BVDV and innate immunity

Exosomes-mediated transmission of standard bovine viral diarrhea strain OregonC24Va in bovine trophoblast cells

Bovine viral diarrhoea virus (BVDV) can infect cows on days 30-110 of gestation and crossing the placental barrier, resulting in persistently infected (PI) and causing significant economic losses to dairy farming. Bovine placental trophoblast cells (BTCs) are the major cells in the early chorionic tissue of the placenta and play important roles in placental resistance to viral transmission. In this study, we have confirmed that BTCs is among a groups of cell types those could be infected by BVDV in vivo, and BVDV infection stimulates the autophagic responses in BTCs and promotes the release of exosomes. Meanwhile, the exosomes derived from BTCs can be used by BVDV to spread between placental trophoblast cells, and this mode of transmission cannot be blocked by antibodies against the BVDV E2 protein, whereas the replication and spread of BVDV in BTCs can be blocked by inhibiting autophagy and exosomogenesis. Our study provides a theoretical and practical basis for scientific prediction and intervention of reproductive disorders caused by BVDV infection in cows of different gestation periods from a novel perspective.

Mitochondria-mediated ferroptosis contributes to the inflammatory responses of bovine viral diarrhea virus (BVDV) in vitro

Bovine viral diarrhea virus (BVDV) belongs to the family Flaviviridae and includes two biotypes in cell culture: cytopathic (CP) or non-cytopathic (NCP) effects. Ferroptosis is a non-apoptotic form of programmed cell death that contributes to inflammatory diseases. However, whether BVDV induces ferroptosis and the role of ferroptosis in viral infection remain unclear. Here, we provide evidence that both CP and NCP BVDV can induce ferroptosis in Madin-Darby bovine kidney cells at similar rate. Mechanistically, biotypes of BVDV infection downregulate cytoplasmic and mitochondrial GPX4 via Nrf2-GPX4 pathway, thereby resulting in lethal lipid peroxidation and promoting ferroptosis. In parallel, BVDV can degrade ferritin heavy chain and mitochondrial ferritin via NCOA4-mediated ferritinophagy to promote the accumulation of Fe2+ and initiate ferroptosis. Importantly, CP BVDV-induced ferroptosis is tightly associated with serious damage of mitochondria and hyperactivation of inflammatory responses. In contrast, mild or unapparent damage of mitochondria and slight inflammatory responses were detected in NCP BVDV-infected cells. More importantly, different mitophagy pathways in response to mitochondria damage by both biotypes of BVDV are involved in inflammatory responses. Overall, this study is the first to show that mitochondria may play key roles in mediating ferroptosis and inflammatory responses induced by biotypes of BVDV in vitro.IMPORTANCEBovine viral diarrhea virus (BVDV) threatens a wide range of domestic and wild cattle population worldwide. BVDV causes great economic loss in cattle industry through its immunosuppression and persistent infection. Despite extensive research, the mechanism underlying the pathogenesis of BVDV remains elusive. Our data provide the first direct evidence that mitochondria-mediated ferroptosis and mitophagy are involved in inflammatory responses in both biotypes of BVDV-infected cells. Importantly, we demonstrate that the different degrees of injury of mitochondria and inflammatory responses may attribute to different mitophagy pathways induced by biotypes of BVDV. Overall, our findings uncover the interaction between BVDV infection and mitochondria-mediated ferroptosis, which shed novel light on the physiological impacts of ferroptosis on the pathogenesis of BVDV infection, and provide a promising therapeutic strategy to treat this important infectious disease with a worldwide distribution.

[Persistent form of bovine viral diarrhea]

The review provides an analysis of literature data on the persistent form of Bovine Viral diarrhea/Mucosal disease (BVD) and is focused on virus and host factors, including those related to immune response, that contribute the persistence of the virus. BVD is a cattle disease widespread throughout the world that causes significant economic damage to dairy and beef cattle. The disease is characterized by a variety of clinical signs, including damage to the digestive and respiratory organs, abortions, stillbirths and other failures of reproductive functions.

Immune evasion strategies of bovine viral diarrhea virus

Bovine viral diarrhea virus (BVDV) is a significant pathogen that causes great economic losses in the global livestock industry. During the long-term interactions between BVDV and its hosts, the virus has evolved multiple strategies to evade the host's innate immunity and adaptive immunity, thereby promoting viral survival and replication. This review focuses on the most recent research on immune evasion strategies employed by BVDV, including evading type I IFN signaling pathway, evading host adaptive immunity, mediating NF-κB signaling pathway, mediating cell apoptosis and inducing autophagy. Unraveling BVDV's immune evasion strategies will enhance our understanding of the pathogenesis of BVDV and contribute to the development of more effective therapies for the prevention, control and eradication of BVDV.

Integrative Transcriptomics and Proteomics Analysis Reveals Immune Response Process in Bovine Viral Diarrhea Virus-1-Infected Peripheral Blood Mononuclear Cells

Bovine viral diarrhea virus (BVDV) causes bovine viral diarrhea-mucosal disease, inflicting substantial economic losses upon the global cattle industry. Peripheral blood mononuclear cells (PBMCs) are the central hub for immune responses during host-virus infection and have been recognized as crucial targets for BVDV infection. In order to elucidate the dynamics of host-BVDV-1 interaction, this study harnessed RNA-seq and iTRAQ methods to acquire an extensive dataset of transcriptomics and proteomics data from samples of BVDV-1-infected PBMCs at the 12-h post-infection mark. When compared to mock-infected PBMCs, we identified 344 differentially expressed genes (DEGs: a total of 234 genes with downregulated expression and 110 genes with upregulated expression) and 446 differentially expressed proteins (DEPs: a total of 224 proteins with downregulated expression and 222 proteins with upregulated expression). Selected DEGs and DEPs were validated through quantitative reverse transcriptase-polymerase chain reaction and parallel reaction monitoring. Gene ontology annotation and KEGG enrichment analysis underscored the significant enrichment of DEGs and DEPs in various immunity-related signaling pathways, including antigen processing and presentation, complement and coagulation cascades, cytokine-cytokine receptor interaction, and the NOD-like receptor signaling pathway, among others. Further analysis unveiled that those DEGs and DEPs with downregulated expression were predominantly associated with pathways such as complement and coagulation cascades, the interleukin-17 signaling pathway, cytokine-cytokine receptor interaction, the PI3K-Akt signaling pathway, the tumor necrosis factor signaling pathway, and the NOD-like receptor signaling pathway. Conversely, upregulated DEGs and DEPs were chiefly linked to metabolic pathways, oxidative phosphorylation, complement and coagulation cascades, and the RIG-I-like receptor signaling pathway. These altered genes and proteins shed light on the intense host-virus conflict within the immune realm. Our transcriptomics and proteomics data constitute a significant foundation for delving further into the interaction mechanism between BVDV and its host.

Bovine Airway Models: Approaches for Investigating Bovine Respiratory Disease

Bovine respiratory disease (BRD) is a multifactorial condition where different genera of bacteria, such as Mannheimia haemolytica, Histophilus somni, Pasteurella multocida, and Mycoplasma bovis, and viruses, like bovine respiratory syncytial virus, bovine viral diarrhea virus, and bovine herpes virus-1, infect the lower respiratory tract of cattle. These pathogens can co-infect cells in the respiratory system, thereby making specific treatment very difficult. Currently, the most common models for studying BRD include a submerged tissue culture (STC), where monolayers of epithelial cells are typically covered either in cellular or spent biofilm culture medium. Another model is an air-liquid interface (ALI), where epithelial cells are exposed on their apical side and allowed to differentiate. However, limited work has been reported on the study of three-dimensional (3D) bovine models that incorporate multiple cell types to represent the architecture of the respiratory tract. The roles of different defense mechanisms in an infected bovine respiratory system, such as mucin production, tight junction barriers, and the production of antimicrobial peptides in in vitro cultures require further investigation in order to provide a comprehensive understanding of the disease pathogenesis. In this report, we describe the different aspects of BRD, including the most implicated pathogens and the respiratory tract, which are important to incorporate in disease models assembled in vitro. Although current advancements of bovine respiratory cultures have led to knowledge of the disease, 3D multicellular organoids that better recapitulate the in vivo environment exhibit potential for future investigations.

Serum and milk levels of antibodies to bovine viral diarrhoea virus, bovine herpesvirus-1 and -4, and circulation of different bovine herpesvirus-4 genotypes in dairy cattle with clinical mastitis

Introduction

Bovine viral diarrhoea virus (BVDV) and bovine herpesvirus (BoHV)-1 and -4 are important causes of respiratory diseases and reproductive disorders of dairy cattle worldwide.

Material and Methods

Investigation of BVDV and BoHV-1 and -4 antibody levels in the serum and milk of dairy cattle in a group with clinical mastitis and a healthy group was undertaken using an indirect ELISA, and identification of the BoHV-4 genotypes in clinical mastitis cases was attempted by PCR and sequencing.

