Nutritional status impacts dengue virus infection in mice

Background

Dengue virus (DENV) is estimated to infect 390 million people annually. However, few host factors that alter disease severity are known. Malnutrition, defined as both over- and undernutrition, is a growing problem worldwide and has long been linked to dengue disease severity by epidemiological and anecdotal observations. Accordingly, we sought to establish a mouse model to assess the impact of nutritional status on DENV disease severity.

Results

Using transiently immunocompromised mice, we established a model of mild dengue disease with measurable viremia. We then applied it to study the effects of healthy weight, obese, and low-protein diets representing normal, over-, and undernutrition, respectively. Upon infection with DENV serotype 2, obese mice experienced more severe morbidity in the form of weight loss and thrombocytopenia compared to healthy weight groups. Additionally, obesity altered cytokine expression following DENV infection. Although low protein-fed mice did not lose significant weight after DENV2 infection, they also experienced a reduction in platelets as well as increased spleen pathology and viral titers.

Conclusions

Our results indicate that obese or undernourished mice incur greater disease severity after DENV infection. These studies establish a role for nutritional status in DENV disease severity.

Alveolar echinococcosis in a dog in the eastern United States

An 8-y-old Labrador Retriever was presented to a small animal practice in northern Virginia with a history of recent lethargy. Physical examination findings were unremarkable. Ultrasound revealed several large hepatic masses and multiple smaller masses involving the pancreas. Cytologic findings on fine-needle aspirates of the hepatic masses included inflammation and necrosis with eosinophilic, membranous oval structures consistent with cestode infection. Histopathologic findings for biopsies of these masses included extensive necrosis, inflammation, and PAS-positive hyaline-like membranous material interpreted as metacestode cyst wall. A PCR product was generated from aspirate material using primers specific for Echinococcus multilocularis. Subsequent sequence data were 100% homologous to E. multilocularis NADH dehydrogenase subunit I gene sequences. The dog received daily oral albendazole (10 mg/kg) treatment, but its condition deteriorated, and the dog was euthanized. The dog, born in Mississippi, was brought as a puppy to Virginia with no other travel history. To our knowledge, alveolar echinococcosis has not been reported previously in a dog in the United States; E. multilocularis infection was apparently acquired in the mid-Atlantic region of the United States.

Virus-like particle vaccine with B-cell epitope from porcine epidemic diarrhea virus (PEDV) incorporated into hepatitis B virus core capsid provides clinical alleviation against PEDV in neonatal piglets through lactogenic immunity

Porcine epidemic diarrhea virus (PEDV) has had a negative economic impact on the global swine industry for decades since its first emergence in the 1970s in Europe. In 2013, PEDV emerged for the first time in the United States, causing immense economic losses to the swine industry. Efforts to protect U.S. swine herds from PEDV infection and limit PEDV transmission through vaccination had only limited success so far. Following the previous success in our virus-like particle (VLP) based vaccine in mouse model, in this study we determined the immunogenicity and protective efficacy of a VLP-based vaccine containing B-cell epitope ⁷⁴⁸YSNIGVCK⁷⁵⁵ from the spike protein of PEDV incorporated into the hepatitis B virus core capsid (HBcAg), in a comprehensive pregnant gilt vaccination and piglet challenge model. The results showed that the vaccine was able to induce significantly higher virus neutralization response in gilt milk, and provide alleviation of clinical signs for piglets experimentally infected with PEDV. Piglets from pregnant gilt that was vaccinated with the VLP vaccine had faster recovery from the clinical disease, less small intestinal lesions, and higher survival rate at 10 days post-challenge (DPC).

Retinoic acid exerts disease stage-dependent and tissue-specific effects on pristane-induced lupus

We previously showed that all-trans-retinoic acid (tRA) exacerbated pre-existing autoimmunity in lupus; however, its effects before disease onset are unknown. Here, using a pristane-induced model, we show that tRA exerts tissue-specific effects when given at the initiation vs. continuation phase of lupus. Pre-pristane treatment with tRA aggravated glomerulonephritis through increasing renal expression of pro-fibrotic protein laminin β1, activating bone marrow CD11b- conventional dendritic cells, increasing the splenic CD4:CD8 ratio, and upregulating the interaction of ICAM-1 and LFA-1 that led to the infiltration of inflammatory cells to the spleen. Transcriptomic analysis revealed that prior to lupus induction, tRA significantly upregulated genes associated with cell differentiation, activation, and migration. Moreover, compared to pristane alone, tRA pre-treatment potentiated, whereas tRA post-treatment significantly suppressed, the renal expression of proinflammatory TNF-α, IL-1β, CCL2, and CCL3. While it may benefit the kidney, post-pristane treatment with tRA worsened the onset and severity of pristane-induced arthritis through promoting neutrophil and mononuclear cell infiltration into the joints. Together, these findings suggest that tRA supplementation regardless of the time of administration promotes chemokine-driven migration and tissue-specific infiltration of inflammatory cells, thereby exacerbating lupus-associated kidney or joint inflammation. Interestingly, both pre- and post-treatments with tRA modulated the gut microbiota in a similar fashion, suggesting a gut microbiota-independent mechanism by which tRA affects the initiation vs. continuation phase of lupus.

