Smartphone recognition-based immune microparticles for rapid on-site visual data-sharing detection of Newcastle disease virus.

Since the last century, animal viruses have posed great threats to the health of humans and the farming industry. Therefore, virus control is of great urgency, and regular, timely, and accurate detection is essential to it. Here, we designed a rapid on-site visual data-sharing detection method for the Newcastle disease virus with smartphone recognition-based immune microparticles. The detection method we developed includes three major modules: preparation of virus detection vectors, sample detection, and smartphone image analysis with data upload. First, the hydrogel microparticles containing active carboxyl were manufactured, which coated nucleocapsid protein of NDV. Then, HRP enzyme-labeled anti-NP nanobody was used to compete with the NDV antibody in the serum for color reaction. Then the rough detection results were visible to the human eyes according to the different shades of color of the hydrogel microparticles. Next, the smartphone application was used to analyze the image to determine the accurate detection results according to the gray value of the hydrogel microparticles. Meanwhile, the result was automatically uploaded to the homemade cloud system. The total detection time was less than 50 min, even without trained personnel, which is shorter than conventional detection methods. According to experimental results, this detection method has high sensitivity and accuracy. And especially, it uploads the detection information via a cloud platform to realize data sharing, which plays an early warning function. We anticipate that this rapid on-site visual data-sharing detection method can promote the development of virus self-checking at home.

A synthetic toll-like receptor 7 agonist inhibits porcine reproductive and respiratory syndrome virus replication in piglets.

Toll-like receptor 7 (TLR7) agonists have been shown to exert therapeutic effects against several viruses. However, antiviral potential of TLR7 agonist in inhibiting porcine reproductive and respiratory syndrome virus (PRRSV) infection has not been assessed in vivo. In our previous study, a synthetic TLR7 agonist, SZU101, was confirmed to inhibit PRRSV infection of porcine alveolar macrophages (PAMs). Here, antiviral effects of SZU101 were evaluated in PRRSV-challenged piglets based on assessments of rectal temperature, viremia, gross and microscopic lung lesions, PRRSV-specific antibodies, PRRSV-specific lymphocyte proliferation and serum IFN-ß level. Our results revealed that SZU101 treatment alleviated PRRSV-induced rectal temperature spikes, pulmonary pathologic changes, and serum viral load. Meanwhile, administration of SZU101 led to increased proliferation of PRRSV-specific lymphocytes and serum IFN-ß levels, but did not enhance PRRSV-specific antibody production. These results demonstrate that SZU101 has potential as a therapeutic treatment for PRRS.

Isolation and Genetic Characterization of Parvoviruses From Dogs, Cats, Minks, and Raccoon Dogs in the Eastern Region of Shandong Province, China.

The eastern region of Shandong province, China, is an intensive economic mink and raccoon dog breeding area. To investigate the molecular variations of parvovirus in cats, dogs, minks, and raccoon dogs from this region, feline panleukopenia virus (FPV), canine parvovirus 2 (CPV-2), mink enteritis virus (MEV), and raccoon dog parvovirus (RDPV) were separately isolated and characterized from the respective animals with gastroenteritis. PCR amplification showed that there were 15/18 (83.3%), 9/13 (69.2%), 8/11 (72.7%), and 3/7 (42.9%) samples from the diseased animals separately positive for FPV, CPV-2, MEV, and RDPV. Of these, a total of six FPV, six MEV, four CPV-2, and three RDPV strains were successfully isolated using F81 cells. Next, the near-complete genomes of 19 parvovirus isolates were amplified and analyzed. The viral particle 2 (VP2) sequence alignment showed that they shared 97.2-100% nucleotide similarity. Phylogenetic analysis showed that the five FPV isolates were in the same branch, and an FPV isolate was closely related with MEV and RDPV isolates obtained in this study. These suggested that cross-species infection occurred in the Shandong region between the FPV, MEV, and RDPV. For the four CPV-2 isolates, three were antigenic variant strains CPV-2a, and the other was antigenic variant strain CPV-2c. Additionally, the mutations that had emerged in the VP2 amino acids of CPV-2 also occurred in the VP2 from the FPV, MEV, and RDPV isolates. This study suggested that the continuous evolution of the parvovirus may be accelerated in areas with a high density of economic animal trading/breeding, and controlling parvovirus infection in these animals remains a challenge.

