Bovine herpesvirus 1 (BHV-1): biology, pathogenesis, and control

53BP1, a known chromatin-associated factor that promotes DNA damage repair, is differentially modulated during bovine herpesvirus 1 infection in vitro and in vivo

Bovine herpesvirus 1 (BoHV-1) productive infection induces the formation of DNA double-strand breaks (DSBs), the most severe form of DNA lesions in cultured cells. 53BP1, a chromatin-associated factor, plays an essential role in DNA damage repair. In this study, we demonstrated that BoHV-1 productive infection in bovine kidney (MDBK) cells increased the expression of phosphorylated form of H2AX protein (γH2AX) and promoted the formation of γH2AX foci in the nucleus, indicative of enhanced DNA lesions. However, despite the elevated total 53BP1 protein levels, its recruitment to the nucleus and formation of 53BP1 foci was impaired, suggesting the disruption of 53BP1-mediated DNA damage repair (DDR). Furthermore, immunohistochemistry (IHC) studies showed that γH2AX was readily detected in trigeminal ganglia (TG) neurons of New Zealand White rabbits during both acute infection (day 3) and dexamethasone (DEX)-stimulated reactivation from latency, indicating the occurrence of DNA damage in vivo. This was consistent with the substantial reduction of 53BP1 protein expression in these tissues. Interestingly, 53BP1 was detected in a subset of TG neurons from both mock-infected and latently infected rabbits, but the localization profile of 53BP1 looks largely different, suggesting that 53BP1 may play a role in viral latency. Taken together, our findings demonstrated that BoHV-1 lytic infection impaired 53BP1-dependent DNA damage repair through differing mechanisms in vitro and in vivo, potentially promoting the accumulation of DNA damage. Moreover, virus latency altered the 53BP1 localization, underscoring the importance of 53BP1 signaling in the virus pathogenicity.

Luteolin inhibits BHV-1 replication and alleviates virus-induced inflammatory responses by regulating PI3K/AKT pathway

Bovine herpesvirus type 1 (BHV-1) seriously affects the production safety of the cattle industry and leads to epidemics worldwide. Luteolin (Lut), a flavonoid substance, can be found in vegetables, fruits, and herbs and possesses various biological properties. Here, we found that Lut can dose-dependently and significantly inhibit the cytopathic effects of BHV-1, decrease the viral titer, and suppress the BHV-1 gB gene and VP8 protein levels on bovine nasal turbinate osteoblasts (BT) and bovine kidney epithelial cells (MDBK). Mechanistic studies revealed that Lut can stably bind to the active sites of PI3K and AKT, and inhibit the PI3K/AKT pathway. Interestingly, 740Y-P (an agonist of the PI3K/AKT pathway) significantly attenuated the anti-BHV-1 effects of Lut. Further studies on the anti-inflammatory effects of Lut revealed that it attenuated BHV-1-induced activation of the NFκB pathway, which significantly suppressed the expression of TNF-α, IL-1β, IL-6, and IL-8 and increased the expression levels of IL-4 and IL-10. The PI3K/AKT pathway was also found to be involved in the anti-inflammatory effects of Lut. These results confirm the inhibitory effect of Lut on BHV-1 replication, which lays the foundation for further studies on the prevention and control of BHV-1.

Bovine Transcription Factor POU Class 2 Homeobox 1 (POU2F1/Oct1) Protein Promotes BoHV-1 Replication in MDBK Cells

Bovine herpesvirus type 1 (BoHV-1) causes severe diseases in bovine species and great economic burden to the cattle industry worldwide. Due to its complex life cycle, many host factors that affect BoHV-1 replication remain to be explored. To understand the possible roles that the Oct1 cellular protein could play in this process, we first created Oct1-deficient MDBK cells using CRISPR/Cas9-mediated genome editing. Upon infection, the absence of Oct1 in MDBK cells significantly impacted BoHV-1 replication, a phenotype rescued by over-expressing the wild-type Oct1 protein in the deficient cells. We further found that the expression of all three classes of temporal genes, including essential and non-essential viral genes, were significantly reduced in Oct1 knockout MDBK cells, following both high and low multiplicity of infection. In summary, our findings confirm that the bovine Oct1 protein acts as a pro-viral factor for BoHV-1 replication by promoting its viral gene transcription in MDBK cells.

Isolation of the Initial Bovine Alphaherpesvirus 1 Isolate from Yanbian, China

Bovine infectious rhinotracheitis (IBR), caused by bovine alphaherpesvirus 1 (BoAHV1), poses significant challenges to the global cattle industry due to its high contagiousness and economic impact. In our study, we successfully isolated a BoAHV1 strain from suspected infected bovine nasal mucus samples in Yanji city, revealing genetic similarities with strains from Sichuan, Egypt, and the USA, while strains from Xinjiang, Beijing, Hebei, and Inner Mongolia showed more distant associations, indicating potential cross-border transmission. Additionally, our investigation of BoAHV1 infection dynamics within host cells revealed early upregulation of gB, which is critical for sustained infection, while the expression of gC and gD showed variations compared to previous studies. These findings enhance our understanding of BoAHV1 diversity and infection kinetics, underscoring the importance of international collaboration for effective surveillance and control strategies. Furthermore, they lay the groundwork for the development of targeted therapeutics and vaccines to mitigate the impact of IBR on the cattle industry.

The biology and development of vaccines for bovine alphaherpesvirus 1

Bovine alphaherpesvirus type 1 (BoAHV-1) infections lead to compromised herd health and significantly reduced productivity of affected cattle. While BoAHV-1 may cause rhinotracheitis, conjunctivitis, genital infections, and abortions, respiratory tract infections constitute the predominant clinical disease. Immune suppression induced by BoAHV-1 may contribute to co-infections initiating the bovine respiratory disease complex. In this review, the emphasis is to recapitulate the biology and the vaccine technologies currently in use and in development for BoAHV-1, and to discuss the major limitations. Studies on the life cycle and host interactions of BoAHV-1 have resulted in the identification of virulence factors. While several vaccine types, such as vectored vaccines and subunit vaccines, are under investigation, modified live and inactivated BoAHV-1 vaccines are still most frequently used in most areas of the world, whereas attenuated and inactivated marker vaccines are in use in Europe. The knowledge gained from studies on the biology of BoAHV-1 can form a basis for the rational design of future vaccines.

Ivermectin antiviral activity against Varicellovirus bovinealpha 1: assessment of intracellular drug accumulation in virus-infected cells

Varicellovirus bovinealpha 1 (formerly bovine alphaherpesvirus type 1, BoAHV-1) is associated with several syndromes in cattle, including respiratory disease and is one of the main agents involved in the bovine respiratory disease complex (BRDC). Its infectious cycle is characterized by latent infections with sporadic virus reactivation and transmission. Although the acute disease can be prevented by the use of vaccines, specific therapeutic measures are not available. Ivermectin (IVM) is a semi-synthetic avermectin with a broad-spectrum antiparasitic activity, which has previously shown to have potential as an antiviral drug. In this study, IVM antiviral activity against BoAHV-1 was characterized in two cell lines (MDBK [Madin Darby bovine kidney] and BT [bovine turbinate]), including the measurement of intracellular drug accumulation within virus-infected cells. IVM antiviral activity was assessed at three different drug concentrations (1.25, 2.5 and 5 µM) after incubation for 24, 48 and 72 h. Slight cytotoxicity was only observed with 5 µM IVM. Even the lowest IVM dose was able to induce a significant reduction in virus titers in both cell lines. These findings indicate that the antiviral effects of IVM were evident in our experimental model within the range of concentrations achievable through therapeutic in vivo administration. Consequently, additional in vivo trials are necessary to validate the potential utility of these results in effectively managing BoAHV-1 in infected cattle.

