Expression of RNautophagy/DNautophagy-related genes is regulated under control of an innate immune receptor.

Double-stranded RNA (dsRNA) is a molecular pattern uniquely produced in cells infected with various viruses as a product or byproduct of replication. Cells detect such molecules, which indicate non-self invasion, and induce diverse immune responses to eliminate them. The degradation of virus-derived molecules can also play a role in the removal of pathogens and suppression of their replication. RNautophagy and DNautophagy are cellular degradative pathways in which RNA and DNA are directly imported into a hydrolytic organelle, the lysosome. Two lysosomal membrane proteins, SIDT2 and LAMP2C, mediate nucleic acid uptake via this pathway. Here, we showed that the expression of both SIDT2 and LAMP2C is selectively upregulated during the intracellular detection of poly(I:C), a synthetic analog of dsRNA that mimics viral infection. The upregulation of these two gene products upon poly(I:C) introduction was transient and synchronized. We also observed that the induction of SIDT2 and LAMP2C expression by poly(I:C) was dependent on MDA5, a cytoplasmic innate immune receptor that directly recognizes poly(I:C) and induces various antiviral responses. Finally, we showed that lysosomes can target viral RNA for degradation via RNautophagy and may suppress viral replication. Our results revealed a novel degradative pathway in cells as a downstream component of the innate immune response and provided evidence suggesting that the degradation of viral nucleic acids via RNautophagy/DNautophagy contributes to the suppression of viral replication.

First detection of porcine circovirus type 3 in Japan.

Porcine circovirus associated diseases (PCVAD) have multiple manifestations that have been attributed to porcine circovirus type 2 (PCV2). Recently, a novel porcine circovirus, PCV type 3 (PCV3), was identified in pigs with systemic inflammation of unknown etiology. In this study, we tried to detect the PCV3 genome in tissue samples collected from Japanese pig herds in 2016. The PCV3 genome was detected by PCR in 7 of 73 samples. The homology between each Japanese strain was 99.5% for the full-length sequence and 98.9 to 99.2% for the open reading frame 2. These results suggest that PCV3 has already invaded Japanese pig farms.

Efficacy of genogroup 1 based porcine epidemic diarrhea live vaccine against genogroup 2 field strain in Japan.

BACKGROUND: Porcine epidemic diarrhea (PED) is a lethal infectious disease in suckling piglets with symptoms including watery diarrhea caused by PED virus (PEDV). Since the late 1990's, live vaccines based on genogroup 1 virus have been used in Japan, and a significant amount of the vaccine has been used even after new genogroups invaded in 2013. In this study, we evaluated the effect of a conventional PED live vaccine on a newly prevalent genogroup 2 field strain in experimental and field situations. METHODS: Two pregnant sows were administered twice the live vaccine before farrowing. A pregnant sow was served as a negative control. All newborn piglets were challenged with the genogroup 2 virus, and clinical signs were monitored for 7 days post challenge. PEDV-specific immune responses in serum and milk of the sows were assayed by virus neutralization assay. The efficacy of PED live vaccine in vaccinated or non-vaccinated farms was evaluated by comparing the mortality rate of suckling piglets after the onset of PED. RESULTS: The challenged piglets exhibited watery diarrhea with or without vaccination. However, the clinical score of piglets born from vaccinated sows significantly improved after the 4th day of the challenge. The survival rate of piglets in the vaccinated group at the end of the experimental period was 80%, whereas in the control group was 0%. Neutralizing antibody titers in serum and milk of control sow was negative throughout the experimental period, whereas high titers were observed in the vaccinated sows. The vaccinated farms significantly reduced the mortality rate of suckling piglets after the onset of PED, compared to farms not vaccinated. CONCLUSIONS: The conventional PED live vaccine induced the lactogenic immunity to vaccinated sows and showed partial protection against the genogroup 2 virus both under the experimental and field conditions.

Oral rice-based vaccine induces passive and active immunity against enterotoxigenic E. coli-mediated diarrhea in pigs.

Enterotoxigenic Escherichia coli (ETEC) causes severe diarrhea in both neonatal and weaned pigs. Because the cholera toxin B subunit (CTB) has a high level of amino acid identity to the ETEC heat-labile toxin (LT) B-subunit (LTB), we selected MucoRice-CTB as a vaccine candidate against ETEC-induced pig diarrhea. When pregnant sows were orally immunized with MucoRice-CTB, increased amounts of antigen-specific IgG and IgA were produced in their sera. CTB-specific IgG was secreted in the colostrum and transferred passively to the sera of suckling piglets. IgA antibodies in the colostrum and milk remained high with a booster dose after farrowing. Additionally, when weaned minipigs were orally immunized with MucoRice-CTB, production of CTB-specific intestinal SIgA, as well as systemic IgG and IgA, was induced. To evaluate the cross-protective effect of MucoRice-CTB against ETEC diarrhea, intestinal loop assay with ETEC was conducted. The fluid volume accumulated in the loops of minipigs immunized with MucoRice-CTB was significantly lower than that in control minipigs, indicating that MucoRice-CTB-induced cross-reactive immunity could protect weaned pigs from diarrhea caused by ETEC. MucoRice-CTB could be a candidate oral vaccine for inducing both passive and active immunity to protect both suckling and weaned piglets from ETEC diarrhea.