Studies of in vivo distribution of bovine herpesvirus type 4 in the natural host

Epidemiological survey of bovine gammaherpesvirus 4 (BoHV-4) infection in cattle and buffalo from Pakistan

This study was conducted to evaluate the prevalence of bovine gammaherpesvirus 4 (BoHV-4) among healthy cattle and buffaloes as well as those associated with different diseases (respiratory tract infection, mastitis and reproductive tract infection) in District Chakwal, Pakistan. Blood, swab and milk samples of cattle and buffaloes were randomly collected from different areas of Chakwal. DNA was isolated from the samples and subjected to nested PCR using thymidine kinase gene primers. Out of 300 samples (200 blood, 50 swab and 50 milk samples) from both species (cattle and buffalo), an overall prevalence of BoHV-4 of 3.33% was obtained. Samples from cattle showed a higher species-specific prevalence (4.16%) than samples from buffalo (2.78%). One sample out of 50 swab samples and 1 out of 50 milk samples were also positive for BoHV-4. DNA sequencing of a positive PCR product from cattle confirmed that the sequence was from the thymidine kinase gene of BoHV-4. Phylogenetic analysis also revealed close similarities with other BOHV-4 thymidine kinase sequences. To detect BoHV-4 antibodies, an indirect ELISA was also performed. Two hundred blood samples were also collected from the same animals in nonanticoagulant-containing tubes for the isolation of serum and were subjected to indirect ELISA. Sixteen samples (8%) were positive for BoHV-4 antibodies. This study will be useful in further diagnoses of BoHV-4 in Pakistan and in devising measures to control the spread 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.

OvHV-2 Glycoprotein B Delivered by a Recombinant BoHV-4 Is Immunogenic and Induces Partial Protection against Sheep-Associated Malignant Catarrhal Fever in a Rabbit Model

An efficacious vaccine for sheep-associated malignant catarrhal fever (SA-MCF) is important for the livestock industry. Research towards SA-MCF vaccine development is hindered by the absence of culture systems to propagate the causative agent, ovine herpesvirus-2 (OvHV-2), which means its genome cannot be experimentally modified to generate an attenuated vaccine strain. Alternative approaches for vaccine development are needed to deliver OvHV-2 antigens. Bovine herpesvirus 4 (BoHV-4) has been evaluated as a vaccine vector for several viral antigens with promising results. In this study, we genetically engineered BoHV-4 to express OvHV-2 glycoprotein B (gB) and evaluated its efficacy as an SA-MCF vaccine using a rabbit model. The construction of a viable recombinant virus (BoHV-4-AΔTK-OvHV-2-gB) and confirmation of OvHV-2 gB expression were performed in vitro. The immunization of rabbits with BoHV-4-AΔTK-OvHV-2-gB elicited strong humoral responses to OvHV-2 gB, including neutralizing antibodies. Following intra-nasal challenge with a lethal dose of OvHV-2, 42.9% of the OvHV-2 gB vaccinated rabbits were protected against SA-MCF, while all rabbits in the mock-vaccinated group succumbed to SA-MCF. Overall, OvHV-2 gB delivered by the recombinant BoHV-4 was immunogenic and partly protective against SA-MCF in rabbits. These are promising results towards an SA-MCF vaccine; however, improvements are needed to increase protection rates.

Epidemiological study of the association between bovine gammaherpesvirus type 4 and reproductive disease in dairy cattle from northwestern Spain

Bovine gammaherpesvirus 4 (BoHV-4) has controversially been related with cattle reproductive disease. In the present study we analyze the relationship between exposure to BoHV-4 and reproductive performance in dairy cattle from northwestern Spain. A total of 2022 sera from 50 farms were examined to detect anti-BoHV-4 antibodies. Herd and individual reproductive records were collected to analyze association with exposure to BoHV-4. In addition, 52 abortion cases were examined to detect BoHV-4 DNA. An individual seroprevalence of 66.6 % and a herd prevalence of 98 % were found. Exposure to BoHV-4 increased with age, particularly in individuals between 26-36 months old (OR = 2.7; CI 95 %: 1.2-5.0, compared to animals < 26 months). Seroprevalence was not associated with herd fertility and herd abortion rate, but seropositive animals between 26-36 months presented prolonged calving to fertilizing insemination intervals (HR: 1.4; CI 95 %: 1.2-2.0) as well as higher odds of an unsuccessful 1^st insemination (OR: 2.5; CI 95 %: 1.2-5.0). In abortion cases, BoHV-4 DNA was found in 12 vaginal swabs from 5 farms but not in any fetal tissue. Our results reveal an endemic, high and widespread exposure to BoHV-4 among dairy cattle from NW Spain with a limited impact in the reproductive performance of herds. The significantly worse reproductive performance of seropositive animals of 26-36 months of age may be the consequence of the establishment of primo-infections when moving heifers to lactation lots. Our findings may be useful to understand the potential population impact of BoHV-4.

Bovine Herpesvirus-4-Vectored Delivery of Nipah Virus Glycoproteins Enhances T Cell Immunogenicity in Pigs

Nipah virus (NiV) is an emergent pathogen capable of causing acute respiratory illness and fatal encephalitis in pigs and humans. A high fatality rate and broad host tropism makes NiV a serious public and animal health concern. There is therefore an urgent need for a NiV vaccines to protect animals and humans. In this study we investigated the immunogenicity of bovine herpesvirus (BoHV-4) vectors expressing either NiV attachment (G) or fusion (F) glycoproteins, BoHV-4-A-CMV-NiV-GΔTK or BoHV-4-A-CMV-NiV-FΔTK, respectively in pigs. The vaccines were benchmarked against a canarypox (ALVAC) vector expressing NiV G, previously demonstrated to induce protective immunity in pigs. Both BoHV-4 vectors induced robust antigen-specific antibody responses. BoHV-4-A-CMV-NiV-GΔTK stimulated NiV-neutralizing antibody titers comparable to ALVAC NiV G and greater than those induced by BoHV-4-A-CMV-NiV-FΔTK. In contrast, only BoHV-4-A-CMV-NiV-FΔTK immunized pigs had antibodies capable of significantly neutralizing NiV G and F-mediated cell fusion. All three vectored vaccines evoked antigen-specific CD4 and CD8 T cell responses, which were particularly strong in BoHV-4-A-CMV-NiV-GΔTK immunized pigs and to a lesser extent BoHV-4-A-CMV-NiV-FΔTK. These findings emphasize the potential of BoHV-4 vectors for inducing antibody and cell-mediated immunity in pigs and provide a solid basis for the further evaluation of these vectored NiV vaccine candidates.