Results

Antibodies specific to BVDV, BoHV-1 and BoHV-4 were detected in the serum and milk of all dairy cattle with clinical mastitis. The cut-off values for BVDV and BoHV-1 in the sera and milk were extremely high in both healthy and mastitic animals. However, BoHV-4 antibodies were detected only in the clinically mastitic cattle, and BoHV-4 levels were higher in milk than in sera among these animals. Genotypes I and II of BoHV-4 were detected in the milk samples of four seropositive cows with clinical mastitis from the same herd.

Conclusion

The results of this investigation demonstrate that clinical mastitis cases in the same herd may have aetiology in different BoHV-4 genotypes.

Prevalence of bovine viral diarrhea virus in cattle between 2010 and 2021: A global systematic review and meta-analysis

Background

Bovine viral diarrhea is one of the diseases that cause huge economic losses in animal husbandry. Many countries or regions have successively introduced eradication plans, but BVDV still has a high prevalence in the world. This meta-analysis aims to investigate the prevalence and risk factors of BVDV in the world in recent 10 years, and is expected to provide some reference and theoretical basis for BVDV control plans in different regions.

Method

Relevant articles published from 2010 to 2021 were mainly retrieved from NCBI, ScienceDirect, Chongqing VIP, Chinese web of knowledge (CNKI), web of science and Wanfang databases.

Results

128 data were used to analyze the prevalence of BVDV from 2010 to 2021. BVDV antigen prevalence rate is 15.74% (95% CI: 11.35-20.68), antibody prevalence rate is 42.77% (95% CI: 37.01-48.63). In the two databases of antigen and antibody, regions, sampling time, samples, detection methods, species, health status, age, sex, breeding mode, and seasonal subgroups were discussed and analyzed, respectively. In the antigen database, the prevalence of dairy cows in the breed subgroup, ELISA in the detection method subgroup, ear tissue in the sample subgroup, and extensive breeding in the breeding mode were the lowest, with significant differences. In the antibody database, the prevalence rate of dairy cows in the breed subgroup and intensive farming was the highest, with a significant difference. The subgroups in the remaining two databases were not significantly different.

Conclusion

This meta-analysis determined the prevalence of BVDV in global cattle herds from 2010 to 2021. The prevalence of BVDV varies from region to region, and the situation is still not optimistic. In daily feeding, we should pay attention to the rigorous and comprehensive management to minimize the spread of virus. The government should enforce BVDV prevention and control, implement control or eradication policies according to local conditions, and adjust the policies in time.

In Vivo and In Vitro Antiviral Activity of Phlorizin Against Bovine Viral Diarrhea Virus

Bovine viral diarrhea virus (BVDV) is one of the most serious pathogens affecting the cattle industry worldwide. Phlorizin, a kind of flavonoids extracted from apple tree roots, leaves, and fruits, has a variety of biological functions and has been widely used as a herbal supplement and food additive. Here, BALB/c mouse and Madin-Darby bovine kidney (MDBK) cells were used to explore the effect and mechanism of phlorizin against BVDV infection. The results showed that phlorizin significantly inhibited CP BVDV replication and improved the histopathological changes of duodenum and spleen in mice. In vitro studies also confirmed the activity of phlorizin against CP BVDV. Exploration on its potential mechanism suggested that phlorizin inhibited CP BVDV-induced beclin-1 level and the conversion rate of LC3B-I to LC3B-II. Interestingly, although phlorizin also showed a protective effect on MDBK cells, which were treated with 3-methyladenine A (3-MA), the effect was significantly weakened. Furthermore, phlorizin suppressed the stage of BVDV replication but showed no effect on stages of attachment and internalization. Our data further indicated that phlorizin promoted IFN-α and IFN-β levels, decreased IL-1β and IL-6 expression, and regulated RIG-I, MDA5, TLR3, and NLRP3 levels. Similar to CP BVDV results, in vivo and in vitro, phlorizin inhibited NCP BVDV (NY-1 and YNJG2020 strains) infection. These results were the first to be discovered that phlorizin might be used as a new dietary strategy for controlling BVDV infection.

Descriptive analysis of national bovine viral diarrhoea test data in England (2016-2020)

Background

Bovine viral diarrhoea virus (BVDV) causes substantial economic losses to the cattle industry; however, control and eradication can be achieved by identifying and removing persistently infected cattle from the herd. Each UK nation has separate control programmes. The English scheme, BVDFree, started in 2016 and is voluntary.

Methods

We analysed the test results submitted to BVDFree from 5847 herds between 2016 and 2020.

Results

In 2020, 13.5% of beef breeders and 20.0% of dairy herds that submitted tests had at least one positive (virus/antibody) test result. Although lower than in previous years, there was no clear trend in the proportion of positive tests over time. In virus testing herds, 0.4% of individual tests were positive in 2020, and 1.5% of individual tests were positive in BVDV‐positive virus testing herds. Dairy herds and larger herds were more likely to join BVDFree, and dairy herds were also more likely to virus test than beef breeder herds. Larger herds, herds that used virus testing and herds that had BVDV‐positive test results were more likely to continue submitting tests to BVDFree.

Conclusions

The findings provide a benchmark for the status of BVDV control in England; continued analysis of test results will be important to assess progress towards eradication.

Epigenomic and Proteomic Changes in Fetal Spleens Persistently Infected with Bovine Viral Diarrhea Virus: Repercussions for the Developing Immune System, Bone, Brain, and Heart

Bovine viral diarrhea virus (BVDV) infection during early gestation results in persistently infected (PI) immunotolerant calves that are the primary reservoirs of the virus. Pathologies observed in PI cattle include congenital defects of the brain, heart, and bone as well as marked functional defects in their immune system. It was hypothesized that fetal BVDV infection alters T cell activation and signaling genes by epigenetic mechanisms. To test this, PI and control fetal splenic tissues were collected on day 245 of gestation, 170 days post maternal infection. DNA was isolated for reduced representation bisulfite sequencing, protein was isolated for proteomics, both were analyzed with appropriate bioinformatic methods. Within set parameters, 1951 hypermethylated and 691 hypomethylated DNA regions were identified in PI compared to control fetuses. Pathways associated with immune system, neural, cardiac, and bone development were associated with heavily methylated DNA. The proteomic analysis revealed 12 differentially expressed proteins in PI vs. control animals. Upregulated proteins were associated with protein processing, whereas downregulated proteins were associated with lymphocyte migration and development in PI compared to control fetal spleens. The epigenetic changes in DNA may explain the immune dysfunctions, abnormal bone formation, and brain and heart defects observed in PI animals.

Cattle farmer psychosocial profiles and their association with control strategies for bovine viral diarrhea

Bovine viral diarrhea (BVD) is endemic in the United Kingdom and causes major economic losses. Control is largely voluntary for individual farmers and is likely to be influenced by psychosocial factors, such as altruism, trust, and psychological proximity (feeling close) to relevant “others,” such as farmers, veterinarians, the government, and their cows. These psychosocial factors (factors with both psychological and social aspects) are important determinants of how people make decisions related to their own health, many of which have not been studied in the context of infectious disease control by farmers. Farmer psychosocial profiles were investigated using multiple validated measures in an observational survey of 475 UK cattle farmers using the capability, opportunity, motivation-behavior (COM-B) framework. Farmers were clustered by their BVD control practices using latent class analysis. Farmers were split into 5 BVD control behavior classes, which were tested for associations with the psychosocial and COM-B factors using multinomial logistic regression, with doing nothing as the baseline class. Farmers who were controlling disease both for themselves and others were more likely to do something to control BVD (e.g., test, vaccinate). Farmers who did not trust other farmers, had high psychological capability (knowledge and understanding of how to control disease), and had high physical opportunity (time and money to control disease) were more likely to have a closed, separate herd and test. Farmers who did not trust other farmers were also more likely to undertake many prevention strategies with an open herd. Farmers with high automatic motivation (habits and emotions) and reflective motivation (decisions and goals) were more likely to vaccinate and test, alone or in combination with other controls. Farmers with high psychological proximity (feeling of closeness) to their veterinarian were more likely to undertake many prevention strategies in an open herd. Farmers with high psychological proximity to dairy farmers and low psychological proximity to beef farmers were more likely to keep their herd closed and separate and test or vaccinate and test. Farmers who had a lot of trust in other farmers and invested in them, rather than keeping everything for themselves, were more likely to be careful introducing new stock and test. In conclusion, farmer psychosocial factors were associated with strategies for BVD control in UK cattle farmers. Psychological proximity to veterinarians was a novel factor associated with proactive BVD control and was more important than the more extensively investigated trust. These findings highlight the importance of a close veterinarian-farmer relationship and are important for promoting effective BVD control by farmers, which has implications for successful nationwide BVD control and eradication schemes.

