Chitosan-adjuvanted Salmonella subunit nanoparticle vaccine for poultry delivered through drinking water and feed.

Poor induction of mucosal immunity in the intestines by current Salmonella vaccines is a challenge to the poultry industry. We prepared and tested an oral deliverable Salmonella subunit vaccine containing immunogenic outer membrane proteins (OMPs) and flagellin (F) protein loaded and F-protein surface coated chitosan nanoparticles (CS NPs) (OMPs-F-CS NPs). The OMPs-F-CS NPs had mean particle size distribution of 514 nm, high positive charge and spherical in shape. In vitro and in vivo studies revealed the F-protein surface coated CS NPs were specifically targeted to chicken immune cells. The OMPs-F-CS NPs treatment of chicken immune cells upregulated TLRs, and Th1 and Th2 cytokines mRNA expression. Oral delivery of OMPs-F-CS NPs in birds enhanced the specific systemic IgY and mucosal IgA antibodies responses as well as reduced the challenge Salmonella load in the intestines. Thus, user friendly oral deliverable chitosan-based Salmonella vaccine for poultry is a viable alternative to current vaccines.

Alginate-coated chitosan microparticles encapsulating an oral plasmid-cured live Salmonella enterica serovar Gallinarum vaccine cause a higher expression of interferon-gamma in chickens compared to the parenteral live vaccine.

Salmonella enterica serovar Gallinarum causes a disease in chickens known as fowl typhoid. Interferon-gamma (IFN-γ) has been shown to be crucial in eliminating salmonellosis infection because of its strong association with T-cell responses. This study was undertaken to compare the expression of IFN-γ in chickens generated by different vaccine formulations. Eighty one-day-old Lohmann layer chicks were divided into four groups of 20 birds each for the experiment. This comprised an unvaccinated negative control group (NEG), a group vaccinated with the live 9R vaccine by the injection route (SC), a group vaccinated with alginate-coated chitosan microparticles encapsulating live plasmid-cured S. Gallinarum strain 9 (PC) by the oral route, and a group vaccinated with a weak attenuated live S. Gallinarum strain 9 encapsulated in alginate-coated chitosan microparticles (VM) given orally. Vaccinations were done at 10 and 14 weeks of age followed by challenge at 16 weeks of age. IgG was measured using ELISA. qRT-PCR was used to compare the mRNA fold expression of IFN-γ in the PC, VM and SC groups using the unvaccinated/unchallenged group as the control. There were significant differences in the IgG levels between each vaccinated group and the unvaccinated group (P < 0.05) after booster vaccination and post-challenge. There was 100% protection of the birds in SC and VM groups, 80% protection in PC group and 0% protection in the NEG group. Using 2-ΔΔCT calculation, IFN-γ was more highly expressed in the PC group than in the SC group or VM group. In conclusion, the IFN-γ was more highly expressed in the PC group (though not significantly higher) compared to the SC and VM groups and this could be attributed to the alginate-coated chitosan microparticles which acted as an adjuvant.

Laser micro-structured Si scaffold-implantable vaccines against Salmonella Typhimurium.

Salmonella Typhi is responsible for typhoid fever in humans. Despite the efforts, the development of long-lasting vaccines has failed and the available vaccines display only moderate activity, being considered as "international traveler's" vaccines. Taking advantage of the previously described implantable vaccine technology consisting on 3D laser-microstructured Si scaffolds loaded with antigen-seeded macrophages, the present study aimed to apply an antigenic stimulus of whole extracts of S. Typhimurium, which is the mouse analogue of the human Salmonella Typhi, and examine its ability to mount specific antibody response. After defining the experimental conditions for specific anti-S. Typhimurium IgG production in vitro, antigen-seeded macrophages loaded onto the 3D Si-scaffolds were implanted to mice, while parallel experiments used conventional Freund-complete-adjuvant vaccination protocols. The results showed that only the implantable vaccine protocol could mount a specific antibody response 14 days after implantation. The cytokine profile showed increase of IL-10 and IFN-γ in the case of implantable and conventional vaccination respectively, 7 days after implantation. Morphological studies on the excised scaffolds 14 days after implantation, showed the development of a well-structured adherent monolayer, establishing multiple contacts with lymphocytes in favor to immune response development. Based on the hypothesis that both stimulatory and suppressive components in the vaccination preparation, could affect the overall activity, peptidoglycan was applied as an antigen to the vaccination protocols. Surprisingly, peptidoglycan was shown to induce a mitogenic rather than specific immunogenic response. In this case, histological analysis of the excised scaffolds showed a restricted layer of adherent cells with cytoplasmic extensions, but hard to distinguish cell contacts with lymphocytes. Finally, the presented results showed a differential behavior of antigen presenting cells in accordance to the antigenic stimulus and consequently the activation state of the cells. Tailoring the micro/sub-micron 3D structures and chemistry of Si scaffolds, could control cell behavior according to the user's needs.

