Comparative immunogenicity and efficacy of equivalent outer membrane vesicle and glycoconjugate vaccines against nontyphoidal Salmonella.

Nontyphoidal Salmonellae cause a devastating burden of invasive disease in sub-Saharan Africa with high levels of antimicrobial resistance. Vaccination has potential for a major global health impact, but no licensed vaccine is available. The lack of commercial incentive makes simple, affordable technologies the preferred route for vaccine development. Here we compare equivalent Generalized Modules for Membrane Antigens (GMMA) outer membrane vesicles and O-antigen-CRM197 glycoconjugates to deliver lipopolysaccharide O-antigen in bivalent Salmonella Typhimurium and Enteritidis vaccines. Salmonella strains were chosen and tolR deleted to induce GMMA production. O-antigens were extracted from wild-type bacteria and conjugated to CRM197 Purified GMMA and glycoconjugates were characterized and tested in mice for immunogenicity and ability to reduce Salmonella infection. GMMA and glycoconjugate O-antigen had similar structural characteristics, O-acetylation, and glucosylation levels. Immunization with GMMA induced higher anti-O-antigen IgG than glycoconjugate administered without Alhydrogel adjuvant. With Alhydrogel, antibody levels were similar. GMMA induced a diverse antibody isotype profile with greater serum bactericidal activity than glycoconjugate, which induced almost exclusively IgG1. Immunization reduced bacterial colonization of mice subsequently infected with SalmonellaS Typhimurium numbers were lower in tissues of mice vaccinated with GMMA compared with glycoconjugate. S. Enteritidis burden in the tissues was similar in mice immunized with either vaccine. With favorable immunogenicity, low cost, and ability to induce functional antibodies and reduce bacterial burden, GMMA offer a promising strategy for the development of a nontyphoidal Salmonella vaccine compared with established glycoconjugates. GMMA technology is potentially attractive for development of vaccines against other bacteria of global health significance.

Development and Evaluation of Two Live Salmonella-Vectored Vaccines for Campylobacter Control in Broiler Chickens.

Campylobacter is the leading bacterial cause of human enteritis in developed countries. Human campylobacteriosis is commonly associated with the consumption of undercooked, contaminated chicken, a natural host of Campylobacter. Thus, the control of Campylobacter colonization in poultry at the farm level would reduce the risk of human exposure to this pathogen. Vaccination is an attractive intervention measure to mitigate Campylobacter in poultry. Our recent studies have demonstrated that the outer-membrane proteins CmeC (an essential component of CmeABC multidrug efflux pump) and CfrA (ferric enterobactin receptor) are feasible candidates for immune intervention against Campylobacter. By targeting these two promising vaccine candidates, live attenuated Salmonella-vectored vaccines were developed and evaluated in this study. Briefly, the cfrA and cmeC genes were cloned into expression vector pYA3493 and transferred into Salmonella enterica serovar Typhimurium χ8914, the USDA licensed live attenuated vaccine strain. The oral live Salmonella vaccines producing CfrA or CmeC (truncated or full length) were successfully constructed by using delicate molecular manipulation despite the challenge due to the potential toxic effect of the cloned gene product in the Escherichia coli host. Expression and membrane localization of the target protein in the vaccines were confirmed by immunoblotting. The efficacies of the two live vaccines that produce full-length CfrA or CmeC were evaluated by using broiler chickens. However, oral vaccination of chickens failed to trigger significant systemic and intestinal mucosal immune responses and, consequently, did not confer protection against Campylobacter jejuni colonization chickens. The vaccination regimens of the constructed live Salmonella-vectored vaccine need to be optimized in future studies.

Immunization with recombinant Salmonella expressing SspH2-EscI protects mice against wild type Salmonella infection.

