Bovine respiratory syncytial virus infection: immunopathogenic mechanisms

Characterizing the influence of various antimicrobials used for metaphylaxis against bovine respiratory disease on host transcriptome responses

Currently, control against bovine respiratory disease (BRD) primarily consists of mass administration of an antimicrobial upon arrival to facility, termed "metaphylaxis." The objective of this study was to determine the influence of six different antimicrobials used as metaphylaxis on the whole blood host transcriptome in healthy steers upon and following arrival to the feedlot. One hundred and five steers were stratified by arrival body weight (BW = 247 ± 28 kg) and randomly and equally allocated to one of seven treatments: negative control (NC), ceftiofur (CEFT), enrofloxacin (ENRO), florfenicol (FLOR), oxytetracycline (OXYT), tildipirosin (TILD), or tulathromycin (TULA). On day 0, whole blood samples and BW were collected prior to a one-time administration of the assigned antimicrobial. Blood samples were collected again on days 3, 7, 14, 21, and 56. A subset of cattle (n = 6) per treatment group were selected randomly for RNA sequencing across all time points. Isolated RNA was sequenced (NovaSeq 6,000; ~35 M paired-end reads/sample), where sequenced reads were processed with ARS-UCD1.3 reference-guided assembly (HISAT2/StringTie2). Differential expression analysis comparing treatment groups to NC was performed with glmmSeq (FDR ≤ 0.05) and edgeR (FDR ≤ 0.1). Functional enrichment was performed with KOBAS-i (FDR ≤ 0.05). When compared only to NC, unique differentially expressed genes (DEGs) found within both edgeR and glmmSeq were identified for CEFT (n = 526), ENRO (n = 340), FLOR (n = 56), OXYT (n = 111), TILD (n = 3,001), and TULA (n = 87). At day 3, CEFT, TILD, and OXYT shared multiple functional enrichment pathways related to T-cell receptor signaling and FcεRI-mediated NF-kappa beta (kB) activation. On day 7, Class I major histocompatibility complex (MHC)-mediated antigen presentation pathways were enriched in ENRO and CEFT groups, and CEFT and FLOR had DEGs that affected IL-17 signaling pathways. There were no shared pathways or Gene Ontology (GO) terms among treatments at day 14, but TULA had 19 pathways and eight GO terms enriched related to NF- κβ activation, and interleukin/interferon signaling. Pathways related to cytokine signaling were enriched by TILD on day 21. Our research demonstrates immunomodulation and potential secondary therapeutic mechanisms induced by antimicrobials commonly used for metaphylaxis, providing insight into the beneficial anti-inflammatory properties antimicrobials possess.

Identification of a DRB3*011:01-restricted CD4+ T cell response against bovine respiratory syncytial virus fusion protein

Although Human Respiratory Syncytial Virus (HRSV) is a significant cause of severe respiratory disease with high morbidity and mortality in pediatric and elderly populations worldwide there is no licensed vaccine. Bovine Respiratory Syncytial Virus (BRSV) is a closely related orthopneumovirus with similar genome structure and high homology between structural and nonstructural proteins. Like HRSV in children, BRSV is highly prevalent in dairy and beef calves and known to be involved in the etiology of bovine respiratory disease, in addition to being considered an excellent model for HRSV. Commercial vaccines are currently available for BRSV, though improvements in efficacy are needed. The aims of this study were to identify CD4+ T cell epitopes present in the fusion glycoprotein of BRSV, an immunogenic surface glycoprotein that mediates membrane fusion and a major target of neutralizing antibodies. Overlapping peptides representing three regions of the BRSV F protein were used to stimulate autologous CD4+ T cells in ELISpot assays. T cell activation was observed only in cells from cattle with the DRB3*011:01 allele by peptides from AA249-296 of the BRSV F protein. Antigen presentation studies with C-terminal truncated peptides further defined the minimum peptide recognized by the DRB3*011:01 allele. Computationally predicted peptides presented by artificial antigen presenting cells further confirmed the amino acid sequence of a DRB3*011:01 restricted class II epitope on the BRSV F protein. These studies are the first to identify the minimum peptide length of a BoLA-DRB3 class II-restricted epitope in BRSV F protein.

ChAd155-RSV vaccine is immunogenic and efficacious against bovine RSV infection-induced disease in young calves

Respiratory syncytial virus (RSV) infection causes a substantial lower-respiratory-tract disease burden in infants, constituting a global priority for vaccine development. We evaluated immunogenicity, safety and efficacy of a chimpanzee adenovirus (ChAd)-based vaccine candidate, ChAd155-RSV, in a bovine RSV (bRSV) challenge model. This model closely reproduces the pathogenesis/clinical manifestations of severe pediatric RSV disease. In seronegative calves, ChAd155-RSV elicits robust neutralizing antibody responses against human RSV. Two doses protect calves from clinical symptoms/lung pathological changes, and reduce nasal/lung virus loads after both a short (4-week) and a long (16-week) interval between last immunization and subsequent bRSV challenge. The one-dose regimen confers near-complete or significant protection after short-term or long-term intervals before challenge, respectively. The presence of pre-existing bRSV-antibodies does not affect short-term efficacy of the two-dose regimen. Immunized calves present no clinical signs of enhanced respiratory disease. Collectively, this supports the development of ChAd155-RSV as an RSV vaccine candidate for infants.

The titers, duration, and residual clinical protection of passively transferred nasal and serum antibodies are similar among beef calves that nursed colostrum from vaccinated or unvaccinated dams and were challenged experimentally with bovine respiratory syncytial virus at three months of age

OBJECTIVES

To compare initial titers, duration, and residual clinical protection of passively transferred bovine respiratory syncytial virus (BRSV) nasal immunoglobulin (Ig) G-1 and IgA, and serum neutralizing (SN) antibodies.

ANIMALS

40 three-month-old beef steers born either to unvaccinated or vaccinated cows.

PROCEDURES

During the last trimester of gestation, cows were assigned randomly to either vaccinated or unvaccinated groups. Calves were grouped on the basis of whether they nursed colostrum from unvaccinated dams (NO-VACC group; n = 20) versus dams vaccinated with 2 doses of an inactivated BRSV vaccine (VACC group; n = 20). At 3 months of age, calves were challenged with BRSV. Respiratory signs were scored. Nasal BRSV IgG-1 and IgA and SN antibodies were compared before and after the challenge. The presence of BRSV in nasal secretions was evaluated by reverse transcription-PCR assays.

RESULTS

Respiratory scores after BRSV challenge were similar between treatment groups. Nasal BRSV IgG-1 and SN antibodies were significantly greater in VACC calves at 48 hours of life; however, by 3 months of age, titers had decayed in both groups. Nasal BRSV IgA titers were minimal after colostrum intake and before the BRSV challenge, and increased in both groups after the challenge. The NO-VACC group had a significantly greater probability of shedding BRSV compared with VACC calves.

CLINICAL RELEVANCE

At 3 months of age, titers of passively transferred BRSV antibodies in VACC and NO-VACC calves had decayed to nonprotective levels. Calves born to vaccinated dams had a decreased probability of BRSV shedding; however, this was not related to differences in SN or nasal BRSV antibody titers.

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.

