Seroprevalence of encephalomyocarditis virus in intensive pig farms in China

TRIM7 inhibits encephalomyocarditis virus replication by activating interferon-β signaling pathway

Tripartite motif-containing protein 7 (TRIM7), the member of tripartite motif (TRIM) family, plays an important role in innate immune responses against viral infection. Among them, the function of TRIM7 in Encephalomyocarditis virus (EMCV) infection has not been reported. Here, we found that TRIM7 inhibited the replication of EMCV through the type I interferon (IFN) signaling pathway. Interestingly, TRIM7 was down-regulated after EMCV infection in HEK293T cells. Further, overexpression of TRIM7 suppressed the replication of EMCV in HEK293T cells and enhanced the activity of IFN-β promoter. On the other hand, knockdown of the endogenous TRIM7 promoted EMCV infection and impaired the activity of IFN-β promoter. TRIM7 could regulate retinoic acid-inducible gene I (RIG-I)/ melanoma differentiation-associated gene 5 (MDA5)/ mitochondrial antiviral-signaling protein (MAVS) mediated IFN-β signaling pathway. Moreover, TRIM7 interacted with MAVS and they were co-located in HEK293T cells. We demonstrate that TRIM7 plays a positive role in IFN-β signaling pathway during EMCV infection and suppresses EMCV replication. Taken together, the presented results suggest that TRIM7 has a pivotal function in anti-EMCV infection, thereby providing a potential target for further development of anti-EMCV inhibitors.

A recent view about encephalomyocarditis virus circulating in compartmentalised animal population in Northern Italy

Encephalomyocarditis virus (Picornaviridae, Cardiovirus A) is the causative agent of the homonymous disease, which may induce myocarditis, encephalitis and reproductive disorders in various mammals, especially in swine. Despite the disease occurred endemically in pig farms since 1997, the recent increase of death experimented in Northern Italy prompted to furtherly investigate the evolution of the virus and the actual spread of the infection. Italian EMC viruses, collected between 2013 and 2019, showed an overall antigenic stability. The in-house ELISA Monoclonal Antibodies based, able to reveal changes in seven different antigenic sites, showed only sporadic and occasional mutations in considered samples and the subsequent phylogenetic analysis confirmed antigenic panel's remarks. All the isolates could be classified within a unique lineage, which comprise other European strains and confirm that the viruses currently circulating in Italy developed from a unique common ancestor. Despite the demonstrated stability of virus, some putative newly emerged variants were detected through antigenic profile analysis and phylogenesis. Finally, the serosurvey proved that spread of EMCV is greater than the diffusion of fatal infections would suggest, due to subclinical circulation of EMCV. It demonstrated an increase in the proportion of seropositive farms, if compared with previous data with no remarkable differences between farms with and without clinical evidence of disease.

Host protein, HSP90β, antagonizes IFN-β signaling pathway and facilitates the proliferation of encephalomyocarditis virus in vitro

Encephalomyocarditis virus (EMCV) is a small, non-enveloped, single stranded RNA virus which infects a wide variety of mammalian species, and has zoonotic importance. Many host proteins are known to regulate EMCV proliferation by interacting with its structural or nonstructural proteins, but the regulatory role and mechanism of heat shock protein 90β (HSP90β), in EMCV infection has not been reported yet. Here, we report that overexpression of HSP90β significantly promotes the growth and proliferation of EMCV in vitro. On the contrary, down-regulation of HSP90β by RNAi or geldanamycin inhibits EMCV replication. HSP90β suppresses IFN-β responses in the RLRs pathway by targeting the expression of the key adaptor molecules MAVS, TBK1, and IRF3, but not MDA5. This study demonstrates the firsthand information that HSP90β plays a positive role in viral proliferation by inhibiting EMCV induced IFN-β production. Collectively, the results reveal new insights into HSP90β-assisted progression of EMCV infection.

