Xinpeng Jiang

Pathogenic infections caused by intestinal microecological imbalance pose a critical threat to livestock breeding and human health. Multiple probiotic functions of Lacticaseibacillus casei (L. casei), an important probiotic, are modulated by pyrR-mediated pyrimidine metabolism. This study used L. casei isolated from the intestines of Min pigs (a local pig breed from northeastern China) and its pyrR gene knockout mutant (named L. casei ΔpyrR, ΔpyrR) to investigate their antibacterial, anti-inflammatory, and antioxidant capacities. The results showed that the mutant exhibited significantly attenuated effects compared with the wild-type in disrupting pre-formed biofilms, damaging bacterial morphology, and downregulating the expression of related genes (biofilm and flagellar genes) in Staphylococcus aureus (S. aureus) and Salmonella typhimurium (S. typhimurium). The mutant-derived supernatant also exhibited impaired anti-inflammatory effects in S. typhimurium-challenged IPEC-J2 cells: it was less effective at restraining pathogen-induced IL-1β upregulation and boosting the production of host-derived TGF-β and IL-10, accompanied by altered regulation of the host STING signaling pathway. However, existing data cannot fully distinguish whether STING alteration corresponds to suppressed inflammation or impaired immunity. Additionally, pyrimidine metabolism in L. casei suppresses pathogen-induced reactive oxygen species (ROS) accumulation. These findings are consistent with pyrR-mediated pyrimidine synthesis contributing to the probiotic functions of L. casei, providing an experimental basis for optimizing probiotic preparations and substituting antibiotics.

In recent years, outbreaks of Seneca Valley virus (SVV) in pig farms have raised concerns about disease resistance in different pig breeds. Min pigs are an excellent local pig breed in China, but the breed’s strong disease resistance mechanism has not been clearly investigated. In this study, Min pigs and Landrace pigs were challenged with SVV, and the differences in pathogenicity between SVV-infected Min and Landrace pigs were evaluated in terms of production performance, survival rate, immune cell activity, pathological changes, viral titer, and cytokine expression. The results show that the mortality rate in Min pigs was significantly lower than that in Landrace pigs without substantial weight loss. The copy number of SVV RNA in the intestinal mucosa of Min pigs was lower than that in Landrace pigs. Additionally, the IgA and IgG titers in Min pigs were higher than those in Landrace pigs. Both the absolute number and percentage of M1 macrophages were elevated in Min pigs relative to Landrace pigs. This study is the first to identify differences in macrophage activity between SVV-infected Min pigs and Landrace pigs. The presented results indicate the potential research value of studying innate immunity differences in disease resistance between pig breeds.

Seneca Valley virus (SVV) infection has recently disseminated across pig farms in Canada, America, and China. The SVV has been identified in humans, rodents, and houseflies. Although cross‐species transmission events may lead to limited subsequent transmission, sustained outbreaks have been observed in new mammalian hosts. Thus, in our study, we utilized molecular characteristics, pathological examination, and the immune response to ascertain whether mink could serve as a novel mammalian host for SVV. Here, our study utilized a porcine strain of SVV to infect minks orally, resulting in pathological changes in the intestines. In addition, SVV could stimulate a specific neutralizing antibody response. The neutralizing antibody against SVV has also been found in mink through an epidemiological investigation in Heilongjiang Province. This study highlights the role of SVV infection in minks as an impetus for viral evolution, which poses potential threats to livestock, public health, and economic prosperity.

Lacticaseibacillus is one of the predominant microorganisms in gut from human and animal, and the lacticaseibacillus have effective applications against the viral diarrhea of piglets in the farm. However, the function and the concrete cell single pathways of the active ingredient from lacticaseibacillus was not clear within anti-infection in the postbiotics research. Here, we compared the biological function of extracellular polysaccharides (EPS) purified from lacticaseibacillus casei (L. casei) and gene editing lacticaseibacillus casei with the CRISPER-Cas9 technology, which were with the ability of antioxidation and anti-inflammation, and the EPS could also inhibit the ROS production within the Porcine Small Intestinal Epithelial Cells-J2 (IPEC-J2). Interestingly, we found that both of EPS and genome editing lacticaseibacillus casei could specifically target the IFN-λ expression in the IPEC-J2, which was beneficial against the PEDV infection in the virus replication and production with the qRT-PCR and indirect immunofluorescence methods. Finally, the STAT3 cell single pathway was stimulated to transcribe IFN-λ with the EPS to elucidate the detailed mechanism of activating type III IFN signals receptor of IL-10R2, which play the function between anti-inflammation and anti-virus in the PEDV infection. Taken together, our research linked a postbiotics of EPS with the antiviral infection of PEDV, which suggest that the lacticaseibacillus itself still have displayed the potential immunomodulatory activities, and highlight the immunomodulatory potential of EPS-producing microbes. Graphical Abstract

