Classical swine fever in pigs: recent developments and future perspectives

PKM2 induces mitophagy through the AMPK-mTOR pathway promoting CSFV proliferation

Viruses exploit the host cell's energy metabolism system to support their replication. Mitochondria, known as the powerhouse of the cell, play a critical role in regulating cell survival and virus replication. Our prior research indicated that the classical swine fever virus (CSFV) alters mitochondrial dynamics and triggers glycolytic metabolic reprogramming. However, the role and mechanism of PKM2, a key regulatory enzyme of glycolytic metabolism, in CSFV replication remain unclear. In this study, we discovered that CSFV enhances PKM2 expression and utilizes PKM2 to inhibit pyruvate production. Using an affinity purification coupled mass spectrometry system, we successfully identified PKM as a novel interaction partner of the CSFV non-structural protein NS4A. Furthermore, we validated the interaction between PKM2 and both CSFV NS4A and NS5A through co-immunoprecipitation and confocal analysis. PKM2 was found to promote the expression of both NS4A and NS5A. Moreover, we observed that PKM2 induces mitophagy by activating the AMPK-mTOR signaling pathway, thereby facilitating CSFV proliferation. In summary, our data reveal a novel mechanism whereby PKM2, a metabolic enzyme, promotes CSFV proliferation by inducing mitophagy. These findings offer a new avenue for developing antiviral strategies.

IMPORTANCE

Viruses rely on the host cell's material-energy metabolic system for replication, inducing host metabolic disorders and subsequent immunosuppression-a major contributor to persistent viral infections. Classical swine fever virus (CSFV) is no exception. Classical swine fever is a severe acute infectious disease caused by CSFV, resulting in significant economic losses to the global pig industry. While the role of the metabolic enzyme PKM2 (pyruvate dehydrogenase) in the glycolytic pathway of tumor cells has been extensively studied, its involvement in viral infection remains relatively unknown. Our data unveil a new mechanism by which the metabolic enzyme PKM2 mediates CSFV infection, offering novel avenues for the development of antiviral strategies.

E-2 Glycoprotein Structural Variations Analysed within the CSFV 2.2. Genogroup in a “Closed Grid” Sampling Study from Meghalaya, India

CSF is enzootic in most of pig-producing states, particularly in the NorthEastern (NE) region of India. In this study, a total of 249 sera and 190 tissue samples were collected from different parts of Meghalaya. Samples were processed by ELISA and RT-PCR for serological and molecular diagnosis. Representative positive samples from the Khasi Hills region were selected for sequencing and “close grid” phylogenetic relationship using partial genomic regions of 5′UTR and E2. High seroprevalence (74.7%) of CSFV was recorded. Detection of the CSFV genome in serologically positive serum samples and tissue samples was 61.29% and 18.94%, respectively. BLAST and phylogenetic analyses indicate the clustering of all the field samples in subgroup 2.2, with high identity with EF014334 from China. Molecular structural modelling of the E2 partial sequence using representative sequences MG563797 from Meghalaya and EF014334 from China indicate potential changes in the protein motif and its conformation, which may explain the emergence of subgroup 2.2 CSFV replacing the predominant subgroup 1.1 viruses in NorthEast India. The epidemiological information presented in this study may be helpful for determination of disease incidence in this region, whereas the virus profile may be useful for framing disease control programs.

A Novel Blocking Enzyme-Linked Immunosorbent Assay Based on a Biotinylated Nanobody for the Rapid and Sensitive Clinical Detection of Classical Swine Fever Virus Antibodies