An assessment of bovine herpes virus 4 as a causative agent in abortions and neonatal death

Numerous viruses, including bovine viral diarrhoea virus (BVDV), bovine herpes virus 1 (BoHV-1) and bovine herpes virus 4 (BoHV-4), and other pathogens are the most common causes of reproductive disorders and are responsible for huge economic losses in livestock production. This study investigates the aetiological role of BoHV-4 in fertility problems such as abortions, stillbirth and birth with unviable calves. Retrospective samples from 38 animals, including 17 aborting cows, 17 aborted foetuses, three stillborn calves and one unviable newborn calf were analysed. The BoHV-4 genome was detected in 25 (65.7%) animals by polymerase chain reaction. In 14 of these infected animals, we detected co-infection with BVDV, while the co-presence of BoHV-1 was also detected in one animal. In addition to the high prevalence of BoHV-4 genome in materials related to fertility problems, isolation of BoHV-4 from the brain of one stillborn calf indicated a causal link between BoHV-4 and fertility problems, such as abortion, stillbirths or birth with unviable calves.

Studies on the molecular biological peculiarities of bovine herpesvirus 4

Studies on the molecular biological features of bovine herpesvirus 4 (BHV 4) strains isolated in Bulgaria have been conducted. Two types of polymerase chain reaction have been developed and applied to confirm the gB and TK genes. A restrictase fragment analysis was performed using various types of restrictase enzymes. The tested Bulgarian strains differed in their restrictase genomic profile from the reference European strain Movar 33/63 and from the American strain DN 599, and were clearly different each from the other. No clear relationship has been established between the restrictase enzyme profiles and the tropism of the isolated viruses. Sequencing of isolated ВHV 4 strains showed homo­logy with the reference European strain Movar 33/63. After construction of the phylogenetic tree, three ВHV 4 strains were at one branch of the phylogenetic tree, while two other strains were at the branch of reference Movar 33/63 strain. Applied molecular biology methods can be successfully used for differentiation and detailed genetic characterisation of the isolated BHV 4 strains.

Monitoring of the shedding and serological dynamics of Bovine gammaherpesvirus type 4 in a dairy cattle herd

Bovine gammaherpesvirus type 4 (BoHV-4) is increasingly related with reproductive disease in cattle, but its epidemiology is not fully understood. We monitored the serological response and shedding of BoHV-4 in a positive dairy cattle farm with metritis. First, we performed an ELISA to detect BoHV-4 antibodies in all the animals (n = 104). Afterwards, ten seronegative heifers introduced in the production lot and sera samples were monthly taken for four months and then 6-10 months after introduction to detect BoHV-4 antibodies by ELISA. Moreover, a vaginal swab was taken after calving to detect BoHV-4 by PCR. Concurrently, a weekly collection of vaginal and nasal swabs and milk was performed during the first month post-partum in multiparous cows with metritis (n = 14), heifers with metritis (n = 4), heifers without metritis but positive to BoHV-4 (ELISA or PCR) (n = 2) and multiparous cows without metritis (n = 3). Seropositivity was higher in older animals and in the production lot. Three heifers which shed BoHV-4 after parturition resulted seronegative at first but eventually seroconverted. In the same vein, most heifers seroconverted after 6-10 months in the production lot (8/10). Multiparous cows shed virus by various routes: 13/14 (93 %) in vaginal secretions, 7/14 (50 %) in nasal exudates and 7/14 (50 %) in milk. However, in the other groups, shedding was only detected in vaginal swabs from the first week post-partum. Our study describes BoHV-4 shedding in field conditions. Seronegative animals may become horizontally infected when moved to a contaminated environment.

A recombinant bovine herpesvirus-4 vectored vaccine delivered via intranasal nebulization elicits viral neutralizing antibody titers in cattle

Recombinant herpesvirus vaccine vectors offer distinct advantages in next-generation vaccine development, primarily due to the ability to establish persistent infections to provide sustainable antigen responses in the host. Recombinant bovine herpesvirus-4 (BoHV-4) has been previously shown to elicit protective immunity in model laboratory animal species against a variety of pathogens. For the first time, we describe the induction of antigen-specific immune responses to two delivered antigens in the host species after intranasal nebulization of recombinant BoHV-4 expressing the chimeric peptide containing the bovine viral diarrhea virus (BVDV) glycoprotein E2 and the bovine herpesvirus 1 (BoHV-1) glycoprotein D (BoHV-4-A-CMV-IgK-gE2gD-TM). In this study, four cattle were immunized via intranasal nebulization with the recombinant BoHV-4 construct. Two of the cattle were previously infected with wild-type BoHV-4, and both developed detectable serologic responses to BVDV and BoHV-1. All four immunized cattle developed detectable viral neutralizing antibody responses to BVDV, and one steer developed a transient viral neutralizing response to BoHV-1. Approximately one year after immunization, immunosuppressive doses of the glucocorticoid dexamethasone were administered intravenously to all four cattle. Within two weeks of immunosuppression, all animals developed viral neutralizing antibody responses to BoHV-1, and all animals maintained BVDV viral neutralizing capacity. Overall, nebulization of BoHV-4-A-CMV-IgK-gE2gD-TM persistently infects cattle, is capable of eliciting antigen-specific immunity following immunization, including in the presence of pre-existing BoHV-4 immunity, and recrudescence of the virus boosts the immune response to BoHV-4-vectored antigens. These results indicate that BoHV-4 is a viable and attractive vaccine delivery platform for use in cattle.

Presence of gammaherpesvirus BoHV-4 in endometrial cytology samples is not associated with subclinical endometritis diagnosed at artificial insemination in dairy cows

In the past, bovine herpesvirus 4 (BoHV-4) has been suggested to be associated with metritis and endometritis. However, not many field studies investigated the association between BoHV-4 and subclinical endometritis (SCE). In the present study, the association between the intrauterine presence of BoHV-4 and SCE diagnosed during artificial insemination (AI) was examined on two dairy farms in Belgium. An immunoperoxidase monolayer assay (IPMA) and an enzyme-linked immuno sorbent assay (ELISA) were used to screen the serum for anti-BoHV-4 antibodies. A SYBR green based one step real time qPCR was used to detect and quantify BoHV-4 (ORF20) in nasal, uterine and vaginal samples collected at AI. A reverse transcription qPCR (RT-qPCR) was used to detect mRNA (gB) as proof of a productive BoHV-4 infection. BoHV-4 was detected in 39.4% (farm A)/23.8% (farm B) of the nasal samples, 48.5% (farm A)/19.0% (farm B) of the uterine samples and 51.5% (farm A)/42.9% (farm B) of the vaginal samples. Active replication was only detected in farm A in 38.5% of the BoHV-4 positive nasal samples and in 5.9% positive cases of the vaginal samples. The prevalence of SCE diagnosed at AI was 45.5% and 42.9% in farm A and farm B, respectively. The presence of SCE was associated with a reduced pregnancy outcome at artificial insemination (AI) (P＜0.001). The occurrence of SCE at AI was not associated with the presence of latent or productive BoHV4 infections in the uterus nor in the vagina and nose (P＞0.05).

