging occur.

Effects of virion host shut-off activity of bovine herpesvirus 1 on MHC class I expression

Previously, we have shown that bovine herpesvirus 1 (BHV-1) down-regulates the expression of major histocompatibility complex class I molecules by interfering with transport of peptides by the transporter associated with antigen processing (TAP). Further studies revealed that BHV-1 down-regulates the expression of mRNA for class I molecules and other cellular proteins. To further elucidate the mechanisms of down-regulation of class I molecules, a virion host shut-off (vhs) deletion mutant was generated. The mutant, like the wildtype (wt) virus, interfered with transport of peptides by the TAP, and down-regulated cell surface expression of class I molecules. However, unlike the wt virus, the mutant did not impair the synthesis of class I molecules. These results indicate that down-regulation of class I molecules by BHV-1 is mediated by vhs activity of the virus, as well as mechanisms specifically directed at the class I pathway. Absence of vhs activity should result in decreased pathogenicity and enhanced immunogenicity of BHV-1 vhs deletion mutant, making it a better vaccine candidate.

Transcriptional and translational expression kinetics of the bovine herpesvirus 1 UL51 homologue gene

We characterized the expression kinetics of the transcript and protein generated from the bovine herpesvirus 1 (BHV1) homologue of the herpes simplex virus 1 (HSV1) UL51 gene. The BHV1 UL51 ORF, located at positions 7236-->7967 of the viral genome, generated a major 1.05 kb transcript accumulating at very low abundance as soon as 3 h post-infection (p.i.), after which its levels increased to reach a plateau from 6 to 12 h p.i., and then slowly decreased up to 24 h p.i. As determined by S1 nuclease protection assays, UL51 transcription initiated at two distinct sites located at 191 and 196 bases upstream from the initiation codon, corresponding to positions 7045 and 7040 of the viral genome, respectively. Western blotting of BHV1-infected protein cell lysates, using a BHV1-specific antiserum generated against a recombinant protein expressed in Escherichia coli, detected a 28 kDa protein of the expected size (24985 Da) whose expression kinetics followed that of its transcript. As evidenced by in situ immunofluorescence assays, the protein mainly localized to the cytoplasm and the perinuclear region of infected cells. In contrast to HSV1 UL51 which is classified as a gamma2 gene, BHV1 UL51 belongs to viral genes of the gamma1 class as expression of its transcript is partially dependent on viral DNA synthesis.

Expression kinetics of the transcript and product of the UL28 homologue of bovine herpesvirus 1

We report that the bovine herpesvirus 1 (BHV1) UL28 ORF, a homologue of the herpes simplex virus (HSV) UL28 gene, represents a functional gene encoding a viral specific protein. The BHV1 UL28 ORF, located at positions 53058-->55538 of the viral genome, encodes a viral specific transcript of 3.4 kb detected at 6 h post-infection (p.i.) after which its levels accumulated up to 12 h p.i. and then remained constant up to 24 h p.i. Transcription of the BHV1 UL28 was determined to initiate 95 bases upstream from the ORF's initiating codon, which corresponds to 33 nucleotides downstream from a putative TATA box. A BHV1 UL28 specific antiserum, generated against a T7-Tag/UL28 fusion protein expressed in E. coli, specifically reacted with a 100 kDa protein in Western blots of BHV1-infected protein cell lysates. The expression kinetics of the protein was delayed by 6 h relative to that of its transcript suggesting that the gene is regulated at the translational level. In contrast to the HSV and pseudorabies virus UL28 genes, which belong to viral genes of the early (beta) class, that of BHV1 was unambiguously classified as a gamma2 gene. Further studies will be required to determine whether these kinetic differences have any functional implications.