Major Vault Protein Inhibits Porcine Reproductive and Respiratory Syndrome Virus Infection in CRL2843CD163 Cell Lines and Primary Porcine Alveolar Macrophages.

Porcine reproductive and respiratory syndrome (PRRS), a significant viral infectious disease that commonly occurs among farmed pigs, leads to considerable economic losses to the swine industry worldwide. Major vault protein (MVP) is a host factor that induces type Ⅰ interferon (IFN) production. In this study, we evaluated the effect of MVP on PRRSV infection in CRL2843CD163 cell lines and porcine alveolar macrophages (PAMs). Our results showed that MVP expression was downregulated by PRRSV infection. Adenoviral overexpression of MVP inhibited PRRSV replication, whereas the siRNA knockdown of MVP promoted PRRSV replication. In addition, MVP knockdown has an adverse effect on the inhibitive role of MVP overexpression on PRRSV replication. Moreover, MVP could induce the expression of type Ⅰ IFNs and IFN-stimulated gene 15 (ISG15) in PRRSV-infected PAMs. Based on these results, MVP may be a potential molecular target of drugs for the effective prevention and treatment of PRRSV infection.

Biotinylated Single-Domain Antibody-Based Blocking ELISA for Detection of Antibodies Against Swine Influenza Virus.

BACKGROUND: Enzyme-linked immunosorbent assay (ELISA) is a common method for diagnosing swine influenza. However, the production of classical antibodies is both costly and time-consuming. As a promising alternative diagnostic tool, single-domain antibodies (sdAbs) offer the advantages of simpler and faster generation, good stability and solubility, and high affinity and specificity. METHODS: Phage display technology was used to isolate sdAbs against the SIV-NP protein from a camel VHH library. The sdAb5 was fused to the biotin acceptor peptide (BAP) and a His-Tag for its expression as monomeric and site-specific biotinylation in E.coli to develop an sdAb-based blocking ELISA (sdAb-ELISA). In the sdAb-ELISA, the anti-SIV antibodies from swine samples were used to block the binding between the biotinylated sdAb5 and SIV-NP protein coated on the ELISA plate. The specificity, sensitivity, and reproducibility of sdAb-ELISA were determined. In addition, consistency among sdAb-ELISA, commercial ELISA kit, and Western blot was evaluated. RESULTS: Six SIV-NP-specific sdAbs were isolated, among which sdAb5 was identified as a dominant sdAb with higher reactivity. The cut-off value of biotinylated sdAb5-based bELISA was determined to be 29.8%. Compared with the positive reference serum against five different types of swine viruses, the developed sdAb-ELISA showed 100% specificity. The detection limit of sdAb-ELISA was 1:160 in an anti-SIV positive reference serum, which is lower than that of the commercial ELISA kit (1:20). In 78 diluted anti-SIV positive serum (1:80), 21 and 42 samples were confirmed as positive by the commercial ELISA kit and sdAb-ELISA, respectively. The coefficients of variation of intra- and inter-assay were 1.79-4.57% and 5.54-9.98%, respectively. The sdAb-ELISA and commercial ELISA kit showed a consistency of 94.17% in clinical swine serum samples. Furthermore, the coincidence rate was 96.67% between the results detected by sdAb-ELISA and Western blot. CONCLUSION: A specific, sensitive, and reproducible sdAb-ELISA was successfully developed, which offers a new, promising method to detect anti-SIV antibodies in swine serum.

Experimental infection of rabbit with swine-derived hepatitis E virus genotype 4.

