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Abstract: Pork products are a possible source of introduction of PCV2 isolates into a pig population. However, limited work has been done on the transmission through meat of porcine circovirus type 2 (PCV2), a virus associated with several disease syndromes in pigs. The objectives of this study were to determine if pork products from PCV2-infected pigs contain PCV2 DNA/antigen and to determine if the PCV2 present in the tissues is infectious by performing in vitro and in vivo studies. Skeletal muscle, bone marrow, and lymphoid tissues from pigs experimentally inoculated with PCV2 were collected 14 days post-inoculation (DPI). The tissues were tested for presence of PCV2 DNA by quantitative real-time PCR, for PCV2 antigen by immunohistochemistry (IHC), and for presence of infectious PCV2 by virus isolation and inoculation of PCV2 naïve pigs. Lymphoid tissues contained the highest amount of PCV2 (positive by PCR, IHC, and virus isolation), bone marrow contained a lower amount of PCV2 (positive by PCR and IHC but negative by virus isolation), and skeletal muscle contained the lowest amount of PCV2 (positive by PCR but negative by IHC and virus isolation). Naïve pigs fed for three consecutive days with either skeletal muscle, bone marrow, or lymphoid tissues all became PCV2 viremic as determined by quantitative real-time PCR on serum starting at 7 DPI. The pigs also seroconverted to PCV2 as determined by PCV2 IgM and IgG ELISA. In addition, PCV2 antigen was detected by IHC stains in lymphoid tissues and intestines collected from the majority of these pigs. Results from this study indicate that uncooked PCV2 DNA positive lymphoid tissues, bone marrow, and skeletal muscle from PCV2 viremic pigs contain sufficient amount of infectious PCV2 to infect naïve pigs by the oral route. [Copyright &y& Elsevier]

Highlights • Vaccination of sows with an inactivated MRV3 vaccine induced only a low level humoral response. • Maternal immunity acquired from vaccinated sows reduces MRV3 replication. • The U.S. MRV3 infects but only causes very mild diarrhea in pigs. Abstract A novel U.S. strain of mammalian orthoreovirus type 3 (MRV3) isolated from diarrheic pigs in 2015 was reportedly highly pathogenic in pigs. In this study, we first developed an inactivated MRV3 vaccine and determined its protective efficacy against MRV3 infection in conventional neonatal piglets. A pathogenicity study was also conducted in gnotobiotic pigs to further assess the pathogenicity of MRV3. To evaluate if piglets could be protected against MRV3 infection after immunization of pregnant sows with an inactivated MRV3 vaccine, pregnant sows were vaccinated with 2 or 3 doses of the vaccine or with PBS buffer. Four-day-old piglets born to vaccinated and unvaccinated sows were subsequently challenged with MRV3. The results showed that piglets born from vaccinated sows had lower levels of fecal viral RNA shedding at 1, 3, and 4 days post-challenge, suggesting that the inactivated MRV3 vaccine can reduce MRV3 replication. Surprisingly, although the conventional piglets were infected, they did not develop severe enteric disease as reported previously. Therefore, in an effort to further definitively assess the pathogenicity of MRV3, we experimentally infected gnotobiotic pigs, a more sensitive model for pathogenicity study, with the wild-type MRV3 virus. The infected gnotobiotic piglets all survived and exhibited only very mild diarrhea in some pigs. Taken together, the results indicate that the novel strain of MRV3 recently isolated in the United States infected but caused only very mild diarrhea in pigs, and that maternal immunity acquired from sows vaccinated with an inactivated vaccine can reduce MRV3 replication in neonatal pigs. [ABSTRACT FROM AUTHOR]

More than two decades after its emergence, porcine circovirus type 2 (PCV2) remains an economically important swine pathogen. Commercial vaccines which were first introduced to the U.S in 2006, have been highly effective in reducing clinical signs and improving production. Recent studies have indicated a declining level of PCV2 prevalence and viremia in the field. However, reports on the emergence of new viral variants have also continued to increase. This article reviews topics of current interest in the field of PCV2 vaccines; including the comparative efficacy of the available commercial products, efficacy of current vaccines against new and emerging strains, findings on the differences between immunity in natural infection versus vaccination, limitations of current experimental models for PCV2 vaccine studies, and new developments in novel experimental vaccines. The discussion is framed in the context of attempts for the possible eradication of PCV2 in the future. [ABSTRACT FROM AUTHOR]