Monoclonal and polyclonal antibodies are mostly used for the development of traditional enzyme-linked immunosorbent assays (ELISAs), but the use of certain conventional antibodies may be limited by their low yield, the difficulty of their isolation, and their high cost. Heavy-chain antibodies derived from camelids with naturally missing light chains can overcome these deficiencies and are an excellent alternative to conventional antibodies. In this study, a nanobody (Nb)-AviTag fusion protein was constructed, and the feasibility of its use as a high-sensitivity probe in a blocking ELISA (bELISA) for classical swine fever virus (CSFV) was investigated. The CSFV E2 recombinant protein expressed by the CHO expression system exhibited good reactogenicity and immunogenicity and induced the production of high CSFV antibody levels in rabbits. Three different clones of Nbs were successfully isolated using a phage display system in alpaca, and an Nb1-AviTag fusion protein was successfully expressed using an Escherichia coli expression system. The purified Nb1-AviTag fusion protein was then biotinylated in vitro to obtain Nb1-biotin. A novel bELISA was developed for the detection of CSFV antibodies in clinical serum using Nb1-biotin as a probe. The cutoff value of bELISA was 32.18%, the sensitivity of bELISA was higher than that of the bELISA kit with IDEXX antibody, and the coincidence rate was 94.7%. A rapid, low-cost, highly sensitive and highly specific CSFV E2 antibody-based bELISA method was successfully established and can be used for the serological evaluation of CSFV E2 subunit vaccines and the ELISA-based diagnosis of CSFV infection. IMPORTANCE Currently, the epidemic situation of classical swine fever (CSF) is sporadic, and cases of atypical swine fever are on the rise in China. Therefore, it is necessary to accurately eliminate suspected cases by using highly sensitive and specific diagnostic techniques. In our study, a rapid, low-cost, highly sensitivity, highly reliable and reproducible, and highly specific classical swine fever virus (CSFV) E2 antibody-based blocking ELISA method was successfully established by using the phage display system and the Nb1-AviTag fusion expression platform. It provides a new technique for serological evaluation of CSFV vaccines and ELISA-based diagnosis of CSFV infection.

Search for additional tests for immunobiological evaluation of the candidate vaccines against African swine fever

The spread of African swine fever (ASF) in Eurasia has forced a return to the development of live vaccines based on naturally or experimentally attenuated strains of the virus including those resulting from genetic manipulations. This process includes evaluation of the immunomodulating properties of the vaccines. In this report we provide our assessment of two tests for immunobiological evaluation of a candidate live vaccine against ASF from the attenuated ASF virus (ASFV) strain KK-202: (i) investigation of the effect of the attenuated ASFV strain KK-202 on the protectiveness of the vaccine ASFV strain FK-32/135 and a vaccine against classical swine fever (CSF) from the strain LK-VNIIVViM; (ii) determination of the phagocytic activity of blood neutrophils in pigs inoculated with ASFV strains differing in virulence. A simultaneous or sequential inoculation of attenuated strain KK-202 (seroimmunotype II) and vaccine strain FK-32/135 (seroimmunotype IV) into pigs resulted in the loss of protection against the virulent strain France-32 (seroimmunotype IV). Following the simultaneous or sequential inoculations of the ASFV strain KK-202 and the CSF virus (CSFV) vaccine produced from the strain LK-VNIIVViM, the neutralizing antibody titers against the CSFV observed in the experimental groups (after vaccination and after the challenge infection with the virulent CSFV strain Shimen) were not different from those found in animals of the control group. The phagocytic activity of blood neutrophils was shown to increase from 30% in the norm to 50%-94% depending on the virulence of the ASFV strains inoculated into pigs. The results of this work demonstrate the ability of the attenuated ASFV strains to modulate the development of the cellular link of protective immunity without negative impact on the humoral immune response. The informative value of the described immunobiological tests in vivo and in vitro seems to be a more preferable alternative in comparison to the commonly used in vitro tests, which do not always correlate with the development of protection against ASF.

Transboundary Animal Diseases, an Overview of 17 Diseases with Potential for Global Spread and Serious Consequences

Animals provide food and other critical resources to most of the global population. As such, diseases of animals can cause dire consequences, especially disease with high rates of morbidity or mortality. Transboundary animal diseases (TADs) are highly contagious or transmissible, epidemic diseases, with the potential to spread rapidly across the globe and the potential to cause substantial socioeconomic and public health consequences. Transboundary animal diseases can threaten the global food supply, reduce the availability of non-food animal products, or cause the loss of human productivity or life. Further, TADs result in socioeconomic consequences from costs of control or preventative measures, and from trade restrictions. A greater understanding of the transmission, spread, and pathogenesis of these diseases is required. Further work is also needed to improve the efficacy and cost of both diagnostics and vaccines. This review aims to give a broad overview of 17 TADs, providing researchers and veterinarians with a current, succinct resource of salient details regarding these significant diseases. For each disease, we provide a synopsis of the disease and its status, species and geographic areas affected, a summary of in vitro or in vivo research models, and when available, information regarding prevention or treatment.

