DNA vaccine encoding the major virulence factors of Shiga toxin type 2e (Stx2e)-expressing Escherichia coli induces protection in mice

Oral Immunization with Attenuated Salmonella Choleraesuis Expressing the FedF Antigens Protects Mice against the Shiga-Toxin-Producing Escherichia coli Challenge

Edema disease (ED) is a severe and lethal infectious ailment in swine, stemming from Shiga-toxin-producing Escherichia coli (STEC). An efficient, user-friendly, and safe vaccine against ED is urgently required to improve animal welfare and decrease antibiotic consumption. Recombinant attenuated Salmonella vaccines (RASV) administered orally induce both humoral and mucosal immune responses to the immunizing antigen. Their potential for inducing protective immunity against ED is significant through the delivery of STEC antigens. rSC0016 represents an enhanced recombinant attenuated vaccine vector designed for Salmonella enterica serotype Choleraesuis. It combines sopB mutations with a regulated delay system to strike a well-balanced equilibrium between host safety and immunogenicity. We generated recombinant vaccine strains, namely rSC0016 (pS-FedF) and rSC0016 (pS-rStx2eA), and assessed their safety and immunogenicity in vivo. The findings demonstrated that the mouse models immunized with rSC0016 (pS-FedF) and rSC0016 (pS-rStx2eA) generated substantial IgG antibody responses to FedF and rStx2eA, while also provoking robust mucosal and cellular immune responses against both FedF and rStx2eA. The protective impact of rSC0016 (pS-FedF) against Shiga-toxin-producing Escherichia coli surpassed that of rSC0016 (pS-rStx2eA), with percentages of 83.3%. These findings underscore that FedF has greater suitability for vaccine delivery via recombinant attenuated Salmonella vaccines (RASVs). Overall, this study provides a promising candidate vaccine for infection with STEC.

C500 variants conveying complete mucosal immunity against fatal infections of pigs with Salmonella enterica serovar Choleraesuis C78-1 or F18+ Shiga toxin-producing Escherichia coli

Salmonella enterica serovar Choleraesuis (S. Choleraesuis) C500 strain is a live, attenuated vaccine strain that has been used in China for over 40 years to prevent piglet paratyphoid. However, this vaccine is limited by its toxicity and does not offer protection against diseases caused by F18+ Shiga toxin-producing Escherichia coli (STEC), which accounts for substantial economic losses in the swine industry. We recently generated a less toxic derivative of C500 strain with both asd and crp deletion (S. Choleraesuis C520) and assessed its efficacy in mice. In addition, we demonstrate that C520 is also less toxic in pigs and is effective in protecting pigs against S. Choleraesuis when administered orally. To develop a vaccine with a broader range of protection, we prepared a variant of C520 (S. Choleraesuis C522), which expresses rSF, a fusion protein comprised of the fimbriae adhesin domain FedF and the Shiga toxin-producing IIe B domain antigen. For comparison, we also prepared a control vector strain (S. Choleraesuis C521). After oral vaccination of pigs, these strains contributed to persistent colonization of the intestinal mucosa and lymphoid tissues and elicited both cytokine expression and humoral immune responses. Furthermore, oral immunization with C522 elicited both S. Choleraesuis and rSF-specific immunoglobulin G (IgG) and IgA antibodies in the sera and gut mucosa, respectively. To further evaluate the feasibility and efficacy of these strains as mucosal delivery vectors via oral vaccination, we evaluated their protective efficacy against fatal infection with S. Choleraesuis C78-1, as well as the F18+ Shiga toxin-producing Escherichia coli field strain Ee, which elicits acute edema disease. C521 conferred complete protection against fatal infection with C78-1; and C522 conferred complete protection against fatal infection with both C78-1 and Ee. Our results suggest that C520, C521, and C522 are competent to provide complete mucosal immune protection against fatal infection with S. Choleraesuis in swine and that C522 equally qualifies as an oral vaccine vector for protection against F18+ Shiga toxin-producing Escherichia coli.

