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Bovine respiratory disease (BRD) is a major disease of young cattle whose etiology lies in complex interactions between pathogens and environmental and host factors. Despite a high frequency of codetection of respiratory pathogens in BRD, data on the molecular mechanisms and pathogenesis associated with viral and bacterial interactions are still limited. In this study, we investigated the effects of a coinfection with influenza D virus (IDV) and Mycoplasma bovis in cattle. Naive calves were infected by aerosol with a French IDV strain and an M. bovis strain. The combined infection shortened the incubation period, worsened the disease, and led to more severe macroscopic and microscopic lesions compared to these parameters in calves infected with only one pathogen. In addition, IDV promoted colonization of the lower respiratory tract (LRT) by M. bovis and increased white cell recruitment to the airway lumen. The transcriptomic analysis highlighted an upregulation of immune genes in the lungs of coinfected calves. The gamma interferon (IFN-gamma) gene was shown to be the gene most statistically overexpressed after coinfection at 2 days postinfection (dpi) and at least until 7 dpi, which correlated with the high level of lymphocytes in the LRT. Downregulation of the PACE4 and TMPRSS2 endoprotease genes was also highlighted, being a possible reason for the faster clearance of IDV in the lungs of coinfected animals. Taken together, our coinfection model with two respiratory pathogens that when present alone induce moderate clinical signs of disease was shown to increase the severity of the disease in young cattle and a strong transcriptomic innate immune response in the LRT, especially for IFN-gamma.IMPORTANCE Bovine respiratory disease (BRD) is among the most prevalent diseases in young cattle. BRD is due to complex interactions between viruses and/or bacteria, most of which have a moderate individual pathogenicity. In this study, we showed that coinfection with influenza D virus (IDV) and Mycoplasma bovis increased the severity of the respiratory disease in calves in comparison with IDV or M. bovis infection. IDV promoted M. bovis colonization of the lower respiratory tract and increased white cell recruitment to the airway lumen. The transcriptomic analysis highlighted an upregulation of immune genes in the lungs of coinfected calves. The IFN-gamma gene in particular was highly overexpressed after coinfection, correlated with the disease severity, immune response, and white cell recruitment in the lungs. In conclusion, we showed that IDV facilitates coinfections within the BRD complex by modulating the local innate immune response, providing new insights into the mechanisms involved in severe respiratory diseases.

Recent studies have identified a new genus of the Orthomyxoviridae family, Influenza D virus (IDV). This virus was shown to infect farm animals including swine and cattle, and to efficiently replicate and transmit in ferrets, the animal model of choice for transmission of influenza A virus to humans. This partnering grant on IDV addressed the need for capacity building at EU level to improve the EU's scientific assessment capacity and international competitiveness. We have promoted cross‐disciplinary cooperation between the partner institutes representing six Member States (BE, FR, IT, LU, NL and SE). We have shown that the available antigen and genome test systems allow reliable influenza D diagnostics in partners laboratories, while for a few of the applied antibody testing methods adjustments are recommended. Tools were developed to study virus‐host range, with a gain of knowledge on host and tissue tropism of IDV in farm animals but also in wild life and very preliminary data was generated on human tissues. Serological results in European cattle suggest that influenza D virus is enzootic. Virus diversity is still unfolding: new virus introductions were identified, as well as new reassortants whose differential clinical impact or cross‐protection levels are still poorly understood. Considering drivers of emergence, IDV was in the top five in comparison with 29 other diseases. The main risk factors of IDV in cattle are related to the animal density, presence of respiratory clinical signs in cattle and contact rates between animals. Simplified quantitative IDV risk assessment exposure model indicated a possible infection of human by IDV through aerosols in cattle farms. Further studies are warranted to fully assess the risk of IDV for both animal and Human health in Europe.

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International audience; Lipopolysaccharide (LPS) expressed on the surface of Gram-negative bacteria activates pro-inflammatory pathways, dys-regulates the function of endometrial cells and is a key player in the mechanisms involved in endometritis. This study aimed to investigate the effects of LPS on bovine endometrial epithelial cells (bEEC) from whole transcriptome with a special focus on genes involved in embryo-maternal interactions. Following in vitro culture, bEEC from three cows were exposed to 0, 2, and 8 μg/mL LPS for 24h. RNA samples extracted at 0 and 24 hours were analyzed by RNA sequencing (RNA-seq). At 24h, 2035 differentially expressed genes (DEGs) were identified between controls and samples treated with 2 μg/mL LPS. Gene ontology analysis showed that over-expressed DEGs were associated to immune response, response to stress and external stimuli, catalytic activity, and cell cycle. Genes associated with cell membrane and cell adhesion pathways were under-expressed. LPS induced changes in expression of specific genes related to embryo-maternal interactions including under-expression of eight members of the cadherin superfamily, over-expression of six members of the mucin family, and differential expression of a large set of genes binding the above molecules and of more than 20 transcripts coding for cytokines and their receptors. Type I interferon-τ dependent genes were also over-expressed. From a sub-set of 19 genes, (biological replicates of bEEC from cows taken at time 6 (n = 3), 24 (n = 6) and 48 hours (n = 3), and 2 technical replicates per sample) differential gene expression was confirmed by RT2-qPCR (r2 between fold changes at 24 hours by RT2-qPCR and RNA-seq = 0.97). These results indicate that LPS affects the function of bEEC in many ways by differential transcription, glycolytic metabolism and oxidative stress. Many transcriptomic signatures related to implantation and embryo maternal interactions were strongly affected by LPS. These results pave the way for further studies to investigate the duration of these changes and their possible impact on endometrial function and fertility.