First detection of emerging HoBi-like Pestivirus (BVD-3) among some persistently infected dairy cattle herds in Egypt

Bovine viral diarrhoea virus (BVDV) is a serious veterinary health concern worldwide. We conducted this study to determine the prevalence of persistent infections (PI) and identify the current strain among some dairy cattle herds in Egypt. A total of 240 serum samples were collected from six Egyptian provinces. Between 2019 and 2020, samples were tested by Enzyme linked immunosorbent assay (ELISA) for detection of PI animals, and then molecular characterization was performed. Six calves were found PI with a prevalence of 2.5% (6/240). Using molecular characterization, HoBi-like Pestivirus (BVD-3) was successfully identified in Egypt for the first time. Based on the BVD-3 reference strains on Genbank, the detected strains had an identity ranging from 98.8 to 99.6%. Partial nucleotide sequence of the 5'UTR gene for six tested samples was submitted to Genbank with accessions: OM324396, OM324397, OM324398, OM324399, OM3243100, and OM3243101.

Identification of differentially expressed gene pathways between cytopathogenic and non-cytopathogenic BVDV-1 strains by analysis of the transcriptome of infected primary bovine cells

The bovine viral diarrhea virus 1 (BVDV-1), belonging to the Pestivirus genus, is characterized by the presence of two biotypes, cytopathogenic (cp) or non-cytopathogenic (ncp). For a better understanding of the host pathogen interactions, we set out to identify transcriptomic signatures of bovine lung primary cells (BPCs) infected with a cp or a ncp strain. For this, we used both a targeted approach by reverse transcription droplet digital PCR and whole genome approach using RNAseq. Data analysis showed 3571 differentially expressed transcripts over time (Fold Change >2) and revealed that the most deregulated pathways for cp strain are signaling pathways involved in responses to viral infection such as inflammatory response or apoptosis pathways. Interestingly, our data analysis revealed a deregulation of Wnt signaling pathway, a pathway described in embryogenesis, that was specifically seen with the BVDV-1 cp but not the ncp suggesting a role of this pathway in viral replication.

A double deletion prevents replication of the pestivirus bovine viral diarrhea virus in the placenta of pregnant heifers

In contrast to wild type bovine viral diarhea virus (BVDV) specific double deletion mutants are not able to establish persistent infection upon infection of a pregnant heifer. Our data shows that this finding results from a defect in transfer of the virus from the mother animal to the fetus. Pregnant heifers were inoculated with such a double deletion mutant or the parental wild type virus and slaughtered pairwise on days 6, 9, 10 and 13 post infection. Viral RNA was detected via qRT-PCR and RNAscope analyses in maternal tissues for both viruses from day 6 p.i. on. However, the double deletion mutant was not detected in placenta and was only found in samples from animals infected with the wild type virus. Similarly, high levels of wild type viral RNA were present in fetal tissues whereas the genome of the double deletion mutant was not detected supporting the hypothesis of a specific inhibition of mutant virus replication in the placenta. We compared the induction of gene expression upon infection of placenta derived cell lines with wild type and mutant virus via gene array analysis. Genes important for the innate immune response were strongly upregulated by the mutant virus compared to the wild type in caruncle epithelial cells that establish the cell layer on the maternal side at the maternal–fetal interface in the placenta. Also, trophoblasts which can be found on the fetal side of the interface showed significant induction of gene expression upon infection with the mutant virus although with lower complexity. Growth curves recorded in both cell lines revealed a general reduction of virus replication in caruncular epithelial cells compared to the trophoblasts. Compared to the wild type virus this effect was dramtic for the mutant virus that reached only a TCID₅₀ of 1.0 at 72 hours post infection.

Here we report on animal studies elucidating mechanisms preventing the transfer of a double deletion mutant of a pestivirus to the fetus in pregnant heifers. This mutant lacks both known factors engaged in blocking the innate immune response to pestiviral infection. As shown also in earlier studies, this mutant was not detected in the fetuses at any of the tested time points in contrast to the wild-type (wt) virus. However, similar to the wt the mutant was detected in a large variety of different maternal tissues. The only exception was the placenta where only wt but not mutant virus was detected. Using gene array analyses we showed that infection of two cell lines derived either from the maternal or the fetal site of the maternal-fetal interface with the mutant virus induces a significant antiviral gene expression response. The reaction of cells from the maternal side was more complex and virus replication in these cells was reduced, almost completly blocking the mutant virus. These results support the hypothesis that replication of the mutant virus is blocked in the placenta due to a highly active innate immune response and the prevention of replication also blocks transfer of the virus to the fetus.

Genes and regulatory mechanisms associated with experimentally-induced bovine respiratory disease identified using supervised machine learning methodology

Bovine respiratory disease (BRD) is a multifactorial disease involving complex host immune interactions shaped by pathogenic agents and environmental factors. Advancements in RNA sequencing and associated analytical methods are improving our understanding of host response related to BRD pathophysiology. Supervised machine learning (ML) approaches present one such method for analyzing new and previously published transcriptome data to identify novel disease-associated genes and mechanisms. Our objective was to apply ML models to lung and immunological tissue datasets acquired from previous clinical BRD experiments to identify genes that classify disease with high accuracy. Raw mRNA sequencing reads from 151 bovine datasets (n = 123 BRD, n = 28 control) were downloaded from NCBI-GEO. Quality filtered reads were assembled in a HISAT2/Stringtie2 pipeline. Raw gene counts for ML analysis were normalized, transformed, and analyzed with MLSeq, utilizing six ML models. Cross-validation parameters (fivefold, repeated 10 times) were applied to 70% of the compiled datasets for ML model training and parameter tuning; optimized ML models were tested with the remaining 30%. Downstream analysis of significant genes identified by the top ML models, based on classification accuracy for each etiological association, was performed within WebGestalt and Reactome (FDR ≤ 0.05). Nearest shrunken centroid and Poisson linear discriminant analysis with power transformation models identified 154 and 195 significant genes for IBR and BRSV, respectively; from these genes, the two ML models discriminated IBR and BRSV with 100% accuracy compared to sham controls. Significant genes classified by the top ML models in IBR (154) and BRSV (195), but not BVDV (74), were related to type I interferon production and IL-8 secretion, specifically in lymphoid tissue and not homogenized lung tissue. Genes identified in Mannheimia haemolytica infections (97) were involved in activating classical and alternative pathways of complement. Novel findings, including expression of genes related to reduced mitochondrial oxygenation and ATP synthesis in consolidated lung tissue, were discovered. Genes identified in each analysis represent distinct genomic events relevant to understanding and predicting clinical BRD. Our analysis demonstrates the utility of ML with published datasets for discovering functional information to support the prediction and understanding of clinical BRD.

Natural Bovine Coronavirus Infection in a Calf Persistently Infected with Bovine Viral Diarrhea Virus: Viral Shedding, Immunological Features and S Gene Variations

Simple Summary

The evolution of a bovine coronavirus (BCoV) natural infection in a calf persistently infected with bovine viral diarrhea virus (BVDV) was described. The infected calf developed intermittent nasal discharge, diarrhea and hyperthermia. The total number of leukocytes/mL and the absolute differential number of neutrophils and lymphocytes resulted within the normal range, but the monocytes increased at T28 (time 28 post-infection) and the CD8⁺ subpopulation increased at T7 and between T28 and T35. BCoV shedding in nasal discharges and feces was detected up to three weeks post infection (p.i.) and high antibody titers persisted for up to 8 weeks p.i. Virus shedding increased until T14, contrary to what was observed in a previous study where BCoV was detected with a lower load in the co-infected (BCoV/BVDV) calves than in the calves infected with BCoV only. We can suppose that BVDV may have exacerbated the long viral excretion, as well as favoring the onset of mutations in the genome of BCoV. An extensive study was performed to verify if the selective pressure in the S gene could be a natural mode of variation of BCoV.

Abstract

The evolution of a bovine coronavirus (BCoV) natural infection in a calf persistently infected with bovine viral diarrhea virus (BVDV) was described. The infected calf developed intermittent nasal discharge, diarrhea and hyperthermia. The total number of leukocytes/mL and the absolute differential number of neutrophils and lymphocytes resulted within the normal range, but monocytes increased at T28 (time 28 post-infection). Flow-cytometry analysis evidenced that the CD8⁺ subpopulation increased at T7 and between T28 and T35. BCoV shedding in nasal discharges and feces was detected up to three weeks post infection and high antibody titers persisted up to T56. The RNA BCoV load increased until T14, contrary to what was observed in a previous study where the fecal excretion of BCoV was significantly lower in the co-infected (BCoV/BVDV) calves than in the calves infected with BCoV only. We can suppose that BVDV may have modulated the BCoV infection exacerbating the long viral excretion, as well as favoring the onset of mutations in the genome of BCoV detected in fecal samples at T21. An extensive study was performed to verify if the selective pressure in the S gene could be a natural mode of variation of BCoV, providing data for the identification of new epidemic strains, genotypes or recombinant betacoronaviruses.