Construction, expression, and characterization of a single-chain variable fragment (ScFv) antibody targeting to the encephalomyocarditis virus

Encephalomyocarditis virus (EMCV) is as a potential zoonotic agent with a wide host range. Here, applying gene splicing by overlap extension PCR (SOE-PCR), we describe a simple method for producing single-chain variable fragment (scFv) antibody against EMCV that configurates in the orientation of VH-(GGGGS)₄ -VL. DNA template was resverse transcribed by total RNA that derived from hyperimmunized antibody positive mice spleen after inoculation inactivated EMCV-PV21 as antigen. Using the degenerate primers designed for the variable regions of IgG of murine antibody, the 417 bp of gene encoding VH-linker (VHL) and 360 bp of gene encoding linker-VL (LVL) of the anti-EMCV was individually amplified from DNA template by PCR, repectively. The 762 bp gene encoding anti-EMCV scFv was constructed by SOE-PCR when the mixed VHL and LVL genes were used as the template. The amplified gene subcloned into pGEX-6P1 to yield pGEX-6P1/EMCV-scFv. Recombinant vector transformed into the Escherichia coli BL21 (DE3) and a 53 KDa GST-scFv fusion protein was obtained by SDS-PAGE electrophoresis. Animal experiment results showed that the pretective rate of mice in group A which challenged 500 μL 10⁴ TCID₅₀ EMCV per mouse for 7 d post-inoculation scFv 3 d (0.5 mg purified recombinant scFv per mouse) was 91.67% (11/12). The serum anti-EMCV antibody titer in group A mice was most significantly higher than that in positive control mouse (P < 0.01), coversely the serum relative mRNA copies were significantly lower than that in positive control mouse (P < 0.05). These findings indicated that recombinant anti-EMCV scFv has remarkable anti-EMCV effect in mice.

Development and application of an indirect ELISA for the detection of antibodies against encephalomyocarditis virus

Encephalomyocarditis virus (EMCV) can cause acute myocarditis in young pigs or reproductive failure in sows. It has been recognized worldwide as a pathogen infecting many species and causes substantial economic losses. In the present study, an indirect ELISA was developed for the detection of antibodies to EMCV. The VP1 gene of EMCV was amplified by reverse transcription-quantitative polymerase chain reaction and expressed in Escherichia coli with 49.3 kDa under the condition of isopropyl-β-d-thiogalactoside. Following this, the authors obtained the recombinant protein VP1 as a coating antigen. The antigen concentration and serum dilution were optimized using a checkerboard titration. Compared with viral neutralization tests, the sensitivity and specificity of the indirect ELISA was 95.7% and 92.9%, respectively. A total of 265 clinical swine serum samples from different pig farms in China were used to a serological survey. The seropositive rate of the serum samples was 81.9%. In conclusion, the developed indirect ELISA assay is sensitive and specific, which will be useful for large-scale serological survey in EMCV infection and monitoring antibodies titers against EMCV.

Isolation and Characterization of Encephalomyocarditis Virus from Dogs in China

Encephalomyocarditis virus (EMCV) is as a potential zoonotic agent with a wide host range. Here, we describe an EMC virus isolate, identified as EMCV C15, which was successfully obtained from the serum of dogs from animal hospitals. Virus production in cell culture was confirmed by EMCV-specific real-time RT-PCR, indirect immunofluorescence assays and electron microscopy. In addition, the open reading frame sequence (ORF) of the EMCV C15 virus was determined. From sequence comparison and phylogenetic analysis among 24 reference EMCV strains, it appears that the EMCV C15 strain is closely genetically related to strain BEL2887A/91 (>99.0% nucleotide identity). In artificially challenged dogs, the heart and brain were important targets of EMCV C15. This study provides genetic and pathogenic characterization of the EMCV C15 strain isolated in Beijing and calls for sustained surveillance of EMCV infection in China to support better prevention and control of the disease.