Bovine herpes virus type-4 infection among postpartum dairy cows in California: risk factors and phylogenetic analysis

The aims of this study were to determine the prevalence and associated risk factors of bovine herpes virus type-4 (BoHV-4) infection and describe the genetic characteristics and predominant genotypes of the virus in Yolo and Tulare counties, California. A cross-sectional study involving multi-stage sampling technique was used. One hundred and forty-eight post-partum cows were enrolled from 11 dairy farms. Uterine/vaginal samples were collected and tested for BoHV-4 and other co-infecting viruses using real-time PCR. Data were analysed using multilevel logistic mixed-effect model. Phylogenetic analysis of 10 BoHV-4 isolates was conducted by targeting three open reading frames (ORF3, ORF8 and ORF 22) of the viral genome. The prevalence of BoHV-4 infection was 22.3% (33/148), while post-partum metritis was 33.8% (48/142). Strong association was found between BoHV-4 infection and lactation number, lactation stage and post-partum metritis. The odds of being positive for BoHV-4 infection were 6.47 times (95% CI 1.17-35.92; P 240 days). Cows with post-partum metritis were 4.51 times (95% CI 1.27-16.02; P < 0.05) more likely to test positive for BoHV-4 infection compared with those without post-partum metritis. Phylogenetic analysis of BoHV-4 based on sequencing of glycoprotein and thymidine kinase (TK) genes revealed genetic variability of the virus with glycoprotein B genotype 1 and TK genotype 2 as being dominant genotypes. The reported high genetic variability of BoHV-4 indicates the possibility of co-infection with multiple genotypes.

The genetic diversity of bovine papillomaviruses (BPV) from different papillomatosis cases in dairy cows in Turkey

Papillomaviruses (PVs) are epitheliotropic viruses that cause benign proliferative lesions in the skin (warts or papillomas) and mucous membranes of their natural hosts. In bovines specifically, 13 types of Bovine papillomaviruses (BPVs) are currently described in the literature, although the actual number may be greater than 20. BPV types are classified into four genera based on homology within the genomic regions of the L1 ORF, the most conserved sequence. This study conducted molecular typing of BPV in dairy cows with different papillomatosis cases and investigated the presence of co-infections across distinct BPV types in the same sample. After carrying out PCR using degenerate primers and type specific primers, 35 BPV suspected samples were detected as positive for BPV and these samples were used for typing using sequence analysis/PCR with type-specific primers. This analysis identified BPV-1, -2, -3, -4, -6, -7, -9 and -10, new putative types (BPV/BR/UEL6-like viruses) and the previously described putative type viruses (BAPV-6) in the 35 BPV-positive samples. In addition, co-infections across different BPV types were widely detected in the BPV-positive samples.  This study shows that PCR assays using degenerate primers to amplify partial fragments of the L1 gene followed by sequencing is useful for genotyping BPV. However, results need confirmation using type-specific primers in order to consider co-infections. In addition, this study identified a new putative type (in the same cluster as BPV/BR/UEL6-like viruses) and the previously described putative type viruses (BAPV-6) in teat papillomatosis of Turkish dairy cows. The study shows that it is essential to identify BPV types and their prevalence/distribution, and also to determine the clinical consequences of infection for the development of prophylactic and/or therapeutic procedures.

Uterine infection with bovine herpesvirus type 4 in dairy cows

Diseases of the reproductive tract are a frequent problem in dairy herds. Herpesviruses are uterine pathogens also involved in other clinical diseases; for example, bovine herpesvirus type 4 BoHV-4 induces abortion, enteritis, metritis, pneumonia and vaginitis, but it can also be detected in healthy cows. The role of BoHV-4 in the development of clinical endometritis (CE) or subclinical endometritis (SE) has not clearly been described. Therefore, the objective of this study was to describe the prevalence of uterine BoHV-4 infection and its relationship with clinical, bacteriological and cytological findings in dairy cows 20-30 days after calving. The experiment was performed as a completely randomized block design, with farm (n = 10) as blocking criterion and with cow (n = 397) as the experimental unit. Logistic regression models were used to assess the effect of BoHV-4 infection on CE, SE and reproductive performance. Proportion of cows infected with BoHV-4 was 5.8% (n = 23/397). BoHV-4 was isolated in 11.0% (n = 12/109), 4.8% (n = 4/84) and 3.6% (n = 7/194) of cows diagnosed as CE, SE or healthy, respectively. A logistic model revealed that BoHV-4 infection showed a tendency to increase the risk for CE (AOR = 2.17; p = .10) but significantly reduced both, the odds for artificial insemination within 80 days post-partum (dpp) (AOR = 0.37; p = .035) and for pregnancy within 200 dpp (AOR = 0.13; p = .004). Furthermore, BoHV-4 infection increased the chance for intrauterine infection with Trueperella pyogenes (AOR = 5.55; p < .001) and vice versa (AOR = 5.79, p < .001). In conclusion, BoHV-4 infection is associated with reduced chances for insemination and pregnancy by 200 dpp and showed a trend to be associated with increased risk for CE. Furthermore, BoHV-4 and Trueperella pyogenes infections are strongly related.

Bovine herpesvirus 4 DNA is not detected in free-ranging domestic cats from California, Colorado or Florida

Objectives Several studies have reported that domestic cats can be naturally infected with bovine herpesvirus 4 (BHV4). Cats experimentally inoculated with BHV4 developed clinical signs involving the urinary tract, leading to the hypothesis that natural infection with BHV4 may be associated with feline lower urinary tract diseases. However, the question of whether BHV4 infection is common in cats remains equivocal. In this study, we sought to determine whether BHV4 is a common natural infection of domestic cats in the USA. Methods We used a sensitive nested PCR protocol specific to the BHV4 thymidine kinase gene to screen free-ranging domestic cat blood DNA samples (n = 101) collected from California, Colorado and Florida. Results Cats within this cohort were positive for seven other common pathogens of domestic cats, demonstrating the relatively high exposure of this population to endemic feline infections. In contrast, all domestic cat blood samples were negative for BHV4, while BHV4-containing tissue culture extracts were strongly positive. Conclusions and relevance BHV4 has been detected in tissues of latently infected cattle, though viral DNA is typically also detected in peripheral blood cells throughout infection. Our results suggest that persistent presence of BHV4 DNA in the blood of domestic cats is either rare or non-existent. We thus conclude that BHV4 is unlikely to be a major pathogen of cats.

The role of herpesviruses (BoHV-1 and BoHV-4) and pestiviruses (BVDV and BDV) in ruminant abortion cases in western Turkey

The economic impact of abortions in ruminant breeders is one of the biggest problems in livestock. Of the infectious agents, viruses, especially herpesviruses and pestiviruses, are the most important causative agents of abortion in ruminants. In the present study, the role of herpesviruses (bovine herpesvirus-1 (BoHV-1), bovine herpesvirus-4 (BoHV-4)) and pestiviruses (bovine viral diarrhea virus (BVDV), border disease virus (BDV)) was investigated in cases of ruminant abortion between 2007 and 2015 in western Turkey. Out of 81 aborted fetal samples (60 calves, 19 lambs, and 2 kids), 42 were positive, which included 31 calves, 9 lambs, and 2 goats; 39 aborted fetal samples were negative for the pestivirus antigen ELISA. BoHV-1 antigen ELISA was positive in 3 cases which included 2 calves and 1 lamb; the remainder 78 cases were negative. Pestivirus and BoHV-1 were positive in 51.85 and 3.70 %, respectively, of the samples. According to PCR analysis, BoHV-4 was not encountered in any of the tested samples. In one of the calf fetus samples, both BVDV and BoHV-1 were positive; in one of the lamb fetus samples, BoHV-1 was positive. There was a much higher level of pestivirus antigen than the other viral agents evaluated in the study (p < 0.0001). The results of this study indicate that pestiviruses are a common viral cause of ruminant abortions in the examined area.

