Classical swine fever virus inhibits nitric oxide production in infected macrophages

Tear metabolomics reveals novel potential biomarkers in epithelial herpes simplex keratitis

BACKGROUND

Herpes simplex keratitis (HSK) is a recurrent inflammatory disease of cornea primarily initiated by type I herpes simplex virus infection of corneal epithelium. However, early diagnosis of HSK remains challenging due to the lack of specific biomarkers. This study aims to identify biomarkers for HSK through tear metabolomics analysis between HSK and healthy individuals.

METHODS

We conducted a cross-sectional study enrolling 33 participants. Tear samples were collected from one eye of 18 HSK patients and 15 healthy volunteers using Schirmer-strips. Tear metabolomic profiling was performed using high-performance liquid chromatography tandem mass spectrometry (LC-MS/MS). Metabolites were quantified and matched against entries in the human metabolome database (HMDB) and small molecule pathway database (SMPDB) to identify metabolites and metabolic pathways, respectively. Metabolic differences between HSK and control group were determined using multivariate statistical analysis.

RESULTS

A total of 329 metabolites were identified, of which 18 were significantly altered in HSK patients. Notably, 12 metabolites were significantly increased, and 6 were significantly decreased in HSK patients. The changed metabolites were enriched in these pathways: arginine and proline metabolism, phospholipid biosynthesis, alpha linolenic acid and linoleic acid metabolism, retinol metabolism. To assess the potential utility of tear biomarkers, a predictive model was developed combining 4 metabolites (AUC = 0.998 [95%CI: 0.975, 1]): D-proline, linoelaidic acid, plantagonine, and phosphorylcholine.

CONCLUSIONS

Our study establishes that HSK has a distinctive metabolomic profile, with 4 key elements maybe emerging as potential biomarkers for diagnostic purposes. These findings may provide novel insights into early and rapid diagnosis of HSK.

Enhanced infectivity of bovine viral diarrhoea virus (BVDV) in arginase-producing bovine monocyte-derived macrophages

Macrophages are important cells of the innate immunity that play a major role in Bovine Viral Diarrhoea Virus (BVDV) pathogenesis. Macrophages are not a homogenous population; they exist in different phenotypes, typically divided into two main categories: classically (pro-inflammatory) and alternatively activated (anti-inflammatory) or M1 and M2, respectively. The role of bovine macrophage phenotypes on BVDV infection is still unclear. This study characterized the interaction between BVDV and monocyte-derived macrophages (Mo-Mφ) collected from healthy cattle and polarized to an M1 or M2 state by using LPS, INF-γ, IL-4, or azithromycin. Arginase activity quantitation was utilized as a marker of the M2 Mo-Mφ spectrum. There was a significant association between arginase activity and the replication rate of BVDV strains of different genotypes and biotypes. Inhibition of arginase activity also reduced BVDV infectivity. Calves treated with azithromycin-induced Mo-Mφ of the M2 state produced high levels of arginase. Interestingly, azithromycin administered in vivo increased the susceptibility of macrophages to BVDV infection ex vivo. Mo-Mφ from pregnant dams and calves produced higher arginase levels than those from non-pregnant adult animals. The increased infection of arginase-producing alternatively activated bovine macrophages with BVDV supports the need to delve into a possible leading role of M2 macrophages in establishing the immune-suppressive state during BVDV convalescence.

Porcine circovirus type 2 infection inhibits macrophage M1 polarization induced by other pathogens via viral capsid protein and host gC1qR protein