Carnitine palmitoyl-transferase 1A is potentially involved in bovine herpesvirus 1 productive infection

Bovine herpesvirus 1(BoHV-1) is an important bovine pathogen that causes great economic loss to cattle farms worldwide. The virus-productive infection in bovine kidney (MDBK) cells results in ATP depletion. The mechanisms are not well understood. Mitochondrial fatty acid β-oxidation (FAO) is an important energy source in many tissues with high energy demand. Since carnitine palmitoyl-transferase 1 A (CPT1A) is the rate-limiting enzyme of FAO, we investigated the interactions between virus-productive infection and CPT1A signaling. Here, we found that virus-productive infection at the later stage significantly decreased CPT1A protein levels in all the detected cells, including MDBK, A549, and Neuro-2A cells, differentially altered the accumulation of CPT1A proteins in the nucleus and cytosol, and re-localized the protein in the nucleus. Etomoxir (ETO), an irreversible inhibitor of CPT1A, inhibited viral replication and partially interfered with the ability of BoHV-1 to alter CPT1A accumulation in the nucleus but not in the cytosol. Furthermore, ETO consistently reduced RNA levels of two viral regulatory proteins (bICP0 and bICP22) and protein expression of virion-associated proteins during productive infection, further supporting the important roles of CPT1A signaling in BoHV-1 productive infection. These data, for the first time, suggest that CPT1A is potentially involved in BoHV-1 productive infection.

An indirect ELISA to detect antibodies to the gC of bovine alphaherpesvirus 1 (BoAHV1) displaying no crossreactivity with antibodies induced by bovine alphaherpesvirus 5 (BoAHV5)

Seroprevalence of bovine alphaherpesvirus type 1 (BoAHV1) infections may be contaminated by crossreactive antibodies to bovine alphaherpesvirus type 5 (BoAHV5). To avoid such crossreactivity, an indirect enzyme-linked immunosorbent assay prepared with a recombinant glycoprotein C (gC) antigen (ELISA-gC1) was developed, aiming the detection of antibodies to BoAHV1, with no crossreactivity with BoAHV5 antibodies. The antigen for the ELISA-gC1 was the product of the expression of 219 bp from the N-terminal portion of the BoAHV1 gC gene, which bears low homology between the two virus types. The test was validated on 131 bovine serum samples, including 26 sera from BoAHV1-experimentally immunized, 38 sera from BoAHV5-experimentally infected or immunized calves, and 67 sera from calves seronegative for both BoAHV1 and BoAHV5, as determined by serum neutralization (SN). When compared to SN for BoAHV1, the ELISA-gC1 presented 100% sensitivity, 95.5 % specificity, 100 % negative predictive value, 89.6 % positive predictive value, 98.8 % precision, and a kappa correlation coefficient (κ) 0.95. None of the 38 BoAHV5-seropositive calves was detected by the ELISA-gC1. The ELISA-gC1 proved highly effective for the identification of BoAHV1-positive sera, with no crossreactivity with anti-BoAHV5 antibodies, thus able to distinguish serological responses from BoAHV1- and BoAHV5-seropositive cattle. Its capacity to detect BoAHV1-specific antibodies should allow the determination of the actual BoAHV1 prevalence in herds, which cannot be serologically determined in countries where BoAHV5 is also prevalent due to antibody crossreactivity. Apart from recognizing exclusively BoAHV1-infected cattle, the ELISA-gC1 may also be used in support of BoAHV5 epidemiological studies by allowing the exclusion of BoAHV1-seropositive animals.

Associating bovine herpesvirus 1 envelope glycoprotein gD with activated phospho-PLC-γ1(S1248)

Phospholipase C gamma 1 (PLC-γ1) may locate at distinct subcellular locations, such as cytosol, plasma membrane, and nucleus for varied biological functions. Bovine herpesvirus 1 (BoHV-1) productive infection activates PLC-γ1 signaling, as demonstrated by increased protein levels of phosphorylated-PLC-γ1 at Ser1248 [p-PLC-γ1(S1248)], which benefits virus productive infection. Here, for the first time, we reported that Golgi apparatus also contains activated p-PLC-γ1(S1248). And BoHV-1 productive infection at later stages (24 hpi) increased the accumulation of p-PLC-γ1(S1248) in the Golgi apparatus, where p-PLC-γ1(S1248) forms highlighted puncta observed via a confocal microscope. Coimmunoprecipitation studies demonstrated that the Golgi p-PLC-γ1(S1248) is specifically associated with the viral protein gD but not gC. In addition, we found that p-PLC-γ1(S1248) is consistently associated with both the plasma membrane-associated virions and the released virions. When the virus-infected cells were treated with PLC-γ1-specific inhibitor, U73122, for a short duration of 4 hours prior to the endpoint of virus infection, we found that the viral protein gD was trapped in the Golgi apparatus, suggesting that the PLC-γ1 signaling may facilitate trafficking of progeny virions out of this organelle. These findings provide a novel insight into the interplay between PLC-γ1 signaling and BoHV-1 replication. IMPORTANCE Bovine herpesvirus 1 (BoHV-1) productive infection increases protein levels of phosphorylated-phospholipase C gamma 1 at Ser1248 [p-PLC-γ1(S1248)]. However, whether it causes any variations to p-PLC-γ1(S1248) localization is not well understood. Here, for the first time, we found that partial p-PLC-γ1(S1248) is residing in the Golgi apparatus, where the accumulation is enhanced by virus infection. p-PLC-γ1(S1248) is consistently associated with virions, partially via binding to gD, in both the Golgi apparatus and cytoplasm membranes. Surprisingly, it also associates with the released virions. Of note, this is the first evidenced BoHV-1 virion-bound host protein. It seems that p-PLC-γ1(S1248) works as an escort during trafficking of progeny virions out of Golgi apparatus to the plasma membranes as well as releasing outside of the cell membranes. Furthermore, we showed that the activated p-PLC-γ1(S1248) is potentially implicated in the transport of virions out of Golgi apparatus, which may represent a novel mechanism to regulate virus productive infection.

NFAT5 Restricts Bovine Herpesvirus 1 Productive Infection in MDBK Cell Cultures

Bovine herpesvirus 1 (BoHV-1), an important bovine viral pathogen, causes severe disease in the upper respiratory tract and reproductive system. Tonicity-responsive enhancer-binding protein (TonEBP), also known as nuclear factor of activated T cells 5 (NFAT5), is a pleiotropic stress protein involved in a range of cellular processes. In this study, we showed that the knockdown of NFAT5 by siRNA increased BoHV-1 productive infection and overexpression of NFAT5 via plasmid transfection decreased virus production in bovine kidney (MDBK) cells. Virus productive infection at later stages significantly increased transcription of NFAT5 but not appreciably alter measurable NFAT5 protein levels. Virus infection relocalized NFAT5 protein and decreased the cytosol accumulation. Importantly, we found a subset of NFAT5 resides in mitochondria, and virus infection led to the depletion of mitochondrial NFAT5. In addition to full-length NFAT5, another two isoforms with distinct molecular weights were exclusively detected in the nucleus, where the accumulation was differentially affected following virus infection. In addition, virus infection differentially altered mRNA levels of PGK1, SMIT, and BGT-1, the canonical downstream targets regulated by NFAT5. Taken together, NFAT5 is a potential host factor that restricts BoHV-1 productive infection, and virus infection hijacks NFAT5 signaling transduction by relocalization of NFAT5 molecules in cytoplasm, nucleus, and mitochondria, as well as altered expression of its downstream targets. IMPORTANCE Accumulating studies have revealed that NFAT5 regulates disease development due to infection of numerous viruses, underlying the importance of the host factor in virus pathogenesis. Here, we report that NFAT5 has capacity to restrict BoHV-1 productive infection in vitro. And virus productive infection at later stages may alter NFAT5 signaling pathway as observed by relocalization of NFAT5 protein, reduced accumulation of NFAT5 in cytosol, and differential expression of NFAT5 downstream targets. Importantly, for the first time, we found that a subset of NFAT5 resides in mitochondria, implying that NFAT5 may regulate mitochondrial functions, which will extend our knowledge on NFAT5 biological activities. Moreover, we found two NFAT5 isoforms with distinct molecular weights were exclusively detected in the nucleus, where the accumulation was differentially affected following virus infection, representing a novel regulation mechanism on NFAT5 function in response to BoHV-1infection.

Diagnosis of Ruminant Viral Diseases with Loop-Mediated Isothermal Amplification

Infectious diseases in livestock industry are major problems for animal health, food safety, and the economy. Zoonotic diseases from farm animals are significant threat to human population as well. These are notifiable diseases listed by the World Organization for Animal Health (OIE). Rapid diagnostic methods can help keep infectious diseases under control in herds. Loop-mediated isothermal amplification (LAMP) is a simple and rapid nucleic acid amplification method that is studied widely for detection of many infectious diseases in the field. LAMP allows biosensing of target DNA or RNA under isothermal conditions with high specificity in a short period of time. An untrained user can analyze results based on color change or turbidity. Here we review LAMP assays to diagnose OIE notifiable ruminant viral diseases in literature highlighting properties of LAMP method considering what is expected from an efficient, field usable diagnostic test.