Decoding the RNA viromes in rodent lungs provides new insight into the origin and evolutionary patterns of rodent-borne pathogens in Mainland Southeast Asia

BACKGROUND

As the largest group of mammalian species, which are also widely distributed all over the world, rodents are the natural reservoirs for many diverse zoonotic viruses. A comprehensive understanding of the core virome of diverse rodents should therefore assist in efforts to reduce the risk of future emergence or re-emergence of rodent-borne zoonotic pathogens.

RESULTS

This study aimed to describe the viral range that could be detected in the lungs of rodents from Mainland Southeast Asia. Lung samples were collected from 3284 rodents and insectivores of the orders Rodentia, Scandentia, and Eulipotyphla in eighteen provinces of Thailand, Lao PDR, and Cambodia throughout 2006-2018. Meta-transcriptomic analysis was used to outline the unique spectral characteristics of the mammalian viruses within these lungs and the ecological and genetic imprints of the novel viruses. Many mammalian- or arthropod-related viruses from distinct evolutionary lineages were reported for the first time in these species, and viruses related to known pathogens were characterized for their genomic and evolutionary characteristics, host species, and locations.

CONCLUSIONS

These results expand our understanding of the core viromes of rodents and insectivores from Mainland Southeast Asia and suggest that a high diversity of viruses remains to be found in rodent species of this area. These findings, combined with our previous virome data from China, increase our knowledge of the viral community in wildlife and arthropod vectors in emerging disease hotspots of East and Southeast Asia. Video abstract.

Classical swine fever virus: the past, present and future

Classical swine fever (CSF) is among the most relevant viral epizootic diseases of swine. Due to its severe economic impact, CSF is notifiable to the world organisation for animal health. Strict control policies, including systematic stamping out of infected herds with and without vaccination, have permitted regional virus eradication. Nevertheless, CSF virus (CSFV) persists in certain areas of the world and has re-emerged regularly. This review summarizes the basic established knowledge in the field and provides a comprehensive and updated overview of the recent advances in fundamental CSFV research, diagnostics and vaccine development. It covers the latest discoveries on the genetic diversity of pestiviruses, with implications for taxonomy, the progress in understanding disease pathogenesis, immunity against acute and persistent infections, and the recent findings in virus-host interactions and virulence determinants. We also review the progress and pitfalls in the improvement of diagnostic tools and the challenges in the development of modern and efficacious marker vaccines compatible with serological tests for disease surveillance. Finally, we highlight the gaps that require research efforts in the future.

Recent Advances in the Diagnosis of Classical Swine Fever and Future Perspectives

Classical swine fever (CSF) is a highly contagious viral disease of pigs, including wild boar. It is regarded as one of the major problems in the pig industry as it is still endemic in many regions of the world and has the potential to cause devastating epidemics, particularly in countries free of the disease. Rapid and reliable diagnosis is of utmost importance in the control of CSF. Since clinical presentations of CSF are highly variable and may be confused with other viral diseases in pigs, laboratory diagnosis is indispensable for an unambiguous diagnosis. On an international level, well-established diagnostic tests of CSF such as virus isolation, fluorescent antibody test (FAT), antigen capture antibody enzyme-linked immunosorbent assay (ELISA), reverse-transcription polymerase chain reaction (RT-PCR), virus neutralization test (VNT), and antibody ELISA have been described in detail in the OIE Terrestrial Manual. However, improved CSF diagnostic methods or alternatives based on modern technologies have been developed in recent years. This review thus presents recent advances in the diagnosis of CSF and future perspectives.

