Ganglioside GM3 deficiency enhances mast cell sensitivity.

Mast cells are a significant source of cytokines and chemokines that play a role in pathological processes. Gangliosides, which are complex lipids with a sugar chain, are present in all eukaryotic cell membranes and comprise lipid rafts. Ganglioside GM3, the first ganglioside in the synthetic pathway, is a common precursor of the specifying derivatives and is well known for its various functions in biosystems. Mast cells contain high levels of gangliosides; however, the involvement of GM3 in mast cell sensitivity is unclear. Therefore, in this study, we elucidated the role of ganglioside GM3 in mast cells and skin inflammation. GM3 synthase (GM3S)-deficient mast cells showed cytosolic granule topological changes and hyperactivation upon IgE-DNP stimulation without affecting proliferation and differentiation. Additionally, inflammatory cytokine levels increased in GM3S-deficient bone marrow-derived mast cells (BMMC). Furthermore, GM3S-KO mice and GM3S-KO BMMC transplantation showed increased skin allergic reactions. Besides mast cell hypersensitivity caused by GM3S deficiency, membrane integrity decreased and GM3 supplementation rescued this loss of membrane integrity. Additionally, GM3S deficiency increased the phosphorylation of p38 mitogen-activated protein kinase. These results suggest that GM3 increases membrane integrity, leading to the suppression of the p38 signalling pathway in BMMC and contributing to skin allergic reaction.

The Swine Erysipelas Vaccine SER-ME Effectively Protects Pigs against Challenge with the Erysipelothrix rhusiopathiae M203/I257 SpaA-Type Variant.

Erysipelothrix rhusiopathiae causes swine erysipelas (SE). Sporadic SE outbreaks in Japan are mostly caused by the E. rhusiopathiae serovar 1a variant featured by methionine (M) and isoleucine (I) at amino acid positions 203 and 257 of the surface protective antigen (Spa) A protein (M203/I257 SpaA-type). To determine if current vaccines are effective against infection with this variant in pigs, one representative inactivated vaccine, SER-ME (containing E. rhusiopathiae serovar 2a), was evaluated. All vaccinated pigs survived without any apparent clinical signs after lethal challenge with the Fujisawa reference strain or the variant. This indicates that the SER-ME vaccine effectively protects pigs against the infection of E. rhusiopathiae M203/I257 SpaA-type variant. Current vaccines in Japan, including SER-ME, suggest that outbreaks in Japan are unlikely caused by vaccine failure.

Comparative study of the phenotype and virulence of recent serovar 1a, 1b, and 2a isolates of Erysipelothrix rhusiopathiae in Japan.

Erysipelothrix rhusiopathiae causes swine erysipelas (SE) and is classified -into 16 serovars based on cell surface antigens. Our previous study suggested that recent SE outbreaks were mostly caused by serovar 1a of E. rhusiopathiae with the surface protective antigen (Spa)A protein characterized by methionine and isoleucine at positions 203 and 257 (M203/I257 SpaA). In this study, four recent E. rhusiopathiae isolates comprising two serovar 1a with M203/I257 SpaA strains (2012 Miyazaki and 2012 Chiba), one serovar 1b strain (2015 Miyazaki), and one serovar 2a strain (2012 Nagano) were compared with each other and with the serovar 1a Fujisawa reference strain regarding in vitro phenotypes and in vivo virulence in mice and pigs. The serovar 1b and 2a strains, which are the less prevalent strains in the field in Japan, showed lower growth in liquid culture and lower virulence in animals than the serovar 1a variants. Adhesion of the serovar 2a strain to porcine endothelial cells was weaker than that of the serovar 1a and 1b strains. Several advantages of serovar 1a strains were found, but no plausible cause of the M203/I257 SpaA type variants to be selected for the most prevalent strains among serovar 1a strains was identified in this study.

Isolation and characterization of Helicobacter suis from human stomach.

Helicobacter suis, a bacterial species naturally hosted by pigs, can colonize the human stomach in the context of gastric diseases such as gastric mucosa-associated lymphoid tissue (MALT) lymphoma. Because H. suis has been successfully isolated from pigs, but not from humans, evidence linking human H. suis infection to gastric diseases has remained incomplete. In this study, we successfully in vitro cultured H. suis directly from human stomachs. Unlike Helicobacter pylori, the viability of H. suis decreases significantly on neutral pH; therefore, we achieved this using a low-pH medium for transport of gastric biopsies. Ultimately, we isolated H. suis from three patients with gastric diseases, including gastric MALT lymphoma. Successful eradication of H. suis yielded significant improvements in endoscopic and histopathological findings. Oral infection of mice with H. suis clinical isolates elicited gastric and systemic inflammatory responses; in addition, progression of gastric mucosal metaplasia was observed 4 mo postinfection. Because H. suis could be isolated from the stomachs of infected mice, our findings satisfied Koch's postulates. Although further prospective clinical studies are needed, H. suis, like H. pylori, is likely a gastric pathogen in humans. Furthermore, comparative genomic analysis of H. suis using complete genomes of clinical isolates revealed that the genome of each H. suis isolate contained highly plastic genomic regions encoding putative strain-specific virulence factors, including type IV secretion system-associated genes, and that H. suis isolates from humans and pigs were genetically very similar, suggesting possible pig-to-human transmission.

Serovars and SpaA Types of Erysipelothrix rhusiopathiae Isolated from Pigs in Japan from 2012 to 2019.

Erysipelothrix rhusiopathiae causes swine erysipelas (SE), which results in considerable economic loss on pig farms. During SE outbreaks that occurred sporadically from 2008 to 2011 in Japan, new E. rhusiopathiae strains were isolated with a specific surface protective antigen (Spa)A protein characterized by methionine at position 203 and isoleucine at position 257 (M203/I257 SpaA type). To determine whether strains with the M203/I257 SpaA type are still prevalent in Japan, we collected 79 strains of E. rhusiopathiae from pigs showing various SE symptoms from 2012 to 2019 and classified them based on serovar typing, spaA gene sequence analysis, and lineage typing. We found that the majority of recent E. rhusiopathiae strains (59/79) belonged to the serovar 1a strain, and that the M203/I257 SpaA type (56/59) was predominant continuing from 2008 to 2011. Furthermore, serovar 1a strains with IVb-1 and IVb-2 lineages that had been isolated in specific regions of Japan were no longer local but were found across Japan. The pathogenicity of recent isolates tested in mice was not significantly changed when compared to that of previously isolated strains. Our results suggest that recent SE outbreaks were not due to changes in the SpaA protein or to altered virulence of E. rhusiopathiae but were rather caused by the persistent presence of E. rhusiopathiae with the M203/I257 SpaA type.

Complete Genome Sequence of Mycoplasma bovis Strain KG4397, Isolated from Cattle in Japan.

Mycoplasma bovis is a major bacterial pathogen that causes pneumonia, mastitis, and arthritis in cattle. In this study, we performed whole-genome sequencing of an M. bovis strain isolated in Japan for the first time and announce the complete genome sequence of strain KG4397, which caused respiratory diseases in cattle in 2012.