Stakeholder Perceptions of Disease Management for Dairy Calves: "It's Just Little Things That Make Such a Big Difference"

Calf morbidity and mortality rates are often high in dairy herds, raising animal welfare concerns and negatively affecting farm economic efficiency and future performance. Disease prevention is critical to maintain calves in good health, but interventions are dependent upon the persons conducting them. This paper explores the perceptions of farmers, farm workers, veterinarians, and other advisors on the management of calfhood disease on dairy farms in England. Participants were recruited using purposive and "snowball" sampling, resulting in 40 in-depth, semi-structured interviews-26 with dairy farmers and 14 with advisors. Interviews were recorded, transcribed, and thematically coded. Three major themes were derived on the basis of interview data: disease occurrence and treatments, management of calf environment, and the role of stockmanship and perceived control. Respiratory and gastrointestinal diseases in calves were those reported to be most problematic on dairy farms. Limited time and financial resources caused some farmers and advisors to experience a perceived inability to control calf health without antimicrobial treatments. Overall, the findings emphasise the importance of human influences on calf health and disease in the context of influencing the interactions among the host, pathogens, and the environment. Further research should investigate what "attention to detail" means within different farm contexts and practices, as this was believed to be important in the promotion of better husbandry standards and health. We recommend the use of supportive knowledge exchange processes, including facilitation, to empower farmers to promote continuous improvement in calf health.

Bovine Immunology: Implications for Dairy Cattle

The growing world population (7.8 billion) exerts an increased pressure on the cattle industry amongst others. Intensification and expansion of milk and beef production inevitably leads to increased risk of infectious disease spread and exacerbation. This indicates that improved understanding of cattle immune function is needed to provide optimal tools to combat the existing and future pathogens and improve food security. While dairy and beef cattle production is easily the world's most important agricultural industry, there are few current comprehensive reviews of bovine immunobiology. High-yielding dairy cattle and their calves are more vulnerable to various diseases leading to shorter life expectancy and reduced environmental fitness. In this manuscript, we seek to fill this paucity of knowledge and provide an up-to-date overview of immune function in cattle emphasizing the unresolved challenges and most urgent needs in rearing dairy calves. We will also discuss how the combination of available preventative and treatment strategies and herd management practices can maintain optimal health in dairy cows during the transition (periparturient) period and in neonatal calves.

Recent Advances on the Bovine Viral Diarrhea Virus Molecular Pathogenesis, Immune Response, and Vaccines Development

The bovine viral diarrhea virus (BVDV) consists of two species and various subspecies of closely related viruses of varying antigenicity, cytopathology, and virulence-induced pathogenesis. Despite the great ongoing efforts to control and prevent BVDV outbreaks and the emergence of new variants, outbreaks still reported throughout the world. In this review, we are focusing on the molecular biology of BVDV, its molecular pathogenesis, and the immune response of the host against the viral infection. Special attention was paid to discuss some immune evasion strategies adopted by the BVDV to hijack the host immune system to ensure the success of virus replication. Vaccination is one of the main strategies for prophylaxis and contributes to the control and eradication of many viral diseases including BVDV. We discussed the recent advances of various types of currently available classical and modern BVDV vaccines. However, with the emergence of new strains and variants of the virus, it is urgent to find some other novel targets for BVDV vaccines that may overcome the drawbacks of some of the currently used vaccines. Effective vaccination strategy mainly based on the preparation of vaccines from the homologous circulating strains. The BVDV-E2 protein plays important role in viral infection and pathogenesis. We mapped some important potential neutralizing epitopes among some BVDV genomes especially the E2 protein. These novel epitopes could be promising targets against the currently circulating strains of BVDV. More research is needed to further explore the actual roles of these epitopes as novel targets for the development of novel vaccines against BVDV. These potential vaccines may contribute to the global eradication campaign of the BVDV.

Prevalence of bovine abortion, calf mortality, and bovine viral diarrhea virus (BVDV) persistently infected calves among pastoral, peri-urban, and mixed-crop livestock farms in central and Northwest Ethiopia

Background

Bovine Viral Diarrhea virus (BVDV) is one of important diseases of cattle worldwide causing economic losses to the cattle industry primarily due to increased premature culling and decreased reproductive performance. The virus can cross the placenta during early pregnancy and result in the birth of persistently infected (PI) calves that are efficient transmitters of BVDV and serving as the primary reservoirs for BVDV. Relatively few studies have focused on understanding BVDV seroprevalence, virus detection, genotyping and its distribution in Africa. Most BVDV research in Ethiopia has involved serologic surveys in adult cattle, rather than the identification of PI calves, despite their role in viral shedding and recurring infections. A cross-sectional study was undertaken in three different livestock production systems of Ethiopia with the objective to estimate the prevalence of bovine abortion, calf mortality, and BVDV persistently infected calves.

Results

Ear notch samples (882) collected from calves in 349 households were tested for BVDV antigen using antigen capture enzyme-linked immunosorbent assay (ACE). All samples tested were negative for BVDV antigen. The overall animal level crude abortion and calf mortality prevalence were 4.0% (95% CI: 2.9–5.2) and 9.2% (95% CI: 7.7–11.0) respectively. The lower BVDV PI prevalence may be due to a lower effective contact rate between cattle reared in small-scale extensive production systems in Ethiopia.

Conclusions

This is the first report of BVDV Ag test in Ethiopia and no PI was detected in calves in the study areas. Since BVDV is a disease of great economic importance, this study finding must be interpreted with care since absence of evidence is not evidence of absence and even a single BVDV infected animal can serve as source of infection and contribute to the persistent spread of the virus. Greater attention needs to be given to screening for PI animals through testing large number of animals and culling positive animals. Hence, future research should focus on regions and production systems with high BVDV seroprevalence followed by antigen ELISA or BVDV real-time PCR to detect persistently infected and acutely viremic animals.

Upregulation of interferon-alpha gene in bovine embryos produced in vitro in response to experimental infection with noncytophatic bovine-viral-diarrhea virus

In-vitro fertilization is a routine livestock-breeding technique widely used around the world. Several studies have reported the interaction of bovine viral-diarrhea virus (BVDV) with gametes and in-vitro-produced (IVP) bovine embryos. Since, gene expression in BVDV-infected IVP bovine embryos is scarcely addressed. The aim of this work was to evaluate the differential expression of genes involved in immune and inflammatory response. Groups of 20-25 embryos on Day 6 (morula stage) were exposed (infected) or not (control) to an NCP-BVDV strain in SOF medium. After 24 h, embryos that reached expanded blastocyst stage were washed. Total RNA of each embryo group was extracted to determine the transcription levels of 9 specific transcripts related with antiviral and inflammatory response by SYBR Green real time quantitative (RT-qPCR). Culture media and an aliquot of the last embryos wash on Day 7 were analyzed by titration and virus isolation, respectively. A conventional PCR confirmed BVDV presence in IVP embryos. A significantly higher expression of interferon-α was observed in blastocysts exposed to NCP-BVDV compared to the controls (p < 0.05). In this study, the upregulation of INFα and TLR7 genes involved in inflammatory and immune response in BVDV-infected IVP bovine embryos is a new finding in this field. This differential expression suggest that embryonic cells could function in a manner like immune cells by recognizing and responding early to interaction with viral pathogens. These results provide new insights into the action of BVDV on the complex molecular pathways controlling bovine early embryonic development.

Changes in circulating lymphocytes and lymphoid tissue associated with vaccination of colostrum deprived calves

The objective of this study was to compare immunological responses and lymphoid depletion in young, colostrum deprived calves following administration of vaccines containing modified-live bovine viral diarrhea virus (BVDV). A group of calves exposed to a typical virulence non-cytopathic (ncp) BVDV-2 field strain (ncp exposed) was included to compare responses of calves receiving vaccine to responses generated against a field strain (mimicking a natural infection). A negative control group administered a placebo was used in all comparisons. All vaccines used in the study were administered per manufacturer recommendations while ncp BVDV exposed calves received 5 ml intranasally (2.5 ml/nare; 4.2 × 10⁶ TCID₅₀/ml) of the BVDV-2 field strain. Samples collected at each time point included nasal swabs for virus detection, blood samples for complete blood counts and detection of viremia, PBMCs for flow cytometric analysis, serum for virus neutralization titers, and thymus tissue at necropsy for evaluation of lymphoid depletion. A measurable neutralizing BVDV titer was observed for all treatment groups excluding the control animals, which remained negative during the study period. Virus shedding was only detected from the ncp vaccinated and ncp exposed calves. A decline from baseline was observed for peripheral lymphocyte and CD4⁺ cells for the groups receiving the adjuvanted cytopathic (cp) vaccine, the double deleted genetically modified (ddGM) vaccine, the ncp vaccine and ncp exposed calves, but not for the control group or groups receiving cp vaccines. Thymus depletion was observed for the ncp vaccine and ncp exposed calves and to a lesser extent for the ddGM vaccine calves. Collectively, these data suggest that the virus biotype, method of attenuation, presentation, and use of adjuvant will influence vaccine impacts on lymphoid tissues and the immune response. As such, multiple variables should be considered when determining costs and benefits of vaccination.

Atypical Porcine Pestivirus Circulation and Molecular Evolution within an Affected Swine Herd

Atypical porcine pestivirus (APPV) is a single-stranded RNA virus from the family Flaviviridae, which is linked to congenital tremor (CT) type A-II in newborn piglets. Here, we retrospectively investigated the molecular evolution of APPV on an affected herd between 2013 and 2019. Monitoring was done at regular intervals, and the same genotype of APPV was found during the entire study period, suggesting no introductions from outside the farm. The nucleotide substitutions over time did not show substantial amino acid variation in the structural glycoproteins. Furthermore, the evolution of the virus showed mainly purifying selection, and no positive selection. The limited pressure on the virus to change at immune-dominant regions suggested that the immune pressure at the farm might be low. In conclusion, farms can have circulation of APPV for years, and massive testing and removal of infected animals are not sufficient to clear the virus from affected farms.