Pathology of the outbreak of subgenotype 2.5 classical swine fever virus in northern Vietnam

Classical swine fever (CSF) is an endemic disease in southeastern Asia and is one of the most important swine diseases in Vietnam. This study was conducted to characterize the pathology of natural cases of CSF in northern Vietnam in 2018 and their genetic prevalence. A total of 10 representative pigs were collected from four provinces (Hung Yen, Ha Noi, Quang Ninh and Thai Binh) during five outbreaks and examined pathologically. The gross and histopathological findings showed the disease was expressed as the acute or the subacute to chronic form of CSF, depending on the age of the animals. The most consistently observed lesions associated with infection by the classical swine fever virus (CSFV) included lymphoid depletions in tonsils, lymph node and spleen; histiocytic hyperplasia in spleen; cerebral haemorrhage; perivascular cuffing in the brain; renal erythrodiapedesis; urothelial vacuolation and degeneration and interstitial pneumonia. The immunohistochemical findings showed a ubiquitous CSFV antigen mainly in the monocytes/macrophages and in the epithelial and endothelial cells in various organs. CSFV neurotropism was also found in the small neurons of the cerebrum and the ganglia of the myenteric plexus. Analysis of the full-length envelope protein (E2) genome sequence showed that all strains were genetically clustered into subgenotype 2.5, sharing a nucleotide identity of 94.0%-100.00%. Based on the results of this study, the strain was categorized as a moderately virulent CSFV.

Classical Swine Fever Virus Biology, Clinicopathology, Diagnosis, Vaccines and a Meta-Analysis of Prevalence: A Review from the Indian Perspective

Classical swine fever (CSF) is an economically significant, multi-systemic, highly contagious viral disease of swine world over. The disease is notifiable to the World Organization for Animal Health (OIE) due to its enormous consequences on porcine health and the pig industry. In India, the pig population is 9.06 million and contributes around 1.7% of the total livestock population. The pig industry is not well organized and is mostly concentrated in the eastern and northeastern states of the country (~40% of the country’s population). Since the first suspected CSF outbreak in India during 1944, a large number of outbreaks have been reported across the country, and CSF has acquired an endemic status. As of date, there is a scarcity of comprehensive information on CSF from India. Therefore, in this review, we undertook a systematic review to compile and evaluate the prevalence and genetic diversity of the CSF virus situation in the porcine population from India, targeting particular virus genes sequence analysis, published reports on prevalence, pathology, and updates on indigenous diagnostics and vaccines. The CSF virus (CSFV) is genetically diverse, and at least three phylogenetic groups are circulating throughout the world. In India, though genotype 1.1 predominates, recently published reports point toward increasing evidence of co-circulation of sub-genotype 2.2 followed by 2.1. Sequence identities and phylogenetic analysis of Indian CSFV reveal high genetic divergence among circulating strains. In the meta-analysis random-effects model, the estimated overall CSF prevalence was 35.4%, encompassing data from both antigen and antibody tests, and region-wise sub-group analysis indicated variable incidence from 25% in the southern to nearly 40% in the central zone, eastern, and northeastern regions. A country-wide immunization approach, along with other control measures, has been implemented to reduce the disease incidence and eliminate the virus in time to come.

Apoptosis, Autophagy, and Pyroptosis: Immune Escape Strategies for Persistent Infection and Pathogenesis of Classical Swine Fever Virus

Classical swine fever (CSF) is a severe acute infectious disease that results from classical swine fever virus (CSFV) infection, which leads to serious economic losses in the porcine industry worldwide. In recent years, numerous studies related to the immune escape mechanism of the persistent infection and pathogenesis of CSFV have been performed. Remarkably, several independent groups have reported that apoptosis, autophagy, and pyroptosis play a significant role in the occurrence and development of CSF, as well as in the immunological process. Apoptosis, autophagy, and pyroptosis are the fundamental biological processes that maintain normal homeostatic and metabolic function in eukaryotic organisms. In general, these three cellular biological processes are always understood as an immune defense response initiated by the organism after perceiving a pathogen infection. Nevertheless, several viruses, including CSFV and other common pathogens such as hepatitis C and influenza A, have evolved strategies for infection and replication using these three cellular biological process mechanisms. In this review, we summarize the known roles of apoptosis, autophagy, and pyroptosis in CSFV infection and how viruses manipulate these three cellular biological processes to evade the immune response.