BACKGROUND: Enhancing caspase-1 activation in macrophages is helpful for the clearance of intracellular bacteria in mice. Our previous studies have shown that EscI, an inner rod protein of type III system in E. coli can enhance caspase-1 activation. The purpose of this study was to further analyze the prospect of EscI in the vaccine design. RESULTS: A recombinant Salmonella expressing SspH2-EscI fusion protein using the promotor of Salmonella effector SspH2, X4550(pYA3334-P-SspH2-EscI), was constructed. A control recombinant Salmonella expressing SspH2 only X4550(pYA3334-P-SspH2) was also constructed. In the early stage of in vitro infection of mouse peritoneal macrophages, X4550(pYA3334-P-SspH2-EscI) could significantly (P < 0.05) enhance intracellular caspase-1 activation and pyroptotic cell death of macrophages, when compared with X4550(pYA3334-P-SspH2). Except for the intracellular pH value, the levels of reactive oxygen species, intracellular concentration of calcium ions, nitric oxide and mitochondrial membrane potential in macrophages were not significantly different between the cells infected with X4550(pYA3334-P-SspH2-EscI) and those infected with X4550(pYA3334-P-SspH2). Besides, only lower inflammatory cytokines secretion was induced by X4550(pYA3334-P-SspH2-EscI) than X4550(pYA3334-P-SspH2). After intravenous immunization of mice (1 × 106 cfu/mouse), the colonization of X4550(pYA3334-P-SspH2-EscI) in mice was significantly limited at one week post immunization (wpi), when compared with X4550(pYA3334-P-SspH2) (P < 0.05). The population of activated CD8+T lymphocytes in mouse spleens induced by X4550(pYA3334-P-SspH2-EscI) was lower than that induced by X4550(pYA3334-P-SspH2) at 2-3 wpi, and the ratio of CD4+T cells to CD8+T cells decreased. The blood coagulation assay indicated that no significant difference was found between X4550(pYA3334-P-SspH2-EscI) and uninfected control, while X4550(pYA3334-P-SspH2) could induce the quick coagulation. Notably, immunization of X4550(pYA3334-P-SspH2-EscI) could limit the colonization of challenged Salmonella strains in the early stage of infection and provide more effective protection. CONCLUSION: The activation of caspase-1 in macrophages by EscI can be used in the design of live attenuated Salmonella vaccine candidate.

Overexpression of MicA induces production of OmpC-enriched outer membrane vesicles that protect against Salmonella challenge.

Outer membrane vesicles (OMVs) derived from bacteria are promising candidates for subunit vaccines. Stresses that modulate the composition of outer membrane proteins (OMPs) are important for OMV synthesis. Small RNAs (sRNAs) expressed in response to stress regulate OMPs, although the mechanism underlying sRNA-mediated OMV biogenesis and its utility for developing vaccine platforms remains to be elucidated. Here, we characterized the role of a sRNA, MicA, which regulates OmpA, a major OMP involved in both production of OMVs and reactive immunity against Salmonella challenge. A Salmonella strain overexpressing MicA generated more OMVs than a control strain. In addition, OmpC was the major component of MicA-derived OMV proteins. MicA-derived OMVs induced Th1- and Th17-type immune responses in vitro and reduced Salmonella-mediated lethality in a mouse model. Thus, OmpA-regulatory sRNA-derived OMVs may facilitate production of Salmonella-protective vaccines.

Current perspectives on invasive nontyphoidal Salmonella disease.

PURPOSE OF REVIEW: We searched PubMed for scientific literature published in the past 2 years for relevant information regarding the burden of invasive nontyphoidal Salmonella disease and host factors associated with nontyphoidal Salmonella infection and discuss current knowledge on vaccine development. The following search terms were used: Salmonella, non typhoidal/nontyphoidal, NTS, disease, bloodstream infection, invasive, sepsis/septicaemia/septicemia, bacteraemia/bacteremia, gastroenteritis, incidence, prevalence, morbidity, mortality, case fatality, host/risk factor, vaccination, and prevention/control. RECENT FINDINGS: Estimates of the global invasive nontyphoidal Salmonella disease burden have been recently updated; additional data from Africa, Asia, and Latin America are now available. New data bridge various knowledge gaps, particularly with respect to host risk factors and the geographical distribution of iNTS serovars. It has also been observed that Salmonella Typhimurium sequence type 313 is emergent in several African countries. Available data suggest that genetic variation in the sequence type 313 strain has led to increased pathogenicity and human host adaptation. A bivalent efficacious vaccine, targeting Salmonella serovars Typhimurium and Enteritidis, would significantly lower the disease burden in high-risk populations. SUMMARY: The mobilization of surveillance networks, especially in Asia and Latin America, may provide missing data regarding the invasive nontyphoidal Salmonella disease burden and their corresponding antimicrobial susceptibility profiles. Efforts and resources should be directed toward invasive nontyphoidal Salmonella disease vaccine development.