Bovine viral diarrhea virus: An updated American College of Veterinary Internal Medicine consensus statement with focus on virus biology, hosts, immunosuppression, and vaccination

Control of bovine viral diarrhea virus (BVDV) in cattle populations across most of the world has remained elusive in spite of advances in knowledge about this viral pathogen. A central feature of virus perseverance in cattle herds is the unique mechanism of persistent infection. Managing BVDV infection in herds involves controlling persistently infected carrier animals using a multidimensional approach of vaccination, biosecurity, and identification of BVDV reservoirs. A decade has passed since the original American College of Veterinary Internal Medicine consensus statement on BVDV. While much has remained the same with respect to clinical signs of disease, pathogenesis of infection including persistent infection, and diagnosis, scientific articles published since 2010 have led to a greater understanding of difficulties associated with control of BVDV. This consensus statement update on BVDV presents greater focus on topics currently relevant to the biology and control of this viral pathogen of cattle, including changes in virus subpopulations, infection in heterologous hosts, immunosuppression, and vaccination.

Attenuated lymphocyte activation leads to the development of immunotolerance in bovine fetuses persistently infected with bovine viral diarrhea virus†

Bovine viral diarrhea virus continues to cost the cattle industry millions of dollars each year despite control measures. The primary reservoirs for bovine viral diarrhea virus are persistently infected animals, which are infected in utero and shed the virus throughout their lifetime. The difficulty in controlling the virus stems from a limited understanding of transplacental transmission and fetal development of immunotolerance. In this study, pregnant bovine viral diarrhea virus naïve heifers were inoculated with bovine viral diarrhea virus on day 75 of gestation and fetal spleens were collected on gestational days 82, 97, 190, and 245. Microarray analysis on splenic RNA from days 82 and 97 revealed an increase in signaling for the innate immune system and antigen presentation to T cells in day 97 persistently infected fetuses compared to controls. Reverse transcription quantitative polymerase chain reaction on select targets validated the microarray revealing a downregulation of type I interferons and lymphocyte markers in day 190 persistently infected fetuses compared to controls. Protein was visualized using western blot and tissue sections were analyzed with hematoxylin and eosin staining and immunohistochemistry. Data collected indicate that fetal immunotolerance to bovine viral diarrhea virus developed between days 97 and 190, with mass attenuation of the immune system on day 190 of gestation. Furthermore, lymphocyte transcripts were initially unchanged then downregulated, suggesting that immunotolerance to the virus stems from a blockage in lymphocyte activation and hence an inability to clear the virus. The identification of lymphocyte derived immunotolerance will aid in the development of preventative and viral control measures to implement before or during pregnancy.

From Beef to Bees: High-Throughput Kinome Analysis to Understand Host Responses of Livestock Species to Infectious Diseases and Industry-Associated Stress

Within human health research, the remarkable utility of kinase inhibitors as therapeutics has motivated efforts to understand biology at the level of global cellular kinase activity (the kinome). In contrast, the diminished potential for using kinase inhibitors in food animals has dampened efforts to translate this research approach to livestock species. This, in our opinion, was a lost opportunity for livestock researchers given the unique potential of kinome analysis to offer insight into complex biology. To remedy this situation, our lab developed user-friendly, cost-effective approaches for kinome analysis that can be readily incorporated into most research programs but with a specific priority to enable the technology to livestock researchers. These contributions include the development of custom software programs for the creation of species-specific kinome arrays as well as comprehensive deconvolution and analysis of kinome array data. Presented in this review are examples of the application of kinome analysis to highlight the utility of the technology to further our understanding of two key complex biological events of priority to the livestock industry: host immune responses to infectious diseases and animal stress responses. These advances and examples of application aim to provide both mechanisms and motivation for researchers, particularly livestock researchers, to incorporate kinome analysis into their research programs.

Lytic cycle of Besnoitia besnoiti tachyzoites displays similar features in primary bovine endothelial cells and fibroblasts

BACKGROUND

Bovine besnoitiosis, caused by the cyst-forming apicomplexan parasite Besnoitia besnoiti, is a chronic and debilitating cattle disease that continues to spread in Europe in the absence of control tools. In this scenario, in vitro culture systems are valuable tools to carry out drug screenings and to unravel host-parasite interactions. However, studies performed in bovine target cells are scarce.

METHODS

The objective of the present study was to obtain primary bovine aortic endothelial cells (BAECs) and fibroblast cell cultures, target cells during the acute and the chronic stage of the disease, respectively, from healthy bovine donors. Afterwards, expression of surface (CD31, CD34 and CD44) and intracellular markers (vimentin and cytokeratin) was studied to characterize cell populations by flow cytometry. Next, the lytic cycle of B. besnoiti tachyzoites was studied in both target cells. Invasion rates (IRs) were determined by immunofluorescence at several time points post-infection, and proliferation kinetics were studied by quantitative PCR (qPCR). Finally, the influence of bovine viral diarrhea virus (BVDV) co-infection on the host cell machinery, and consequently on B. besnoiti invasion and proliferation, was investigated in BAECs.

RESULTS

Morphology and cytometry results confirmed the endothelial and fibroblast origins. CD31 was the surface marker that best discriminated between BAECs and fibroblasts, since fibroblasts lacked CD31 labelling. Expression of CD34 was weak in low-passage BAECs and absent in high-passage BAECs and fibroblasts. Positive labelling for CD44, vimentin and cytokeratin was observed in both BAECs and fibroblasts. Regarding the lytic cycle of the parasite, although low invasion rates (approximately 3-4%) were found in both cell culture systems, more invasion was observed in BAECs at 24 and 72 hpi. The proliferation kinetics did not differ between BAECs and fibroblasts. BVDV infection favoured early Besnoitia invasion but there was no difference in tachyzoite yields observed in BVDV-BAECs compared to BAECs.

CONCLUSIONS

We have generated and characterized two novel standardized in vitro models for Besnoitia besnoiti infection based on bovine primary target BAECs and fibroblasts, and have shown the relevance of BVDV coinfections, which should be considered in further studies with other cattle pathogens.

Diseases associated with bovine viral diarrhea virus subtypes 1a and 2b in beef and dairy cattle in Uruguay

Bovine viral diarrhea virus (BVDV, Pestivirus) causes significant economic losses to the livestock industry worldwide. Although serological surveys show that BVDV exposure is widespread in cattle in Uruguay, BVDV-associated diseases are greatly underreported. The aim of this work is to describe the epidemiological, clinical, pathological, and virological findings from spontaneous outbreaks of BVDV-associated diseases in cattle in Uruguay. Diagnostic investigations were performed during 6 spontaneous disease outbreaks on beef and dairy cattle farms in the departments of Colonia, Rio Negro, and Soriano between November 2016 and April 2018. Carcasses of 8 naturally deceased cattle from these outbreaks were necropsied and subjected to histological examination and immunohistochemistry to detect BVDV antigen in the tissues. Reverse transcription real-time PCR and genomic sequencing were also performed to identify BVDV at the species and subtype levels. Other ancillary diagnostic tests, including bacterial cultures, were performed on a case-by-case basis to rule in/out differential diagnoses based on initial clinicopathological presumptive diagnoses. BVDV-associated conditions that were diagnosed in the 8 cases included mucosal disease, transient postnatal BVDV infections associated with digestive/septicemic salmonellosis by Salmonella serovar typhimurium, Histophilus somni bronchopneumonia, urinary tract coinfections with Escherichia coli and Streptococcus sp., enteric coinfection with coccidia, and transplacental fetal infections and abortions with Neospora caninum coinfection. BVDV-1a and BVDV-2b were each identified in four of the eight cases. We conclude that BVDV-1a and BVDV-2b contribute significantly to disease and mortality in cattle in Uruguay. Future research should estimate the economic impact of BVDV in the Uruguayan livestock sector.

RNA-Seq based transcriptome analysis during bovine viral diarrhoea virus (BVDV) infection

BACKGROUND

Bovine viral diarrhoea virus (BVDV) is the member of the genus Pestivirus within the Flaviviridae family and responsible for severe economic losses in the cattle industry. BVDV can employ 'infect-and-persist' strategy and 'hit-and-run' strategy to remain associated with hosts and thus contributes to BVDV circulation in cattle herds. BVDV have also evolved various strategies to evade the innate immunity of host. To further understand the mechanisms by which BVDV overcomes the host cell innate immune response and provide more clues for further understanding the BVDV-host interaction, in this descriptive study, we conducted a investigation of differentially expressed genes (DEGs) of the host during BVDV infection by RNA-Seq analysis.

