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Pseudorabies virus (PRV) is a porcine alphaherpesvirus that belongs to the Herpesviridae family. We showed earlier that infection of porcine epithelial cells with PRV triggers activation of the nuclear factor κB (NF-κB) pathway, a pivotal signaling axis in the early immune response. However, PRV-induced NF-κB activation does not lead to NF-κB-dependent gene expression. Here, using electrophoretic mobility shift assays (EMSAs), we show that PRV does not disrupt the ability of NF-κB to interact with its κB target sites. Assessing basal cellular transcriptional activity in PRV-infected cells by quantitation of prespliced transcripts of constitutively expressed genes uncovered a broad suppression of cellular transcription by PRV, which also affects the inducible expression of NF-κB target genes. Host cell transcription inhibition was rescued when viral genome replication was blocked using phosphonoacetic acid (PAA). Remarkably, we found that host gene expression shutoff in PRV-infected cells correlated with a substantial retention of the NF-κB subunit p65, the TATA box binding protein, and RNA polymerase II-essential factors required for (NF-κB-dependent) gene transcription-in expanding PRV replication centers in the nucleus and thereby away from the host chromatin. This study reveals a potent mechanism used by the alphaherpesvirus PRV to steer the protein production capacity of infected cells to viral proteins by preventing expression of host genes, including inducible genes involved in mounting antiviral responses. IMPORTANCE Herpesviruses are highly successful pathogens that cause lifelong persistent infections of their host. Modulation of the intracellular environment of infected cells is imperative for the success of virus infections. We reported earlier that a DNA damage response in epithelial cells infected with the alphaherpesvirus pseudorabies virus (PRV) results in activation of the hallmark proinflammatory NF-κB signaling axis but, remarkably, that this activation does not lead to NF-κB-induced (proinflammatory) gene expression. Here, we report that PRV-mediated inhibition of host gene expression stretches beyond NF-κB-dependent gene expression and in fact reflects a broad inhibition of host gene transcription, which correlates with a substantial recruitment of essential host transcription factors in viral replication compartments in the nucleus, away from the host chromatin. These data uncover a potent alphaherpesvirus mechanism to interfere with production of host proteins, including proteins involved in antiviral responses.

Background: Pseudorabies virus (PRV) infection leads to high mortality in swine. Despite extensive efforts, effective treatments against PRV infection are limited. Furthermore, the inflammatory response induced by PRV strain GXLB-2013 is unclear., Objectives: Our study aimed to investigate the inflammatory response induced by PRV strain GXLB-2013, establish an inflammation model to elucidate the pathogenesis of PRV infection further, and develop effective drugs against PRV infection., Methods: Kunming mice were infected intramuscularly with medium, LPS, and different doses of PRV-GXLB-2013. Viral spread and histopathological damage to brain, spleen, and lung were determined at 7 days post-infection (dpi). Immune organ indices, levels of reactive oxygen species (ROS), nitric oxide (NO), and inflammatory cytokines, as well as levels of activity of COX-2 and iNOS were determined at 4, 7, and 14 dpi., Results: At 10⁵-10⁶ TCID 50 PRV produced obviously neurological symptoms and 100% mortality in mice. Viral antigens were detectable in kidney, heart, lung, liver, spleen, and brain. In addition, inflammatory injuries were apparent in brain, spleen, and lung of PRV-infected mice. Moreover, PRV induced increases in immune organ indices, ROS and NO levels, activity of COX-2 and iNOS, and the content of key pro-inflammatory cytokines, including interleukin (IL)-1β, IL-6, tumor necrosis factor-α, interferon-γ and MCP-1. Among the tested doses, 10² TCID 50 of PRV produced a significant inflammatory mediator increase., Conclusions: An inflammatory model induced by PRV infection was established in mice, and 10² TCID 50 PRV was considered as the best concentration for the establishment of the model., Competing Interests: The authors declare no conflicts of interest., (© 2021 The Korean Society of Veterinary Science.)

Pseudorabies virus (PRV) infection causes great economic losses in the pig industry. By disrupting the homeostasis of the endoplasmic reticulum (ER), many viral infections induce ER stress and trigger the unfolded protein response (UPR). However, the roles of ER stress and UPR in PRV infection remain unclear. In the present study, we demonstrate that the expression of the ER stress marker glucose-regulated protein 78 (GRP78) increased during the early stages of PRV infection, indicating that ER stress was induced. Examination of the three branches of the UPR revealed that the IRE1-XBP1 and eIF2α-ATF4 pathways were activated during PRV infection. In addition, PRV induced apoptosis in later stages of infection through the CHOP-Bcl2 axis. Overexpression of GRP78 or ER stress inducer treatment with thapsigargin could enhance PRV production. Conversely, ER stress inhibitor treatment with tauroursodeoxycholic acid reduced PRV replication. Taken together, our results reveal that PRV infection induces ER stress and activates the IRE1-XBP1 and eIF2α-ATF4 pathways., (Copyright © 2019 Elsevier B.V. All rights reserved.)

As a key cellular transcription factor that plays a central role in cellular responses to a broad range of stress factors, p53 has generally been considered as a host cell restriction factor for various viral infections. However, the defined roles of p53 in pseudorabies virus (PRV) replication, pathogenesis, and host responses remain unclear. In the present study, we initially constructed a p53 overexpressing a porcine kidney epithelial cell line (PK-15) to detect the effect of p53 on PRV replication in vitro. The results show that viral glycoprotein B (gB) gene copies and the titers of virus were significantly higher in p53 overexpressing PK-15 cells than in PK-15 and p53 inhibitor treated p53 overexpressing PK-15 cells. A similar result was also found in the p53 inhibitor PFT-α-treated PK-15 cells. We then examined the effects of p53 on PRV infection in vivo by using p53-knockout (p53 -/- ) mice. The results show that p53 knockout not only led to significantly reduced rates of mortality but also to reduced viral replication and development of viral encephalitis in the brains of mice following intracranial inoculation. Furthermore, we examined the effect of p53 knockout on the expression of the reported host cell regulators of PRV replication in the brains of mice by using RNA sequencing. The results show that p53 knockout downregulated the interferon (IFN) regulator genes, chemokine genes, and antiviral genes after PRV infection. This finding suggests that p53 positively regulates viral replication and pathogenesis both in vitro and in vivo. These findings offer novel targets of intrinsic host cell immunity for PRV infection.

Previous studies have shown changes in membrane properties of neurons in rat deep cerebellar nuclei (DCN) as a function of development, but due to technical difficulties in obtaining viable DCN slices from adult animals, it remains unclear whether there are learning-related alterations in the membrane properties of DCN neurons in adult rats. This study was designed to record from identified DCN cells in cerebellar slices from postnatal day 25-26 (P25-26) rats that had a relatively mature sensory nervous system and were able to acquire learning as a result of tone-shock eyeblink conditioning (EBC) and to document resulting changes in electrophysiological properties. After electromyographic electrode implantation at P21 and inoculation with a fluorescent pseudorabies virus (PRV-152) at P22-23, rats received either four sessions of paired delay EBC or unpaired stimulus presentations with a tone conditioned stimulus and a shock unconditioned stimulus or sat in the training chamber without stimulus presentations. Compared with rats given unpaired stimuli or no stimulus presentations, rats given paired EBC showed an increase in conditioned responses across sessions. Whole-cell recordings of both fluorescent and nonfluorescent DCN projection neurons showed that delay EBC induced significant changes in membrane properties of evoked DCN action potentials including a reduced after-hyperpolarization amplitude and shortened latency. Similar findings were obtained in hyperpolarization-induced rebound spikes of DCN neurons. In sum, delay EBC produced significant changes in the membrane properties of juvenile rat DCN projection neurons. These learning-specific changes in DCN excitability have not previously been reported in any species or task., Competing Interests: The authors declare no conflict of interest.

