Neutralizing antibodies to bovine herpesvirus types 1 (BoHV-1) and 5 (BoHV-5) and its subtypes

Humoral Immune Response of Mice against a Vaccine Candidate Composed of a Chimera of gB of Bovine Alphaherpesviruses 1 and 5

Infectious bovine rhinotracheitis (IBR) and bovine meningoencephalitis are caused by Bovine alphaherpesvirus (BoHV) types 1 and 5, which seriously threaten the global cattle industry. Vaccination to improve immunity is the most direct and effective means to prevent these conditions. Glycoprotein B (gB) is essential for the attachment of both viruses to permissive cells, and is a major target of the host immune system, inducing a strong humoral response. The aim of this study was to evaluate, in a murine model, the immune response of a candidate vaccine formulation composed of a chimeric BoHV-1 and BoHV-5 gB (DgB), expressed in Komagataella phaffii. The chimeric DgB vaccine adjuvanted with Montanide 50 ISA V2 or aluminum hydroxide was administered intramuscularly or subcutaneously. A control group and a group that received a commercial vaccine were inoculated subcutaneously. Higher titers of neutralizing antibodies against BoHV-1, BoHV-5, and a natural BoHV-1/5 recombinant strain were obtained with the oil-based candidate vaccine formulation administered intramuscularly. The results demonstrated that the chimeric DgB conserved important epitopes that were able to stimulate a humoral immune response capable of neutralizing BoHV-1, BoHV-5, and the recombinant strain, suggesting that the vaccine antigen is a promising candidate to be further evaluated in cattle.

Neutralizing antibodies to bovine and bubaline alphaherpesviruses in water buffaloes (Bubalus bubalis)

Water buffaloes (Bubalus bubalis) have been introduced in many regions of the world as a source of animal protein. In many instances, bubaline cattle are reared close to or mixed with bovine or zebuine cattle. However, little is known about infectious diseases of bubaline and the interactions that may arise involving the microbiota of those species. Alphaherpesviruses of ruminants (bovine alphaherpesviruses types 1 and 5, BoHV-1, BoHV-5; bubaline alphaherpesvirus 1, BuHV-1) are highly cross-reactive in serological assays performed with bovine or zebuine sera. However, the profile of reactivity of bubaline cattle sera to alphaherpesviruses remains unknown. As such, it is not known which virus strain (or strains) would be most appropriate to be used as the challenge virus in the laboratory in search for alphaherpesvirus-neutralizing antibodies. In this study, the profile of neutralizing antibodies to alphaherpesviruses in bubaline sera was determined against different types/subtypes of bovine and bubaline alphaherpesviruses. Sera (n=339) were screened in a 24-h serum neutralization test (SN) against 100 TCID50 of each of the challenge viruses. From those, 159 (46.9 %) neutralized at least one of the viruses assayed; 131 (38.6%) sera neutralized the three viral strains used for screening. The viral strain that was neutralized by the largest number of sera was BoHV-5b A663 (149/159; 93.7%). A few sera neutralized only one of the challenge viruses: four sera neutralized BoHV-1 LA only; another neutralized BoHV-5 A663 only and four others neutralized BuHV-1 b6 only. SN testing with two additional strains gave rise to similar results, where maximum sensitivity (defined here as the largest number of sera that neutralized the challenge viruses) was obtained by adding positive results attained with three of the challenge strains. Differences in neutralizing antibody titers were not significant to allow inferences on which would be the most likely virus that induced the antibody responses detected here.

An ELISA to Detect Antibodies to Bovine Alphaherpesviruses 1 and 5 and Bubaline Alphaherpesvirus 1 in Cattle Sera

