African Swine Fever virus (ASFV) is a large double-enveloped DNA virus of the Asfarviridae family that causes a lethal hemorrhagic disease in domestic pigs and wild boars. Since 2007, a highly virulent genotype II strain has emerged and spread in Europe and South-East Asia, where millions of animals succumbed to the disease. Field- and laboratory-attenuated strains of ASFV cause highly variable clinical disease severity and survival, and mechanisms remain unclear. We hypothesized that the immunological and hygienic status of pigs is a determinant of ASF disease course. Here we compared the immunological profile at baseline and in response to ASFV infection in specific pathogen-free (SPF) and farm-raised Large White domestic pigs. At steady state, SPF pigs showed lower white blood cell counts and a lower basal inflammatory and antiviral transcriptomic profile compared to farm pigs associated with profound differences in gut microbiome composition. After inoculation with a highly virulent ASFV genotype II strain (Armenia 2008), severe clinical signs, viremia and pro-inflammatory cytokines appeared sooner in SPF pigs, indicating a reduced capacity to control early virus replication. In contrast, during infection with an attenuated field isolate (Estonia 2014), SPF pigs presented a milder and shorter clinical disease with full recovery, whereas farm pigs presented severe protracted disease with 50% lethality. Interestingly, farm pigs showed higher production of inflammatory cytokines, whereas SPF pigs produced more anti-inflammatory IL-1ra early after infection, and presented a stronger expansion of leukocytes in the recovery phase. Altogether, our data indicate that the hygiene-dependent innate immune status has a double-edge sword impact on immune responses in ASF pathogenesis. While the higher baseline innate immune activity helps the host in reducing initial virus replication, it promotes immunopathological cytokine responses, and delays lymphocyte proliferation after infection with an attenuated strain. Such effects should be considered for live vaccine development and vigilance.

Lung-resident (LR) mesenchymal stem and stromal cells (MSCs) are key elements of the alveolar niche and fundamental regulators of homeostasis and regeneration. We interrogated their function during virus-induced lung injury using the highly prevalent respiratory syncytial virus (RSV) which causes severe outcomes in infants. We applied complementary approaches with primary pediatric LR-MSCs and a state-of-the-art model of human RSV infection in lamb. Remarkably, RSV-infection of pediatric LR-MSCs led to a robust activation, characterized by a strong antiviral and pro-inflammatory phenotype combined with mediators related to T cell function. In line with this, following in vivo infection, RSV invades and activates LR-MSCs, resulting in the expansion of the pulmonary MSC pool. Moreover, the global transcriptional response of LR-MSCs appears to follow RSV disease, switching from an early antiviral signature to repair mechanisms including differentiation, tissue remodeling, and angiogenesis. These findings demonstrate the involvement of LR-MSCs during virus-mediated acute lung injury and may have therapeutic implications. AUTHOR SUMMARY This work identifies a novel function of lung-resident MSCs during virus-induced acute lung injury. These findings contribute to the understanding of host response and lung repair mechanisms during a highly prevalent clinical situation and may have therapeutic implications.

Rationale: Respiratory syncytial virus (RSV) is a major cause of lower respiratory tract infection in infancy, potentially aided by an inappropriate immune response. Sparse information is available for the distal lung, mostly because data arose from non-invasive samplings of peripheral blood and nasal aspirates. Objectives: To determine the neonatal immune response to RSV in the bronchoalveolar space and better understand why neonates are at greater risk of developing severe disease. Methods: We used the newborn lamb, a state-of-the-art translational model of human RSV infection, offering ease sampling and full accessibility to lower airways. Using a multiparameter flow cytometry assay, we evaluated the frequency and activation/maturation state of the major subsets of the developing T-cell compartment. Measurements and Main Results: The T-cell compartment of the healthy developing lung was very distinct to that seen in adults. We observed a high frequency of type 2 CD4+ (Th2) and CD8+ (Tc2) T-cells, both being a large source of IL-4, which declined progressively over time. Remarkably, RSV infection exacerbated this pro-type 2 environment, rather than inducing a type 2 response per se. Neonatal regulatory T-cell (Treg) suppressive functions occurred very early to dampen those Th2 and Tc2 responses, while γδ T-cells dropped and failed to produce IL-17. The disease severity was related to the magnitude of these T-cell responses. Conclusion: The atypical neonatal immune response to RSV consists of distinct T-cell subsets that tightly cooperate, namely a combined bronchoalveolar influx of Treg, Th2 and Tc2 cells, associated with a depletion of γδ T-cells.