Effects of vitamin E supplementation on serum oxidative stress biomarkers, antibody titer after live bovine respiratory syncytial virus vaccination, as well as serum and fecal immunoglobulin A in weaned Japanese Black calves

The purpose of this study was to determine the effects of vitamin E supplementation on blood oxidative stress biomarker in weaned calves. Thirty clinically healthy 12 weeks of age Japanese Black calves were randomly assigned to two groups: 15 calves received 300 IU of vitamin E daily from 12 to 18 weeks of age (VE group), and the other 15 calves did not receive the vitamin E (control group). Blood samples were taken at 12, 14, 16, 18, and 20 weeks of age. The concentration of serum reactive oxygen metabolites at 20 weeks of age were significantly lower in the VE group than those in the control group. Vitamin E supplementation to weaned calves might affect blood oxidative stress.

Neutrophil extracellular traps (NETs) in a randomized controlled trial of a combination of antiviral and nonsteroidal anti-inflammatory treatment in a bovine model of respiratory syncytial virus infection

The function of neutrophils in viral infections has long been established and studies have been done to examine the role of neutrophil extracellular traps (NETs). Further study and analysis of NETs in viral infections may reveal a new therapeutic target. Administration of ibuprofen and GS-561937, a fusion protein inhibitor (FPI), have been experimentally shown to decrease the severity of bovine respiratory syncytial virus (BRSV) infection. Our aims were to determine the effect of ibuprofen and FPI on NETs after BRSV infection as a monotherapy or combined therapy.

METHODS

We conducted a randomized placebo-controlled trial of ibuprofen, FPI, or as a dual therapy initiated at 3 or 5 days after experimental infection with BRSV in 36 five to six-week-old Holstein calves (Bos Taurus). Lung tissue samples were collected and stained with antibodies conjugated with fluorescence dyes to visualize and quantify the NETs in situ. We estimated the average NETs in the sample lung tissue slides and compared the areas occupied by NETS within and between the treatment groups.

RESULTS

There were significantly fewer NETs in the lung tissue from calves that were given ibuprofen and both ibuprofen and fusion protein inhibitor from day 3 post infection compared to the placebo group. Calves administered with ibuprofen, fusion protein inhibitor or both from day five had visually fewer NETs than the placebo but the difference was not significant.

CONCLUSION

BRSV can induce NET formation in vitro and in vivo. A combination of both drugs (Ibuprofen and FPI) resulted in less NETs observed in lung tissue of BRSV infected calves compared to the placebo or monotherapy groups.

The contribution of bovines to human health against viral infections

In the last 40 years, novel viruses have evolved at a much faster pace than other pathogens. Viral diseases pose a significant threat to public health around the world. Bovines have a longstanding history of significant contributions to human nutrition, agricultural, industrial purposes, medical research, drug and vaccine development, and livelihood. The life cycle, genomic structures, viral proteins, and pathophysiology of bovine viruses studied in vitro paved the way for understanding the human counterparts. Calf model has been used for testing vaccines against RSV, papillomavirus vaccines and anti-HCV agents were principally developed after using the BPV and BVDV model, respectively. Some bovine viruses-based vaccines (BPIV-3 and bovine rotaviruses) were successfully developed, clinically tried, and commercially produced. Cows, immunized with HIV envelope glycoprotein, produced effective broadly neutralizing antibodies in their serum and colostrum against HIV. Here, we have summarized a few examples of human viral infections for which the use of bovines has contributed to the acquisition of new knowledge to improve human health against viral infections covering the convergence between some human and bovine viruses and using bovines as disease models. Additionally, the production of vaccines and drugs, bovine-based products were covered, and the precautions in dealing with bovines and bovine-based materials.

Evaluation of specific immunoglobulin A in nasal secretions and neutralizing antibodies in serum collected at multiple time points from young beef calves following intranasal or subcutaneous administration of a modified-live bovine respiratory syncytial virus vaccine

OBJECTIVE

To determine anti-bovine respiratory syncytial virus (BRSV) antibody titers for nasal secretions and serum from beef calves following administration of a modified-live (MLV) BRSV vaccine.

ANIMALS

60 healthy newborn purebred beef calves.

PROCEDURES

Calves were randomly assigned to 1 of 3 groups: intranasal (IN)-SC (IN MLV BRSV vaccine within 24 hours of birth and SC MLV BRSV vaccine at 2 months of age), SC-IN (SC MLV BRSV vaccine within 24 hours of birth and IN MLV BRSV vaccine at 2 months of age), or NO-IN (no vaccine within 24 hours of birth and IN MLV BRSV vaccine at 2 months of age). Nasal secretion and serum samples were collected for determination of anti-BRSV antibodies within 24 hours of birth and 2 and 6 months of age.

RESULTS

Titers of anti-BRSV IgA antibodies in nasal secretions and BRSV neutralizing antibodies in serum were similar among groups at each sampling time. Within 24 hours of birth, nasal anti-BRSV IgA titers were negligible. At 2 months, mean nasal anti-BRSV IgA titers for calves in IN-SC, SC-IN, and NO-IN groups were 192.84, 224.49, and 114.71, respectively.

CONCLUSIONS AND CLINICAL RELEVANCE

Concentrations of anti-BRSV IgA antibodies in the nasal secretions and BRSV neutralizing antibodies in the serum of young beef calves following an MLV BRSV vaccine protocol that consisted of IN or SC vaccine within 24 hours of birth and vice versa at 2 months of age were not different from that following only an IN MLV BRSV vaccine at 2 months of age. However, the lack of any differences may have been attributed to other factors.

A randomized controlled trial comparing non-steroidal anti-inflammatory and fusion protein inhibitors singly and in combination on the histopathology of bovine respiratory syncytial virus infection

Bovine respiratory syncytial virus (RSV) has substantial morbidity in young calves, and closely parallels human RSV in infants. We performed a randomized controlled trial in five to six-week-old Holstein calves (Bos taurus). comparing fusion protein inhibitor (FPI) and non-steroidal anti-inflammatory drug (NSAID) singly and in combination at three and five days after experimental BRSV infection. Thirty-six calves received one of six treatments; Ibuprofen started on day 3, Ibuprofen started on day 5, FPI started on day 5, FPI and Ibuprofen started on day 3, FPI and Ibuprofen started on day 5, or placebo. We have previously reported significant clinical benefits when combined FPI and NSAID treatment was started at three and five days after bovine RSV infection. Necropsy was performed on Day 10 following infection and hematoxylin and eosin staining was performed on sections from each lobe. Histology was described using a four-point scale. We performed canonical discrimination analysis (CDA) to determine the structural level where differences between treatments occurred and mixed effects regression to estimate effect sizes. Separation from placebo was maximal for dual therapy at the levels of the alveolus, septum, and bronchus in CDA. We found that the clinical benefits of combined FPI and NSAID treatment of BRSV extend at least partially from histopathological changes in the lung when treatment was started three days after infection. We found decreased lung injury when ibuprofen was started as monotherapy on day 3, but not day 5 following infection. Combined therapy with both an FPI and ibuprofen was always better than ibuprofen alone. We did not prove that the clinical benefits seen starting FPI and ibuprofen five days after infection can be solely explained by histopathological differences as identified on H&E staining.