Bovine alphaherpesvirus 1 (subtypes 1.1, 1.2a, and 1.2b), type 5 (subtypes 5a, 5b, and 5c), and bubaline herpesvirus 1 (BuHV-1) induce highly, though not fully cross-reactive serological responses. Most types and subtypes of these viruses circulate particularly in countries of the southern hemisphere, notably Brazil and Argentina. Therefore, the detection of infected animals is important in defining prevention and control strategies, particularly when flocks are destined for international trade. Identification of infected herds is most often achieved by assays that detect antibodies, such as enzyme immunoassays (ELISAs). However, to date, no ELISA has been evaluated in its capacity to detect antibodies to these alphaherpesviruses. Here, an ELISA was developed to detect antibodies to all currently recognized BoAHV-1, BoAHV-5, and BuAHV-1 types/subtypes, and its sensitivity and specificity were determined. Six hundred bovine sera were screened in serum neutralization tests (SN) against the seven viruses. ELISAs prepared with each of the viruses were compared to SN. Subsequently, a combined assay with multiple antigens LISA was prepared by mixing five viral antigens, chosen for their highest sensitivity in the preparative assays. In comparison to SN, the mAgELISA sensitivity was 96.5% with 96.1% specificity (κ = 0.93; PPV = 95.0%; NPV = 97.3%). The findings reveal that the mAgELISA developed here is highly suitable for the detection of antibodies, comparable in sensitivity and specificity to that of SN when performed with all known types and subtypes of bovine and bubaline alphaherpesviruses.

Field Evaluation of Commercial Vaccines against Infectious Bovine Rhinotracheitis (Ibr) Virus Using Different Immunization Protocols

Bovine alphaherpesvirus 1 is ubiquitous in cattle populations and is associated with several clinical syndromes, including respiratory disease, genital disease, infertility and abortions. Control of the virus in many parts of the world is achieved primarily through vaccination with either inactivated or live modified viral vaccines. The objective of this study was to evaluate the performance of four commercially available BoHV-1 vaccines commonly used in Central and South America. Animals were divided into eight groups and vaccinated on days 0 and 30. Groups 1 to 4 received two doses of four different BoHV-1 commercial vaccines (named A to D). Groups 5 and 6 received vaccine D plus a vaccine for either Clostridial or Food-and-Mouth-Disease (FMD), respectively. Group 7 received one dose of two different brands of reproductive vaccines. Serum samples were collected from all animals on days 0, 30 and 60 to evaluate neutralizing and isotype-specific (IgG1 and IgG2) antibodies. Of the four commercial vaccines evaluated, only vaccine A induced neutralizing antibodies to titers ≥ 1:8 in 13/15 (86%) of the animals 60 days post-vaccination. Levels of IgG2 antibody increased in all groups, except for group 2 after the first dose of vaccine B. These results show that only vaccine A induced significant and detectable levels of BoHV-1-neutralizing antibodies. The combination of vaccine D with Clostridial or FMD vaccines did not affect neutralizing antibody responses to BoHV-1. The antibody responses of three of the four commercial vaccines analyzed here were lower than admissible by vaccine A. These results may be from vaccination failure, but means to identify the immune signatures predictive of clinical protection against BoHV-1 in cattle should also be considered.

Bacillus Toyonensis BCT-7112T Spores as Parenteral Adjuvant of BoHV-5 Vaccine in a Murine Model

Bacterial spores of the genus Bacillus are being evaluated as adjuvant molecules capable of improving the immune response to vaccines. In this study, we investigate whether subcutaneously administered spores of B. toyonensis BCT-7112^T could enhance a vaccine immune response in mice. Three groups of mice were subcutaneously vaccinated on day 0 and received a booster on day 21 of the experiment, with the following vaccine formulations: 40 µg of recombinant glycoprotein D (rgD) from bovine herpesvirus type 5 (BoHV-5) adsorbed in 10% aluminum hydroxide (alum) without B. toyonensis spores (group 1) and B. toyonensis (1 × 10⁶ viable spores) + 40 µg of rgD adsorbed in 10% alum (group 2); and B. toyonensis (1 × 10⁶ viable spores) without rgD (group 3). Group 2 showed significantly higher titers (P < 0.05) of total specific serum IgG, IgG2a, and neutralizing antibodies, when compared with the groups 1 and 3. A significantly higher (P < 0.05) transcription level of cytokines IL-4, IL-12, and IFN-γ was observed in splenocytes from mice that received the B. toyonensis spores in the vaccine formulation. In addition, stimulation of the macrophage-like cell line RAW264.7 with spores of B. toyonensis markedly enhanced the cell proliferation and mRNA transcription levels of IL-4, and IL-12 cytokines in these cells. Our findings indicated that the subcutaneous administration of B. toyonensis BCT-7112^T spores enhanced the humoral and cellular immune response against BoHV-5 in mice.