Porcine circovirus type 2 (PCV2) has been proven to co-infect with a variety of pathogens and cause immunosuppression. Previously, we have reported that PCV2 infection attenuates the production of pro-inflammatory cytokines induced by other pathogens in porcine macrophages. However, whether PCV2 can affect M1-type macrophage polarization induced by other pathogens is less well reported. Herein, we found that PCV2 infection suppressed M1 macrophage production induced by porcine reproductive and respiratory syndrome virus (PRRSV) and Haemophilus parasuis (H. parasuis) in the lung and promoted the proliferation of these pathogens in the piglets. Consistently, we confirmed that PCV2 inhibits M1 macrophage production and its associated gene expression in porcine alveolar macrophages (PAMs) both ex vivo and in vitro. Meanwhile, PCV2 inhibited lipopolysaccharide (LPS)-induced pro-inflammatory cytokines in vitro in a time- and dose-dependent manner. In PCV2-infected cells, LPS-induced signal transducer and activator of transcription (STAT1) phosphorylation and its nuclear translocation were decreased. Based on these findings, we further identified a role for PCV2 capsid protein (Cap) in LPS-induced M1 macrophage-associated genes and found that PCV2 Cap can significantly reduce STAT1 phosphorylation and its nuclear translocation, as well as the production of M1 macrophage-related genes. As the binding protein of PCV2 Cap, gC1qR protein was also associated with this inhibition process. gC1qR-binding activity-deficient PCV2 Cap mutated protein (Cap RmA) appeared an attenuated inhibitory effect on other pathogen-induced polarization of M1-type macrophages, suggesting that the inhibitory effect of PCV2 infection on M1-type macrophage polarization induced by other pathogens is dependent on Cap protein and the host gC1qR protein. Altogether, our results demonstrate that PCV2 infection inhibits macrophage M1 polarization induced by other pathogens via capsid and host gC1qR protein modulating JAK/STAT signaling.

COVID-19: A Redox Disease-What a Stress Pandemic Can Teach Us About Resilience and What We May Learn from the Reactive Species Interactome About Its Treatment

Significance: Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the virus causing coronavirus disease 2019 (COVID-19), affects every aspect of human life by challenging bodily, socioeconomic, and political systems at unprecedented levels. As vaccines become available, their distribution, safety, and efficacy against emerging variants remain uncertain, and specific treatments are lacking. Recent Advances: Initially affecting the lungs, COVID-19 is a complex multisystems disease that disturbs the whole-body redox balance and can be long-lasting (Long-COVID). Numerous risk factors have been identified, but the reasons for variations in susceptibility to infection, disease severity, and outcome are poorly understood. The reactive species interactome (RSI) was recently introduced as a framework to conceptualize how cells and whole organisms sense, integrate, and accommodate stress. Critical Issues: We here consider COVID-19 as a redox disease, offering a holistic perspective of its effects on the human body, considering the vulnerability of complex interconnected systems with multiorgan/multilevel interdependencies. Host/viral glycan interactions underpin SARS-CoV-2's extraordinary efficiency in gaining cellular access, crossing the epithelial/endothelial barrier to spread along the vascular/lymphatic endothelium, and evading antiviral/antioxidant defences. An inflammation-driven "oxidative storm" alters the redox landscape, eliciting epithelial, endothelial, mitochondrial, metabolic, and immune dysfunction, and coagulopathy. Concomitantly reduced nitric oxide availability renders the sulfur-based redox circuitry vulnerable to oxidation, with eventual catastrophic failure in redox communication/regulation. Host nutrient limitations are crucial determinants of resilience at the individual and population level. Future Directions: While inflicting considerable damage to health and well-being, COVID-19 may provide the ultimate testing ground to improve the diagnosis and treatment of redox-related stress diseases. "Redox phenotyping" of patients to characterize whole-body RSI status as the disease progresses may inform new therapeutic approaches to regain redox balance, reduce mortality in COVID-19 and other redox diseases, and provide opportunities to tackle Long-COVID. Antioxid. Redox Signal. 35, 1226-1268.