Retinoic Acid Exerts Disease Stage-Dependent Effects on Pristane-Induced Lupus

We previously showed that all-trans-retinoic acid (tRA), an active metabolite of vitamin A, exacerbated pre-existing autoimmunity in lupus; however, its effects before the development of autoimmunity are unknown. Here, using a pristane-induced model, we show that tRA exerts differential effects when given at the initiation vs. continuation phase of lupus. Unlike tRA treatment during active disease, pre-pristane treatment with tRA aggravated glomerulonephritis through increasing renal expression of pro-fibrotic protein laminin β1, activating bone marrow conventional dendritic cells (cDCs), and upregulating the interaction of ICAM-1 and LFA-1 in the spleen, indicating an active process of leukocyte activation and trafficking. Transcriptomic analysis revealed that prior to lupus induction, tRA significantly upregulated the expression of genes associated with cDC activation and migration. Post-pristane tRA treatment, on the other hand, did not significantly alter the severity of glomerulonephritis; rather, it exerted immunosuppressive functions of decreasing circulatory and renal deposition of autoantibodies as well as suppressing the renal expression of proinflammatory cytokines and chemokines. Together, these findings suggest that tRA differentially modulate lupus-associated kidney inflammation depending on the time of administration. Interestingly, both pre- and post-pristane treatments with tRA reversed pristane-induced leaky gut and modulated the gut microbiota in a similar fashion, suggesting a gut microbiota-independent mechanism by which tRA affects the initiation vs. continuation phase of lupus.

Abrogated AID Function Prolongs Survival and Diminishes Renal Pathology in the BXSB Mouse Model of Systemic Lupus Erythematosus

Almost a decade has passed since the approval of belimumab, an mAb directed against B lymphocyte stimulation and the first targeted therapy approved for systemic lupus erythematous (SLE) in over 50 y. Although well tolerated, the efficacy of belimumab remains limited and is not labeled for patients suffering from nephritis, the leading cause of patient mortality. We sought to explore alternative targets of autoreactive B lymphocytes through manipulation of affinity maturation. The BXSB/MpJ mouse, a well-established model of human SLE, develops elevated antinuclear Abs and immune complex-mediated nephritis along with other manifestations of SLE-like disease. To limit interfering with critical background genetics, we used CRISPR-Cas9 to disrupt activation-induced cytidine deaminase (AID; Aicda) directly in BXSB zygotes. Homozygous null mice demonstrated significantly prolonged survival compared with wild-type. Although mice continued to develop plasma cells, splenic follicular structure was restored, and renal pathology was reduced. Mice developed expanded germinal center B lymphocyte populations as in other models of AID deficiency as well as increased populations of CD73⁺ B lymphocytes. Treatment with the small molecule inhibitor of RAD51, 4,4'-diisothiocyano-2,2'-stilbenedisulfonic acid, resulted in minimal changes in disease markers in BXSB mice. The prolonged survival in AID-deficient BXSB mice appears attributed primarily to the reduced renal pathology, warranting further exploration, as current therapeutics targeting lupus nephritis are limited and, thus, in great demand.

Identification of the JAK-STAT pathway in canine splenic hemangiosarcoma, thyroid carcinoma, mast cell tumor, and anal sac adenocarcinoma

Dysregulation of the Janus Kinase (JAK) - Signal Transducer and Activator of Transcription (STAT) cellular signaling pathway has been associated with the development and progression of multiple human cancers. STAT3 has been reported to be present and constitutively active in a number of veterinary cancers, and few studies have reported mutations or activation of JAK1 or JAK2. Archived tissue samples from 54 client-owned dogs with histologically-diagnosed HSA, MCT, TC, or AGASACA were evaluated by immunohistochemical scoring of JAK1, JAK2, STAT3, and the phosphorylated counterparts pJAK1, pJAK2, and pSTAT3. IHC scoring was retrospectively analyzed with retrospectively-collected clinical parameters, including patient characteristics, metastasis, and survival. JAK1, pJAK1, JAK2, pJAK2, STAT3, and pSTAT3 were present in all tumor types evaluated. Significant correlations between JAK 1/2 or STAT3 and activated or downstream components were identified in all tumor types. Clinically, pSTAT3 was correlated with development of metastasis in dogs with MCT, while increased JAK1 expression or activation may impact survival in dogs with MCT or HSA. These findings provide a foundation to further investigate the JAK-STAT pathway in canine malignancies for additional therapeutic options.