Elucidation of the Host Bronchial Lymph Node miRNA Transcriptome Response to Bovine Respiratory Syncytial Virus

Bovine respiratory disease (BRD) causes substantial morbidity and mortality, affecting cattle of all ages. One of the main causes of BRD is an initial inflammatory response to bovine respiratory syncytial virus (BRSV). MicroRNAs are novel and emerging non-coding small RNAs that regulate many biological processes and are implicated in various inflammatory diseases. The objective of the present study was to elucidate the changes in the bovine bronchial lymph node miRNA transcriptome in response to BRSV following an experimental viral challenge. Holstein-Friesian calves were either administered a challenge dose of BRSV (103.5 TCID50/ml × 15 ml) (n = 12) or were mock inoculated with sterile phosphate buffered saline (n = 6). Daily scoring of clinical signs was performed and calves were euthanized at day 7 post-challenge. Bronchial lymph nodes were collected for subsequent RNA extraction and sequencing (75 bp). Read counts for known miRNAs were generated using the miRDeep2 package using the UMD3.1 reference genome and the bovine mature miRNA sequences from the miRBase database (release 22). EdgeR was used for differential expression analysis and Targetscan was used to identify target genes for the differentially expressed (DE) miRNAs. Target genes were examined for enriched pathways and gene ontologies using Ingenuity Pathway Analysis (Qiagen). Multi-dimensional scaling (MDS) based on miRNA gene expression changes, revealed a clearly defined separation between the BRSV challenged and control calves, although the clinical manifestation of disease was only mild. One hundred and nineteen DE miRNAs (P < 0.05, FDR < 0.1, fold change > 1.5) were detected between the BRSV challenged and control calves. The DE miRNAs were predicted to target 465 genes which were previously found to be DE in bronchial lymph node tissue, between these BRSV challenged and control calves. Of the DE predicted target genes, 455 had fold changes that were inverse to the corresponding DE miRNAs. There were eight enriched pathways among the DE predicted target genes with inverse fold changes to their corresponding DE miRNA including: granulocyte and agranulocyte adhesion and diapedesis, interferon signalling and role of pathogen recognition receptors in recognition of bacteria and viruses. Functions predicted to be increased included: T cell response, apoptosis of leukocytes, immune response of cells and stimulation of cells. Pathogen recognition and proliferation of cytotoxic T cells are vital for the recognition of the virus and its subsequent elimination.

Supplementing a Saccharomyces cerevisiae fermentation product modulates innate immune function and ameliorates bovine respiratory syncytial virus infection in neonatal calves

The objectives of this study were to determine the effects of oral supplementation with Saccharomyces cerevisiae fermentation products (SCFP; SmartCare and NutriTek; Diamond V, Cedar Rapids, IA) on immune function and bovine respiratory syncytial virus (BRSV) infection in preweaned dairy calves. Twenty-four Holstein × Angus, 1- to 2-d-old calves (38.46 ± 0.91 kg initial body weight [BW]) were assigned two treatment groups: control or SCFP treated, milk replacer with 1 g/d SCFP (SmartCare) and calf starter top-dressed with 5 g/d SCFP (NutriTek). The study consisted of one 31-d period. On days 19 to 21 of the supplementation period, calves were challenged via aerosol inoculation with BRSV strain 375. Calves were monitored twice daily for clinical signs, including rectal temperature, cough, nasal and ocular discharge, respiration effort, and lung auscultation. Calves were euthanized on day 10 postinfection (days 29 to 31 of the supplementation period) to evaluate gross lung pathology and pathogen load. Supplementation with SCFP did not affect BW (P = 0.762) or average daily gain (P = 0.750), percentages of circulating white blood cells (P < 0.05), phagocytic (P = 0.427 for neutrophils and P = 0.460 for monocytes) or respiratory burst (P = 0.119 for neutrophils and P = 0.414 for monocytes) activity by circulating leukocytes either before or following BRSV infection, or serum cortisol concentrations (P = 0.321) after BRSV infection. Calves receiving SCFP had reduced clinical disease scores compared with control calves (P = 0.030), reduced airway neutrophil recruitment (P < 0.002), reduced lung pathology (P = 0.031), and a reduced incidence of secondary bacterial infection. Calves receiving SCFP shed reduced virus compared with control calves (P = 0.049) and tended toward lower viral loads in the lungs (P = 0.051). Immune cells from the peripheral blood of SCFP-treated calves produced increased (P < 0.05) quantities of interleukin (IL)-6 and tumor necrosis factor-alpha in response to toll-like receptor stimulation, while cells from the bronchoalveolar lavage (BAL) of SCFP-treated calves secreted less (P < 0.05) proinflammatory cytokines in response to the same stimuli. Treatment with SCFP had no effect on virus-specific T cell responses in the blood but resulted in reduced (P = 0.045) virus-specific IL-17 secretion by T cells in the BAL. Supplementing with SCFP modulates both systemic and mucosal immune responses and may improve the outcome of an acute respiratory viral infection in preweaned dairy calves.

Molecular characterization of Brazilian wild-type strains of bovine respiratory syncytial virus reveals genetic diversity and a putative new subgroup of the virus

Background

Bovine orthopneumovirus, formerly known as bovine respiratory syncytial virus (BRSV), is frequently associated with bovine respiratory disease (BRD).

Aim

To perform the molecular characterization of the G and F proteins of Brazilian wild-type BRSV strains derived from bovine respiratory infections in both beef and dairy cattle.

Materials and Methods

Ten BRSV strains derived from a dairy heifer rearing unit (n = 3) in 2011 and steers of three other feedlots (n = 7) in 2014 and 2015 were analyzed. For the BRSV G and F partial gene amplifications, RT-nested-PCR assays were performed with sequencing in both directions with forward and reverse primers used.

Results

The G gene-based analysis revealed that two strains were highly similar to the BRSV sequences representative of subgroup III, including the Bayovac vaccine strain. However, the remaining seven Brazilian BRSV strains were diverse when compared with strains representative of the BRSV I to VIII subgroups. The central hydrophobic region of the Brazilian BRSV G gene showed the replacement of conserved cysteines and other residues of importance to antibody reactivity. The deduced F gene amino acid sequences from the Brazilian BRSV strains showed changes that were absent in the representative sequences of the known subgroups. Viral isolation on the nasopharyngeal swab suspensions failed to isolate BRSV.

Conclusion

Results suggest that these strains represent a putative new subgroup of BRSV with mutations observed in the immunodominant region of the G protein. However, further studies on these Brazilian BRSV strains should be performed to establish their pathogenic potential.

Experimental challenge with bovine respiratory syncytial virus in dairy calves: bronchial lymph node transcriptome response

Bovine Respiratory Disease (BRD) is the leading cause of mortality in calves. The objective of this study was to examine the response of the host’s bronchial lymph node transcriptome to Bovine Respiratory Syncytial Virus (BRSV) in a controlled viral challenge. Holstein-Friesian calves were either inoculated with virus (10^3.5 TCID₅₀/ml × 15 ml) (n = 12) or mock challenged with phosphate buffered saline (n = 6). Clinical signs were scored daily and blood was collected for haematology counts, until euthanasia at day 7 post-challenge. RNA was extracted and sequenced (75 bp paired-end) from bronchial lymph nodes. Sequence reads were aligned to the UMD3.1 bovine reference genome and differential gene expression analysis was performed using EdgeR. There was a clear separation between BRSV challenged and control calves based on gene expression changes, despite an observed mild clinical manifestation of the disease. Therefore, measuring host gene expression levels may be beneficial for the diagnosis of subclinical BRD. There were 934 differentially expressed genes (DEG) (p < 0.05, FDR <0.1, fold change >2) between the BRSV challenged and control calves. Over-represented gene ontology terms, pathways and molecular functions, among the DEG, were associated with immune responses. The top enriched pathways included interferon signaling, granzyme B signaling and pathogen pattern recognition receptors, which are responsible for the cytotoxic responses necessary to eliminate the virus.