Signature of genome wide gene expression in classical swine fever virus infected macrophages and PBMCs of indigenous vis-a-vis crossbred pigs

The genetic basis of differential host immune response vis-à-vis transcriptome profile was explored in PBMCs of indigenous (Ghurrah) and crossbred pigs after classical swine fever vaccination and in monocyte derived macrophages (MDMs) challenged with virulent classical swine fever (CSF) virus. The humoral immune response (E2 antibody) was higher (74.87%) in crossbred than indigenous pigs (58.20%) at 21st days post vaccination (21dpv). The rate of reduction of ratio of CD4⁺/CD8⁺ was higher in crossbred pigs than indigenous pigs at 7th days post vaccination (7dpv). The immune genes IFIT1, IFIT5, RELA, NFKB2, TNF and LAT2 were up regulated at 7dpv in RNA seq data set and was in concordance during qRT-PCR validation. The Laminin Subunit Beta 1 (LAMB1) was significantly (p ≤ 0.05) down-regulated in MDMs of indigenous pigs and consequently a significantly (p ≤ 0.01) higher copy number of virulent CSF virus was evidenced in macrophages of crossbred pigs than indigenous pigs. Activation of LXR:RXR pathway at 60 h post infection (60hpi) in MDMs of indigenous versus crossbred pigs inhibited nuclear translocation of NF-κB, resulted into transrepression of proinflammatory genes. But it helped in maintenance of HDL level by lowering down cholesterol/LDL level in MDMs of indigenous pigs. The key immune genes (TLR2, TLR4, IL10, IL8, CD86, CD54, CASP1) of TREM1 signaling pathway were upregulated at 7dpv in PBMCs but those genes were downregulated at 60hpi in MDMs indigenous pigs. Using qRT-PCR, the validation of differentially expressed, immunologically important genes (LAMB1, OAS1, TLR 4, TLR8 and CD86) in MDMs revealed that expression of these genes were in concordance with RNA-seq data.

Current and Future Therapeutic Strategies for Lentiviral Eradication from Macrophage Reservoirs

Macrophages, one of the most abundant populations of leukocytes in the body, function as the first line of defense against pathogen invaders. Human Immunodeficiency virus 1 (HIV-1) remains to date one of the most extensively studied viral infections. Naturally occurring lentiviruses in domestic and primate species serve as valuable models to investigate lentiviral pathogenesis and novel therapeutics. Better understanding of the role macrophages play in HIV pathogenesis will aid in the advancement towards a cure. Even with current efficacy of first- and second-line Antiretroviral Therapy (ART) guidelines and future efficacy of Long Acting Slow Effective Release-ART (LASER-ART); ART alone does not lead to a cure. The major challenge of HIV eradication is viral latency. Latency Reversal Agents (LRAs) show promise as a possible means to eradicate HIV-1 from the body. It has become evident that complete eradication will need to include combinations of various effective therapeutic strategies such as LASER-ART, LRAs, and gene editing. Review of the current literature indicates the most promising HIV eradication strategy appears to be LASER-ART in conjunction with viral and receptor gene modifications via the CRISPR/Cas9 system. Graphical abstract A multimodal approach to HIV treatment including gene editing, LASER-ART, and latency reversal agents may provide a means to achieve HIV eradication.

Infectious bronchitis corona virus establishes productive infection in avian macrophages interfering with selected antimicrobial functions

Infectious bronchitis virus (IBV) causes respiratory disease leading to loss of egg and meat production in chickens. Although it is known that macrophage numbers are elevated in the respiratory tract of IBV infected chickens, the role played by macrophages in IBV infection, particularly as a target cell for viral replication, is unknown. In this study, first, we investigated the ability of IBV to establish productive replication in macrophages in lungs and trachea in vivo and in macrophage cell cultures in vitro using two pathogenic IBV strains. Using a double immunofluorescent technique, we observed that both IBV Massachusetts-type 41 (M41) and Connecticut A5968 (Conn A5968) strains replicate in avian macrophages at a low level in vivo. This in vivo observation was substantiated by demonstrating IBV antigens in macrophages following in vitro IBV infection. Further, IBV productive infection in macrophages was confirmed by demonstrating corona viral particles in macrophages and IBV ribonucleic acid (RNA) in culture supernatants. Evaluation of the functions of macrophages following infection of macrophages with IBV M41 and Conn A5968 strains revealed that the production of antimicrobial molecule, nitric oxide (NO) is inhibited. It was also noted that replication of IBV M41 and Conn A5968 strains in macrophages does not interfere with the induction of type 1 IFN activity by macrophages. In conclusion, both M41 and Con A5968 IBV strains infect macrophages in vivo and in vitro resulting productive replications. During the replication of IBV in macrophages, their ability to produce NO can be affected without affecting the ability to induce type 1 IFN activity. Further studies are warranted to uncover the significance of macrophage infection of IBV in the pathogenesis of IBV infection in chickens.