Tyrosine phosphorylation of bovine herpesvirus 1 tegument protein VP22 correlates with the incorporation of VP22 into virions

Tyrosine phosphorylation has been shown to play a role in the replication of several herpesviruses. In this report, we demonstrate that bovine herpesvirus 1 infection triggered tyrosine phosphorylation of proteins with molecular masses similar to those of phosphorylated viral structural proteins. One of the tyrosine-phosphorylated viral structural proteins was the tegument protein VP22. A tyrosine 38-to-phenylalanine mutation totally abolished the phosphorylation of VP22 in transfected cells. However, construction of a VP22 tyrosine 38-to-phenylalanine mutant virus demonstrated that VP22 was still phosphorylated but that the phosphorylation site may change to the C terminus rather than be in the N terminus as in wild-type VP22. In addition, the loss of VP22 tyrosine phosphorylation correlated with reduced incorporation of VP22 compared to that of envelope glycoprotein D in the mutant viruses but not with the amount of VP22 produced during virus infection. Our data suggest that tyrosine phosphorylation of VP22 plays a role in virion assembly.

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.

Expression of bovine viral diarrhoea virus glycoprotein E2 by bovine herpesvirus-1 from a synthetic ORF and incorporation of E2 into recombinant virions

Expression cassettes containing the codons for the pestivirus E (rns) signal peptide (Sig) followed by a chemically synthesized ORF that encoded the bovine viral diarrhoea virus (BVDV) strain C86 glycoprotein E2, a class I membrane glycoprotein, were constructed with and without a chimeric intron sequence immediately upstream of the translation start codon, and incorporated into the genome of bovine herpesvirus-1 (BHV-1). The resulting recombinants, BHV- 1/SigE2(syn) and BHV-1/SigE2(syn)-intron, expressed comparable quantities of glycoprotein E2, and Northern blot hybridizations indicated that the presence of the intron did not increase significantly the steady-state levels of transcripts encompassing the SigE2(syn) ORF. In BHV-1/SigE2(syn)- infected cells, the 54 kDa E2 glycoprotein formed a dimer with an apparent molecular mass of 94 kDa, which was further modified to a 101 kDa form found in the envelope of recombinant virus particles. Penetration kinetics and single-step growth curves indicated that the incorporation of the BVDV E2 glycoprotein in the BHV-1 envelope, which apparently did not require BHV-1-specific signals, interfered with entry into target cells and egress of progeny virions. These results demonstrate that a pestivirus glycoprotein can be expressed efficiently by BHV-1 and incorporated into the viral envelope. BHV-1 thus represents a promising tool for the development of efficacious live and inactivated BHV-1-based vector vaccines.

Immunogenicity and protective efficacy of a gE, gG and US2 gene-deleted bovine herpesvirus-1 (BHV-1) vaccine

The efficacy and safety of a gene-deleted bovine herpesvirus-1 (BHV-1) vaccine was determined in a bovine herpesvirus challenge trial in calves. Three different doses of the vaccine were administered intramuscularly at 10(5), 10(6) and 10(7) PFU/ml and compared to a commercial vaccine and non vaccinated control calves. Challenge was performed by intranasal aerosolization with the Cooper strain of BHV-1 (3 x 10(4) PFU/ml). The non-vaccinated calves shed significantly (P < 0.05) more virus than all other groups on days 4, 8 and 10 post challenge. By day 14 post challenge, antibody titers for BHV-1 of calves vaccinated with 10(7) PFU/ml were significantly (P < 0.05) higher than the commercial or non-vaccinated calves. Clinical scores of non-vaccinated calves were significantly (P < 0.05) higher than all other groups on days 4-14 post challenge. With both radioimmunoprecipitation and competitive enzyme-linked immunosorbent assays (C-ELISA), calves in the gene-deleted vaccine groups mounted comparable specific responses against gB, gC and gD post vaccination as calves in the commercial vaccine group, but in a dose dependent manner. These data suggest that the gene-deleted BHV-1 vaccine tested may be used as an effective vaccine in controlling BHV-1 infections.

BHV-1: new molecular approaches to control a common and widespread infection

BACKGROUND

Herpesviruses are widespread viruses, causing severe infections in both humans and animals. Eradication of herpesviruses is extremely difficult because of their ability to establish latent and life-long infections. However, latency is only one tool that has evolved in herpesviruses to successfully infect their hosts; such viruses display a wide (and still incompletely known) panoply of genes and proteins that are able to counteract immune responses of their hosts. Envelope glycoproteins and cytokine inhibitors are two examples of such weapons. All of these factors make it difficult to develop diagnostics and vaccines, unless they are based on molecular techniques.