Effect of combined vaccination for Pasteurella multocida, Mannheimia haemolytica, and Histophilus somni to prevent respiratory diseases in young Japanese Black calves in the field

To evaluate the preventive effects of combined vaccination for Pasteurella multocida, Mannheimia haemolytica and Histophilus somni on respiratory diseases in Japanese Black calves, 295 calves at one farm were alternately assigned to two groups; 147 calves received the vaccine at 4 and 8 weeks of age (vaccination group), and the other 148 calves did not receive vaccine (control group). The incidences of respiratory diseases were 25.9 and 70.9% in the vaccination and control groups, respectively, and the odds ratio for comparison between the two groups was 0.143 (95% confidence interval: 0.086–0.238). Administration of the multiple vaccine to Japanese black calves might be one of effective factor for prevention of respiratory diseases.

Identification of an antilymphocyte transformation substance from Pasteurella multocida

Pasteurella multocida is one of the most important bacteria responsible for diseases of animals. Crude extracts from sonicated P. multocida strain Dainai-1, which is serotype A isolated from bovine pneumonia, were found to inhibit proliferation of mouse spleen cells stimulated with Con A. The crude extract was purified by cation and anion exchange chromatography and hydroxyapatite chromatography. Its molecular weight was 27 kDa by SDS-PAGE and it was named PM27. PM27 was found to inhibit proliferation of mouse spleen cells stimulated with Con A as effectively as did the crude extract; however, its activity was lost after heating to 100°C for 20 min. PM27 did not directly inhibit proliferation of HT-2 cells, which are an IL-2-dependent T cell line, nor did it modify IL-2 production by Con A-stimulated mouse spleen cells. The N-terminal amino acid sequence of PM27 was determined and BLAST analysis revealed its identity to uridine phosphorylase (UPase) from P. multocida. UPase gene from P. multocida Dainai-1 was cloned into expression vector pQE-60 in Escherichia coli XL-1 Blue. Recombinant UPase (rUPase) tagged with His at the C-terminal amino acid was purified with Ni affinity chromatography. rUPase was found to inhibit proliferation of mouse spleen cells stimulated with Con A; however, as was true for PM27, its activity was lost after heating to 100°C for 20 min. Thus, PM27/UPase purified from P. multocida has significant antiproliferative activity against Con A-stimulated mouse spleen cells and may be a virulence factor.

Bovine respiratory syncytial virus in experimentally exposed and rechallenged calves; viral shedding related to clinical signs and the potential for transmission

Background

Bovine respiratory syncytial virus (BRSV) is an important respiratory pathogen worldwide, detrimentally affecting the economy and animal welfare. To prevent and control BRSV infection, further knowledge on virus shedding and transmission potential in individual animals is required. This study aimed to detect viral RNA and infective virions during BRSV infection to evaluate duration of the transmission period and correlation with clinical signs of disease. The outcome of BRSV re-exposure on calves, their housing environment and effect of introduction of sentinel calves was also investigated.

A live animal experiment including 10 calves was conducted over 61 days. Initially, two calves were inoculated with a non-passaged BRSV field isolate. Two days later, six naïve calves (EG: Exposed group) were introduced for commingling and four weeks later, another two naïve calves (SG: Sentinel group) were introduced. Seven weeks after commingling, EG animals were re-inoculated. Clinical examination was performed daily. Nasal swabs were collected regularly and analysed for viral RNA by RT-ddPCR, while virus isolation was performed in cell culture. BRSV serology was performed with ELISA.

Results

All the EG calves seroconverted and showed clinical signs of respiratory disease. Viral RNA was detected from days 1–27 after exposure, while the infective virus was isolated on day 6 and 13. On day 19, all animals were seropositive and virus could not be isolated. Total clinical score for respiratory signs corresponded well with the shedding of viral RNA. The SG animals, introduced 27 days after exposure, remained negative for BRSV RNA and stayed seronegative throughout the study. Inoculation of the EG calves seven weeks after primary infection did not lead to new shedding of viral RNA or clinical signs of disease.

Conclusion

Viral RNA was detected in nasal swabs from the calves up to four weeks after exposure. The detection and amount of viral RNA corresponded well with the degree of respiratory signs. The calves were shedding infective virions for a considerable shorter period, and naïve calves introduced after four weeks were not infected. Infected calves were protected from reinfection for at least seven weeks. This knowledge is useful to prevent spread of BRSV.

Utility of the Neonatal Calf Model for Testing Vaccines and Intervention Strategies for Use against Human RSV Infection

Respiratory syncytial virus (RSV) is a significant cause of pediatric respiratory tract infections. It is estimated that two-thirds of infants are infected with RSV during the first year of life and it is one of the leading causes of death in this age group worldwide. Similarly, bovine RSV is a primary viral pathogen in cases of pneumonia in young calves and plays a significant role in bovine respiratory disease complex. Importantly, naturally occurring infection of calves with bovine RSV shares many features in common with human RSV infection. Herein, we update our current understanding of RSV infection in cattle, with particular focus on similarities between the calf and human infection, and the recent reports in which the neonatal calf has been employed for the development and testing of vaccines and therapeutics which may be applied to hRSV infection in humans.

Detection of Bovine Respiratory Syncytial Virus, Pasteurella Multocida, and Mannheimia Haemolytica by Immunohistochemical Method in Naturally-infected Cattle

Introduction

The aim of this study was to determine the predisposing effect of bovine respiratory syncytial virus (BRSV) on Pasteurella spp. infection in naturally-induced pneumonia in cattle by immunohistochemical labelling.

Material and Methods

Lungs of cattle slaughtered in the slaughterhouse were examined macroscopically, and 100 pneumonic samples were taken. The samples were fixed in 10% neutral formalin and embedded in paraffin by routine methods. Sections 5 μm in thickness were cut. The streptavidin-peroxidase method (ABC) was used to stain the sections for immuno-histochemical examination.

Results

BRSV antigens were found in the cytoplasm of epithelial cells of bronchi, bronchioles, and alveoles and within inflammatory cell debris and inflammatory exudate in bronchial lumens. Pasteurella spp. antigens were detected in the cytoplasm of the epithelial cells of bronchi and bronchioles, and in cells in the lumens of bronchi and bronchioles. Eleven cases were positive for only one pathogen (six for BRSV and five for Pasteurella spp.), while 35 cases were positive for 2 pathogens: BRSV plus P. multocida (n = 21) or M. haemolytica (n = 14).

Conclusion

The presence of high levels of BRSV in dual infections indicates that BSRV may be the main pneumonia-inducing agent and an important predisposing factor for the formation of Pasteurella spp. infections in cattle naturally afflicted with pneumonia.

Serological investigation of antibodies against respiratory viruses in calves from Brazilian family farming and their relation to clinical signs of bovine respiratory disease

ABSTRACT: Bovine respiratory disease (BRD) is responsible for economic losses in cattle production. Viruses are categorized as primary etiological agents. The aims of this study were to evaluate the presence of antibodies against bovine viral diarrhea virus (BVDV), bovine herpes virus type 1 (BoHV-1), and bovine respiratory syncytial virus (BRSV) in healthy and BRD calves from family farming in relation to clinical signs of BRD. Hundred and forty-five calves were randomly selected and physical examination was performed. Only 123 animals were classified as healthy and BRD calves. Antibodies were evaluated by virus neutralization test. Person’s Chi-square test and Fisher’s exact test were performed as univariate analysis. Binary Logistic Regression was applied as multivariate analysis. Variables with P<0.10 were considered statistically significant. Variables with 0.15<P<0.10 were considered as statistical tendencies. Antibodies against BoHV-1, BVDV, and BRSV were detected in 32%, 23% and 37% animals. Antibodies against both three viruses were detected in 26.8% of calves. The presence of antibodies against BRSV were associated to normal heart rates (P=0.018) and unilateral airflow (P=0.035). Tendency was observed to unilateral airflow (P=0.06) Statistical tendencies were observed to Ab-BoHV-1 and body temperature (P=0.119) and breathing pattern (P=0.123). The profile of antibodies against respiratory viruses in calves from Brazilian family farming was firstly described. The results confirmed the importance of some clinical signs to viral infection.