Hepatitis E virus (HEV) is a zoonotic virus that is capable of causing cross-species infection. Rabbits can be experimentally infected with human- and swine-derived HEV-4 in the species Orthohepevirus A, and avian-derived HEV-3 in the species Orthohepevirus B suggesting rabbits can serve as an animal model for zoonotic HEV infection study. However, these studies show that the infectivity of swine HEV isolates in rabbits is not consistent. In this study, the animal study was conducted by the experimental infection of rabbit with a swine-derived HEV-4 isolated in China (designated CHN-SD-sHEV) for 28 weeks post-inoculation (wpi) in compassion to that infected with a rabbit-derived HEV-3 (designated HEV-SX-rHEV). Two rabbits were euthanized every 2 wpi for pathological examinations. The results showed that rabbits infected with CHN-SD-sHEV had the viremia and virus fecal shedding from 1 wpi to 22 wpi and seroconverted from 10 to 28 wpi. Meanwhile, elevated ALT levels were detected at 2 wpi. Moreover, virus replication was confirmed by the detection of both positive- and negative-strand HEV RNAs in the livers and spleens. Diarrhea and hepatocellular lesions were also observed in some animals. In contrast, rabbits experimentally infected with CHN-SX-rHEV exhibited earlier seroconversion, viremia and virus fecal shedding and hepatocellular lesions. Taken together, our data demonstrate that in comparison to the previously reported cases, the swine-derived HEV-4 isolated in China could cross-species infect rabbit accompanied with prolonged virus fecal shedding and liver lesions.

A Nanobody Targeting Viral Nonstructural Protein 9 Inhibits Porcine Reproductive and Respiratory Syndrome Virus Replication.

Porcine reproductive and respiratory syndrome (PRRS) is of great concern to the swine industry due to pandemic outbreaks of the disease, current ineffective vaccinations, and a lack of efficient antiviral strategies. In our previous study, a PRRSV Nsp9-specific nanobody, Nb6, was successfully isolated, and the intracellularly expressed Nb6 could dramatically inhibit PRRSV replication in MARC-145 cells. However, despite its small size, the application of Nb6 protein in infected cells is greatly limited, as the protein itself cannot enter the cells physically. In this study, a trans-activating transduction (TAT) peptide was fused with Nb6 to promote protein entry into cells. TAT-Nb6 was expressed as an inclusion body in Escherichia coli, and indirect enzyme-linked immunosorbent assays and pulldown assays showed that E. coli-expressed TAT-Nb6 maintained the binding ability to E. coli-expressed or PRRSV-encoded Nsp9. We demonstrated that TAT delivered Nb6 into MARC-145 cells and porcine alveolar macrophages (PAMs) in a dose- and time-dependent manner, and TAT-Nb6 efficiently inhibited the replication of several PRRSV genotype 2 strains as well as a genotype 1 strain. Using a yeast two-hybrid assay, Nb6 recognition sites were identified in the C-terminal part of Nsp9 and spanned two discontinuous regions (Nsp9aa454-551 and Nsp9aa599-646). Taken together, these results suggest that TAT-Nb6 can be developed as an antiviral drug for the inhibition of PRRSV replication and controlling PRRS disease.IMPORTANCE The pandemic outbreak of PRRS, which is caused by PRRSV, has greatly affected the swine industry. We still lack an efficient vaccine, and it is an immense challenge to control its infection. An intracellularly expressed Nsp9-specific nanobody, Nb6, has been shown to be able to inhibit PRRSV replication in MARC-145 cells. However, its application is limited, because Nb6 cannot physically enter cells. Here, we demonstrated that the cell-penetrating peptide TAT could deliver Nb6 into cultured cells. In addition, TAT-Nb6 fusion protein could suppress the replication of various PRRSV strains in MARC-145 cells and PAMs. These findings may provide a new approach for drug development to control PRRS.

Porcine reproductive and respiratory syndrome virus inhibits MARC-145 proliferation via inducing apoptosis and G2/M arrest by activation of Chk/Cdc25C and p53/p21 pathway.