RESULTS

Our analysis identified 1297, 1732, 3072, and 1877 DEGs in the comparison groups mock vs. MDBK cells infected with BVDV post 2 h (MBV2h), mock vs. MBV6h, mock vs. MBV12h, and mock vs. MBV24h, respectively. The reproducibility and repeatability of the results were validated by RT-qPCR. Enrichment analyses of GO annotations and KEGG pathways revealed the host DEGs that are potentially induced by BVDV infection and may participate in BVDV-host interactions. Protein-protein interaction (PPI) network analyses identified the potential interactions among the DEGs. Our findings suggested that BVDV infection induced the upregulation of genes involved in lipid metabolism. The expression of genes that have antiviral roles, including ISG15, Mx1, OSA1Y, were found to be downregulated and are thus potentially associated with the inhibition of host innate immune system during BVDV infection. The expression levels of F3, C1R, KNG1, CLU, C3, FB, SERPINA5, SERPINE1, C1S, F2RL2, and C2, which belong to the complement and coagulation signalling cascades, were downregulated during BVDV infection, which suggested that the complement system might play a crucial role during BVDV infection.

CONCLUSION

In this descriptive study, our findings revealed the changes in the host transcriptome expression profile during BVDV infection and suggested that BVDV-infection induced altering the host's metabolic network, the inhibition of the expression of antiviral proteins and genes within the complement system might be contributed to BVDV proliferation. The above findings provided unique insights for further studies on the mechanisms underlying BVDV-host interactions.

Antiviral effects of nisin, lysozyme, lactoferrin and their mixtures against bovine viral diarrhoea virus

Background

Bovine viral diarrhoea virus (BVDV), an enveloped, single-stranded, positive-sense RNA virus from the Flaviviridae family, is a globally distributed bovine pathogen. BVDV infection in cattle, despite having a wide range of clinical manifestations, is invariably responsible for significant economic losses. To counteract these losses, various schemes to control and eradicate BVDV have been implemented, although safe drugs effectively inhibiting the replication of the virus are still lacking. The purpose of this study was to characterize the antiviral effect of naturally occurring proteins and peptide, such as bovine lactoferrin, chicken egg lysozyme, and nisin from Lactococcus lactis, used both individually and in combination, against the cytopathic NADL strain of BVDV in vitro. After determining the cytotoxicity level of each protein or peptide to MDBK cells, its antiviral effects were evaluated using virucidal, cytopathic effect inhibition and viral yield reduction assays. In addition, the influence of the tested compounds on the intracellular viral RNA level was determined.

Results

The highest efficacy among the single treatments was achieved by bovine lactoferrin, which was effective both at the early stages of viral infection and during its entire course, although the effect weakened over time. Nisin and lysozyme were effective at later stages of infection, and the intensity of their effect did not diminish with time. Nisin+lactoferrin and lysozyme+lactoferrin combinations demonstrated stronger antiviral effects than did the single substances. The nisin+lactoferrin mixture present during the whole period of infection produced the strongest anti-BVDV effect in our entire research on both the extracellular viral titre (titre reduction up to 2.875 log ≈ 99.9%) and the intracellular viral RNA level (reduction up to 89%), and this effect intensified over the incubation time.

Conclusions

The tested substances could be applied in bovine viral diarrhoea prevention and therapy, especially when used in combination.

Electronic supplementary material

The online version of this article (10.1186/s12917-019-2067-6) contains supplementary material, which is available to authorized users.

Global knowledge gaps in the prevention and control of bovine viral diarrhoea (BVD) virus

The significant economic impacts of bovine viral diarrhoea (BVD) virus have prompted many countries worldwide to embark on regional or national BVD eradication programmes. Unlike other infectious diseases, BVD control is highly feasible in cattle production systems because the pathogenesis is well understood and there are effective tools to break the disease transmission cycle at the farm and industry levels. Coordinated control approaches typically involve directly testing populations for virus or serological screening of cattle herds to identify those with recent exposure to BVD, testing individual animals within affected herds to identify and eliminate persistently infected (PI) cattle, and implementing biosecurity measures such as double-fencing shared farm boundaries, vaccinating susceptible breeding cattle, improving visitor and equipment hygiene practices, and maintaining closed herds to prevent further disease transmission. As highlighted by the recent DISCONTOOLS review conducted by a panel of internationally recognized experts, knowledge gaps in the control measures are primarily centred around the practical application of existing tools rather than the need for creation of new tools. Further research is required to: (a) determine the most cost effective and socially acceptable means of applying BVD control measures in different cattle production systems; (b) identify the most effective ways to build widespread support for implementing BVD control measures from the bottom-up through farmer engagement and from the top-down through national policy; and (c) to develop strategies to prevent the reintroduction of BVD into disease-free regions by managing the risks associated with the movements of animals, personnel and equipment. Stronger collaboration between epidemiologists, economists and social scientists will be essential for progressing efforts to eradicate BVD from more countries worldwide.

Immunobiotics for the Bovine Host: Their Interaction with Intestinal Epithelial Cells and Their Effect on Antiviral Immunity

The scientific community has reported several cases of microbes that exhibit elevated rates of antibiotic resistance in different regions of the planet. Due to this emergence of antimicrobial resistant microorganisms, the use of antibiotics as promoters of livestock animals' growth is being banned in most countries around the world. One of the challenges of agricultural immunology therefore is to find alternatives by modulating the immune system of animals in drug-independent safe food production systems. In this regard, in an effort to supplant antibiotics from bovine feeds, several alternatives were proposed including the use of immunomodulatory probiotics (immunobiotics). The purpose of this review is to provide an update of the status of the modulation of intestinal antiviral innate immunity of the bovine host by immunobiotics, and the beneficial impact of immunobiotics on viral infections, focused on intestinal epithelial cells (IECs). The results of our group, which demonstrate the capacity of immunobiotic strains to beneficially modulate Toll-like receptor 3-triggered immune responses in bovine IECs and improve the resistance to viral infections, are highlighted. This review provides comprehensive information on the innate immune response of bovine IECs against virus, which can be further investigated for the development of strategies aimed to improve defenses in the bovine host.

Feed Intake and Weight Changes in Bos indicus-Bos taurus Crossbred Steers Following Bovine Viral Diarrhea Virus Type 1b Challenge Under Production Conditions

Bovine viral diarrhea virus (BVDV) has major impacts on beef cattle production worldwide, but the understanding of host animal genetic influence on illness is limited. This study evaluated rectal temperature, weight change and feed intake in Bos indicus crossbred steers (n = 366) that were challenged with BVDV Type 1b, and where family lines were stratified across three vaccine treatments of modified live (MLV), killed, (KV) or no vaccine (NON). Pyrexia classification based on 40.0 °C threshold following challenge and vaccine treatment were investigated for potential interactions with sire for weight change and feed intake following challenge. Pyrexia classification affected daily feed intake (ADFI, p = 0.05), and interacted with day (p < 0.001) for ADFI. Although low incidence of clinical signs was observed, there were marked reductions in average daily gain (ADG) and cumulative feed intake during the first 14 day post-challenge; ADG (CV of 104%) and feed efficiency were highly variable in the 14-day period immediately post-challenge as compared to the subsequent 14-day periods. A sire × vaccine strategy interaction affected ADFI (p < 0.001), and a sire by time period interaction affected ADG (p = 0.03) and total feed intake (p = 0.03). This study demonstrates that different coping responses may exist across genetic lines to the same pathogen, and that subclinical BVDV infection has a measurable impact on cattle production measures.

Characterization of thymus-associated lymphoid depletion in bovine calves acutely or persistently infected with bovine viral diarrhea virus 1, bovine viral diarrhea virus 2 or HoBi-like pestivirus

Naïve pregnant cattle exposed to pestiviruses between 40-125 days of gestation can give birth to persistently infected (PI) calves. Clinical presentation and survivability, in PI cattle, is highly variable even with the same pestivirus strain whereas the clinical presentation in acute infections is more uniform with severity of symptoms being primarily a function of virulence of the infecting virus. The aim of this study was to compare thymic depletion, as measured by comparing the area of the thymic cortex to the medulla (corticomedullary ratio), in acute and persistent infections of the same pestivirus isolate. The same general trends were observed with each pestivirus isolate. Thymic depletion was observed in both acutely and persistently infected calves. The average thymic depletion observed in acutely infected calves was greater than that in age matched PI calves. PI calves, regardless of infecting virus, revealed a greater variability in amount of depletion compared to acutely infected calves. A trend was observed between survivability and depletion of the thymus, with PI calves surviving less than 5 weeks having lower corticomedullary ratios and greater depletion. This is the first study to compare PI and acutely infected calves with the same isolates as well as to evaluate PI calves based on survivability. Further, this study identified a quantifiable phenotype associated with potential survivability.

Within host RNA virus persistence: mechanisms and consequences

In a prototypical response to an acute viral infection it would be expected that the adaptive immune response would eliminate all virally infected cells within a few weeks of infection. However many (non-retrovirus) RNA viruses can establish 'within host' persistent infections that occasionally lead to chronic or reactivated disease. Despite the importance of 'within host' persistent RNA virus infections, much has still to be learnt about the molecular mechanisms by which RNA viruses establish persistent infections, why innate and adaptive immune responses fail to rapidly clear these infections, and the epidemiological and potential disease consequences of such infections.