Exopolysaccharide Production and Biofilm Formation by Histophilus somni

The biofilm matrix of Histophilus somni is a complex architecture that differs substantially in structure between a pathogenic and commensal isolate examined. Overall, most pathogenic isolates produce more biofilm than commensal isolates. A major component of the biofilm is exopolysaccharide (EPS), which is also produced in greater quantity in the pathogenic isolate than in the commensal isolate studied. The EPS is composed of a D-mannan polymer, with occasional galactose residues present on side chains, similar in composition to that of yeast mannan. When grown in the presence of sialic acid, the biofilm EPS becomes sialylated and the amino sugars N-acetylglucosamine and N-acetylgalactosamine can be detected. In vitro biofilm formation follows a typical 4-stage growth curve, characterized by attachment, growth, maturation, and detachment. Following experimental challenge, formation of an H. somni biofilm has been demonstrated in cardiopulmonary tissue, often with Pasteurella multocida cohabitating the biofilm. A recently developed diagnostic test can detect antibodies to the EPS only in animals with systemic disease due to H. somni and is therefore capable of distinguishing between healthy animals colonized with H. somni and animals with systemic disease.

Bovine Gamma Delta T Cells Contribute to Exacerbated IL-17 Production in Response to Co-Infection with Bovine RSV and Mannheimia haemolytica

Human respiratory syncytial virus (HRSV) is a leading cause of severe lower respiratory tract infection in children under five years of age. IL-17 and Th17 responses are increased in children infected with HRSV and have been implicated in both protective and pathogenic roles during infection. Bovine RSV (BRSV) is genetically closely related to HRSV and is a leading cause of severe respiratory infections in young cattle. While BRSV infection in the calf parallels many aspects of human infection with HRSV, IL-17 and Th17 responses have not been studied in the bovine. Here we demonstrate that calves infected with BRSV express significant levels of IL-17, IL-21 and IL-22; and both CD4 T cells and γδ T cells contribute to this response. In addition to causing significant morbidity from uncomplicated infections, BRSV infection also contributes to the development of bovine respiratory disease complex (BRDC), a leading cause of morbidity in both beef and dairy cattle. BRDC is caused by a primary viral infection, followed by secondary bacterial pneumonia by pathogens such as Mannheimia haemolytica. Here, we demonstrate that in vivo infection with M. haemolytica results in increased expression of IL-17, IL-21 and IL-22. We have also developed an in vitro model of BRDC and show that co-infection of PBMC with BRSV followed by M. haemolytica leads to significantly exacerbated IL-17 production, which is primarily mediated by IL-17-producing γδ T cells. Together, our results demonstrate that calves, like humans, mount a robust IL-17 response during RSV infection; and suggest a previously unrecognized role for IL-17 and γδ T cells in the pathogenesis of BRDC.

γδ T cells and the immune response to respiratory syncytial virus infection

γδ T cells are a subset of nonconventional T cells that play a critical role in bridging the innate and adaptive arms of the immune system. γδ T cells are particularly abundant in ruminant species and may constitute up to 60% of the circulating lymphocyte pool in young cattle. The frequency of circulating γδ T cells is highest in neonatal calves and declines as the animal ages, suggesting these cells may be particularly important in the immune system of the very young. Bovine respiratory syncytial virus (BRSV) is a significant cause of respiratory infection in calves, and is most severe in animals under one year of age. BRSV is also a significant factor in the development of bovine respiratory disease complex (BRDC), the leading cause of morbidity and mortality in feedlot cattle. Human respiratory syncytial virus (RSV) is closely related to BRSV and a leading cause of lower respiratory tract infection in infants and children worldwide. BRSV infection in calves shares striking similarities with RSV infection in human infants. To date, there have been few studies defining the role of γδ T cells in the immune response to BRSV or RSV infection in animals or humans, respectively. However, emerging evidence suggests that γδ T cells may play a critical role in the early recognition of infection and in shaping the development of the adaptive immune response through inflammatory chemokine and cytokine production. Further, while it is clear that γδ T cells accumulate in the lungs during BRSV and RSV infection, their role in protection vs. immunopathology remains unclear. This review will summarize what is currently known about the role of γδ T cells in the immune response to BRSV and BRDC in cattle, and where appropriate, draw parallels to the role of γδ T cells in the human response to RSV infection.

Bovine respiratory syncytial virus outbreak reduced bulls' weight gain and feed conversion for eight months in a Norwegian beef herd

BACKGROUND

Cost-benefit evaluation of measures against respiratory disease in cattle requires accounting with the associated production losses. Investigations of naturally occurring respiratory infections in a herd setting are an opportunity for accurate estimates of the consequences. This article presents estimates based on individual monitoring of weight and concentrate intake of several hundred bulls previous to, during and after a respiratory infection outbreak with bovine respiratory syncytial virus (BRSV) as the main pathogen. The aim of the study was to analyse the association between exposure to BRSV, weight gain and feed conversion rate, quantify any change in these parameters, and estimate the duration of the change in production.

RESULTS

A comparison of growth curves for the bulls that were present during the outbreak revealed that bulls with severe clinical signs had a clear and consistent trend of poorer growth rate than those with milder or no signs. The weight/age-ratio was 0.04-0.10 lower in the severely affected bulls, and evident throughout the study period of 8 months. A comparison of growth rates between apparently healthy bulls being present during the outbreak and a comparable group of bulls exactly 1 year later (n = 377) showed a reduced growth rate of 111 g/day in the first group. The difference amounted to 23 extra days needed to reach the reference weight. Feed conversion was also reduced by 79 g weight gain/kilogram concentrate consumed in the outbreak year.

CONCLUSION

This study indicates significant negative effects on performance of animals that develop severe clinical signs in the acute stage, and that the growth and production is negatively affected many months after apparent recovery. In addition, the performance of apparently healthy animals that are exposed during an outbreak are severely negatively affected. The duration of this decrease in production in animals after recovery, or animals that have not shown disease at all, has not previously been documented. These losses will easily be underestimated, but contribute significantly to the costs for the producer. The findings emphasize the importance of BRSV infection for profitability and animal welfare in cattle husbandry. The study also illustrates that utilising intra-herd comparison of health and production parameters is a productive approach to estimate consequences of an outbreak.

Survey of management practices related to bovine respiratory disease in preweaned calves on California dairies

In the spring of 2013, a survey of California (CA) dairies was performed to characterize management practices related to bovine respiratory disease in preweaned calves, compare these practices across geographic regions of the state, and determine the principal components that explain the variability in management between herds. The questionnaire consisted of 53 questions divided into 6 sections to assess management practices affecting dairy calves from precalving to weaning. The questionnaire was mailed to 1,523 grade A licensed dairies in CA and 224 responses (14.7%) were collected. Survey response rates were similar over the 3 defined regions of CA: northern CA, northern San Joaquin Valley, and the greater southern CA region. The mean size of respondent herds was 1,423 milking cows. Most dairies reported raising preweaned calves on-site (59.7%). In 93.3% of dairies, preweaned calves were raised in some form of individual housing. Nonsaleable milk was the most frequent liquid diet fed to preweaned heifers (75.2%). Several important differences were identified between calf-raising practices in CA and practices reported in recent nationwide studies, including herd sizes, housing practices, and sources of milk fed to heifers. The differences between the CA and nationwide studies may be explained by differences in herd size. Regional differences within CA were also identified. Compared with the 2 other regions, northern CA dairies were found to have smaller herds, less Holstein cattle, calves remained with dams for longer periods of time after calving, were more likely to be certified organic dairies, and raised their own calves more often. Principal component analysis was performed and identified 11 components composed of 28 variables (questions) that explained 66.5% of the variability in the data. The identified components and questions will contribute to developing a risk assessment tool for bovine respiratory disease in preweaned dairy calves.