Host nutritional status affects alphavirus virulence, transmission, and evolution

Malnourishment, specifically overweight/obesity and undernourishment, affects more than 2.5 billion people worldwide, with the number affected ever-increasing. Concurrently, emerging viral diseases, particularly those that are mosquito-borne, have spread dramatically in the past several decades, culminating in outbreaks of several viruses worldwide. Both forms of malnourishment are known to lead to an aberrant immune response, which can worsen disease outcomes and reduce vaccination efficacy for viral pathogens such as influenza and measles. Given the increasing rates of malnutrition and spread of arthropod-borne viruses (arboviruses), there is an urgent need to understand the role of host nutrition on the infection, virulence, and transmission of these viruses. To address this gap in knowledge, we infected lean, obese, and undernourished mice with arthritogenic arboviruses from the genus Alphavirus and assessed morbidity, virus replication, transmission, and evolution. Obesity and undernourishment did not consistently influence virus replication in the blood of infected animals except for reductions in virus in obese mice late in infection. However, morbidity was increased in obese mice under all conditions. Using Mayaro virus (MAYV) as a model arthritogenic alphavirus, we determined that both obese and undernourished mice transmit virus less efficiently to mosquitoes than control (lean) mice. In addition, viral genetic diversity and replicative fitness were reduced in virus isolated from obese compared to lean controls. Taken together, nutrition appears to alter the course of alphavirus infection and should be considered as a critical environmental factor during outbreaks.

Over- and undernutrition, collectively known as malnutrition, affect over 2.5 billion people worldwide. Associations between malnutrition and mosquito-borne virus infection and resulting disease have been identified in epidemiological studies but have not been explored in controlled studies. Here, we infect obese or undernourished mice with different arthritis inducing viruses in the genus Alphavirus and measure disease symptoms, viral replication, transmission, and evolution. We found that markers of disease, namely weight loss and footpad swelling, were increased in obese mice. We also found that replication differences between mice fed different diets were minimal except late in infection for obese mice when levels of virus dropped significantly. When mosquitoes were allowed to feed on mice fed different diets, we observed reduced infection and transmission rates, depending on the diet. Finally, we found reduced genetic diversity and replicative fitness of virus isolated from obese mice. This study provides insights into the influence of nutrition on alphavirus pathogenesis and evolution.

Theileria orientalis Ikeda Genotype in Cattle, Virginia, USA

Theileria orientalis Ikeda genotype is a parasite that causes a disease in cattle that results in major economic issues in Asia, New Zealand, and Australia. The parasite is transmitted by Haemaphysalis longicornis ticks, which have recently been reported in numerous states throughout the eastern United States. Concurrently, cattle in Virginia showed clinical signs consistent with a hemoprotozoan infection. We used amplicons specific for the major piroplasm surface protein and small subunit rDNA of piroplasms to test blood samples from the cattle by PCR. Bidirectional Sanger sequencing showed sequences with 100% identity with T. orientalis Ikeda genotype 2 sequences. We detected the parasite in 3 unrelated herds and from various animals sampled at 2 time points. Although other benign T. orientalis genotypes are endemic to the United States, detection of T. orientalis Ikeda genotype might represent a risk for the cattle industry in Virginia.

CD8+ lymphocytes but not B lymphocytes are required for protection against chronic hepatitis E virus infection in chickens