MATERIALS AND METHODS

Animal herpesviruses, because of their striking similarity to human ones, are suitable models to study the molecular biology of herpesviruses and develop strategies aimed at designing neurotropic live vectors for gene therapy as well as engineered attenuated vaccines.

RESULTS

BHV-1 is a neurotropic herpesvirus causing infectious rhinotracheitis (IBR) in cattle. It is a major plague in zootechnics and commercial trade, because of its ability to spread through asymptomatic carrier animals, frozen semen, and embryos. Such portals of infections are also important for human herpesviruses, which mainly cause systemic, eye, and genital tract infections, leading even to the development of cancer.

CONCLUSIONS

This review covers both the genetics and molecular biology of BHV-1 and its related herpesviruses. Epidemiology and diagnostic approaches to herpesvirus infections are presented. The role of herpesviruses in gene therapy and a broad introduction to classic and engineered vaccines against herpesviruses are also provided. http://link.springer-ny. com/link/service/journals/00020/bibs/5n5p261.html

Bovine herpes virus expressing envelope protein (E2) of bovine viral diarrhea virus as a vaccine candidate

The gene encoding the envelope protein (E2) of bovine viral diarrhea virus (BVDV) was expressed under the thymidine kinase (TK) promoter of Korean bovine herpesvirus 1 (BHV-1) isolate. Thymidine kinase negative (TK-) BHV-1 recombinants expressing E2 of BVDV were constructed and the expression of E2 was identified by immunofluorescence and Western blotting. Compared to wild type BHV-1, the recombinant BHV-1 had a delayed cytopathogenic effect in cells. The immunogenicity of the recombinant BHV-1 was examined in guinea pigs and cattle. Although an increase in body temperature was detected for a few days, the inoculated cattle returned to normal temperature with the development of neutralizing antibodies to BVDV.

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.

The class II membrane glycoprotein G of bovine respiratory syncytial virus, expressed from a synthetic open reading frame, is incorporated into virions of recombinant bovine herpesvirus 1

The bovine herpesvirus 1 (BHV-1) recombinants BHV-1/eG(ori) and BHV-1/eG(syn) were isolated after insertion of expression cassettes which contained either a genomic RNA-derived cDNA fragment (BHV-1/eG(ori)) or a modified, chemically synthesized open reading frame (ORF) (BHV-1/eG(syn)), which both encode the attachment glycoprotein G of bovine respiratory syncytial virus (BRSV), a class II membrane glycoprotein. Northern blot analyses and nuclear runoff transcription experiments indicated that transcripts encompassing the authentic BRSV G ORF were unstable in the nucleus of BHV-1/eG(ori)-infected cells. In contrast, high levels of BRSV G RNA were detected in BHV-1/eG(syn)-infected cells. Immunoblots showed that the BHV-1/eG(syn)-expressed BRSV G glycoprotein contains N- and O-linked carbohydrates and that it is incorporated into the membrane of infected cells and into the envelope of BHV-1/eG(syn) virions. The latter was also demonstrated by neutralization of BHV-1/eG(syn) infectivity by monoclonal antibodies or polyclonal anti-BRSV G antisera and complement. Our results show that expression of the BRSV G glycoprotein by BHV-1 was dependent on the modification of the BRSV G ORF and indicate that incorporation of class II membrane glycoproteins into BHV-1 virions does not necessarily require BHV-1-specific signals. This raises the possibility of targeting heterologous polypeptides to the viral envelope, which might enable the construction of BHV-1 recombinants with new biological properties and the development of improved BHV-1-based live and inactivated vector vaccines.

Functional expression of the bovine herpesvirus 1 alkaline deoxyribonuclease (UL12) in Escherichia coli

Sequence analysis within the unique long segment of the bovine herpesvirus 1 (BHV-1; infectious bovine rhinotracheitis virus) genome identified an open reading frame whose deduced protein product of 487 amino acids exhibited homology to alkaline deoxyribonucleases (DNases) of other herpesviruses. To determine this BHV-1 gene product has nuclease activity, the gene designated UL12 was inserted into the vector pET-28a(+) and expressed in Escherichia coli as an oligohistidine-tagged protein. Upon induction with isopropyl beta-D-thiogalactopyranoside E. coli BL21 (DE3) [pLysS] cells carrying this recombinant plasmid produced a 57-kDa protein, the molecular mass of which was in accordance with the prediction from the DNA sequence. The recombinant UL12 protein purified by nickel-chelating affinity chromatography exhibited both exonuclease and endonuclease activity, each with an alkaline pH optimum.