Detection of bovine respiratory syncytial virus infections in young dairy and beef cattle in Poland

BACKGROUND

Bovine respiratory syncytial virus (BRSV) is a major contributor to bovine respiratory disease complex in dairy and beef calves, especially during the first year of life. There is a lack of comprehensive information about the prevalence of infection in cattle herds in Poland as well as in European countries outside the European Union.

OBJECTIVE

The aim of this study was to estimate the prevalence of BRSV infections in young beef and dairy cattle in southeastern Poland, a region that has direct contact with non-EU countries. Animals & methods: Nasal swabs and sera (n = 120) were obtained from young cattle aged 6-12 months from 45 farms in eastern and southeastern Poland. BRSV antigen detection in the nasal swabs was carried out using a rapid immunomigration assay used in diagnosing human respiratory syncytial virus (hRSV) infections in humans, while antibodies to BRSV were detected in the sera by ELISA antibody detection.

RESULTS

The study confirmed the presence of BRSV infections in young cattle under 12 months of age from both dairy and beef herds. BRSV was detected in 27 of the 45 herds (60%) sampled.

CONCLUSIONS

Findings from this study indicate a high prevalence of BRSV infections in cattle in Poland, which may have a significant influence on health status and animal performance. The prevalence of infection is similar to that in other parts of Poland and other countries in Europe. Development of strategies to reduce BRSV infections is needed to improve health and productivity.

Respiratory syncytial virus infection in cattle

Bovine respiratory syncytial virus (RSV) is a cause of respiratory disease in cattle worldwide. It has an integral role in enzootic pneumonia in young dairy calves and summer pneumonia in nursing beef calves. Furthermore, bovine RSV infection can predispose calves to secondary bacterial infection by organisms such as Mannheimia haemolytica, Pasteurella multocida, and Histophilus somni, resulting in bovine respiratory disease complex, the most prevalent cause of morbidity and mortality among feedlot cattle. Even in cases where animals do not succumb to bovine respiratory disease complex, there can be long-term losses in production performance. This includes reductions in feed efficiency and rate of gain in the feedlot, as well as reproductive performance, milk production, and longevity in the breeding herd. As a result, economic costs to the cattle industry from bovine respiratory disease have been estimated to approach $1 billion annually due to death losses, reduced performance, and costs of vaccinations and treatment modalities. Human and bovine RSV are closely related viruses with similarities in histopathologic lesions and mechanisms of immune modulation induced following infection. Therefore, where appropriate, we provide comparisons between RSV infections in humans and cattle. This review article discusses key aspects of RSV infection of cattle, including epidemiology and strain variability, clinical signs and diagnosis, experimental infection, gross and microscopic lesions, innate and adaptive immune responses, and vaccination strategies.

Rapid Detection of Bovine Respiratory Syncytial Virus in Poland Using a Human Patient-Side Diagnostic Assay

Bovine respiratory syncytial virus (BRSV) plays a significant role in the etiopathogenesis of the respiratory syndrome in young cattle during their first year of life. Development of rapid and accurate BRSV diagnostic tools would aid in the appropriate control of this important pathogen. The objective of this study was to characterize infections induced by BRSV by means of rapid patient-side immunomigration assays used for diagnosis of human respiratory syncytial virus (hRSV) in humans. Nasal and tracheal swabs were obtained from healthy calves of various beef and dairy breeds - Holstein-Friesian, Simmental, Charolais, Belgian Blue and Limousin, between the ages of 5 and 12 months, from 26 farms. BRSV was identified using two rapid immunomigration assays, TruRSV® and Clearview® RSV, and compared with RT-PCR as a reference technique. BRSV was found in 73.1% of all the herds tested. High agreement with RT-PCR was obtained for TruRSV® (κ = 0.824), while in the case of the Clearview® RSV test, agreement with PCR was moderate (κ = 0.420). The results demonstrate that rapid patient-side immunomigration assays designed to detect hRSV can be used to accurately detect BRSV in field samples collected from cattle.

Neonatal calf infection with respiratory syncytial virus: drawing parallels to the disease in human infants

Respiratory syncytial virus (RSV) is the most common viral cause of childhood acute lower respiratory tract infections. It is estimated that RSV infections result in more than 100,000 deaths annually worldwide. Bovine RSV is a cause of enzootic pneumonia in young dairy calves and summer pneumonia in nursing beef calves. Furthermore, bovine RSV plays a significant role in bovine respiratory disease complex, the most prevalent cause of morbidity and mortality among feedlot cattle. Infection of calves with bovine RSV shares features in common with RSV infection in children, such as an age-dependent susceptibility. In addition, comparable microscopic lesions consisting of bronchiolar neutrophilic infiltrates, epithelial cell necrosis, and syncytial cell formation are observed. Further, our studies have shown an upregulation of pro-inflammatory mediators in RSV-infected calves, including IL-12p40 and CXCL8 (IL-8). This finding is consistent with increased levels of IL-8 observed in children with RSV bronchiolitis. Since rodents lack IL-8, neonatal calves can be useful for studies of IL-8 regulation in response to RSV infection. We have recently found that vitamin D in milk replacer diets can be manipulated to produce calves differing in circulating 25-hydroxyvitamin D3. The results to date indicate that although the vitamin D intracrine pathway is activated during RSV infection, pro-inflammatory mediators frequently inhibited by the vitamin D intacrine pathway in vitro are, in fact, upregulated or unaffected in lungs of infected calves. This review will summarize available data that provide parallels between bovine RSV infection in neonatal calves and human RSV in infants.

Genes controlling vaccine responses and disease resistance to respiratory viral pathogens in cattle

Farm animals remain at risk of endemic, exotic and newly emerging viruses. Vaccination is often promoted as the best possible solution, and yet for many pathogens, either there are no appropriate vaccines or those that are available are far from ideal. A complementary approach to disease control may be to identify genes and chromosomal regions that underlie genetic variation in disease resistance and response to vaccination. However, identification of the causal polymorphisms is not straightforward as it generally requires large numbers of animals with linked phenotypes and genotypes. Investigation of genes underlying complex traits such as resistance or response to viral pathogens requires several genetic approaches including candidate genes deduced from knowledge about the cellular pathways leading to protection or pathology, or unbiased whole genome scans using markers spread across the genome. Evidence for host genetic variation exists for a number of viral diseases in cattle including bovine respiratory disease and anecdotally, foot and mouth disease virus (FMDV). We immunised and vaccinated a cattle cross herd with a 40-mer peptide derived from FMDV and a vaccine against bovine respiratory syncytial virus (BRSV). Genetic variation has been quantified. A candidate gene approach has grouped high and low antibody and T cell responders by common motifs in the peptide binding pockets of the bovine major histocompatibility complex (BoLA) DRB3 gene. This suggests that vaccines with a minimal number of epitopes that are recognised by most cattle could be designed. Whole genome scans using microsatellite and single nucleotide polymorphism (SNP) markers has revealed many novel quantitative trait loci (QTL) and SNP markers controlling both humoral and cell-mediated immunity, some of which are in genes of known immunological relevance including the toll-like receptors (TLRs). The sequencing, assembly and annotation of livestock genomes and is continuing apace. In addition, provision of high-density SNP chips should make it possible to link phenotypes with genotypes in field populations without the need for structured populations or pedigree information. This will hopefully enable fine mapping of QTL and ultimate identification of the causal gene(s). The research could lead to selection of animals that are more resistant to disease and new ways to improve vaccine efficacy.