Molecular Analysis of South African Ovine Herpesvirus 2 Strains Based on Selected Glycoprotein and Tegument Genes

Ovine herpesvirus 2 (OvHV-2), is the causative agent of sheep-associated malignant catarrhal fever (SA-MCF), a generally fatal disease of cattle and other captive wild ruminants. Information on the OvHV-2 strains circulating in South Africa (SA) and other African countries with regard to genetic structure and diversity, and pattern of distribution is not available. This study aimed to characterize the OvHV-2 strains circulating in SA using selected genes encoding glycoproteins and tegument proteins. To establish the genetic diversity of OvHV-2 strains, four genes, Ov 7, Ov 8 ex2, ORF 27 and ORF 73 were selected for analysis by PCR and DNA sequencing. Nucleotide and amino acid multiple sequence analyses revealed two genotypes for ORF 27 and ORF 73, and three genotypes for Ov 7 and Ov 8 ex2, randomly distributed throughout the regions. Ov 7 and ORF 27 nucleotide sequence analysis revealed variations that distinguished SA genotypes from those of reference OvHV-2 strains. Epitope mapping analysis showed that mutations identified from the investigated genes are not likely to affect the functions of the gene products, particularly those responsible for antibody binding activities associated with B-cell epitopes. Knowledge of the extent of genetic diversity existing among OvHV-2 strains has provided an understanding on the distribution patterns of OvHV-2 strains or genotypes across the regions of South Africa. This can facilitate the management of SA-MCF in SA, in terms of introduction of control measures or safe practices to monitor and control OvHV-2 infection. The products encoded by the Ov 7, Ov 8 ex2 and ORF 27 genes are recommended for evaluation of their coded proteins as possible antigens in the development of an OvHV-2 specific serodiagnostic assay.

Co-infection with Bovine Herpesvirus 4 and Histophilus somni Significantly Extends the Service Period in Dairy Cattle with Purulent Vaginal Discharge

The aim of the study was to investigate the effect of Bovine Herpesvirus 4 (BoHV-4) and Histophilus (H.) somni on fertility rate of cows in a Hungarian Holstein-Friesian dairy herd with purulent vaginal discharge (PVD). Non-pregnant cows (n = 188) with mature corpus luteum were treated with cloprostenol and 3 days later if they did not show oestrus, were examined by rectal palpation. Animals showing PVD (n = 60/31.9%/) and 14 controls with normal vaginal discharge (Score 0) were randomly selected and further examined by ultrasonography and blood samples were collected for detecting BoHV-4 DNA and transcervical guarded swabs were collected from the uterus for bacteriological examination. Although the majority of the examined animals were infected with BoHV-4 and H. somni including the control animals as well, in group of animals with PVD score 3, fewer animals became pregnant and the duration between the first treatment to pregnancy was significantly extended. Based on these clinical and comparative data, our results confirm that these two microorganisms together may impair important reproductive parameters which may cause large economic losses to dairy farms.

Molecular Characterization of the First Bovine Herpesvirus 4 (BoHV-4) Strains Isolated from In Vitro Bovine Embryos production in Argentina

Bovine herpesvirus 4 (BoHV-4) is increasingly considered as responsible for various problems of the reproductive tract. The virus infects mainly blood mononuclear cells and displays specific tropism for vascular endothelia, reproductive and fetal tissues. Epidemiological studies suggest its impact on reproductive performance, and its presence in various sites in the reproductive tract highlights its potential transmission in transfer-stage embryos. This work describes the biological and genetic characterization of BoHV-4 strains isolated from an in vitro bovine embryo production system. BoHV-4 strains were isolated in 2011 and 2013 from granulosa cells and bovine oocytes from ovary batches collected at a local abattoir, used as "starting material" for in vitro production of bovine embryos. Compatible BoHV-4-CPE was observed in the co-culture of granulosa cells and oocytes with MDBK cells. The identity of the isolates was confirmed by PCR assays targeting three ORFs of the viral genome. The phylogenetic analyses of the strains suggest that they were evolutionary unlinked. Therefore it is possible that BoHV-4 ovary infections occurred regularly along the evolution of the virus, at least in Argentina, which can have implications in the systems of in vitro embryo production. Thus, although BoHV-4 does not appear to be a frequent risk factor for in vitro embryo production, data are still limited. This study reveals the potential of BoHV-4 transmission via embryo transfer. Moreover, the high variability among the BoHV-4 strains isolated from aborted cows in Argentina highlights the importance of further research on the role of this virus as an agent with the potential to cause reproductive disease in cattle. The genetic characterization of the isolated strains provides data to better understand the pathogenesis of BoHV-4 infections. Furthermore, it will lead to fundamental insights into the molecular aspects of the virus and the means by which these strains circulate in the herds.

[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.

Detection of bovine herpesvirus 2 and bovine herpesvirus 4 DNA in trigeminal ganglia of naturally infected cattle by polymerase chain reaction

Establishment of latent infection within specific tissues in the host is a common biological feature of the herpesviruses. In the case of bovine herpesvirus 2 (BoHV-2), latency is established in neuronal tissues, while bovine herpesvirus 4 (BoHV-4) and ovine herpesvirus 2 (OvHV-2) latent virus targets on cells of the monocytic lineage. This study was conducted in quest of BoHV-2, BoHV-4 and OvHV-2 DNA in two hundred trigeminal ganglia (TG) specimens, derived from one hundred clinically healthy cattle, majority of them naturally infected with bovine herpesvirus 1 (BoHV-1) and bovine herpesvirus 5 (BoHV-5). Total DNA extracted from ganglia was analyzed by polymerase chain reaction (PCR) designed to amplify part of the genes coding for BoHV-2, and BoHV-4 glycoprotein B and, for OvHV-2, the gene coding for phosphoribosylformylglycinamidine synthase-like protein. BoHV-2 DNA was detected in TG samples of two (2%) and BoHV-4 DNA in nine (9%) of the animals, whereas OvHV-2 DNA could not be detected in any of the TG DNA. The two animals in which BoHV-2 DNA was identified were also co-infected with BoHV-1 and BoHV-5. Within the nine animals in which BoHV-4 DNA was detected, six were also co-infected with BoHV-1 and BoHV-5. This report provides for the first time evidence that viral DNA from BoHV-2 and BoHV-4 can be occasionally detected in TG of naturally infected cattle. Likewise, in this report we provided for the first time evidence that the co-infection of cattle with three distinct bovine herpesviruses might be a naturally occurring phenomenon.