Immunogenic potential of a Salmonella Typhimurium live vaccine for pigs against monophasic Salmonella Typhimurium DT 193.

BACKGROUND: Monophasic Salmonella Typhimurium (mSTM) strains account for up to 8.6% of all human Salmonellosis cases. They have an increasing prevalence during recent years and several human cases with hospitalisation were reported. These strains are often isolated from pigs and pork - one primary source of human infection. A Salmonella Typhimurium (STM) live vaccine has been proven successful in controlling of STM infections in pigs for many years. The aim of this study was to test the immunogenicity of the vaccine in weaners during oral challenge with a virulent mSTM strain and to examine the kinetics of STM-specific IgA, IgM and IgG antibodies induced by vaccination and infection. RESULTS: Despite clinical signs being present in both groups, the vaccination led to a significant reduction of diarrhoea, overall clinical symptoms and a milder elevation of the body temperature. Necropsy revealed fewer pathological lesions in the gastrointestinal tract of vaccinated compared to control animals. Moreover, in the ileal and caecal mucosa and in the ileocaecal lymph nodes the challenge strain burden was significantly reduced by vaccination. Significant differences in the antibody responses of both groups were present during the vaccination period and after infection. In vaccinated animals Salmonella-specific IgA and IgG antibody levels increased significantly after vaccination and were even more pronounced in response to challenge. In contrast, similarly low levels of IgM antibodies were detected during the vaccination period in both vaccinated and non-vaccinated animals. However, after challenge IgM antibody levels increased significantly in control pigs while neither IgA nor IgG antibodies were detectable. CONCLUSION: The data demonstrate that mSTM can evoke clinical signs in weaners. Due to the vaccination their incidence and magnitude were significantly milder. Vaccination also led to a significantly reduced challenge strain burden in the intestine and the lymph nodes which is comparable to previous studies using the same vaccine in a challenge with biphasic STM. Therefore, it is concluded that this vaccine induces immunity against monophasic and biphasic STM strains. Furthermore, the results of antibody profiles in response to vaccination and infection provide additional evidence for humoral immune mechanisms triggered during Salmonella infection or vaccination.

Prevention of egg contamination by Salmonella Enteritidis after oral vaccination of laying hens with Salmonella Enteritidis ΔtolC and ΔacrABacrEFmdtABC mutants.

Vaccination of laying hens has been successfully used to reduce egg contamination by Salmonella Enteritidis, decreasing human salmonellosis cases worldwide. Currently used vaccines for layers are either inactivated vaccines or live attenuated strains produced by mutagenesis. Targeted gene deletion mutants hold promise for future vaccines, because specific bacterial functions can be removed that may improve safety and allow differentiation from field strains. In this study, the efficacy of Salmonella Enteritidis ΔtolC and ΔacrABacrEFmdtABC strains in laying hens as live vaccines was evaluated. The mutants are deficient in either the membrane channel TolC (ΔtolC) or the multi-drug efflux systems acrAB, acrEF and mdtABC (ΔacrABacrEFmdtABC). These strains have a decreased ability for gut and tissue colonization and are unable to survive in egg white, the latter preventing transmission of the vaccine strains to humans. Two groups of 30 laying hens were orally inoculated at day 1, 6 weeks and 16 weeks of age with 10(8) cfu of either vaccine strain, while a third group was left unvaccinated. At 24 weeks of age, the birds were intravenously challenged with 5 × 10(7) cfu Salmonella Enteritidis PT4 S1400/94. The vaccine strains were not shed or detected in the gut, internal organs or eggs, 2 weeks after the third vaccination. The strains significantly protected against gut and internal organ colonization, and completely prevented egg contamination by Salmonella Enteritidis under the conditions of this study. This indicates that Salmonella Enteritidis ΔtolC and ΔacrABacrEFmdtABC strains might be valuable strains for vaccination of layers against Salmonella Enteritidis.