The human respiratory syncytial virus (RSV) is a major cause of severe lower respiratory tract infections in infants, possibly due to the specific features of the immature neonatal pulmonary immune system. Using the newborn lamb, a classical model of human lung development and a state-of-the-art model of RSV infection, we aimed to explore the role of cell-mediated immunity in RSV disease during early life. Remarkably, in healthy conditions, the developing T cell compartment of the neonatal lung showed major differences to that seen in the mature adult lung. The most striking observation being a high baseline frequency of bronchoalveolar IL-4-producing CD4 and CD8 T cells, which declined progressively over developmental age. RSV infection exacerbated this pro-type 2 environment in the bronchoalveolar space, rather than inducing a type 2 response per se. Moreover, regulatory T cell suppressive functions occurred very early to dampen this pro-type 2 environment, rather than shutting them down afterwards, while γδ T cells dropped and failed to produce IL-17. Importantly, RSV disease severity was related to the magnitude of those unconventional bronchoalveolar T cell responses. These findings provide novel insights in the mechanisms of RSV immunopathogenesis in early life, and constitute a major step for the understanding of RSV disease severity. AUTHOR SUMMARY By using a state-of-the-art translational model with full accessibility to the small airways at defined early life periods, we provide an unpreceded characterization of the developing T cell compartment in the distal lungs of healthy and RSV-infected neonates. This process is highly dynamic and tightly regulated, characterized by colonizing T-cell subsets that synergize towards a narrow pro-tolerogenic immunological window. We believe our work constitutes a solid basis to clarify the age dependency of RSV immunopathogenesis, and should be considered in vaccine design, which remains challenging after five decades of effort.

Viral agents such as bovine respiratory syncytial virus (BRSV) and bovine parainfluenza virus 3 (BPIV-3) are considered primary infectious agents in bovine respiratory disease complex (BRDC). Information regarding the pathogenesis of BRDC is scarce, especially at an advanced chronicity stage, in addition to ongoing coinfection with other primary agents such as Mycoplasma bovis. Based on a retrospective review of histology slides from 104 autopsy cases, we classified cases according to type of pneumonia and chronicity. We performed immunohistochemistry (IHC) for BRSV, BPIV-3, and M. bovis as well as real-time PCR (rtPCR) for M. bovis on lung tissue of all 104 cases and correlated results with the morphologic type of pneumonia. Histomorphologically, 79 cases were classified as bronchopneumonia, 16 as bronchointerstitial pneumonia, and 9 as interstitial pneumonia. In 89 cases, at least 1 of the investigated agents was detected by IHC; 44 of these cases had a coinfection. BPIV-3 was the predominant agent present, as a single infection in 39 cases, and in coinfection with M. bovis in 39 cases. Comparing the detection methods for M. bovis, rtPCR was more specific and sensitive than IHC. The combination of both methods provided a good visual tool for assessing severity and distribution of M. bovis antigen within the tissue. Unlike BRSV, BPIV-3 and M. bovis persisted in chronic BRDC, suggesting ongoing impairment of defense mechanisms in the lung.

Summary In 2015, cholesterol deficiency (CD) was reported for the first time as a new recessive defect in Holstein cattle. After GWAS mapping and identification of a disease‐associated haplotype, a causative loss‐of‐function variant in APOB was identified. CD‐clinically affected APOB homozygotes showed poor development, intermittent diarrhea and hypocholesterolemia and, consequently, a limited life expectation. Herein, we present a collection of 18 cases clinically diagnosed as CD‐affected APOB heterozygotes. CD‐clinically affected heterozygotes show reduced cholesterol and triglyceride blood concentrations. The differences in total blood cholesterol and triglycerides between nine CD‐clinically affected and 36 non‐affected heterozygotes were significant. As only some APOB heterozygotes show the clinical CD phenotype, we assume that the penetrance is reduced in heterozygotes compared to the fully penetrant effect observed in homozygotes. We conclude that APOB‐associated CD represents most likely an incomplete dominant inherited metabolic disease with incomplete penetrance in heterozygotes.