Arginine and manganese supplementation on the immune competence of broilers immune stimulated with vaccine against Salmonella Enteritidis.

This experiment was conducted to evaluate the combined effects of manganese-amino acid complex and arginine supplementation on the immune competence of broilers. On the day of hatch 640 male Cobb 500 broiler chicks assigned to two study groups (immune stimulate and non-stimulated). A 2 × 2 factorial arrangement of treatments was used with two manganese sources (MnSO4 or manganese-amino acid complex - MnAA) and two digestible Arg:Lys ratios (1.12 or 1.20). The treatments are: IM (80 ppm MnSO4); MnAA (40 ppm MnSO4 + 40 ppm MnAA); IM+Arg: 80 ppm MnSO4+ L-Arg (Arg:DigLys 1.20); MnAA+Arg: 40 ppm MnSO4 + 40 ppm MnAA + L-Arg (Arg:Lys 1.20). For treatments 1 and 2, the digestible Arg:Lys ratio was 1.12, considered normal for corn-soybean meal-based diets. Birds in the immune stimulated group received a dose of Salmonella Enteritidis vaccine. For growth performance and lymphoid organ development, no significant results were observed. Non-stimulated birds fed diets with Arg supplementation had higher percentage of mucosal T helper, T helper and T cytotoxic, compared to the normal Arg:Lys ratio (1.12). In the immune stimulated birds, broilers fed exclusive IM diet had a higher amount of T helper, T cytotoxic, activated T cytotoxic, and APC cells compared to broilers fed MnAA. The inorganic Mn diets, resulted in higher humoral antibody level (increased IgM levels) only when associated with supplementation of L-Arg. However, the use of an associated Mn source, could support high levels of IgM in commercial levels of Arg. No differences were observed to macrophage phagocytic activity analyses.

Animal Models for Salmonellosis: Applications in Vaccine Research.

Salmonellosis remains an important cause of human disease worldwide. While there are several licensed vaccines for Salmonella enterica serovar Typhi, these vaccines are generally ineffective against other Salmonella serovars. Vaccines that target paratyphoid and nontyphoidal Salmonella serovars are very much in need. Preclinical evaluation of candidate vaccines is highly dependent on the availability of appropriate scientific tools, particularly animal models. Many different animal models exist for various Salmonella serovars, from whole-animal models to smaller models, such as those recently established in insects. Here, we discuss various mouse, rat, rabbit, calf, primate, and insect models for Salmonella infection, all of which have their place in research. However, choosing the right model is imperative in selecting the best vaccine candidates for further clinical testing. In this minireview, we summarize the various animal models that are used to assess salmonellosis, highlight some of the advantages and disadvantages of each, and discuss their value in vaccine development.

Passive immunity stimulated by vaccination of dry cows with a Salmonella bacterial extract.