Modulation of granzymes mRNA expression in neural tissue of BoAHV-1 and BoAHV-5-infected cattle

Bovine alphaherpesviruses (BoAHV)-1 and 5 are neurotropic viruses of cattle which differ in their neuropathogenic potential. BoAHV-5 is responsible for non-suppurative meningoencephalitis in calves while BoAHV-1 can occasionally cause encephalitis. Granzymes (GZMs) are serine-proteases that participate in CD8⁺ T cells-mediated killing of virally-infected cells upon release through perforin (PFN)-formed pores in the cell membrane. Recently, six GZMs have been identified in cattle (A, B, K, H, M and O). However, their expression in bovine tissues has not been evaluated. In this study, the mRNA expression levels of PFN and GZMs A, B, K, H and M in the nervous system of calves experimentally-inoculated with BoAHV-1 or BoAHV-5 were analyzed at the three distinct stages of the infectious cycle of alphaherpesviruses: acute infection, latency and reactivation. This is the first report describing the expression of GZMs in bovine neural tissue and the first analysis of GZM expression in the context of bovine alphaherpesviruses neuropathogenesis. The findings revealed that PFN and GZM K are upregulated during BoAHV-1 or BoAHV-5 acute infection. In contrast to BoAHV-1, during BoAHV-5 latency a significant up-regulation of PFN, GZM K and GZM H was detected. PFN and GZM A, K and H expression was also up-regulated during BoAHV-5 reactivation. Therefore, a distinct pattern of PFN and GZM expression is evident along the infectious cycle of each alphaherpesvirus and this might contribute to the differences in BoAHV-1 and BoAHV-5 neuropathogenesis.

The Cell-Mediated Immune Response against Bovine alphaherpesvirus 1 (BoHV-1) Infection and Vaccination

Bovine Alphaherpesvirus 1 (BoHV-1) is one of the major respiratory pathogens in cattle worldwide. Infection often leads to a compromised host immune response that contributes to the development of the polymicrobial disease known as “bovine respiratory disease”. After an initial transient phase of immunosuppression, cattle recover from the disease. This is due to the development of both innate and adaptive immune responses. With respect to adaptive immunity, both humoral and cell-mediated immunity are required to control infection. Thus, several BoHV-1 vaccines are designed to trigger both branches of the adaptive immune system. In this review, we summarize the current knowledge on cell-mediated immune responses directed against BoHV-1 infection and vaccination.

Microscopic lesions and modulation of gene expression in cervical medulla during BoAHV-1and BoAHV-5 infection: A mini-review

Bovine herpesvirus (BoAHV) types 1 and 5 are closely-related neurotropic alpha-herpesviruses. BoAHV-1 generally causes respiratory and genital disease but can occasionally cause encephalitis. BoAHV-5 is the causative agent of non suppurative meningoencephalitis in calves. During neuroinvasion, both viruses reach the central and peripheral nervous system. While brain alterations are well-described, the changes that occur in the medulla have not been fully detailed. In this work, we integrated and analyzed the virological findings, the microscopic lesions and the changes that occur in the expression of genes related to the innate immunity, cell cycle and apoptosis in the cervical medulla of calves experimentally-infected with BoAHV-1 and BoAHV-5. This will contribute to the understanding of the differential neuropathogenesis of these alpha-herpesviruses of cattle.

Characterization and expression of domains of Alphaherpesvirus bovine 1/5 envelope glycoproteins B in Komagataella phaffi

BACKGROUND

Bovine herpes virus (BoHV 1 and BoHV-5) are the causative agents of infectious bovine rhinotracheitis (IBR). IBR is responsible for important economic losses in the cattle industry. The envelope glycoprotein B (gB) is essential for BoHV infection of cattle's upper respiratory and genital tract. gB is one of the main candidate antigens for a potential recombinant vaccine since it induces a strong and persistent immune response.

RESULTS

In this study, gB of BoHV-1 and BoHV-5 was characterized in terms of function, structure, and antigenicity through bioinformatics tools. gB showed conserved sequence and structure, so, both domains named PH Like 1 and 2 domains of each virus were selected for the design of a bivalent vaccine candidate. The immunoinformatic study showed that these two domains have epitopes recognizable by B and T lymphocytes, followed by this, the cDNA domains from BoHV-1/5 gB (Domains-gB) were transformed into the yeast Komagataella phaffii GS115 (previously known as Pichia pastoris). A recombinant protein with molecular weight of about 110 kDa was obtained from the culture media. The vaccine candidate protein (Domains-gB) was recognized by a monoclonal antibody from a commercial ELISA kit used for IBR diagnostic, which may suggest that the epitopes are conserved of the entire infectious virus.

CONCLUSION

Overall, it was shown that the recombinant domains of BoHV-1/5 gB have antigenic and immunogenic properties similar to the native gB. This vaccine candidate is promising to be used in future studies to assess its immunogenicity in an animal model.

Phospholipase C-γ1 potentially facilitates subcellular localization of activated β-catenin, p-β-catenin(S552), during bovine herpesvirus 1 productive infection in MDBK cells

Bovine herpesvirus 1 (BoHV-1) is a significant risk factor for the bovine respiratory disease complex (BRDC), a severe disease causing great economic losses to the cattle industry worldwide. Previous studies have reported that both phospholipase C-γ1 (PLC-γ1) and β-catenin are activated during BoHV-1 infection for efficient replication. However, the interplay between PLC-γ1 and β-catenin as a consequence of virus infection remains to be elucidated. Here, we reported that PLC-γ1 interacted with β-catenin, which was enhanced following virus infection. PLC-γ1-specific inhibitor, U73122, significantly reduced the mRNA levels of β-catenin in BoHV-1-infected cells; however, the steady-state protein levels were not affected due to the virus infection. Interestingly, the treatment of virus-infected cells with U73122 reduced the accumulation of activated β-catenin [p-β-catenin(S552)] in fractions of the cytoplasmic membrane as that observed with the treatment of methyl-β-cyclodextrin (MβCD), which can disrupt cytoplasmic membrane structure via sequestering cholesterol. Nucleus accumulation of p-β-catenin(S552) was increased following U73122 treatment in virus-infected cells. In addition, the association of p-β-catenin(S552) with cytoplasmic membrane induced by the virus infection was significantly disrupted by the treatment of U73122 and MβCD. These data indicated that the PLC-γ1 signaling is potentially involved in the regulation of β-catenin signaling stimulated by BoHV-1 infection partially via affecting the subcellular localization of p-β-catenin(S552).

Stress Triggers Expression of Bovine Herpesvirus 1 Infected Cell Protein 4 (bICP4) RNA during Early Stages of Reactivation from Latency in Pharyngeal Tonsil

