Respiratory viral infection in neonatal piglets causes marked microglia activation in the hippocampus and deficits in spatial learning

Swine global genomic resources: insights into wild and domesticated populations

Suids, both domesticated and wild, are found on all continents except for Antarctica and provide valuable food resources for humans in addition to serving as important models for biomedical research. Continuing advances in genome sequencing have allowed researchers to compare the genomes from diverse populations of suids helping to clarify their evolution and dispersal. Further analysis of these samples may provide clues to improve disease resistance/resilience and productivity in domestic suids as well as better ways of classifying and conserving genetic diversity within wild and captive suids. Collecting samples from diverse populations of suids is resource intensive and may negatively impact endangered populations. Here we catalog extensive tissue and DNA samples from suids in collections in both Europe and North America. We include samples that have previously been used for whole genome sequencing, targeted DNA sequencing, RNA sequencing, and reduced representation bisulfite sequencing (RRBS). This work provides an important centralized resource for researchers who wish to access published databases.

Impaired spatial working memory and reduced hippocampal neuronal density in a rat model of neurocysticercosis

Neurocysticercosis (NCC) is the most common parasitic disease affecting the nervous system and is a leading cause of acquired epilepsy worldwide, as well as cognitive impairment, especially affecting memory. The aim of this study was to evaluate the effect of NCC on spatial working memory and its correlation with hippocampal neuronal density, in a rat model of NCC. This experimental study was conducted on female (n = 60) and male (n = 73) Holtzman rats. NCC was induced by intracranial inoculation of T. solium oncospheres in 14 day-old-rats. Spatial working memory was assessed using the T-maze test at 3, 6, 9, and 12 months post-inoculation, and sensorimotor evaluation was performed at 12 months post-inoculation. Hippocampal neuronal density was evaluated by immunostaining of NeuN-positive cells of the CA1 region. Of the rats inoculated with T. solium oncospheres, 87.2% (82/94) developed NCC. The study showed a significant decline in spatial working memory over a 1-year follow-up period in rats experimentally infected with NCC. Males showed an early decline that started at 3 months, while females demonstrated it at 9 months. Additionally, a decrease in neuronal density was observed in the hippocampus of NCC-infected rats, with a more significant reduction in rats with cysts in the hippocampus than in rats with cysts in other brain areas and control rats. This rat model of NCC provides valuable support for the relationship between neurocysticercosis and spatial working memory deficits. Further investigations are required to determine the mechanisms involved in cognitive impairment and establish the basis for future treatments.

Peripheral immune challenges elicit differential up-regulation of hippocampal cytokine and chemokine mRNA expression in a mouse model of the 15q13.3 microdeletion syndrome

The human heterozygous 15q13.3 microdeletion is associated with neuropathological disorders, most prominently with epilepsy and intellectual disability. The 1.5 Mb deletion encompasses six genes (FAN1 [MTMR15], MTMR10, TRPM1, KLF13, OTUD7A, and CHRNA7); all but one (TRPM1) are expressed in the brain. The 15q13.3 microdeletion causes highly variable neurological symptoms, and confounding factors may contribute to a more severe phenotype. CHRNA7 and KLF13 are involved in immune system regulation and altered immune responses may contribute to neurological deficits. We used the Df[h15q13]/+ transgenic mouse model with a heterozygous deletion of the orthologous region (Het) to test the hypothesis that the microdeletion increases innate immune responses compared to wild type (WT). Male and female mice were acutely challenged with the bacteriomimetic lipopolysaccharide (LPS, 0.1 mg/kg, i.p.) or the viral mimetic polyinosinic:polycytidylic acid (Poly(I:C), 5 mg/kg). Hippocampal mRNA expression of pro-inflammatory cytokines and chemokines were determined three hours after injection using quantitative PCR analysis. In controls, expression was not affected by sex or genotype. LPS and Poly(I:C) resulted in significantly increased hippocampal expression of cytokines, chemokines, and interferon-γ (IFNγ), with more robust increases for TNF-α, IL-6, IL-1β, CXCL1, and CCL2 by LPS, higher induction of IFNγ by Poly(I:C), and similar increases of CCL4 and CCL5 by both agents. Generally, Hets exhibited stronger responses than WT mice, and significant effects of genotype or genotype × treatment interactions were detected for CXCL1 and CCL5, and IL-6, IL-1β, and CCL4, respectively, after LPS. Sex differences were detected for some targets. LPS but not Poly(I:C), reduced overnight burrowing independent of sex or genotype, suggesting that LPS induced sickness behavior. Thus, mice carrying the microdeletion have an increased innate immune response following a LPS challenge, but further studies will have to determine the extent and mechanisms of altered immune activation and subsequent contributions to 15q13.3 microdeletion associated deficits.

SARS-CoV-2 is associated with changes in brain structure in UK Biobank

There is strong evidence for brain-related abnormalities in COVID-19 1-13 . It remains unknown however whether the impact of SARS-CoV-2 infection can be detected in milder cases, and whether this can reveal possible mechanisms contributing to brain pathology. Here, we investigated brain changes in 785 UK Biobank participants (aged 51-81) imaged twice, including 401 cases who tested positive for infection with SARS-CoV-2 between their two scans, with 141 days on average separating their diagnosis and second scan, and 384 controls. The availability of pre-infection imaging data reduces the likelihood of pre-existing risk factors being misinterpreted as disease effects. We identified significant longitudinal effects when comparing the two groups, including: (i) greater reduction in grey matter thickness and tissue-contrast in the orbitofrontal cortex and parahippocampal gyrus, (ii) greater changes in markers of tissue damage in regions functionally-connected to the primary olfactory cortex, and (iii) greater reduction in global brain size. The infected participants also showed on average larger cognitive decline between the two timepoints. Importantly, these imaging and cognitive longitudinal effects were still seen after excluding the 15 cases who had been hospitalised. These mainly limbic brain imaging results may be the in vivo hallmarks of a degenerative spread of the disease via olfactory pathways, of neuroinflammatory events, or of the loss of sensory input due to anosmia. Whether this deleterious impact can be partially reversed, or whether these effects will persist in the long term, remains to be investigated with additional follow up.