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.

Infectious bovine rhinotracheitis, parainfluenza-3, and respiratory coronavirus

A number of viruses have been proven to be primary respiratory pathogens of cattle. Viruses may play an important role in making cattle susceptible to secondary respiratory bacterial pathogens. Epidemiology, pathogenesis, laboratory diagnosis, and important properties in infectious bovine rhinotracheitis (IBR), parainfluenza-3 (PI-3), and bovine respiratory coronavirus (BRCV) are described in this article.

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.

Purification of the infectious bovine rhinotracheitis virus alkaline deoxyribonuclease expressed in Escherichia coli

Nucleotide sequence analysis within the unique long segment of the infectious bovine rhinotracheitis virus (IBRV) genome identified an open reading frame of 1461 base pairs whose deduced polypeptide of 487 amino acids exhibited homology to alkaline deoxyribonucleases of other herpesviruses. To determine whether this IBRV gene product has nuclease activity, the gene designated UL12 was inserted into the vector pET-28a(+) and expressed in Escherichia coli as an oligohistidine-tagged protein. Upon induction with isopropyl beta-D-thiogalactopyranoside E. coli BL21 (DE3)[pLysS] cells harboring this recombinant plasmid produced a 57-kDa protein, the molecular mass of which was in accordance with the prediction from the nucleotide sequence. A one-step purification procedure using metal affinity chromatography resulted in a homogeneous preparation of this recombinant protein. The purified protein exhibited both exonuclease and endonuclease activities, each with an alkaline pH optimum.

From essential to beneficial: glycoprotein D loses importance for replication of bovine herpesvirus 1 in cell culture

Glycoprotein D (gD) of bovine herpesvirus 1 (BHV-1) has been shown to be an essential component of virions involved in virus entry. gD expression in infected cells is also required for direct cell-to-cell spread. Therefore, BHV-1 gD functions are identical in these aspects to those of herpes simplex virus 1 (HSV-1) gD. In contrast, the gD homolog of pseudorabies virus (PrV), although essential for penetration, is not necessary for direct cell-to-cell spread. Cocultivation of cells infected with phenotypically gD-complemented gD- mutant BHV-1/80-221 with noncomplementing cells resulted in the isolation of the cell-to-cell-spreading gD-negative mutant ctcs+BHV-1/80-221, which was present in the gD-null BIV-1 stocks. ctcs+BHV-1/80-221 could be propagated only by mixing infected with uninfected cells, and virions released into the culture medium were noninfectious. Marker rescue experiments revealed that a single point mutation in the first position of codon 450 of the glycoprotein H open reading frame, resulting in a glycine-to-tryptophan exchange, enabled complementation of the gD function for cell-to-cell spread. After about 40 continuous passages of ctcs+BHV-1/80-221-infected cells with noninfected cells, the plaque morphology in the cultures started to change from roundish to comet shaped. Cells from such plaques produced infectious gD- virus, named gD-infBHV-1, which entered cells much more slowly than wild-type BHV-1. In contrast, integration of the gD gene into the genomes of gD-infBHV-1 and ctcs+BHV-1/80-221 resulted in recombinants with accelerated penetration in comparison to wild-type virions. In summary, our results demonstrate that under selective conditions, the function of BHV-1 gD for direct cell-to-cell spread and entry into cells can be compensated for by mutations in other viral (glyco)proteins, leading to the hypothesis that gD is involved in formation of penetration-mediating complexes in the viral envelope of which gH is a component. Together with results for PrV, varicella-zoster virus, which lacks a gD homolog, and Marek's disease virus, whose gD homolog is not essential for infectivity, our data may open new insights into the evolution of alphaherpesviruses.