Porcine reproductive and respiratory syndrome virus(PRRSV) is an important immunosuppressive virus which can suppresses infected cells proliferation. In this work, we examined PRRSV ability to manipulate cell cycle progression of MARC-145 cells and explored the potential molecular mechanisms. The results showed that PRRSV infection imposed a growth-inhibitory effect on MARC-145 cells by inducing cell cycle arrest at G2/M phase. This arrest was due to the significant decrease of Cdc2-cyclinB1 complex activity in PRRSV-infected cells and the activity reduction was a result of Cdc2 Tyr15 phosphorylation and the accumulation of Cdc2 and cyclinB1 in the nucleus. Not only elevated Wee1 and Myt1 expression and inactivated Cdc25C, but also increase of p21 and 14-3-3σ in a p53-dependent manner caused the inhibitory Tyr15 phosphorylation of Cdc2. PRRSV infection also activated Chk1. Our data suggest PRRSV infection induces G2/M arrest via various molecular regulatory mechanisms. These results provide a new insights for PRRSV pathogenesis.

Platycodin D Suppresses Type 2 Porcine Reproductive and Respiratory Syndrome Virus In Primary and Established Cell Lines.

Porcine reproductive and respiratory syndrome virus (PRRSV) is a continuous threat to the pork industry as it continues to cause significant economic loss worldwide. Currently, vaccination strategies provide very limited protection against PRRSV transmission. Consequently, there is an urgent need to develop new antiviral strategies. Platycodin D (PD) is one of the major bioactive triterpenoid saponins derived from Platycodon grandiflorum, a traditional Chinese medicine used as an expectorant for pulmonary diseases and a remedy for respiratory disorders. Here, we demonstrate that PD exhibits potent activity against PRRSV infection in Marc-145 cells and primary porcine alveolar macrophages. PD exhibited broad-spectrum inhibitory activities in vitro against high pathogenic type 2 PRRSV GD-HD strain and GD-XH strain as well as classical CH-1a and VR2332 strains. PD at concentrations ranging 1⁻4 µM significantly inhibited PRRSV RNA synthesis, viral protein expression and progeny virus production in a dose-dependent manner. EC50 values of PD against four tested PRRSV strains infection in Marc-145 cells ranged from 0.74 to 1.76 µM. Mechanistically, PD inhibited PRRSV replication by directly interacting with virions therefore affecting multiple stages of the virus life cycle, including viral entry and progeny virus release. In addition, PD decreased PRRSV- and LPS-induced cytokine (IFN-α, IFN-ß, IL-1α, IL-6, IL-8 and TNF-α) production in PAMs. Altogether, our findings suggested that PD is a potent inhibitor of PPRSV infection in vitro. However, further in vivo studies are necessary to confirm PD as a potential novel and effective PPRSV inhibitor in swine.

Cross-species infection of mice by rabbit hepatitis E virus.

Rabbits are recognized as a zoonotic reservoir of hepatitis E virus (HEV) for transmission to humans and other zoonotic reservoirs such as swine. The purpose of this study was to assess the ability of rabbit HEV to cross the species barrier to infect mice and also the usefulness of this animal to study HEV transmission and pathogenesis. In this study, uninfected BALB/c mice were experimentally inoculated with rabbit HEV either via gavage or through contact-exposure with infected mice. Rabbit HEV propagation in mice was evaluated by studying fecal virus shedding, viremia, seroconversion and microscopic liver lesions. Rabbit HEV could be detected in all mice infected by gavage, but only in some contact-exposed mice, with some animals exhibiting fecal virus shedding, seroconversion or viremia (one mouse only). Compared with inoculated mice, anti-rabbit HEV antibody titers and viral copy numbers in fecal and serum samples were lower in contact-exposed mice. Infected mice mainly exhibited phlebitis, hepatocyte swelling and necrosis. Microscopic liver lesion scores for inoculated and contact-exposed infected mice were higher than scores for negative controls. This study therefore demonstrates that rabbit HEV could infect BALB/c mice both though inoculation via gavage and through contact-exposure.