Metabolic Profiles in Cell Lines Infected with Classical Swine Fever Virus

Viruses require energy and biosynthetic precursors from host cells for replication. An understanding of the metabolic interplay between classical swine fever virus (CSFV) and host cells is important for exploring the complex pathological mechanisms of classical swine fever (CSF). In the current study, and for the first time, we utilized an approach involving gas chromatography coupled with mass spectrometry (GC-MS) to examine the metabolic profiles within PK-15 and 3D4/2 cells infected with CSFV. The differential metabolites of PK-15 cells caused by CSFV infection mainly included the decreased levels of glucose 6-phosphate [fold change (FC) = −1.94)] and glyceraldehyde-3-phosphate (FC = −1.83) during glycolysis, ribulose 5-phosphate (FC = −1.51) in the pentose phosphate pathway, guanosine (FC = −1.24) and inosine (FC = −1.16) during purine biosynthesis, but the increased levels of 2-ketoisovaleric acid (FC = 0.63) during the citrate cycle, and ornithine (FC = 0.56) and proline (FC = 0.62) during arginine and proline metabolism. However, metabolite changes caused by CSFV infection in 3D4/2 cells included the reduced glyceraldehyde-3-phosphate (FC = −0.77) and pyruvic acid (FC = −1.42) during glycolysis, 2-ketoglutaric acid (FC = −1.52) in the citrate cycle, and the elevated cytosine (FC = 2.15) during pyrimidine metabolism. Our data showed that CSFV might rebuild cellular metabolic programs, thus aiding viral replication. These findings may be important in developing targets for new biomarkers for the diagnosis and identification of enzyme inhibitors or metabolites as antiviral drugs, or screening viral gene products as vaccines.

Different RNA splicing mechanisms contribute to diverse infective outcome of classical swine fever viruses of differing virulence: insights from the deep sequencing data in swine umbilical vein endothelial cells

Molecular mechanisms underlying RNA splicing regulation in response to viral infection are poorly understood. Classical swine fever (CSF), one of the most economically important and highly contagious swine diseases worldwide, is caused by classical swine fever virus (CSFV). Here, we used high-throughput sequencing to obtain the digital gene expression (DGE) profile in swine umbilical vein endothelial cells (SUVEC) to identify different response genes for CSFV by using both Shimen and C strains. The numbers of clean tags obtained from the libraries of the control and both CSFV-infected libraries were 3,473,370, 3,498,355, and 3,327,493 respectively. In the comparison among the control, CSFV-C, and CSFV-Shimen groups, 644, 158, and 677 differentially expressed genes (DEGs) were confirmed in the three groups. Pathway enrichment analysis showed that many of these DEGs were enriched in spliceosome, ribosome, proteasome, ubiquitin-mediated proteolysis, cell cycle, focal adhesion, Wnt signalling pathway, etc., where the processes differ between CSFV strains of differing virulence. To further elucidate important mechanisms related to the differential infection by the CSFV Shimen and C strains, we identified four possible profiles to assess the significantly expressed genes only by CSFV Shimen or CSFV C strain. GO analysis showed that infection with CSFV Shimen and C strains disturbed ‘RNA splicing’ of SUVEC, resulting in differential ‘gene expression’ in SUVEC. Mammalian target of rapamycin (mTOR) was identified as a significant response regulator contributed to impact on SUVEC function for CSFV Shimen. This computational study suggests that CSFV of differing virulence could induce alterations in RNA splicing regulation in the host cell to change cell metabolism, resulting in acute haemorrhage and pathological damage or infectious tolerance.

