Breakthrough infections by SARS-CoV-2 variants boost cross-reactive hybrid immune responses in mRNA-vaccinated Golden Syrian hamsters.

Hybrid immunity (vaccination + natural infection) to SARS-CoV-2 provides superior protection to re-infection. We performed immune profiling studies during breakthrough infections in mRNA-vaccinated hamsters to evaluate hybrid immunity induction. The mRNA vaccine, BNT162b2, was dosed to induce binding antibody titers against ancestral spike, but inefficient serum virus neutralization of ancestral SARS-CoV-2 or variants of concern (VoCs). Vaccination reduced morbidity and controlled lung virus titers for ancestral virus and Alpha but allowed breakthrough infections in Beta, Delta and Mu-challenged hamsters. Vaccination primed for T cell responses that were boosted by infection. Infection back-boosted neutralizing antibody responses against ancestral virus and VoCs. Hybrid immunity resulted in more cross-reactive sera, reflected by smaller antigenic cartography distances. Transcriptomics post-infection reflects both vaccination status and disease course and suggests a role for interstitial macrophages in vaccine-mediated protection. Therefore, protection by vaccination, even in the absence of high titers of neutralizing antibodies in the serum, correlates with recall of broadly reactive B- and T-cell responses.

Enhancing the one health initiative by using whole genome sequencing to monitor antimicrobial resistance of animal pathogens: Vet-LIRN collaborative project with veterinary diagnostic laboratories in United States and Canada.

BACKGROUND: Antimicrobial resistance (AMR) of bacterial pathogens is an emerging public health threat. This threat extends to pets as it also compromises our ability to treat their infections. Surveillance programs in the United States have traditionally focused on collecting data from food animals, foods, and people. The Veterinary Laboratory Investigation and Response Network (Vet-LIRN), a national network of 45 veterinary diagnostic laboratories, tested the antimicrobial susceptibility of clinically relevant bacterial isolates from animals, with companion animal species represented for the first time in a monitoring program. During 2017, we systematically collected and tested 1968 isolates. To identify genetic determinants associated with AMR and the potential genetic relatedness of animal and human strains, whole genome sequencing (WGS) was performed on 192 isolates: 69 Salmonella enterica (all animal sources), 63 Escherichia coli (dogs), and 60 Staphylococcus pseudintermedius (dogs). RESULTS: We found that most Salmonella isolates (46/69, 67%) had no known resistance genes. Several isolates from both food and companion animals, however, showed genetic relatedness to isolates from humans. For pathogenic E. coli, no resistance genes were identified in 60% (38/63) of the isolates. Diverse resistance patterns were observed, and one of the isolates had predicted resistance to fluoroquinolones and cephalosporins, important antibiotics in human and veterinary medicine. For S. pseudintermedius, we observed a bimodal distribution of resistance genes, with some isolates having a diverse array of resistance mechanisms, including the mecA gene (19/60, 32%). CONCLUSION: The findings from this study highlight the critical importance of veterinary diagnostic laboratory data as part of any national antimicrobial resistance surveillance program. The finding of some highly resistant bacteria from companion animals, and the observation of isolates related to those isolated from humans demonstrates the public health significance of incorporating companion animal data into surveillance systems. Vet-LIRN will continue to build the infrastructure to collect the data necessary to perform surveillance of resistant bacteria as part of fulfilling its mission to advance human and animal health. A One Health approach to AMR surveillance programs is crucial and must include data from humans, animals, and environmental sources to be effective.

Temporal Release, Paracrine and Endocrine Actions of Ovine Conceptus-Derived Interferon-Tau During Early Pregnancy.