Bovine herpesvirus 1 (BoHV-1), an important pathogen of cattle, establishes lifelong latency in sensory neurons within trigeminal ganglia (TG) after acute infection. The BoHV-1 latency-reactivation cycle, like other alphaherpesvirinae subfamily members, is essential for viral persistence and transmission. Notably, cells within pharyngeal tonsil (PT) also support a quiescent or latent BoHV-1 infection. The synthetic corticosteroid dexamethasone, which mimics the effects of stress, consistently induces BoHV-1 reactivation from latency allowing early stages of viral reactivation to be examined in the natural host. Based on previous studies, we hypothesized that stress-induced cellular factors trigger expression of key viral transcriptional regulatory genes. To explore this hypothesis, RNA-sequencing studies compared viral gene expression in PT during early stages of dexamethasone-induced reactivation from latency. Strikingly, RNA encoding infected cell protein 4 (bICP4), which is translated into an essential viral transcriptional regulatory protein, was detected 30 min after dexamethasone treatment. Ninety minutes after dexamethasone treatment bICP4 and, to a lesser extent, bICP0 RNA were detected in PT. All lytic cycle viral transcripts were detected within 3 h after dexamethasone treatment. Surprisingly, the latency related (LR) gene, the only viral gene abundantly expressed in latently infected TG neurons, was not detected in PT during latency. In TG neurons, bICP0 and the viral tegument protein VP16 are expressed before bICP4 during reactivation, suggesting distinct viral regulatory genes mediate reactivation from latency in PT versus TG neurons. Finally, these studies confirm PT is a biologically relevant site for BoHV-1 latency, reactivation from latency, and virus transmission. IMPORTANCE BoHV-1, a neurotropic herpesvirus, establishes, maintains, and reactivates from latency in neurons. BoHV-1 DNA is also detected in pharyngeal tonsil (PT) from latently infected calves. RNA-sequencing studies revealed the viral infected cell protein 4 (bICP4) RNA was expressed in PT of latently infected calves within 30 min after dexamethasone was used to initiate reactivation. As expected, bICP4 RNA was not detected during latency. All lytic cycle viral genes were expressed within 3 h after dexamethasone treatment. Conversely, bICP0 and the viral tegument protein VP16 are expressed prior to bICP4 in trigeminal ganglionic neurons during reactivation. The viral latency related gene, which is abundantly expressed in latently infected neurons, was not abundantly expressed in PT during latency. These studies provide new evidence PT is a biologically relevant site for BoHV-1 latency and reactivation. Finally, we predict other alphaherpesvirinae subfamily members utilize PT as a site for latency and reactivation.

Subunit vaccine based on glycoprotein B protects pattern animal guinea pigs from tissue damage caused by infectious bovine rhinotracheitis virus

Infectious bovine rhinotracheitis (IBR) is caused by Bovine herpesvirus type 1 (BoHV-1), which seriously threatens the global cattle industry. Only vaccination to improve immunity is the most direct and effective means to prevent IBR. Attempts are being made to use subunit vaccines, deleted or recombinant viral vaccines to reduce or eradicate IBR. For investigating the immunological characteristics of glycoprotein B subunit vaccine in pattern animal guinea pigs, the partial glycoprotein B (gB) of BoHV-1 with dominant antigenic characteristic was selected. A recombinant prokaryotic expression vector pET-32a-gB with the truncated gB gene was constructed, expressed, identified and the purified proteins were used to immunize guinea pigs. The immune effect of the subunit vaccine was assessed by monitoring clinical symptoms, viral load, antibody secretion, and histopathological changes. The results indicated that guinea pigs immunized with the gB subunit vaccine produced high levels of anti-gB antibodies and virus-neutralizing antibodies. The gB subunit vaccine significantly reduced viral shedding and lung tissue damage after IBRV challenge. The animals inoculated the gB subunit vaccine also had less virus reactivation. Its protective effect on viral shedding and tissue damage was similar to that of inactivated BoHV-1 vaccine. This work is a proof-of-concept study of subunit vaccine-induced protection against BoHV-1. And it is expected to be a candidate vaccine for the prevention of IBR.

DNA Damage Response Differentially Affects BoHV-1 Gene Transcription in Cell Type-Dependent Manners

Bovine herpesvirus 1 (BoHV-1), an important pathogen of cattle, is also a promising oncolytic virus. Recent studies have demonstrated that the virus infection induces DNA damage and DNA damage response (DDR), potentially accounting for virus infection-induced cell death and oncolytic effects. However, whether the global DDR network affects BoHV-1 productive infection remains to be elucidated. In this study, we show that global DDR induced by ultraviolet (UV) irradiation prior to BoHV-1 infection differentially affected transcription of immediate early (IE) genes, such as infected cell protein 0 (bICP0) and bICP22, in a cell-type-dependent manner. In addition, UV-induced DDR may affect the stabilization of viral protein levels, such as glycoprotein C (gC) and gD, because the variation in mRNA levels of gC and gD as a consequence of UV treatment were not in line with the variation in individual protein levels. The virus productive infection also affects UV-primed DDR signaling, as demonstrated by the alteration of phosphorylated histone H2AX (γH2AX) protein levels and γH2AX formation following virus infection. Taken together, for the first time, we evidenced the interplay between UV-primed global DDR and BoHV-1 productive infection. UV-primed global DDR differentially modulates the transcription of virus genes and stabilization of virus protein. Vice versa, the virus infection may affect UV-primed DDR signaling.

Understanding the mechanisms of viral and bacterial coinfections in bovine respiratory disease: a comprehensive literature review of experimental evidence

Bovine respiratory disease (BRD) is one of the most important diseases impacting the global cattle industry, resulting in significant economic loss. Commonly referred to as shipping fever, BRD is especially concerning for young calves during transport when they are most susceptible to developing disease. Despite years of extensive study, managing BRD remains challenging as its aetiology involves complex interactions between pathogens, environmental and host factors. While at the beginning of the twentieth century, scientists believed that BRD was only caused by bacterial infections ("bovine pasteurellosis"), we now know that viruses play a key role in BRD induction. Mixtures of pathogenic bacteria and viruses are frequently isolated from respiratory secretions of animals with respiratory illness. The increased diagnostic screening data has changed our understanding of pathogens contributing to BRD development. In this review, we aim to comprehensively examine experimental evidence from all existing studies performed to understand coinfections between respiratory pathogens in cattle. Despite the fact that pneumonia has not always been successfully reproduced by in vivo calf modelling, several studies attempted to investigate the clinical significance of interactions between different pathogens. The most studied model of pneumonia induction has been reproduced by a primary viral infection followed by a secondary bacterial superinfection, with strong evidence suggesting this could potentially be one of the most common scenarios during BRD onset. Different in vitro studies indicated that viral priming may increase bacterial adherence and colonization of the respiratory tract, suggesting a possible mechanism underpinning bronchopneumonia onset in cattle. In addition, a few in vivo studies on viral coinfections and bacterial coinfections demonstrated that a primary viral infection could also increase the pathogenicity of a secondary viral infection and, similarly, dual infections with two bacterial pathogens could increase the severity of BRD lesions. Therefore, different scenarios of pathogen dynamics could be hypothesized for BRD onset which are not limited to a primary viral infection followed by a secondary bacterial superinfection.

β-catenin has potential effects on the expression, subcellular localization, and release of high mobility group box 1 during bovine herpesvirus 1 productive infection in MDBK cell culture

High mobility group box 1 (HMGB1), a ubiquitous DNA-binding protein, can be released into extracellular space and function as a strong proinflammatory cytokine, which plays critical roles in the pathogenesis of various inflammatory diseases. Here, we showed that BoHV-1 productive infection in MDBK cells at later stage significantly increases HMGB1 mRNA expression and the protein release, but decreases the steady-state protein levels. Virus infection increases accumulation of HMGB1 protein in both nucleus and mitochondria, and relocalizes nuclear HMGB1 to assemble in highlighted foci via a confocal microscope assay. Interestingly, β-catenin-specific inhibitor iCRT14 is able to increase HMGB1 transcription and the protein release, and subcellular translocation in virus-infected cells. HMGB1-specific inhibitor, glycyrrhizin, could differentially affect virus gene transcription such as, the viral regulatory protein bICP0, bICP4 and bICP22, as well as glycoprotein gD. In summary, our data provides a novel mechanism that β-catenin signaling may regulate inflammatory response via affecting HMGB1 signaling.