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

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

Molecular and antigenic characterization of bovine herpesvirus type 1 (BoHV-1) strains from cattle with diverse clinical cases in Turkey

The present study reports the molecular and antigenic characterization of 13 bovine herpesvirus type 1 (BoHV-1) field viruses obtained from cattle with different clinical cases in Turkey between 1992 and 2017. We selected glycoprotein C (gC) of BoHV-1 as a target to detect and/or verify presence of the virus in suspect materials followed by virus isolation (VI) in MDBK cells. In seven out of 13 BoHV-1 positive samples, cytophatic effects (CPEs) were observed in MDBK cell cultures, although only four virus samples reached a sufficient titer to use in phylogenetic assay, restriction endonuclease analysis (REA), and virus neutralization test (VNT). According to the results of sequence analysis of the 13 BoHV-1 positive samples, nine BoHV-1 field viruses were determined as BoHV-1.1 and four as BoHV-1.2. Using REA, we demonstrated that two of our isolated viruses could be categorized as BoHV-1.1 while the other two isolates were BoHV-1.2 subtypes. Differences between the BoHV-1.1 and BoHV-1.2 isolates were also detected in the VNT results by assaying 125 suspected serum samples after testing with isolated (KY748023, KY748022, KY748020, and KY748021) and reference viruses (BoHV-1 Cooper and BoHV-5 Texas 89). These results are indicating the need to correctly identify BoHV-1 field isolates to better understand the epidemiology and pathogenesis of infection. In addition, it would be useful to identify the subtypes circulating in the specific geographical area while determining vaccination preferences.

Bovine alphaherpesvirus 1 and 5 in semen from bulls presenting genital lesions under field conditions in Brazil

ABSTRACT Bovine alphaherpesviruses 1 and 5 (BoHV-1/5) are main pathogens of respiratory, reproductive and neurological diseases in cattle. The aim of this study was to investigate the frequency of neutralizing antibodies against BoHV-1/5 in serum samples and to detect viral DNA in semen of bulls from beef cattle farms located in RS. A total of 372 serum and semen sample from bulls were collected in eighteen farms. Serum samples were submitted to virus neutralization (VN) assay, while semen samples were used to detect BoHV-1 and BoHV-5 DNA by PCR. VN results showed that BoHV-1/5 antibodies were detected in bulls of 66.7% (12/18) of the farms, 295 (79.5%) BoHV positive bulls, 287 for BoHV-1 and 234 for BoHV-; at 43 vaccinated bulls 72.1% (31/43) showing serology negative. BoHV-1/5 DNA was detected in the semen of three bulls; one of the them presenting BoHV-1, one out three presenting BoHV-5 and one BoHV-1/5.co-infection All BoHV DNA positive samples came from animals presenting posthitis and other genital lesions at sampling. Results showed a high seroprevalence of BoHV-1/5 antibodies in bulls as well as strong evidence that these viruses are actively circulating in the cattle farms. A remarkable finding is that in the presence of clinically evident lesions in the genital tract, both BoHV-1 and 5 may found in semen.

RETRACTED: Bovine Herpesvirus 5 promotes mitochondrial dysfunction in cultured bovine monocyte-derived macrophages and not affect virus replication

This article has been retracted: please see Elsevier Policy on Article Withdrawal (https://www.elsevier.com/about/our-business/policies/article-withdrawal). This article has been retracted at the request of the Editors-in-Chief and Authors. Fig 1A is a duplicate of a figure that has already been published in da Silva SEL et al. Archives of Virology 2018;163:1043-1049; 10.1007/s00705-018-3704-2. These two papers report studies performed with cells from two different animal species (bovine cells for the Veterinary Microbiology paper and chicken cells for the Archives of Virology paper). The reuse of the same figure in the Veterinary Microbiology paper to describe cells that were supposed to be from a different species is thus inappropriate and also puts into question the reliability of the other results presented in this paper. In addition, the Editors-in-Chief have remaining concerns about the strong similarities of other data presented in the two papers. Even if these concerns were addressed, the re-use of any data has to be clearly indicated and appropriately cited. As such this article represents a misuse of the scientific publishing system. The scientific community takes a very strong view on this matter and apologies are offered to readers of the journal that this was not detected during the submission process.