The antiviral activity of interferon (IFN) increases in uterine vein serum (UVS) during early pregnancy in sheep. This antiviral activity in UVS collected on Day 15 of pregnancy is blocked by anti-IFN-tau (anti-IFNT) antibodies. Conceptus-derived IFNT was hypothesized to induce IFN-stimulated gene (ISG) expression in endometrium and extrauterine tissues during pregnancy. To test this hypothesis, blood was collected from ewes on Days 12-16 of the estrous cycle or pregnancy. Serum progesterone was >1.7 ng/ml in pregnant (P) and nonpregnant (NP) ewes until Day 13, then declined to <0.6 ng/ml by Day 15 in NP ewes. A validated IFNT radioimmunoassay detected IFNT in uterine flushings (UFs) on Days 13-16 and in UVS on Days 15-16 of pregnancy. IFNT detection in UF correlated with paracrine induction of ISGs in the endometrium and occurred prior to the inhibition of estrogen receptor 1 and oxytocin receptor expression in uterine epithelia on Day 14 of pregnancy. Induction of ISG mRNAs in corpus luteum (CL) and liver tissue occurred by Day 14 and in peripheral blood mononuclear cells by Day 15 in P ewes. Expression of mRNAs for IFN signal transducers and ISGs were greater in the CL of P than that of NP ewes on Day 14. It is concluded that: 1) paracrine actions of IFNT coincide with detection of IFNT in UF; 2) endocrine action of IFNT ensues through induction of ISGs in peripheral tissues; and 3) IFNT can be detected in UVS, but not until Days 15-16 of pregnancy, which may be limited by the sensitivity of the IFNT radioimmunoassay.

Imaging diagnosis: Multiple cartilaginous exostoses and calcinosis circumscripta occurring simultaneously in the cervical spine of a dog.

An 8-month-old female Saint Bernard dog was presented with gait abnormalities consistent with a left-lateralizing cervical myelopathy. Imaging revealed a large, irregular soft tissue and mineral mass at the level of C1 and C2. The lesion was successfully excised, and histopathology was performed, revealing evidence of both multiple cartilaginous exostoses and calcinosis circumscripta. To the authors' knowledge, this is the first report comparing features using magnetic resonance imaging, computed tomography, and radiography. Additionally, multiple cartilaginous exostoses have not previously been reported to occur in combination with calcinosis circumscripta.

Colonic gastrointestinal stromal tumor resulting in recurrent colic and hematochezia in a warmblood gelding.

A 14-year-old Trakehner gelding was evaluated for recurrent colic, with episodes occurring over 1 year. Signs were consistent with intermittent ascending colon obstruction and hematochezia. Necropsy examination revealed an ulcerated mass extending into the lumen of the right dorsal ascending colon. Gross and histologic appearance and immunoreactivity to c-kit (CD117), desmin, vimentin, and smooth muscle actin, were consistent with a diagnosis of gastrointestinal stromal tumor.

Tumeur ventrale gastro-intestinale du côlon produisant des coliques et de l'hématochézie et des coliques récurrentes chez un hongre à sang chaud. Un hongre Trakehner âgé de 14 ans a été évalué pour des coliques récurrentes et les épisodes duraient depuis 1 an. Les signes étaient conformes à une obstruction intermittente du côlon ascendant et à l'hématochézie. La nécropsie a révélé une masse ulcéreuse s'étendant dans la lumière du côlon ascendant dorsal droit. L'apparence brute et histologique et l'immunoréactivité à c-kit (CD117), à la desmine, à la vimentine et à l'actine des muscles lisses étaient conformes au diagnostic de tumeur ventrale gastro-intestinale.(Traduit par Isabelle Vallières).

Comparative evaluation of assay performance for SARS-CoV-2 detection in animal oral samples, lung homogenates, and phosphate-buffered saline using the TaqPath COVID-19 Combo kit.

A One Health approach has been key to monitoring the COVID-19 pandemic, as human and veterinary medical professionals jointly met the demands for an extraordinary testing effort for SARS-CoV-2. Veterinary diagnostic laboratories continue to monitor SARS-CoV-2 infection in animals, furthering the understanding of zoonotic transmission dynamics between humans and animals. A RT-PCR assay is a primary animal screening tool established within validation and verification guidelines provided by the American Association of Veterinary Laboratory Diagnosticians (AAVLD), World Organisation for Animal Health (WOAH), and the U.S. Food and Drug Administration (FDA). However, differences in sample matrices, RNA extraction methods, instrument platforms, gene targets, and cutoff values may affect test outcomes. Therefore, targeted validation for a new sample matrix used in any PCR assay is critical. We evaluated a COVID-19 assay for the detection of SARS-CoV-2 in feline and canine lung homogenates and oral swab samples. We used the commercial Applied Biosystems MagMAX Viral/Pathogen II (MVP II) nucleic acid isolation kit and TaqPath COVID-19 Combo kit, which are validated for a variety of human samples, including nasopharyngeal and oropharyngeal swab samples. Our masked test showed a high detection rate and no false-positive or false-negative results, supporting sample extension to include feline oral swab samples. Our study is a prime example of One Health, illustrating how a COVID-19 assay designed for human testing can be adapted and used to detect SARS-CoV-2 in oral swab samples from cats and likely dogs, but not lung homogenates.