Hepatitis E is an important global disease, causing outbreaks of acute hepatitis in many developing countries and sporadic cases in industrialized countries. Hepatitis E virus (HEV) infection typically causes self-limiting acute hepatitis but can also progress to chronic disease in immunocompromised individuals. The immune response necessary for the prevention of chronic infection is T cell-dependent; however, the arm of cellular immunity responsible for this protection is not currently known. To investigate the contribution of humoral immunity in control of HEV infection and prevention of chronicity, we experimentally infected 20 wild-type (WT) and 18 immunoglobulin knockout (JH-KO) chickens with a chicken strain of HEV (avian HEV). Four weeks postinfection (wpi) with avian HEV, JH-KO chickens were unable to elicit anti-HEV antibody but had statistically significantly lower liver lesion scores than the WT chickens. At 16 wpi, viral RNA in fecal material and liver, and severe liver lesions were undetectable in both groups. To determine the role of cytotoxic lymphocytes in the prevention of chronicity, we infected 20 WT and 20 cyclosporine and CD8⁺ antibody-treated chickens with the same strain of avian HEV. The CD8 ⁺ lymphocyte-depleted, HEV-infected chickens had higher incidences of prolonged fecal viral shedding and statistically significantly higher liver lesion scores than the untreated, HEV-infected birds at 16 wpi. The results indicate that CD8 ⁺ lymphocytes are required for viral clearance and reduction of liver lesions in HEV infection while antibodies are not necessary for viral clearance but may contribute to the development of liver lesions in acute HEV infection.

Acute hindlimb lameness in a 6-month-old cat

CLINICAL PRESENTATION

A 6-month-old female spayed domestic shorthair cat was presented for investigation of acute right hindlimb lameness and paresis.

WHAT IS YOUR DIAGNOSIS?

Readers are encouraged to review the case history and consider what their diagnostic suspicion is. Also what is the preferred treatment for this injury? And what is the primary cause of this injury?

Sarcocystis neurona-Induced Myeloencephalitis Relapse Following Anticoccidial Treatment

Sarcocystis neurona is a ubiquitous parasite in the eastern United States, which is the principal causative agent in the neurologic disorder equine protozoal myeloencephalitis (EPM). While much is known about this protozoa's life cycle in its natural host, the opossum (Didelphis virginiana), little is known of how it acts in the aberrant equine host, which displays a high incidence of exposure with a relatively low rate of morbidity. For this study, we employed the popular interferon gamma knockout mouse model to determine the potential for recrudescence of S. neurona infection after treatment with the anticoccidial drug diclazuril. Mice were infected with S. neurona merozoites, and 7-days post-infection (DPI) they were treated with diclazuril for 30 or 60 days or not treated at all. All infected non-treated mice developed neurologic signs consistent with S. neurona infection within 30 DPI. All diclazuril-treated infected mice remained clinically normal while on treatment but developed neurologic signs within 60 days of treatment cessation. Histological examination of cerebella from all infected mice demonstrated characteristic lesions of S. neurona infection, regardless of treatment status. Cerebellar samples collected from infected treated mice, displaying neurologic signs, produced viable S. neurona in culture. However, cerebellar samples collected from infected and neurologically normal mice at the end of a 30-day treatment period did not produce viable S. neurona in culture. Analysis of the humoral immune response in infected mice showed that during treatment IgM antibody production decreased, suggesting the organism was sequestered from immune surveillance. The cessation of treatment and subsequent development of neurologic disease resulted in increased IgM antibody production, suggesting recognition by the immune system at that time. Based on the study results the authors propose that diclazuril was able to inhibit the replication and migration of S. neurona but not fully eliminate the parasite, suggesting recrudescence of infection after treatment is possible.

Diagnostic accuracy of stereotactic brain biopsy for intracranial neoplasia in dogs: Comparison of biopsy, surgical resection, and necropsy specimens

Background

Stereotactic brain biopsy (SBB) is a technique that allows for definitive diagnosis of brain lesions. Little information is available regarding the diagnostic utility of SBB in dogs with intracranial diseases.

Objective

To investigate the diagnostic accuracy (DA) of SBB in dogs with brain tumors.

Animals

Thirty‐one client‐owned dogs that underwent SBB followed by surgical resection or necropsy examinations.

Methods

Retrospective observational study. Two pathologists blinded to SBB and reference standard diagnoses reviewed histologic specimens and typed and graded tumors according to World Health Organization and revised canine glioma classification criteria. Agreement between tumor type and grade from SBB were compared to reference standards and assessed using kappa statistics. Patient and technical factors associated with agreement also were examined.

Results

Stereotactic brain biopsy specimens were obtained from 24 dogs with gliomas and 7 with meningiomas. Tumor type agreement between SBB and the reference standard was observed in 30/31 cases (κ = 0.95). Diagnostic concordance was perfect for meningiomas. Grade agreement among gliomas was observed in 18/23 cases (κ = 0.47). Stereotactic brain biopsy underrepresented the reference standard glioma grade in cases with disagreement. The DA of SBB was 81%, with agreement noted in 56/69 biopsy samples. Smaller tumors and fewer SBB specimens obtained were significantly associated with diagnostic discordance.