Abstract: The objective of this study was to investigate cytokine expression and in vitro replication of porcine circovirus type 2 (PCV2) and porcine reproductive and respiratory syndrome virus (PRRSV) in pulmonary alveolar macrophages (PAMs) emphasizing PCV2 open-reading frame (ORF) origin (PCV2a or PCV2b) and PRRSV strain. Chimeric PCV2 viruses composed of different combinations of ORF1 and ORF2 of PCV2a or PCV2b (chimera PCV2a–2b and chimera PCV2b–2a) were constructed and five different PRRSV isolates were utilized: Type 1 (SD 01-08) or type 2 (NC16845b, VR-2332, MN-184, JA-142). PAMs were infected singularly or with combinations of PCV2b, PCV2a, chimera PCV2a–2b, and chimera PCV2b–2a, and one of the five PRRSV isolates. Real-time PCR was used to test PAMs (PCV2 mRNA) and supernatants (PRRSV RNA, PCV2 DNA, PCV2 mRNA) harvested at 24, 48, 72 and 96h post inoculation (hpi). Levels of IFN-γ, TNF-α and IL-10 were determined by quantitative ELISAs. PCV2 replication in PAMs was limited to groups inoculated with PCV2 strains containing ORF1 of PCV2a (PCV2a, chimera PCV2a–2b). Furthermore, in supernatants, PCV2 mRNA was only detected in groups coinfected with PRRSV regardless of strain at 48hpi supporting an enhancing effect of PRRSV on PCV2 infection. Changes in cytokine levels were minimal and associated with PRRSV strain for TNF-α. In summary, in vitro differences in PCV2 replication in PAMs inoculated with different PCV2–PRRSV combinations were independent of PCV2 ORF2 origin with minimal effects of concurrent PRRSV infection perhaps indicating that PCV2-specific changes in ORF1 may be more important than those in ORF2. [Copyright &y& Elsevier]

Abstract: To determine differences in infection kinetics of two temporally and genetically different type 2 porcine reproductive and respiratory syndrome virus (PRRSV) isolates in vivo with and without concurrent porcine circovirus (PCV) type 2a or 2b infection, 62 pigs were randomly assigned to one of seven groups: negative controls (n =8); pigs coinfected with a 1992 PRRSV strain (VR-2385) and PCV2a (CoI-92-2a; n =9), pigs coinfected with VR-2385 and PCV2b (CoI-92-2b; n =9), pigs coinfected with a 2006 PRRSV strain (NC16845b) and PCV2a (CoI-06-2a; n =9), pigs coinfected with NC16845b and PCV2b (CoI-06-2b; n =9), pigs infected with VR-2385 (n =9), and pigs infected with NC16845b (n =9). Blood samples were collected before inoculation and at day post-inoculation (dpi) 3, 6, 9 and 12 and tested for the presence of PRRSV antibody and RNA, PCV2 antibody and DNA, complete blood counts, and interferon gamma (IFN-γ) levels. Regardless of concurrent PCV2 infection, VR-2385 initially replicated at higher levels and reached peak replication levels at dpi 6. Pigs infected with VR-2385 had significantly higher amounts of viral RNA in serum on both dpi 3 and dpi 6, compared to pigs infected with NC16845b. The peak of NC16845b virus replication occurred between dpi 9 and dpi 12 and was associated with a delayed anti-PRRSV antibody response in these pigs. PCV2 coinfection resulted in significantly more severe macroscopic and microscopic lung lesions and a stronger anti-PRRSV IgG response compared to pigs infected with PRRSV alone. This work further emphasizes in vivo replication differences among PRRSV strains and the importance of coinfecting pathogens. [Copyright &y& Elsevier]

Abstract: A genetically distinct strain of avian hepatitis E virus (avian HEV-VA strain) was isolated from a healthy chicken in Virginia, and thus it is important to characterize and compare its pathogenicity with the prototype strain (avian HEV-prototype) isolated from a diseased chicken. Here we first constructed an infectious clone of the avian HEV-VA strain. Capped RNA transcripts from the avian HEV-VA clone were replication-competent after transfection of LMH chicken liver cells. Chickens inoculated intrahepatically with RNA transcripts of avian HEV-VA clone developed active infection as evidenced by fecal virus shedding, viremia, and seroconversion. To characterize the pathogenicity, RNA transcripts of both avian HEV-VA and avian HEV-prototype clones were intrahepatically inoculated into the livers of chickens. Avian HEV RNA was detected in feces, serum and bile samples from 10/10 avian HEV-VA-inoculated and 9/9 avian HEV-prototype-inoculated chickens although seroconversion occurred only in some chickens during the experimental period. The histopathological lesion scores were lower for avian HEV-VA group than avian HEV-prototype group in the liver at 3 and 5 weeks post-inoculation (wpi) and in the spleen at 3wpi, although the differences were not statistically significant. The liver/body weight ratio, indicative of liver enlargement, of both avian HEV-VA and avian HEV-prototype groups were significantly higher than that of the control group at 5wpi. Overall, the avian HEV-VA strain still induces histological liver lesions even though it was isolated from a healthy chicken. The results also showed that intrahepatic inoculation of chickens with RNA transcripts of avian HEV infectious clone may serve as an alternative for live virus in animal pathogenicity studies. [ABSTRACT FROM AUTHOR]