Lactobacillus casei (L. casei) has four possible mechanisms: antimicrobial antagonism, competitional adhesion, immunoregulation, and the inhibition of bacterial toxins. To delineate the metabolic reactions of nucleotides from L. casei that are associated with mechanisms of inhibiting pathogens and immunoregulation, we report that a PyrR-deficient L. casei strain was constructed using the CRISPR-Cas9^D10A tool. Furthermore, there were some changes in its basic biological characterization, such as its growth curve, auxotroph, and morphological damage. The metabolic profiles of the supernatant between the PyrR-deficient and wild strains revealed the regulation of the synthesis of genetic material and of certain targeting pathways and metabolites. In addition, the characteristics of the PyrR-deficient strain were significantly altered as it lost the ability to inhibit the growth of pathogens. Moreover, we identified PyrR-regulating pyrimidine biosynthesis, which further improved its internalization and colocalization with macrophages. Evidence shows that the PyrR gene is a key active component in L. casei supernatants for the regulation of pyrimidine biosynthesis against a wide range of pathogens.

In China, the national-level protected pig, the Min pig, is characterized by the development of secondary hairs and hair follicles in winter. Factors that dominate the genotype in the growth of secondary hairs are not clear through the concrete cell signaling pathways. This study compared hair phenotypes based on morphological structure, transcriptomics, and potential targeting molecules in the breeds of Min, Berkshire, and Yorkshire pigs. The results indicated that Min pigs have specific characteristics for the growth of secondary hairs compared with the Berkshire and Yorkshire pigs. The transcriptome analyses and quantitative reverse transcription-polymerase chain reaction results revealed that secondary hair growth was activated by follicle stem cells. The specific inhibitors of Wnt and BMP were studied using respective signals. The density of follicles, activity of follicle stem cells, and relative gene expression results have shown that Wnt and BMP stimulate the activity of follicle stem cells, and the Wnt signaling molecule has a significantly better effect than the BMP signaling molecule on stem cells. Wnt and BMP can promote the growth of local secondary hair and gene expression. Therefore, this study was conducted to verify the development mechanisms of secondary hairs, which have potential applications in laboratory animals and comparative medicine.

The porcine epidemic diarrhea virus, PEDV, which causes diarrhea, vomiting and death in piglets, causes huge economic losses. Therefore, understanding how to induce mucosal immune responses in piglets is essential in the mechanism and application against PEDV infection with mucosal immunity. A method of treatment in our research was used to make an oral vaccine that packaged the inactive PEDV with microencapsulation, which consisted of sodium alginate and chitosan, and adapted the condition of the gut in mice. The in vitro release experiment of microcapsules showed that inactive PEDV was not only easily released in saline and acid solutions but also had an excellent storage tolerance, and was suitable for use as an oral vaccine. Interestingly, both experimental groups with different doses of inactive virus enhanced the secretion of specific antibodies in the serum and intestinal mucus, which caused the effective neutralization against PEDV in the Vero cell by both IgG and IgA, respectively. Moreover, the microencapsulation could stimulate the differentiation of CD11b+ and CD11c+ dendritic cells, which means that the microencapsulation was also identified as an oral adjuvant to help phagocytosis of dendritic cells in mice. Flow cytometry revealed that the B220⁺ and CD23⁺ of the B cells could significantly increase antibody production with the stimulation from the antigens’ PEDV groups, and the microencapsulation could also increase the cell viability of B cells, stimulating the secretion of antibodies such as IgG and IgA in mice. In addition, the microencapsulation promoted the expression of anti-inflammatory cytokines, such as IL-10 and TGF-β. Moreover, proinflammatory cytokines, such as IL-1, TNF-α, and IL-17, were inhibited by alginate and chitosan in the microencapsulation groups compared with the inactivated PEDV group. Taken together, our results demonstrate that the microparticle could play the role of mucosal adjuvant, and release inactivated PEDV in the gut, which can effectively stimulate mucosal and systemic immune responses in mice.