Impact of Bovine Herpesvirus 4 (BoHV-4) on Reproduction

Bovine herpesvirus 4 (BoHV-4) is increasingly considered as responsible for various reproductive troubles. This virus infects blood mononuclear cells and displays a specific tropism for vascular endothelia, mammary tissue, endometrium and foetal tissues. Viral multiplication can be reactivated by corticosteroids or stress, both factors present at calving. BoHV-4 has been isolated in a large variety of clinical cases, primarily metritis, vaginitis and mastitis, but also endometritis, abortion and orchitis. Its impact on reproductive performance has been suggested by several epidemiological studies: seroprevalence against BoHV-4 is higher in aborted females and in repeat breeders. Nevertheless, its intrinsic pathogenic power seems low, symptoms developing only when BoHV-4 cooperates with bacteria: within the uterus or mammary gland. BoHV-4 is rather currently considered as a cofactor for the development of an inflammatory reaction initiated by bacteria.

Search for the genome of bovine herpesvirus types 1, 4 and 5 in bovine semen

Bovine herpesvirus type 1 (BoHV-1) causes respiratory and reproductive disorders in cattle. Recently, bovine herpesvirus type 5 (BoHV-5) and bovine herpesvirus type 4 (BoHV-4) have been identified to be associated with genital disease. In this study, the presence of the genome of BoHV-1, BoHV-4 and BoHV-5 in bovine semen of Argentinean and international origin was analyzed by PCR assays. The most important finding of this study is the detection of the genome of BoHV-1 and BoHV-4 in semen of bulls maintained at artificial insemination centers. It is particularly relevant that BoHV-1 DNA was also identified in one sample of international origin suggesting the need for extensive quality control measures on international transport of bovine semen.

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.

Symptomless intrauterine transmission of bovine herpesvirus 4 to bovine fetuses

Blood samples of 31 healthy calves and their dams taken immediately after calving before colostrum uptake, and at days 11, 23 and 8 weeks, spleens of seven stillborn calves were analysed in order to determine the source and time of bovine herpesvirus type 4 infection. All the calves were born as seronegatives, while all cattle were seropositives. Viral DNA were amplified by a nested PCR assay from 54.8% of peripheral blood leukocyte samples of newborn calves taken before colostrum uptake, and from all cattle and from their colostrums. Real time PCR detected higher virus level in peripheral blood leukocytes in adult cattle, then in their newborn calves. Bovine semen cells (spermatozoa and leukocyte fractions), spleens of stillborn calves also carried viral genomes. Our results prove, that bovine fetuses can be infected in utero by BoHV-4, but are born as seronegatives. After human examples this is the first report in veterinary virology on intrauterine transmission of a herpesvirus without acute consequences. This phenomenon could explain the low antigenicity of BoHV-4 proteins and lack of neutralizating antibodies. BoHV-4, a gammaherpesvirus, could serve as an animal model for studying inapparent herpesviral infections of human fetuses.

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.

Detection of bovine herpesvirus 4 DNA in aborted bovine fetuses

The presence of Bovine herpesvirus 4 (BoHV-4) was investigated by several methods in 24 aborted bovine fetuses. Polymerase chain reaction (PCR) and in situ DNA hybridization proved the presence of BoHV-4 DNA in 7 (29%) of the fetuses. The BoHV-4 genome was detected in the cytoplasm of splenic lymphocytes and monocytes, and sometimes in renal tubular epithelial cells or hepatic Kupffer cells, in all 7 PCR-positive fetuses. However, BoHV-4-specific monoclonal antibody failed to detect viral antigen in the formalin-fixed, paraffin-embedded tissue samples. No bacterial pathogens were found in the tissues of the BoHV-4-positive fetuses. Fungi were detected in 1 sample, and antibody to bovine viral diarrhea virus was detected in another. These results indicate that BoHV-4 could play a role in reproductive disorders of cattle, including abortion.

An investigation of the aetiological role of bovine herpesvirus 4 in bovine endometritis

Uteri from 31 infertile cattle were examined for the presence of bovine herpesvirus 4 (BoHV-4) by nested polymerase chain reaction (PCR). Samples were also tested for bacteria, including chlamydiae and Mycoplasma bovis. BoHV-4 was detected by PCR in 27/31 (87.1%) samples, but the presence and amount of viral DNA was not correlated with histological and bacteriological findings. Arcanobacterium pyogenes, Histophilus somni and Pasteurella multocida were isolated from five cows with endometritis. Chlamydiae were detected in four cases (12.9%), but only two of these had endometritis. The study does not support a role for BoHV-4 as primary agent in bovine endometritis.

Detection of bovine herpesvirus 4 in aborted bovine placentas

Diagnostic studies on aborted placentas of cattle usually do not determine any reason for abortions. In this paper, five bovine herpesviruses (BoHVs) and some bacteriological agents were investigated by several methods in 33 aborted bovine placentas. Inclusion bodies, PCR and in situ DNA hybridization proved the presence of BoHV-4 DNA in six (18.18%) tested placentas. Positive DNA hybridization signal localized BoHV-4 DNA to placental epithelial cells macrophages and lymphocytes. By destroying epithelial cells and provoking local immune response BoHV-4 infection may inhibit physiological functions of the placenta during gestation. This finding is a further sign that BoHV-4 plays an active role in reproductive disorders of cattle.

Characterization of Bovine Herpesvirus Type 4 Isolated from Cattle with Mastitis and Subclinical Infection by the Virus among Cattle

An outbreak of contagious mastitis occurred among cattle on a farm, and bovine herpesviruses were isolated from the affected mammary tissues, scabs and abscess discharge of the cattle. A bovine herpesvirus type 4 (BoHV-4)-specific fragment was amplified from the isolates by polymerase chain reaction (PCR). Restriction endonuclease analyses demonstrated that the isolates were related to Movar-like European type BoHV-4. To determine the ratio of BoHV-4 subclinical infection in the cattle, a genomic survey was performed by PCR for cattle that were moved to the animal hygiene service station in Ibaraki prefecture. The BoHV-4 genome was occasionally detected in peripheral blood leukocytes, lymph nodes and nervous tissues. The rate of BoHV-4 subclinical infection was relatively high in the cattle.