Abstract: The objectives of this study were (1) to compare the efficacy of two different PCV2 vaccination protocols (colostrum-derived immunity versus piglet vaccination) in a conventional PCV2 growing pig challenge model and (2) to evaluate the efficacy of vaccinating piglets with the same vaccine used in the dams. Two different commercially available vaccines (VAC1; VAC2) were used in the same experiment. Seventy-eight piglets born to vaccinated or non-vaccinated sows were divided into 8 groups. A proportion of the pigs with and a proportion of the pigs without passively acquired immunity were vaccinated at 21 days of age. All pigs except negative controls were challenged with PCV2b at 35 days post-vaccination and necropsied at 21 days post-challenge (dpc). The data indicates that both dam vaccination and piglet vaccination had similar efficacies in reducing PCV2 viral loads and antigen levels in the growing pigs. Interestingly, dam vaccination alone did result in significantly (P <0.05) lower anti-PCV2-antibodies levels at challenge in piglets from dams immunized with VAC2 compared to piglets from VAC1 immunized dams. When data obtained from the growing piglets that were vaccinated with VAC1 or VAC2 were compared, antibody levels and reduction of incidence of PCV2-antigen were not different; however, piglets vaccinated with VAC2 had reduced PCV2-DNA genomic copies in serum by 21 dpc. Vaccination of piglets with the same vaccine as was used on their dams did not appear to affect vaccine efficacy as piglets in these groups had anti-PCV2-antibody levels and PCV2 genomic copies similar to the groups where vaccine was administered to the piglets only. [Copyright &y& Elsevier]

Abstract: In the present work, 262 serum samples and 29 faeces pools from chickens coming from 29 healthy flocks were analysed by RT-PCR for detection of avian HEV and by ELISA using an aHEV derived antigen for detection of anti-HEV IgG. Additionally, other 300 randomly selected serum samples were also analysed by RT-PCR. Seven serum samples were positive to RNA detection. Sequence analysis of both the helicase and the capsid genes revealed that the Spanish isolates were clustered together and close related to those strains from the United States isolated from farms with HSS. On the serology study, 26/29 flocks had at least one positive animal (89.7%) and chickens older than 40 weeks were found to have higher seropositivities compared to the rest of age groups. Within positive farms, the proportion of positive animals ranged from 20% to 80%. This is the first report of aHEV sequences in chickens from Europe. Further studies are needed to elucidate the clinical significance of avian HEV infections in Europe. [Copyright &y& Elsevier]

Abstract: Porcine reproductive and respiratory syndrome virus (PRRSV) is the causative agent of a contagious disease characterized by reproductive failure in sows and respiratory disease in piglets. This infectious disease results in significant losses in the swine industry and specific anti-PRRSV drugs are needed. In this study, we evaluated a novel class of antisense compounds, peptide-conjugated phosphorodiamidate morpholino oligomers (P-PMOs), for their ability to suppress PRRSV replication in cell culture. P-PMOs are analogs of single-stranded DNA and contain a modified backbone that confers highly specific binding to RNA and resistance to nucleases. Of six P-PMOs tested, one (‘5UP1’), with sequence complementary to the 5′-terminal 21 nucleotides of the PRRSV genome, was found to be highly effective at reducing PRRSV replication in a specific and dose-dependent manner in CRL11171 cells in culture. 5UP1 treatment generated up to a 4.5log reduction in infectious PRRSV yield, while a control P-PMO had no effect on viral titer. Immunofluorescence assay with an anti-PRRSV monoclonal antibody confirmed the titer observations. The sequence-specificity of 5UP1 effect was confirmed in part by a cell-free luciferase reporter assay system, which showed that 5UP1-mediated inhibition of translation decreased if the target-RNA contained mispairings in relation to the 5UP1 P-PMO. Real-time RT-PCR showed that the production of PRRSV negative-sense RNA was reduced if 5UP1 was added to cells at up to 6h post-virus inoculation. Cell viability assays detected no cytotoxicity of 5UP1 within the concentration-range of this study. These results indicate that P-PMO 5UP1 has potential as an anti-PRRSV agent. [Copyright &y& Elsevier]