A novel Salmonella strain inactivated by a regulated autolysis system and expressing the B subunit of Shiga toxin 2e efficiently elicits immune responses and confers protection against virulent Stx2e-producing Escherichia coli

BACKGROUND

Salmonella Typhimurium (S. Typhimurium) inactivated by a regulated autolysis system was genetically engineered to express the homo-pentameric B subunit of Shiga toxin 2e (Stx2eB) on its surface. To prepare a strain able to yield autolyzed Salmonella bearing Stx2eB, the plasmid pJHL184 harboring stx _2eB gene was transformed into the attenuated S. Typhimurium strain, JOL1454. Stx2eB subcloned into the antigen delivery cassette of the plasmid was expressed as fusion protein with the outer membrane protein RESULTS: The expression of Stx2eB fused to the signal peptide in JOL1454 was validated by immunoblot analysis. To determine the immunogenicity of JOL1454, female BALB/c mice were intramuscularly injected with 1 × 10⁸ CFU of the inactivated cells at weeks 0 and 2. Significantly elevated levels of IgG and IgA specific to Stx2eB was observed at weeks 4 and 6 post-immunization (PI) (P <0.05). Proportion of CD3⁺CD4⁺ T lymphocyte subpopulation was also significantly augmented in in vivo stimulated splenocytes relative to that in the control group. The increased titers of IgG1 and IgG2a, and of immunomodulatory cytokines indicated that the immunization elicited Th1 and Th2 immune responses. Further, immunomodulatory cytokine genes (IL-6, IL-17A, IL21 and JOL1454) efficiently upregulated in naïve porcine peripheral blood mononuclear cells (PBMCs) pulsed with JOL1454. At week 6 PI, following the challenge with a virulent Stx2e-producing Escherichia coli in the mice, all immunized mice survived whereas approximately 30% of the mice in the control group died.

CONCLUSIONS

JOL1454 provided superior immunogenicity and effective protection against challenge with a sublethal dose, which demonstrates its potential as a candidate vaccine against edema disease.

Intestinal Microbiota-Derived GABA Mediates Interleukin-17 Expression during Enterotoxigenic Escherichia coli Infection

Intestinal microbiota has critical importance in pathogenesis of intestinal infection; however, the role of intestinal microbiota in intestinal immunity during enterotoxigenic Escherichia coli (ETEC) infection is poorly understood. The present study tested the hypothesis that the intestinal microbiota is associated with intestinal interleukin-17 (IL-17) expression in response to ETEC infection. Here, we found ETEC infection induced expression of intestinal IL-17 and dysbiosis of intestinal microbiota, increasing abundance of γ-aminobutyric acid (GABA)-producing Lactococcus lactis subsp. lactis. Antibiotics treatment in mice lowered the expression of intestinal IL-17 during ETEC infection, while GABA or L. lactis subsp. lactis administration restored the expression of intestinal IL-17. L. lactis subsp. lactis administration also promoted expression of intestinal IL-17 in germ-free mice during ETEC infection. GABA enhanced intestinal IL-17 expression in the context of ETEC infection through activating mechanistic target of rapamycin complex 1 (mTORC1)-ribosomal protein S6 kinase 1 (S6K1) signaling. GABA-mTORC1 signaling also affected intestinal IL-17 expression in response to Citrobacter rodentium infection and in drug-induced model of intestinal inflammation. These findings highlight the importance of intestinal GABA signaling in intestinal IL-17 expression during intestinal infection and indicate the potential of intestinal microbiota-GABA signaling in IL-17-associated intestinal diseases.

MicroRNA-127-5p regulates osteopontin expression and osteopontin-mediated proliferation of human chondrocytes

The aim of this study was to determine the specific microRNA (miRNA) that regulates expression of osteopontin (OPN) in osteoarthritis (OA). The potential regulatory miRNAs for OPN messenger RNA (mRNA) were predicted by miRNA prediction programs. Among eight potential regulatory miRNAs, miR-220b, miR-513a-3p and miR-548n increased, while miR-181a, miR-181b, miR-181c, miR-181d and miR-127-5p decreased in OA patients. miRNA-127-5p mimics suppressed OPN production as well as the activity of a reporter construct containing the 3'-UTR of human OPN mRNA. In addition, mutation of miR-127-5p binding site in the 3'-UTR of OPN mRNA abolished miR-127-5p-mediated repression of reporter activity. Conversely, treatment with miR-127-5p inhibitor increased reporter activity and OPN production. Interestingly, miR-127-5p inhibited proliferation of chondrocytes through OPN. In conclusion, miRNA-127-5p is an important regulator of OPN in human chondrocytes and may contribute to the development of OA.