Detection of bovine herpesvirus 4 in CD11b+ leukocytes of experimentally infected rabbits

The presence and numbers of bovine herpesvirus 4 (BoHV-4) infected CD11b+ leukocytes were investigated during experimental infections of New Zealand White rabbits by Fluorescence Activated Cell Sorter (FACS) analysis. Peripheral blood leukocytes (PBL) were collected every second day, and the cells were stained with phycoerythrin-labelled CD11b-specific mouse monoclonal antibody and fluorescein-conjugated bovine herpesvirus 4-specific mouse monoclonal antibody. The numbers of double-stained cells from PBLs of the control and inoculated groups were measured and compared in FACSTREK analyser. Double-stained cells were detected in the virus-inoculated group on postinoculation days (PID) 2-5 and 9-12. The results indicated that CD11b+ PBLs were permissive for BoHV-4 infection, and are probably the main reservoir of the virus during the latent period. The data did not indicate production of infectious viral particles, but virus-specific proteins were expressed on the surface of CD11b+ cells. The two waves of double-stained cells gave similar results to the PCR assays from serum samples, which showed the presence of viral DNA in the serum on the same days when virus-infected CD11b cells were also present. Productive BoHV-4 infection of mast cells or undifferentiated leukocytes in the bone marrow and the antiviral immune response might be responsible for this periodic appearance of the virus in CD11b+ PBLs and in the serum. The paper provides evidence that CD11b+ PBLs are the main target cell populations in the blood for BoHV-4.

Bovine herpesvirus 4-associated postpartum metritis in a Spanish dairy herd

In more than 10 Spanish dairy cows, a bovine herpesvirus 4 (BHV4) associated postpartum metritis was confirmed by virus isolation, BHV4-glycoprotein B (gB) PCR and/or serology. In this study, 12 cows with, and, at the time of sampling, 3 cows without clinical signs of acute postpartum metritis from one large dairy herd in Spain were examined for bacterial and viral infections. Blood, placenta/caruncles and uterine contents were collected between day 1 and day 20 post-calving, and examined for the presence of bacteria and for viruses by virus isolation, BHV4 DNA by BHV4-gB PCR and/or BHV4 antibody titres. Bovine herpesvirus 4 was detected in 83% of the cases with clinical signs of acute postpartum metritis by virus isolation and/or BHV4-gB PCR. An increase of BHV4 antibodies was detected in all examined postpartum metritis cows and in the 3 cows without clinical metritis. Two of these 3 cows developed severe metritis a few dayss after collecting the first blood sample. A concurrent infections of BHV4 and bacteria, mainly Arcanobacterium pyogenes and Streptococcus sp., were detected in 73% of the examined uterine contents collected from postpartum metritis affected cows. This case-report study showed a clear association between BHV4 infections and acute postpartum metritis in dairy cows. In addition, the BHV4-associated postpartum metritis appeared to be an emerging syndrome in this Spanish herd.

Role of bovine herpesvirus 4 in bacterial bovine mastitis

In order to study the role played by bovine herpesvirus 4 (BoHV-4) in bovine mastitis, PCR experiments were performed on a Hungarian dairy herd of 2000 cows. Milk cells were tested with a nested PCR adjusted to detect the virus in the milk. Thirty to forty-one percentage of the udders of 101 cows with bacterial mastitis (Escherichia coli, Streptococcus uberis or Staphylococcus aureus) gave positive results, whereas less than 6% of the milk samples were positive for BoHV-4 from 118 animals with healthy udders. The mastitis status of these 118 healthy cows was followed throughout the milking period; 4.2% had clinical, and 25.42% had subclinical mastitis. By the end of the milking period, more than 90% of the cows shed the virus in their milk, regardless of the bacterial status of the udder. No correlation was found between the virus shed, the somatic cell count, and the bacterial status of the udder. Viral DNA was detected in the wall of the milk duct. These results demonstrate that BoHV-4 neither causes mastitis directly nor plays a role in the initiation of the process, but later, when bacterial infection of the udder occurs, the reactivated virus replicates in the immune cells of the udder and/or in the epithelial cells of the milk ducts and may be responsible for more severe, prolonged mastitis. As mastitis is a crucial problem of milk production, this virus may be considered a possible predisposing factor and also an agent of secondary udder infections in prolonged mastitis cases.

Detection of bovine gammaherpesviruses by a nested duplex PCR

The two bovine gammaherpesviruses (Alcelaphine herpesvirus 1, AlHV-1; Bovine herpesvirus 4, BoHV-4) are distributed worldwide in cattle populations. Since the animals are frequently infected latently with no or low seropositivity, a DNA based diagnostic method would be useful for surveys and detection of these viruses. In the present study a nested duplex PCR was established for the sensitive and specific simultaneous detection of both viruses. The primers were designed for the gene of the major capsid protein (ORF25). The assay did not amplify the capsid gene sequence of 10 related bovine herpesviruses and other gammaherpesviruses. The test was able to detect 1pfu (plaque forming unit) of AlHV-1 and BoHV-4. Among 146 clinical samples (lymph nodes and peripheral blood leukocytes, PBLs) 65 (44.52%) were found to be positives for AlHV-1 and 84 (57.53%) for BoHV-4. This nested duplex PCR assay could serve as a useful diagnostic method for rapid, sensitive, specific simultaneous detection of the two bovine gammaherpesviruses.

Mammary Lesions Associated with Bovine Herpesvirus Type 4 in a Cow with Clinical Mastitis

Intranuclear eosinophilic inclusion bodies were seen in the lactiferous duct and sinus epithelium of mammary tissues collected from a cow with clinical mastitis. Transmission electron microscopy revealed herpesvirus particles in these cells. Immunolabeling against anti bovine herpesvirus type 4 (BHV-4) rabbit serum was detected in nuclei that had intranuclear inclusion bodies. In addition, BHV-4 was isolated from the mammary tissue. The viral DNA was detected by nested PCR from the same tissue. This is the first report to describe mammary lesions in association with BHV-4.

Use of a polymerase chain reaction assay to detect bovine herpesvirus type 2 DNA in skin lesions from cattle suspected to have pseudo-lumpy skin disease

Beef cattle from a herd in north Alabama were examined because of an outbreak of nonfatal skin disease characterized by discrete circumscribed areas of inflammation that developed on the skin from the neck to the hips. Areas of inflammation, which tended to be superficial, underwent necrosis and scabbed over. The scabs eventually dropped off leaving discrete, round, whitish, hairless lesions that were 1.2 to 2.5 cm diameter. Because clinical signs were consistent with those expected with pseudo-lumpy skin disease (PLSD) caused by bovine herpesvirus type 2 (BHV-2), samples from 16 representative animals were submitted for BHV-2 testing. All 16 animals were seropositive for BHV-2, but the virus could not be isolated from skin biopsy specimens or buffy coat samples. Results of a polymerase chain reaction assay incorporating primers designed to amplify 2 DNA sequences from BHV-2 were positive for 3 of the 10 cattle, suggesting that skin lesions in these cattle were a result of PLSD. Our findings suggest that PLSD may be more common and widespread in the United States than suggested by the frequency with which BHV-2 has been isolated from cattle with PLSD-like skin lesions.