Isolation and molecular and phylogenetic analyses of encephalomyocarditis virus from wild boar in central China

Encephalomyocarditis virus (EMCV) can infect many host species and cause acute myocarditis and respiratory failure in piglets, reproductive failure in pregnant sows. In this study, an EMCV strain, designated JZ1202, was isolated from semi-captive wild boars that presented with acute myocarditis and sudden death in central China. It was identified by hemagglutination inhibition (HI) assay, reverse transcription polymerase chain reaction (RT-PCR) and genome sequencing. The subsequent results showed that the virus could produce a specific cytopathic effect on BHK cells and could cause clinical symptoms and pathological changes in mice. Complete genome sequencing and multiple sequence alignment indicated that JZ1202 strain was 81.3%-99.9% identical with other isolates worldwide. Phylogenetic analysis of the whole genome, ORF, VP3/VP1 and 3D genes using neighbor-joining method revealed that JZ1202 isolate was grouped into lineage 1. The results of this study confirmed that an EMCV strain JZ 1202 isolated from wild boar in central China was fatal to mice and provided new epidemiologic data on EMCV in China.

National serosurvey of encephalomyocarditis virus in healthy people and pigs in China

Encephalomyocarditis virus (EMCV) is a zoonotic pathogen that has a wide spectrum of host range. The virus has been discovered on swine farms worldwide and can cause acute fatal myocarditis in piglets and reproductive disorders in sows. Although EMCV infection has been documented in farmed pigs in China, seroprevalence in humans has not been reported. In this study, we conducted nationwide serological surveys for EMCV in humans and farmed pigs in China in 2013, by the use of a double antigen sandwich ELISA method. A total of 3305 serum samples from healthy people were obtained from seven geographical regions in China, of which 1010 samples (30.56%) were positive for EMCV antibodies. The overall seroprevalence for EMCV in the age groups of 0-20, 21-40, 41-60 and >60 years were 13.5%, 30.25%, 36.83% and 38.71% respectively, showing a tendency of increasing with age (P = 0.000). A total of 3470 serum samples from farmed pigs were collected and tested for antibodies to EMCV. A high seroprevalence of 77% was recorded, and significant regional differences were observed. It was concluded that people and pigs in China were commonly infected by EMCV. In addition, in order to characterize changes of seroprevalence during natural EMCV infection in pigs, 240 serial serum samples were collected from 30 pigs (at 0, 15, 30, 60, 75, 90, 120, and 150 days of age) in a farrow-to-finish farm in China. The data showed that there were two EMCV antibody peaks: the first peak appeared at day 30, followed by a decrease in EMCV antibody titer, and the second occurred after day 75. Thus, the most susceptible period of pigs for EMCV infection was between day 30 and day 75 of age.

Recombinant Encephalomyocarditis Viruses Elicit Neutralizing Antibodies against PRRSV and CSFV in Mice

Encephalomyocarditis virus (EMCV) is capable of infecting a wide range of species and the infection can cause myocarditis and reproductive failure in pigs as well as febrile illness in human beings. In this study, we introduced the entire ORF5 of the porcine reproductive and respiratory syndrome virus (PRRSV) or the neutralization epitope regions in the E2 gene of the classical swine fever virus (CSFV), into the genome of a stably attenuated EMCV strain, T1100I. The resultant viable recombinant viruses, CvBJC3m/I-ΔGP5 and CvBJC3m/I-E2, respectively expressed partial PRRSV envelope protein GP5 or CSFV neutralization epitope A1A2 along with EMCV proteins. These heterologous proteins fused to the N-terminal of the nonstructural leader protein could be recognized by anti-GP5 or anti-E2 antibody. We also tested the immunogenicity of these fusion proteins by immunizing BALB/c mice with the recombinant viruses. The immunized animals elicited neutralizing antibodies against PRRSV and CSFV. Our results suggest that EMCV can be engineered as an expression vector and serve as a tool in the development of novel live vaccines in various animal species.

Development of a TaqMan-based real-time reverse transcription polymerase chain reaction assay for the detection of encephalomyocarditis virus

Encephalomyocarditis virus (EMCV) is one of the major zoonosis pathogens and can cause acute myocarditis in young pigs or reproductive failure in sows. In this study, a TaqMan-based real-time reverse transcription polymerase chain reaction (RT-PCR) assay targeting 3D gene of EMCV was developed and their sensitivities and specificities were investigated. The results indicated that the standard curve had a wide dynamic range (10(1)-10(6) copies/μL) with a linear correlation (R(2)) of 0.996 between the cycle threshold (Ct) value and template concentration. The real-time RT-PCR assay is highly sensitive and able to detect 1.4×10(2) copies/μL of EMCV RNA, as no cross-reaction was observed with other viruses. These data suggested that the real-time RT-PCR assay developed in this study will be suitable for future surveillance and specific diagnosis of EMCV-infection.