Glutamine promotes intestinal SIgA secretion through intestinal microbiota and IL-13

SCOPE

Glutamine supplementation enhances secretory IgA (SIgA) production in the intestine, but the mechanism is largely unknown. We examined this issue using a mouse model.

METHODS AND RESULTS

In mouse model, glutamine supplementation increased both SIgA abundance in intestinal luminal contents and IgA(+) plasma cell numbers in the mouse ileum, and decreased bacterial loads in mouse mesenteric lymph nodes. Glutamine supplementation increased mouse ileal expression of cytokines associated with T cell-dependent and T cell-independent pathways of SIgA induction, including IL-5, IL-6, IL-13, transforming growth factor (TGF-β), a proliferation-inducing ligand (APRIL), B cell-activating factor (BAFF), vasoactive intestinal peptide (VIP) receptor, and retinal dehydrogenases. Injecting an IL-13 antibody during glutamine supplementation reduced J-chain expression in the mouse ileum. Glutamine supplementation increased bacterial invasion into the mouse ileal wall, while disrupting the mouse intestinal microbiota abrogated the influence of glutamine supplementation on SIgA secretion.

CONCLUSION

Glutamine supplementation appears to enhance SIgA secretion in the mouse intestine through the intestinal microbiota and subsequently through T cell-dependent and T cell-independent pathways.

Hydrogen-rich saline injection into the subarachnoid cavity within 2 weeks promotes recovery after acute spinal cord injury

Hydrogen can relieve tissue-damaging oxidative stress, inflammation and apoptosis. Injection of hydrogen-rich saline is an effective method for transporting molecular hydrogen. We hypothesized that hydrogen-rich saline would promote the repair of spinal cord injury induced by Allen's method in rats. At 0.5, 1, 2, 4, 8, 12 and 24 hours after injury, then once daily for 2 weeks, 0.25 mL/kg hydrogen-rich saline was infused into the subarachnoid space through a catheter. Results at 24 hours, 48 hours, 1 week and 2 weeks after injury showed that hydrogen-rich saline markedly reduced cell death, inflammatory cell infiltration, serum malondialdehyde content, and caspase-3 immunoreactivity, elevated serum superoxide dismutase activity and calcitonin gene-related peptide immunoreactivity, and improved motor function in the hindlimb. The present study confirms that hydrogen-rich saline injected within 2 weeks of injury effectively contributes to the repair of spinal cord injury in the acute stage.

Approaches to treatment of emerging Shiga toxin-producing Escherichia coli infections highlighting the O104:H4 serotype

Shiga toxin-producing Escherichia coli (STEC) are a group of diarrheagenic bacteria associated with foodborne outbreaks. Infection with these agents may result in grave sequelae that include fatality. A large number of STEC serotypes has been identified to date. E. coli serotype O104:H4 is an emerging pathogen responsible for a 2011 outbreak in Europe that resulted in over 4000 infections and 50 deaths. STEC pathogenicity is highly reliant on the production of one or more Shiga toxins that can inhibit protein synthesis in host cells resulting in a cytotoxicity that may affect various organ systems. Antimicrobials are usually avoided in the treatment of STEC infections since they are believed to induce bacterial cell lysis and the release of stored toxins. Some antimicrobials have also been reported to enhance toxin synthesis and production from these organisms. Various groups have attempted alternative treatment approaches including the administration of toxin-directed antibodies, toxin-adsorbing polymers, probiotic agents and natural remedies. The utility of antibiotics in treating STEC infections has also been reconsidered in recent years with certain modalities showing promise.