Immune responses in bovines to recombinant glycoprotein D of bovine herpesvirus type 5 as vaccine antigen

Bovine herpesvirus 5 (BoHV-5) is responsible for outbreaks of meningoencephalitis that cause important economic losses in young cattle. BoHV-5 glycoprotein D (gD5) is essential for attachment and penetration into permissive cells and targeting of host immune systems, inducing strong humoral and cellular immune responses. The aim of this study was to evaluate the vaccinal immune response of vaccines formulated with the recombinant BoHV-5 gD (rgD5) in bovines. For the experiment, 72 heifers were randomly allotted into 6 different groups with 12 animals each. Group 1: vaccine formulated using inactivated BoHV-5 (iBoHV-5) adjuvanted with ISA50V2; Group 2: iBoHV-5 associated with 100 µg of rgD5 adjuvanted with ISA50V2; Group 3: 100 µg of rgD5 adjuvanted with ISA50V2; Group 4: 100 µg of rgD5 adjuvanted with Al(OH)₃; Group 5: commercial vaccine; and Group 6: control group. Two doses were administered in a 26-day interval and the third after 357 days from primo vaccination. Cattle vaccinated with the vaccines formulated with iBoHV-5 plus rgD5 showed a significant (p < 0.01) five-fold increase in total immunoglobulin G (IgG) for BoHV-5, BoHV-1, and rgD5 as compared with the commercial and control groups. Also, a significant (p < 0.05) increase in IgG1 and IgG2a levels was induced in serum for rgD5. In addition, these same vaccines showed significant (p < 0.01) four-fold higher titers of BoHV-1 and -5 neutralizing antibodies. The results demonstrated that the rgD5 conserved important epitopes that were able to stimulate bovine humoral immunity response capable of viral neutralization of BoHV-1 and -5, suggesting it as a promising vaccine antigen to be used in vaccine for BoHV-1 and -5 endemic areas.

Bacillus toyonensis improves immune response in the mice vaccinated with recombinant antigen of bovine herpesvirus type 5

Probiotics modulate the immune response and can increase the effectiveness of vaccines. Bacillus toyonensis is widely used as a probiotic in animal feed. The aim of this study was to assess the effects of B. toyonensis administration on the immune response to an experimental recombinant vaccine against bovine herpesvirus type 5 (BoHV-5) in mice. Mice were vaccinated with BoHV-5 recombinant glycoprotein D and supplemented with the probiotic B. toyonensis in two regimes: one group received the probiotic only during seven days prior to the initial vaccination while the second group was given the probiotic throughout the experimental period of seven weeks. Animals supplemented with probiotic B. toyonensis in two regimes showed an increase in total immunoglobulin (Ig)G, IgG1 and IgG2a levels in serum, in addition to higher titres of antibodies capable of neutralising the BoHV-5 virus than non-supplemented animals (P<0.05). Splenocytes from the supplemented mice had higher mRNA transcription levels of cytokines interleukin (IL)-4 and IL-12. These results show that the use of this probiotic may significantly contribute to the response elicited by recombinant vaccines, especially those that rely on increasing antibody and cell-mediated immune responses for efficacy. Further, the data support an immunomodulatory effect for probiotic B. toyonensis and imply that enhance effect on the immune response against a BoHV-5 recombinant vaccine in mice.

Bovine herpesviruses induce different cell death forms in neuronal and glial-derived tumor cell cultures

Oncolytic viruses have the ability to infect tumor cells and leave healthy cells intact. In this study, bovine herpesvirus 1 (BHV1; Los Angeles, Cooper, and SV56/90 strains) and bovine herpesvirus 5 (BHV5; SV507/99 and GU9457818 strains) were used to infect two neuronal tumor cell lineages: neuro2a (mouse neuroblastoma cells) and C6 (rat glial cells). BHV1 and BHV5 strains infected both cell lines and positively correlated with viral antigen detection (p < 0.005). When neuro2a cells were infected by Los Angeles, SV507/99, and GU9457818 strains, 40 % of infected cells were under early apoptosis and necroptosis pathways. Infected C6 cells were >40 % in necroptosis phase when infected by BHV5 (GU9457818 strain). Blocking caspase activation did not interfere with cell death. However, when necroptosis was blocked, 60-80 % of both infected cells with either virus switched to early apoptosis pathway with no interference with virus replication. Moreover, reactive oxygen species production and mitochondrial membrane dysfunction were detected at high levels in both infected cell lines. In spite of apoptosis and necroptosis blockage, tumor necrosis factor alpha (TNFA) and virus transcription were positively correlated for all viral strains studied. Thus, these results contribute to the characterization of BHV1 and BHV5 as potential oncolytic viruses for non-human cells. Nonetheless, the mechanisms underlying their oncolytic activity in human cells are still to be determined.