INTRODUCTION In spring 2017, the first case of bovine anthrax in 20 years in Switzerland occurred in the canton of Jura. Carcasses of anthrax-deceased animals should not be opened due to the formation of highly resistant spores bearing the risk of environmental contamination and aerosolization. Nevertheless, in the course of this local outbreak, one sick cow from the affected farm, whose blood repeatedly tested negative for Bacillus anthracis, was necropsied after euthanasia under special biosafety precautions at the Institute of Animal Pathology, Vetsuisse-Faculty Bern. Necropsy revealed ventral edema, fetal death, necro-hemorrhagic placentitis and necrotizing iliac lymphadenitis. Bacillus anthracis was isolated only from placenta and altered lymph node. The biosafety measures taken during and after necropsy prevented a contamination of the necropsy environment, which was proven with bacteriological swabs. This case shows that anthrax may elicit unspecific symptoms mimicking other diseases, and veterinarians must be aware of these non-septicemic cases.

Background Cholesterol deficiency (CD), a newly identified autosomal recessive genetic defect in Holstein cattle, is associated with clinical signs of diarrhea, failure to thrive, and hypocholesterolemia. Hypothesis/Objectives The objective is to describe the clinicopathological phenotype of affected Holstein cattle homozygous for the causative apolipoprotein B gene (APOB) mutation. Animals Six Holstein cattle, 5 calves with a clinical history of chronic diarrhea, and 1 heifer with erosions in the buccal cavity and neurologic symptoms were admitted to the Clinic for Ruminants. Methods This case review included a full clinical examination, a complete blood count, blood chemistry, and measurements of cholesterol and triglycerides. The animals were euthanized and necropsied. A PCR‐based direct gene test was applied to determine the APOB genotype. Results All 6 animals were inbred, could be traced back to the sire Maughlin Storm, and were confirmed homozygous for the APOB mutation. The clinical phenotype included poor development, underweight, and intermittent diarrhea in the calves, and neurologic signs in the heifer included hypermetria and pacing. Hypocholesterolemia and low triglycerides concentrations were present in all animals. The pathological phenotype of all animals was steatorrhea with enterocytes of the small intestine containing intracytoplasmic lipid vacuoles. The peripheral nervous system of the heifer displayed degenerative changes. Conclusions and clinical importance Suspicion of CD in Holstein cattle is based on the presence of chronic diarrhea with no evidence of primary infections. Confirmation of the associated APOB gene mutation is needed. Additionally, the heifer demonstrated primarily signs of neurologic disease providing an unexpected phenotype of CD.

Summary Cholesterol deficiency, a new autosomal recessive inherited genetic defect in Holstein cattle, has been recently reported to have an influence on the rearing success of calves. The affected animals show unresponsive diarrhea accompanied by hypocholesterolemia and usually die within the first weeks or months of life. Here, we show that whole genome sequencing combined with the knowledge about the pedigree and inbreeding status of a livestock population facilitates the identification of the causative mutation. We resequenced the entire genomes of an affected calf and a healthy partially inbred male carrying one copy of the critical 2.24‐Mb chromosome 11 segment in its ancestral state and one copy of the same segment with the cholesterol deficiency mutation. We detected a single structural variant, homozygous in the affected case and heterozygous in the non‐affected carrier male. The genetic makeup of this key animal provides extremely strong support for the causality of this mutation. The mutation represents a 1.3kb insertion of a transposable LTR element (ERV2‐1) in the coding sequence of the APOB gene, which leads to truncated transcripts and aberrant splicing. This finding was further supported by RNA sequencing of the liver transcriptome of an affected calf. The encoded apolipoprotein B is an essential apolipoprotein on chylomicrons and low‐density lipoproteins, and therefore, the mutation represents a loss of function mutation similar to autosomal recessive inherited familial hypobetalipoproteinemia‐1 (FHBL1) in humans. Our findings provide a direct gene test to improve selection against this deleterious mutation in Holstein cattle.