An Improved DNA Vaccine Against Bovine Herpesvirus-1 Using CD40L and a Chemical Adjuvant Induces Specific Cytotoxicity in Mice

Bovine herpesvirus-1 (BoHV-1) uses many mechanisms to elude the immune system; one of them is spreading intracellularly, even in the presence of specific antiviral antibodies. Cytotoxic T lymphocytes (CTLs) are necessary to eliminate the virus. The main preventive strategy is vaccination based on inactivated virus. These vaccines are poor inducers of cellular immune responses, and complicate serological diagnosis and determination of the real prevalence of infection. DNA vaccines are a good option because of the capacity of Differentiating Infected from Vaccinated Animals-(DIVA vaccine)-and may be the best way to induce cytotoxic responses. Although this type of vaccines leads to only weak "in vivo" expression and poor immune responses, incorporation of molecular and/or chemical adjuvants can improve the latter, both in magnitude and in direction. In this study, we have investigated the specific immune responses elicited in mice by DNA vaccines based on the BoHV-1 glycoprotein D (pCIgD) with and without two different adjuvants: a plasmid encoding for murine CD40L (pCD40L) or Montanide™ 1113101PR (101). Mice vaccinated with pCIgD⁺CD40L, pCIgD⁺101, and pCIgD⁺CD40L⁺101 developed significantly higher specific antibody titers against BoHV-1 than the pCIgD group (p < 0.01). The animals vaccinated with pCgD⁺pCD40L⁺101 raised significantly higher levels of IgG2a and IgG2b (p < 0.01 and p < 0.001, respectively) than mice vaccinated with pCIgD alone. On the contrary, when the activity of CTL against cells infected with BoHV-1 was measured, the vaccine pCgD⁺pCD40L⁺101 induced significantly higher levels of cytotoxicity activity (p < 0.001) than pCIgD alone. A significant increase in the CD4⁺ populations in the group receiving pCIgD⁺CD40L⁺101 in comparison with the pCIgD group was observed and, also, interferon gamma, interleukin (IL)-6, and IL-17A levels were higher. Considering the results obtained from this study for humoral and cellular responses in mice, the inclusion of pCD40L and 101 as adjuvants in a BoHV-1 DNA vaccine for cattle is highly recommendable.

Dewormer drug fenbendazole has antiviral effects on BoHV-1 productive infection in cell cultures

BACKGROUND

Fenbendazole, a dewormer drug, is used widely in the clinical treatment of parasite infections in animals. Recent studies have shown that fenbendazole has substantial effects on tumor growth, immune responses, and inflammatory responses, suggesting that fenbendazole is a pluripotent drug. Nevertheless, the antiviral effects have not been reported. Fenbendazole can disrupt microtubules, which are essential for multiple viruses infections, suggesting that fenbendazole might have antiviral effects.

OBJECTIVES

This study examined whether fenbendazole could inhibit bovine herpesvirus 1 (BoHV-1) productive infection in cell cultures.

METHODS

The effects of fenbendazole on viral production, transcription of the immediate early (IE) genes, viron-associated protein expression, and the cellular signaling PLC-γ1/Akt pathway were assessed using distinct methods.

RESULTS

Fenbendazole could inhibit BoHV-1 productive infections significantly in MDBK cells in a dose-dependent manner. A time-of-addition assay indicated that fenbendazole affected both the early and late stages in the virus replication cycles. The transcription of IE genes, including BoHV-1 infected cell protein 0 (bICP0), bCP4, and bICP22, as well as the synthesis of viron-associated proteins, were disrupted differentially by the fenbendazole treatment. The treatment did not affect the cellular signaling pathway of PLC-γ1/Akt, a known cascade playing important roles in virus infection.

CONCLUSIONS

Overall, fenbendazole has antiviral effects on BoHV-1 replication.

Two Separate Tyrosine-Based YXXL/Φ Motifs within the Glycoprotein E Cytoplasmic Tail of Bovine Herpesvirus 1 Contribute in Virus Anterograde Neuronal Transport

Bovine herpesvirus 1 (BHV-1) causes respiratory infection and abortion in cattle. Following a primary infection, BHV-1 establishes lifelong latency in the trigeminal ganglia (TG). Periodic reactivation of the latent virus in TG neurons results in anterograde virus transport to nerve endings in the nasal mucosa and nasal virus shedding. The BHV-1 glycoprotein E cytoplasmic tail (gE-CT) is necessary for virus cell-to-cell spread in epithelial cells and neuronal anterograde transport. Recently, we identified two tyrosine residues, Y467 and Y563, within the tyrosine-based motifs ₄₆₇YTSL₄₇₀ and ₅₆₃YTVV₅₆₆, which, together, account for the gE CT-mediated efficient cell-to-cell spread of BHV-1 in epithelial cells. Here, we determined that in primary neuron cultures in vitro, the individual alanine exchange Y467A or Y563A mutants had significantly diminished anterograde axonal spread. Remarkably, the double-alanine-exchanged Y467A/Y563A mutant virus was not transported anterogradely. Following intranasal infection of rabbits, both wild-type (wt) and the Y467A/Y563A mutant viruses established latency in the TG. Upon dexamethasone-induced reactivation, both wt and the mutant viruses reactivated and replicated equally efficiently in the TG. However, upon reactivation, only the wt, not the mutant, was isolated from nasal swabs. Therefore, the gE-CT tyrosine residues Y467 and Y563 together are required for gE CT-mediated anterograde neuronal transport.

β-cantenin is potentially involved in the regulation of c-Jun signaling following bovine herpesvirus 1 infection

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BoHV-1 infection promotes nucleus accumulation of p-c-Jun(S73) and p-β-catenin(S552)

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The association between β-catenin and c-Jun in in nucleus is readily detected following BoHV-1 infection.

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BoHV-1 infection stimulates the expression and activation of c-Jun potentially through β-catenin.

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BoHV-1 infection leads to relocalization of nucleus c-Jun to form specific foci.

C-Jun, activated by various extracellular signals, is important for cell differentiation, proliferation, apoptosis, and inflammatory responses. We have previously reported that bovine herpesvirus 1 (BoHV-1) infection in MDBK cells stimulates the c-Jun NH2-terminal kinase (JNK)/c-Jun cascade for efficient replication. However, the mechanisms regarding the regulation of c-Jun following BoHV-1 infection remain unknown. In this study, we show that virus infection increases accumulation of p-c-Jun(S73) (phosphorylated c-Jun at Ser73) and p-β-catenin(S552) in the nucleus, resulting in relocalized nuclear p-c-Jun(S73) to assemble in highlighted punctum via a confocal microscope assay. An association between β-catenin and c-Jun in the nucleus was readily detected in virus-infected, but not mock-infected cells. Interestingly, β-catenin was found to be involved in the regulation of c-Jun signaling in virus-infected cells as iCRT14, a β-catenin-specific inhibitor that can inhibit β-catenin-dependent transcriptional activity, was able to decrease protein expression and phosphorylation of c-Jun. Furthermore, we suggest that BoHV-1 infection stimulates c-Jun phosphorylation regulated by β-catenin via both c-Jun NH2-terminal kinase (JNK)-dependent and JNK-independent mechanisms. These data add to our knowledge regarding the regulation of c-Jun following virus infection and further support the important roles of β-catenin signaling playing in BoHV-1 infection.

MANα1-2MAN decorated liposomes enhance the immunogenicity induced by a DNA vaccine against BoHV-1

New technologies in the field of vaccinology arise as a necessity for the treatment and control of many diseases. Whole virus inactivated vaccines and modified live virus ones used against Bovine Herpesvirus-1 (BoHV-1) infection have several disadvantages. Previous works on DNA vaccines against BoHV-1 have demonstrated the capability to induce humoral and cellular immune responses. Nevertheless, 'naked' DNA induces low immunogenic response. Thus, loading of antigen encoding DNA sequences in liposomal formulations targeting dendritic cell receptors could be a promising strategy to better activate these antigen-presenting cells (APC). In this work, a DNA-based vaccine encoding the truncated version of BoHV-1 glycoprotein D (pCIgD) was evaluated alone and encapsulated in a liposomal formulation containing LPS and decorated with MANα1-2MAN-PEG-DOPE (pCIgD-Man-L). The vaccinations were performed in mice and bovines. The results showed that the use of pCIgD-Man-L enhanced the immune response in both animal models. For humoral immunity, significant differences were achieved when total antibody titres and isotypes were assayed in sera. Regarding cellular immunity, a significant increase in the proliferative response against BoHV-1 was detected in animals vaccinated with pCIgD-Man-L when compared to the response induced in animals vaccinated with pCIgD. In addition, upregulation of CD40 molecules on the surface of bovine dendritic cells (DCs) was observed when cells were stimulated and activated with the vaccine formulations. When viral challenge was performed, bovines vaccinated with MANα1-2MAN-PEG-DOPE elicited better protection which was evidenced by a lower viral excretion. These results demonstrate that the dendritic cell targeting using MANα1-2MAN decorated liposomes can boost the immunogenicity resulting in a long-lasting immunity. Liposomes decorated with MANα1-2MAN-PEG-DOPE were tested for the first time as a DNA vaccine nanovehicle in cattle as a preventive treatment against BoHV-1. These results open new perspectives for the design of vaccines for the control of bovine rhinotracheitis.

