Evolution of Bovine herpesvirus 4: recombination and transmission between African buffalo and cattle

Identification and phylogenetic analysis of bovine herpesvirus 4 isolated from aborted bovine foetuses in Türkiye

Bovine herpesvirus 4 (BoHV-4) is responsible for reproductive disorders and abortions in cattle. The aim of this study was to investigate the potential role of BoHV-4 in abortions in dairy cows when the possible aetiological cause could not be determined in Türkiye. The study also provided the molecular characterization of BoHV-4 strains based on the gB gene. In this study, foetuses (n = 188) and serum (n = 50) were retrospectively used for PCR and indirect ELISA assays, respectively. In addition, foetuses with BoHV-4 were tested for the isolation of the BoHV-4 strain in MDBK cell culture. The BoHV-4 gB gene was detected in the brain, liver, lung, kidney, and spleen tissues of three foetuses out of 188 aborted foetuses. The BoHV-4 strain was isolated from the kidney of one foetus in MDBK cell culture. The three aborted foetuses were from different cows in the same herd in 2021. On this dairy farm, the BoHV-4 seroprevalence rate in cattle with a history of abortion was 96% (48/50). Phylogenetic analysis revealed that the detected strains belong to genotype II. The present study shows that the impact of BoHV-4 on abortions in cattle should not be ignored. It can therefore be informative to focus on BoHV-4 in routine laboratory diagnostics for abortions without a proven aetiology or in cattle herds that have previously been infected with BoHV-4.

Isolation and complete genomic characterization of a Movar 33/63-like Japanese bovine herpesvirus 4 from a calf with respiratory disease

Bovine herpesvirus 4 (BoHV-4) is an indigenous virus in cattle prevalent mainly in North and South American countries and European countries, but the genomic sequences and genetic characteristics of Japanese strains have not been reported. BoHV-4 is suspected, but not proven, to be associated with various diseases. In the present study, we isolated BoHV-4 from a 10-month-old Japanese Black calf with respiratory symptoms in Japan. To identify the genetic characteristics of the isolate named strain SG20, complete genome sequencing was performed using a combination of next-generation and Sanger sequencing technologies. The complete long unique coding region (LUR) of SG20 was found to comprise 108,819 nucleotides with 41.4% GC content and contain at least 78 open reading frames. It shares 83.4 to 99.3% overall nucleotide identity with six BoHV-4 strains available in the database. The deduced amino acid sequence alignment revealed that SG20 contains genotype 1-specific features of BoHV-4, such as amino acid substitutions and insertions within the glycoprotein B region. Phylogenetic analyzes based on the nucleotide sequences of ORF20 indicated that the virus belonged to genotype 1 (Movar 33/63-like group). The strain was also analyzed using the complete LUR and placed in the same clade as a strain recently isolated from China, but it was distinct from American and European BoHV-4 strains of genotype 1. Although further genomic and epidemiologic information is needed, our results help elucidate the molecular epidemiology of BoHV-4 and provide a foundation for future studies.

Whole Genome Sequence-Based Analysis of Bovine Gammaherpesvirus 4 Isolated from Bovine Abortions

Bovine gammaherpesvirus 4 (BoGHV4) is a member of the Gammaherspivirinae subfamily, Rhadinovirus genus. Its natural host is the bovine, and it is prevalent among the global cattle population. Although the complete genome of BoGHV4 has been successfully sequenced, the functions of most of its genes remain unknown. Currently, only six strains of BoGHV4, all belonging to Genotype 1, have been sequenced. This is the first report of the nearly complete genome of Argentinean BoGHV4 strains isolated from clinical cases of abortion, representing the first BoGHV4 Genotype 2 and 3 genomes described in the literature. Both Argentinean isolates presented the highest nt p-distance values, indicating a greater level of divergence. Overall, the considerable diversity observed in the complete genomes and open reading frames underscores the distinctiveness of both Argentinean isolates compared to the existing BoGHV4 genomes. These findings support previous studies that categorized the Argentinean BoGHV4 strains 07-435 and 10-154 as Genotypes 3 and 2, respectively. The inclusion of these sequences represents a significant expansion to the currently limited pool of BoGHV4 genomes while providing an important basis to increase the knowledge of local isolates.