A live attenuated Salmonella Enteritidis secreting detoxified heat labile toxin enhances mucosal immunity and confers protection against wild-type challenge in chickens.

A live attenuated Salmonella Enteritidis (SE) capable of constitutively secreting detoxified double mutant Escherichia coli heat labile toxin (dmLT) was developed. The biologically adjuvanted strain was generated via transformation of a highly immunogenic SE JOL1087 with a plasmid encoding dmLT gene cassette; the resultant strain was designated JOL1641. A balanced-lethal host-vector system stably maintained the plasmid via auxotrophic host complementation with a plasmid encoded aspartate semialdehyde dehydrogenase (asd) gene. Characterization by western blot assay revealed the dmLT subunit proteins in culture supernatants of JOL1641. For the investigation of adjuvanticity and protective efficacy, chickens were immunized via oral or intramuscular routes with PBS, JOL1087 and JOL1641. Birds immunized with JOL1641 showed significant (P ≤ 0.05) increases in intestinal SIgA production at the 1(st) and 2(nd) weeks post-immunization via oral and intramuscular routes, respectively. Interestingly, while both strains showed significant splenic protection via intramuscular immunization, JOL1641 outperformed JOL1087 upon oral immunization. Oral immunization of birds with JOL1641 significantly reduced splenic bacterial counts. The reduction in bacterial counts may be correlated with an adjuvant effect of dmLT that increases SIgA secretion in the intestines of immunized birds. The inclusion of detoxified dmLT in the strain did not cause adverse reactions to birds, nor did it extend the period of bacterial fecal shedding. In conclusion, we report here that dmLT could be biologically incorporated in the secretion system of a live attenuated Salmonella-based vaccine, and that this construction is safe and could enhance mucosal immunity, and protect immunized birds against wild-type challenge.

Immune protection of chickens conferred by a vaccine consisting of attenuated strains of Salmonella Enteritidis, Typhimurium and Infantis.

The colonization of poultry with different Salmonella enterica serovars poses an issue throughout the world. In this study we therefore tested the efficacy of a vaccine consisting of attenuated strains of Salmonella enterica serovars Enteritidis, Typhimurium and Infantis against challenge with the same serovars and with S. Agona, Dublin and Hadar. We tested oral and aerosol administration of the vaccine, with or without co-administration of cecal microbiota from adult hens. The protective effect was determined by bacterial counts of the challenge strains up to week 18 of life and by characterizing the immune response using real-time PCR specific for 16 different genes. We have shown that a vaccine consisting of attenuated S. Enteritidis, S. Typhimurium and S. Infantis protected chickens against challenge with the wild type strains of the same serovars and partially protected chickens also against challenge with isolates belonging to serovars Dublin or Hadar. Aerosol vaccination was more effective at inducing systemic immunity whilst oral vaccination stimulated a local immune response in the gut. Co-administration of cecal microbiota increased the protectiveness in the intestinal tract but slightly decreased the systemic immune response. Adjusting the vaccine composition and changing the administration route therefore affects vaccine efficacy.

Challenges in mucosal vaccines for the control of infectious diseases.

The mucosal surface is the largest route through which pathogens enter the human body. To control the outbreak of mucosal infectious diseases, we must use our knowledge of the mucosal immune system to create vaccines that elicit protective mucosal and systemic immunity. Mucosal vaccines have advantages over traditional injectable vaccines in that they not only induce effective mucosal immune responses, but they also do not cause physical or psychological discomfort. Mucosal vaccines currently licensed for human use include oral vaccines against Vibrio cholerae, Salmonella typhi, poliovirus and rotavirus, and nasal vaccines against influenza virus. To further improve the existing vaccines, it will be necessary to develop novel vaccine production, storage and delivery systems through innovative strategies derived from interdisciplinary scientific research. Our accumulated knowledge of the innate and acquired arms of the mucosal immune system and the recent scientific and technical advancements in the fields of molecular biology, plant biology, bio-engineering and chemical engineering, genome biology and systems biology have created a unique research and development platform for the development of the next generation of mucosal vaccines. This review summarizes the current perspectives and future directions of mucosal vaccine development with emphasis on oral and nasal vaccines for the control of infectious diseases.

