Mesomycoplasma ovipneumoniae from goats with respiratory infection: pathogenic characteristics, population structure, and genomic features.

BACKGROUND: Mycoplasma ovipneumoniae is a critical pathogen that causes respiratory diseases that threaten Caprini health and cause economic damage. A genome-wide study of M. ovipneumoniae will help understand the pathogenic characteristics of this microorganism. RESULTS: Toxicological pathology and whole-genome sequencing of nine M. ovipneumoniae strains isolated from goats were performed using an epidemiological survey. These strains exhibited anterior ventral lung consolidation, typical of bronchopneumonia in goats. Average nucleotide identity and phylogenetic analysis based on whole-genome sequences showed that all M. ovipneumoniae strains clustered into two clades, largely in accordance with their geographical origins. The pan-genome of the 23 M. ovipneumoniae strains contained 5,596 genes, including 385 core, 210 soft core, and 5,001 accessory genes. Among these genes, two protein-coding genes were annotated as cilium adhesion and eight as paralog surface adhesins when annotated to VFDB, and no antibiotic resistance-related genes were predicted. Additionally, 23 strains carried glucosidase-related genes (ycjT and group_1595) and glucosidase-related genes (atpD_2), indicating that M. ovipneumoniae possesses a wide range of glycoside hydrolase activities. CONCLUSIONS: The population structure and genomic features identified in this study will facilitate further investigations into the pathogenesis of M. ovipneumoniae and lay the foundation for the development of preventive and therapeutic methods.

Replication of Porcine Astrovirus Type 1-Infected PK-15 Cells In Vitro Affected by RIG-I and MDA5 Signaling Pathways.

The interferon (IFN) system is an extremely powerful antiviral response in animal cells. The subsequent effects caused by porcine astrovirus type 1 (PAstV1) IFN activation are important for the host's response to viral infections. Here, we show that this virus, which causes mild diarrhea, growth retardation, and damage of the villi of the small intestinal mucosa in piglets, induces an IFN response upon infection of PK-15 cells. Although IFN-ß mRNA was detected within infected cells, this response usually occurs during the middle stages of infection, after genome replication has taken place. Treatment of PAstV1-infected cells with the interferon regulatory factor 3 (IRF3) inhibitor BX795 decreased IFN-ß expression, whereas the nuclear factor kappa light chain enhancer of activated B cells (NF-κB) inhibitor BAY11-7082 did not. These findings indicate that PAstV induced the production of IFN-ß via IRF3-mediated rather than NF-κB-mediated signaling pathways in PK-15 cells. Moreover, PAstV1 increased the protein expression levels of retinoic acid-inducible gene I (RIG-I) and melanoma differentiation-associated protein 5 (MDA5) in PK-15 cells. The knockdown of RIG-I and MDA5 decreased the expression levels of IFN-ß and the viral loads and increased the infectivity of PAstV1. In conclusion, PAstV1 induced the production of IFN-ß via the RIG-I and MDA5 signaling pathways, and the IFN-ß produced during PAstV1 infection inhibited viral replication. These results will help provide new evidence that PAstV1-induced IFNs may protect against PAstV replication and pathogenesis. IMPORTANCE Astroviruses (AstVs) are widespread and can infect multiple species. Porcine astroviruses produce mainly gastroenteritis and neurological diseases in pigs. However, astrovirus-host interactions are less well studied, particularly with respect to their antagonism of IFN. Here, we report that PAstV1 acts via IRF3 transcription pathway activation of IFN-ß. In addition, the knockdown of RIG-I and MDA5 attenuated the production of IFN-ß induced by PAstV1 in PK-15 cells and increased efficient viral replication in vitro. We believe that these findings will help us to better understand the mechanism of how AstVs affect the host IFN response.

Proteomic analysis of exosome-like vesicles from Fasciola gigantica adult worm provides support for new vaccine targets against fascioliasis.