An attenuated herpesvirus vectored vaccine candidate induces T-cell responses against highly conserved porcine reproductive and respiratory syndrome virus M and NSP5 proteins that are unable to control infection

Porcine reproductive and respiratory syndrome virus (PRRSV) remains a leading cause of economic loss in pig farming worldwide. Existing commercial vaccines, all based on modified live or inactivated PRRSV, fail to provide effective immunity against the highly diverse circulating strains of both PRRSV-1 and PRRSV-2. Therefore, there is an urgent need to develop more effective and broadly active PRRSV vaccines. In the absence of neutralizing antibodies, T cells are thought to play a central role in controlling PRRSV infection. Herpesvirus-based vectors are novel vaccine platforms capable of inducing high levels of T cells against encoded heterologous antigens. Therefore, the aim of this study was to assess the immunogenicity and efficacy of an attenuated herpesvirus-based vector (bovine herpesvirus-4; BoHV-4) expressing a fusion protein comprising two well-characterized PRRSV-1 T-cell antigens (M and NSP5). Prime-boost immunization of pigs with BoHV-4 expressing the M and NSP5 fusion protein (vector designated BoHV-4-M-NSP5) induced strong IFN-γ responses, as assessed by ELISpot assays of peripheral blood mononuclear cells (PBMC) stimulated with a pool of peptides representing PRRSV-1 M and NSP5. The responses were closely mirrored by spontaneous IFN-γ release from unstimulated cells, albeit at lower levels. A lower frequency of M and NSP5 specific IFN-γ responding cells was induced following a single dose of BoHV-4-M-NSP5 vector. Restimulation using M and NSP5 peptides from PRRSV-2 demonstrated a high level of cross-reactivity. Vaccination with BoHV-4-M-NSP5 did not affect viral loads in either the blood or lungs following challenge with the two heterologous PRRSV-1 strains. However, the BoHV-4-M-NSP5 prime-boost vaccination showed a marked trend toward reduced lung pathology following PRRSV-1 challenge. The limited effect of T cells on PRRSV-1 viral load was further examined by analyzing local and circulating T-cell responses using intracellular cytokine staining and proliferation assays. The results from this study suggest that vaccine-primed T-cell responses may have helped in the control of PRRSV-1 associated tissue damage, but had a minimal, if any, effect on controlling PRRSV-1 viral loads. Together, these results indicate that future efforts to develop effective PRRSV vaccines should focus on achieving a balanced T-cell and antibody response.

Characterization of BoHV-4 ORF45

Bovine herpesvirus 4 (BoHV-4) is a Gammaherpesvirus belonging to the Rhadinovirus genus. The bovine is BoHV-4's natural host, and the African buffalo is BoHV-4's natural reservoir. In any case, BoHV-4 infection is not associated with a specific disease. Genome structure and genes are well-conserved in Gammaherpesvirus, and the orf 45 gene and its product, ORF45, are one of those. BoHV-4 ORF45 has been suggested to be a tegument protein; however, its structure and function have not yet been experimentally characterized. The present study shows that BoHV-4 ORF45, despite its poor homology with other characterized Rhadinovirus ORF45s, is structurally related to Kaposi's sarcoma-associated herpesvirus (KSHV), is a phosphoprotein, and localizes in the host cell nuclei. Through the generation of an ORF45-null mutant BoHV-4 and its pararevertant, it was possible to demonstrate that ORF45 is essential for BoHV-4 lytic replication and is associated with the viral particles, as for the other characterized Rhadinovirus ORF45s. Finally, the impact of BoHV-4 ORF45 on cellular transcriptome was investigated, an aspect poorly explored or not at all for other Gammaherpesvirus. Many cellular transcriptional pathways were found to be altered, mainly those involving p90 ribosomal S6 kinase (RSK) and signal-regulated kinase (ERK) complex (RSK/ERK). It was concluded that BoHV-4 ORF45 has similar characteristics to those of KSHV ORF45, and its unique and incisive impact on the cell transcriptome paves the way for further investigations.

Characterization and phylogenetic analysis of bovine gammaherpesvirus 4 isolated in China, 2022

Bovine gammaherpesvirus 4 (BoHV-4) is a common virus detected in bovine with respiratory disease worldwide. In this study, we identified and characterized a novel BoHV-4 strain, referred as HB-ZJK, in vaginal swabs collected from cattle in China, 2022. The long unique region (LUR) of HB-ZJK is 10,9811 bp in length. It shares 99.17% to 99.38% nucleotide identity to five BoHV-4 strains available in GenBank and the highest similarity was seen with BoHV-4V. test (JN133502.1) strain (99.38%). Mutations, insertions or deletions were observed mainly in HB-ZJK gB (ORF8), TK (ORF21), gH (ORF22), MCP (ORF25), PK (ORF36), gM (ORF39), and gL (ORF47) genes compared to its genomic coordinates. Phylogenetic analyses of gB and TK genes showed that HB-ZJK clustered with China 512 (2019), B6010 (2009), and J4034 (2009) strains, demonstrating that the isolated HB-ZJK belongs to genotype 1. This is the first report that has revealed a comprehensive genome profile of BoHV-4 strain in China. This study will provide foundation for epidemiological investigations of BoHV-4 and contribute to the molecular and pathogenic studies of BoHV-4.