BICP0 Negatively Regulates TRAF6-Mediated NF-κB and Interferon Activation by Promoting K48-Linked Polyubiquitination of TRAF6

The infected cell protein 0 (BICP0) is an immediate early protein encoded by BHV-1, and its RING finger domain, which endows BICP0 with intrinsic E3 ubiquitin ligase activity, is common in all ICP0 proteins. Tumor necrosis factor receptor-associated factor 6 (TRAF6) is one of the TRAF family members and is ubiquitously expressed in mammalian tissues. TRAF6 forms the MyD88-TRAF6-IRF7 complex and activates interferon induction in the TLR (Toll-like receptors) and the RLR (RIG-I-like receptor) pathway. Previous studies showed that BICP0 reduced IFN-β promoter activity by interacting with IRF7. In this study, we found that BICP0 promoted the K48-ubiquitination and degradation of TRAF6 through the ubiquitin proteasome system. The interaction between BICP0 and TRAF6 is a prerequisite for ubiquitination modification, and the 346-PAERQY-351 of BICP0 is indispensable. The motif mutation experiments showed that the tyrosine 351 of BICP0 is the key amino acid involved. Further studies demonstrated that BICP0 suppressed the NF-κB pathway via the interference of TRAF6. Moreover, degradation of TRAF6 protein influenced the K63-linked ubiquitination of IRF7 and activation of interferon promoter. Collectively, these findings indicate that the BICP0 protein suppresses the inflammation signaling and IFN production by K48-linked polyubiquitination of TRAF6 and may further clarify the immune evasion function of BICP0.

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.

The Antiviral Effects of Sodium Phenylbutyrate Against BoHV-1 Infection In Vitro

Introduction:

The alteration of histone acetylation is a known mechanism to regulate gene expression, and thereby affecting various cellular processes. Histone deacetylases (HDACs) are known to regulate histone acetylation by removal of the acetyl group from lysines. HDAC inhibitor such as Sodium Phenylbutyrate (PB) and Valproic Acid (VPA) have been reported to affect multiple virus infection while whether they affect BoHV-1 infection is unknown.

Objective:

The aim of the study is to investigate whether PB and VPA effects BoHV-1 infection and the virus induced inflammation related signaling including Erk1/2 and p38MAPK signaling.

Methods:

To assess the antiviral effects of PB and VPA on BoHV-1 infection, MDBK cells were treated with these inhibitors at different concentrations. Then time addition was performed to pinpoint which stages of virus infection was affected by the chemicals. In order to assess whether PB affect viral gene expression, we detected the viral IE genes such as bICP0, bICP4 and bICP22 using real-time PCR assay. The effects of PB had on the activation of inflammation related signaling including Erk1/2 and p38MAPK in response to the virus infection were also detected.

Results:

Here, for the first time we reveals that PB but not VPA affects BoHV-1 infection at late stages of infection. It affected the expression of IE genes such as bICP0, bICP4 and bICP22. Interestingly, PB enhanced the activation of both Erk1/2 and p38MAPK signaling stimulated by BoHV-1 infection.

Conclusion:

HDAC inhibitor PB significantly inhibited BoHV-1 infection partially through the interruption of certain viral IE gene expression. Though PB has been reported to have antiinflammatory effects, we found that it enhanced the activation of inflammation pertinent signaling of both Erk1/2 and p38MAPK stimulated by BoHV-1 infection.

Differential expression of cyclins mRNA in neural tissues of BoHV-1- and BoHV-5- infected cattle

Bovine alphaherpesvirus types 1 (BoHV-1) and 5 (BoHV-5) are closely related alphaherpesviruses. BoHV-5 causes non-suppurative meningoencephalitis in calves. BoHV-1 is associated with several syndromes and, occasionally, can cause encephalitis. Although both viruses are neurotropic and they share similar biological properties, it is unknown why these alphaherpesviruses differ in their ability to cause neurological disease. Neural tissue samples were collected from BoHV-1- and BoHV-5-intranasally inoculated calves during acute infection, latency and reactivation and the levels of cyclins mRNA expression were analyzed by qRT-PCR. Striking differences in the levels of cyclins mRNA were particularly detected in trigeminal ganglion (TG). The expression levels of cyclins in TG during BoHV-5 latency suggest that these viruses utilize different strategies to persist in the host. It is apparent that a relationship between virus loads and cyclin mRNA levels can be established only during acute infection and other factors might be involved in the regulation of cell cycle components during BoHV latency and reactivation. Bovine alphaherpesviruses neuropathogenicity might be influenced by the differential control of cell cycle components by these herpesviruses. This is the first report on BoHV-5 modulation of cyclins expression in neural tissues from its natural host.

Modulation of cathelicidins, IFNβ and TNFα by bovine alpha-herpesviruses is dependent on the stage of the infectious cycle

Production of antimicrobial peptides cathelicidins, interferons and cytokines is an important feature in airway epithelial host defense. The innate immune response to alpha-herpesvirus infection at the sites of primary replication has not been fully studied. Thus, the aim of this study was to determine the expression of innate immune components, cathelicidins, IFNβ, TNFα and TNF receptors (TNFRI and TNFRII) during acute infection and reactivation of bovine herpesvirus type 1 (BoHV-1) and 5 (BoHV-5) in the respiratory tract and lymphoid tissue of their natural host. We found that BoHV infection modulates mainly the expression of BMAP28, a key cathelicidin in cattle. It was downregulated by both viruses in retropharyngeal lymph nodes of acutely infected-calves, and it was accompanied by a lower expression of IFNβ, TNFα and TNFRI. BoHV-5 showed a pronounced role in the downregulation of BMAP28, even in nasal mucosa and lung. However, during reactivation, BoHV-5 upregulated both BMAP28 and IFNβ in retropharyngeal lymph nodes. Acute replication induced also TNFα mRNA and protein synthesis, and expression of TNFRI and II was positively regulated during both acute infection and reactivation, particularly in the trachea. Moreover, BMAP27 was detected during BoHV-1 reactivation suggesting a potential role at this stage. Thus, cathelicidins are implicated in alpha-herpesvirus infections of the bovine respiratory system and the response is distinct during BoHV-1 and BoHV-5 acute infection and reactivation. This demonstrates that these viruses modulate differentially the components of innate immune response, possibly influencing their pathogenesis. This study provides an initial pilot analysis of factors that might be implicated in alpha-herpesvirus infection of the bovine respiratory system.

Meta-analysis of prevalence of bovine herpes virus 1 in cattle in Mainland China

Bovine herpesvirus 1 (BHV-1), an important pathogen of cattle, can cause severe clinical syndromes including respiratory disease, genital disease, and late-term abortions, as well as neurological and systemic disease in cattle. For assessing the prevalence of BHV-1 infection in mainland China, a systematic review and meta-analysis was conducted. In this systematic review and meta-analysis, we searched English and Chinese literature databases for published paper regarding the prevalence of BHV-1 in cattle in China from inception to May 20, 2018. Search strings included if they reported the cattle samples of more than 30 cattle and provided information that allowed us to establish the prevalence of BHV-1. Moreover, we excluded repeated studies, reviews, other hosts studies, as well as studies with inconsistent data, incomplete information or only provided prevalence data, and out of mainland China data. We extracted how many cattle have BHV-1 infection from the obtained studies, moreover, and calculated pooled prevalence of BHV-1 infection in cattle. The data of 41 articles (including data on 43,441 cattle) are compliant with the standards. The pooled prevalence of BHV-1 in cattle in China was 40%, the pooled prevalence of BHV-1 in cattle from Northeast China (24%) was significant lower than those from other regions. In addition, the prevalence of BHV-1 was associated with publication time of paper, detection methods, age of cattle, and clinical symptoms (pneumonia, abortion etc.).Our findings suggest that BHV-1 is common in cattle in mainland China. It is necessary to monitor the prevalence of BHV-1 in cattle and the powerful and effective regulatory measures should be taken out to prevent the spread of BHV-1.