Immune Responses Against Classical Swine Fever Virus: Between Ignorance and Lunacy

Classical swine fever virus infection of pigs causes disease courses from life-threatening to asymptomatic, depending on the virulence of the virus strain and the immunocompetence of the host. The virus targets immune cells, which are central in orchestrating innate and adaptive immune responses such as macrophages and conventional and plasmacytoid dendritic cells. Here, we review current knowledge and concepts aiming to explain the immunopathogenesis of the disease at both the host and the cellular level. We propose that the interferon type I system and in particular the interaction of the virus with plasmacytoid dendritic cells and macrophages is crucial to understand elements governing the induction of protective rather than pathogenic immune responses. The review also concludes that despite the knowledge available many aspects of classical swine fever immunopathogenesis are still puzzling.

Macrophage Polarization in Virus-Host Interactions

Macrophage involvement in viral infections and antiviral states is common. However, this involvement has not been well-studied in the paradigm of macrophage polarization, which typically has been categorized by the dichotomy of classical (M1) and alternative (M2) statuses. Recent studies have revealed the complexity of macrophage polarization in response to various cellular mediators and exogenous stimuli by adopting a multipolar view to revisit the differential process of macrophages, especially those re-polarized during viral infections. Here, through examination of viral infections targeting macrophages/monocytic cells, we focus on the direct involvement of macrophage polarization during viral infections. Type I and type III interferons (IFNs) are critical in regulation of viral pathogenesis and host antiviral infection; thus, we propose to incorporate IFN-mediated antiviral states into the framework of macrophage polarization. This view is supported by the multifunctional properties of type I IFNs, which potentially elicit and regulate both M1- and M2-polarization in addition to inducing the antiviral state, and by the discoveries of viral mechanisms to adapt and modulate macrophage polarization. Indeed, several recent studies have demonstrated effective prevention of viral diseases through manipulation of macrophage immune statuses.

Classical swine fever virus and p7 protein induce secretion of IL-1β in macrophages

Classical swine fever virus (CSFV) has a tropism for vascular endothelial cells and immune system cells. The process and release of pro-inflammatory cytokines, including IL-1β and IL-18, is one of the fundamental reactions of the innate immune response to viral infection. In this study, we investigated the production of IL-1β from macrophages following CSFV infection. Our results showed that IL-1β was upregulated after CSFV infection through activating caspase-1. Subsequent studies demonstrated that reactive oxygen species may not be involved in CSFV-mediated IL-1β release. Recently, research has indicated a novel mechanism by which inflammasomes are triggered through detection of activity of viroporin. We further demonstrated that CSFV viroporin p7 protein induced IL-1β secretion which could be inhibited by the ion channel blocker amantadine and also discovered that p7 protein was a short-lived protein degraded by the proteasome. Together, our observations provided an insight into the mechanism of CSFV-induced inflammatory responses.

Classical swine fever virus down-regulates endothelial connexin 43 gap junctions

Classical swine fever is a contagious disease of pigs characterized by fatal hemorrhagic fever. Classical swine fever virus (CSFV) induces the expression of pro-inflammatory and pro-coagulant factors of vascular endothelial cells and establishes a long-term infection. This study aimed to understand the effect of CSFV on endothelial connexin 43 (Cx43) expression and gap junctional intercellular coupling (GJIC). Porcine aortic endothelial cells were infected with CSFV at different multiplicity of infection for 48 h. Semi-quantitative RT-PCR, immunoconfocal microscopy, and Western blotting showed that the transcription and translation of Cx43 were reduced, and this was associated with an attenuation of GJIC. This decrease occurred in a time-dependent manner. An ERK inhibitor (PD98059), a JNK inhibitor (SP600125), and proteasome/lysosome inhibitors all significantly reversed the reduction in Cx43 protein levels without any influence on the titer of progeny virus. In addition, CSFV activated ERK and JNK in a time-dependent manner and down-regulated Cx43 promoter activity, mainly through decreased AP2 binding. This effect was primarily caused by the replication of CSFV rather than a consequence of cytokines being induced by CSFV infection of endothelial cells.