Histological lesions in vascular tissues of bovine herpes virus type 4-infected rabbits

The gamma-herpes virus bovine herpes virus type 4 (BoHV-4) is distributed worldwide in cattle populations with unknown pathogenicity. Bovine endothelial cells were recently shown to be susceptible to BoHV-4 infection in vitro and this virus accelerated the cholesterol-induced atherosclerotic process in rabbits. In this study, the in vivo effect of BoHV-4 on cardiovascular tissue was investigated by intravenous infection of rabbits fed a cholesterol free diet. Inflammatory lesions of vascular tissue in aortic and valvular endothelial cells, and smooth muscle cells were detected by H&E staining, PCR, IF, EM immunohistochemistry, while virus isolation was used to detect virus particles. Acute and chronic vasculitis, signs of chronic endocarditis, with mononuclear cell accumulation and a fresh thrombus was found. Herpes viruses have already been thought to initiate cardio-vascular disorders, now this paper shows that a bovine gamma-herpes virus could also be a causative agent of vascular lesions in mammals fed a normal diet. BoHV-4-infection of rabbits could serve as a useful animal model for research into virus-induced human cardio-vascular diseases.

Latency and persistence of bovine herpesvirus type 4, strain B11-41, in bovine nervous tissues

Three cattle were experimentally infected with bovine herpesvirus type 4 (BoHV-4), strain B11-41, isolated from the spinal cord of a cow, and monitored for clinical symptoms. None of them showed any clinical signs except increases of leukocyte numbers in two of them, and the body temperature remained normal throughout the experiment. Antibody titers against BoHV-4 continuously increased for one month and were maintained at a high level for more than 1 year by enzyme-linked immunosorbent assay (ELISA). The virus was isolated only from serum and peripheral blood leukocytes (PBL) of one cow in the early stage of infection, but the viral genome was detected in PBL continuously by PCR. When they were euthanized, the viral genome was detected in the lymph nodes and nervous tissues such as medulla, spinal cord, and trigeminal ganglion. These results indicate that cattle are infected with the virus latently and persistently, and the latency site would be in the tissues of the central nervous system as well as lymphoid tissues. When a seroepidemiological survey was performed on antibodies to BoHV-4 among cattle in Japan by ELISA, the rate of antibody-positive cattle was 8.9% and they were found irregularly on certain farms.

Seroprevalence and comparison of isolates of endometriotropic bovine herpesvirus-4

Sixty-eight cases of suppurative, ulcerative endometritis associated with Bovine Herpesvirus-4 (BHV-4) in postparturient dairy cows (62 Holsteins and 6 Jerseys, mean age 4.2 years) were confirmed by a combination of histopathology, fluorescent antibody assays, electron microscopic evaluation of uterus, and polymerase chain reaction (PCR). All cases occurred in the 3- to 28-day postpartum period, and histologic lesions among various cows were consistent when compared with postpartum interval. The endometrial lining epithelium was necrotic and ulcerated from 3 to 7 days postpartum, with only mild inflammation in the lamina propria and submucosa. From 1 to 4 weeks postpartum, the ulcers were confluent to diffuse. Epithelium was replaced by fibrinonecrotic, suppurative mats, resulting in severe bacterial pyometra by day 24. Seroprevalence to BHV-4 in one dairy with a history of 18 mortality cases was 36% (107 of 296). In a random sample of 8 cows from this herd, none had serologic titers in blood sampled 2 weeks prepartum, but 3 of 8 seroconverted with significant titers of 1:8 to 1:16 at 2 weeks postpartum. By 10 weeks postpartum, all 8 cows returned to negative serologic status. Two of 6 cats from the premises also had positive titers. Random serum samples taken from 480 dairy cattle at sale barns indicated 76 (16%) were positive by serum neutralization. Clinical signs, postparturient timing, and histologic lesions were very similar to those previously reported in Belgium with BHV-4. But sequence analysis of PCR products of the glycoprotein B region of 4 separate field isolates of endometriotropic BHV-4 suggests these field isolates were more closely related to the North American nonvirulent strain DN-599 than to the endometriotropic European strain V.

VirOligo: a database of virus-specific oligonucleotides

VirOligo is a database of virus-specific oligonucleotides. The VirOligo database consists of two tables, Common data and Oligo data. The Oligo data table contains PCR primers and hybridization probes used for detection of viral nucleic acids and the Common data table contains the experimental conditions used in their detection. Each oligonucleotide entry contains links to PubMed, GenBank, NCBI Taxonomy databases and BLAST. As of July 2001, the VirOligo database contains a complete listing of oligonucleotides specific to viral agents associated with bovine respiratory disease that were published in English in peer-reviewed journals. The viruses are bovine herpes virus types 1, 3, 4 and 5, bovine viral diarrhea virus, bovine parainfluenza 3 virus, bovine respiratory syncytial virus, bovine adenovirus, bovine rhinovirus, bovine coronavirus, bovine reovirus, bovine enterovirus and alcelaphine herpesvirus-1. The VirOligo database is being expanded to other viruses and can be accessed through the Internet at http://viroligo.okstate.edu/.

New histochemical and ultrastructural observations on normal bovine tonsils

Samples of normal bovine palatine tonsils were examined by light and electron microscopy. Like human tonsils, they were composed of crypts, subepithelial areas, follicles, and T-dependent zones, but their well-developed capsule subdivided the lymphoid tissue by connective septa. B cells formed the major lymphoid component. The follicles and T-dependent zones had morphological and histochemical features typical of peripheral lymph organs. Follicular dendritic cells were isolated and shown to be similar to human follicular dendritic cells.

Endometritis in postparturient cattle associated with bovine herpesvirus-4 infection: 15 cases

Suppurative, ulcerative endometritis associated with bovine herpesvirus-4 (BHV-4) infection was identified in 15 postparturient dairy cows from 5 separate dairies. Characteristic eosinophilic to amphophilic intranuclear viral inclusion bodies were identified within degenerate endometrial lining epithelium and endothelial cells. Bovine herpesvirus-4 was confirmed as the etiology by a combination of fluorescent antibody assays, viral isolation, heminested PCR, ultrastructural examination of the uterus and inoculated tissue culture cells, and negative-stain electron microscopy of tissue culture supernatant. Viral particles measuring 70-95 nm were demonstrated in uterine epithelial and endothelial cells by electron microscopy. Bacteria including Arcanobacterium pyogenes, Escherichia coli, and an alpha-Streptococcus isolate were isolated from all uteri. Bovine herpesvirus-4-associated endometritis has been previously reported in sporadic cases in Europe but has not been previously reported in the United States. Endometritis associated with BHV-4 appears to be an emerging syndrome in Georgia dairy herds.