A contribution to the systematization of bovine herpesvirus 1 based on genomic mapping by restriction fragment pattern analysis

Fourteen isolates of bovine herpesvirus 1 (BHV-1) found representative of more than 100 isolates studied, were compared by restriction fragment pattern analyses and molecularly characterized. A number of evolutionary links between the variants originally associated with infectious bovine rhinotracheitis and the variants originally associated with infectious pustular vulvovaginitis were identified. These findings, as well as the lack of any correlation between genome type and clinical manifestation, confirm that there is no phylogenetic basis for a distinction between groups of strains associated with genital and respiratory disease. Two attenuated vaccine strains can be identified as deviating from field isolates.

Population dynamics of bovine herpesvirus 1 infection in a dairy herd

An induced outbreak of a bovine herpesvirus 1 (BHV1) infection in a dairy herd is described. The outbreak was induced by injecting three BHV1 seropositive cows with dexamethasone. Within 7 weeks all seronegative cows had seroconverted. Also some seropositive animals showed a significant increase in serum antibody titre. Using these data, parameters of population dynamics such as R0, the basic reproduction ratio, could be estimated. The basic reproduction ratio is a threshold value describing infection dynamics in a population. This parameter is defined as the average number of secondary cases generated by one primary case in a wholly susceptible population of defined density. In this population R0 was estimated to be at least 7. The importance of these findings, and implications for eradication of BHV1 are discussed.

Molecular virology of ruminant herpesviruses

Molecular virology has served to establish bovine herpesvirus 1 (BHV-1) as the prototype member of ruminant herpesviruses. Based on the genomic sequence of the virus, we aim to identify and characterize virus-specified components, to explain their concerted action, and to predict how the chain of events during the lytic and latent phases of the viral life cycle may be interrupted. The nucleotide sequence of the BHV-1 genome (136 kb) has just been completed by international cooperation (July 1995; except for a small gap in UL36). It comprises 67 unique genes and 2 genes, both duplicated, in the inverted repeats. In general, these genes exhibit strong homology at the amino acid sequence level to those of other alphaherpesviruses (HSV-1, VZV, EHV-1) and are arranged in similar order. A few genes are peculiar to only one or two herpesviruses, e.g. in BHV-1 the circ, UL0.5, UL3.5 and US1.5 genes. Not long ago, the repertoire of BHV-1 proteins under study was restricted to the three major glycoproteins (gB, gC, and gD) and thymidine kinase. The repertoire is now growing rapidly and includes 7 additional glycoproteins (gE, gI, gH, gL, gG, gK and gM), a number of enzymes (e.g. ribonucleotide reductase, DNA Polymerase, dUTPase), and a group of regulatory proteins (BICPO, 4, 22, and 27, alpha TIF). Investigations into the functions of these proteins and comparison with their counterparts in other herpesviruses should reveal which are useful targets for diagnosis, prevention or antiviral treatment. Recombinant viruses containing deletions or replacements of individual genes are being created, aiming at vaccine development and insights into pathogenesis, notably latency, neurotropism, and interference with host functions. Molecular analysis of other ruminant herpesviruses is much less advanced. Over a dozen virus species have been described; most share basic properties with BHV-1 and may be classified as alphaherpesviruses. The gammaherpesviruses are represented by the proposed agent of malignant catarrhal fever, alcelaphine herpesvirus 1, and by bovine herpesvirus 4, whose partial sequences exhibit similarity to herpesvirus saimiri.

Glycoprotein E of bovine herpesvirus type 1 is involved in virus transmission by direct cell-to-cell spread

In order to identify the role of the bovine herpesvirus type 1 (BHV-1) glycoprotein E (gE) in the viral infection cycle, we have constructed a BHV-1 gE deletion mutant strain (BHV-1 gE-). This strain was assayed in vitro by comparing its growth kinetics with the wild type strain used as a host of the deletion. Our results indicate that those conditions which prevent the infection by direct adsorption to the cells (presence of a semi-solid medium or presence of neutralizing antibodies in the medium) selectively inhibit the growth of the gE- strain, suggesting that gE plays a central role in the BHV-1 spread by direct cell-to-cell transmission, a major mechanism of the BHV-1 in vivo virulence.