Characterization of Three Novel Linear Neutralizing B-Cell Epitopes in the Capsid Protein of Swine Hepatitis E Virus.

Hepatitis E virus (HEV) causes liver disease in humans and is thought to be a zoonotic infection, with domestic animals, including swine and rabbits, being a reservoir. One of the proteins encoded by the virus is the capsid protein. This is likely the major immune-dominant protein and a target for vaccination. Four monoclonal antibodies (MAbs), three novel, 1E4, 2C7, and 2G9, and one previously characterized, 1B5, were evaluated for binding to the capsid protein from genotype 4 swine HEV. The results indicated that 625DFCP628, 458PSRPF462, and 407EPTV410 peptides on the capsid protein comprised minimal amino acid sequence motifs recognized by 1E4, 2C7, and 2G9, respectively. The data suggested that 2C7 and 2G9 epitopes were partially exposed on the surface of the capsid protein. Truncated genotype 4 swine HEV capsid protein (sp239, amino acids 368 to 606) can exist in multimeric forms. Preincubation of swine HEV with 2C7, 2G9, or 1B5 before addition to HepG2 cells partially blocked sp239 cell binding and inhibited swine HEV infection. The study indicated that 2C7, 2G9, and 1B5 partially blocked swine HEV infection of rabbits better than 1E4 or normal mouse IgG. The cross-reactivity of antibodies suggested that capsid epitopes recognized by 2C7 and 2G9 are common to HEV strains infecting most host species. Collectively, MAbs 2C7, 2G9, and 1B5 were shown to recognize three novel linear neutralizing B-cell epitopes of genotype 4 HEV capsid protein. These results enhance understanding of HEV capsid protein structure to guide vaccine and antiviral design.IMPORTANCE Genotype 3 and 4 HEVs are zoonotic viruses. Here, genotype 4 HEV was studied due to its prevalence in human populations and pig herds in China. To improve HEV disease diagnosis and prevention, a better understanding of the antigenic structure and neutralizing epitopes of HEV capsid protein are needed. In this study, the locations of three novel linear B-cell recognition epitopes within genotype 4 swine HEV capsid protein were characterized. Moreover, the neutralizing abilities of three MAbs specific for this protein, 2C7, 2G9, and 1B5, were studied in vitro and in vivo Collectively, these findings reveal structural details of genotype 4 HEV capsid protein and should facilitate development of applications for the design of vaccines and antiviral drugs for broader prevention, detection, and treatment of HEV infection of diverse human and animal hosts.

Curcumin is a promising inhibitor of genotype 2 porcine reproductive and respiratory syndrome virus infection.

BACKGROUND: Porcine reproductive and respiratory syndrome virus (PRRSV) could lead to pandemic diseases and huge financial losses to the swine industry worldwide. Curcumin, a natural compound, has been reported to serve as an entry inhibitor of hepatitis C virus, chikungunya virus and vesicular stomatitis virus. In this study, we investigated the potential effect of curcumin on early stages of PRRSV infection. RESULTS: Curcumin inhibited infection of Marc-145 cells and porcine alveolar macrophages (PAMs) by four different genotype 2 PRRSV strains, but had no effect on the levels of major PRRSV receptor proteins on Marc-145 cells and PAMs or on PRRSV binding to Marc-145 cells. However, curcumin did block two steps of the PRRSV infection process: virus internalization and virus-mediated cell fusion. CONCLUSIONS: Our results suggested that an inhibition of genotype 2 PRRSV infection by curcumin is virus strain-independent, and mainly inhibited by virus internalization and cell fusion mediated by virus. Collectively, these results demonstrate that curcumin holds promise as a new anti-PRRSV drug.

Effect of housing arrangement on fecal-oral transmission of avian hepatitis E virus in chicken flocks.