Rapid detection of encephalomyocarditis virus by one-step reverse transcription loop-mediated isothermal amplification method

The encephalomyocarditis virus (EMCV) can cause acute myocarditis in young pigs or reproductive failure in sows. In this study, a reverse transcription loop-mediated isothermal amplification (RT-LAMP) assay was developed to detect EMCV RNA. The RT-LAMP assay was highly sensitive and able to detect 2.2 × 10(-5)ng of EMCV RNA, as no cross-reaction was observed with other viruses. The RT-LAMP assay was conducted in isothermal (62 °C) conditions within 50 min. The amplified products of EMCV could be detected as ladder-like bands using agarose gel electrophoresis. This is the first report to demonstrate the application of a one-step RT-LAMP assay for the detection of EMCV. The sensitive, specific and rapid RT-LAMP assay developed in this study can be applied widely in clinical diagnosis and field surveillance of EMCV.

Complete genome sequence of porcine encephalomyocarditis virus from an aardvark in china

A strain of encephalomyocarditis virus, HNXX13, was isolated from an aardvark in central China. The complete genome was sequenced and analyzed, and phylogenetic analysis suggests that HNXX13 belongs to encephalomyocarditis virus group 1.

Complete Genome Sequence of Porcine Encephalomyocarditis Virus Strain BD2

Encephalomyocarditis virus (EMCV) causes acute myocarditis in young pigs or reproductive failure in sows, and it is divided into two main groups. Here, we report the complete genome sequence of EMCV strain BD2, which belongs to group I.

Detection and characterization of potentially zoonotic viruses in faeces of pigs at slaughter in Germany

Pigs can harbour a variety of viruses in their gastrointestinal tract. Some of them are closely related to human viruses and are therefore suspected to have a zoonotic potential. Only little is known about the presence of those viruses in pigs at slaughter. However, by contamination of meat with zoonotic viruses during the slaughtering process, food-borne transmission to humans may be possible. Here we analyzed 120 faecal samples of pigs at slaughter from 3 different geographical regions of Germany for the presence of astrovirus (AstV), encephalomyocarditis virus (EMCV), hepatitis E virus (HEV), norovirus genogroup II (NoV GII) and group A rotavirus (GARV). Using real-time RT-PCR, the most frequently detected virus was AstV, which was present in 20.8% of the samples, followed by NoV GII with a detection rate of 14.2%. EMCV, HEV and GARV were found only occasionally with detection rates of 4.2%, 2.5% and 0.8%, respectively. Analyses of partial genome sequences of the viruses indicated that the detected AstV and NoV GII mainly represented typical pig virus strains, which have not been detected in humans so far. However, the GARV and HEV strains were more closely related to human strains. The results indicate that enteric viruses, some of them with zoonotic potential, are present in pig faeces at slaughter. Application of good hygiene practice is necessary to minimize the risk of introducing these viruses into the food and to prevent virus transmission to highly exposed persons such as slaughterers and veterinarians.

The encephalomyocarditis virus

The encephalomyocarditis virus (EMCV) is a small non-enveloped single-strand RNA virus, the causative agent of not only myocarditis and encephalitis, but also neurological diseases, reproductive disorders and diabetes in many mammalian species. EMCV pathogenesis appears to be viral strain- and host-specific, and a better understanding of EMCV virulence factors is increasingly required. Indeed, EMCV is often used as a model for diabetes and viral myocarditis, and is also widely used in immunology as a double-stranded RNA stimulus in the study of Toll-like as well as cytosolic receptors. However, EMCV virulence and properties have often been neglected. Moreover, EMCV is able to infect humans albeit with a low morbidity. Progress on xenografts, such as pig heart transplantation in humans, has raised safety concerns that need to be explored. In this review we will highlight the biology of EMCV and all known and potential virulence factors.