Comparison of bulk milk antibody and youngstock serology screens for determining herd status for Bovine Viral Diarrhoea Virus

Background

This paper examines the use of Bulk Milk antibody (BM Ab), Youngstock (YS) serology (Check Tests) and Bulk Milk PCR (BM PCR) for determining the presence or absence of animals persistently infected (PI) with Bovine Viral Diarrhoea Virus (BVDV) within a herd. Data is presented from 26 herds where average herd sizes were 343 and 98 animals for dairy and beef units respectively. Seventeen herds had sufficient data to analyse using Receiver Operating Characteristic (ROC) and probability curves enabling calculation of the sensitivity and specificity of BM Ab and YS Check tests for determining the presence of PI animals within herds in this dataset.

Results

Using BM Ab to screen a herd for the presence of PI animals, achieved a herd level sensitivity and specificity of 80.00 % (44.39–97.48 %) and 85.71 % (42.13–99.64 %) respectively (95 % confidence intervals quoted). Sensitivity and specificity of YS Check Tests at a cut off of 3/10 Ab positive YS were 81.82 % (48.22–97.72 %) and 66.67 % (22.28–95.67 %) respectively (95 % confidence interval). These results were achieved by comparing the screening tests to whole herd PI searches that took place 1–19 months after the initial screen with a mean interval of 8 months. Removal of this delay by taking BM samples on the day of a whole herd test and simulating a YS Check Test from the herd test data produced improvements in the reliability of the Check Tests. BM Ab sensitivity and specificity remained unchanged. However, the Check Test sensitivity and specificity improved to 90.9 % (58.72–99.77 %) and 100 % (54.07–100 %) respectively (95 % confidence interval) at a cut of off 2.5/10 Ab positive animals. Our limited BM PCR results identified 5/23 dairy farms with a positive BM PCR result; two contained milking PIs, two had non-milking PIs and another had no PIs identified.

Conclusions

Delaying a PI search following an initial herd screen decreased the diagnostic accuracy and relevance of our results. With careful interpretation, longitudinal surveillance using a combination of the techniques discussed can successfully determine farm status and therefore allow changes in BVDV status to be detected early, thus enabling prompt action in the event of a BVDV incursion.

Bovine Viral Diarrhea Virus Type 2 Impairs Macrophage Responsiveness to Toll-Like Receptor Ligation with the Exception of Toll-Like Receptor 7

Bovine viral diarrhea virus (BVDV) is a member of the Flaviviridae family. BVDV isolates are classified into two biotypes based on the development of cytopathic (cp) or non-cytopathic (ncp) effects in epithelial cell culture. BVDV isolates are further separated into species, BVDV1 and 2, based on genetic differences. Symptoms of BVDV infection range from subclinical to severe, depending on strain virulence, and may involve multiple organ systems and induction of a generalized immunosuppression. During BVDV-induced immune suppression, macrophages, critical to innate immunity, may have altered pathogen recognition receptor (PRR) signaling, including signaling through toll-like receptors (TLRs). Comparison of BVDV 2 strains with different biotypes and virulence levels is valuable to determining if there are differences in host macrophage cellular responses between viral phenotypes. The current study demonstrates that cytopathic (cp), noncytopathic (ncp), high (hv) or low virulence (lv) BVDV2 infection of bovine monocyte-derived macrophages (MDMΦ) result in differential expression of pro-inflammatory cytokines compared to uninfected MDMΦ. A hallmark of cp BVDV2 infection is IL-6 production. In response to TLR2 or 4 ligation, as might be observed during secondary bacterial infection, cytokine secretion was markedly decreased in BVDV2-infected MDMΦ, compared to non-infected MDMΦ. Macrophages were hyporesponsive to viral TLR3 or TLR8 ligation. However, TLR7 stimulation of BVDV2-infected MDMΦ induced cytokine secretion, unlike results observed for other TLRs. Together, these data suggest that BVDV2 infection modulated mRNA responses and induced a suppression of proinflammatory cytokine protein responses to TLR ligation in MDMΦ with the exception of TLR7 ligation. It is likely that there are distinct differences in TLR pathways modulated following BVDV2 infection, which have implications for macrophage responses to secondary infections.

Distribution and Cellular Heterogeneity of Bovine Viral Diarrhea Viral Antigen Expression in the Brain of Persistently Infected Calves: A New Perspective

Persistent infection following in utero exposure to bovine viral diarrhea virus (BVDV) early in gestation is a serious cause of morbidity and mortality in cattle industries worldwide. The brain is a primary target of persistent infection. In the current study, the types of cells infected and topography of viral antigen expression were examined in brain sections from 9 BVDV persistently infected crossbred calves, all less than 1 year of age, by immunohistochemical staining using the 15C5 primary monoclonal antibody. BVDV antigen was detected in the brains of all persistently infected calves. A variety of cell types was infected, including neurons, astrocytes, oligodendroglia, blood vessel-associated cells (pericytes, perivascular macrophages, smooth muscle cells), and cells in the leptomeninges (blood vessel-associated cells). Conclusive demonstration of viral antigen in vascular endothelial cells was elusive. The intensity and distribution of viral antigen staining in neurons were highly variable. Viral antigen staining was most consistent and intense in thalamic nuclei, most notably in dorsal and medial nuclear groups, followed by the hippocampus, entorhinal cortex, basal nuclei, and piriform cortex. Staining in other brain areas was often less intense and inconsistent. The variability in the intensity and topography of viral antigen in the brain may explain the heterogeneity in the clinical manifestations of BVDV-induced disease. Additionally, infection of the brain in persistently infected calves may underlie or at least contribute to endocrine disturbances and immunologic deficits that are protean manifestations of BVDV-induced disease.

Viral Antigen Distribution in the Respiratory Tract of Cattle Persistently Infected with Bovine Viral Diarrhea Virus Subtype 2a

Tissues were obtained at necropsy from the nasal vestibule, turbinates, nasopharynx, trachea, tracheobronchial bifurcation, and lung from each of 10 clinically healthy calves persistently infected (PI) with bovine viral diarrhea virus (BVDV) serotype 2a. Tissues from the nasal vestibule were obtained by biopsy from five additional PI calves. Formalin-fixed tissues were processed for immunohistochemistry to localize the distribution of BVDV throughout the respiratory tract. Antigen distribution and intensity were subjectively evaluated. Throughout the respiratory tract, mononuclear leukocytes, vascular smooth muscle, and endoneural and perineural cells had BVDV immunoreactivity (BVDV-IR). Multifocally, squamous and ciliated columnar epithelium throughout the respiratory tract contained weak to moderate BVDV antigen. Viral antigen was not seen in goblet cells. BVDV-IR in mixed tubuloalveolar glands of the nasal cavity was weak to strong in serous secretory cells and ductular epithelium. Chondrocytes of the concha often contained BVDV antigen diffusely. Nasal mucus-secreting and tracheobronchial glands multifocally contained weak viral signal. In all cases, alveolar macrophages had moderate to strong BVDV-IR, whereas BVDV-IR in alveolar epithelial cells was weak to moderate. BVDV was present in interalveolar leukocytes and mesenchymal cells. Results indicate that serous secretions of the nasal cavity, productive viral infection of epithelium, and infected leukocytes in respiratory secretions are likely major sources of infectious BVDV from PI calves. The presence of BVDV antigen in respiratory epithelium is, at least, indirect support for the notion that this virus predisposes PI cattle to secondary microbial infections.

Evidence for Tunisian-Like Pestiviruses Presence in Small Ruminants in Italy Since 2007

The genus Pestivirus, which belongs to the Flaviviridae family, includes ssRNA+ viruses responsible for infectious diseases in pigs, cattle, sheep, goats and other domestic and wild ruminants. Like most of the RNA viruses, pestivirus has high genome variability with practical consequences on disease epidemiology, diagnosis and control. In addition to the officially recognized species in the genus Pestivirus, such as BVDV-1, BVDV-2, BDV and CSFV, other pestiviruses have been detected. Furthermore, most of the ruminant pestiviruses show low or absent species specificity observed in serological tests and are able to infect multiple species. Particularly, small ruminants are receptive hosts of the most heterogeneous group of pestiviruses. The aim of this study was to carry out the molecular characterization of pestiviruses isolated from sheep and goats in Sicily, Italy. Phylogenetic analysis of two viral genomic regions (a fragment of 5'-UTR and the whole N^pro regions) revealed the presence of different pestivirus genotypes in the analysed goat and sheep herds. Two of five viral isolates were clustered with BVDV-1d viruses, a strain widespread in Italy, but never reported in Sicily. The other three isolates formed a distinct cluster with high similarity to Tunisian isolates, recently proposed as a new pestivirus species. This represents the first evidence for Tunisian-like pestivirus presence in small ruminants in Italy. Furthermore, one of the isolates was collected from a goat, representing the first isolation of Tunisian-like pestivirus from this species.