Genome sequence and experimental infection of calves with bovine gammaherpesvirus 4 (BoHV-4)

Bovine gammaherpesvirus 4 (BoHV-4) is ubiquitous in cattle worldwide, and it has been detected in animals exhibiting broad clinical presentations. The virus has been detected in the United States since the 1970s; however, its clinical relevance remains unknown. Here, we determined the complete genome sequences of two contemporary BoHV-4 isolates obtained from respiratory (SD16-38) or reproductive (SD16-49) tract specimens and assessed clinical, virological, and pathological outcomes upon intranasal (IN) inoculation of calves with the respiratory BoHV-4 isolate SD16-38. A slight and transient increase in body temperature was observed in BoHV-4-inoculated calves. Additionally, transient viremia and virus shedding in nasal secretions were observed in all inoculated calves. BoHV-4 DNA was detected by nested PCR in the tonsil and regional lymph nodes (LNs) of calves euthanized on day 5 post-inoculation (pi) and in the lungs of calves euthanized on day 10 pi. Calves euthanized on day 35 pi harbored BoHV-4 DNA in the respiratory tract (turbinates, trachea, lungs), regional lymphoid tissues, and trigeminal ganglia. Interestingly, in situ hybridization revealed the presence of BoHV-4 DNA in nerve bundles surrounding the trigeminal ganglia and retropharyngeal lymph nodes (day 35 pi). No histological changes were observed in the respiratory tract (turbinate, trachea, and lung), lymphoid tissues (tonsil, LNs, thymus, and spleen), or central nervous tissues (olfactory bulb and trigeminal ganglia) sampled throughout the animal studies (days 5, 10, and 35 pi). This study contributes to the understanding of the infection dynamics and tissue distribution of BoHV-4 following IN infection in calves. These results suggest that BoHV-4 SD16-38 used in our study has low pathogenicity in calves upon intranasal inoculation.

[Detection of bovine herpesvirus 4 DNA in cattle by realtime PCR.]

INTRODUCTION

BoHV-4 is poorly understood. Data on the circulation of the virus among animals and its role in infectious diseases insufficient. Aimes and goals. Development of real-time PCR for detecting the BoHV-4 and studying the frequency of its presence in samples from sick animals.

MATERIAL AND METHODS

The nucleotide sequences of the glycoprotein L gene served as a target for amplification. The sequences of reference strains published in GenBank were used to analyze and design the primers. Studies were conducted in 3 regions of Western Siberia on 5 large dairy farms.

RESULTS

27.7% of samples contained the virus. The virus was present as a monoagent in nasal cavity of calves (80.0%), lungs (46.2%) and bronchial lymph nodes (38.5%) in pneumonia. In the cases of diarrhea the virus was detected in 20%, and in cows with gynecological pathology in 10.0%. In respiratory diseases of calves the virus was detected in association with BoHV-1 (21.6%) and BoCV (20.3%), and in gynecological pathology of cows with BVDV1 (6%).

DISCUSSION

According to the phylogenetic analysis of 5 identified virus isolates, four belonged to the American branch and one to the European branch. The circulation of American strains occurred in the territory of the Republic of Kazakhstan (1), Tyumen (1) and Novosibirsk (2) regions, and the European - in the Novosibirsk region.

CONCLUSION

The search for viruses involved to the infectious pathology, as well as studying the genetic diversity of viruses circulating on a particular farm including imported from other countries, is relevant.