Pregnancy-associated genes contribute to antiluteolytic mechanisms in ovine corpus luteum.

The hypothesis that ovine luteal gene expression differs due to pregnancy status and day of estrous cycle was tested. RNA was isolated from corpora lutea (CL) on days 12 and 14 of the estrous cycle (NP) or pregnancy (P) and analyzed with the Affymetrix bovine microarray. RNA also was isolated from luteal cells on day 10 of estrous cycle that were cultured for 24 h with luteolytic hormones (OXT and PGF) and secretory products of the conceptus (IFNT and PGE2). Differential gene expression (>1.5-fold, P < 0.05) was confirmed using semiquantitative real-time PCR. Serum progesterone concentrations decreased from day 12 to day 15 in NP ewes (P < 0.05) reflecting luteolysis and remained >1.7 ng/ml in P ewes reflecting rescue of the CL. Early luteolysis (days 12-14) was associated with differential expression of 683 genes in the CL, including upregulation of SERPINE1 and THBS1. Pregnancy on day 12 (55 genes) and 14 (734 genes) also was associated with differential expression of genes in the CL, many of which were ISGs (i.e., ISG15, MX1) that were induced when culturing luteal cells with IFNT, but not PGE2. Finally, many genes, such as PTX3, IL6, VEGF, and LHR, were stabilized during pregnancy and downregulated during the estrous cycle and in response to culture of luteal cells with luteolytic hormones. In conclusion, pregnancy circumvents luteolytic pathways and activates or stabilizes genes associated with interferon, chemokine, cell adhesion, cytoskeletal, and angiogenic pathways in the CL.

Endocrine delivery of interferon tau protects the corpus luteum from prostaglandin F2 alpha-induced luteolysis in ewes.

Paracrine release of ovine interferon tau (oIFNT) from the conceptus alters release of endometrial prostaglandin F2 alpha (PGF) and prevents luteolysis. Endocrine release of oIFNT into the uterine vein occurs by Day 15 of pregnancy and may impart resistance of the corpus luteum (CL) to PGF. It was hypothesized that infusion of recombinant oIFNT (roIFNT) into the uterine or jugular veins on Day 10 of the estrous cycle would protect the CL against exogenous PGF-induced luteolysis. Osmotic pumps were surgically installed in 24 ewes to deliver bovine serum albumin (BSA; n = 12) or roIFNT (200 µg/day; n = 12) for 24 h into the uterine vein. Six ewes in each treatment group received a single injection of PGF (4 mg/58 kg body weight) 12 h after pump installation. In a second experiment, BSA or roIFNT was delivered at 20 or 200 µg/day into the uterine vein or 200 µg/day into the jugular vein for 72 h in 30 ewes. One half of these ewes received an injection of PGF 24 h after pump installation. Concentrations of progesterone in serum declined in BSA-treated ewes injected with PGF, but were sustained in all ewes infused with 20 µg/day of roIFNT into the uterine vein and 200 µg of roIFNT into the jugular vein followed 24 h later with injection of PGF. All concentrations of roIFNT and modes of delivery (uterine or jugular vein) increased luteal concentrations of IFN-stimulated gene (i.e., ISG15) mRNA. Infusion of 200 µg of IFNT over 24 h induced greater mRNA concentrations for cell survival genes, such as BCL2-like 1 (BCL2L1 or Bcl-xL), serine/threonine kinase (AKT), and X-linked inhibitor of apoptosis (XIAP) and decreased prostaglandin F receptor (PTGFR) mRNA concentrations, when compared to controls. It is concluded that endocrine delivery of roIFNT, regardless of route (uterine or jugular vein), effectively protects CL from the luteolytic actions of PGF by mechanisms that involve ISGs and stabilization of cell survival genes.