Innate and adaptive immune responses to in utero infection with bovine viral diarrhea virus

Infection of pregnant cows with noncytopathic (ncp) bovine viral diarrhea virus (BVDV) induces rapid innate and adaptive immune responses, resulting in clearance of the virus in less than 3 weeks. Seven to 14 days after inoculation of the cow, ncpBVDV crosses the placenta and induces a fetal viremia. Establishment of persistent infection with ncpBVDV in the fetus has been attributed to the inability to mount an immune response before 90-150 days of gestational age. The result is 'immune tolerance', persistent viral replication and shedding of ncpBVDV. In contrast, we describe the chronic upregulation of fetal Type I interferon (IFN) pathway genes and the induction of IFN-γ pathways in fetuses of cows infected on day 75 of gestation. Persistently infected (PI) fetal IFN-γ concentrations also increased at day 97 at the peak of fetal viremia and IFN-γ mRNA was significantly elevated in fetal thymus, liver and spleen 14-22 days post maternal inoculation. PI fetuses respond to ncpBVDV infection through induction of Type I IFN and IFN-γ activated genes leading to a reduction in ncpBVDV titer. We hypothesize that fetal infection with BVDV persists because of impaired induction of IFN-γ in the face of activated Type I IFN responses. Clarification of the mechanisms involved in the IFN-associated pathways during BVDV fetal infection may lead to better detection methods, antiviral compounds and selection of genetically resistant breeding animals.

Immune response to bovine viral diarrhea virus--looking at newly defined targets

Bovine viral diarrhea virus (BVDV) has long been associated with a wide variety of clinical syndromes and immune dysregulation, many which result in secondary bacterial infections. Current understanding of immune cell interactions that result in activation and tolerance are explored in light of BVDV infection including: depletion of lymphocytes, effects on neutrophils, natural killer cells, and the role of receptors and cytokines. In addition, we review some new information on the effect of BVDV on immune development in the fetal liver, the role of resident macrophages, and greater implications for persistent infection.

Global transcriptomic profiling of bovine endometrial immune response in vitro. II. Effect of bovine viral diarrhea virus on the endometrial response to lipopolysaccharide

Infection with noncytopathic bovine viral diarrhea virus (ncpBVDV) is associated with uterine disease and infertility. This study investigated the influence of ncpBVDV on immune functions of the bovine endometrium by testing the response to bacterial lipopolysaccharide (LPS). Primary cultures of mixed epithelial and stromal cells were divided into four treatment groups (control [CONT], BVDV, CONT+LPS, and BVDV+LPS) and infected with ncpBVDV for 4 days followed by treatment with LPS for 6 h. Whole-transcriptomic gene expression was measured followed by Ingenuity Pathway Analysis. Differential expression of 184 genes was found between CONT and BVDV treatments, showing interplay between induction and inhibition of responses. Up-regulation of TLR3, complement, and chemotactic and TRIM factors by ncpBVDV all suggested an ongoing immune response to viral infection. Down-regulation of inflammatory cytokines, chemokines, CXCR4, and serine proteinase inhibitors suggested mechanisms by which ncpBVDV may simultaneously counter the host response. Comparison between BVDV+LPS and CONT+LPS treatments showed 218 differentially expressed genes. Canonical pathway analysis identified the key importance of interferon signaling. Top down-regulated genes were RSAD2, ISG15, BST2, MX2, OAS1, USP18, IFIT3, IFI27, SAMD9, IFIT1, and DDX58, whereas TRIM56, C3, and OLFML1 were most up-regulated. Many of these genes are also regulated by IFNT during maternal recognition of pregnancy. Many innate immune genes that typically respond to LPS were inhibited by ncpBVDV, including those involved in pathogen recognition, inflammation, interferon response, chemokines, tissue remodeling, cell migration, and cell death/survival. Infection with ncpBVDV can thus compromise immune function and pregnancy recognition, thereby potentially predisposing infected cows to postpartum bacterial endometritis and reduced fertility.

Bovine Viral Diarrhea Virus-Associated Disease in Feedlot Cattle

Bovine viral diarrhea virus (BVDv) is associated with bovine respiratory disease complex and other diseases of feedlot cattle. Although occasionally a primary pathogen, BVDv's impact on cattle health is through the immunosuppressive effects of the virus and its synergism with other pathogens. The simple presence or absence of BVDv does not result in consistent health outcomes because BVDv is only one of many risk factors that contribute to disease syndromes. Current interventions have limitations and the optimum strategy for their uses to limit the health, production, and economic costs associated with BVDv have to be carefully considered for optimum cost-effectiveness.

Bovine viral diarrhea virus type 2 in vivo infection modulates TLR4 responsiveness in differentiated myeloid cells which is associated with decreased MyD88 expression

Symptoms of bovine viral diarrhea virus (BVDV) infection range from subclinical to severe, depending on strain virulence. Several in vitro studies showed BVDV infection impaired leukocyte function. Fewer studies have examined the effects of in vivo BVDV infection on monocyte/macrophage function, especially with strains of differing virulence. We characterized cytokine production by bovine myeloid cells isolated early or late in high (HV) or low virulence (LV) BVDV2 infection. Given BVDV infection may enhance susceptibility to secondary bacterial infection, LPS responses were examined as well. Monocytes from HV and LV infected calves produced higher levels of cytokines compared to cells from controls. In contrast, monocyte-derived macrophage cytokine levels were generally reduced. Modulated cytokine expression in HV BVDV2 macrophages was associated with decreased MyD88 expression, likely due to its interaction with viral NS5A. These data and those of others, suggest that certain Flaviviridae may have evolved strategies for subverting receptor signaling pathways involving MyD88.

Effects of Preinfection With Bovine Viral Diarrhea Virus on Immune Cells From the Lungs of Calves Inoculated With Bovine Herpesvirus 1.1

The aim of this work was to study the interstitial aggregates of immune cells observed in pulmonary parenchyma of calves preinfected with bovine viral diarrhea virus and challenged later with bovine herpesvirus 1. In addition, the intent of this research was to clarify the role of bovine viral diarrhea virus in local cell-mediated immunity and potentially in predisposing animals to bovine respiratory disease complex. Twelve Friesian calves, aged 8 to 9 months, were inoculated with noncytopathic bovine viral diarrhea virus genotype 1. Ten were subsequently challenged with bovine herpesvirus 1 and euthanized at 1, 2, 4, 7, or 14 days postinoculation. The other 2 calves were euthanized prior to the second inoculation. Another cohort of 10 calves was inoculated only with bovine herpesvirus 1 and then were euthanized at the same time points. Two calves were not inoculated with any agent and were used as negative controls. Pulmonary lesions were evaluated in all animals, while quantitative and biosynthetic changes in immune cells were concurrently examined immunohistochemically to compare coinfected calves and calves challenged only with bovine herpesvirus 1. Calves preinfected with bovine viral diarrhea virus demonstrated moderate respiratory clinical signs and histopathologic evidence of interstitial pneumonia with aggregates of mononuclear cells, which predominated at 4 days postinoculation. Furthermore, this group of animals was noted to have a suppression of interleukin-10 and associated alterations in the Th1-driven cytokine response in the lungs, as well as inhibition of the response of CD8+ and CD4+ T lymphocytes against bovine herpesvirus 1. These findings suggest that bovine viral diarrhea virus preinfection could affect the regulation of the immune response as modulated by regulatory T cells, as well as impair local cell-mediated immunity to secondary respiratory pathogens.

Analysis of mRNA expression for genes associated with regulatory T lymphocytes (CD25, FoxP3, CTLA4, and IDO) after experimental infection with bovine viral diarrhea virus of low or high virulence in beef calves

Immunosuppression caused by bovine viral diarrhea virus (BVDV) has been associated with lymphocyte depletion, leukopenia and impairment of leukocyte function; however, no work has been done on the relationship between BVDV and regulatory T lymphocytes (Tregs). The objective of this study was to compare the mRNA expression of genes associated with Tregs (CD25, FoxP3, CTLA4, and IDO), after experimental infection of beef calves with low (LV) or high (HV) virulence BVDV. Thirty BVDV-naïve calves were randomly assigned to three groups. Calves were intra-nasally inoculated with LV (n=10, strain SD-1) or HV (n=10, strain 1373) BVDV or BVDV-free cell culture medium (control, n=10). Quantitative RT-PCR was used to determine the expression of target genes in tracheo-bronchial lymph nodes and spleen on day 5 post-infection. The mRNA expression of CD25 was up-regulated in tracheo-bronchial lymph nodes of LV (P<0.05), but not in HV compared to the control group. The expression of FoxP3 and CTLA4 was not increased in tracheo-bronchial lymph nodes of either of the BVDV-inoculated groups. A dramatic up-regulation of IDO mRNA was observed in tracheo-bronchial lymph nodes of LV (P<0.05), but not HV compared to the control calves. In conclusion, experimental infection with BVDV did not provide evidence of Treg activation based on expression of FoxP3 and CTL4. Differential expression of CD25 and IDO mRNA on day 5 post-infection with HV or LV BVDV might reflect temporal differences in transcription occurring during the immune response elicited by these viral strains, or differences in viral infectivity of the host cells.