Patterns of gene expression in swine macrophages infected with classical swine fever virus detected by microarray

Infection of domestic swine with highly virulent, classical swine fever virus (CSFV) strain Brescia, causes lethal disease in all infected animals. However, the molecular mechanisms involved in modulating the host cellular processes and evasion of the immune response have not been clearly established. To gain insight into, the early host response to CSFV, we analyzed the pattern of gene expression in infected swine macrophages, using custom designed swine microarrays. Macrophages, the target cell for CSFV infection, were isolated from primary cultures of peripheral blood mononuclear cells, allowing us to utilize identical uninfected macrophages at the same time points as CSFV-infected macrophages, allowing only genes induced by CSFV to be identified. First, microarray probes were optimized by screening 244,000 probes for hybridization with RNA from infected and uninfected macrophages. Probes that hybridized and passed quality control standards were used to design a 44,000 probe microarray for this study. Changes in expression levels of 79 genes (48 up- and 31 down-regulated) during the first 48h post-infection were observed. As expected many of the genes with an altered pattern of expression are involved in the development of an innate immune response. Several of these genes had differential expression in an attenuated strain NS4B.VGIv, suggesting that some of these differences are responsible for virulence. The observed gene expression profile might help to explain the immunological and pathological changes associated with infection of pigs with CSFV Brescia.

Global transcriptional profiles in peripheral blood mononuclear cell during classical swine fever virus infection

Classical swine fever virus (CSFV) is an etiologic agent that causes a highly contagious disease in pigs. Laying a foundation to solve problems in its pathogenic mechanism, microarray analysis was performed to detect the gene transcriptional profiles in peripheral blood mononuclear cells (PBMC) following infection with a Chinese highly virulent CSFV strain Shimen. Three susceptible pigs were inoculated intramuscularly with a lethal dose (1.0x10(6) TCID(50)) of CSFV. Pigs showed classical CSF signs, depletion of lymphocytes and monocytes consistent with CSFV infection, and the CSFV genome was also confirmed in the PBMC. The PBMC were isolated at 1, 3, 6 and 9 days post-inoculation (dpi). Total RNA were extracted and subjected to microarray analysis. Data showed that expression of 847 genes wherein 467 genes were known function and the remaining 380 genes were unknown function, and 541 up- and 306 down-regulation, altered after infection. There were 54, 181, 438 and 354 up- and 61, 120, 218 and 145 down-regulated genes presented on 1, 3, 6 and 9dpi, respectively. These genes were involved in immune response (14.5%), apoptosis (3.3%), signal transduction (7.6%), transcription (4.4%), metabolism (11%), transport (3.9%), development (6.8%) and cell cycle (3.7%). Results demonstrated its usefulness in exploring the pathogenic mechanisms of CSFV.

Acute induction of cell death-related IFN stimulated genes (ISG) differentiates highly from moderately virulent CSFV strains

Classical swine fever (CSF) severity is dependent on the virulence of the CSF virus (CSFV) strain. The earliest event detected following CSFV infection is a decrease in lymphocytes number. With some CSFV strains this leads to lymphopenia, the severity varying according to strain virulence. This lymphocyte depletion is attributed to an induction of apoptosis in non-infected bystander cells. We collected peripheral blood mononuclear cells (PBMC) before and during 3 days post-infection with either a highly or moderately virulent CSFV strain and subjected them to comparative microarray analysis to decipher the transcriptomic modulations induced in these cells in relation to strain virulence. The results revealed that the main difference between strains resided in the kinetics of host response to the infection: strong and immediate with the highly virulent strain, progressive and delayed with the moderately virulent one. Also although cell death/apoptosis-related IFN stimulated genes (ISG) were strongly up-regulated by both strains, significant differences in their regulation were apparent from the observed differences in onset and extent of lymphopenia induced by the two strains. Furthermore, the death receptors apoptotic pathways (TRAIL-DR4, FASL-FAS and TNFa-TNFR1) were also differently regulated. Our results suggest that CSFV strains might exacerbate the interferon alpha response, leading to bystander killing of lymphocytes and lymphopenia, the severity of which might be due to the host’s loss of control of IFN production and downstream effectors regulation.