Genetic Variation in the Glycoprotein B Sequence of Equid Herpesvirus 5 among Horses of Various Breeds at Polish National Studs

Equid herpesvirus 5 (EHV-5) is one of two γ-herpesviruses that commonly infect horses worldwide. The objective of the study was to estimate the genetic variability within EHV-5 viruses circulating among horses in Poland. Partial glycoprotein B (gB) sequences from 92 Polish horses from 13 studs throughout Poland were compared to each other and to three EHV-5 sequences from other countries. Despite the overall high level of conservation, considerable variability was observed around the putative furin cleavage site. Based on phylogenetic analysis, the viruses clustered within two major lineages (A and B), with further sub-clustering within group A. The clustering of EHV-5 sequences was independent of age or geographical origin of the sampled horses. Recombination was identified as one of the factors contributing to the genomic heterogeneity. Viruses from unweaned foals were more similar to viruses from other foals at the same stud than to viruses form their dams, suggesting the horizontal transfer and/or evolution of EHV-5 within individual hosts. Our data indicate that the gB sequence is not suitable for tracking the source of EHV-5 infection. Further research is needed to elucidate the importance of the sequence variability around the EHV-5 gB furin cleavage site on the biology of the virus.

Isolation and molecular characterization of bovine herpesvirus 4 from cattle in mainland China

Bovine herpesvirus 4 (BoHV-4) is one of the most important of the known viral respiratory and reproductive pathogens of both young and adult cattle. However, BoHV-4 has not been isolated or detected in mainland China prior to this study. In 2019, BoHV-4 strain 512 was isolated from cattle in Heilongjiang Province, China, using MDBK cells, and characterized by PCR, nucleotide sequence analysis, and transmission electron microscopy. Two other unknown herpesvirus strains, BL6010 and J4034, which were isolated from cattle in 2009 in China and stored at -70℃, were also propagated in MDBK cells and identified as BoHV-4 by PCR. Phylogenetic analysis based on partial nucleotide sequences of the thymidine kinase (TK) gene and glycoprotein B (gB) gene for the three isolates indicated that these three Chinese strains belong to BoHV-4 genotype 1. A preliminary virus neutralization test revealed that 64% of the 70 bovine sera (45/70) collected from Inner Mongolia Autonomous Region, China, had anti-BoHV-4 antibodies and that natural BoHV-4 infection occurred in cattle in China. Here, we report for the first time the isolation and molecular characterization of BoHV-4 from cattle in mainland China.

Virus-Host Coevolution with a Focus on Animal and Human DNA Viruses

Viruses have been infecting their host cells since the dawn of life, and this extremely long-term coevolution gave rise to some surprising consequences for the entire tree of life. It is hypothesised that viruses might have contributed to the formation of the first cellular life form, or that even the eukaryotic cell nucleus originates from an infection by a coated virus. The continuous struggle between viruses and their hosts to maintain at least a constant fitness level led to the development of an unceasing arms race, where weapons are often shuttled between the participants. In this literature review we try to give a short insight into some general consequences or traits of virus–host coevolution, and after this we zoom in to the viral clades of adenoviruses, herpesviruses, nucleo-cytoplasmic large DNA viruses, polyomaviruses and, finally, circoviruses.

Bovine Herpesvirus Type 4 (BoHV-4) Vector Delivering Nucleocapsid Protein of Crimean-Congo Hemorrhagic Fever Virus Induces Comparable Protective Immunity against Lethal Challenge in IFNα/β/γR-/- Mice Models

Crimean-Congo hemorrhagic fever virus (CCHFV) is the causative agent of a tick-borne infection with a significant mortality rate of up to 40% in endemic areas, with evidence of geographical expansion. Due to a lack of effective therapeutics and control measures, the development of a protective CCHFV vaccine remains a crucial public health task. This paper describes, for the first time, a Bovine herpesvirus type 4 (BoHV-4)-based viral vector (BoHV4-∆TK-CCHFV-N) and its immunogenicity in BALB/c and protection potential in IFNα/β/γR−/− mice models in comparison with two routinely used vaccine platforms, namely, Adenovirus type 5 and a DNA vector (pCDNA3.1 myc/His A), expressing the same antigen. All vaccine constructs successfully elicited significantly elevated cytokine levels and specific antibody responses in immunized BALB/c and IFNα/β/γR−/− mice. However, despite highly specific antibody responses in both animal models, the antibodies produced were unable to neutralize the virus in vitro. In the challenge experiment, only the BoHV4-∆TK-CCHFV-N and Ad5-N constructs produced 100% protection against lethal doses of the CCHFV Ank-2 strain in IFNα/β/γR−/− mice. The delivery platforms could not be compared due to similar protection rates in IFNα/β/γR−/− mice. However, during the challenge experiment in the T cell and passive antibody transfer assay, BoHV4-∆TK-CCHFV-N was dominant, with a protection rate of 75% compared to others. In conclusion, vector-based CCHFV N protein expression constitutes an effective approach for vaccine development and BoHV-4 emerged as a strong alternative to previously used viral vectors.