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International audience; Concerns are growing over the impact of livestock farming on environment and public health. The livestock industry is faced with the double constraint of limiting its use of natural resources and antimicrobials while ensuring its economic sustainability. In this context, reliable methods are needed to evaluate the effect of the prevention of endemic animal diseases on the productivity of livestock production systems. In this study, an epidemiological and productivity model was used to link changes in Bovine Respiratory Disease (BRD) incidence with the productivity of the beef and dairy cattle sectors in France. Cattle production parameters significantly affected by BRD were selected through literature review. Previous field study results and national cattle performance estimates were used to infer growth performances, mortality rates and carcass quality in the cattle affected and not affected by BRD. A steady-state deterministic herd production model was used to predict the productivity of the dairy and beef sector and their defined compartments (breeding-fattening, feedlot young bulls, and feedlot veal) in case of BRD incidence reduction by 20%, 50% or 100%. Results suggested that BRD should be controlled at a priority in beef breeding farms as eradication of BRD in beef calves would increase the whole beef sector's productivity by 4.7-5.5% while eradication in other production stages would result in lower productivity gain in their respective sectors. However, the analysis performed at compartment level showed that, in both the beef and dairy sector, young bull and veal feedlot enterprises derive more economic benefits from BRD eradication for their own compartment (increase in productivity of 8.7-12.8% for beef young bulls) than the breeding farms (increase in productivity of 5.1-6% for beef calves), which may limit the investments in BRD control.

International audience; Lipopolysaccharide (LPS) is a component of outer membrane of Gram-negative bacteria involved in post-partum metritis and endometritis in cattle. LPS causes inflammation of the endometrium. Increased cell proliferation is part of the inflammatory process and has been reported in human epithelial and immune cells and from bovine Endometrial epithelial Cells (bEEC). In this study we investigated possible changes in gene expression in relation with the proliferative response of bEEC after challenge with E. coli-LPS. Following In vitro culture, bEEC from 3 cows were exposed to 0, 2, and 8 μg/ml LPS for 24 hrs. For each time point and LPS dosage, attached cells were counted then frozen. The variation of cells number over time was analyzed by ANOVA (SAS 9.1, proc GLM). RNA was extracted by using the All prep DNA/RNA Universal kit (Qiagen). Samples were analyzed by RNA sequencing performed in SciLife Laboratory in Uppsala and differentially expressed genes (DEG) searched by using Ensemble genes as reference. A significant increase in cell number was observed for cells treated with 8 μg/ml LPS (P≤ 0.001) whereas proliferation with 2μg/ml was more moderate. Major changes in gene expression were observed whatever the dosage used. 2035 DEG were found (Benjamini-Hochberg adjusted P value

International audience; Background: Bovine respiratory syncytial virus (BRSV) is a major cause of respiratory disease in cattle worldwide. Calves are particularly affected, even with low to moderate levels of BRSV-specific maternally derived antibodies (MDA). Available BRSV vaccines have suboptimal efficacy in calves with MDA, and published infection models in this target group are lacking in clinical expression. Here, we refine and characterize such a model. Results: In a first experiment, 2 groups of 3 calves with low levels of MDA were experimentally inoculated by inhalation of aerosolized BRSV, either: the Snook strain, passaged in gnotobiotic calves (BRSV-Snk), or isolate no. 9402022 Denmark, passaged in cell culture (BRSV-Dk). All calves developed clinical signs of respiratory disease and shed high titers of virus, but BRSV-Snk induced more severe disease, which was then reproduced in a second experiment in 5 calves with moderate levels of MDA. These 5 calves shed high titers of virus and developed severe clinical signs of disease and extensive macroscopic lung lesions (mean+/-SD, 48.3+/-12.0% of lung), with a pulmonary influx of inflammatory cells, characterized by interferon gamma secretion and a marked effect on lung function. Conclusions: We present a BRSV-infection model, with consistently high clinical expression in young calves with low to moderate levels of BRSV-specific MDA, that may prove useful in studies into disease pathogenesis, or evaluations of vaccines and antivirals. Additionally, refined tools to assess the outcome of BRSV infection are described, including passive measurement of lung function and a refined system to score clinical signs of disease. Using this cognate host calf model might also provide answers to elusive questions about human RSV (HRSV), a major cause of morbidity in children worldwide.