Conclusions and Clinical Importance

The DA of SBB readily allows for the diagnosis of common brain tumors in dogs. Although glioma grade discordance was frequent, diagnoses obtained from SBB are sufficient to currently inform therapeutic decisions. Multiple SBB specimens should be collected to maximize DA.

Mixed germ cell tumor composed of a tridermic testicular teratoma and seminoma in a rooster

A 5-y-old backyard Araucana-Americana rooster was presented to the regional diagnostic laboratory with a history of progressive lethargy and respiratory signs. Autopsy revealed a single large mass of testicular origin in the coelomic cavity, causing compression of other organs. Histologically, the mass was 1 neoplasm with mixed components of 2 different germ cell tumors, namely a teratoma composed of elements of all 3 primordial germ cell lines (ectoderm, mesoderm, and endoderm), and a seminoma consisting of round or polygonal cells arranged in sheets supported by a scant fibrovascular stroma. Teratomas and seminomas are both considered to be uncommon neoplasms in poultry medicine. A testicular teratoma is composed of mature embryonic tissue derived from at least 2 of the 3 germinal layers. Seminomas and teratomas both arise from the germinal epithelium of seminiferous tubules and are classified as germ cell tumors. This neoplastic mass thus is a rare case of a mixed germ cell tumor.

Dilated cardiomyopathy with endocardial fibroelastosis in a juvenile Pallas cat

Dilated cardiomyopathy (DCM) is a myocardial disease characterized by ventricular chamber dilation associated with systolic myocardial dysfunction in the absence of other cardiac lesions. DCM occasionally develops in conjunction with proliferation of fibroelastic fibers in the endocardium, producing endocardial fibroelastosis (EFE). Although early reports describe EFE as a primary disease, evidence now suggests that EFE may develop as a response to myocardial dysfunction. Echocardiographic evaluation of a 4-wk-old Pallas cat ( Otocolobus manul) with respiratory distress revealed enlargement of both atria, enlarged end-systolic left ventricular dimension, and left ventricular dilation. DCM was diagnosed, and the cat was euthanized, given the poor prognosis. Postmortem examination revealed pericardial effusion and biventricular and biatrial enlargement. The interventricular septum and free walls of ventricles were thin. Histologically, the endocardium of the left and right ventricles was diffusely thickened; Verhoeff-Van Gieson staining of the left ventricular endocardium revealed a moderate amount of endocardial accumulation of elastin and collagen. These fibers were more prominent in papillary muscles and around coronary blood vessels. Based on these findings, we diagnosed DCM with EFE. Cardiac diseases are rarely diagnosed in wild felids.

Human Breast-Milk Feeding Enhances the Humoral and Cell-Mediated Immune Response in Neonatal Piglets

Background

The benefits of breastfeeding infants are well characterized, including those on the immune system. However, determining the mechanism by which human breast milk (HBM) elicits effects on immune response requires investigation in an appropriate animal model.

Objective

The primary aim of this study was to develop a novel porcine model and to determine the differential effects of feeding HBM and a commercial milk formula (MF) on immune response and gastrointestinal microbial colonization in a controlled environment.

Methods

Male piglets were fed HBM (n = 26) or MF (n = 26) from day 2 through day 21. Piglets were vaccinated (n = 9/diet group) with cholera toxin and cholera toxin subunit B (CTB) and tetanus toxoid at 21 d or were fed placebo (n = 6/diet group) and then weaned to a standard solid diet at the age of 21 d. Humoral and cell-mediated immune responses were assessed from blood on days 35 and 48. Immune response was further examined from tissues, including mesenteric lymph nodes (MLNs), Peyer's patches (PPs), and spleen. The colonization of gut microbiota was characterized from feces on days 16 and 49.

Results

Serum antibody titers in piglets fed HBM were 4-fold higher (P < 0.05) to CTB and 3-fold higher (P < 0.05) to tetanus toxoid compared with piglets fed MF on day 48. Compared with MF, the numbers of immunoglobulin A antibody-producing cells to CTB were 13-fold higher (P < 0.05) in MLNs and 11-fold higher (P < 0.05) in PPs in the HBM diet group on day 51. In addition, significantly increased T cell proliferation was observed in the HBM group relative to the MF group. Furthermore, microbial diversity in the HBM group was lower (P < 0.05) than in the MF group.

Conclusions

This porcine model appears to be valid for studying the effects of early postnatal diet on immune responses and the gastrointestinal microbiome. Our results lay the groundwork for future studies defining the role of infant diet on microbiota and immune function.