Construction and characterization of an attenuated bovine herpesvirus type 1 (BHV-1) recombinant virus

A recombinant bovine herpesvirus type 1 (BHV-1) virus (Gal-TK) has been constructed. The Gal-TK virus contains a chimeric reporter/marker gene coding for bacterial beta-galactosidase (beta-gal gene) that was inserted stably within the viral TK gene. This resulted in inactivation of the TK gene. The beta-gal gene is under the regulation of a strong, human cytomegalovirus-immediate early (HCMV-IE) promoter and is expressed as an authentic viral-coded gene. Even though the one-step growth kinetics of the recombinant and parent viruses were similar, the recombinant virus yielded less than the parent virus on Madin-Darby bovine kidney cells. After intranasal inoculation, the engineered virus was virtually avirulent for colostrum-deprived new-born calves. Similar to the parent virus, the recombinant virus replicated in the upper respiratory tract of calves, but the amount of progeny viruses produced was reduced significantly. The progeny viruses recovered from nasal swabs of animals inoculated with the recombinant and the Cooper strains of BHV-1 were easily distinguishable based on the beta-gal marker.

Bovine herpesvirus 1 U(s) open reading frame 4 encodes a glycoproteoglycan

Sequence analysis of the short unique (Us) segment of the bovine herpesvirus 1 (BHV-1) genome predicted that the Us open reading frame (ORF) 4 encodes a protein with homology to glycoprotein G (gG) of other alpha-herpesviruses (P. Leung-Tack, J.-C. Audonnet, and M. Riviere, Virology 199:409-421, 1994). RNA analysis showed that the Us ORF4 is contained within two transcripts of 3.5 and 1.8 kb. The 3.5 kb RNA represents a structurally bicistronic RNA which encompasses the Us ORF3 and Us ORF4, whereas the 1.8-kb RNA constitutes the monocistronic Us ORF4 mRNA. To identify the predicted BHV-I gG, recombinant vaccinia virus expressing the Us ORF4 was used to raise specific antibodies in rabbits. The antiserum recognized a 65-kDa polypeptide and a very diffusely migrating species of proteins with an apparent molecular mass of between 90 and greater than 240 kDa in supernatants of BHV-1-infected cells which was also precipitated together with 61- and 70-kDa polypeptides from cell-associated proteins. The specificity of the reaction was demonstrated by the absence of these proteins from the supernatant of cells infected with the Us ORF4 deletion mutant BHV-l/gp1-8. Treatment of the immunoprecipitated proteins with glycosidases and chondroitinase AC showed that the 65-kDa protein constitutes gG, which contains both N- and O-linked carbohydrates, and that the high-molecular-mass proteins contain glycosaminoglycans linked to a 65-kDa glycoprotein that is antigenically related to gG. These molecules were therefore named glycoproteoglycan C (gpgG). Pulse chase experiments indicated that gG and gpgG were processed from a common precursor molecule with an apparent molecular mass of 61 kDa via a 70-kDa intermediate. Both gG and gpgG could not be found associated with purified virions. In summary, our results identify the BHV-I gG protein and demonstrate the presence of a form of posttranslational modification, glycosamino-glycosylation, that has not yet been described for a herpesvirus-encoded protein.

Sequence and expression of a bovine herpesvirus-1 gene homologous to the glycoprotein K-encoding gene of herpes simplex virus-1

In the bovine herpes virus-1 (BHV-1) genome, a gene equivalent to the glycoprotein k (gK)-encoding gene of other herpesviruses was identified and sequenced. The primary translation product is predicted to comprise 338 amino acids (aa) and to exhibit a molecular mass of 37.5 kDa. It possesses characteristics typical for membrane glycoproteins including a potential cleavable signal sequence, three transmembrane domains and two potential N-linked glycosylation sites. Comparison to the gK proteins of the other herpesviruses revealed aa sequence homologies of 46, 44, 53, 43, and 46% with the gK counterparts of herpes simplex viruses-1 and 2 (HSV-1 and 2), equine herpesvirus-1 (EHV-1), Marek's disease virus (MDV) and varicella zoster virus (VZV), respectively. A 30-kDa primary translation product was identified following in vitro translation of in vitro transcribed mRNA. When canine microsomal membranes were added to the translation reaction, a 38-kDa glycosylated protein was detected. Treatment with endoglycosidase F or H (endo or H) removed the glycosyl groups and reduced the apparent molecular mass of the 38-kDa glycoprotein.