Chronic cerebral aspects of long COVID, post-stroke syndromes and similar states share their pathogenesis and perispinal etanercept treatment logic

The chronic neurological aspects of traumatic brain injury, post‐stroke syndromes, long COVID‐19, persistent Lyme disease, and influenza encephalopathy having close pathophysiological parallels that warrant being investigated in an integrated manner. A mechanism, common to all, for this persistence of the range of symptoms common to these conditions is described. While TNF maintains cerebral homeostasis, its excessive production through either pathogen‐associated molecular patterns or damage‐associated molecular patterns activity associates with the persistence of the symptoms common across both infectious and non‐infectious conditions. The case is made that this shared chronicity arises from a positive feedback loop causing the persistence of the activation of microglia by the TNF that these cells generate. Lowering this excess TNF is the logical way to reducing this persistent, TNF‐maintained, microglial activation. While too large to negotiate the blood‐brain barrier effectively, the specific anti‐TNF biological, etanercept, shows promise when administered by the perispinal route, which allows it to bypass this obstruction.

Neural Injury and Repair in a Novel Neonatal Mouse Model of Listeria Monocytogenes Meningoencephalitis

To improve the therapy of neonatal central nervous system infections, well-characterized animal models are urgently needed. The present study analyzes neuropathological alterations with particular focus on neural injury and repair in brains of neonatal mice with Listeria monocytogenes (LM) meningitis/meningoencephalitis using a novel nasal infection model. The hippocampal formation and frontal cortex of 14 neonatal mice with LM meningitis/meningoencephalitis and 14 uninfected controls were analyzed by histology, immunohistochemistry, and in situ tailing for morphological alterations. In the dentate gyrus of the hippocampal formation of mice with LM meningitis/meningoencephalitis, an increased density of apoptotic neurons visualized by in situ tailing (p = 0.04) and in situ tailing plus immunohistochemistry for activated Caspase-3 (p < 0.0001) was found. A decreased density of dividing cells stained with an anti-PCNA-antibody (p < 0.0001) and less neurogenesis visualized by anti-calretinin (p < 0.0001) and anti-calbindin (p = 0.01) antibodies were detected compared to uninfected controls. The density of microglia was higher in LM meningitis (p < 0.0001), while the density of astrocytes remained unchanged. Infiltrating monocytes and neutrophilic granulocytes likely contributed to tissue damage. In conclusion, in the brains of LM-infected mice a strong immune response was observed which led to neuronal apoptosis and an impaired neural regeneration. This model appears very suitable to study therapies against long-term sequelae of neonatal LM meningitis.

Up-Regulation of Immune Checkpoints in the Thymus of PRRSV-1-Infected Piglets in a Virulence-Dependent Fashion

Virulent porcine reproductive and respiratory syndrome virus (PRRSV) strains, such as the Lena strain, have demonstrated a higher thymus tropism than low virulent strains. Virulent PRRSV strains lead to severe thymus atrophy, which could be related to marked immune dysregulation. Impairment of T-cell functions through immune checkpoints has been postulated as a strategy executed by PRRSV to subvert the immune response, however, its role in the thymus, a primary lymphoid organ, has not been studied yet. Therefore, the goal of this study was to evaluate the expression of selected immune checkpoints (PD1/PDL1, CTLA4, TIM3, LAG3, CD200R1 and IDO1) in the thymus of piglets infected with two different PRRSV-1 strains. Thymus samples from piglets infected with the low virulent 3249 strain, the virulent Lena strain and mock-infected were collected at 1, 3, 6, 8 and 13 days post-infection (dpi) to analyze PRRSV viral load, relative quantification and immunohistochemical staining of immune checkpoints. PD1/PDL1, CTLA4, TIM3, LAG3 and IDO1 immune checkpoints were significantly up-regulated in the thymus of PRRSV infected piglets, especially in those infected with the virulent Lena strain from 6 dpi onwards. This up-regulation was associated with disease progression, high viral load and cell death. Co-expression of these molecules can affect T-cell development, maturation and selection, negatively regulating the host immune response against PRRSV.

High-resolution magnetic resonance imaging-based atlases for the young and adolescent domesticated pig (Sus scrofa)

BACKGROUND

Neurodevelopmental studies utilize the pig as a translational animal model due to anatomical and morphological similarities between the pig and human brain. However, neuroimaging resources are not as well developed for the pig as they are for humans and other animal models. We established a magnetic resonance imaging-based brain atlas at two different ages for biomedical studies utilizing the pig as a preclinical model.

NEW METHOD

Twenty artificially-reared domesticated male pigs (Sus scrofa) and thirteen sow-reared adolescent domesticated male pigs (Sus scrofa) underwent a series of scans measuring brain macrostructure, microstructure, and arterial cerebral blood volume.

RESULTS

An atlas for the 4-week-old and 12-week-old pig were created along with twenty-six regions of interest. Normative data for brain measures were obtained and detailed descriptions of the data processing pipelines were provided.

COMPARISON WITH EXISTING METHOD

Atlases at the two different ages were created for the pig utilizing newer imaging technology and software. This facilitates the performance of longitudinal studies and enables more precise volume measurements in pigs of various ages by appropriately representing the neuroanatomical features of younger and older pigs and accommodating the proportion differences of the brain over time.

CONCLUSION

Two high-resolution MRI brain atlases specific to the domesticated young and adolescent pig were created using defined image acquisition and data processing methods to facilitate the generation of high-quality normative data for neurodevelopmental research.

Activation of pro- and anti-inflammatory responses in lung tissue injury during the acute phase of PRRSV-1 infection with the virulent strain Lena

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Lena virulent strain caused an increase in sera levels of IFN-γ and IL-6.

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Lung viral load and PRRSV-N-protein⁺ cells were inversely correlated with CD163⁺ macrophages in the lung.

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CD14⁺ cells infiltrated interstitium to possibly replenish macrophages subsets.

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Lena-induced microscopic lung injury was linked to an increase of iNOS⁺ cells.

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The increase of CD200R1⁺ and FoxP3⁺ cells was associated with the course of lung injury.