Protection Against Necrotic Enteritis in Broiler Chickens by Regulated Delayed Lysis Salmonella Vaccines.

Necrotic enteritis (NE), caused by Gram-positive Clostridium perfringens type A strains, has gained more attention in the broiler industry due to governmental restrictions affecting the use of growth-promoting antibiotics in feed. To date, there is only one commercial NE vaccine available, based on the C. perfringens alpha toxin. However, recent work has suggested that the NetB toxin, not alpha toxin, is the most critical virulence factor for causing NE. These findings notwithstanding, it is clear from prior research that immune responses against both toxins can provide some protection against NE. In this study, we delivered a carboxyl-terminal fragment of alpha toxin and a GST-NetB fusion protein using a novel attenuated Salmonella vaccine strain designed to lyse after 6-10 rounds of replication in the chicken host. We immunized birds with vaccine strains producing each protein individually, a mixture of the two strains, or with a single vaccine strain that produced both proteins. Immunization with strains producing either of the single proteins was not protective, but immunization with a mixture of the two or with a single strain producing both proteins resulted in protective immunity. The vaccine strain synthesizing both PlcC and GST-NetB was able to elicit strong production of intestinal IgA, IgY, and IgM antibodies and significantly protect broilers against C. perfringens challenge against both mild and severe challenges. Although not part of our experimental plan, the broiler chicks we obtained for these studies were apparently contaminated during transit from the hatchery with group D Salmonella. Despite this drawback, the vaccines worked well, indicating applicability to real-world conditions.

Administration of a Salmonella Enteritidis ΔhilAssrAfliG strain by coarse spray to newly hatched broilers reduces colonization and shedding of a Salmonella Enteritidis challenge strain.

Consumption of contaminated poultry meat is still an important cause of Salmonella infections in humans. Colonization inhibition (CI) occurs when a live Salmonella strain is administered to chickens and subsequently protects against challenge with another Salmonella strain belonging to the same serotype. A Salmonella Enteritidis hilAssrAfliG deletion mutant has previously been proven to reduce colonization and shedding of a wild-type Salmonella Enteritidis strain in newly hatched broilers after experimental infection. In this study, we compared two administration routes for this strain. Administering the Salmonella Enteritidis ΔhilAssrAfliG strain through drinking water on the first day of life resulted in decreased fecal shedding and cecal colonization of a wild-type Salmonella Enteritidis challenge strain administered 24 h later using a seeder-bird model. When administering the CI strain by coarse spray on newly hatched broiler chicks, an even more pronounced reduction of cecal colonization was observed, and fecal shedding of the Salmonella Enteritidis challenge strain ceased during the course of the experiment. These data suggest that administering a Salmonella Enteritidis ΔhilAssrAfliG strain to newly hatched chicks using a coarse spray is a useful and effective method that reduces colonization and shedding of a wild-type Salmonella Enteritidis strain after early challenge.

Oral administration of the Salmonella Typhimurium vaccine strain Nal2/Rif9/Rtt to laying hens at day of hatch reduces shedding and caecal colonization of Salmonella 4,12:i:-, the monophasic variant of Salmonella Typhimurium.