BACKGROUND: Avian hepatitis E virus (HEV) infection is common in chicken flocks in China, as currently no measures exist to prevent the spread of the disease. In this study, we analyzed the effect of caged versus cage-free housing arrangements on avian HEV transmission. First, 127 serum and 110 clinical fecal samples were collected from 4 chicken flocks including the two arrangements in Shaanxi Province, China and tested for HEV antibodies and/or virus. Concurrently, 36 specific-pathogen-free chickens were divided equally into four experimental living arrangement groups, designated cage-free (Inoculated), caged (Inoculated), cage-free (Negative) and caged (Negative) groups. In caged groups, three cages contained 3 chickens each. Three chickens each from cage-free (Inoculated) and caged (Inoculated) groups (one chicken of each cage) were inoculated by cutaneous ulnar vein with the same dose of avian HEV, respectively. The cage-free (Negative) and caged (Negative) groups served as negative control. Serum and fecal samples were collected at 1 to 7 weeks post-inoculation (wpi) and liver lesions were scored at 7 wpi. RESULTS: The results of serology showed that the avian HEV infection rate (54.10%) of the cage-free chickens was significantly higher than the one (12.12%) for caged chickens (P < 0.05). Also, the rate of detection of avian HEV RNA in the clinical fecal samples was significantly higher in the cage-free (22.80%, 13/57) than caged birds (5.66%, 3/53). Moreover, under experimental conditions, the infected number of uninoculated cage-free chickens (6) was significantly higher than the one for the uninoculated caged birds (2), as evidenced by seroconversion, fecal virus shedding, viremia and gross and microscopic liver lesions. CONCLUSIONS: These results suggest that reduction of contact with feces as seen in the caged arrangement of housing chickens can reduce avian HEV transmission. This study provides insights for prevention and control of avian HEV infection in chicken flocks.

Decreased egg production in laying hens associated with infection with genotype 3 avian hepatitis E virus strain from China.

To determine the relationship between decreased egg production and avian HEV infection, thirty healthy 23-week-old Hy-Line Variety Brown layer hens were randomly divided into 3 groups with 10 hens per group. Next, a genotype 3 avian HEV strain from China was used to inoculate laying hens via oronasal or intravenous routes using a 50% chicken infectious dose of 500. All hens were necropsied at 14 weeks postinoculation (wpi). Fecal virus shedding, viremia, seroconversion, serum alanine aminotransferase (ALT) increases and liver lesions showed that after intravenous (i.v.) and oronasal inoculation, the laying hens were successfully infected. Compared with the uninoculated group, the i.v. and oronasally inoculated groups exhibited egg production decreases at 1wpi and 2wpi, reaching peak production at 3wpi and 8wpi, respectively. In both groups, decreased production was evident for 12 weeks and overall decreases ranged from 10% to 30%. In addition, in the 7 field layer farms exhibiting decreased egg production, vaccination regimens had been completed against Newcastle disease, infectious bronchitis, avian influenza H9N2 and H5N1 and egg drop syndrome virus. However, circulating avian HEV was confirmed on these farms using tests to detect avian HEV IgG antibodies and RNA. Therefore, the experimental and field data indicate that avian HEV infection acting alone could account for observed decreases in egg production in laying hens.

Antiviral Strategies against PRRSV Infection.

PRRSV (porcine reproductive and respiratory syndrome virus) is a major economically significant pathogen that has adversely impacted the global swine industry for almost 30 years. Currently PRRSV is estimated to cause losses of almost US$600 million per year in the USA. Except for new mutants that continually emerge during PRRSV outbreaks, our understanding of the virology, origin, and evolution of PRRSV and the host's immune response are largely inadequate. Such limited knowledge impedes development of effective methods to eradicate this virus. In this review, we systematically describe recent advances in anti-PRRSV research, especially focusing on those techniques with the potential to transform current anti-PRRSV strategies. Furthermore, a combination of these new techniques may provide creative insights to guide future PRRSV control and prevention.

Evaluation of recombinant Chinese avian hepatitis E virus (CaHEV) ORF2 and ORF3 proteins for protection of chickens against CaHEV infection.