Comparison between DNA Detection in Trigeminal Nerve Ganglia and Serology to Detect Cattle Infected with Bovine Herpesviruses Types 1 and 5

Bovine herpesviruses (BoHVs) types 1 (BoHV-1) and 5 (BoHV-5) are alphaherpesviruses of major importance to the bovine production chain. Such viruses are capable of establishing latent infections in neuronal tissues. Infected animals tend to develop a serological response to infection; however, such response—usually investigated by antibody assays in serum—may eventually not be detected in laboratory assays. Nevertheless, serological tests such as virus neutralization (VN) and various enzyme-linked immunosorbent assays (ELISAs) are widely employed to check individual or herd status of BoHV infections. The correlation between detection of antibodies and the presence of viral nucleic acids as indicatives of infection in infected cattle has not been deeply examined. In order to investigate such correlation, 248 bovine serum samples were tested by VN to BoHV-1 and BoHV-5, as well as in a widely employed (though not type-differential) gB ELISA (IDEXX IBR gB X2 Ab Test) in search for antibodies to BoHVs. Immediately after blood withdrawal, cattle were slaughtered and trigeminal ganglia (TG) excised for DNA extraction and viral nucleic acid detection (NAD) by nested PCR. Neutralizing antibodies to BoHV-1 and/or BoHV-5 were detected in 44.8% (111/248) of sera, whereas the gB ELISA detected antibodies in 51.2% (127/248) of the samples. However, genomes of either BoHV-1, BoHV-5, or both, were detected in TGs of 85.9% (213/248) of the animals. These findings reveal that the assays designed to detect antibodies to BoHV-1 and/or BoHV-5 employed here may fail to detect a significant number of latently infected animals (in this study, 35.7%). From such data, it is clear that antibody assays are poorly correlated with detection of viral genomes in BoHV-1 and BoHV-5-infected animals.

Development of an Indirect ELISA for Serological Diagnosis of Bovine herpesvirus 5

Bovine herpesviruses 1 and 5 (BoHV-1 and BoHV-5) are economically important pathogens, associated with a variety of clinical syndromes, including respiratory and genital disease, reproductive failure and meningoencephalitis. The standard serological assay to diagnose BoHV-1 and BoHV-5 infections is the virus neutralization test (VNT), a time consuming procedure that requires manipulation of infectious virus. In the present study a highly sensitive and specific single dilution indirect ELISA was developed using recombinant glycoprotein D from BoHV-5 as antigen (rgD5ELISA). Bovine serum samples (n = 450) were screened by VNT against BoHV-5a and by rgD5ELISA. Compared with the VNT, the rgD5ELISA demonstrated accuracy of 99.8%, with 100% sensitivity, 96.7% specificity and coefficient of agreement between the tests of 0.954. The rgD5ELISA described here shows excellent agreement with the VNT and is shown to be a simple, convenient, specific and highly sensitive virus-free assay for detection of serum antibodies to BoHV-5.

Sequence analysis of the 5' third of glycoprotein C gene of South American bovine herpesviruses 1 and 5

Bovine herpesviruses 1 (BoHV-1) and 5 (BoHV-5) share high genetic and antigenic similarities, but exhibit marked differences in tissue tropism and neurovirulence. The amino-terminal region of glycoprotein C (gC), which is markedly different in each of the viruses, is involved in virus binding to cellular receptors and in interactions with the immune system. This study investigated the genetic and antigenic differences of the 5′ region of the gC (5′ gC) gene (amino-terminal) of South American BoHV-1 (n=19) and BoHV-5 (n=25) isolates. Sequence alignments of 374 nucleotides (104 amino acids) revealed mean similarity levels of 97.3 and 94.2% among BoHV-1 gC (gC1), respectively, 96.8 and 95.6% among BoHV-5 gC (gC5), and 62 and 53.3% between gC1 and gC5. Differences included the absence of 40 amino acid residues (27 encompassing predicted linear epitopes) scattered throughout 5′ gC1 compared to 5′ gC5. Virus neutralizing assays testing BoHV-1 and BoHV-5 antisera against each isolate revealed a high degree of cross-neutralization between the viruses, yet some isolates were neutralized at very low titers by heterologous sera, and a few BoHV-5 isolates reacted weakly with either sera. The virus neutralization differences observed within the same viral species, and more pronounced between BoHV-1 and BoHV-5, likely reflect sequence differences in neutralizing epitopes. These results demonstrate that the 5′ gC region is well conserved within each viral species but is divergent between BoHV-1 and BoHV-5, likely contributing to their biological and antigenic differences.