Porcine reproductive and respiratory syndrome virus (PRRSV) plays a key role in porcine respiratory disease complex modulating the host immune response and favouring secondary bacterial infections. Pulmonary alveolar macrophages (PAMs) are the main cells supporting PRRSV replication, with CD163 as the essential receptor for viral infection. Although interstitial pneumonia is by far the representative lung lesion, suppurative bronchopneumonia is described for PRRSV virulent strains. This research explores the role of several immune markers potentially involved in the regulation of the inflammatory response and sensitisation of lung to secondary bacterial infections by PRRSV-1 strains of different virulence. Conventional pigs were intranasally inoculated with the virulent subtype 3 Lena strain or the low virulent subtype 1 3249 strain and euthanised at 1, 3, 6 and 8 dpi. Lena-infected pigs exhibited more severe clinical signs, macroscopic lung score and viraemia associated with an increase of IL-6 and IFN-γ in sera compared to 3249-infected pigs. Extensive areas of lung consolidation corresponding with suppurative bronchopneumonia were observed in Lena-infected pigs. Lung viral load and PRRSV-N-protein⁺ cells were always higher in Lena-infected animals. PRRSV-N-protein⁺ cells were linked to a marked drop of CD163⁺ macrophages. The number of CD14⁺ and iNOS⁺ cells gradually increased along PRRSV-1 infection, being more evident in Lena-infected pigs. The frequency of CD200R1⁺ and FoxP3⁺ cells peaked late in both PRRSV-1 strains, with a strong correlation between CD200R1⁺ cells and lung injury in Lena-infected pigs. These results highlight the role of molecules involved in the earlier and higher extent of lung lesions in piglets infected with the virulent Lena strain, pointing out the activation of routes potentially involved in the restraint of the local inflammatory response.

Isolation, culture, and downstream characterization of primary microglia and astrocytes from adult rodent brain and spinal cord

BACKGROUND

Neuroimmunologists aspire to understand the interactions between neurons, microglia, and astrocytes in the CNS. To study these cells, researchers work with either immortalized cell lines or primary cells acquired from animal tissue. Primary cells reflect in vivo characteristics and functionality compared to immortalized cells; however, they are challenging to acquire and maintain.

NEW METHOD

Established protocols to harvest primary glia use neonatal rodents, here we provide a method for simultaneously isolating microglia and astrocytes from brain and/or spinal cord from adult rodents. We utilized a discontinuous percoll density gradient enabling easy discrimination of these cell populations without enzymatic digestion or complex sorting techniques.

RESULTS

We found cells isolated from the percoll interface between 70 %-50 % were microglia, as they express ionizing calcium-binding adaptor molecule 1 (Iba1) in immunocytochemistry and CD11b^hi and CD45^lo using flow cytometry. Isolated cells from the 50 %-30 % interface were astrocytes as they express glial fibrillary acidic protein (GFAP) in immunocytochemistry and Glutamate aspartate transporter (GLAST)-1 using flow cytometry. Cultured microglia and astrocytes showed a functional increase in IL-6 production after treatment of lipopolysaccharide (LPS).

COMPARISON WITH EXISTING METHODS

Our method allows for rapid isolation of both microglia and astrocytes in one protocol with relatively few resources, preserves cellular phenotype, and yields high cell numbers without magnetic or antibody sorting.

CONCLUSION

Here we show a novel, single protocol to isolate microglia and astrocytes from brain and spinal cord tissue, allowing for culturing and other downstream applications from the cells of animals of various ages, which will be useful for researchers investigating these two major glial cell types from the brain or spinal cord of the same rodent.

Altered Hippocampal Epigenetic Regulation Underlying Reduced Cognitive Development in Response to Early Life Environmental Insults

The hippocampus is involved in learning and memory and undergoes significant growth and maturation during the neonatal period. Environmental insults during this developmental timeframe can have lasting effects on brain structure and function. This study assessed hippocampal DNA methylation and gene transcription from two independent studies reporting reduced cognitive development stemming from early life environmental insults (iron deficiency and porcine reproductive and respiratory syndrome virus (PRRSv) infection) using porcine biomedical models. In total, 420 differentially expressed genes (DEGs) were identified between the reduced cognition and control groups, including genes involved in neurodevelopment and function. Gene ontology (GO) terms enriched for DEGs were associated with immune responses, angiogenesis, and cellular development. In addition, 116 differentially methylated regions (DMRs) were identified, which overlapped 125 genes. While no GO terms were enriched for genes overlapping DMRs, many of these genes are known to be involved in neurodevelopment and function, angiogenesis, and immunity. The observed altered methylation and expression of genes involved in neurological function suggest reduced cognition in response to early life environmental insults is due to altered cholinergic signaling and calcium regulation. Finally, two DMRs overlapped with two DEGs, VWF and LRRC32, which are associated with blood brain barrier permeability and regulatory T-cell activation, respectively. These results support the role of altered hippocampal DNA methylation and gene expression in early life environmentally-induced reductions in cognitive development across independent studies.

The Potential Role of Dysfunctions in Neuron-Microglia Communication in the Pathogenesis of Brain Disorders

The bidirectional communication between neurons and microglia is fundamental for the proper functioning of the central nervous system (CNS). Chemokines and clusters of differentiation (CD) along with their receptors represent ligand-receptor signalling that is uniquely important for neuron - microglia communication. Among these molecules, CX3CL1 (fractalkine) and CD200 (OX-2 membrane glycoprotein) come to the fore because of their cell-type-specific localization. They are principally expressed by neurons when their receptors, CX3CR1 and CD200R, respectively, are predominantly present on the microglia, resulting in the specific axis which maintains the CNS homeostasis. Disruptions to this balance are suggested as contributors or even the basis for many neurological diseases. In this review, we discuss the roles of CX3CL1, CD200 and their receptors in both physiological and pathological processes within the CNS. We want to underline the critical involvement of these molecules in controlling neuron - microglia communication, noting that dysfunctions in their interactions constitute a key factor in severe neurological diseases, such as schizophrenia, depression and neurodegeneration-based conditions.

Hydrolyzed Fat Formula Increases Brain White Matter in Small for Gestational Age and Appropriate for Gestational Age Neonatal Piglets

Background: Intrauterine growth restriction is a common cause of small for gestational age (SGA) infants worldwide. SGA infants are deficient in digestive enzymes required for fat digestion and absorption compared to appropriate for gestational age (AGA) infants, putting them at risk for impaired neurocognitive development. Objective: The objective was to determine if a hydrolyzed fat (HF) infant formula containing soy free fatty acids, 2-monoacylglycerolpalmitate, cholesterol, and soy lecithin could increase brain tissue incorporation of essential fatty acids or white matter to enhance brain development in SGA and AGA neonatal piglet models. Methods: Sex-matched, littermate pairs of SGA (0.5-0.9 kg) and AGA (1.2-1.8 kg) 2 days old piglets (N = 60) were randomly assigned to control (CON) or HF formula diets in a 2 × 2 factorial design. On day 14, 24 piglets were used for hippocampal RNA-sequencing; the rest began a spatial learning task. On days 26-29, brain structure was assessed by magnetic resonance imaging (MRI). Cerebellum and hippocampus were analyzed for fatty acid content. Results: SGA piglets grew more slowly than AGA piglets, with no effect of diet on daily weight gain or weight at MRI. HF diet did not affect brain weight. HF diet increased relative volumes of 7 brain regions and white matter (WM) volume in both SGA and AGA piglets. However, HF did not ameliorate SGA total WM integrity deficits. RNA sequencing revealed SGA piglets had increased gene expression of synapse and cell signaling pathways and decreased expression of ribosome pathways in the hippocampus compared to AGA. HF decreased expression of immune response related genes in the hippocampus of AGA and SGA piglets, but did not correct gene expression patterns in SGA piglets. Piglets learned the T-maze task at the same rate, but SGA HF, SGA CON, and AGA HF piglets had more accurate performance than AGA CON piglets on reversal day 2. HF increased arachidonic acid (ARA) percentage in the cerebellum and total ARA in the hippocampus. Conclusions: HF enhanced brain development in the neonatal piglet measured by brain volume and WM volume in specific brain regions; however, more studies are needed to assess long-term outcomes.