Adrenocortical Challenge Response and Genomic Analyses in Scottish Terriers With Increased Alkaline Phosphate Activity

Scottish terriers (ST) frequently have increased serum alkaline phosphatase (ALP) of the steroid isoform. Many of these also have high serum concentrations of adrenal sex steroids. The study's objective was to determine the cause of increased sex steroids in ST with increased ALP. Adrenal gland suppression and stimulation were compared by low dose dexamethasone (LDDS), human chorionic gonadotropin (HCG) and adrenocorticotropic hormone (ACTH) response tests. Resting plasma pituitary hormones were measured. Steroidogenesis-related mRNA expression was evaluated in six ST with increased ALP, eight dogs of other breeds with pituitary-dependent hyperadrenocorticism (HAC), and seven normal dogs. The genome-wide association of single nucleotide polymorphisms (SNP) with ALP activity was evaluated in 168 ST. ALP (reference interval 8–70 U/L) was high in all ST (1,054 U/L) and HAC (985 U/L) dogs. All HAC dogs and 2/8 ST had increased cortisol post-ACTH administration. All ST and 2/7 Normal dogs had increased sex steroids post-ACTH. ST and Normal dogs had similar post-challenge adrenal steroid profiles following LDDS and HCG. Surprisingly, mRNA of hydroxysteroid 17-beta dehydrogenase 2 (HSD17B2) was lower in ST and Normal dogs than HAC. HSD17B2 facilities metabolism of sex steroids. A SNP region was identified on chromosome 5 in proximity to HSD17B2 that correlated with increased serum ALP. ST in this study with increased ALP had a normal pituitary-adrenal axis in relationship to glucocorticoids and luteinizing hormone. We speculate the identified SNP and HSD17B2 gene may have a role in the pathogenesis of elevated sex steroids and ALP in ST.

Evaluation of the pathogenicity of mammalian orthoreovirus type 3 (MRV3) in germ-free gnotobiotic pigs and of the efficacy of an inactivated vaccine against MRV3 infection in neonatal conventional piglets

A novel U.S. strain of mammalian orthoreovirus type 3 (MRV3) isolated from diarrheic pigs in 2015 was reportedly highly pathogenic in pigs. In this study, we first developed an inactivated MRV3 vaccine and determined its protective efficacy against MRV3 infection in conventional neonatal piglets. A pathogenicity study was also conducted in gnotobiotic pigs to further assess the pathogenicity of MRV3. To evaluate if piglets could be protected against MRV3 infection after immunization of pregnant sows with an inactivated MRV3 vaccine, pregnant sows were vaccinated with 2 or 3 doses of the vaccine or with PBS buffer. Four-day-old piglets born to vaccinated and unvaccinated sows were subsequently challenged with MRV3. The results showed that piglets born from vaccinated sows had lower levels of fecal viral RNA shedding at 1, 3, and 4 days post-challenge, suggesting that the inactivated MRV3 vaccine can reduce MRV3 replication. Surprisingly, although the conventional piglets were infected, they did not develop severe enteric disease as reported previously. Therefore, in an effort to further definitively assess the pathogenicity of MRV3, we experimentally infected gnotobiotic pigs, a more sensitive model for pathogenicity study, with the wild-type MRV3 virus. The infected gnotobiotic piglets all survived and exhibited only very mild diarrhea in some pigs. Taken together, the results indicate that the novel strain of MRV3 recently isolated in the United States infected but caused only very mild diarrhea in pigs, and that maternal immunity acquired from sows vaccinated with an inactivated vaccine can reduce MRV3 replication in neonatal pigs.

Effects of postmortem time and storage fluid on the material properties of bovine liver parenchyma in tension

In motor vehicle collisions (MVCs), liver injuries are one of the most frequently reported types of abdominal organ trauma. Although finite element models are utilized to evaluate the risk of sustaining an abdominal organ injury in MVCs, these models must be validated based on biomechanical data in order to accurately assess injury risk. Given that previous studies that have quantified the tensile failure properties of human liver parenchyma have been limited to testing at 48 h postmortem, it is currently unknown how the material properties change between time of death and 48 h postmortem. Therefore, the objective of this study was to quantify the effects of postmortem degradation on the tensile material properties of bovine liver parenchyma with increasing postmortem time when stored in DMEM or saline. A total of 148 uniaxial tension tests were successfully conducted on parenchyma samples of fourteen bovine livers acquired immediately after death. Liver tissue was submerged in DMEM or saline and kept cool during sample preparation and storage. Twelve livers were stored as large blocks of tissue, while two livers were stored as small blocks and slices. Tension tests were performed on multiple dog-bone samples from each liver at three time points: ~6 h, ~24 h, and ~48 h postmortem. The data were then analyzed using a Linear Mixed Effect Model to determine if there were significant changes in the failure stress, failure strain, and modulus with respect to postmortem time. The results of the current study showed that the failure strain of bovine liver parenchyma decreased significantly between 6 h and 48 h after death when stored as large blocks in saline and refrigerated. Conversely, neither the failure stress nor failure strain changed significantly with respect to postmortem time when stored as large blocks in DMEM. The modulus did not change significantly with respect to postmortem time for tissue stored as large blocks in either saline or DMEM. Cellular disruption increased with postmortem time for tissue stored as large blocks, with tissue stored in saline showing the greatest increase at each time point. In addition, preliminary results indicated that reducing the tissue storage size had a negative effect on the material properties and cellular architecture. Overall, this study illustrated that the effects of postmortem liver degradation varied with respect to the preservation fluid, storage time, and storage block size.