Immune responses of mice against recombinant bovine herpesvirus 5 glycoprotein D

Glycoprotein D (gD) is essential for attachment and penetration of Bovine herpesvirus 5 (BoHV-5) into permissive cells, and is a major target of the host immune system, inducing strong humoral and cellular immune responses. The aim of this study was to evaluate in mice the immunogenicity of recombinant BoHV-5 gD (rgD5) expressed in Pichia pastoris. Vaccines formulated with rgD5 alone or adjuvanted with Montanide 50 ISA V2; Emulsigen or Emulsigen-DDA was administered intramuscularly or subcutaneously. Almost all formulations stimulated a humoral immune response after the first inoculation. The only exception was observed when the rgD5 was administered subcutaneously without adjuvant, in this case, the antibodies were observed after three doses. Higher titers of neutralizing antibodies were obtained with the three oil-based adjuvant formulations when compared to non-adjuvanted vaccine formulations. The rgD5 vaccine stimulated high mRNA expression levels of Th1 (INF-γ) and pro-inflammatory cytokines (IL-17, GM-CSF). The results demonstrated that the recombinant gD from BoHV-5 conserved important epitopes for viral neutralization from native BoHV-5 gD and was able to elicit mixed Th1/Th2 immune response in mice.

Validation of a reference control for an SYBR-Green fluorescence assay-based real-time PCR for detection of bovine herpesvirus 5 in experimentally exposed bovine embryos

The objective of this study was to optimize an internal control to improve SYBR-Green-based qPCR to amplify/detect the BoHV-5 US9 gene in bovine embryos produced in vitro and experimentally exposed to the virus. We designed an SYBR-Green-based binding assay that is quick to perform, reliable, easily optimized and compares well with the published assay. Herein we demonstrated its general applicability to detect BoHV-5 US9 gene in bovine embryos produced in vitro experimentally exposed to BoHV-5. In order to validate the assay, three different reference genes were tested; and the histone 2a gene was shown to be the most adequate for normalizing the qPCR reaction, by considering melting and standard curves (p < 0.05). On the other hand, no differences were found in the development of bovine embryos in vitro whether they were exposed to BoHV-5 reference and field strains comparing to unexposed embryos. The developed qPCR assay may have important field applications as it provides an accurate BoHV-5 US9 gene detection using a proven reference gene and is considerably less expensive than the TaqMan qPCR currently employed in sanitary programs.

Evaluation of developmental changes in bovine in vitro produced embryos following exposure to bovine Herpesvirus type 5

BACKGROUND

Bovine Herpesvirus type-5 (BoHV-5) is a neurovirulent α-Herpesvirus which is potentially pathogenic for cows and suspected to be associated with reproductive disorders. Interestingly, natural transmission of BoHV-5 by contaminated semen was recently described in Australia. Additionally, BoHV-5 was also isolated from the semen of a healthy bull in the same country and incriminated in a natural outbreak of reproductive disease after artificial insemination. In contrast with BoHV-1, experimental exposure of in vitro produced bovine embryos to BoHV-5 does not affect embryo viability and seems to inhibit some pathways of apoptosis. However, the mechanisms responsible for these phenomena are poorly understood. In this study, we examined mitochondrial activity, antioxidant protection, stress response and developmental rates of in vitro produced bovine embryos that were exposed and unexposed to BoHV-5.