Coordinated expression of vascular endothelial growth factor A and urokinase-type plasminogen activator contributes to classical swine fever virus Shimen infection in macrophages

BACKGROUND

The Shimen strain of classical swine fever (CSF) virus (CSFV) causes CSF, which is mainly characterised by disseminated intravascular haemorrhage. Macrophages are an essential component of innate immunity against pathogenic microorganisms; however, the role of macrophages in CSF pathogenesis remains unclear. To illuminate the infective mechanism of CSFV, we used gene co-expression networks derived from macrophages infected with CSFV Shimen and CSFV C as well as uninfected macrophages to screen key regulatory genes, and their contributions to the pathogenesis of CSF were discussed.

RESULTS

Vascular endothelial growth factor A (VEGFA) and plasminogen activator, urokinase (PLAU, which encodes urokinase-type plasminogen activator [uPA]) were identified as coordinated genes expressed in macrophages by gene co-expression networks. Quantitative polymerase chain reaction and western blot analysis confirmed that VEGFA and PLAU were significantly up-regulated at both the transcription and translation levels after infection. Further, confocal microscopy analysis proposed that the VEGFA and uPA proteins were temporally co-localised with the CSFV protein E2.

CONCLUSIONS

Our findings suggest that co-expression of VEGFA and PLAU in macrophages contributes to CSFV Shimen infection and serves as a significant avenue for the strain to form an inflammatory microenvironment, providing new insight into the mechanisms of CSF caused by a virulent strain.

Expression and serological application of recombinant epitope-repeat protein carrying an immunodominant epitope of Newcastle disease virus nucleoprotein

Purpose

The aim of the present study was to develop a serodiagnostic test for differentiation infected from vaccinated animal (DIVA) strategy accompanying the marker vaccine lacking an immunodominant epitope (IDE) of nucleoprotein of Newcastle disease virus (NDV).

Materials and Methods

Recombinant epitope-repeat protein (rERP) gene encoding eight repeats of the IDE sequence (ETQFLDLMRAVANSMR) by tetra-glycine linker was synthesized. Recombinant baculovirus carrying the rERP gene was generated to express the rERP in insect cells. Specificity and sensitivity of an indirect enzyme-linked immunosorbent assay (ELISA) employing the rERP was evaluated.

Results

The rERP with molecular weight of 20 kDa was successfully expressed by the recombinant baculovirus in an insect-baculovirus system. The rERP was antigenically functional as demonstrated by Western blotting. An indirect ELISA employing the rERP was developed and its specificity and sensitivity was determined. The ELISA test allowed discrimination of NDV infected sera from epitope deletion virus vaccinated sera.

Conclusion

The preliminary results represent rERP ELISA as a promising DIVA diagnostic tool.

Discovery of Diverse Rodent and Bat Pestiviruses With Distinct Genomic and Phylogenetic Characteristics in Several Chinese Provinces

Bats and rodents are widely distributed worldwide and can be native or intermediate reservoirs of many important zoonotic viruses. Pestiviruses are a group of virus species of the genus Pestivirus under the family Flaviviridae that can infect a wide variety of artiodactylous hosts, including swine and ruminants. Two classic types of pestiviruses, bovine viral diarrhea virus and classical swine fever virus, are important causative agents of mild-to-severe disease in bovine and swine hosts, respectively, and cause tremendous economic losses in these industries. Recent reports revealed that bats and rodents could also act as natural hosts of pestiviruses and an atypical porcine pestivirus, which cause disease in piglets, showed a close genetic relationship with a specific bat pestivirus, RaPestV-1. This study aimed to describe the detection and characterization of novel pestiviruses from bats and rodents in different locations by analyzing the available bat and rodent virome data from throughout China. Two bat pestivirus species and four rodent pestivirus species that are distinct from other known viruses were identified and sequenced. These viruses were identified from two bat species and four rodent species in different Chinese provinces. There were two distinct lineages present in these viruses, that differ from artiodactylous pestivirus. These findings expand our understanding of the genetic diversity of pestiviruses in bats and rodents and suggest the presence of a diverse set of pestiviruses in non-artiodactylous hosts. This study may provide new insight for the prevention of future viral disease outbreaks originating from bats and rodents.