International audience; The development of safe and effective vaccines against both bovine and human respiratory syncytial viruses (BRSV, HRSV) to be used in the presence of RSV-specific maternally-derived antibodies (MDA) remains a high priority in human and veterinary medicine. Herein, we present safety and efficacy results from a virulent BRSV challenge of calves with MDA, which were immunized with one of three vaccine candidates that allow serological differentiation of infected from vaccinated animals (DIVA): an SH gene-deleted recombinant BRSV (Delta SHrBRSV), and two subunit (SU) formulations based on HRSV-P, -M2- 1, and -N recombinant proteins displaying BRSV-F and -G epitopes, adjuvanted by either oil emulsion (Montanide ISA71(VG), SUMont) or immunostimulating complex matrices (AbISCO-300, SUAbis). Whereas all control animals developed severe respiratory disease and shed high levels of virus following BRSV challenge, Delta SHrBRSV-immunized calves demonstrated almost complete clinical and virological protection five weeks after a single intranasal vaccination. Although mucosal vaccination with DSHrBRSV failed to induce a detectable immunological response, there was a rapid and strong anamnestic mucosal BRSV-specific IgA, virus neutralizing antibody and local T cell response following challenge with virulent BRSV. Calves immunized twice intramuscularly, three weeks apart with SUMont were also well protected two weeks after boost. The protection was not as pronounced as that in Delta SHrBRSV-immunized animals, but superior to those immunized twice subcutaneously three weeks apart with SUAbis. Antibody responses induced by the subunit vaccines were non-neutralizing and not directed against BRSV F or G proteins. When formulated as SUMont but not as SUAbis, the HRSV N, P and M2-1 proteins induced strong systemic cross-protective cell-mediated immune responses detectable already after priming. Delta SHrBRSV and SUMont are two promising DIVA-compatible vaccines, apparently inducing protection by different immune responses that were influenced by vaccine-composition, immunization route and regimen.

Session 3 : Antivirals & Vaccines; The incursion and circulation of more than nine different serotypes of Bluetongue virus (BTV) in central and northern Europe over the past fifteen years has resulted in decreased animal welfare and production losses. Vaccination is crucial for controlling BTV since conventional biosecurity measures have limited impact on vector-borne diseases. However, as current vaccines have no accepted characteristic allowing for the differentiation of infected from vaccinated animals (DIVA), the use of these products impairs sero-epidemiological surveillance and thus a quick return to BTV-free status as well as serological monitoring of vaccine efficacy in the field. Small ruminants show the most severe clinical signs following BTV infection, but cattle are the virus’s main amplifying host and when infected with certain BTV strains, such as BTV-8, they can also display clinical signs. However, protective bovine immune responses against BTV are poorly characterized and there is limited information available about the ability of commercial and experimental vaccines to induce clinical and virological protection against BTV infection in cattle. Our objective was to develop and evaluate the efficacy of a novel DIVA subunit vaccine against BTV-8 in cattle, that later may be developed into a multi-serotype vaccine. We produced recombinant VP2 of BTV-8 and NS1 and NS2 of BTV-2 and formulated the vaccine with the purified proteins and an ISCOM-based adjuvant (SubV). The DIVA characteristic of this vaccine is based on the detection of VP7 antibodies in infected animals, thereby enabling the detection of BTV infection of any serotype. In the first study, we evaluated the immunogenicity of SubV in comparison with a commercial inactivated vaccine against BTV-8. Cows were subcutaneously immunized twice at a 3-weeks interval with SubV (n=5), the commercial vaccine (n=5), or with placebo (n=5). Humoral and cell-mediated immune responses were monitored before each vaccination as well as at 3 and 6 weeks after the second immunization. Both vaccines induced similar serum neutralizing antibody titers and the specific IgG1 antibody responses detected against VP2, NS1, and NS2 were strongest in cows immunized with SubV. Furthermore, serotype cross-reactive humoral and cell-mediated immunological responses to BTV-8 were detected to NS2 and NS1 of BTV-2, respectively. In the second study, calves were immunized twice at a 3-weeks interval with either SubV (n=6) or placebo (n=6), then challenged with BTV-8 three weeks later in a Biosecurity level 3 facility. Whereas controls developed strong viremia and clinical signs of Bluetongue disease including fever, mucosal congestion, and stiffness, vaccinated calves did not show any of these signs and were strongly protected against BTV infection. Preliminary data indicate that vaccinated animals developed very strong serum neutralizing antibody responses following vaccination. Humoral and cellular immunological analyses are ongoing and clinical, virological, and immunological results of both studies will be presented during the meeting. Taken together, these data indicate that our novel subunit DIVA vaccine composed of only three BTV proteins is very effective against BTV-8 infection in cattle, and will also enable serological monitoring of any BTV serotype in circulation in vaccinated populations. Furthermore, the serotype cross-reactivity of NS1 and NS2 suggests that this vaccine may be expanded in the future to target multiple BTV serotypes through the addition of purified recombinant VP2 of other serotypes.