Activation and modulation of antiviral and apoptotic genes in pigs infected with classical swine fever viruses of high, moderate or low virulence

The immune response to CSFV and the strategies of this virus to evade and suppress the pigs’ immune system are still poorly understood. Therefore, we investigated the transcriptional response in the tonsils, median retropharyngeal lymph node (MRLN), and spleen of pigs infected with CSFV strains of similar origin with high, moderate, and low virulence. Using a porcine spleen/intestinal cDNA microarray, expression levels in RNA pools prepared from infected tissue at 3 dpi (three pigs per virus strain) were compared to levels in pools prepared from uninfected homologue tissues (nine pigs). A total of 44 genes were found to be differentially expressed. The genes were functionally clustered in six groups: innate and adaptive immune response, interferon-regulated genes, apoptosis, ubiquitin-mediated proteolysis, oxidative phosphorylation and cytoskeleton. Significant up-regulation of three IFN-γ-induced genes in the MRLNs of pigs infected with the low virulence strain was the only clear qualitative difference in gene expression observed between the strains with high, moderate and low virulence. Real-time PCR analysis of four response genes in all individual samples largely confirmed the microarray data at 3 dpi. Additional PCR analysis of infected tonsil, MRLN, and spleen samples collected at 7 and 10 dpi indicated that the strong induction of expression of the antiviral response genes chemokine CXCL10 and 2′–5′ oligoadenylate synthetase 2, and of the TNF-related apoptosis-inducing ligand (TRAIL) gene at 3 dpi, decreased to lower levels at 7 and 10 dpi. For the highly and moderately virulent strains, this decrease in antiviral and apoptotic gene expression coincided with higher levels of virus in these immune tissues.

Genomic expression profiling of peripheral blood leukocytes of pigs infected with highly virulent classical swine fever virus strain Shimen

Classical swine fever (CSF), caused by a virus of the same name (CSFV), is a highly contagious swine pyrexic disease featuring extensive haemorrhagic lesions and leukopenia, but little is known about the molecular mechanisms of its pathogenesis. To gain insight into the interaction between the virus and host cells, microarray analyses were performed to detect alterations in genomic expression of pig peripheral blood leukocytes (PBLs) following CSFV infection. Three healthy pigs were inoculated with a lethal dose of highly virulent CSFV strain Shimen. PBLs were isolated at the onset of typical clinical signs and total RNA was subjected to microarray analyses with Affymetrix Porcine Genome Array GeneChips. Of all 20 201 pig genes arrayed in the chip, 1745 showed altered expression (up- or downregulation) after infection. These were classified into eight functional groups, relating to cell proliferation (3.6 %), immune response (2.1 %), apoptosis (1.4 %), kinase activity (1.4 %), signal transduction (1.4 %), transcription (0.7 %), receptor activity (0.7 %) and cytokines/chemokines (0.4 %). The remaining 88.3 % of genes had unknown functions. Alterations in genomic expression were confirmed by real-time RT-PCR of selected cellular genes and Western blotting of annexin 2, a cellular protein relating to virus infection. The observed expression changes of numerous genes involved in immune and inflammatory responses and in the apoptosis process indicate that CSFV has developed sophisticated mechanisms to cause leukopenia in infected pigs. These data provide a basis for exploring the molecular pathogenesis of CSFV infection through an understanding of the interaction between viral and cellular components.