Seroprevalence of Classical Swine Fever in pigs of Karnataka and comparative diagnostic evaluation of antigen ELISA and reverse transcriptase -PCR

Classical swine fever is highly contagious viral disease of swine causing huge economic losses to pig farmersand pig industry. The study was conducted in Karnataka to understand the current scenario of CSF in the state andto evaluate efficiency of diagnostic tests (antigen ELISA and RT-PCR) in detecting the disease. Serum sampleswere collected from 270 pigs from 13 districts of the state and were tested for the presence of CSF antibodies.Whole blood samples (151) from 14 outbreaks of CSF were collected for the comparative diagnosis of the diseaseusing Antigen ELISA and reverse transcriptase (RT)-PCR. A seroprevalence of 28.5% (77/270) was found in theserum samples collected form the whole Karnataka. The southern Karnataka had higher seroprevalence (47%) incomparison to northern Karnataka region where seroprevalence was 17%. It confirms endemicity of the disease insouthern region. Of 151 blood samples collected for comparative diagnosis, 61 samples were positive for CSF byRT-PCR and 39 by antigen ELISA, indicating the superiority of RT-PCR over antigen ELISA to detect CSFVinfection in earliest stages of infection.

Seroprevalence of selected viral pathogens in pigs reared in organized farms of Meghalaya from 2014 to 16

Aim:

A pilot study was carried out to find out the seroprevalence of Porcine circovirus 2 (PCV2), classical swine fever virus (CSFV), and Porcine respiratory and reproductive syndrome virus (PRRS) in pig population of Meghalaya.

Materials and Methods:

Serum samples were collected from piglets of 40–45 days age group, growers, and sows reared under organized and unorganized management in 11 districts of Meghalaya situated in the Khasi, Jaintia, and Garo hills divisions in the time period of 2014-2016 from apparently healthy and suspected pigs. Seroprevalence of PCV2, CSFV, and PRRS specific antibodies was detected by enzyme-linked immunosorbent assay (ELISA).

Results:

A total of 1899 serum samples were collected and screened using antibody ELISA kits specific for PCV2, CSFV, and PRRS. The highest antibody prevalence during the selected time periods was detected for PCV2 (80.8% in 2014, 79.1% in 2015, and 96.2% in 2016) followed by CSFV (76.4% in 2014, 66.09% in 2015, and 25.5% in 2016) and PRRS (2.8% in 2014, 2.7% in 2015, and 3.62% in 2016). The result indicates high seroprevalence for PCV2, which can be considered as an inducement factor due to the immunosuppressive nature of the virus, for animals being susceptible to other pathogens in farms where airborne transmission of PCV2 and postweaning multisystemic wasting syndrome among animals reared in close pens can be a major possibility.

Conclusions:

The data from this study indicates ubiquitous prevalence of PCV2 antibodies in the farm animals along with the endemic presence of swine fever and emergence of PRRS in an organized farm. There are few reports regarding PCV2 infections/outbreaks in pigs associated with reproductive failure from northern and southern part of India, but till date, there are no reports regarding concomitant infection of CSFV and PCV2 from India. Considerable high seropositivity of PCV2 indicates the need for high impact hygiene practice in farms, routine seromonitoring and implementation the vaccination program. To the author’s best knowledge, this is the first documented report on the seroprevalence of PCV2, CSFV, and PRRS from pig population of Meghalaya.