Chronic pelvic pain causes significant patient morbidity and is a challenge to clinicians. Using a murine neurogenic cystitis model that recapitulates key aspects of interstitial cystitis/bladder pain syndrome (IC), we recently showed that pseudorabies virus (PRV) induces severe pelvic allodynia in BALB/c mice relative to C57BL/6 mice. Here, we report that a quantitative trait locus (QTL) analysis of PRV-induced allodynia in F2 CxB progeny identified a polymorphism on chromosome 13, rs6314295 , significantly associated with allodynia (logarithm of odds = 3.11). The nearby gene encoding acyloxyacyl hydrolase ( Aoah) was induced in the sacral spinal cord of PRV-infected mice. AOAH-deficient mice exhibited increased vesicomotor reflex in response to bladder distension, consistent with spontaneous bladder hypersensitivity, and increased pelvic allodynia in neurogenic cystitis and postbacterial chronic pain models. AOAH deficiency resulted in greater bladder pathology and tumor necrosis factor production in PRV neurogenic cystitis, markers of increased bladder mast cell activation. AOAH immunoreactivity was detectable along the bladder-brain axis, including in brain sites previously correlated with human chronic pelvic pain. Finally, AOAH-deficient mice had significantly higher levels of bladder vascular endothelial growth factor, an emerging marker of chronic pelvic pain in humans. These findings indicate that AOAH modulates pelvic pain severity, suggesting that allelic variation in Aoah influences pelvic pain in IC.

Emerging pseudorabies virus (PRV) variant has led to frequent outbreaks of PRV infection among Bartha-K61-vaccinated swine population in Chinese swine farms and caused high mortality in pigs of all age since late 2011. Here, we generated a gE/gI-deleted PRV (rPRVXJ-delgI/gE-EGFP) based on PRV variant strain (PRV-XJ) through homologous DNA recombination. Compared to parental strain, rPRVXJ-delgI/gE-EGFP showed similar growth kinetics in vitro. Its safety and immunogenicity were evaluated in weaned piglets. Our results showed that piglets immunized with rPRVXJ-delgI/gE-EGFP did not exhibit any clinical symptoms, and a high level of gB-specific antibody was detected. After lethal challenge with variant PRV (PRV-FJ strain), all vaccinated piglets survived without showing any clinical symptoms except slight fever within 7 days post-challenge. In unvaccinated piglets, typical clinical symptoms of pseudorabies were observed, and the piglets were all died at 5 days post-challenge. These results indicated that a live rPRVXJ-delgI/gE-EGFP vaccine could be a maker vaccine candidate to control the currently epidemic pseudorabies in China.

The experiment was conducted to evaluate the effects of dietary threonine (Thr) supplement on reproductive performance and immune function of the male mice challenged with pseudorabies virus (PRV). Kun-Ming male mice were assigned randomly to four groups with different Thr levels (0.70%, 0.88%, 1.10% and 1.30%). Half of the mice in each group were injected with PRV or phosphate-buffered saline (PBS) after 5 weeks' adaptation to diets. The second experiment examined the effects of dietary Thr level on copulation rate, pregnancy rate and average number per litter of PRV- or PBS-challenged male mice that copulated with adult female mice on the 9th day post PRV challenge. Sperm quality and testosterone of mice were decreased after PRV infection, but this effect was attenuated by increasing Thr levels. Copulation and conception rates were increased with increasing Thr levels (P = 0.14), but litter size was not affected (P > 0.05). In the PBS and PRV groups, mice fed higher levels of Thr had increased immunoglobulin (Ig)G, IgA and IgM concentrations. The PRV-specific antibody level, interleukin (IL)-1β and tumor necrosis factor (TNF)-α concentration in PRV groups enhanced with increasing Thr levels; however, there was no difference in PBS groups. Furthermore, higher toll-like receptor (TLR)2 and TLR9 expressions in testis were observed by PRV challenge compared with PBS groups, and higher Thr supplement attenuated PRV-challenged induced the upregulation effect of TLR2 and TLR9 mRNA expression in testis (P < 0.05). These data suggest that higher Thr consumption was recommended in order to counteract the deleterious effects of virus invasion, possibly through the downregulated expression of TLRs, and thus to improve immunity and reproduction performance of male mice challenged with PRV.

Rabbit eyeblink conditioning is a well characterized model of associative learning. To identify specific neurons that are part of the eyeblink premotor pathway, a retrograde transsynaptic tracer (pseudorabies virus) was injected into the orbicularis oculi muscle. Four time points (3, 4, 4.5, and 5 d) were selected to identify sequential segments of the pathway and a map of labeled structures was generated. At 3 d, labeled first-order motor neurons were found in dorsolateral facial nucleus ipsilaterally. At 4 d, second-order premotor neurons were found in reticular nuclei, and sensory trigeminal, auditory, vestibular, and motor structures, including contralateral red nucleus. At 4.5 d, labeled third-order premotor neurons were found in the pons, midbrain, and cerebellum, including dorsolateral anterior interpositus nucleus and rostral fastigial nucleus. At 5 d, labeling revealed higher-order premotor structures. Labeled fourth-order Purkinje cells were found in ipsilateral cerebellar cortex in cerebellar lobule HVI and in lobule I. The former has been implicated in eyeblink conditioning and the latter in vestibular control. Labeled neurons in anterior interpositus were studied, using neurotransmitter immunoreactivity to classify individual cell types and delineate their interconnectivity. Labeled third-order premotor neurons were immunoreactive for glutamate and corresponded to large excitatory projection neurons. Labeled fourth-order premotor interneurons were immunoreactive for GABA (30%), glycine (18%), or both GABA and glycine (52%) and form a functional network within anterior interpositus involved in modulation of motor commands. These results identify a complete eyeblink premotor pathway, deep cerebellar interconnectivity, and specific neurons responsible for the generation of eyeblink responses.

Replication and transneuronal transport of pseudorabies virus (PRV) are widely used to define the organization of neural circuits in rodent brain. Here we report a dual infection approach that highlights connections to neurons that collateralize within complex networks. The method combines Cre recombinase (Cre) expression from a PRV recombinant (PRV-267) and Cre-dependent reporter gene expression from a second infecting strain of PRV (PRV-263). PRV-267 expresses both Cre and a monomeric red fluorescent protein (mRFP) fused to viral capsid protein VP26 (VP26-mRFP) that accumulates in infected cell nuclei. PRV-263 carries a Brainbow cassette and expresses a red (dTomato) reporter that fills the cytoplasm. However, in the presence of Cre, the dTomato gene is recombined from the cassette, eliminating expression of the red reporter and liberating expression of either yellow (EYFP) or cyan (mCerulean) cytoplasmic reporters. We conducted proof-of-principle experiments using a well-characterized model in which separate injection of recombinant viruses into the left and right kidneys produces infection of neurons in the renal preautonomic network. Neurons dedicated to one kidney expressed the unique reporters characteristic of PRV-263 (cytoplasmic dTomato) or PRV-267 (nuclear VP26-mRFP). Dual infected neurons expressed VP26-mRFP and the cyan or yellow cytoplasmic reporters activated by Cre-mediated recombination of the Brainbow cassette. Differential expression of cyan or yellow reporters in neurons lacking VP26-mRFP provided a unique marker of neurons synaptically connected to dual infected neurons, a synaptic relationship that cannot be distinguished using other dual infection tracing approaches. These data demonstrate Cre-enabled conditional reporter expression in polysynaptic circuits that permits the identification of collateralized neurons and their presynaptic partners.