Dietary glutamate supplementation ameliorates mycotoxin-induced abnormalities in the intestinal structure and expression of amino acid transporters in young pigs

The purpose of this study was to investigate the hypothesis that dietary supplementation with glutamic acid has beneficial effects on growth performance, antioxidant system, intestinal morphology, serum amino acid profile and the gene expression of intestinal amino acid transporters in growing swine fed mold-contaminated feed. Fifteen pigs (Landrace×Large White) with a mean body weight (BW) of 55 kg were randomly divided into control group (basal feed), mycotoxin group (contaminated feed) and glutamate group (2% glutamate+contaminated feed). Compared with control group, mold-contaminated feed decreased average daily gain (ADG) and increased feed conversion rate (FCR). Meanwhile, fed mold-contaminated feed impaired anti-oxidative system and intestinal morphology, as well as modified the serum amino acid profile in growing pigs. However, supplementation with glutamate exhibited potential positive effects on growth performance of pigs fed mold-contaminated feed, ameliorated the imbalance antioxidant system and abnormalities of intestinal structure caused by mycotoxins. In addition, dietary glutamate supplementation to some extent restored changed serum amino acid profile caused by mold-contaminated feed. In conclusion, glutamic acid may be act as a nutritional regulating factor to ameliorate the adverse effects induced by mycotoxins.

Dietary L-proline supplementation confers immunostimulatory effects on inactivated Pasteurella multocida vaccine immunized mice

This study was conducted to determine the immunostimulatory effect of L-proline on inactivated vaccine immunized mice. Ninety-five female KM mice were randomly divided into five groups: (1) mice received dietary supplementation with 0.4% L-proline and immunized with inactivated vaccine (V-P group); (2) mice received dietary supplementation with 0.3% L-alanine (isonitrogenous control) and immunized with inactivated vaccine (V-A group, negative control); (3) mice were immunized with inactivated vaccine with oil adjuvant (V-O group, positive control); (4) mice were immunized with inactivated vaccine with aluminum hydroxide adjuvant (V-H group, positive control); (5) mice immunized with phosphate-buffered saline (control group). All mice were dead in the control group between 36 and 48 h post infection. Mice in the V-P group showed 100% protection after challenge with P. multocida serotype A (CQ2) at dose of 4.4 × 10(5) CFU (2LD50). Meanwhile, serum antibody titers in the V-P group were higher than those in the V-A group before infection and those in the V-A and V-O groups at 36 h post infection. Moreover, serum IL-1β levels in the V-P group were lower than those in V-O group. Furthermore, serum GSH-PX levels in the V-P group were higher than those in the V-A and V-O groups. Collectively, dietary proline supplementation confers beneficial immunostimulatory effects in inactivated P. multocida vaccine immunized mice.

Dietary supplementation with proline confers a positive effect in both porcine circovirus-infected pregnant and non-pregnant mice

Porcine circovirus type 2 (PCV2) is associated with various diseases that impose a significant economic burden on the swine industry. We hypothesised that nutritional supplementation with proline to enhance the immune response might be a useful prophylactic measure against PCV2 infection. To test this hypothesis, in the present study, we measured clinical data, including blood parameters, serum cytokine profile, PCV2 virus load in organs and serum, and microscopic lesions in the lung, liver and spleen, in both PCV2-infected pregnant and non-pregnant mice. Dietary supplementation with proline had no effect (P>0·05) on abortion rates in PCV2-infected pregnant mice, although a numerically lower abortion rate (22·2 v. 44·4 %) was observed compared with the control. Dietary supplementation with proline significantly increased serum C-reactive protein levels (P= 0·03) in PCV2-infected pregnant mice, and increased serum TNF-α levels (P= 0·01), leucocytes (P< 0·05), lymphocytes (P< 0·05) and neutrophilic granulocytes (P< 0·05) in PCV2-infected non-pregnant mice. Meanwhile, dietary proline significantly (P< 0·05) decreased the PCV2 virus load in the lung. Furthermore, mice in the dietary proline group showed a significant (P< 0·01) decrease in microscopic lesion scores in the lung, liver and spleen compared with those in the alanine group. Collectively, dietary proline supplementation confers a functional role in PCV2-infected mice.