A new monophasic variant of Salmonella Typhimurium, Salmonella enterica serotype 4,12:i:-, is rapidly emerging. This serotype is now considered to be among the 10 most common serovars isolated from humans in many countries in Europe and in the United States. The public health risk posed by these emerging monophasic Salmonella Typhimurium strains is considered comparable to that of classical Salmonella Typhimurium strains. The serotype 4,12:i:- is frequently isolated from pigs but also poultry are carrying strains from this serotype. In the current study, we evaluated the efficacy of the Salmonella Typhimurium strain Nal2/Rif9/Rtt, a strain contained in the commercially available live vaccines AviPro Salmonella Duo and AviPro Salmonella VacT, against infection with the emerging monophasic variant in poultry. Three independent trials were conducted. In all trials, laying type chicks were orally vaccinated with the Salmonella Typhimurium strain Nal2/Rif9/Rtt at d hatch, while the birds were challenged the next d with a different infection dose in each trial (low, high, and intermediate). For the intermediate-dose study, a seeder bird model was used in which one out of 3 animals were infected while all individual birds were infected in the other trials. Data obtained from each independent trial show that oral administration of the Salmonella Typhimurium strain Nal2/Rif9/Rtt at d hatch reduced shedding, caecal, and internal organ colonization of Salmonella Typhimurium 4,12:i:-, administered at d 2 life. This indicates that Salmonella Typhimurium strain Nal2/Rif9/Rtt can help to control Salmonella 4,12:i:- infections in poultry.

Stochastic modeling of imperfect Salmonella vaccines in an adult dairy herd.

Salmonella is a major cause of bacterial foodborne disease. Human salmonellosis results in significant public health concerns and a considerable economic burden. Dairy cattle are recognized as a key source of several Salmonella serovars that are a threat to human health. To lower the risk of Salmonella infection, reduction of Salmonella prevalence in dairy cattle is important. Vaccination as a control measure has been applied for reduction of preharvest Salmonella prevalence on dairy farms. Salmonella vaccines are usually imperfect (i.e., vaccines may provide a partial protection for susceptible animals, reduce the infectiousness and shedding level, shorten the infectious period of infected animals, and/or curb the number of clinical cases), and evaluation of the potential impacts of imperfect Salmonella vaccines at the farm level is valuable to design effective intervention strategies. The objective of this study was to investigate the impact of imperfect Salmonella vaccines on the stochastic transmission dynamics in an adult dairy herd. To this end, we developed a semi-stochastic and individual-based continuous time Markov chain (CTMC) vaccination model with both direct and indirect transmission, and applied the CTMC vaccination model to Salmonella Cerro transmission in an adult dairy herd. Our results show that vaccines shortening the infectious period are most effective in reducing prevalence, and vaccines decreasing host susceptibility are most effective in reducing the outbreak size. Vaccines with multiple moderate efficacies may have the same effectiveness as vaccines with a single high efficacy in reducing prevalence, time to extinction, and outbreak size. Although the environment component has negligible contributions to the prevalence, time to extinction, and outbreak size for Salmonella Cerro in the herd, the relative importance of environment component was not assessed. This study indicates that an effective vaccination program against Salmonella Cerro spread in the herd can be designed with (1) vaccines with a single high efficacy in reducing either the infectious period or susceptibility of the host, or (2) if such single high efficacy vaccines are not available, vaccines with multiple moderate efficacies may be considered instead. These findings are also of general value for designing vaccination program for Salmonella serotypes in livestock.

Prospects for prevention of Salmonella infection in children through vaccination.

PURPOSE OF REVIEW: Strains of Salmonella enterica subsp. enterica are amongst the most commonly identified invasive bacterial pathogens in resource-poor settings, and cause significant mortality, particularly in children. In this study we review recent progress in the development of vaccines against S. Typhi, S. Paratyphi and nontyphoidal Salmonella for children. RECENT FINDINGS: Typhoid remains common and S. Paratyphi A is increasingly recognized as a cause of enteric fever in Asia. In rural Africa, nontyphoidal salmonellae are among the most common invasive bacterial infections, although S. Typhi predominates in some urban centres. Licensed vaccines against typhoid have moderate but useful efficacy but neither of the two available vaccines can be used in infants. Although Ty21a may afford some cross-protection against S. Paratyphi B, there are no vaccines that specifically target paratyphoid or any nontyphoidal Salmonella. Several live attenuated vaccines are under development and may offer some advantages over Ty21a. Vi-conjugate vaccines should offer children excellent protection from typhoid once licensed. SUMMARY: There are few effective vaccines against Salmonella sp. and those that do exist target only one serovar, S. Typhi. Research is urgently needed to combat emerging agents of enteric fever such as S. Paratyphi A as well as nontyphoidal serovars, which commonly cause invasive disease in Africa.