Background: Pseudorabies virus (PRV) is an alphaherpesviruses whose native host is pig. PRV infection mainly causes signs of central nervous system disorder in young pigs, and respiratory system diseases in the adult., Results: In this report, we have analyzed native host (piglets) gene expression changes in response to acute pseudorabies virus infection of the brain and lung using a printed human oligonucleotide gene set from Illumina. A total of 210 and 1130 out of 23,000 transcript probes displayed differential expression respectively in the brain and lung in piglets after PRV infection (p-value < 0.01), with most genes displaying up-regulation. Biological process and pathways analysis showed that most of the up-regulated genes are involved in cell differentiation, neurodegenerative disorders, the nervous system and immune responses in the infected brain whereas apoptosis, cell cycle control, and the mTOR signaling pathway genes were prevalent in the infected lung. Additionally, a number of differentially expressed genes were found to map in or close to quantitative trait loci for resistance/susceptibility to pseudorabies virus in piglets., Conclusion: This is the first comprehensive analysis of the global transcriptional response of the native host to acute alphaherpesvirus infection. The differentially regulated genes reported here are likely to be of interest for the further study and understanding of host viral gene interactions.

Alpha-herpesviruses, including human herpes simplex virus 1 & 2, varicella zoster virus and the swine pseudorabies virus (PRV), infect the peripheral nervous system of their hosts. Symptoms of infection often include itching, numbness, or pain indicative of altered neurological function. To determine if there is an in vitro electrophysiological correlate to these characteristic in vivo symptoms, we infected cultured rat sympathetic neurons with well-characterized strains of PRV known to produce virulent or attenuated symptoms in animals. Whole-cell patch clamp recordings were made at various times after infection. By 8 hours of infection with virulent PRV, action potential (AP) firing rates increased substantially and were accompanied by hyperpolarized resting membrane potentials and spikelet-like events. Coincident with the increase in AP firing rate, adjacent neurons exhibited coupled firing events, first with AP-spikelets and later with near identical resting membrane potentials and AP firing. Small fusion pores between adjacent cell bodies formed early after infection as demonstrated by transfer of the low molecular weight dye, Lucifer Yellow. Later, larger pores formed as demonstrated by transfer of high molecular weight Texas red-dextran conjugates between infected cells. Further evidence for viral-induced fusion pores was obtained by infecting neurons with a viral mutant defective for glycoprotein B, a component of the viral membrane fusion complex. These infected neurons were essentially identical to mock infected neurons: no increased AP firing, no spikelet-like events, and no electrical or dye transfer. Infection with PRV Bartha, an attenuated circuit-tracing strain delayed, but did not eliminate the increased neuronal activity and coupling events. We suggest that formation of fusion pores between infected neurons results in electrical coupling and elevated firing rates, and that these processes may contribute to the altered neural function seen in PRV-infected animals.

The neuroinvasive property of several alpha-herpesviruses underlies an uncommon infectious process that includes the establishment of life-long latent infections in sensory neurons of the peripheral nervous system. Several herpesvirus proteins are required for replication and dissemination within the nervous system, indicating that exploiting the nervous system as a niche for productive infection requires a specialized set of functions encoded by the virus. Whether initial entry into the nervous system from peripheral tissues also requires specialized viral functions is not known. Here we show that a conserved deubiquitinase domain embedded within a pseudorabies virus structural protein, pUL36, is essential for initial neural invasion, but is subsequently dispensable for transmission within and between neurons of the mammalian nervous system. These findings indicate that the deubiquitinase contributes to neurovirulence by participating in a previously unrecognized initial step in neuroinvasion.

PRV infection causes apoptosis in vitro and in vivo. However, the significance of PRV-induced apoptosis and its signaling pathways is still unknown. This work investigates the role of MAPK pathways in mediating PRV-induced apoptosis. Flow cytometry, apoptosis ELISA and western blotting using antibodies against cleaved caspase-3, -6 and PARP demonstrated that PRV induces apoptosis in a time- and dose-dependent manner. p38 and JNK/SAPK inhibitors significantly protected cells from PRV-induced apoptosis. Inhibitor treatment did not affect Us3a gene transcription and progeny virus production. Western blotting revealed that PRV activates p38 and JNK/SAPK signaling. Inhibition of NF-kappaB had no effect on PRV-mediated apoptosis. Non-replicative PRV failed to activate p38 and JNK/SAPK or induce apoptosis. PRV infection increases TNF-alpha transcription, translation and secretion, as well as TNF-alpha receptor expression. Inhibition of p38 and JNK/SAPK reduced PRV-induced TNF-alpha up-regulation. Neutralization assay confirmed that TNF-alpha is a key mediator involved in PRV-induced apoptosis.

Although it has been reported by several laboratories that vestibular stress activates the hypothalamo-pituitary-adrenocortical axis (HPA), the existence of neuronal connections between vestibular and hypothalamic paraventricular neurons has not yet been demonstrated. By the use of a virus-based retrograde trans-synaptic tracing technique in the rat, here we demonstrate vestibular projections to the paraventricular nucleus (PVN). Pseudorabies virus (Bartha strain, type BDR62) was injected into the PVN, and the progression of the infection along synaptically connected neurons was followed in the pons and the medulla, 3 and 4 days post-inoculation. Virus-infected neurons were revealed mainly in the medial vestibular nucleus. Labeled cells were scattered in the spinal, and very rarely in the superior nuclei, but none of them in the lateral vestibular nucleus. Injections of cholera toxin B subunit, a monosynaptic retrograde tracer into the PVN failed to label any cells in the vestibular nuclei. These results provide anatomical evidence for the existence of a vestibulo-paraventricular polysynaptic pathway and support the view that the HPA axis is modulated by vestibular stress.

Background: Mast cells trigger inflammation that is associated with local pain, but the mechanisms mediating pain are unclear. Interstitial cystitis (IC) is a bladder disease that causes debilitating pelvic pain of unknown origin and without consistent inflammation, but IC symptoms correlate with elevated bladder lamina propria mast cell counts. We hypothesized that mast cells mediate pelvic pain directly and examined pain behavior using a murine model that recapitulates key aspects of IC., Methods and Findings: Infection of mice with pseudorabies virus (PRV) induces a neurogenic cystitis associated with lamina propria mast cell accumulation dependent upon tumor necrosis factor alpha (TNF), TNF-mediated bladder barrier dysfunction, and pelvic pain behavior, but the molecular basis for pelvic pain is unknown. In this study, both PRV-induced pelvic pain and bladder pathophysiology were abrogated in mast cell-deficient mice but were restored by reconstitution with wild type bone marrow. Pelvic pain developed normally in TNF- and TNF receptor-deficient mice, while bladder pathophysiology was abrogated. Conversely, genetic or pharmacologic disruption of histamine receptor H1R or H2R attenuated pelvic pain without altering pathophysiology., Conclusions: These data demonstrate that mast cells promote cystitis pain and bladder pathophysiology through the separable actions of histamine and TNF, respectively. Therefore, pain is independent of pathology and inflammation, and histamine receptors represent direct therapeutic targets for pain in IC and other chronic pain conditions.