Identification and characterization of the bovine herpesvirus 1 UL7 gene and gene product which are not essential for virus replication in cell culture

The UL7 gene of bovine herpesvirus 1 (BHV-1) strain Schönböken was found at a position and in a context predicted from the gene order in the prototype alphaherpesvirus herpes simplex virus type 1. The gene and flanking regions were sequenced, the UL7 RNA and protein were characterized, and 98.3% of the UL7 open reading frame was deleted from the viral genome without destroying productive virus replication. Concomitant deletion of nine 3' codons from the BHV-1 UL6 ORF and 77 amino acids from the carboxy terminus of the predicted BHV-1 UL8 protein demonstrated that these domains are also not essential for function of the respective proteins. The UL7 open reading frame encodes a protein of 300 amino acids with a calculated molecular mass of 32 kDa. Comparison with UL7 homologs of other alphaherpesviruses revealed a high degree of homology, the most prominent being to the predicted UL7 polypeptide of varicella-zoster virus, with 43.3% identical amino acids. A monospecific anti-UL7 serum identified the 33-kDa (apparent-molecular-mass) UL7 polypeptide which is translated from an early-expressed 1.7-kb RNA. The UL7 protein was localized in the cytoplasm of infected cells and could not be detected in purified virions. In summary, we describe the first identification of an alphaherpesviral UL7-encoded polypeptide and demonstrate that the UL7 protein is not essential for replication of BHV-1 in cell culture.

The bovine herpesvirus type 1 major tegument protein VP8 expressed in recombinant vaccinia virus does not induce significant immunity in mice

We previously reported the characterization of the gene encoding the bovine herpesvirus type 1 (BHV-1) major tegument protein VP8. With the aim of defining the immunological properties of this protein, we constructed a recombinant vaccinia virus (VV-VP8) in which expression of the VP8 gene was regulated by the P7.5 early/late promoter. Since the sequence of the VP8 gene contained a TTTTTNT motif known to serve as a transcription termination signal of vaccinia virus genes of the early class, a second recombinant (VV-VP8-Mut) in which this signal was modified by site-directed mutagenesis was created. Characterization of the recombinant viruses revealed that truncated VP8 mRNA and protein (69 kDa) were synthesized in VV-VP8 infected cells, whereas cells infected with VV-VP8-Mut produced a protein which was undistinguishable from that of the BHV-1 encoded protein (92-94 kDa). Immunization of BALB/c mice (H-2d) with VV-VP8-Mut induced a low VP8-specific antibody response whereas no specific response was induced in VV-VP8 inoculated mice. The low humoral response elicited was similar in C57BL/6 (H-2b) and C3H (H-2k) mice. Furthermore, immunization of mice with VV-VP8-Mut did not induce a BHV-1-specific lymphoproliferation in the three mice strains examined. Our results contrast with a recent study showing that immunization of calves with purified VP8 stimulated both T cell proliferation and antibody production.

Construction of bovine herpesvirus-1 (BHV-1) recombinants which express pseudorabies virus (PRV) glycoproteins gB, gC, gD, and gE

We have improved the method for constructing recombinants of bovine herpesvirus type-1 (BHV-1). Using this method, we constructed three recombinants in which the pseudorabies virus (PRV) thymidine kinase (tk) gene was inserted at three different sites in the unique short region of BHV-1. These three sites are located in the open reading frame of gE, gG and gI genes. Previously, two sites (tk and gC) had been used to insert foreign DNA fragments to BHV-1 genome. Therefore we now have 5 sites in BHV-1 where DNA can be inserted. The gB, gC, gD, gE and gI genes of PRV were successfully inserted at the tk or the gC gene of BHV-1 genome and Western blot analyses confirmed that the recombinants express PRV gB, gC, gD and gE. Anti-PRV gB and gC antibodies as well as anti-PRV polyclonal serum neutralized BHV-1 recombinants which express PRV gB and gC. The latter was neutralized more strongly. However, anti-gD monoclonal antibody and anti-PRV polyclonal serum failed to neutralize gD-expressing recombinants. This suggests that PRV gC and some gB are integrated into the viral envelope of the recombinants, but very little gD is present in the viral envelope.