Quantitative trait loci associated with the immune response to a bovine respiratory syncytial virus vaccine

Infectious disease is an important problem for animal breeders, farmers and governments worldwide. One approach to reducing disease is to breed for resistance. This linkage study used a Charolais-Holstein F2 cattle cross population (n = 501) which was genotyped for 165 microsatellite markers (covering all autosomes) to search for associations with phenotypes for Bovine Respiratory Syncytial Virus (BRSV) specific total-IgG, IgG1 and IgG2 concentrations at several time-points pre- and post-BRSV vaccination. Regions of the bovine genome which influenced the immune response induced by BRSV vaccination were identified, as well as regions associated with the clearance of maternally derived BRSV specific antibodies. Significant positive correlations were detected within traits across time, with negative correlations between the pre- and post-vaccination time points. The whole genome scan identified 27 Quantitative Trait Loci (QTL) on 13 autosomes. Many QTL were associated with the Thymus Helper 1 linked IgG2 response, especially at week 2 following vaccination. However the most significant QTL, which reached 5% genome-wide significance, was on BTA 17 for IgG1, also 2 weeks following vaccination. All animals had declining maternally derived BRSV specific antibodies prior to vaccination and the levels of BRSV specific antibody prior to vaccination were found to be under polygenic control with several QTL detected.

Heifers from the same population (n = 195) were subsequently immunised with a 40-mer Foot-and-Mouth Disease Virus peptide (FMDV) in a previous publication. Several of these QTL associated with the FMDV traits had overlapping peak positions with QTL in the current study, including the QTL on BTA23 which included the bovine Major Histocompatibility Complex (BoLA), and QTL on BTA9 and BTA24, suggesting that the genes underlying these QTL may control responses to multiple antigens. These results lay the groundwork for future investigations to identify the genes underlying the variation in clearance of maternal antibody and response to vaccination.

Pathogenesis of respiratory syncytial virus

While affecting all age groups, respiratory syncytial virus (RSV) infections can be particularly severe in infants, who develop functionally distinct immune responses, as well as in immunocompromised individuals. The extent to which environmental, viral and host factors contribute to the pathogenesis of RSV varies considerably between infected individuals. A correlation between the level of virus replication and pathogenesis has been established, and several viral proteins, in particular NS1 and NS2, modulate the immune response. Host immunity clearly contributes to RSV pathogenesis, and a number of specific cell populations may be involved. Ultimately, whether the response induced by RSV is protective or pathogenic depends on a combination of host factors, young age being one of the most important ones.

Calf health from birth to weaning. III. housing and management of calf pneumonia

Calfhood diseases have a major impact on the economic viability of cattle operations. A three part review series has been developed focusing on calf health from birth to weaning. In this paper, the last of the three part series, we review disease prevention and management with particular reference to pneumonia, focusing primarily on the pre-weaned calf. Pneumonia in recently weaned suckler calves is also considered, where the key risk factors are related to the time of weaning. Weaning of the suckler calf is often combined with additional stressors including a change in nutrition, environmental change, transport and painful husbandry procedures (castration, dehorning). The reduction of the cumulative effects of these multiple stressors around the time of weaning together with vaccination programmes (preconditioning) can reduce subsequent morbidity and mortality in the feedlot. In most studies, calves housed individually and calves housed outdoors with shelter, are associated with decreased risk of disease. Even though it poses greater management challenges, successful group housing of calves is possible. Special emphasis should be given to equal age groups and to keeping groups stable once they are formed. The management of pneumonia in calves is reliant on a sound understanding of aetiology, relevant risk factors, and of effective approaches to diagnosis and treatment. Early signs of pneumonia include increased respiratory rate and fever, followed by depression. The single most important factor determining the success of therapy in calves with pneumonia is early onset of treatment, and subsequent adequate duration of treatment. The efficacy and economical viability of vaccination against respiratory disease in calves remains unclear.

Animal models of human respiratory syncytial virus disease

Infection with the human pneumovirus pathogen, respiratory syncytial virus (hRSV), causes a wide spectrum of respiratory disease, notably among infants and the elderly. Laboratory animal studies permit detailed experimental modeling of hRSV disease and are therefore indispensable in the search for novel therapies and preventative strategies. Present animal models include several target species for hRSV, including chimpanzees, cattle, sheep, cotton rats, and mice, as well as alternative animal pneumovirus models, such as bovine RSV and pneumonia virus of mice. These diverse animal models reproduce different features of hRSV disease, and their utilization should therefore be based on the scientific hypothesis under investigation. The purpose of this review is to summarize the strengths and limitations of each of these animal models. Our intent is to provide a resource for investigators and an impetus for future research.

Effect of abrupt weaning at housing on leukocyte distribution, functional activity of neutrophils, and acute phase protein response of beef calves

BACKGROUND

Sixteen, spring-born, single suckled, castrated male calves of Limousin x Holstein-Friesian and Simmental x Holstein-Friesian dams respectively, were used to investigate the effect of weaning on total leukocyte and differential counts, neutrophil functional activity, lymphocyte immunophenotypes, and acute phase protein response. Calves grazed with their dams until the end of the grazing season when they were housed in a slatted floor shed. On the day of housing, calves were assigned to a treatment, (i) abruptly weaned (W: n = 8) or (ii) non-weaned (controls) (C: n = 8). Weaned calves were housed in pens without their dams, whereas non-weaned (control) calves were housed with their dams. Blood was collected on day -7, 0 (housing), 2, 7, and 14 to determine total leukocyte and differential counts and concentration of fibrinogen and haptoglobin. Lymphocyte immunophenotypes were characterised using selected surface antigens (CD4+, CD8+, WC1+ (gammadelta T cells), MHC Class II+ lymphocytes), and the functional activities of neutrophils (surface expression of L-selectin (CD62L), phagocytic and oxidative burst activity) were investigated using flow cytometry.

RESULTS

Treatment x sampling time interactions (P < 0.05) were detected for total leukocyte and neutrophil counts, all lymphocyte subsets, mean fluorescence intensity of CD62L+ neutrophils, and percentage neutrophils performing phagocytosis. On d 2, total leukocyte and neutrophil count increased (P < 0.001), and percentage CD4+ and CD8+ lymphocytes, percentage phagocytic neutrophils, mean fluorescence intensity of CD62L+ neutrophils decreased (P < 0.05) in W compared with baseline (d 0), whereas they were unchanged (P > 0.05) in C. On d 2, percentage WC1+ lymphocytes decreased (P < 0.05), whereas percentage MHC class II+ lymphocytes increased (P < 0.05) in W and C, however the magnitude of change was greater in W than C. There were no treatment x sampling time interactions (P > 0.05) for monocyte, eosinophil, and basophil counts, percentage G1+ neutrophils, or percentage oxidative burst positive neutrophils.

CONCLUSIONS

Abrupt weaning resulted in increased neutrophil counts and impaired trafficking and phagocytic function. Together with the changes in lymphocyte subsets, the results suggest that there was a greater transitory reduction in immune function at housing in abruptly weaned than non-weaned beef calves.