Interstitial cystitis (IC) is a chronic bladder inflammatory disease of unknown etiology that is often regarded as a neurogenic cystitis. IC is associated with urothelial lesions, voiding dysfunction, and pain in the pelvic/perineal area, and diet can exacerbate IC symptoms. In this study, we used a murine neurogenic cystitis model to investigate the development of pelvic pain behavior. Neurogenic cystitis was induced by the injection of Bartha's strain of pseudorabies virus (PRV) into the abductor caudalis dorsalis tail base muscle of female C57BL/6J mice. Infectious PRV virions were isolated only from the spinal cord, confirming the centrally mediated nature of this neurogenic cystitis model. Pelvic pain was assessed using von Frey filament stimulation to the pelvic region, and mice infected with PRV developed progressive pelvic pain. Pelvic pain was alleviated by 2% lidocaine instillation into either the bladder or the colon but not following lidocaine instillation into the uterus. The bladders of PRV-infected mice showed markers of inflammation and increased vascular permeability compared with controls. In contrast, colon histology was normal and vascular permeability was unchanged, suggesting that development of pelvic pain was due only to bladder inflammation. Bladder-induced pelvic pain was also exacerbated by colonic administration of a subthreshold dose of capsaicin. These data indicate organ cross talk in pelvic pain and modulation of pain responses by visceral inputs distinct from the inflamed site. Furthermore, these data suggest a mechanism by which dietary modification benefits pelvic pain symptoms.

Ba-DupGreen (BDG) is a highly attenuated, Bartha-derived pseudorabies virus (PRV) expressing green fluorescent protein (GFP) with immediate-early kinetics. Innate immune mechanisms underlying the low infectivity of the virus and the disappearance of infected neurons from the brain were studied at cellular level following injection of BDG into the spleen. The temporal shift in the expression between GFP and viral structural proteins allowed us to discriminate three stages of viral infection in the compromised neurons in correlation with the ongoing local inflammatory response. Iba1/lectin/OX42-positive microglia were recruited to infected neurons within 4-6 h following the initiation of virus replication, incorporated BrdU, isolated the infected cells before the disintegration of their membranes and phagocytosed collapsed neurons. Ex vivo-labeled blood and bone marrow-derived leukocytes, including ED-1-positive macrophages were involved in the immune cell assembly around compromised neurons, which resulted in the complete clearance of infected neurons from the early-infected brain regions.

Neurotropism is a distinctive feature of members of the Alphaherpesvirinae. However, its molecular basis remains enigmatic. In the past, research has been focused mainly on the role of viral envelope proteins in modulating herpesvirus neuroinvasion and neurovirulence (T. C. Mettenleiter, Virus Res. 92:192-206, 2003). To further analyze the molecular requirements for neuroinvasion of the alphaherpesvirus pseudorabies virus (PrV), adult mice were infected intranasally with a set of single- or multiple-deletion mutants lacking the UL3, UL4, UL7, UL11, UL13, UL16, UL17, UL21, UL31, UL34, UL37, UL41, UL43, UL46, UL47, UL48, UL51, US3, US9, glycoprotein E (gE), gM, UL11/US9, UL11/UL16, UL16/UL21, UL11/UL16/UL21, UL11/gE, UL11/gM, UL43/gK, UL43/gM, or UL43/gK/gM genes. Neurovirulence was evaluated by measuring mean survival times compared to that after wild-type virus infection. Furthermore, by immunohistochemical detection of infected neurons, the kinetics of viral spread in the murine central nervous system was investigated.

Mammalian alphaherpesviruses normally establish latent infections in ganglia of the peripheral nervous system in their natural hosts. Occasionally, however, these viruses spread to the central nervous system (CNS), where they cause damaging, often fatal, infections. Attenuated alphaherpesvirus derivatives have been used extensively as neuronal circuit tracers in a variety of animal models. Their circuit-specific spread provides a unique paradigm to study the local and global CNS response to infection. Thus, we systematically analyzed the host gene expression profile after acute pseudorabies virus (PRV) infection of the CNS using Affymetrix GeneChip technology. Rats were injected intraocularly with one of three selected virulent and attenuated PRV strains. Relative levels of cellular transcripts were quantified from hypothalamic and cerebellar tissues at various times postinfection. The number of cellular genes responding to infection correlated with the extent of virus dissemination and relative virulence of the PRV strains. A total of 245 out of 8,799 probe sets, corresponding to 182 unique cellular genes, displayed increased expression ranging from 2- to more than 100-fold higher than in uninfected tissue. Over 60% thereof were categorized as immune, proinflammatory, and other cellular defense genes. Additionally, a large fraction of infection-induced transcripts represented cellular stress responses, including glucocorticoid- and redox-related pathways. This is the first comprehensive in vivo analysis of the global transcriptional response of the mammalian CNS to acute alphaherpesvirus infection. The differentially regulated genes reported here are likely to include potential diagnostic and therapeutic targets for viral encephalitides and other neurodegenerative or neuroinflammatory diseases.

Aim: To examine the effect of acute infection caused by herpesvirus (pseudorabies virus, PRV) on pancreatic ductal secretion., Methods: The virulent Ba-DupGreen (BDG) and non-virulent Ka-RREp0lacgfp (KEG) genetically modified strains of PRV were used in this study and both of them contain the gene for green fluorescent protein (GFP). Small intra/interlobular ducts were infected with BDG virus (10(7) PFU/mL for 6 h) or with KEG virus (10(10) PFU/mL for 6 h), while non-infected ducts were incubated only with the culture media. The ducts were then cultured for a further 18 h. The rate of HCO(3)(-) secretion (base efflux -J(B-)) was determined from the buffering capacity of the cells and the initial rate of intracellular acidification (1) after sudden blockage of basolateral base loaders with dihydro-4,4-diisothiocyanatostilbene-2,2-disulfonic acid (500 micromol/L) and amiloride (200 micromol/L), and (2) after alkali loading the ducts by exposure to NH(4)Cl. All the experiments were performed in HCO(3)(-)-buffered Ringer solution at 37 degrees (n = 5 ducts for each experimental condition). Viral structural proteins were visualized by immunohistochemistry. Virally-encoded GFP and immunofluorescence signals were recorded by a confocal laser scanning microscope., Results: The BDG virus infected the majority of accessible cells of the duct as judged by the appearance of GFP and viral antigens in the ductal cells. KEG virus caused a similarly high efficiency of infection. After blockage of basolateral base loaders, BDG infection significantly elevated -J(B-) 24 h after the infection, compared to the non-infected group. However, KEG infection did not modify -J(B-). After alkali loading the ducts, -J(B-) was significantly elevated in the BDG group compared to the control group 24 h after the infection. As we found with the inhibitor stop method, no change was observed in the group KEG compared to the non-infected group., Conclusion: Incubation with the BDG or KEG strains of PRV results in an effective infection of ductal epithelial cells. The BDG strain of PRV, which is able to initiate a lytic viral cycle, stimulates HCO(3)(-) secretion in guinea pig pancreatic duct by about four- to fivefold, 24 h after the infection. However, the KEG strain of PRV, which can infect, but fails to replicate, has no effect on HCO(3)(-) secretion. We suggest that this response of pancreatic ducts to virulent PRV infection may represent a defense mechanism against invasive pathogens to avoid pancreatic injury.