METHODS

For this purpose, bovine embryos produced in vitro were assayed for cell markers after experimental infection of oocytes (n = 30; five repetitions), in vitro fertilization and development. The indirect immunofluorescence was employed to measure the expression of superoxide dismutase 1 (SOD1), anti-oxidant like protein 1 (AOP-1), heat shock protein 70.1 (Hsp 70.1) and also viral antigens in embryos derived from BoHV-5 exposed and unexposed oocytes. The determination of gene transcripts of mitochondrial activity (SOD1), antioxidant protection (AOP-1) and stress response (Hsp70.1) were evaluated using the reverse transcriptase polymerase chain reaction (RT-PCR). MitoTracker Green FM, JC-1 and Hoechst 33342-staining were used to evaluate mitochondrial distribution, segregation patterns and embryos morphology. The intensity of labeling was graded semi-quantitatively and embryos considered intensively marked were used for statistical analysis.

RESULTS

The quality of the produced embryos was not affected by exposure to BoHV-5. Of the 357 collected oocytes, 313 (+/- 6.5; 87.7%) were cleaved and 195 (+/- 3.2; 54.6%) blastocysts were produced without virus exposure. After exposure, 388 oocytes were cleaved into 328 (+/- 8.9, 84.5%), and these embryos produced 193 (+/- 3.2, 49.7%) blastocysts. Viral DNA corresponding to the US9 gene was only detected in embryos at day 7 after in vitro culture, and confirmed by indirect immunofluorescence assay (IFA). These results revealed significant differences (p < 0.05) between exposed and unexposed oocytes fertilized, as MitoTracker Green FM staining Fluorescence intensity of Jc-1 staining was significantly higher (p < 0.005) among exposed embryos (143 +/- 8.2). There was no significant difference between the ratios of Hoechst 33342-stained nuclei and total cells in good-quality blastocysts (in both the exposed and unexposed groups). Using IFA and reverse transcriptase polymerase chain reaction (RT-PCR) for the set of target transcripts (SOD1, AOP-1 and Hsp 70.1), there were differences in the mRNA and respective proteins between the control and exposed embryos. Only the exposed embryos produced anti-oxidant protein-like 1 (AOP-1). However, neither the control nor the exposed embryos produced the heat shock protein Hsp 70.1. Interestingly, both the control and the exposed embryos produced superoxide dismutase (SOD1), revealing intense mitochondrial activity.

CONCLUSION

This is the first demonstration of SOD1 and AOP-1 production in bovine embryos exposed to BoHV-5. Intense mitochondrial activity was also observed during infection, and this occurred without interfering with the quality or number of produced embryos. These findings further our understanding on the ability of α-Herpesviruses to prevent apoptosis by modulating mitochondrial pathways.

Bull semen variables after experimental exposure with Bovine Herpesvirus type 5

The influence of Bovine Herpesvirus type 5 (BoHV-5) infection on semen variables and sperm morphology collected from healthy bulls with no reproductive disorder was evaluated in ten ejaculates distributed into two experimental groups: group I, bull semen exposed to 10(2.3) (tissue culture infectious dose) TCID(50)/50 μl of a Brazilian strain of BoHV-5 (US9/BR/2007; GU9457818) and group II, unexposed bull control semen. After experimental infection, the semen was frozen-thawed prior to computerized analysis (CASA) of sperm motility and movement. Also analyzed were sperm phosphatidylserine transposition, acrosomal integrity, mitochondrial function, plasma membrane integrity and Annexin V expression. Viable BoHV-5 particles and their DNA were detected in infected semen after virus isolation and in situ hybridization (ISH) assay. The ISH revealed the BoHV-5 US9 gene in the acrosome and tail of infected spermatozoa. The only remarkable differences between groups I and II were the sperm kinetic variables, whereby infected sperm had a lesser mean velocity (VAP) and curvilinear velocity (VCL) values as compared to controls (P≤0.05). However, the straightness coefficient (STR) and beat cross frequency (BCF) values were higher in infected sperm. These results indicate that BoHV-5 can be found in infected sperm but induces no functional and morphological damage even after freeze-thawing, and, importantly, BoHV-5 can be spread via in vitro and in vivo reproductive biotechnology procedures.