Prolonged survival in an aged Labrador retriever with a metastatic insulinoma.

This case report highlights an unusually prolonged, asymptomatic, disease-free interval in an aged male Labrador retriever that underwent partial pancreatectomy for a functionally active pancreatic insulinoma with histologically confirmed hepatic metastasis. The patient developed pancreatitis and nonseptic suppurative peritonitis 24 hr after surgical resection of the insulinoma and was managed medically until discharge. Three mo after surgery, the dog was diagnosed with exocrine pancreatic insufficiency (EPI) that was effectively managed with parenteral pancreatic enzymes. Due to normal glucose levels 3 mo postsurgically, liver samples from the initial surgery were resubmitted for immunohistochemistry. Results confirmed insulinoma metastasis with insulin expression. Ten mo postsurgically, the blood glucose was normal and serum insulin levels were slightly above the upper reference limit. The first hypoglycemic episode was documented 23 mo postoperatively, which was effectively managed with prednisone. The cause for the prolonged disease remission and survival was unknown, but was possibly a result of pancreatitis and peritonitis, partial spontaneous regression of metastatic lesions, or idiopathic. Despite life-threatening postoperative complications, this patient enjoyed a profoundly longer than expected survival. This case highlights the importance of removing the primary tumor (insulinoma) despite the presence of metastatic disease.

Angular limb deformity associated with TSPAN18, NRG3 and NOVA2 in Rambouillet rams.

Angular limb deformity (ALD) affects many species of livestock and companion animals. The mechanisms of ALD development are not well understood, but previous research suggests the involvement of genetic risk factors. A case-control genome-wide association study (GWAS) was conducted with 40 ALD-affected and 302 unaffected Rambouillet rams and 40,945 single nucleotide polymorphisms (SNPs). Forelimbs of 6 ALD-affected rams were examined and diagnosed with osteochondrosis. Genome-wide or chromosome-wide significant SNPs were positioned exonic, intronic or within the 3'UTR of genes TSPAN18, NRG3 and NOVA2, respectively. These genes have previously described roles related to angiogenesis and osteoblast, osteoclast and chondrocyte proliferation and differentiation, which suggests the possibility for their involvement in the pathogenesis of osteochondrosis. Functional consequences of SNPs were evaluated through transcription factor binding site analysis, which predicted binding sites for transcription factors of known importance to bone growth, including SOX6, SOX9 and RUNX2. The identification of genetic risk factors for ALD may help to improve animal welfare and production in Rambouillet, a breed known to be at risk for ALD development. This study proposes genes TSPAN18, NRG3 and NOVA2 as targets for further research towards understanding the etiology of ALD in Rambouillet sheep.

Breakthrough infections by SARS-CoV-2 variants boost cross-reactive hybrid immune responses in mRNA-vaccinated Golden Syrian Hamsters.

Hybrid immunity to SARS-CoV-2 provides superior protection to re-infection. We performed immune profiling studies during breakthrough infections in mRNA-vaccinated hamsters to evaluate hybrid immunity induction. mRNA vaccine, BNT162b2, was dosed to induce binding antibody titers against ancestral spike, but inefficient serum virus neutralization of ancestral SARS-CoV-2 or variants of concern (VoCs). Vaccination reduced morbidity and controlled lung virus titers for ancestral virus and Alpha but allowed breakthrough infections in Beta, Delta and Mu-challenged hamsters. Vaccination primed T cell responses that were boosted by infection. Infection back-boosted neutralizing antibody responses against ancestral virus and VoCs. Hybrid immunity resulted in more cross-reactive sera. Transcriptomics post-infection reflects both vaccination status and disease course and suggests a role for interstitial macrophages in vaccine-mediated protection. Therefore, protection by vaccination, even in the absence of high titers of neutralizing antibodies in the serum, correlates with recall of broadly reactive B- and T-cell responses.