CD200 is up-regulated in R6/1 transgenic mouse model of Huntington's disease

In Huntington's disease (HD), striatal medium spiny neurons (MSNs) are particularly sensitive to the presence of a CAG repeat in the huntingtin (HTT) gene. However, there are many evidences that cells from the peripheral immune system and central nervous system (CNS) immune cells, namely microglia, play an important role in the etiology and the progression of HD. However, it remains unclear whether MSNs neurodegeneration is mediated by a non-cell autonomous mechanism. The homeostasis in the healthy CNS is maintained by several mechanisms of interaction between all brain cells. Neurons can control microglia activation through several inhibitory mechanisms, such as the CD200-CD200R1 interaction. Due to the complete lack of knowledge about the CD200-CD200R1 system in HD, we determined the temporal patterns of CD200 and CD200R1 expression in the neocortex, hippocampus and striatum in the HD mouse models R6/1 and HdhQ111/7 from pre-symptomatic to manifest stages. In order to explore any alteration in the peripheral immune system, we also studied the levels of expression of CD200 and CD200R1 in whole blood. Although CD200R1 expression was not altered, we observed and increase in CD200 gene expression and protein levels in the brain parenchyma of all the regions we examined, along with HD pathogenesis in R6/1 mice. Interestingly, the expression of CD200 mRNA was also up-regulated in blood following a similar temporal pattern. These results suggest that canonical neuronal-microglial communication through CD200-CD200R1 interaction is not compromised, and CD200 up-regulation in R6/1 brain parenchyma could represent a neurotrophic signal to sustain or extend neuronal function in the latest stages of HD as pro-survival mechanism.

Maternal viral infection causes global alterations in porcine fetal microglia

Maternal infections during pregnancy are associated with increased risk of neurodevelopmental disorders, although the precise mechanisms remain to be elucidated. Previously, we established a maternal immune activation (MIA) model using swine, which results in altered social behaviors of piglet offspring. These behavioral abnormalities occurred in the absence of microglia priming. Thus, we examined fetal microglial activity during prenatal development in response to maternal infection with live porcine reproductive and respiratory syndrome virus. Fetuses were obtained by cesarean sections performed 7 and 21 d postinoculation (dpi). MIA fetuses had reduced brain weights at 21 dpi compared to controls. Furthermore, MIA microglia increased expression of major histocompatibility complex class II that was coupled with reduced phagocytic and chemotactic activity compared to controls. High-throughput gene-expression analysis of microglial-enriched genes involved in neurodevelopment, the microglia sensome, and inflammation revealed differential regulation in primary microglia and in whole amygdala tissue. Microglia density was increased in the fetal amygdala at 7 dpi. Our data also reveal widespread sexual dimorphisms in microglial gene expression and demonstrate that the consequences of MIA are sex dependent. Overall, these results indicate that fetal microglia are significantly altered by maternal viral infection, presenting a potential mechanism through which MIA impacts prenatal brain development and function.

Differential Microglial Morphological Response, TNFα, and Viral Load in Sedentary-like and Active Murine Models After Systemic Non-neurotropic Dengue Virus Infection

Peripheral inflammatory stimuli increase proinflammatory cytokines in the bloodstream and central nervous system and activate microglial cells. Here we tested the hypothesis that contrasting environments mimicking sedentary and active lives would be associated with differential microglial morphological responses, inflammatory cytokines concentration, and virus load in the peripheral blood. For this, mice were maintained either in standard (standard environment) or enriched cages (enriched environment) and then subjected to a single (DENV1) serotype infection. Blood samples from infected animals showed higher viral loads and higher tumor necrosis factor-α (TNFα) mRNA concentrations than control subjects. Using an unbiased stereological sampling approach, we selected 544 microglia from lateral septum for microscopic 3D reconstruction. Morphological complexity contributed most to cluster formation. Infected groups exhibited significant increase in the microglia morphological complexity and number, despite the absence of dengue virus antigens in the brain. Two microglial phenotypes (type I with lower and type II with higher morphological complexity) were found in both infected and control groups. However, microglia from infected mice maintained in enriched environment showed only one morphological phenotype. Two-way ANOVA revealed that environmental changes and infection influenced type-I and II microglial morphologies and number. Environmental enrichment and infection interactions may contribute to microglial morphological change to a point that type-I and II morphological phenotypes could no longer be distinguished in infected mice from enriched environment. Significant linear correlation was found between morphological complexity and TNFα peripheral blood. Our findings demonstrated that sedentary-like and active murine models exhibited differential microglial responses and peripheral inflammation to systemic non-neurotropic infections with DENV1 virus.