Avian hepatitis E virus (HEV) is the etiologic agent of big liver and spleen disease in chickens. In 2010, the Chinese avian HEV (CaHEV) strain was isolated from chickens and demonstrated to cause the decreased egg production in layer hens. No avian HEV commercial vaccine has yet been developed to prevent virus infection in China. In this study, recombinant CaHEV truncated ORF2 and complete ORF3 proteins were evaluated separately for immunoprotection of chickens against CaHEV infection. First, truncated ORF2 and complete ORF3 proteins were expressed in Escherichia coli. Next, 48 specific-pathogen-free chickens were randomly divided into three groups. One group was immunized with truncated ORF2 protein, the second group was immunized with recombinant ORF3 protein, while the third group (control) was mock-immunized with PBS. After booster immunization, chickens in all three groups were challenged intravenously with CaHEV infectious stock and assessed for viremia, fecal virus shedding, seroconversion, and gross hepatic lesions. In the ORF2 protein-immunized group, no chickens showed evidence of avian HEV infection. In the ORF3 protein-immunized group, nine chickens exhibited viremia and seven had fecal virus shedding. In the control group, all 16 chickens showed viremia and fecal virus shedding. However, the durations in chickens from the ORF3 protein group (2-4weeks) were shorter than the ones from the control group (4-8weeks). Moreover, no gross liver lesions emerged in the ORF2 protein group, while lesions observed in the ORF3 protein group were milder than in controls. Therefore, the ORF2 protein can confer complete immunoprotection against chicken CaHEV infection, while the ORF3 protein only confers partial immunoprotection.

Rabbit hepatitis E virus is an opportunistic pathogen in specific-pathogen-free rabbits with the capability of cross-species transmission.

Hepatitis E virus (HEV) has been detected in rabbits, a recently identified natural reservoir. In this study, anti-HEV antibodies and viral RNA were detected in rabbits sourced from a specific-pathogen-free (SPF) rabbit vendor in Shaanxi Province, China. BLAST results of partial HEV ORF2 genes cloned here indicated that two viral strains circulated in the rabbits. Sequence determination of the complete genome (7302bp) of one strain and a partial ORF1 gene (1537bp) of the other strain showed that they shared 90% identity with one another and 78%-94% identity with other known rabbit HEVs. In addition, inoculation with rabbit HEV from SPF rabbits studied here resulted in infection of SPF pigs; this cross-species transmission was evidenced by seroconversion, viremia and faecal virus shedding. These results suggest that to prevent spread of this zoonotic pathogen, rabbits should be tested routinely for HEV RNA in SPF vendor facilities.

Heme oxygenase-1 metabolite biliverdin, not iron, inhibits porcine reproductive and respiratory syndrome virus replication.

Porcinereproductiveandrespiratorysyndromevirus (PRRSV) causes significant economic losses to the pork industry worldwide. Previously, we demonstrated that heme oxygenase-1 (HO-1) interferes with PRRSV replication. To elucidate the mechanisms involved, here we assess whether the HO-1 downstream metabolites biliverdin (BV) and/or iron mediate the HO-1 antiviral effect. We demonstrate a BV concentration-dependent suppression of PRRSV replication and show that virions are not directly inactivated by BV. Additionally, BV or N-acetyl cysteine (NAC) significantly reduced reactive oxygen species (ROS) in PRRSV-infected MARC-145 cells; however, because NAC did not reduce viral load, the BV antiviral effect is independent of decreased ROS levels. Moreover, a secondary metabolite of BV, bilirubin (BR), specifically mediates this anti-PRRSV activity via a nitric oxide (NO)-dependent cGMP/PKG signaling pathway. While increased iron via addition of FeCl3 did not interfere with PRRSV replication, iron depletion by deferoxamine (DFO) after cobalt-protoporphyrin IX induction of HO-1 did not restore PRRSV replication. Collectively, our findings identify a HO-1-BV/BR-NO-cGMP/PKG cascade as a novel pathway underlying the host cell antiviral effect. These results provide a unique insight into the molecular mechanisms underlying the antiviral effects of the stress-responsive protein HO-1 during PRRSV infection.