Neuro-invasion by a 'Trojan Horse' strategy and vasculopathy during intrauterine flavivirus infection.

The central nervous system (CNS) is a major target of several important human and animal viral pathogens causing congenital infections. However, despite the importance of neuropathological outcomes, for humans in particular, the pathogenesis, including mode of neuro-invasion, remains unresolved for most congenital virus infections. Using a natural model of congenital infection with an RNA virus, bovine viral diarrhoea virus in pregnant cattle, we sought to delineate the timing and mode of virus neuro-invasion of and spread within the brain of foetuses following experimental respiratory tract infection of the dams at day 75 of pregnancy, a time of maximal risk of tissue pathology without foetal death. Virus antigen was first detected in the foetal brains 14 days postinfection of dams and was initially restricted to amoeboid microglial cells in the periventricular germinal layer. The appearance of these cells was preceded by or concurrent with vasculopathy in the same region. While the affected microvessels were negative for virus antigen, they expressed high levels of the type I interferon-stimulated protein ISG15 and eventually disappeared in parallel with the appearance of microcavitary lesions. Subsequently, the virus spread to neurons and other glial cells. Our findings suggest that the virus enters the CNS via infected microglial precursors, the amoeboid microglial cells, in a 'Trojan horse' mode of invasion and that the microcavitary lesions are associated with loss of periventricular microvasculature, perhaps as a consequence of high, unrestricted induction of interferon-regulated proteins.

Gross and histologic description of trematodosis in fetal and neonatal beef calves in North Dakota and Minnesota.

Hepatic trematodes, such as Fasciola hepatica and Fascioloides magna, have variable distribution throughout the United States. F. magna is endemic in the upper midwestern United States, and F. magna infections are diagnosed frequently in weaned calves and adult beef cattle at the North Dakota State University Veterinary Diagnostic Laboratory (NDSU-VDL). Rarely, liver fluke infestation has also been observed in much younger calves, including aborted fetuses. We describe here, in 2 fetal and 7 neonatal beef calves submitted to the NDSU-VDL between 2011 and 2020, parasitic migration tracts in livers, consisting of regionally extensive, random, linear tracts of fibrosis admixed with black porphyrin pigment, along with foci of necrosis and hemorrhage, and mixed inflammatory cells, which were caused presumptively by F. magna infection. Samples were not available from our 9 cases for PCR assay and sequencing, but we did confirm F. magna within liver samples collected from regional cattle in 2020 and 2021. Fetal and neonatal trematodosis was often concurrent with other common causes of fetal abortion and neonatal calf loss in our cases; however, based on the prepatent period of F. magna, fetal and neonatal beef calf trematode infestations occurred in utero.

Comparative Genomics of Listeria monocytogenes Isolates from Ruminant Listeriosis Cases in the Midwest United States.

Ruminants are a well-known reservoir for Listeria monocytogenes. In addition to asymptomatic carriage of the pathogen, ruminants can also acquire listeriosis and develop clinical manifestations in the form of neurologic or fetal infections, similar to those occurring in humans. Genomic characterization of ruminant listeriosis cases in Europe have identified lineage 1 and 2 strains associated with infection, as well as clonal complexes (CCs) that are commonly isolated from human cases of listeriosis; however, there is little information on the diversity of L. monocytogenes from ruminant listeriosis in the United States. In this study, we characterized and compared 73 L. monocytogenes isolates from ruminant listeriosis cases from the Midwest and the Upper Great Plains collected from 2015 to 2020. Using whole-genome sequence data, we classified the isolates and identified key virulence factors, stress-associated genes, and mobile genetic elements within our data set. Our isolates belonged to three different lineages: 31% to lineage 1, 53% to lineage 2, and 15% to lineage 3. Lineage 1 and 3 isolates were associated with neurologic infections, while lineage 2 showed a greater frequency of fetal infections. Additionally, the presence of mobile elements, virulence-associated genes, and stress and antimicrobial resistance genes was evaluated. These genetic elements are responsible for most of the subgroup-specific features and may play a key role in the spread of hypervirulent clones, including the spread of hypervirulent CC1 clone commonly associated with disease in humans, and may explain the increased frequency of certain clones in the area. IMPORTANCE Listeria monocytogenes affects humans and animals, causing encephalitis, septicemia, and abortions, among other clinical outcomes. Ruminants such as cattle, goats, and sheep are the main carriers contributing to the maintenance and dispersal of this pathogen in the farm environment. Contamination of food products from farms is of concern not only because many L. monocytogenes genotypes found there are associated with human listeriosis but also as a cause of significant economic losses when livestock and food products are affected. Ruminant listeriosis has been characterized extensively in Europe; however, there is limited information about the genetic diversity of these cases in the United States. Identification of subgroups with a greater ability to spread may facilitate surveillance and management of listeriosis and contribute to a better understanding of the genome diversity of this pathogen, providing insights into the molecular epidemiology of ruminant listeriosis in the region.