Dietary Iron Deficiency Impaired Peripheral Immunity but Did Not Alter Brain Microglia in PRRSV-Infected Neonatal Piglets

During the postnatal period the developing brain is vulnerable to insults including nutrient insufficiency and infection that may lead to disrupted development and cognitive dysfunction. Since iron deficiency (ID) often presents with immunodeficiency, the objective of this study was to investigate peripheral viremia and inflammation as well as brain microglial phenotype and function when ID and respiratory infection occur simultaneously in a neonatal piglet model. On postnatal day 2 (PD 2) male and female piglets were assigned to one of four treatments and fed either control or ID milk replacer. On PD 8 half the pigs on each diet were inoculated with either vehicle or porcine reproductive and respiratory syndrome virus (PRRSV; P-129). Blood samples were collected prior to inoculation (PD 7) and repeated once weekly. Rectal temperature, feeding score, and sickness behavior were measured daily until PD 28. Hematocrit, hemoglobin, and serum iron were reduced by ID but not PRRSV infection. PRRSV-infected piglets displayed viremia by PD 14; however, those fed control diet had lower viral titer on PD 28, while circulating virus remained elevated in those fed an ID diet, suggesting that ID either impaired immune function necessary for viral clearance or increased viral replication. ID piglets infected with PRRSV displayed reduced sickness behavior compared to those fed control diet on PD 13-15 and 18-20. While ID piglet sickness behavior progressively worsened, piglets fed control diet displayed improved sickness score after PD 21. Microglia isolated from PRRSV piglets had increased MHCII expression and phagocytic activity ex vivo compared to uninfected piglets. ID did not alter microglial activation or phagocytic activity. Similarly, microglial cytokine expression was increased by PRRSV but unaffected by ID, in stark contrast to peripheral blood mononuclear cell (PBMC) cytokine expression, which was increased by infection and generally decreased by ID. Taken together, these data suggest that ID decreases peripheral immune function leading to increased viremia, but immune activity in the brain is protected from acute ID.

Clinical and experimental aspects of breathing modulation by inflammation

Neuroinflammation is produced by local or systemic alterations and mediated mainly by glia, affecting the activity of various neural circuits including those involved in breathing rhythm generation and control. Several pathological conditions, such as sudden infant death syndrome, obstructive sleep apnea and asthma exert an inflammatory influence on breathing-related circuits. Consequently breathing (both resting and ventilatory responses to physiological challenges), is affected; e.g., responses to hypoxia and hypercapnia are compromised. Moreover, inflammation can induce long-lasting changes in breathing and affect adaptive plasticity; e.g., hypoxic acclimatization or long-term facilitation. Mediators of the influences of inflammation on breathing are most likely proinflammatory molecules such as cytokines and prostaglandins. The focus of this review is to summarize the available information concerning the modulation of the breathing function by inflammation and the cellular and molecular aspects of this process. I will consider: 1) some clinical and experimental conditions in which inflammation influences breathing; 2) the variety of experimental approaches used to understand this inflammatory modulation; 3) the likely cellular and molecular mechanisms.

Necrotizing enterocolitis is associated with acute brain responses in preterm pigs

Background

Necrotizing enterocolitis (NEC) is an acute gut inflammatory disorder that occurs in preterm infants in the first weeks after birth. Infants surviving NEC often show impaired neurodevelopment. The mechanisms linking NEC lesions with later neurodevelopment are poorly understood but may include proinflammatory signaling in the immature brain. Using preterm pigs as a model for preterm infants, we hypothesized that severe intestinal NEC lesions are associated with acute effects on the developing hippocampus.

Methods

Cesarean-delivered preterm pigs (n = 117) were reared for 8 days and spontaneously developed variable severity of NEC lesions. Neonatal arousal, physical activity, and in vitro neuritogenic effects of cerebrospinal fluid (CSF) were investigated in pigs showing NEC lesions in the colon (Co-NEC) or in the small intestine (Si-NEC). Hippocampal transcriptome analysis and qPCR were used to assess gene expressions and their relation to biological processes, including neuroinflammation, and neural plasticity. Microglia activation was quantified by stereology. The neuritogenic response to selected proteins was investigated in primary cultures of hippocampal neurons.

Results

NEC development rapidly reduced the physical activity of pigs, especially when lesions occurred in the small intestine. Si-NEC and Co-NEC were associated with 27 and 12 hippocampal differentially expressed genes (DEGs), respectively. These included genes related to neuroinflammation (i.e., S100A8, S100A9, IL8, IL6, MMP8, SAA, TAGLN2) and hypoxia (i.e., PDK4, IER3, TXNIP, AGER), and they were all upregulated in Si-NEC pigs. Genes related to protection against oxidative stress (HBB, ALAS2) and oligodendrocytes (OPALIN) were downregulated in Si-NEC pigs. CSF collected from NEC pigs promoted neurite outgrowth in vitro, and the S100A9 and S100A8/S100A9 proteins may mediate the neuritogenic effects of NEC-related CSF on hippocampal neurons. NEC lesions did not affect total microglial cell number but markedly increased the proportion of Iba1-positive amoeboid microglial cells.

Conclusions

NEC lesions, especially when present in the small intestine, are associated with changes to hippocampal gene expression that potentially mediate neuroinflammation and disturbed neural circuit formation via enhanced neuronal differentiation. Early brain-protective interventions may be critical for preterm infants affected by intestinal NEC lesions to reduce their later neurological dysfunctions.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1201-x) contains supplementary material, which is available to authorized users.

Altered Hippocampal Gene Expression and Morphology in Fetal Piglets following Maternal Respiratory Viral Infection

Maternal infection during pregnancy increases the risk of neurobehavioral problems in offspring. Evidence from rodent models indicates that the maternal immune response to infection can alter fetal brain development, particularly in the hippocampus. However, information on the effects of maternal viral infection on fetal brain development in gyrencephalic species is limited. Thus, the objective of this study was to assess several effects of maternal viral infection in the last one-third of gestation on hippocampal gene expression and development in fetal piglets. Pregnant gilts were inoculated with porcine reproductive and respiratory syndrome virus (PRRSV) at gestational day (GD) 76 and the fetuses were removed by cesarean section at GD 111 (3 days before anticipated parturition). The gilts infected with PRRSV had elevated plasma interleukin-6 levels and developed transient febrile and anorectic responses lasting approximately 21 days. Despite having a similar overall body weight, fetuses from the PRRSV-infected gilts had a decreased brain weight and altered hippocampal gene expression compared to fetuses from control gilts. Notably, maternal infection caused a reduction in estimated neuronal numbers in the fetal dentate gyrus and subiculum. The number of proliferative Ki-67+ cells was not altered, but the relative integrated density of GFAP+ staining was increased, in addition to an increase in GFAP gene expression, indicating astrocyte-specific gliosis. Maternal viral infection caused an increase in fetal hippocampal gene expression of the inflammatory cytokines TNF-α and IFN-γ and the myelination marker myelin basic protein. MHCII protein, a classic monocyte activation marker, was reduced in microglia, while expression of the MHCII gene was decreased in hippocampal tissue of the fetuses from PRRSV-infected gilts. Together, these data suggest that maternal viral infection at the beginning of the last trimester results in a reduction in fetal hippocampal neurons that is evident 5 weeks after infection, when fetal piglets are near full term. The neuronal reduction was not accompanied by pronounced neuroinflammation at GD 111, indicating that any activation of classic neuroinflammatory pathways by maternal viral infection, if present, is mostly resolved by parturition.