The Involvement of Histone H3 Acetylation in Bovine Herpesvirus 1 Replication in MDBK Cells

During bovine herpesvirus 1 (BoHV-1) productive infection in cell cultures, partial of intranuclear viral DNA is present in nucleosomes, and viral protein VP22 associates with histones and decreases histone H4 acetylation, indicating the involvement of histone H4 acetylation in virus replication. In this study, we demonstrated that BoHV-1 infection at the late stage (at 24 h after infection) dramatically decreased histone H3 acetylation [at residues K9 (H3K9ac) and K18 (H3K18ac)], which was supported by the pronounced depletion of histone acetyltransferases (HATs) including CBP/P300 (CREB binding protein and p300), GCN5L2 (general control of amino acid synthesis yeast homolog like 2) and PCAF (P300/CBP-associated factor). The depletion of GCN5L2 promoted by virus infection was partially mediated by ubiquitin-proteasome pathway. Interestingly, the viral replication was enhanced by HAT (histone acetyltransferase) activator CTPB [N-(4-Chloro-3-trifluoromethylphenyl)-2-ethoxy-6-pentadecylbenzamide], and vice versa, inhibited by HAT inhibitor Anacardic acid (AA), suggesting that BoHV-1 may take advantage of histone acetylation for efficient replication. Taken together, we proposed that the HAT-dependent histone H3 acetylation plays an important role in BoHV-1 replication in MDBK (Madin-Darby bovine kidney) cells.

Induction of Oxidative DNA Damage in Bovine Herpesvirus 1 Infected Bovine Kidney Cells (MDBK Cells) and Human Tumor Cells (A549 Cells and U2OS Cells)

Bovine herpesvirus 1 (BoHV-1) is an important pathogen of cattle that causes lesions in mucosal surfaces, genital tracts and nervous systems. As a novel oncolytic virus, BoHV-1 infects and kills numerous human tumor cells. However, the mechanisms underlying the virus-induced cell damages are not fully understood. In this study, we demonstrated that virus infection of MDBK cells induced high levels of DNA damage, because the percentage of comet tail DNA (tailDNA%) determined by comet assay, a direct indicator of DNA damage, and the levels of 8-hydroxyguanine (8-oxoG) production, an oxidative DNA damage marker, consistently increased following the virus infection. The expression of 8-oxoguanine DNA glycosylase (OGG-1), an enzyme responsible for the excision of 8-oxoG, was significantly decreased due to the virus infection, which corroborated with the finding that BoHV-1 infection stimulated 8-oxoG production. Furthermore, the virus replication in human tumor cells such as in A549 cells and U2OS cells also induced DNA damage. Chemical inhibition of reactive oxidative species (ROS) production by either ROS scavenger N-Acetyl-l-cysteine or NOX inhibitor diphenylene iodonium (DPI) significantly decreased the levels of tailDNA%, suggesting the involvement of ROS in the virus induced DNA lesions. Collectively, these results indicated that BoHV-1 infection of these cells elicits oxidative DNA damages, providing a perspective in understanding the mechanisms by which the virus induces cell death in both native host cells and human tumor cells.

Bovine Herpesvirus 1 UL49.5 Interacts with gM and VP22 To Ensure Virus Cell-to-Cell Spread and Virion Incorporation: Novel Role for VP22 in gM-Independent UL49.5 Virion Incorporation

Alphaherpesvirus envelope glycoprotein N (gN) and gM form a covalently linked complex. Bovine herpesvirus type 1 (BHV-1) U_L49.5 (a gN homolog) contains two predicted cysteine residues, C42 and C78. The C42 is highly conserved among the alphaherpesvirus gN homologs (e.g., herpes simplex virus 1 and pseudorabies virus). To identify which cysteine residue is required for the formation of the U_L49.5/gM complex and to characterize the functional significance of the U_L49.5/gM complex, we constructed and analyzed C42S and C78S substitution mutants in either a BHV-1 wild type (wt) or BHV-1 U_L49.5 cytoplasmic tail-null (CT-null) virus background. The results demonstrated that BHV-1 U_L49.5 residue C42 but not C78 was essential for the formation of the covalently linked functional U_L49.5/gM complex, gM maturation in the Golgi compartment, and efficient cell-to-cell spread of the virus. Interestingly, the C42S and CT-null mutations separately did not affect mutant U_L49.5 virion incorporation. However, when both of the mutations were introduced simultaneously, the U_L49.5 C42S/CT-null protein virion incorporation was severely reduced. Incidentally, the anti-VP22 antibody coimmunoprecipitated the U_L49.5 C42S/CT-null mutant protein at a noticeably reduced level compared to that of the individual U_L49.5 C42S and CT-null mutant proteins. As expected, in a dual U_L49.5 C42S/VP22Δ virus with deletion of VP22 (VP22Δ), the U_L49.5 C42S virion incorporation was also severely reduced while in a gMΔ virus, U_L49.5 virion incorporation was affected only slightly. Together, these results suggested that U_L49.5 virion incorporation is mediated redundantly, by both U_L49.5/gM functional complex and VP22, through a putative gM-independent novel U_L49.5 and VP22 interaction.IMPORTANCE Bovine herpesvirus 1 (BHV-1) envelope protein U_L49.5 is an important virulence determinant because it downregulates major histocompatibility complex class I (MHC-I). U_L49.5 also forms a covalently linked complex with gM. The results of this study demonstrate that U_L49.5 regulates gM maturation and virus cell-to-cell spread since gM maturation in the Golgi compartment depends on covalently linked U_L49.5/gM complex. The results also show that the U_L49.5 residue cysteine 42 (C42) mediates the formation of the covalently linked U_L49.5-gM interaction. Furthermore, a C42S mutant virus in which U_L49.5 cannot interact with gM has defective cell-to-cell spread. Interestingly, U_L49.5 also interacts with the tegument protein VP22 via its cytoplasmic tail (CT). The putative U_L49.5 CT-VP22 interaction is essential for a gM-independent U_L49.5 virion incorporation and is revealed when U_L49.5 and gM are not linked. Therefore, U_L49.5 virion incorporation is mediated by U_L49.5-gM complex interaction and through a gM-independent interaction between U_L49.5 and VP22.

Bovine herpesvirus type 5 replication and induction of apoptosis in vitro and in the trigeminal ganglion of experimentally-infected cattle

Bovine herpesvirus (BoHV) types 1 and 5 are neuroinvasive. Cases of BoHV-1-induced encephalitis are not as frequent as those caused by BoHV-5. In this study, the capability of BoHV-5 to induce apoptosis in cell cultures and in the trigeminal ganglion during acute infection of experimentally-infected cattle was analyzed. Apoptotic changes in cell cultures agree with the ability of the viral strains to replicate in each cell line. Marked differences were observed between the in vitro induction of apoptosis by BoHV-1Cooper and BoHV-5 97/613 strains. Apoptotic neurons were clearly evident in the trigeminal ganglion of BoHV-1-infected calves. For BoHV-5 a fewer number of positive neurons was observed. There is an association between the magnitude of bovine herpesviruses replication and the induction of apoptosis in trigeminal ganglion. These findings suggest that the induction of apoptosis and the innate immune response orchestrate the final outcome of alpha herpesviruses infection of the bovine nervous system.

A bovine herpesvirus 1 pUL51 deletion mutant shows impaired viral growth in vitro and reduced virulence in rabbits

Bovine herpesvirus 1 (BoHV-1) UL51 protein (pUL51) is a tegument protein of BoHV-1 whose function is currently unknown. Here, we aimed to illustrate the specific role of pUL51 in virion morphogenesis and its importance in BoHV-1 virulence. To do so, we constructed a BoHV-1 bacterial artificial chromosome (BAC). We used recombinant BAC and transgenic techniques to delete a major part of the UL51 open reading frame. Deletion of pUL51 resulted in severe viral growth defects, as evidenced by lower single and multi-step growth kinetics, reduced plaque size, and the accumulation of non-enveloped capsids in the cytoplasm of infected cells. Using tagged BoHV-1 recombinant viruses, it was determined that the pUL51 protein completely co-localized with the cis-Golgi marker protein GM-130. Taken altogether, pUL51 was demonstrated to play a critical role in BoHV-1 growth and it is involved in viral maturation and egress. Moreover, an in vivo analysis showed that the pUL51 mutant exhibited reduced virulence in rabbits, with no clinical signs, no nasal shedding of the virus, and no detectable serum neutralizing antibodies. Therefore, we conclude that the BoHV-1 pUL51 is indispensable for efficient viral growth in vitro and is essential for virulence in vivo.