African and classical swine fever: similarities, differences and epidemiological consequences

For the global pig industry, classical (CSF) and African swine fever (ASF) outbreaks are a constantly feared threat. Except for Sardinia, ASF was eradicated in Europe in the late 1990s, which led to a research focus on CSF because this disease continued to be present. However, ASF remerged in eastern Europe in 2007 and the interest in the disease, its control and epidemiology increased tremendously. The similar names and the same susceptible species suggest a similarity of the two viral diseases, a related biological behaviour and, correspondingly, similar epidemiological features. However, there are several essential differences between both diseases, which need to be considered for the design of control or preventive measures. In the present review, we aimed to collate differences and similarities of the two diseases that impact epidemiology and thus the necessary control actions. Our objective was to discuss critically, if and to which extent the current knowledge can be transferred from one disease to the other and where new findings should lead to a critical review of measures relating to the prevention, control and surveillance of ASF and CSF. Another intention was to identify research gaps, which need to be closed to increase the chances of a successful eradication of ASF and therefore for a decrease of the economic threat for pig holdings and the international trade.

CSFV Infection Up-Regulates the Unfolded Protein Response to Promote Its Replication

Classical swine fever (CSF) is an OIE-listed, highly contagious animal disease caused by classical swine fever virus (CSFV). The endoplasmic reticulum (ER) is an organelle in which the replication of many RNA viruses takes place. During viral infection, a series of events elicited in cells can destroy the ER homeostasis that cause ER stress and induce an unfolded protein response (UPR). In this study, we demonstrate that ER stress was induced during CSFV infection as several UPR-responsive elements such as XBP1(s), GRP78 and CHOP were up-regulated. Specifically, CSFV transiently activated IRE1 pathway at the initial stage of infection but rapidly switched off, likely due to the reduction in cytoplasm Ca²⁺ after viral incubation. Additionally, our data show that the ER stress induced by CSFV can promote CSFV production, which the IRE1 pathway play an important role in it. Evidence of ER stress in vivo was also confirmed by the marked elevation of GRP78 in CSFV-infected pig PBMC and tissues. Collectively, these data indicate that the ER stress was induced upon CSFV infection and that the activation of the IRE1 pathway benefits CSFV replication.

Molecular approaches to the diagnosis and monitoring of production diseases in pigs

Production disease in pigs is caused by a variety of different pathogens, mainly enteric and respiratory and can result in significant economic loss. Other factors such as stress, poor husbandry and nutrition can also contribute to an animal's susceptibility to disease. Molecular biomarkers of production disease could be of immense value by improving diagnosis and risk analysis to determine best practice with an impact on increased economic output and animal welfare. In addition to the use of multiplex PCR or microarrays to detect individual or mixed pathogens during infection, these technologies can also be used to monitor the host response to infection via gene expression. The patterns of gene expression associated with cellular damage or initiation of the early immune response may indicate the type of pathology and, by extension the types of pathogen involved. Molecular methods can therefore be used to monitor both the presence of a pathogen and the host response to it during production disease. The field of biomarker discovery and implementation is expanding as technologies such as microarrays and next generation sequencing become more common. Whilst a large number of studies have been carried out in human medicine, further work is needed to identify molecular biomarkers in veterinary medicine and in particular those associated with production disease in the pig industry. The pig transcriptome is highly complex and still not fully understood. Further gene expression studies are needed to identify molecular biomarkers which may have predictive value in identifying the environmental, nutritional and other risk factors which are associated with production diseases in pigs.

Recombinant Swinepox Virus Expressing Glycoprotein E2 of Classical Swine Fever Virus Confers Complete Protection in Pigs upon Viral Challenge

Classical swine fever (CSF) is a highly contagious and serious viral disease that affects the pig industry worldwide. The glycoprotein E2 of the classical swine fever virus (CSFV) can induce neutralizing antibodies, and it is widely used for novel vaccine development. To explore the development of a vaccine against CSFV infections, the gene of glycoprotein E2 was inserted into the swinepox virus (SPV) genome by homologous recombination. The culture titers of rSPV-E2 remained at about 4.3 × 10⁶ TCID₅₀ for more than 60 passages in PK15 and swine testis cell lines. The rSPV-E2 could not be replicated in Vero, MDBK or other non-porcine cell lines. After two to three passages, the SPV specific gene of rSPV-E2 could not been detected in the non-porcine cell culture. To evaluate the immunogenicity of rSPV-E2, 20 CSFV seronegative minipigs were immunized with rSPV-E2, a commercial C-strain vaccine, wild-type SPV (wtSPV; negative control), or PBS (a no-challenge control). After challenge with CSFV, pigs in the rSPV-E2-immunized group showed significantly shorter fever duration compared with the wtSPV-treated group (P < 0.05). E2-specific antibodies in the rSPV-E2-immunized group increased dramatically after vaccination and increased continuously over time. CSFV genomic copies in the serum of rSPV-E2-immunized pigs were significantly less compared with the wtSPV-treated group at all time points after challenge (P < 0.01). Significant reduction in gross lung lesion scores, histopathological liver, spleen, lung, and kidney lesion scores were noted in the rSPV-E2-immunized group compared with the wtSPV-treated group (P < 0.01). The results suggested that the recombinant rSPV-E2 provided pigs with significant protection from CSFV infections; thus, rSPV-E2 offers proof of principle for the development of a vaccine for the prevention of CSFV infections in pigs.