Long-Term Neuroinflammation Induced by Influenza A Virus Infection and the Impact on Hippocampal Neuron Morphology and Function

Acute influenza infection has been reported to be associated with neurological symptoms. However, the long-term consequences of an infection with neurotropic and non-neurotropic influenza A virus (IAV) variants for the CNS remain elusive. We can show that spine loss in the hippocampus after infection with neurotropic H7N7 (rSC35M) and non-neurotropic H3N2 (maHK68) in female C57BL/6 mice persists well beyond the acute phase of the disease. Although spine number was significantly reduced at 30 d postinfection (dpi) with H7N7 or H3N2, full recovery could only be observed much later at 120 dpi. Infection with H1N1 virus, which was shown previously to affect spine number and hippocampus-dependent learning acutely, had no significant long-term effects. Spine loss was associated with an increase in the number of activated microglia, reduced long-term potentiation in the hippocampus, and impairment in spatial memory formation, indicating that IAV-associated inflammation induced functional and structural alterations in hippocampal networks. Transcriptome analyses revealed regulation of many inflammatory and neuron- and glia-specific genes in H3N2- and H7N7-infected mice at day 18 and in H7N7-infected mice at day 30 pi that related to the structural and functional alterations. Our data provide evidence that neuroinflammation induced by neurotropic H7N7 and infection of the lung with a non-neurotropic H3N2 IAV result in long-term impairments in the CNS. IAV infection in humans may therefore not only lead to short-term responses in infected organs, but may also trigger neuroinflammation and associated chronic alterations in the CNS.SIGNIFICANCE STATEMENT In the acute phase of influenza infection, neuroinflammation can lead to alterations in hippocampal neuronal morphology and cognitive deficits. The results of this study now also provide evidence that neuroinflammation induced by influenza A virus (IAV) infection can induce longer-lasting, virus-specific alterations in neuronal connectivity that are still detectable 1 month after infection and are associated with impairments in spatial memory formation. IAV infection in humans may therefore not only lead to short-term responses in infected organs, but may also trigger neuroinflammation and associated chronic alterations in the CNS.

Use of a Piglet Model for the Study of Anesthetic-induced Developmental Neurotoxicity (AIDN): A Translational Neuroscience Approach

Anesthesia cannot be avoided in many cases when surgery is required, particularly in children. Recent investigations in animals have raised concerns that anesthesia exposure may lead to neuronal apoptosis, known as anesthesia-induced developmental neurotoxicity (AIDN). Furthermore, some clinical studies in children have suggested that anesthesia exposure may lead to neurodevelopmental deficits later in life. Nonetheless, an ideal animal model for preclinical study has yet to be developed. The neonatal piglet represents a valuable model for preclinical study, as they share a striking number of developmental similarities with humans.

The anatomy and physiology of piglets allow for implementation of rigorous human perioperative conditions in both survival and non-survival procedures. Femoral artery catheterization allows for close monitoring, thus enabling prompt correction of any deviation of the piglet's vital signs and chemistries. In addition, there are multiple developmental similarities between piglets and human neonates. The techniques required to use piglets for experimentation will require experience to master. A pediatric anesthesiologist is a critical member of the investigative team. We describe, in a general sense, the appropriate use of a piglet model for neurodevelopmental study.

NLRP3 Inflammasome in Neurological Diseases, from Functions to Therapies

Neuroinflammation has been identified as a causative factor of multiple neurological diseases. The nucleotide-binding oligomerization domain-, leucine-rich repeat- and pyrin domain-containing 3 (NLRP3) inflammasome, a subcellular multiprotein complex that is abundantly expressed in the central nervous system (CNS), can sense and be activated by a wide range of exogenous and endogenous stimuli such as microbes, aggregated and misfolded proteins, and adenosine triphosphate, which results in activation of caspase-1. Activated caspase-1 subsequently leads to the processing of interleukin-1β (IL-1β) and interleukin-18 (IL-18) pro-inflammatory cytokines and mediates rapid cell death. IL-1β and IL-18 drive inflammatory responses through diverse downstream signaling pathways, leading to neuronal damage. Thus, the NLRP3 inflammasome is considered a key contributor to the development of neuroinflammation. In this review article, we briefly discuss the structure and activation the NLRP3 inflammasome and address the involvement of the NLRP3 inflammasome in several neurological disorders, such as brain infection, acute brain injury and neurodegenerative diseases. In addition, we review a series of promising therapeutic approaches that target the NLRP3 inflammasome signaling including anti-IL-1 therapy, small molecule NLRP3 inhibitors and other compounds, however, these approaches are still experimental in neurological diseases. At present, it is plausible to generate cell-specific conditional NLRP3 knockout (KO) mice via the Cre system to investigate the role of the NLRP3 inflammasome, which may be instrumental in the development of novel pharmacologic investigations for neuroinflammation-associated diseases.

Maternal viral infection during pregnancy elicits anti-social behavior in neonatal piglet offspring independent of postnatal microglial cell activation

Maternal infection during pregnancy increases risk for neurodevelopmental disorders and reduced stress resilience in offspring, but the mechanisms are not fully understood. We hypothesized that piglets born from gilts infected with a respiratory virus during late gestation would exhibit aberrant microglia activity, cognitive deficits and reduced sociability. Pregnant gilts were inoculated with porcine reproductive and respiratory syndrome virus (PRRSV; 5×10⁵ TCID₅₀ of live PRRSV) or saline at gestational day 76. Gilts infected with PRRSV exhibited fever (p<0.01) and reduced appetite (p<0.001) for 2weekspost-inoculation and were PRRSV-positive at parturition. Piglets born from infected and control gilts were weaned at postnatal day (PD) 1 and assigned to two groups. Group 1 was challenged with lipopolysaccharide (LPS, 5μg/kg body weight i.p.) or saline on PD 14 and tissues were collected. Group 2 was tested in a T-maze task to assess spatial learning and in a 3-chamber arena with unfamiliar conspecifics to assess social behavior from PD 14-27. Microglia (CD11b⁺ CD45^low) isolated from Group 2 piglets at PD 28 were challenged ex vivo with LPS; a subset of cells was analyzed for MHCII expression. Maternal infection did not affect offspring circulating TNFα, IL-10, or cortisol levels basally or 4h post-LPS challenge. While performance in the T-maze task was not affected by maternal infection, both sociability and preference for social novelty were decreased in piglets from infected gilts. There was no effect of maternal infection on microglial MHCII expression or LPS-induced cytokine production. Taken together, these results suggest the reduced social behavior elicited by maternal infection is not due to aberrant microglia activity postnatally.