Effect of a DIVA vaccine with and without in-feed use of coated calcium-butyrate on transmission of Salmonella Typhimurium in pigs.

BACKGROUND: For satisfactory Salmonella control, good biosecurity along the pork production chain is crucial, although additional control measures on-farm need to be considered. This study evaluated the effect of two potential control measures against the spread of Salmonella Typhimurium via a transmission experiment with 56 piglets (3-15 weeks of age): two groups were orally vaccinated with 107 - 108 Colony Forming Units (CFU)/2 mL of a new attenuated Salmonella Typhimurium vaccine 'Salmoporc-∆rfaJ' with DIVA capacities (Differentiation between Infected and Vaccinated Animals) (n = 2x16); the feed of one group was additionally supplemented with coated calcium-butyrate salt. Two weeks post vaccination, four pigs per group were orally challenged with 107 CFU/2 mL of a Salmonella Typhimurium strain 112910a. Both groups were compared with a positive (challenged/untreated; n = 16) and negative (unchallenged/untreated; n = 8) control group. Until six weeks post challenge, blood, individual faecal and finally tissue samples were examined. Adjusted transmission ratios 'Ra' were estimated, based on the challenge strain isolation from faecal and/or tissue samples. RESULTS: In both intervention groups, Ra values were lower compared to the positive control group, although these differences were not significant. In the combination group DIVA vaccine + coated butyrate, less non-challenged contact animals excreted Salmonella and less tissue samples were found Salmonella-positive in all pigs, when compared to the positive control group (P < 0.01). Seroconversion was detected in none of the vaccinated animals before challenge, when using a commercial lipopolysaccharide (LPS) ELISA targeting only Salmonella O-antigens, deleted in this vaccine. This was in contrast with an in-house whole-cell ELISA testing for various Salmonella antigens, in which Salmonella-specific antibodies were found pre-challenge in the serum of the vaccinated pigs. CONCLUSIONS: Both interventions showed a limited, non-significant reduction of Salmonella transmission between piglets. They may have applications towards Salmonella control and surveillance. Firstly, the number of Salmonella excreting contact pigs was significantly lower in the group where vaccination was combined with coated calcium-butyrate salt in the feed; secondly, the new vaccine confirmed its DIVA capacity. Therefore, these interventions merit further research with larger sample sizes, to optimize their use for Salmonella programmes.

[Therapeutic intervention alternatives in cancer, using attenuated live bacterial vectors: Salmonella enterica as a carrier of heterologous molecules]. / Alternativas de intervención terapéutica en cáncer usando vectores bacterianos vivos atenuados: Salmonella enterica como acarreador de moléculas heterólogas.

Salmonella enterica is a facultative anaerobic bacteria, whose ability to colonize antigen-presenting cells (APCs) such as dendritic cells and macrophages, has allowed its successful use as an alive, attenuated bacterial vector for vaccination. Salmonella enterica elicits efficient cellular, humoral and mucosal immune responses, against heterologous antigens including viruses, parasites, other bacterial species and tumor-associated antigens, since it is capable of delivering these antigens to cells of the immune system. The extracellular expression of heterologous antigens on the surface of Salmonella enterica via its type I, III and V secretion systems, and their delivery into infected cells is essential for its stimulation of immune responses against these antigens. Moreover, Salmonella enterica is a promising therapeutic agent against cancer, as demonstrated by reports of pre-clinical and clinical studies indicating that, after systemic administration, Salmonella enterica preferentially localizes in solid tumors and metastases as compared to normal tissues. In this review, we focus on novel prophylactic and therapeutic anti-cancer approaches using Salmonella enterica as a delivery system of heterologous molecules with the aim of inhibiting tumor growth.

Salmonella Vaccine Study in Oxford (SALVO) trial: protocol for an observer-participant blind randomised placebo-controlled trial of the iNTS-GMMA vaccine within a European cohort.