Equine dental and skeletal fluorosis induced by well water consumption.

Two horses that consumed well water with high fluoride content exhibited clinical signs of chronic dental and skeletal fluoride toxicosis and were later euthanized and autopsied. Both horses had degenerative disease of multiple joints and multiple dental defects. Elevated fluoride concentrations were found in bone and tooth samples of both horses, well water, and feed. Microscopically, abnormalities were noted in bone and tooth samples, and consisted mostly of foci of cement necrosis and hypercementosis. Horses exhibiting bilateral, highly symmetrical dental and/or skeletal lesions, with chronic lameness, should be evaluated for the possible presence of fluoride toxicosis.

Chronic cor pulmonale secondary to pulmonary atherosclerosis in an African Grey parrot.

CASE DESCRIPTION: A 20-year-old sexually intact female African Grey parrot (Psittacus erithacus) was evaluated to determine the cause of lethargy, hyporexia, weight loss, and persistent ascites of 21 days' duration. CLINICAL FINDINGS: Physical examination revealed a markedly distended abdomen and systolic heart murmur. Thoracic radiography revealed cardiomegaly and hepatomegaly. Doppler echocardiography revealed severe eccentric and concentric hypertrophy of the right ventricle with systolic dysfunction, moderate regurgitation through the right atrioventricular valve, a substantial increase in estimated systolic pulmonary arterial pressure, hepatic venous congestion, and coelomic effusion. A clinical diagnosis of chronic cor pulmonale was established. TREATMENT AND OUTCOME: The parrot was initially stabilized by use of coelomocentesis. During the next month, the parrot was treated by administration of furosemide, hydrochlorothiazide, spironolactone, benazepril, and pimobendan. The parrot appeared to be responding well to treatment but was found dead in its cage 35 days following initial examination. Postmortem examination revealed substantial atherosclerosis of the large pulmonary arteries, with lesions extending into the medium-size arteries. Pulmonary atherosclerosis was suspected as a cause of the severe pulmonary hypertension. CLINICAL RELEVANCE: Although atherosclerosis most commonly affects the systemic and coronary arteries of parrots, sclerotic changes within the pulmonary vasculature should be considered as a possible cause of pulmonary hypertension and as a differential diagnosis for right-sided congestive heart failure in psittacine species.

A Preliminary Evaluation of Ovine Bladder Mucosal Damage Associated With 2 Different Indwelling Urinary Catheters.

OBJECTIVE: To determine whether a new catheter design with a low-profile, open-ended rounded rather than pointed Foley catheter tip can reduce mucosal damage to the bladder of ewes. METHODS AND MATERIALS: Six ewes were randomly assigned to 1 of 2 indwelling urinary catheters-a 16 Fr Foley catheter or a 16 Fr open-tip CystoSure catheter. After 96 hours, all the animals were sacrificed and their bladder and urethra harvested for analysis. RESULTS: Image analysis of the bladder surfaces demonstrated a significant decrease in the percentage of bladder area covered by ulceration and inflammation in sheep with CystoSure catheters compared with Foley catheters (P < .002) as well as a trend toward less edema (P = .17). Macro-morphologic evaluations were confirmed with immunohistochemical markers of cell proliferation and inflammation. CONCLUSION: In this pilot study, we were able to demonstrate that a new catheter design with an open-ended rounded rather than pointed tip and a reduced balloon base-to-tip profile may reduce mucosal damage to the bladder of ewes. Based on the findings from this trial, we believe this new catheter design with its low-profile, rounded tip may reduce bladder mucosal injury, which is a risk factor for catheter-associated urinary tract infections.