Postnatal Iron Deficiency Alters Brain Development in Piglets

BACKGROUND

Cognitive deficits associated with postnatal iron deficiency (ID) suggest abnormal brain development, but little is known about animals with gyrencephalic brains.

OBJECTIVE

The objective was to assess the impact of ID on brain development in piglets.

METHODS

Male and female Yorkshire piglets were reared from postnatal day (PD) 2 until PD 29 or 30 by using milk replacer adequate [control (CON)] or deficient (100 compared with 10 mg/kg) in iron and subjected to MRI to assess brain macrostructure, microstructure, and metabolites in the dorsal hippocampi and intervening space. After MRI, brains were collected for histology. Hematocrit, hemoglobin, and liver iron were measured to determine iron status.

RESULTS

Hematocrit and hemoglobin in ID piglets were less than CON after PD 14 (P < 0.001), and at the study end liver iron in ID piglets was less than CON (P < 0.001). Brain region volumes were not affected by ID, but changes in brain composition were evident. ID piglets had less white matter in 78,305 voxels, with large clusters in the hippocampus and cortex. ID piglets had less gray matter in 13,625 voxels primarily in cortical areas and more gray matter in 28,017 voxels, most notably in olfactory bulbs and hippocampus. The major effect of ID on white matter was supported by lower fractional anisotropy values in the corpus callosum (0.300 compared with 0.284, P = 0.006) and in whole brain white matter (0.313 compared with 0.307, P = 0.002) in ID piglets. In coronal brain sections, corpus callosum width was less (P = 0.043) in ID piglets. Inositol was lower (P = 0.01) and phosphocholine was higher (P = 0.03) in hippocampus of ID piglets.

CONCLUSIONS

Postnatal ID in piglets affects brain development, especially white matter. If the effects of ID persist, it might explain the lasting detrimental effects on cognition.

Peripheral viral infection induced microglial sensome genes and enhanced microglial cell activity in the hippocampus of neonatal piglets

Although poorly understood, early-life infection is predicted to affect brain microglial cells, making them hypersensitive to subsequent stimuli. To investigate this, we assessed gene expression in hippocampal tissue obtained from a previously published study reporting increased microglial cell activity and reduced hippocampal-dependent learning in neonatal piglets infected with porcine reproductive and respiratory syndrome virus (PRRSV), a virus that induces interstitial pneumonia. Infection altered expression of 455 genes, of which 334 were up-regulated and 121 were down-regulated. Functional annotation revealed that immune function genes were enriched among the up-regulated differentially expressed genes (DEGs), whereas calcium binding and synaptic vesicle genes were enriched among the down-regulated DEGs. Twenty-six genes encoding part of the microglia sensory apparatus (i.e., the sensome) were up-regulated (e.g., IL1R1, TLR2, and TLR4), whereas 15 genes associated with the synaptosome and synaptic receptors (e.g., NPTX2, GABRA2, and SLC5A7) were down-regulated. As the sensome may foretell microglia reactivity, we next inoculated piglets with culture medium or PRRSV at PD 7 and assessed hippocampal microglia morphology and function at PD 28 when signs of infection were waning. Consistent with amplification of the sensome, microglia from PRRSV piglets had enhanced responsiveness to chemoattractants, increased phagocytic activity, and secreted more TNFα in response to lipopolysaccharide and Poly I:C. Immunohistochemical staining indicated PRRSV infection increased microglia soma length and length-to-width ratio. Bipolar rod-like microglia not evident in hippocampus of control piglets, were present in infected piglets. Collectively, this study suggests early-life infection alters the microglia sensome as well as microglial cell morphology and function.

Unraveling the swine genome: implications for human health

The pig was first used in biomedical research in ancient Greece and over the past few decades has quickly grown into an important biomedical research tool. Pigs have genetic and physiological traits similar to humans, which make them one of the most useful and versatile animal models. Owing to these similarities, data generated from porcine models are more likely to lead to viable human treatments than those from murine work. In addition, the similarity in size and physiology to humans allows pigs to be used for many experimental approaches not feasible in mice. Research areas that employ pigs range from neonatal development to translational models for cancer therapy. Increasing numbers of porcine models are being developed since the release of the swine genome sequence, and the development of additional porcine genomic and epigenetic resources will further their use in biomedical research.

A novel, clinically relevant use of a piglet model to study the effects of anesthetics on the developing brain

Background

Anesthesia-induced neurotoxicity research in the developing brain must rely upon an unimpeachable animal model and a standardized treatment approach. In this manner, identification of mechanisms of action may be undertaken. The goal of this study was to develop a novel, clinically relevant, translational way to use a piglet model to investigate anesthesia effects on the developing brain.

Methods

29 newborn piglets were assigned to either: (1) control (no intervention, n = 10); (2) lipopolysaccharide (LPS; positive inflammatory control, n = 9); or (3) isoflurane anesthesia (n = 10). Positive inflammatory control animals were given 100 mcg/kg LPS from Escherichia coli intraperitoneally (IP) on the same day as those receiving isoflurane. Isoflurane was administered for 3 h while care was taken to ensure human perioperative conditions. To establish a clinical scenario, each animal was intubated and monitored with pulse oximetry, invasive and non-invasive blood pressure, electrocardiogram, temperature, end-tidal CO₂, anesthetic concentration, and iSTAT blood analysis. All animals were sacrificed after 48 h using transcardiac perfusion of ice-cold, heparinized phosphate buffered saline (PBS) followed by 4 % paraformaldehyde (PFA). Brains were collected and histopathological analysis focused on the entorhinal cortex looking for degenerative changes due to its critical role in learning and memory. Reliable identification of entorhinal cortex was achieved by using colored ink on the surface of the brains, which was then cross-referenced with microscopic anatomy. Hematoxylin & eosin-stained high-power fields was used to quantify cells. ImageJ™ (National Institutes of Health, Bethesda, MD, USA) was used to count absolute number of progenitor glial cells (PGC) and number of PGCs per cluster. Immunohistochemistry was also utilized to ensure positive identification of cellular structures.