Efficacy of an inactivated, recombinant bovine herpesvirus type 5 (BoHV-5) vaccine

Bovine herpesvirus type 5 (BoHV-5) is the causative agent of bovine herpetic encephalitis. In countries where BoHV-5 is prevalent, attempts to vaccinate cattle to prevent clinical signs from BoHV-5-induced disease have relied essentially on vaccination with BoHV-1 vaccines. However, such practice has been shown not to confer full protection to BoHV-5 challenge. In the present study, an inactivated, oil adjuvanted vaccine prepared with a recombinant BoHV-5 from which the genes coding for glycoprotein I (gI), glycoprotein E (gE) and membrane protein US9 were deleted (BoHV-5 gI/gE/US9(-)), was evaluated in cattle in a vaccination/challenge experiment. The vaccine was prepared from a virus suspension containing a pre-inactivation antigenic mass equivalent to 10(7.69) TCID(50)/dose. Three mL of the inactivated vaccine were administered subcutaneously to eight calves serologically negative for BoHV-5 (vaccinated group). Four other calves were mock-vaccinated with an equivalent preparation without viral antigens (control group). Both groups were boostered 28 days later. Neither clinical signs of disease nor adverse effects were observed during or after vaccination. A specific serological response, revealed by the development of neutralizing antibodies, was detected in all vaccinated animals after the first dose of vaccine, whereas control animals remained seronegative. Calves were subsequently challenged on day 77 post-vaccination (pv) with 10(9.25) TCID(50) of the wild-type BoHV-5 (parental strain EVI 88/95). After challenge, vaccinated cattle displayed mild signs of respiratory disease, whereas the control group developed respiratory disease and severe encephalitis, which led to culling of 2/4 calves. Searches for viral DNA in the central nervous system (CNS) of vaccinated calves indicated that wild-type BoHV-5 did not replicate, whereas in CNS tissues of calves on the control group, viral DNA was widely distributed. BoHV-5 shedding in nasal secretions was significantly lower in vaccinated calves than in the control group on days 2, 3, 4 and 6 post-challenge (pc). In addition, the duration of virus shedding was significantly shorter in the vaccinated (7 days) than in controls (12 days). Attempts to reactivate latent infection by administration of dexamethasone at 147 days pv led to recrudescence of mild signs of respiratory disease in both vaccinated and control groups. Infectious virus shedding in nasal secretions was detected at reactivation and was significantly lower in vaccinated cattle than in controls on days 11-13 post-reactivation (pr). It is concluded that the inactivated vaccine prepared with the BoHV-5 gI/gE/US9(-) recombinant was capable of conferring protection to encephalitis when vaccinated cattle were challenged with a large infectious dose of the parental wild type BoHV-5. However, it did not avoid the establishment of latency nor impeded dexamethasone-induced reactivation of the virus, despite a significant reduction in virus shedding after challenge and at reactivation on vaccinated calves.

Development and statistical validation of a guinea pig model for vaccine potency testing against Infectious Bovine Rhinothracheitis (IBR) virus

Infectious Bovine Rhinothracheitis (IBR) caused by bovine herpesvirus 1 (BoHV-1) infection is distributed worldwide. BoHV-1 either alone or in association with other respiratory cattle pathogens causes significant economic losses to the livestock industry. The aim of this work was to validate a guinea pig model as an alternative method to the current BoHV-1 vaccine potency testing in calves. Guinea pigs were immunized with two doses of vaccine, 21 days apart and sampled at 30 days post vaccination (dpv). BoHV-1 antibody (Ab) response to vaccination in guinea pigs, measured by ELISA and virus neutralization (VN), was statistically compared to the Ab response in cattle. The guinea pig model showed a dose-response relationship to the BoVH-1 antigen concentration in the vaccine and it was able to discriminate among vaccines containing 1log(10) difference in its BoHV-1 concentration with very good repeatability and reproducibility (CV < or = 20%). A regression analysis of the Ab titers obtained in guinea pigs and bovines at 30 and 60dpv, respectively, allowed us to classify vaccines in three potency categories: "very satisfactory", "satisfactory" and "unsatisfactory". Bovines immunized with vaccines corresponding to each of these three categories were experimentally challenged with BoVH-1 virus, the level of protection, as measured by reduction of virus shedding and disease severity, correlated well with the vaccine category used. Data generated by 85 experiments, which included vaccination of calves and guinea pigs with 18 reference vaccines of known potency, 8 placebos and 18 commercial vaccines, was subjected to statistical analysis. Concordance analysis indicated almost perfect agreement between the model and the target species for Ab titers measured by ELISA and almost perfect to substantial agreement when Ab titers were measured by VN. Taken together these results indicate that the developed guinea pig model represents a novel and reliable tool to estimate batch-to-batch vaccine potency and to predict efficacy of killed BoHV-1 veterinary vaccines.