Dietary epicatechin improves survival and delays skeletal muscle degeneration in aged mice

We recently reported that epicatechin, a bioactive compound that occurs naturally in various common foods, promoted general health and survival of obese diabetic mice. It remains to be determined whether epicatechin extends health span and delays the process of aging. In the present study, epicatechin or its analogue epigallocatechin gallate (EGCG) (0.25% w/v in drinking water) was administered to 20-mo-old male C57BL mice fed a standard chow. The goal was to determine the antiaging effect. The results showed that supplementation with epicatechin for 37 wk strikingly increased the survival rate from 39 to 69%, whereas EGCG had no significant effect. Consistently, epicatechin improved physical activity, delayed degeneration of skeletal muscle (quadriceps), and shifted the profiles of the serum metabolites and skeletal muscle general mRNA expressions in aging mice toward the profiles observed in young mice. In particular, we found that dietary epicatechin significantly reversed age-altered mRNA and protein expressions of extracellular matrix and peroxisome proliferator–activated receptor pathways in skeletal muscle, and reversed the age-induced declines of the nicotinate and nicotinamide pathway both in serum and skeletal muscle. The present study provides evidence that epicatechin supplementation can exert an antiaging effect, including an increase in survival, an attenuation of the aging-related deterioration of skeletal muscles, and a protection against the aging-related decline in nicotinate and nicotinamide metabolism.—Si, H., Wang, X., Zhang, L., Parnell, L. D., Ahmed, B., LeRoith, T., Ansah, T.-A., Zhang, L., Li, J., Ordovás, J. M., Si, H., Liu, D., Lai, C.-Q. Dietary epicatechin improves survival and delays skeletal muscle degeneration in aged mice.

Biofilm formation and avian immune response following experimental acute and chronic avian cholera due to Pasteurella multocida

Pasteurella multocida is the causative agent of avian cholera, an important economic and ecological disease that can present as a peracute, acute, chronic, or asymptomatic infection. Acute avian cholera is associated with encapsulated P. multocida, while chronic and asymptomatic cases of avian cholera may be associated with capsule-deficient P. multocida isolates. We hypothesize that biofilm formation is also associated with chronic and asymptomatic avian cholera. Experimental infections of chickens with encapsulated, biofilm-deficient P. multocida strain X73, proficient biofilm forming P. multocida strain X73ΔhyaD, and proficient biofilm forming clinical strains 775 and 756 showed that virulence was inversely correlated with biofilm formation. Biofilm-proficient isolates induced chronic avian cholera in the chicken host. Histopathological analysis was used to show that biofilm-proficient isolates induced little inflammation in the lungs, heart, and liver, while biofilm-deficient isolates induced greater inflammation and induced the recruitment of heterophil granulocytes. Putative biofilm matrix material and exopolysaccharide was detected in pulmonary tissue of chickens diagnosed with chronic avian cholera using scanning electron microscopy and a fluorescently-tagged lectin, respectively, supporting a role for biofilm in chronic avian cholera. P. multocida induced Th1 and Th17 immune responses during acute and chronic avian cholera, as determined by quantitative real-time PCR of splenic cytokine genes. Chickens that succumbed to acute avian cholera after experimental challenge with strain X73 had high levels of INF-γ, IL-1β, IL-6, IL-12A, IL-22, IL-17A, and IL-17RA expressed in the spleen compared to all other experimental groups. Birds infected with capsule-deficient strains had chronic infections lasting 7 days or longer, and had increased levels of IL-17RA, CCR6, and IL-16 compared to non-infected control chickens. However, specific antibody titers increased only transiently to capsule-deficient strains and were low, indicating that antibodies are less important in managing and clearing P. multocida infections.