Update on viral pathogenesis in BRD

Many viruses, including bovine herpesvirus-1 (BHV-1), bovine respiratory syncytial virus (BRSV), parainfluenzavirus-3 (PI3), bovine coronavirus, bovine viral diarrhea virus and bovine reovirus, have been etiologically associated with respiratory disease in cattle. This review focuses on the pathogenesis of BHV-1 and BRSV, two very different agents that primarily cause disease in the upper and lower respiratory tract, respectively.

Intranasal immunization of mice with a bovine respiratory syncytial virus vaccine induces superior immunity and protection compared to those by subcutaneous delivery or combinations of intranasal and subcutaneous prime-boost strategies

Bovine respiratory syncytial virus (BRSV) infects cells of the respiratory mucosa, so it is desirable to develop a vaccination strategy that induces mucosal immunity. To achieve this, various delivery routes were compared for formalin-inactivated (FI) BRSV formulated with CpG oligodeoxynucleotide (ODN) and polyphosphazene (PP). Intranasal delivery of the FI-BRSV formulation was superior to subcutaneous delivery in terms of antibody, cell-mediated, and mucosal immune responses, as well as reduction in virus replication after BRSV challenge. Although intranasal delivery of FI-BRSV also induced higher serum and lung antibody titers and gamma interferon (IFN-gamma) production in the lungs than intranasal-subcutaneous and/or subcutaneous-intranasal prime-boost strategies, no significant differences were observed in cell-mediated immune responses or virus replication in the lungs of challenged mice. Interleukin 5 (IL-5), eotaxin, and eosinophilia were enhanced after BRSV challenge in the lungs of subcutaneously immunized mice compared to unvaccinated mice, but not in the lungs of mice immunized intranasally or through combinations of the intranasal and subcutaneous routes. These results suggest that two intranasal immunizations with FI-BRSV formulated with CpG ODN and PP are effective and safe as an approach to induce systemic and mucosal responses, as well to reduce virus replication after BRSV challenge. Furthermore, intranasal-subcutaneous and subcutaneous-intranasal prime-boost strategies were also safe and almost as efficacious. In addition to the implications for the development of a protective BRSV vaccine for cattle, formulation with CpG ODN and PP could also prove important in the development of a mucosal vaccine that induces protective immunity against human RSV.

Bovine respiratory disease research (1983–2009)

Bovine respiratory disease (BRD) research has provided significant understanding of the disease over the past 26 years. Modern research tools that have been used include monoclonal antibodies, genomics, polymerase chain reaction, immunohistochemistry (IHC), DNA vaccines and viral vectors coding for immunogens. Emerging/reemerging viruses and new antigenic strains of viruses and bacteria have been identified. Methods of detection and the role for cattle persistently infected bovine viral diarrhea virus (BVDV) were identified; viral subunits, cellular components and bacterial products have been characterized. Product advances have included vaccines for bovine respiratory syncytial virus, Mannheimia haemolytica and Pasteurella multocida; the addition of BVDV2 to the existing vaccines and new antibiotics. The role of Mycoplasma spp., particularly Mycoplasma bovis in BRD, has been more extensively studied. Bovine immunology research has provided more specific information on immune responses, T cell subsets and cytokines. The molecular and genetic basis for viral–bacterial synergy in BRD has been described. Attempts have been made to document how prevention of BRD by proper vaccination and management prior to exposure to infectious agents can minimize disease and serve as economic incentives for certified health programs.

DNA vaccines in veterinary use

DNA vaccines represent a new frontier in vaccine technology. One important application of this technology is in the veterinary arena. DNA vaccines have already gained a foothold in certain fields of veterinary medicine. However, several important questions must be addressed when developing DNA vaccines for animals, including whether or not the vaccine is efficacious and cost effective compared with currently available options. Another important question to consider is how to apply this developing technology in a wide range of different situations, from the domestic pet to individual fish in fisheries with several thousand animals, to wildlife programs for disease control. In some cases, DNA vaccines represent an interesting option for vaccination, while in others, currently available options are sufficient. This review will examine a number of diseases of veterinary importance and the progress being made in DNA vaccine technology relevant to these diseases, and we compare these with the conventional treatment options available.

Pulmonary eosinophils and their role in immunopathologic responses to formalin-inactivated pneumonia virus of mice

Enhanced disease is the term used to describe the aberrant Th2-skewed responses to naturally acquired human respiratory syncytial virus (hRSV) infection observed in individuals vaccinated with formalin-inactivated viral Ags. Here we explore this paradigm with pneumonia virus of mice (PVM), a pathogen that faithfully reproduces features of severe hRSV infection in a rodent host. We demonstrate that PVM infection in mice vaccinated with formalin-inactivated Ags from PVM-infected cells (PVM Ags) yields Th2-skewed hypersensitivity, analogous to that observed in response to hRSV. Specifically, we detect elevated levels of IL-4, IL-5, IL-13, and eosinophils in bronchoalveolar lavage fluid of PVM-infected mice that were vaccinated with PVM Ags, but not among mice vaccinated with formalin-inactivated Ags from uninfected cells (control Ags). Interestingly, infection in PVM Ag-vaccinated mice was associated with a approximately 10-fold reduction in lung virus titer and protection against weight loss when compared with infected mice vaccinated with control Ags, despite the absence of serum-neutralizing Abs. Given recent findings documenting a role for eosinophils in promoting clearance of hRSV in vivo, we explored the role of eosinophils in altering the pathogenesis of disease with eosinophil-deficient mice. We found that eosinophil deficiency had no impact on virus titer in PVM Ag-vaccinated mice, nor on weight loss or levels of CCL11 (eotaxin-1), IFN-gamma, IL-5, or IL-13 in bronchoalveolar lavage fluid. However, levels of both IL-4 and CCL3 (macrophage inflammatory protein-1alpha) in bronchoalveolar lavage fluid were markedly diminished in PVM Ag-vaccinated, PVM-infected eosinophil-deficient mice when compared with wild-type controls.

Formulation of bovine respiratory syncytial virus fusion protein with CpG oligodeoxynucleotide, cationic host defence peptide and polyphosphazene enhances humoral and cellular responses and induces a protective type 1 immune response in mice

Respiratory syncytial virus (RSV) is the leading cause of serious respiratory tract disease in children and calves; however, RSV vaccine development has been slow due to early observations that formalin-inactivated vaccines induced Th2-type immune responses and led to disease enhancement upon subsequent exposure. Hence, there is a need for novel adjuvants that will promote a protective Th1-type or balanced immune response against RSV. CpG oligodeoxynucleotides (ODNs), indolicidin, and polyphosphazene were examined for their ability to enhance antigen-specific immune responses and influence the Th-bias when co-formulated with a recombinant truncated bovine RSV (BRSV) fusion protein (DeltaF). Mice immunized with DeltaF co-formulated with CpG ODN, indolicidin, and polyphosphazene (DeltaF/CpG/indol/PP) developed higher levels of DeltaF-specific serum IgG, IgG1 and IgG2a antibodies when compared with DeltaF alone, and displayed an increase in the frequency of gamma interferon-secreting cells and decreased interleukin (IL)-5 production by in vitro restimulated splenocytes, characteristic of a Th1 immune response. These results were observed in both C57BL/6 and BALB/c strains of mice. When evaluated in a BRSV challenge model, mice immunized with DeltaF/CpG/indol/PP developed significantly higher levels of BRSV-neutralizing serum antibodies than mice immunized with the DeltaF protein alone, and displayed significantly less pulmonary IL-4, IL-5, IL-13 and eotaxin and reduced eosinophilia after challenge. These results suggest that co-formulation of DeltaF with CpG ODN, host defence peptide and polyphosphazene may result in a safe and effective vaccine for the prevention of BRSV and may have implications for the development of novel human RSV vaccines.