Comparative analysis of replicative properties of phylogenetically divergent, Argentinean BoHV-4 strains in cell lines from different origins

Bovine gammaherpesvirus 4 (BoHV4) is a member of the family Herpesviridae. In Argentina, BoHV4 was isolated and characterized in 2007 from samples of aborted cows. Argentinean isolates are highly divergent and are classified as: Genotype 1(Movar-like), Genotype 2 (DN599-like) and Genotype 3 (a novel group). The aim of this study was to comparatively evaluate the biological characteristics of six Argentinean BoHV4 field isolates in cell lines from different origins. All strains induced productive infection in the cell lines used, with different degrees of permissiveness. A direct relationship among the times of appearance of cytopathic effect, the growth kinetics, the size of the lysis plaques and the virulent-like behaviour in vitro could not be established. However, although slight, there are differences in the biological behaviour of the BoHV4 fields isolates analyzed. This variability is independent of their genetic classification but would be conditioned by the nature of the infected cells.

Cell-Derived Viral Genes Evolve under Stronger Purifying Selection in Rhadinoviruses

Like many other large double-stranded DNA (dsDNA) viruses, herpesviruses are known to capture host genes to evade host defenses. Little is known about the detailed natural history of such genes, nor do we fully understand their evolutionary dynamics. A major obstacle is that they are often highly divergent, maintaining very low sequence similarity to host homologs. Here we use the herpesvirus genus Rhadinovirus as a model system to develop an analytical approach that combines complementary evolutionary and bioinformatic techniques, offering results that are both detailed and robust for a range of genes. Using a systematic phylogenetic strategy, we identify the original host lineage of viral genes with high confidence. We show that although host immunomodulatory genes evolve rapidly compared to other host genes, they undergo a clear increase in purifying selection once captured by a virus. To characterize this shift in detail, we developed a novel technique to identify changes in selection pressure that can be attributable to particular domains. These findings will inform us on how viruses develop strategies to evade the immune system, and our synthesis of techniques can be reapplied to other viruses or biological systems with similar analytical challenges.IMPORTANCE Viruses and hosts have been shown to capture genes from one another as part of the evolutionary arms race. Such genes offer a natural experiment on the effects of evolutionary pressure, since the same gene exists in vastly different selective environments. However, sequences of viral homologs often bear little similarity to the original sequence, complicating the reconstruction of their shared evolutionary history with host counterparts. In this study, we use a genus of herpesviruses as a model system to comprehensively investigate the evolution of host-derived viral genes, using a synthesis of genomics, phylogenetics, selection analysis, and nucleotide and amino acid modeling.

Bovine Herpesvirus-4-Based Vector Delivering Peste des Petits Ruminants Virus Hemagglutinin ORF Induces both Neutralizing Antibodies and Cytotoxic T Cell Responses

Peste des Petits Ruminants Virus (PPRV) is an extremely infective morbillivirus that primarily affects goats and sheep. In underdeveloped countries where livestock are the main economical resource, PPRV causes considerable economic losses. Protective live attenuated vaccines are currently available but they induce antibody responses similar to those produced in PPRV naturally infected animals. Effective vaccines able to distinguish between vaccinated and naturally infected animals are required to PPRV control and eradication programs. Hemagglutinin (H) is a highly immunogenic PPRV envelope glycoprotein displaying both hemagglutinin and neuraminidase activities, playing a crucial role in virus attachment and penetration. In this study, a recombinant Bovine Herpesvirus-4 (BoHV-4)-based vector delivering an optimized PPRV-Hemagglutinin expression cassette, BoHV-4-A-PPRV-H-ΔTK, was assessed in immunocompetent C57BL/6 mice. BoHV-4-A-PPRV-H-ΔTK-immunization elicited both cellular and humoral immune responses with specific T cell, cytotoxic T lymphocyte, and sero-neutralizing antibody against PPRV. These data suggest recombinant BoHV-4-A-PPRV-H-ΔTK as an effective vaccine candidate to protect against PPRV herd infection and potentially applicable for eradication programs.