The UL2 open reading frame of bovine herpesvirus 1 encodes a uracil-DNA glycosylase

Sequence analysis within the unique long segment of the bovine herpesvirus 1 (BHV-1) genome previously identified an open reading frame (ORF), designated UL2, whose deduced polypeptide of 204 amino acids contained a consensus uracil-DNA glycosylase (UDGase) signature sequence. To determine whether the BHV-1 UL2 ORF product has UDGase activity, we positioned the UL2 sequence down-stream of the T7 promoter on the vector pET-28b(+) and expressed it in Escherichia coli. Upon induction with isopropyl beta-D-thiogalactopyranoside these cells produced a 23-kDa protein, the molecular mass of which was in accordance with the prediction from the nucleotide sequence. A one-step purification procedure using nickel-chelating affinity chromatography resulted in a homogeneous preparation of this protein, which displayed specific UDGase activity in an in vitro enzyme assay. These results provide evidence that the BHV-1 UL2 gene does encode a UDGase.

Bovine herpesvirus 1 isolates contain variable copy numbers of GC-rich tandem repeats in the gI non-coding regions of their genomes

A polymerase chain reaction (PCR) targeted to the central portion of the bovine herpesvirus 1 (BHV1) genome, and overlapping the 3' untranslated end of the gI glycoprotein, was used to amplify BHV1 genomic sequences. PCR products generated from cell cultures infected with BHV1.1 were consistently smaller than the corresponding products from cells infected with BHV1.2. The nature of the sequence differences between these isolates within the target region was found to be a consequence of variable numbers of small GC rich repeats, particularly the sequence 5'-G(A/T)CC-3', present in the region downstream of the gI coding region. Based on these differences a modified PCR protocol which readily discriminated between several BHV1.1 and BHV1.2 strains was devised.

Molecular basis of antigenic variation between the glycoproteins C of respiratory bovine herpesvirus 1 (BHV-1) and neurovirulent BHV-5

Herpesvirus glycoprotein C (gC) functions as a major virus attachment protein. The gC sequence of the neurovirulent bovine herpesvirus type 5 (BHV-5) virus was determined and compared with the gC sequence of the nonneurovirulent BHV-1. Alignment of the predicted amino acid sequences of BHV-1 and BHV-5 gC ORFs showed that the amino-terminal third of the protein differed between the two viruses. Whole or subgenomic fragments of gC coding regions from both viruses were expressed as trpE-gC fusion proteins in Escherichia coli to map linear epitopes defined by type-specific murine monoclonal antibodies (MAbs). Based on the reactivity of BHV-1-specific MAbs with the recombinant proteins, two epitopes were mapped between BHV-1 gC residues 22 and 172. Undirectional deletion of these residues at the carboxy end mapped one within residues 22-69 and the other within residues 103-122. Two BHV-5-specific MAbs identified an epitope coding region within BHV-5 gC residues 31-78. Bovine antisera against BHV-1 and BHV-5 showed specificity to BHV-1 gC residues 22-69 and to BHV-5 gC residues 31-78, respectively, in a type-specific manner.

The bovine herpesvirus 1 maturational proteinase and scaffold proteins can substitute for the homologous herpes simplex virus type 1 proteins in the formation of hybrid type B capsids

We determined the nucleotide sequence of a 3.5-kb region of the bovine herpesvirus 1 (BHV-1) genome which contained the complete BHV-1 homologs of the herpes simplex virus type 1 (HSV-1) UL26 and UL26.5 genes. In HSV-1, the UL26 and UL26.5 open reading frames encode scaffold proteins upon which viral capsids are assembled. The UL26-encoded protein is also a proteinase and specifically cleaves both itself and the UL26.5-encoded protein. The overall BHV-1-encoded amino acid sequence showed only 41% identity to the HSV-1 sequences and was most divergent in the regions defined to be involved in the scaffolding function. We substituted the proteins encoded by the BHV-1 homologs of the UL26 and UL26.5 open reading frames, expressed in baculovirus, for the corresponding HSV-1 proteins in an in vitro HSV-1 capsid assembly system. The proteins expressed from the BHV-1 UL26 and UL26.5 homologs facilitated the formation of hybrid type B capsids indistinguishable from those formed entirely with HSV-1-encoded proteins.