Results

Histopathological sections of 28 brains were analyzed. One animal in the LPS group died shortly after administration, presumably from inadvertent intravascular injection. There was an acute basal ganglia ischemic infarct in one isoflurane-treated animal. A large number of small, round nucleated cells were seen throughout layer II of the entorhinal cortex in all animals. These cells were identified as PGCs using immunohistochemistry and light microscopy. Although there was no difference in the absolute number of PGCs between the groups, animals given isoflurane or LPS demonstrated a significant increase in cells forming ‘clusters’ in the entorhinal cortex. An apparent change in the pattern of doublecortin labeling also suggests changes in neuronal precursors and undifferentiated neurons.

Conclusions

This study represents the first novel use of a clinically relevant neonatal piglet model to study anesthesia effects on the developing brain. LPS induces neuroinflammation, and this is a potential mechanism for LPS and perhaps isoflurane in causing a change in progenitor cell distribution. We postulate that the isoflurane-induced change in glial progenitor cell distribution could have important implications for cell differentiation, maturation and neural circuit behavior in the rapidly developing brain.

Application of Bioactive Compounds from Scutellaria in Neurologic Disorders

Inflammation of the brain is one of the most highly researched yet mysterious areas in modern day neurology. The process of inflammation is a normal mechanism of wound healing that can result from acute injuries such as traumas or can be caused by genetic/environmental factors. After the initial insult, the immune system defenses, specifically microglial cells, are activated in order to combat the infection or injury. However, prolonged or chronic inflammation is often deleterious due mainly to accumulation of free reactive oxygen species (ROS) and other pro-inflammatory cytokines in the brain FADDIN EN.CITE. Plant-derived natural compounds have the potential to ameliorate the causes and symptoms of neuroinflammation, due to their various anti-oxidant and anti-inflammatory activities, without completely muting the immune defenses. Scutellaria is a perennial plant in the mint family that has been used to treat diseases in Asia and Eastern Europe throughout history. This chapter reviews the active components of various Scutellaria species and their mechanisms of action to prevent chronic neurologic disorders involving neuroinflammation and neurodegeneration.

Early postnatal respiratory viral infection induces structural and neurochemical changes in the neonatal piglet brain

Infections that cause inflammation during the postnatal period are common, yet little is known about their impact on brain development in gyrencephalic species. To address this issue, we investigated brain development in domestic piglets which have brain growth and morphology similar to human infants, after experimentally infecting them with porcine reproductive and respiratory syndrome virus (PRRSV) to induce an interstitial pneumonia Piglets were inoculated with PRRSV on postnatal day (PD) 7 and magnetic resonance imaging (MRI) was used to assess brain macrostructure (voxel-based morphometry), microstructure (diffusion tensor imaging) and neurochemistry (MR-spectroscopy) at PD 29 or 30. PRRSV piglets exhibited signs of infection throughout the post-inoculation period and had elevated plasma levels of TNFα at the end of the study. PRRSV infection increased the volume of several components of the ventricular system including the cerebral aqueduct, fourth ventricle, and the lateral ventricles. Group comparisons between control and PRRSV piglets defined 8 areas where PRRSV piglets had less gray matter volume; 5 areas where PRRSV piglets had less white matter volume; and 4 relatively small areas where PRRSV piglets had more white matter. Of particular interest was a bilateral reduction in gray and white matter in the primary visual cortex. PRRSV piglets tended to have reduced fractional anisotropy in the corpus callosum. Additionally, N-acetylaspartate, creatine, and myo-inositol were decreased in the hippocampus of PRRSV piglets suggesting disrupted neuronal and glial health and energy imbalances. These findings show in a gyrencephalic species that early-life infection can affect brain growth and development.

A Critical Review of Models of Perinatal Infection

One of the central, unanswered questions in perinatology is why preterm infants continue to have such poor long-term neurodevelopmental, cognitive and learning outcomes, even though severe brain injury is now rare. There is now strong clinical evidence that one factor underlying disability may be infection, as well as nonspecific inflammation, during fetal and early postnatal life. In this review, we examine the experimental evidence linking both acute and chronic infection/inflammation with perinatal brain injury and consider key experimental determinants, including the microglia response, relative brain and immune maturity and the pattern of exposure to infection. We highlight the importance of the origin and derivation of the bacterial cell wall component lipopolysaccharide. Such experimental paradigms are essential to determine the precise time course of the inflammatory reaction and to design targeted neuroprotective strategies to protect the perinatal brain from infection and inflammation.

Early postnatal respiratory viral infection alters hippocampal neurogenesis, cell fate, and neuron morphology in the neonatal piglet

Respiratory viral infections are common during the neonatal period in humans, but little is known about how early-life infection impacts brain development. The current study used a neonatal piglet model as piglets have a gyrencephalic brain with growth and development similar to human infants. Piglets were inoculated with porcine reproductive and respiratory syndrome virus (PRRSV) to evaluate how chronic neuroinflammation affects hippocampal neurogenesis and neuron morphology. Piglets in the neurogenesis study received one bromodeoxyuridine injection on postnatal day (PD) 7 and then were inoculated with PRRSV. Piglets were sacrificed at PD 28 and the number of BrdU+ cells and cell fate were quantified in the dentate gyrus. PRRSV piglets showed a 24% reduction in the number of newly divided cells forming neurons. Approximately 15% of newly divided cells formed microglia, but this was not affected by sex or PRRSV. Additionally, there was a sexual dimorphism of new cell survival in the dentate gyrus where males had more cells than females, and PRRSV infection caused a decreased survival in males only. Golgi impregnation was used to characterize dentate granule cell morphology. Sholl analysis revealed that PRRSV caused a change in inner granule cell morphology where the first branch point was extended further from the cell body. Males had more complex dendritic arbors than females in the outer granule cell layer, but this was not affected by PRRSV. There were no changes to dendritic spine density or morphology distribution. These findings suggest that early-life viral infection can impact brain development.

The domestic piglet: an important model for investigating the neurodevelopmental consequences of early life insults

Insults in the prenatal and early postnatal period increase the risk for behavioral problems later in life. One hypothesis is that pre- and postnatal stressors influence structural and functional brain plasticity. Understanding the mechanisms is important, but progress has lagged because certain studies in human infants are impossible, while others are extremely difficult. Furthermore, results from popular rodent models are difficult to translate to human infants owing to the substantial differences in brain development and morphology. Because it overcomes some of these obstacles, the domestic piglet has emerged as an important model. Piglets have a gyrencephalic brain that develops similar to the human brain and that can be assessed in vivo by using clinical-grade neuroimaging instruments. Furthermore, owing to their precocial nature, piglets can be weaned at birth and used in behavioral testing paradigms to assess cognitive behavior at an early age. Thus, the domestic piglet represents an important translational model for investigating the neurodevelopmental consequences of early life insults.