Whole Genome Sequencing of a Canadian Bovine Gammaherpesvirus 4 Strain and the Possible Link between the Viral Infection and Respiratory and Reproductive Clinical Manifestations in Dairy Cattle

Bovine gammaherpesvirus 4 (BoHV-4) is a herpesvirus widespread in cattle populations, and with no clear disease association. Its genome contains a long unique coding region (LUR) flanked by polyrepetitive DNA and 79 open reading frames (ORFs), with unique 17 ORFs, named Bo1 to Bo17. In 2009, a BoHV-4 strain was isolated (FMV09-1180503: BoHV-4-FMV) from cattle with respiratory disease from Quebec, Canada, and its LUR was sequenced. Despite the overall high similarity, BoHV-4-FMV had the most divergent LUR sequence compared to the two known BoHV-4 reference strain genomes; most of the divergences were in the Bo genes and in the repeat regions. Our phylogenetic analysis based on DNA polymerase and thymidine kinase genes revealed that virus isolate was BoHV-4 gammaherpesvirus and clustered it together with European BoHV-4 strains. Because BoHV-4-FMV was isolated from animals presenting respiratory signs, we have updated the BoHV-4 Canadian cattle seroprevalence data and tried to find out whether there is a link between clinical manifestation and BoHV-4 seropositivity. An indirect immunofluorescence assay (IFA) was performed with nearly 200 randomized sera of dairy cattle from two Canadian provinces, Quebec (n = 100) and Ontario (n = 91). An additional set of sera obtained from Quebec, from the healthy (n = 48) cows or from the animals experiencing respiratory or reproductive problems (n = 75), was also analyzed by IFA. BoHV-4 seroprevalence in Canadian dairy cattle was 7.9% (Quebec: 6% and Ontario: 9.9%). Among animals from the Quebec-based farms, diseased animals showed higher BoHV-4 seropositivity than healthy animals (P < 0.05), with a significant 2.494 odds ratio of being seropositive in sick compared to healthy animals. Although there is no established direct link between BoHV-4 and specific diseases, these seroprevalence data suggest the possible involvement of BoHV-4 in dairy cattle diseases.

Spread of the newly emerging infectious laryngotracheitis viruses in Australia

Infectious laryngotracheitis (ILT) is a significant viral disease of chickens in many countries around the globe. In this report the status of ILT in Australia has been used as a model to evaluate the evolution of the ILT viruses (ILTVs). Due to its geographical isolation, Australia harbored a distinct lineage of ILT viruses (ILTV) up to 2007. However examination of the ILT viruses (ILTV) involved in outbreaks between 2007 and 2009 has revealed that many of the outbreaks were caused by two new viral genotypes, class 8 and class 9. These two recombinant viruses were found to emerge as a result of recombination between previously existing live vaccine strains (SA2 and A20), and another live vaccine strain (Serva) introduced into the country in 2007. The new recombinant ILTVs were also shown to possess significantly higher virulence and replication capacity compared with a previously predominant ILTV, class 2. In the current study, examination of a large number of ILTVs isolated from outbreaks between 2009 and 2015 revealed the emergence of yet another recombinant virus (class 10) that appears to have become a predominant genotype in New South Wales. In Victoria however, the recombinant class 9 gradually became the predominant virus, replacing class 2. Therefore, there was an unusual pattern in geographical spread of the newly emerged viruses in different states of the country. These results suggest that ILTV is fast evolving towards a greater transmissibility and therefore greater capacity to spread into ILTV-free areas.

[Bovine herpesvirus 4 (BoHV-4): general aspects of the biology and status in Argentina]

Bovine herpesvirus 4 (BoHV-4) has been isolated from cattle with respiratory infections, vulvovaginitis, mastitis, abortions, endometritis and from apparently healthy animals throughout the world. Although it has not yet been established as causal agent of a specific disease entity, it is primarily associated with reproductive disorders of cattle. This virus can infect a wide range of species, either in vivo or in vitro. Two groups of prototype strains were originated from the first isolates: the DN599-type strains (American group) and the Movar-type strains (European group). In Argentina, BoHV-4 was isolated and characterized in 2007 from vaginal discharge samples taken from cows that had aborted. So far, more than 40 isolates, mainly associated with aborting bovine females have been registered in our country.