Detection of bovine herpesvirus 4 glycoprotein B and thymidine kinase DNA by PCR assays in bovine milk

A polymerase chain reaction (PCR) assay was developed to detect bovine herpesvirus 4 (BHV4) glycoprotein B (gB) DNA, and a nested-PCR assay was modified for the detection of BHV4 thymidine kinase (TK) DNA in bovine milk samples. To identify false-negative PCR results, internal control templates were constructed, added to milk samples, and co-amplified with viral DNA using the same primers for both templates. Specificity, sensitivity, and reproducibility of the two PCR assays were examined. In both PCR assays, all 31 BHV4 strains examined were scored positive, whereas 14 unrelated viruses scored negative. Sensitivity studies showed that two-ten copies of BHV4 DNA were detectable by the gB-PCR, while one-three copies could be detected by the TK-PCR. For the detection of BHV4 in milk samples, the gB-PCR amplification was found to be ten-times, and the TK-PCR was found to be 55-times more sensitive than virus isolation. BHV4 DNA was detected by gB-PCR and TK-PCR in 93 and 95%, respectively, of 61 milk samples collected from cows infected intramammarily with BHV4, while only 61% were positive by virus isolation. Four out of 48 cows with clinical mastitis were positive for BHV4-gB and BHV4-TK DNA, whereas no BHV4 DNA was detected in milk from control cows. Considerable agreement was seen between the results of the two PCR assays, and both methods were considered as rapid and reliable tests for the screening of BHV4 DNA in bovine milk. The less laborious gB-PCR might be the recommended test of choice for screening large amounts of milk samples for the presence of BHV4.

Detection of bovine herpesvirus 4 (BoHV-4) DNA in the cell fraction of milk of dairy cattle with history of BoHV-4 infection

We have demonstrated, by PCR and restriction enzyme analysis of the PCR product, the presence of bovine herpesvirus 4 (BoHV-4) DNA in the cell fraction of milk from dairy cattle with a history of BoHV-4 infection. We next evaluated the infectious nature of BoHV-4 DNA in those cells. Cocultivation of a BoHV-4-sensitive cell line with BoHV-4 DNA-positive milk cell samples produced cytopathic effects. The same result was obtained from frozen and thawed milk cell fraction coming from the cell milk fraction PCR-positive cows, ensuring that cells were killed and only infectious virus could be recovered after cocultivation with sensitive cells. This report shows that infectious BoHV-4 can be present in milk cells and that therefore nursing may be one of the transmission routes of BoHV-4.

Genomic and pathogenic studies on a glycoprotein E variant field isolate of bovine herpesvirus 1

Glycoprotein E-negative (gE-) laboratory strains of bovine herpesvirus 1 (BHV-1) were recently introduced as novel marker vaccines, allowing serological discrimination between vaccinated and naturally infected animals on the basis of lack or presence of antibodies against gE epitopes. The applicability pf this approach is based on the genetic stability of the gE. However, mutant field variants of BHV-1 with a variable response in anti-gE ELISA have been isolated. The molecular characterization of a gE variant field isolate (Salwa strain) is presented here. By comparing the gE nucleotide and amino acid sequences of the Salwa strain with those of the wild strain Jura, ten mutated bases were found in the gE strain of Salwa, six of which alter the amino acid sequence, leading to changes in five amino acids. Both strains caused respiratory disease in experimentally infected calves, but Salwa generated slightly milder signs. Both viruses were excreted in nasal and ocular discharges, and were reactivated by dexamethasone treatment. In conclusion, the rather close similarities observed in the gE gene structure and pathogenicity features of the gE mutant and of the wild strain of BHV-1 confirm the genetic stability of gE. The findings indicate that the Salwa isolate is virulent, but less virulent than wild strains. Our data support the use of gE-negative marker vaccines in eradication programmes.

Experimental infection with bovine herpesvirus-4 enhances atherosclerotic process in rabbits

An association of herpesvirus and atherosclerosis has been suggested by seroepidemiologic studies and detection of the virus in arterial tissues. To facilitate the studies of the pathogenic role of herpesvirus in atherosclerosis, we established a rabbit model of atherosclerosis with bovine herpesvirus type-4 (BHV-4). Forty New Zealand White rabbits were randomly divided into six groups. Groups 1, 2, and 3 were inoculated iv with BHV-4 and control Groups 4, 5, and 6 with normal saline. Groups 1 and 4 were fed a regular diet throughout the experiment; Groups 2 and 5 were fed a diet supplemented with 2% cholesterol for 3 weeks starting at 3 weeks postinoculation; and Groups 3 and 6 with a diet supplemented with 2% cholesterol for 6 weeks starting at 3 days postinoculation. Extensive atherosclerotic lesions in Groups 2, 3, and 6, and small lesions in two rabbits in Group 1 were observed, but no obvious lesions were observed in Groups 4 and 5. BHV-4 DNA was demonstrated by polymerase chain reaction and liquid hybridization in aortic sections, various tissue samples, and peripheral blood mononuclear cells of all infected rabbits. Our studies demonstrated that BHV-4 can accelerate the atherosclerotic process in rabbits, and that experimental infection of rabbits with BHV-4 can be a useful atherosclerosis model.

A sensitive and specific PCR/Southern blot assay for detection of bovine herpesvirus 4 in calves infected experimentally

A PCR/Southern blot assay for detection of bovine herpesvirus 4 (BHV-4) in the background of bovine cellular DNA was developed. A BHV-4 specific sequence within the gene coding for the glycoprotein B (gB) was selected for primer sequences to guarantee the specificity of the assay. With a detection limit of six molecules BHV-4 DNA in the background of 1 microg of cellular DNA (equals about 150,000 bovine cells) this PCR/Southern blot assay represents a highly sensitive method for detection of BHV-4 DNA. At low concentrations of BHV-4 genomes, this assay also allows to estimate the copy number of BHV-4: a distinction between fewer than 6, 6-59 and more than 60 BHV-4 genomes/100 microl DNA suspension was possible. Tissue and blood samples of two calves, infected experimentally with BHV-4 were examined for the prevalence of BHV-4 DNA 130 days post infection. Ten days before taking samples, one of the calves was immuno-suppressed with dexamethasone. In both calves, BHV-4 DNA was detected in the leucocyte fraction of the blood, and beyond that in lower quantities in the spleen and the kidney of the immuno-suppressed calf. It is assumed that a latent BHV-4 infection was activated after application of dexamethasone and that the leucocyte fraction of the blood represents one site of latency of BHV-4 in cattle.

Persistent infection of bovine herpesvirus type 4 in bovine endothelial cell cultures

Herpesviruses can establish a persistent infection in the cells and tissues of their natural hosts and thus may produce diseases due to cytolytic infections. We have isolated a herpesvirus from a bovine vascular endothelial cell culture after continuous subculturing. Typical cytopathic changes were observed in bovine endothelial cell cultures 2 days after inoculation of the virus. The virus had an icosahedral nucleocapsid of 100-150 nm in diameter and an envelope. The sequences of some DNA fragments of the virus were highly homologous to those of the bovine herpesvirus type 4 (BHV-4) strains. The DNA restriction maps of the virus and the reference strains of BHV-4, DN 599 and Movar 33/63 were very similar but not identical. Therefore, the newly isolated virus has been designated Taiwan strain. The presence of BHV-4 DNA in apparently normal bovine endothelial cell cultures was shown by Southern blot hybridization with the BamHI fragment of the newly isolated BHV-4 and was further confirmed by digestion of the DNA with BamHI plus AccI. In conclusion, we have demonstrated that BHV-4 persisted in the bovine endothelial cell cultures and continuous subcultures could lead to the production of infectious viral particles.