BACKGROUND: Extracellular vesicles (EVs) released by helminths play an important role in parasite-host communication. However, little is known about the characteristics and contents of the EVs of Fasciola gigantica, a parasitic flatworm that causes tropical fascioliasis. A better understanding of EVs released by F. gigantica will help elucidate the mechanism of F. gigantica-host interaction and facilitate the search for new vaccine candidates for the control and treatment of fascioliasis. METHODS: Two different populations of EVs (15k EVs and 100k EVs) were purified from adult F. gigantica culture media by ultracentrifugation. The morphology and size of the purified EVs were determined by transmission electron microscopy (TEM) and by the Zetasizer Nano ZSP high performance particle characterization system. With the aim of identifying diagnostic markers or potential vaccine candidates, proteins within the isolated 100k EVs were analyzed using mass spectrometry-based proteomics (LC-MS/MS). Mice were then vaccinated with excretory/secretory products (ESPs; depleted of EVs), 15k EVs, 100k EVs and recombinant F. gigantica heat shock protein 70 (rFg-HSP70) combined with alum adjuvant followed by challenge infection with F. gigantica metacercariae. Fluke recovery and antibody levels were used as measures of vaccine protection. RESULTS: TEM analysis and nanoparticle tracking analysis indicated the successful isolation of two subpopulations of EVs (15k EVs and 100k EVs) from adult F. gigantica culture supernatants using differential centrifugation. A total of 755 proteins were identified in the 100k EVs. Exosome biogenesis or vesicle trafficking proteins, ESCRT (endosomal sorting complex required for transport) pathway proteins and exosome markers, heat shock proteins and 14-3-3 proteins were identified in the 100k EVs. These results indicate that the isolated 100k EVs were exosome-like vesicles. The functions of the identified proteins may be associated with immune regulation, immune evasion and virulence. Mice immunized with F. gigantica ESPs, 15k EVs, 100k EVs and rFg-HSP70 exhibited a reduction in fluke burden of 67.90%, 60.38%, 37.73% and 56.6%, respectively, compared with the adjuvant control group. The vaccination of mice with F. gigantica 100k EVs, 15k EVs, ESP and rFg-HSP70 induced significant production of specific immunoglobulins in sera, namely IgG, IgG1 and IgG2a. CONCLUSION: The results of this study suggest that proteins within the exosome-like vesicles of F. gigantica have immunomodulatory, immune evasion and virulence functions. This knowledge may lead to new strategies for immunotherapy, vaccination and the diagnosis of fascioliasis.

Immunological pathogenesis of Bovine E. coli infection in a model of C. elegans.

BACKGROUND: Cattle industry is critical for China's livestock industry, whereas E. coli infection and relevant diseases could lead huge economic loss. Traditional mammalian models would be costly, time consuming and complicated to study pathological changes of bovine E. coli. There is an urgent need for a simple but efficient animal model to quantitatively evaluate the pathological changes of bovine-derived E. coli in vivo. Caenorhabditis elegans (C. elegans) has a broad host range of diverse E. coli strains with advantages, including a short life cycle, a simple structure, a transparent body which is easily visualized, a well-studied genetic map, an intrinsic immune system which is conservable with more complicated mammalians. RESULTS: Here, we considered that O126 was the dominant serotype, and a total of 19 virulence factors were identified from 41 common E. coli virulence factors. Different E. coli strains with diverse pathogenicity strengths were tested in C. elegans in E. coli with higher pathogenicity (EC3/10), Nsy-1, Sek-1 and Pmk-1 of the p38 MAPK signaling pathway cascade and the expression of the antimicrobial peptides Abf-3 and Clec-60 were significantly up-regulated comparing with other groups. E. coli with lower pathogenicity (EC5/13) only activated the expression of Nsy-1 and Sek-1 genes in the p38 MAPK signaling pathway, Additionally, both groups of E. coli strains caused significant upregulation of the antimicrobial peptide Spp-1. CONCLUSION: Thirteen E. coli strains showed diverse pathogenicity in nematodes and the detection rate of virulence factors did not corresponding to the virulence in nematodes, indicating complex pathogenicity mechanisms. We approved that C. elegans is a fast and convenient detection model for pathogenic bacteria virulence examinations.

GTPase-activating protein-binding protein 1 (G3BP1) plays an antiviral role against porcine epidemic diarrhea virus.

Porcine epidemic diarrhoea virus (PEDV) is a single-stranded, positive-sense RNA virus that belongs to the Coronaviridae. PEDV causes severe diarrhoea and dehydration in nursing piglets, which leads to significant economic losses to the swine industry worldwide. Stress granules (SGs) are sites of mRNA storage that are formed under various stress conditions including viral infections. Increasing evidence suggests that SGs function in antiviral innate immunity of host cells to limit virus replication. Ras-GTPase-activating protein (SH3 domain) binding protein 1 (G3BP1) is a key stress granule-resident protein that nucleates stress granule assembly. Depletion of G3BP1 inhibits SGs formation and overexpression of G3BP1 nucleates SGs assembly. We observed that knockdown of G3BP1 by silencing RNA significantly increased PEDV replication. Overexpression of exogenous G3BP1, on the other hand, lowered virus replication by 100-fold compared to vector control. An increase in the levels of mRNAs of pro-inflammatory cytokines such as interleukin-1ß (IL-1ß) and tumor necrosis factor-α (TNF-α) was also observed in PEDV-infected G3BP1 depleted cells compared to PEDV-infected control cells. Taken together, our results suggest that G3BP1 plays an antiviral role and impairs PEDV replication.