Increased density of catecholaminergic nerves in the human polycystic ovary has been observed. The aim of the present study was to investigate the distribution of transsynaptically virus-labeled neurons in the central nervous system from the rat polycystic ovary to see whether is it different or not from that of cycling control rats. To induce a polycystic ovary, a single injection of estradiol valerate was given to adult female rats and 30 days later a neurotropic virus was injected into the right ovary. Rats were sacrificed 72 or 96 hours after viral infection. Weight of the ovaries of the estradiol valerate-treated rats was significantly lower compared to controls, and the histology of the ovaries of the treated rats displayed severely atretic large antral follicles. There was almost no viral labeling in the central nervous system from the ovaries showing precystic morphology, in spite of the fact that such altered organs are rich in nerve fibres. It is assumed that presently unidentified factors in the precystic ovary, presumably related to the link between the immune and the nervous system, might be involved in the infectivity of the virus, and thus be responsible for the lack of viral labeling from such an ovary.

Intraocular injection of the Bartha strain of pseudorabies virus (PRV Bartha) results in transsynaptic infection of the hypothalamic suprachiasmatic nucleus (SCN), a retinorecipient circadian oscillator. PRV Bartha infection of a limited number of retinorecipient structures, including the SCN, was initially interpreted as the differential infection of a subpopulation of rat retinal ganglion cells, followed by replication and anterograde transport via the optic nerve. A recent report that used a recombinant strain of PRV Bartha (PRV152) expressing enhanced green fluorescent protein demonstrated that SCN infection actually results from retrograde transneuronal transport of the virus via the autonomic innervation of the eye in the golden hamster. In the present study using the rat, the pattern of infection after intravitreal inoculation with PRV152 was examined to determine if infection of the rat SCN is also restricted to retrograde transsynaptic transport. It was observed that infection in preganglionic autonomic nuclei (i.e., Edinger-Westphal nucleus, superior salivatory nucleus, and intermediolateral nucleus) precedes infection in the SCN. Sympathetic superior cervical ganglionectomy did not abolish label in the SCN after intraocular infection, nor did lesions of parasympathetic preganglionic neurons in the Edinger-Westphal nucleus. However, combined Edinger-Westphal nucleus ablation and superior cervical ganglionectomy eliminated infection of the SCN. This observation allowed a detailed examination of the SCN contribution to descending autonomic circuits afferent to the eye. The results indicate that in the rat, as in the hamster, SCN infection after intraocular PRV152 inoculation is by retrograde transsynaptic transport via autonomic pathways to the eye., (Copyright 2004 Wiley-Liss, Inc.)

Pseudorabies virus (PrV) is a neurotropic alphaherpesvirus that, after intranasal infection of adult mice, enters peripheral neurons and propagates to the central nervous system. In recent years we have analyzed the contribution of virus-encoded glycoproteins to neuroinvasion and transneuronal spread (reviewed in T. C. Mettenleiter, Virus Res. 92:197-206, 2003). We now extend our studies to analyze the role of tegument proteins in these processes. To this end, PrV mutants unable to express the UL11, UL37, UL46, UL47, and UL48 tegument proteins, as well as the corresponding rescued viruses, were intranasally instilled into 6- to 8-week-old CD1 strain mice. First, mean survival times were determined which showed that mice infected with the UL46 deletion mutant succumbed to the disease as early as wild-type PrV-infected animals. Survival times increased in the order: PrV-DeltaUL47-, PrV-DeltaUL11-, and PrV-DeltaUL48-infected animals, a finding which parallels the growth phenotype of these viruses in cell culture. In contrast, none of the PrV-DeltaUL37-infected animals died. Upon closer histological examination, all viruses except PrV-DeltaUL37 were able to infect the nasal cavity and propagate to first- and second-order neurons as shown by two-color immunofluorescence. However, neuroinvasion was delayed in PrV-DeltaUL47, PrV-DeltaUL11, and PrV-DeltaUL48, a finding that correlated with the extended survival times. Surprisingly, whereas PrV-DeltaUL48 and PrV-DeltaUL37 replicated to similar titers in cell culture which were approximately 500-fold lower than those of wild-type virus, after intranasal infection of mice PrV-DeltaUL48 was able to infect areas of the brain like wild-type PrV, although only after a considerably longer time period. In contrast, PrV-DeltaUL37 was not able to enter neurons and was restricted to the infection of single cells in the nasal respiratory epithelium. Thus, our data demonstrate the importance of herpesviral tegument proteins in neuronal infection and show a different contribution of tegument proteins to the neuroinvasion phenotype of a neurotropic alphaherpesvirus.

Pseudorabies virus was used to label transneuronally descending auditory projections following intracochlear injections. At different time points after injection, virus-infected cells were detected immunohistochemically in the central nervous system. Initially (25 h), virus was transported retrogradely to olivocochlear cells in the pons. At 32-72 h after injection, labelling occurred in higher order auditory brainstem nuclei as well as in the locus coeruleus and pontine dorsal raphe. At 90-108 h, virus-infected neurons were found bilaterally in the medial geniculate body and in layer V of the auditory cortex. Viral transneuronal labelling in the auditory cortex after intracochlear application confirms the existence of a continuous descending chain of neurons from the auditory cortex to the cochlea, via the medial and lateral olivocochlear systems. The transneuronal labelling of the locus coeruleus and pontine dorsal raphe suggests that noradrenergic and serotonergic inputs may substantially influence the activity of olivocochlear cells, and thus the cochlea.

Glycoprotein C (gC) of pseudorabies virus, a swine herpesvirus, initiates virus attachment by binding to heparan sulfate (HS) linked to proteoglycans (HSPGs) on the cell surface. This interaction facilitates a required step in virus entry, the binding to a non-HS coreceptor, likely by another viral glycoprotein, gD. We demonstrate that gC has an even more direct role in virus entry than simply promoting adhesion strengthening. A porcine cell line expressing gC trans-complemented the penetration, but not attachment, defect of gC null mutants. In addition, gC promoted the colocalization of cell surface HSPGs and the actin cytoskeleton, suggesting a role for filamentous actin in virus entry. This was supported by results showing that both the engagement of a non-HS coreceptor and entry events subsequent to coreceptor binding were impaired if cells were first treated with an actin depolymerizing agent, cytochalasin D. Our results suggest a model in which gC-HS interactions promote not only virus attachment but also virus entry by usurping the normal properties of HSPGs.

Transneuronal tracing of neuronal circuitry with neurotropic viruses has provided valuable insights in the way in which the nervous system imposes temporal organization on physiological processes and behavior. The swine alpha herpes virus known as pseudorabies virus, or PRV, has been particularly useful in this regard. Early studies identified attenuated mutants with selective tropism for visual circuitry involved in circadian regulation, and subsequent experiments employing this virus have provided considerable insight into the polysynaptic organization of the suprachiasmatic nuclei and associated circuitry. This literature, which has emerged during the past decade, is the subject of this mini review.