The genome of Chelonid herpesvirus 5 harbors atypical genes

The Chelonid fibropapilloma-associated herpesvirus (CFPHV; ChHV5) is believed to be the causative agent of fibropapillomatosis (FP), a neoplastic disease of marine turtles. While clinical signs and pathology of FP are well known, research on ChHV5 has been impeded because no cell culture system for its propagation exists. We have cloned a BAC containing ChHV5 in pTARBAC2.1 and determined its nucleotide sequence. Accordingly, ChHV5 has a type D genome and its predominant gene order is typical for the varicellovirus genus within the alphaherpesvirinae. However, at least four genes that are atypical for an alphaherpesvirus genome were also detected, i.e. two members of the C-type lectin-like domain superfamily (F-lec1, F-lec2), an orthologue to the mouse cytomegalovirus M04 (F-M04) and a viral sialyltransferase (F-sial). Four lines of evidence suggest that these atypical genes are truly part of the ChHV5 genome: (1) the pTARBAC insertion interrupted the UL52 ORF, leaving parts of the gene to either side of the insertion and suggesting that an intact molecule had been cloned. (2) Using FP-associated UL52 (F-UL52) as an anchor and the BAC-derived sequences as a means to generate primers, overlapping PCR was performed with tumor-derived DNA as template, which confirmed the presence of the same stretch of “atypical” DNA in independent FP cases. (3) Pyrosequencing of DNA from independent tumors did not reveal previously undetected viral sequences, suggesting that no apparent loss of viral sequence had happened due to the cloning strategy. (4) The simultaneous presence of previously known ChHV5 sequences and F-sial as well as F-M04 sequences was also confirmed in geographically distinct Australian cases of FP. Finally, transcripts of F-sial and F-M04 but not transcripts of lytic viral genes were detected in tumors from Hawaiian FP-cases. Therefore, we suggest that F-sial and F-M04 may play a role in FP pathogenesis.

Molecular cloning and characterization of Th1 and Th2 cytokines of African buffalo (Syncerus caffer)

The African buffalo (Syncerus caffer) has been implicated as the reservoir of several bovine infectious agents. However, there is insufficient information on the protective immune responses in the African buffalo, particularly in infected animals. In this study, we analysed Th1 cytokines IL-2 and IFN-γ, and Th2 cytokines IL-4 and IL-10. The cloned cDNA of IL-2, IL-4, IL-10 and IFN-γ contained an open reading frame of 468, 501, 408 and 540 nucleotides, encoding polypeptides of 155, 166, 135 and 179 amino acids, respectively. Nucleotide sequence homology of IL-2, IFN-γ and IL-4 was more than 98% between the African buffalo and cattle, which resulted in identical polypeptides. Meanwhile, IL-10 gene of African buffalo and cattle had 95% homology in nucleotide sequence, corresponding to thirteen amino acid residues substitution. Cysteine residues and potential glycosylation sites were conserved within the family Bovinae. Phylogenetic analyses including cytokines of the African buffalo placed them within a cluster comprised mainly of species belonging to the order Artiodactyla, including cattle, water buffalo, sheep, goat, pig and artiodactyl wildlife. A deeper understanding of the structure of these cytokines will shed light on their protective role in the disease-resistant African buffalo in comparison with other closely related species.

Antibody evasion by a gammaherpesvirus O-glycan shield

All gammaherpesviruses encode a major glycoprotein homologous to the Epstein-Barr virus gp350. These glycoproteins are often involved in cell binding, and some provide neutralization targets. However, the capacity of gammaherpesviruses for long-term transmission from immune hosts implies that in vivo neutralization is incomplete. In this study, we used Bovine Herpesvirus 4 (BoHV-4) to determine how its gp350 homolog--gp180--contributes to virus replication and neutralization. A lack of gp180 had no impact on the establishment and maintenance of BoHV-4 latency, but markedly sensitized virions to neutralization by immune sera. Antibody had greater access to gB, gH and gL on gp180-deficient virions, including neutralization epitopes. Gp180 appears to be highly O-glycosylated, and removing O-linked glycans from virions also sensitized them to neutralization. It therefore appeared that gp180 provides part of a glycan shield for otherwise vulnerable viral epitopes. Interestingly, this O-glycan shield could be exploited for neutralization by lectins and carbohydrate-specific antibody. The conservation of O-glycosylation sites in all gp350 homologs suggests that this is a general evasion mechanism that may also provide a therapeutic target.

Sequencing of bovine herpesvirus 4 v.test strain reveals important genome features

Background

Bovine herpesvirus 4 (BoHV-4) is a useful model for the human pathogenic gammaherpesviruses Epstein-Barr virus and Kaposi's Sarcoma-associated Herpesvirus. Although genome manipulations of this virus have been greatly facilitated by the cloning of the BoHV-4 V.test strain as a Bacterial Artificial Chromosome (BAC), the lack of a complete genome sequence for this strain limits its experimental use.