A Simulation Model to Determine Sensitivity and Timeliness of Surveillance Strategies

Animal surveillance systems need regular evaluation. We developed an easily applicable simulation model of the German wild boar population to investigate two evaluation attributes: the sensitivity and timeliness (i.e. the ability to detect a disease outbreak rapidly) of a surveillance system. Classical swine fever (CSF) was used as an example for the model. CSF is an infectious disease that may lead to massive economic losses. It can affect wild boar as well as domestic pigs, and CSF outbreaks in domestic pigs have been linked to infections in wild boar. Awareness of the CSF status in wild boar is therefore vital. Our non-epidemic simulation model is based on real data and evaluates the currently implemented German surveillance system for CSF in wild boar. The results show that active surveillance for CSF fulfils the requirements of detecting an outbreak with 95% confidence within one year after the introduction of CSF into the wild boar population. Nevertheless, there is room for improved performance and efficiency by more homogeneous (active and passive) sampling of wild boar over the year. Passive surveillance alone is not sufficient to meet the requirements for detecting the infection. Although CSF was used as example to develop the model, it may also be applied to the evaluation of other surveillance systems for viral diseases in wild boar. It is also possible to compare sensitivity and timeliness across hypothetical alternative or risk-based surveillance strategies.

Discovery of a novel putative atypical porcine pestivirus in pigs in the USA

Pestiviruses are some of the most significant pathogens affecting ruminants and swine. Here, we assembled a 11 276 bp contig encoding a predicted 3635 aa polyprotein from porcine serum with 68 % pairwise identity to that of a recently partially characterized Rhinolophus affinis pestivirus (RaPV) and approximately 25-28 % pairwise identity to those of other pestiviruses. The virus was provisionally named atypical porcine pestivirus (APPV). Metagenomic sequencing of 182 serum samples identified four additional APPV-positive samples. Positive samples originated from five states and ELISAs using recombinant APPV Erns found cross-reactive antibodies in 94 % of a collection of porcine serum samples, suggesting widespread distribution of APPV in the US swine herd. The molecular and serological results suggest that APPV is a novel, highly divergent porcine pestivirus widely distributed in US pigs.

Biological and molecular characterization of classical swine fever challenge virus from India

Aim:

The aim of this study was biological and molecular characterization of classical swine fever (CSF) challenge virus from India.

Materials and Methods:

CSF challenge virus maintained at Division of Biological standardization was experimentally infected to two seronegative piglets. The biological characterization was done by clinical sign and symptoms along with postmortem findings. For molecular characterization 5’-nontranslated region, E2 and NS5B regions were amplified by reverse transcription polymerase chain reaction and sequenced. The sequences were compared with that of reference strains and the local field isolates to establish a phylogenetic relation.

Results:

The virus produced symptoms of acute disease in the piglets with typical post-mortem lesions. Phylogenetic analysis of the three regions showed that the current Indian CSF Challenge virus is having maximum similarity with the BresciaX strain (USA) and Madhya Pradesh isolate (India) and is belonging to subgroup 1.2 under Group 1.

Conclusion:

Based on biological and molecular characterization of CSF challenge virus from India is described as a highly virulent virus belonging to subgroup 1.2 under Group 1 along with some field isolates from India and Brescia strain.