Frequent blood sampling via intraatrial cannula revealed daily rhythms of TSH and thyroid hormones in both male and female Wistar rats. Thermic ablation of the biological clock, i.e. the suprachiasmatic nucleus (SCN), eliminated the diurnal peak in circulating TSH and thyroid hormones. In addition, SCN lesions produced a clear decrease of 24-h mean T4 concentrations. A more pronounced effect of SCN-lesions on thyroid hormones, as opposed to TSH, suggested routes of SCN control additional to the neuroendocrine hypothalamopituitary-thyroid axis. Retrograde, transneuronal virus tracing was used to identify the type and localization of neurons in the central nervous system that control the autonomic innervation of the thyroid gland. In the spinal cord and brain stem, both the sympathetic and parasympathetic motorneurons were labeled. By varying the postinoculation survival time, it was possible to follow the viral infection as it proceeded. Subsequently, the pseudorabies virus (PRV) infected neurons in several brain stem cell groups, the paraventricular nucleus of the hypothalamus (PVN) and the central nucleus of the amygdala (second order labeling). Among PRV-infected neurons in the PVN were TRH-containing cells. Third order neurons were found in several hypothalamic cell groups, among which was the SCN. Therefore, we propose that the SCN has a dual control mechanism for thyroid activity by affecting neuroendocrine control of TSH release on the one hand and the autonomic input to the thyroid gland on the other.

Objective: To compare serologic testing with slaughter evaluation in assessing effects of subclinical infection on average daily weight gain (ADG) in pigs., Design: Cohort study., Animals: 18 cohorts (30 to 35 pigs/cohort) of pigs on/farms., Procedure: Blood samples were collected, and pigs were weighed at 8, 16, and 24 weeks of age. Sera were tested for antibodies to porcine reproductive and respiratory syndrome virus (PRRSV), swine influenza virus (SIV), transmissible gastroenteritis virus (TGEV), pseudorabies virus, Mycoplasma hyopneumoniae, and Actinobacillus pleuropneumoniae. At slaughter, skin, nasal turbinates, lungs, and liver were examined. Associations between ADG and results of serologic testing and slaughter evaluation were examined by use of multiple linear regression., Results: Pathogens that had a significant effect on any given farm during any given year and the magnitude of that effect varied. However, at 16 and 24 weeks of age, a higher antibody titer was consistently associated with a lower ADG. Mean differences in ADG between seropositive and seronegative pigs were 18 g/d (0.04 lb/d) for SIV, 40 g/d (0.09 lb/d) for PRRSV, 38 g/d (0.08 lb/d) for M hyopneumoniae, and 116 g/d (0.26 lb/d) for TGEV. Of the evaluations performed at slaughter, only detection of lung lesions was consistently associated with a decrease in ADG., Conclusions and Clinical Relevance: Results suggest that subclinical infection with any of a variety of pathogens commonly found in swine herds was associated with a decrease in ADG. Serologic testing was more effective than slaughter evaluation in assessing the impact of subclinical infection on ADG in these pigs.

The suprachiasmatic nucleus of the hypothalamus is responsible for a 24-h rhythm in basal glucose levels in the rat. The neural pathways used by the suprachiasmatic nucleus to mediate this rhythm in plasma glucose have not yet been identified. In the present study we examined whether there are any connections between hypothalamic centers, including the suprachiasmatic nucleus, and the liver, which is the main site for glucose production and storage. Transneuronal virus tracing from the liver showed that after injection of pseudorabies virus, specific neuronal cell populations in the central nervous system were labeled retrogradely, suggesting that specific sites in the central nervous system may control liver metabolism. First-order neurons belonged to the sympathetic and parasympathetic system, while second-order and third-order neurons were present in both the brainstem and hypothalamus. The presence of third-order neurons in the suprachiasmatic nucleus suggests an involvement of the biological clock in the neural control of the liver.

Expression of the latency-associated transcript (LAT) gene is a hallmark of alphaherpesvirus latency, and yet its control and function remain an enigma. Resolution of this problem will require verification and subsequent elimination or disabling of elements regulating LAT gene transcription so that the influence of the resultant RNA can be evaluated. Toward this end, we generated a novel pseudorabies virus (PrV) recombinant in which a 282-bp region containing the LAP1 (first latency-active promoter) consensus sequence was replaced by a reporter cassette. Despite this substitution, replication of the recombinant was comparable to that of the parental and rescuant viruses both in cultured mammalian cells and in the natural host, swine. Furthermore, production of the LAT gene-associated 2.0- and 8.0-kb RNAs during an in vitro lytic infection of cultured neuronal cells was unaffected. However, the otherwise constitutively produced and processed 8.4-kb LAT was not detected in porcine trigeminal ganglia latently infected with this novel recombinant, although the viral genome was shown to be present. Therefore, LAP1 is apparently the basal promoter for PrV LAT gene expression during viral latency but is not required for such activity during an in vitro lytic infection of neuronal cells. More importantly, the ability of PrV to persist in a latent state in the absence of LAT suggests that other factors are responsible for this event in the natural host.

Barrington's nucleus (BN) has been considered a pontine center related exclusively to the control of pelvic parasympathetic activity. The present study demonstrates an anatomical linkage between BN and autonomic outflow to visceral targets innervated exclusively by the sympathetic division of the autonomic nervous system. Temporal analysis of infection after injection of pseudorabies virus (PRV), a retrograde transynaptic tracer, into two sympathetically innervated organs, the spleen and the kidney, revealed the presence of infected neurons in BN at early post-inoculation survival intervals. Immunohistochemical localization of PRV after spleen injections showed that a small subpopulation of BN neurons became labeled in a time frame coincident with the appearance of infected neurons in other brain regions known to project to sympathetic preganglionic neurons (SPNs) in the thoracic spinal cord; a larger number of infected neurons appeared in BN at intermediate intervals after PRV injections into the spleen or kidney. Coinjection of the retrograde tracer Fluoro-Gold i.p. and PRV into the spleen demonstrated that parasympathetic preganglionic neurons in the caudal medulla or lumbo-sacral spinal cord were not infected, indicating that infected BN neurons were not infected via a parasympathetic route. Thus, BN neurons become infected after PRV injections into the spleen or kidney either directly through BN projections to SPNs, or secondarily via BN projections to infected pre-preganglionic neurons. These results demonstrate an anatomical linkage, either direct or indirect, between BN and sympathetic activity. Because BN receives numerous inputs from diverse brain regions, the relation of BN with both branches of the autonomic nervous system suggests that this nucleus might play a role in the integration of supraspinal inputs relevant to the central coordination of sympathetic and parasympathetic activity.

We present a model of neurogenic cystitis induced by viral infection of specific neuronal circuits of the rat CNS. Retrograde infection by pseudorabies virus (PRV) of neuronal populations neighboring those that innervate the bladder consistently led to a localized immune response in the CNS and bladder inflammation. Infection of bladder circuits themselves or of circuits distant from these rarely produced cystitis. Absence of virus in bladder and urine ruled out an infectious cystitis. Total denervation of the bladder, selective C-fiber deafferentation, or bladder sympathectomy prevented cystitis without affecting the CNS disease, indicating a neurogenic component to the inflammation. The integrity of central bladder-related circuits is necessary for the appearance of bladder inflammation, because only CNS lesions affecting bladder circuits, i.e., bilateral dorsolateral or ventrolateral funiculectomy, as well as bilateral lesions of Barrington's nucleus/locus coeruleus area, prevented bladder inflammation. The close proximity in the CNS of noninfected visceral circuits to infected somatic neurons would thus permit a bystander effect, leading to activation of the sensory and autonomic circuits innervating the bladder and resulting in a neurogenic inflammation localized to the bladder. The present study indicates that CNS dysfunction can bring about a peripheral inflammation.