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

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

Induction of interferon-gamma and downstream pathways during establishment of fetal persistent infection with bovine viral diarrhea virus.

Development of transplacental infection depends on the ability of the virus to cross the placenta and replicate within the fetus while counteracting maternal and fetal immune responses. Unfortunately, little is known about this complex process. Non-cytopathic (ncp) strains of bovine viral diarrhea virus (BVDV), a pestivirus in the Flaviviridae family, cause persistent infection in early gestational fetuses (<150 days; persistently infected, PI), but are cleared by immunocompetent animals and late gestational fetuses (>150 days; transiently infected, TI). Evasion of innate immune response and development of immunotolerance to ncp BVDV have been suggested as possible mechanisms for the establishment of the persistent infection. Previously we have observed a robust temporal induction of interferon (IFN) type I (innate immune response) and upregulation of IFN stimulated genes (ISGs) in BVDV TI fetuses. Modest chronic upregulation of ISGs in PI fetuses and calves reflects a stimulated innate immune response during persistent BVDV infection. We hypothesized that establishing persistent fetal BVDV infection is also accompanied by the induction of IFN-gamma (IFN-γ). The aims of the present study were to determine IFN-γ concentration in blood and amniotic fluid from control, TI and PI fetuses during BVDV infection and analyze induction of the IFN-γ downstream pathways in fetal lymphoid tissues. Two experiments with in vivo BVDV infections were completed. In Experiment 1, pregnant heifers were infected with ncp BVDV type 2 on day 75 or 175 of gestation or kept naïve to generate PI, TI and control fetuses, respectively. Fetuses were collected by Cesarean section on day 190. In Experiment 2, fetuses were collected on days 82, 89, 97, 192 and 245 following infection of pregnant heifers on day 75 of gestation. The results were consistent with the hypothesis that ncp BVDV infection induces IFN-γ secretion during acute infection in both TI and PI fetuses and that lymphoid tissues such as spleen, liver and thymus, serve both as possible sources of IFN-γ and target organs for its effects. Notably, induction of IFN-γ coincides with a decrease in BVDV RNA concentrations in PI fetal blood and tissues. This is the first report indicating the possible presence of an adaptive immune response in persistent BVDV infections, which may be contributing to the observed reduction of viremia in PI fetuses.

Effects of in utero pestivirus infection on bovine fetal bone geometry, biomechanical properties and composition.

Transplacental viral infection of the fetus can result in abnormal trabecular and cortical bone modeling in long bones through impaired bone resorption and formation. Although such infections are frequently associated with neonatal fractures in humans and animals, their effect on the biomechanical properties of the developing skeleton remain poorly understood. The goal of this study was to determine the effects of transplacental bovine viral diarrhea virus (BVDV) infection on the biomechanical properties of fetal femora. Pregnant heifers were inoculated intranasally with non-cytopathic BVDV or media alone on day 75 of gestation to produce persistently infected (PI) and control fetuses, respectively, which were then removed on days 192 and 245 of gestation. Histomorphometry, compositional analysis and 'four-point bending until failure' were performed on fetal femora. Altered cortical geometry largely accounted for differences in calculated elastic modulus (PI vs. control, and day 192 vs. day 245) and ultimate stress (day 192 vs. day 245). Fetal infection with BVDV did not significantly impair inherent biomechanical properties of bone but rather resulted in decreased periosteal apposition rates, manifested as smaller femoral mid-diaphyseal diameters. There were no differences between PI and control fetuses in cortical thickness ratio, ash density or calcium/phosphorous content; however, cortical thickness ratio decreased with fetal age. Thus even when cortical thickness ratios are similar, differences in mid-diaphyseal diameter affect the error associated with the calculation of stress and strain by classical beam theory equations.