INTRODUCTION: Invasive non-typhoidal Salmonellosis (iNTS) is mainly caused by Salmonella enterica serovars Typhimurium and Enteritidis and is estimated to result in 77 500 deaths per year, disproportionately affecting children under 5 years of age in sub-Saharan Africa. Invasive non-typhoidal Salmonellae serovars are increasingly acquiring resistance to first-line antibiotics, thus an effective vaccine would be a valuable tool in reducing morbidity and mortality from infection. While NTS livestock vaccines are in wide use, no licensed vaccines exist for use in humans. Here, a first-in-human study of a novel vaccine (iNTS-GMMA) containing S. Typhimurium and S. Enteritidis Generalised Modules for Membrane Antigens (GMMA) outer membrane vesicles is presented. METHOD AND ANALYSIS: The Salmonella Vaccine Study in Oxford is a randomised placebo-controlled participant-observer blind phase I study of the iNTS-GMMA vaccine. Healthy adult volunteers will be randomised to receive three intramuscular injections of the iNTS-GMMA vaccine, containing equal quantities of S. Typhimurium and S. Enteritidis GMMA particles adsorbed on Alhydrogel, or an Alhydrogel placebo at 0, 2 and 6 months. Participants will be sequentially enrolled into three groups: group 1, 1:1 randomisation to low dose iNTS-GMMA vaccine or placebo; group 2, 1:1 randomisation to full dose iNTS-GMMA vaccine or placebo; group 3, 2:1 randomisation to full dose or lower dose (dependant on DSMC reviews of groups 1 and 2) iNTS-GMMA vaccine or placebo.The primary objective is safety and tolerability of the vaccine. The secondary objective is immunogenicity as measured by O-antigen based ELISA. Further exploratory objectives will characterise the expanded human immune profile. ETHICS AND DISSEMINATION: Ethical approval for this study has been obtained from the South Central-Oxford A Research Ethics Committee (Ethics REF:22/SC/0059). Appropriate documentation and regulatory approvals have been acquired. Results will be disseminated via peer-reviewed articles and conferences. TRIAL REGISTRATION NUMBER: EudraCT Number: 2020-000510-14.

Dietary arginine supplementation alleviates immune challenge induced by Salmonella enterica serovar Choleraesuis bacterin potentially through the Toll-like receptor 4-myeloid differentiation factor 88 signalling pathway in weaned piglets.

The present study evaluated whether dietary arginine (Arg) supplementation could attenuate immune challenge induced by Salmonella enterica serovar Choleraesuis C500 (S.C500) through the Toll-like receptor (TLR) 4-myeloid differentiation factor 88 (Myd88) signalling pathway in weaned piglets. A total of thirty-six weaned pigs were randomly allocated into six groups with six replicates per group. Pigs were subjected to three dietary treatments (namely two groups per treatment) in the first week (0-7 d) and fed with diets containing 0, 0·5 and 1·0 % l-Arg, respectively. On day 8, pigs were injected intramuscularly either with S.C500 or sterile saline. Serum samples were collected at day 8 (before injection), and at 1, 3 and 10 d post-injection, pigs were killed for evaluation of tissue gene expression following the last blood collection. Piglets fed the diets with 0·5 or 1·0 % Arg supplementation had a higher concentration of serum Arg (P < 0·05). S.C500-challenged piglets had higher (P < 0·05) serum antibody levels during the days 9-18. Weight gain and feed intake were decreased remarkably (P < 0·01) after the injection of S.C500, and 0·5 or 1·0 % Arg supplementation tended to alleviate the inhibition. The S.C500 challenge significantly enhanced (P < 0·05) serum C-reactive protein (CRP), interferon-γ and IL-12 concentrations, but Arg supplementation attenuated (P < 0·05) the increase in CRP level. The mRNA expression of TLR4, TLR5, Myd88, p65 NF-κB and TNF-α was up-regulated (P < 0·05) by the S.C500 challenge in different tissues, but was down-regulated (P < 0·05) by Arg supplementation. In conclusion, Arg supplementation could inhibit the excessive activation of the TLR4-Myd88 signalling pathway and thus attenuated the negative effects caused by the immune challenge of S.C500.