Retrograde tract tracing studies have indicated that dorsal root ganglion cells from T8 to L2 innervate the rat's left kidney. Electrophysiology studies have indicated that putative second-order sympathetic afferents are found in the dorsal horn at spinal segments T10 to L1 in laminae V-VII. Here, the spread of pseudorabies virus through renal sensory pathways was examined following 2-5 days post-infection (PI) and the virus was located immunocytochemically using a rabbit polyclonal antibody. Two days PI, dorsal root ganglion neurons (first-order sympathetic afferents) were infected with PRV. An average of 1.2, 0.8, 2.1 and 4.4% of the infected dorsal root ganglion neurons were contralateral to the injected kidney at spinal segments T10, T11, T12 and T13, respectively. Four days PI, infected neurons were detected within laminae I and II of the dorsal horn of the caudal thoracic and upper lumbar spinal cord segments. The labeling patterns in the spinal cord are consistent with previous work indicating the location of renal sympathetic sensory pathways. The nodose ganglia were labeled starting 4 days PI, suggesting the involvement of parasympathetic sensory pathways. Five days PI, infected neurons were found in the nucleus tractus solitarius. In the present study, it was unclear whether the infected neurons in the nucleus tractus solitarius are part of sympathetic or parasympathetic afferent pathways or represent a convergence of sensory information. Renal denervation prevented the spread of the virus into the dorsal root ganglia and spinal cord. Sectioning the dorsal roots from T10-L3 blocked viral spread into the spinal cord dorsal horn, but did not prevent infection of neurons in dorsal root ganglion nor did it prevent infection of putative preganglionic neurons in the intermediolateral cell column. The present results indicated that renal afferent pathways can be identified after pseudorabies virus infection of the kidney. Our results suggest that renal afferents travel in sympathetic and parasympathetic nerves and that this information may converge at the NTS., (Copyright 1998 Elsevier Science B.V.)

The development of neurotrophic alpha herpesviruses for transneuronal analysis of neuronal circuitry has emerged from interdisciplinary characterizations of the viral life cycle and the defense response mounted by the nervous system to contain and eliminate the infection. Important findings from a number of fields have combined to provide compelling evidence that these viruses, when used appropriately, are powerful probes of multisynaptic circuits. These studies have also revealed that a number of variables can influence the outcome of infection and should be considered in designing and interpreting data derived from studies employing this experimental approach. The purpose of this paper is to review the literature that has established this experimental approach as a viable method for transynaptic analysis of neuronal circuitry and to define the factors that should be considered in applying this technology.

Neurones situated in the lamina terminalis (organum vasculosum of the lamina terminalis, median preoptic nucleus and subfornical organ) as well as within medial and lateral parts of the preoptic area and in the insular cortex become transneuronally labelled following pseudorabies virus injections into the submandibular or the sublingual gland. These neurones are efferently connected to a chain of central neurones directed to secretory or vascular tissue of the submandibular or the sublingual gland. By varying the postinoculation time a stepwise infection of different forebrain nuclei was registered, with the hypothalamic paraventricular nucleus and the lateral hypothalamic area being the first forebrain structures labelled. Such early infected neurones within these hypothalamic nuclei are in all likelihood third order neurones regulating salivary secretion and might have functioned as relays transmitting virus to other forebrain structures. The above mentioned forebrain areas together with several other hypothalamic nuclei as well as the bed nucleus of the stria terminalis, the central nucleus of the amygdala and the substantia innominata, seem to be the widespread anatomical basis for the central regulation of salivary gland function., (Copyright 1998 Elsevier Science B.V.)

The presence of Aujeszky's disease virus (ADV) in peripheral blood mononuclear cells (PBMC) and tissues of experimentally infected pigs was studied. Vaccinated and unvaccinated pigs were inoculated with different doses of Aujeszky's disease NIA-3 strain. Pigs were periodically bled and PBMC were used for virus isolation and PCR detection of virus. Tissues were obtained at the time of death (8 weeks post-inoculation) and used for ADV genome detection by PCR. ADV genome was amplified from PBMC during the acute phase of infection and, in some experimental groups, up to 38 days post-inoculation (PI). The virus was sporadically detected by virus isolation performed from PBMC. In neural tissues, ADV was constantly amplified from the trigeminal ganglia and the olfactory bulb of persistently infected pigs (euthanized 8 weeks PI). In other tissues, the viral genome was rarely detected in lymph nodes and tonsils, and occasionally, in the bone marrow. Our results indicated that PBMC are not an appropriate source for detecting ADV persistence, since inconsistent results were obtained throughout the experiments. In neural tissues, the olfactory bulb turned out to be as important a target for ADV persistence as the trigeminal ganglia. Viral genome detection in the bone marrow indicated that this tissue may play a role in the establishment of a persistent infection.

To determine whether pseudorabies virus (PRV) infection increases the severity of pneumonia by Mycoplasma hyopneumoniae, 18, 10-week-old Cesarean-derived, colostrum-deprived pigs were randomly assigned to 3 groups of 6 pigs each. Pigs in groups A and C were inoculated intranasally with M. hyopneumoniae at 10-week-old. At 11-week-old, pigs in groups B and C were inoculated intranasally with PRV. All pigs were initially seronegative for M. hyopneumoniae and PRV. Three pigs of each group were euthanized at 12-week-old, and remaining pigs at 14-week-old. At necropsy, gross lesions in the lung were observed in the pigs of groups A and C. On post-inoculation-week (PIW) 2 with M. hyopneumoniae (at 12-week-old), lung lesions were recognized in one of the 3 pigs in group A and all the pigs in group C. The mean percentage of the lung lesions were 0.1% in group A and 9.8% in group C. M. hyopneumoniae was isolated from broncho-alveolar lavage fluids (BALF) of pigs in group A with titer of 10(2) to 10(3) CCU/0.2 ml and in group C with titer of 10(5) to 10(6) CCU/0.2 ml. On PIW 4 (at 14-week-old), lung lesions were observed in all the pigs in groups A and C, and the mean percentage of the lung lesions were 8.3% in group A and 17.2% in group C. M. hyopneumoniae was isolated from BALF in group A with titer of 10(4) to 10(7) CCU/0.2 ml and in group C with titer of 10(6) to 10(7) CCU/0.2 ml. PRVs were isolated from nasal swab and tissue samples in groups B and C. After inoculation, antibody against M. hyopneumoniae was detected in groups A and C, and against PRV in groups B and C. Under the present experimental conditions, PRV infection appear to have effect on the severity of experimentally induced acute mycoplasmal pneumonia in young pigs.

Dysfunction of parasympathetic command neurons may be a cause of cardiac autonomic imbalance, which has been implicated as a pathogenic mechanism of lethal arrhythmias. The locations in the brain of these command neurons are not known. The aim of this investigation is to identify selectively the parasympathetic command neurons in the forebrain. Male Wistar rats were inoculated in the left ventricular myocardium with 2 ml of a 3 x 10(6) plaque-forming units/ml of a pseudorabies virus (PRV)-Bartha solution. Eighteen hours after the infection, the spinal cord was transected at T1. Six of fourteen rats showed PRV-immunoreactive cells in the forebrain after 6 postoperative survival days. Bilaterally, the infections were located in the prelimbic, anterior cingulate, frontal, and insular cortexes, various hypothalamic and midbrain nuclei, the nucleus of the solitary tract, the dorsal motor vagus, and periambiguus nuclei. Control animals receiving intravenous PRV-Bartha injections were not infected. Using transneuronal retrograde viral labeling and spinal cord transection, we were able to localize the forebrain parasympathetic command neurons that maintain cardiac autonomic balance. The virus-infected cells were localized in regions that previously showed susceptibility for immune activation-mediated selective cerebral endothelial leakage. We hypothesize that such selective endothelial leakage could induce autonomic imbalance after myocardial infarction.