NLRX1 suppresses tumorigenesis and attenuates histiocytic sarcoma through the negative regulation of NF-κB signaling

Histiocytic sarcoma is an uncommon malignancy in both humans and veterinary species. Research exploring the pathogenesis of this disease is scarce; thus, diagnostic and therapeutic options for patients are limited. Recent publications have suggested a role for the NLR, NLRX1, in acting as a tumor suppressor. Based on these prior findings, we hypothesized that NLRX1 would function to inhibit tumorigenesis and thus the development of histiocytic sarcoma. To test this, we utilized Nlrx1-/- mice and a model of urethane-induced tumorigenesis. Nlrx1-/- mice exposed to urethane developed splenic histiocytic sarcoma that was associated with significant up-regulation of the NF-κB signaling pathway. Additionally, development of these tumors was also significantly associated with the increased regulation of genes associated with AKT signaling, cell death and autophagy. Together, these data show that NLRX1 suppresses tumorigenesis and reveals new genetic pathways involved in the pathobiology of histiocytic sarcoma.

Vaccination of sows with a dendritic cell-targeted porcine epidemic diarrhea virus S1 protein-based candidate vaccine reduced viral shedding but exacerbated gross pathological lesions in suckling neonatal piglets

Porcine epidemic diarrhea virus (PEDV) poses a serious threat to swine worldwide as evidenced by its recent introduction into the USA and the devastating economic impact it caused to the USA swine industry. Commercial vaccines against PEDV are available but their efficacies are inadequate. Therefore, vaccines with improved efficacy are needed to effectively control PEDV infections. We previously determined the immunogenicity of a novel dendritic cell (DC)-targeted PEDV S1 protein-based subunit vaccine in weaned piglets in which the PEDV antigen was targeted to DCs through a porcine Langerin-specific antibody. In this study, we evaluated the protective efficacy of this DC-targeting vaccine by immunizing sows at 5 and 2 weeks prior to farrowing and by challenging the 5-day-old piglets with PEDV. The results showed that immunization of sow with DC-targeted PEDV vaccine did not eliminate faecal virus shedding in piglets but significantly reduced faecal viral RNA levels in the early days after virus challenge. The vaccine also reduced the amount of PEDV antigen in intestinal tissues presented with intestinal villi regrowth. However, the DC-targeted vaccine neither mitigated PEDV clinical signs nor affected viral RNA loads in intestinal tissues of piglets. In the vaccinated sow, DC-targeted PEDV vaccine enhanced T helper 1-like cluster of differentiation (CD)4 T cell responses and induced IgG but not IgA-specific immune responses. The suckling piglets in the DC-targeted vaccine group showed increased gross pathological lesions in the small intestine. Results in this study provide insights into the effects of sow cellular immune responses to PEDV infection in suckling piglets.

Formula diet driven microbiota shifts tryptophan metabolism from serotonin to tryptamine in neonatal porcine colon

BACKGROUND

The gut microbiota of breast-fed and formula-fed infants differ significantly, as do the risks for allergies, gut dysfunction, and upper respiratory tract infections. The connections between breast milk, various formulas, and the profiles of gut bacteria to these childhood illnesses, as well as the mechanisms underlying the effects, are not well understood.

METHODS

We investigated distal colon microbiota by 16S RNA amplicon sequencing, morphology by histomorphometry, immune response by cytokine expression, and tryptophan metabolism in a pig model in which piglets were sow-fed, or fed soy or dairy milk-based formula from postnatal day (PND) 2 to 21.

RESULTS

Formula feeding significantly (p < 0.05) altered the colon microbiota relative to the sow feeding. A significant reduction in microbial diversity was noted with formula groups in comparison to sow-fed. Streptococcus, Blautia, Citrobacter, Butrycimonas, Parabacteroides, Lactococcus genera were increased with formula feeding relative to sow feeding. In addition, relative to sow feeding, Anaerotruncus, Akkermansia, Enterococcus, Acinetobacter, Christensenella, and Holdemania were increased in milk-fed piglets, and Biliophila, Ruminococcus, Clostridium were increased in soy-fed piglets. No significant gut morphological changes were noted. However, higher cytokine mRNA expression (BMP4, CCL11, CCL21) was observed in the distal colon of formula groups. Formula feeding reduced enterochromaffin cell number and serotonin, but increased tryptamine levels relative to sow feeding.

CONCLUSION

Our data confirm that formula diet alters the colon microbiota and appears to shift tryptophan metabolism from serotonin to tryptamine, which may lead to greater histamine levels and risk of allergies in infants.