Methods

In this study, we have determined the complete sequence of BoHV-4 V.test strain by a pyrosequencing approach.

Results

The long unique coding region (LUR) consists of 108,241 bp encoding at least 79 open reading frames and is flanked by several polyrepetitive DNA units (prDNA). As previously suggested, we showed that the prDNA unit located at the left prDNA-LUR junction (prDNA-G) differs from the other prDNA units (prDNA-inner). Namely, the prDNA-G unit lacks the conserved pac-2 cleavage and packaging signal in its right terminal region. Based on the mechanisms of cleavage and packaging of herpesvirus genomes, this feature implies that only genomes bearing left and right end prDNA units are encapsulated into virions.

Conclusions

In this study, we have determined the complete genome sequence of the BAC-cloned BoHV-4 V.test strain and identified genome organization features that could be important in other herpesviruses.

Neurological disorder in cattle associated with bovine herpesvirus 4

A nested PCR assay was used to diagnose bovine encephalitis through herpesviruses including bovine herpesvirus 5 (BHV-5), bovine herpesvirus 1 (BHV-1), Aujeszky's disease virus (SHV-1), and ovine herpesvirus 2 (OHV-2) in 14 fragments of central nervous system (CNS) from cattle that died with neurological signs. In addition, as some samples of bovine herpesvirus type 4 (BHV-4) have been isolated from neural tissue, it was also tested by nested PCR. The cases of encephalitis occurred in isolation at different times of the year and did not present any seasonality. The duration of the clinical course ranged between 1 to 15 days, and in 64.3% of the cases it manifested between 1 to 2 days. The most frequently observed neurological signs were ataxia, recumbency, unsteadiness and inability to stand, opisthotonus, paddling movements, nystagmus and ptyalism. In the nested assay, there was no evidence of: BHV-1, SHV-1 or OHV-2 in the DNA obtained from the CNS in any of the samples. But the presence of BHV-4 was found in all fragments of the CNS in cattle which died presenting neurological signs. Moreover, BHV-5 was found in association with BHV-4 in two of these samples.

The possible role of bovine herpesvirus type-4 infection in cow infertility

Experimental and field studies have proven that the bovine herpesvirus type-4 (BHV-4) infection leads to various reproductive system problems. In this study, the role of BHV-4 infection in repeat breeding was investigated serologically. Eighty-four samples were obtained from repeat-breeding diagnosed cows in two organized dairy herds; an equal number of healthy cows were sampled from the same farms. The rest of the samples (105) were obtained from reproductively normal cows that were breeding in 18 small enterprises as a control group. The seropositivity proportion in repeat-breeding diagnosed cows was found to be significantly higher (69% (58/84)) than other cows (44% (37/84)) on the same farms. The lowest antibody positivity value for BHV-4 was detected as 24.7% (26/105) in the samples from family-type small farms. The odds ratio (OR) value was calculated as 2.834 in repeat-breeding diagnosed and healthy cows on the same farms, while 6.778 was determined in cows with and without reproductive problems on organized farms compared to small farms. As a result, the BHV-4 infection can be considered one of the reasons for repeat breeding besides other reproductive disorders.

Coinfection with two closely related alphaherpesviruses results in a highly diversified recombination mosaic displaying negative genetic interference

Phylogenetic studies of the emergence and spread of natural recombinants in herpesviruses infecting humans and animals have been reported recently. However, despite an ever-increasing amount of evidence of recombination in herpesvirus history, the recombination process and the consequences on the genetic diversity of the progeny remain poorly characterized. We addressed this issue by using multiple single-nucleotide polymorphisms (SNPs) differentiating the two subtypes of an alphaherpesvirus, bovine herpesvirus 1 (BoHV-1). Analysis of a large sample of progeny virions obtained in a single growth cycle of coinfected BoHV-1 strains provided a prospective investigation of the recombination dynamics by using SNPs as recombination markers. We found that the simultaneous infection with two closely related herpesviruses results in a highly diversified recombination mosaic. From the analysis of multiple recombinants arising in the progeny, we provide the first evidence of genetic interference influencing the recombination process in herpesviruses. In addition, we report striking differences in the levels of recombination frequency observed along the BoHV-1 genome. With particular emphasis on the genetic structure of a progeny virus population rising in vitro, our data show to which extent recombination participates to the genetic diversification of herpesviruses.