Latency is a characteristic and fascinating part of the biology of alphaherpesvirinae, including ADV. Tissue explanation, blot hybridization, in situ hybridization and more recently PCR are the experimental methods used to demonstrate that latent infections consistently occur in ganglionic neurons and, at a lower level, in tonsillar and possibly other cells. In vivo reactivation of ADV, resulting in shedding of virulent ADV, has been demonstrated experimentally following administration of high doses of corticosteriods. To determine the influence of vaccination with currently used gene deleted vaccines on field virus latency load, it is essential to use quantitative latency detection methods. We have developed chemiluminescence-based quantitative PCR assays specific for gG and gE, and are currently using these to determine field virus latency loads in tissues of pigs vaccinated with one of several gene deleted vaccines. Recombination between ADV strains has been demonstrated both in vitro and in vivo and has raised concerns about the generation of gene deleted virulent ADV strains. Recent studies in a mouse model have shown that high concentrations of both strains have to be present at the same anatomical site for recombination to take place. This led to the conclusion that ongoing ADV eradication programs, based upon the use of gene deleted vaccines and differential serological testing, are not likely to be threatened by recombination between virulent ADV and gene deleted vaccine strains.

In the present review, the interaction of Aujeszky's disease (pseudorabies) virus (ADV) with individual susceptible cells and the entire host is presented. Special emphasis is put on how viral envelope glycoproteins control invasion and virulence. Furthermore, the importance of envelope glycoproteins in the induction of a protective immunity is discussed.

Eight Mink (Mustela vison) were inoculated orally with Aujeszky's disease virus (ADV). Three mink were killed at the onset of clinical signs and the other mink died spontaneously after inoculation. The incubation period ranged from 72 to 96 hours and was followed by a short illness characterised by increasing salivation, vomiting and retching, depression and coma. Microscopically, lesions were confined to the brain stem and consisted of a discrete non-suppurative encephalitis. Viral antigen was detected by an immunoperoxidase technique predominantly in association with specific lesions, although sometimes it was found within non-altered areas in the brain stem. Virus isolation confirmed the presence of ADV in the central nervous system. Fibrinoid degeneration of vessel walls was present in pharynx, larynx and myocardium in association with haemorrhages. Microthrombi were observed in heart and brain.

A NYVAC vaccinia vector containing genes for pseudorables virus glycoproteins gII and gp50 was administered to pigs to determine if it would have a greater protective effect than a vector containing the gene for gp50 alone. Both NYVAC vectors protected pigs similarly from virulent pseudorabies virus challenge.

Pseudorabies virus (PRV) is a neurotropic herpesvirus of swine. Previously, we described construction of a recombinant strain of PRV (LLT beta delta 2) which contains a 3.0-kb deletion spanning the junction of the unique long and internal repeat sequences. Compared to the parental strain, Indiana-Funkhauser, and a virus rescued for the deleted sequences (LLT beta res), LLT beta delta 2 replicated efficiently at the site of inoculation, yet exhibited significantly reduced virulence when inoculated intranasally in pigs. In this report, we investigated the effect of the deletion on PRV replication and virulence after intracranial inoculation of swine, in comparison to replication and virulence after intranasal inoculation, in order to more precisely locate the defect in LLT beta delta 2. Four-day-old pigs were infected intranasally with LLT beta delta 2 or LLT beta res and necropsied at various times postinfection. Compared to LLT beta res-infected pigs, tissue distribution of virus, PRV antigen, and lesions of LLT beta delta 2-infected pigs were comparable in all peripheral tissues examined, including trigeminal ganglia, but were reduced in tissues from the central nervous system (CNS). LLT beta delta 2 was able to replicate in the CNS after intracranial inoculation into the cerebral cortex of 2-day-old piglets and to spread from CNS to peripheral tissues. Neurovirulence of LLT beta delta 2 was somewhat reduced, as demonstrated by delayed onset of neurological signs and death in intracranially inoculated pigs. These results indicate that decreased neurovirulence after intranasal inoculation is not due to inability of LLT beta delta 2 to replicate in CNS tissues. The difference in the amount of antigen detected in CNS tissues after intracranial inoculation compared to intranasal inoculation suggests that one defect in LLT beta delta 2 is reduced ability to spread from peripheral neurons to the CNS after intranasal inoculation.

In this study we quantified the transmission of pseudorabies virus (PRV) in well-immunized sow herds in The Netherlands. In three herds, sows were tested for antibodies to gE of PRV every time after they had been transported to another barn (survey A). In 99 other herds, sows were tested simultaneously once or twice yearly (survey B). We observed six introductions in survey A and 53 in survey B. None of these introductions resulted in extensive spread of the virus. The reproduction ratio R, which is defined as the mean number of secondary infections caused by one infectious sow, was significantly less than one. We conclude that PRV can be eliminated from sow herds by vaccination.

Objective: To compare the sensitivities of all available serologic tests in detecting pseudorabies virus (PRV) antibodies in pigs during long-term latent pseudorabies., Design: Pigs experimentally infected with a virulent strain of PRV were maintained for 2 to 27 months after inoculation. At the time of necropsy of each pig, blood was collected for serologic evaluation, and tissues were obtained for polymerase chain reaction (PCR) verification of latency., Animals: 65 crossbred pigs each weighing approximately 18 kg at the start of the study., Procedure: Serum samples from each pig were analyzed by serum neutralization, latex agglutination, screening ELISA, particle concentration fluorescence immunoassay, automated latex agglutination, and differential ELISA for glycoproteins I, III, and X. DNA was extracted from the trigeminal ganglia and tonsils of each pig and was analyzed by PCR for PRV genomic sequences., Results: PCR analysis of trigeminal ganglia and tonsils indicated that all pigs were latently infected with PRV at the time of necropsy, and serologic testing verified that all pigs had PRV-specific antibodies, regardless of duration of infection. The screening tests were virtually equivalent in sensitivity for detection of PRV antibodies. Of the differential serologic tests, the glycoprotein-I and -III marker systems, which performed with similar sensitivity as screening tests, were superior to the glycoprotein-X marker system in detecting PRV antibodies in latently infected pigs., Conclusion: Serologic testing consistently detects pigs in the latent phase of PRV infection, provided that the test detects the antibody response to the whole virus or to a reliable PRV-marker glycoprotein.

On three consecutive days, six pigs were exposed for 15 minutes to aerosols of Aujeszky's disease virus. The total estimated dose was 4.5 log 10 TCID50. Within each isolation room, a sentinel pig was placed on a deck two feet away from the infected pig. The breath of the pigs that had inhaled the aerosols was collected on days 3, 7 and 13. The respiratory and other clinical signs of the infected pigs resembled those in field cases of Aujeszky's disease. All the pigs infected with Aujeszky's disease virus seroconverted within seven to 10 days after infection. Among the sentinel pigs, clinical signs were minimal and only three seroconverted.

The pathogenicity of a double mutant of pseudorabies virus (PRV) with deletions in the latency gene and the early protein O gene was examined. In comparison to the parent Indiana-Funkhauser virus, the ability of this mutant to replicate and to cause disease in piglets is greatly reduced. At an infection dose that caused no clinical signs in 5-day-old neonatal piglets, this mutant was capable of eliciting solid protective immunity against a lethal PRV challenge. Thus, the double-gene deletion attenuates PRV but does not affect its immunogenicity. These features may be desirable for inclusion into future PRV vaccines.