CD335 (NKp46)+ T-Cell Recruitment to the Bovine Upper Respiratory Tract during a Primary Bovine Herpesvirus-1 Infection

Bovine natural killer (NK) cells were originally defined by the NK activation receptor CD335 [natural killer cell p46-related protein (NKp46)], but following the discovery of NKp46 expression on human T-cells, the definition of conventional bovine NK cells was modified to CD335⁺CD3⁻ cells. Recently, a bovine T-cell population co-expressing CD335 was identified and these non-conventional T-cells were shown to produce interferon (IFN)-γ and share functional properties with both conventional NK cells and T-cells. It is not known, however, if CD335⁺ bovine T-cells are recruited to mucosal surfaces and what chemokines play a role in recruiting this unique T-cell subpopulation. In this study, bovine herpesvirus-1 (BHV-1), which is closely related to herpes simplex virus-1, was used to investigate bovine lymphocyte cell populations recruited to the upper respiratory tract following a primary respiratory infection. Immunohistochemical staining with individual monoclonal antibodies revealed significant (P < 0.05) recruitment of CD335⁺, CD3⁺, and CD8⁺ lymphocyte populations to the nasal turbinates on day 5 following primary BHV-1 infection. Dual-color immunofluorescence revealed that cells recruited to nasal turbinates were primarily T-cells that co-expressed both CD335 and CD8. This non-conventional T-cell population represented 77.5% of CD355⁺ cells and 89.5% of CD8⁺ cells recruited to nasal turbinates on day 5 post-BHV-1 infection. However, due to diffuse IFN-γ staining of nasal turbinate tissue, it was not possible to directly link increased IFN-γ production following BHV-1 infection with the recruitment of non-conventional T-cells. Transcriptional analysis revealed CCL4, CCL5, and CXCL9 gene expression was significantly (P < 0.05) upregulated in nasal turbinate tissue following BHV-1 infection. Therefore, no single chemokine was associated with recruitment of non-conventional T-cells. In conclusion, the specific recruitment of CD335⁺ and CD8⁺ non-conventional T-cells to viral-infected tissue suggests that these cells may play an important role in either the clearance of a primary BHV-1 infection or regulating host responses during viral infection. The early recruitment of non-conventional T-cells following a primary viral infection may enable the host to recognize viral-infected cells through NKp46 while retaining the possibility of establishing T-cell immune memory.

The role of phospholipase C signaling in bovine herpesvirus 1 infection

Bovine herpesvirus 1 (BoHV-1) infection enhanced the generation of inflammatory mediator reactive oxidative species (ROS) and stimulated MAPK signaling that are highly possibly related to virus induced inflammation. In this study, for the first time we show that BoHV-1 infection manipulated phospholipase C (PLC) signaling, as demonstrated by the activation of PLCγ-1 at both early stages [at 0.5 h post-infection (hpi)] and late stages (4-12 hpi) during the virus infection of MDBK cells. Viral entry, and de novo protein expression and/or DNA replication were potentially responsible for the activation of PLCγ-1 signaling. PLC signaling inhibitors of both U73122 and edelfosine significantly inhibited BoHV-1 replication in both bovine kidney cells (MDBK) and rabbit skin cells (RS-1) in a dose-dependent manner by affecting the virus entry stage(s). In addition, the activation of Erk1/2 and p38MAPK signaling, and the enhanced generation of ROS by BoHV-1 infection were obviously ameliorated by chemical inhibition of PLC signaling, implying the requirement of PLC signaling in ROS production and these MAPK pathway activation. These results suggest that the activation of PLC signaling is a potential pathogenic mechanism for BoHV-1 infection.

2,3,7,8-tetrachlorodibenzo-p-dioxin and the viral infection

Exposure to 2,3,7,8-tetrachlorodibenzo-p-dioxin (TCDD), a widespread highly toxic environmental contaminant, suppresses immune response and leads to an increased susceptibility to infectious agents. In particular, several studies have provided evidence that TCDD decreases resistance to numerous viruses. Indeed, in vivo and in vitro investigations showed that the presence of TCDD is able to interfere with the replication of both human and animal viruses, such as influenza A viruses, coxsackie virus B3, immunodeficiency virus type-1 (HIV-1), cytomegalovirus (CMV), herpes simplex II, and bovine herpesvirus 1. Moreover, TCDD could induce an exacerbation of latent infection produced by HIV-1, CMV or Epstein-Barr virus. In this review, we first describe the general effects of TCDD exposure on mammalian cells, then we focus on its influence on the viral infections. Overall, the available data support the concept that TCDD exposure may act as an additional risk factor in promoting of viral diseases.

Induction of Both Local Immune Response in Mice and Protection in a Rabbit Model by Intranasal Immunization with Modified Vaccinia Ankara Virus Expressing a Secreted Form of Bovine Herpesvirus 1 Glycoprotein D

In this study, we evaluated the immunogenicity and efficacy of mucosal delivery of a recombinant modified vaccinia Ankara virus (MVA) expressing the secreted version of bovine herpesvirus type 1 (BoHV-1) glycoprotein D (MVA-gDs) without addition of adjuvant in two animal models. First, we demonstrated the capability of MVA-gDs of inducing both local and systemic anti-gD humoral immune response after intranasal immunization of mice. Then, we confirmed that two doses of MVA-gDs administered intranasally to rabbits induced systemic anti-gD antibodies and conferred protection against BoHV-1 challenge. Our results show the potential of using MVA as a vector for the rational design of veterinary vaccines capable of inducing specific and protective immune responses both at local and systemic level.

Bovine herpesvirus type-1 glycoprotein K (gK) interacts with UL20 and is required for infectious virus production

We have previously shown that the HSV-1 gK and UL20 proteins interact and function in virion envelopment, membrane fusion, and neuronal entry. Alignment of the predicted secondary structures of gKs encoded by BoHV-1, HSV-1, HSV-2, EHV-1 and VZV indicated a high degree of domain conservation. Two BoHV-1 gK-null mutant viruses were created by either gK gene deletion or stop codon insertion. In addition, a V5 epitope-tag was inserted at the carboxyl terminus of gK gene to detect gK. The engineered gK-null mutant viruses failed to replicate and produce viral plaques. Co-immunoprecipitation of gK and UL20 expressed via different methods revealed that gK and UL20 physically interacted in the presence or absence of other viral proteins. Confocal microscopy showed that gK and UL20 colocalized in infected cells. These results indicate that BoHV-1 gK and UL20 may function in a similar manner to other alphaherpesvirus orthologues specified by HSV-1, PRV and EHV-1.

The activation of p38MAPK and JNK pathways in bovine herpesvirus 1 infected MDBK cells

We have shown previously that BHV-1 infection activates Erk1/2 signaling. Here, we show that BHV-1 provoked an early-stage transient and late-stage sustained activation of JNK, p38MAPK and c-Jun signaling in MDBK cells. C-Jun phosphorylation was dependent on JNK. These early events were partially due to the viral entry process. Unexpectedly, reactive oxygen species were not involved in the later activation phase. Interestingly, only activated JNK facilitated the viral multiplication identified through both chemical inhibitor and siRNA. Collectively, this study provides insight into our understanding of early stages of BHV-1 infection.

Recombinant bovine adenovirus-3 co-expressing bovine respiratory syncytial virus glycoprotein G and truncated glycoprotein gD of bovine herpesvirus-1 induce immune responses in cotton rats

One of the impediments in the development of safe and cost effective vaccines for veterinary use has been the availability of appropriate delivery vehicle. We have chosen to develop and use bovine adenovirus (BAdV)-3 as vaccine delivery vector in cattle. Here, we describe the construction of recombinant E3 deleted BAdV-3 vectors expressing single vaccine antigen (BAV360; bovine respiratory syncytial virus G) or two vaccine antigens (BAV851; bovine herpesvirus-1gDt and bovine respiratory syncytial virus G). Recombinant proteins expressed by BAV360 or BAV851 were recognized by protein-specific monoclonal antibodies. Moreover, intranasal immunization of cotton rats with BAV360 (expressing a single vaccine antigen) or BAV851 (expressing two vaccine antigens) induced strong antigen-specific immune responses. These results suggest that single replication-competent BAdV-3 expressing vaccine antigens of two economically important respiratory pathogens of calves has potential to act as a feasible approach in the development of economically effective veterinary vaccines for cattle.