BACKGROUND: Diarrhea because of Salmonella infection is a cause of neonatal calf diarrhea. The stimulation of passive immunity in the calf by vaccinating the dam for Salmonella has shown some success in previous studies; however, there are no data on the use of currently licensed vaccines in the United States. OBJECTIVE: To determine whether vaccinating cows at dry-off with a commercially available Salmonella bacterial extract would stimulate Salmonella-specific antibodies in the colostrum of cows at calving and whether these antibodies would be transferred to the calf. ANIMALS: Sixty Holstein cattle and 59 calves from a herd presumed to be naïve to Salmonella. METHODS: Prospective clinical trial. Thirty cows were vaccinated at dry-off with a Salmonella enterica serovar Newport bacterial extract and again 4 weeks later. An additional 30 cows received only saline. Calves fed fresh colostrum from their dam within 4 hours of birth had blood collected 24 hours later. RESULTS: Vaccinated cattle had increased Salmonella Newport antibody titers at calving in blood (P = .01) and colostrum (P = .011). Calves that received colostrum from vaccinated cattle also had significant increase in Salmonella antibodies (1.04 ± 0.03) as compared to calves born to unvaccinated cows (0.30 ± 0.02). CONCLUSIONS AND CLINICAL IMPORTANCE: The results indicate that the use of a commercially available Salmonella vaccine can stimulate antibodies that are passed on to the calf via colostral transfer. Further studies need to be done to determine whether these antibodies will offer protection against Salmonella challenge.

Metabolic engineering of Salmonella vaccine bacteria to boost human Vγ2Vδ2 T cell immunity.

Human Vγ2Vδ2 T cells monitor isoprenoid metabolism by recognizing foreign (E)-4-hydroxy-3-methyl-but-2-enyl pyrophosphate (HMBPP), a metabolite in the 2-C-methyl-D-erythritol-4-phosphate pathway used by most eubacteria and apicomplexan parasites, and self isopentenyl pyrophosphate, a metabolite in the mevalonate pathway used by humans. Whereas microbial infections elicit prolonged expansion of memory Vγ2Vδ2 T cells, immunization with prenyl pyrophosphates or aminobisphosphonates elicit short-term Vγ2Vδ2 expansion with rapid anergy and deletion upon subsequent immunizations. We hypothesized that a live, attenuated bacterial vaccine that overproduces HMBPP would elicit long-lasting Vγ2Vδ2 T cell immunity by mimicking a natural infection. Therefore, we metabolically engineered the avirulent aroA(-) Salmonella enterica serovar Typhimurium SL7207 strain by deleting the gene for LytB (the downstream enzyme from HMBPP) and functionally complementing for this loss with genes encoding mevalonate pathway enzymes. LytB(-) Salmonella SL7207 had high HMBPP levels, infected human cells as efficiently as did the wild-type bacteria, and stimulated large ex vivo expansions of Vγ2Vδ2 T cells from human donors. Importantly, vaccination of a rhesus monkey with live lytB(-) Salmonella SL7207 stimulated a prolonged expansion of Vγ2Vδ2 T cells without significant side effects or anergy induction. These studies provide proof-of-principle that metabolic engineering can be used to derive live bacterial vaccines that boost Vγ2Vδ2 T cell immunity. Similar engineering of metabolic pathways to produce lipid Ags or B vitamin metabolite Ags could be used to derive live bacterial vaccine for other unconventional T cells that recognize nonpeptide Ags.

Dietary supplementation with white button mushrooms augments the protective immune response to Salmonella vaccine in mice.

We previously showed that dietary white button mushrooms (WBMs) enhanced natural killer cell activity and that in vitro WBM supplementation promotes maturation and function of dendritic cells (DCs). The current study investigated whether WBM consumption would enhance pathogen-specific immune response using a Salmonella vaccination and infection animal model. C57BL/6 mice were fed diets containing 0%, 2%, or 5% WBM for 4 wk before oral vaccination with live attenuated Salmonella typhimurium SL1479. Four weeks after immunization, mice were orally infected with virulent Salmonella typhimurium SL1344. Immunization increased animal survival and, among immunized mice, the 2% WBM group had a higher survival rate than the other groups. Next, we fed mice 2% WBMs to determine the immunological mechanism underlying the WBM-potentiated protective effect. We found that WBM supplementation increased Salmonella-specific blood immunoglobulin (Ig) G and fecal IgA concentrations. WBM-fed mice also had a higher IgG2a and unchanged IgG1 production, leading to an elevated IgG2a:IgG1 ratio and indicating an enhanced T helper 1 response. Consistent with these results, WBM-fed mice had higher interferon-γ, tumor necrosis factor (TNF)-α, and interleukin (IL)-17A production and unchanged IL-4 production in their splenocytes after polyclonal (anti-CD3/CD28) or antigen-specific stimulation. Furthermore, WBM-fed mice had more DCs in the spleen, and these DCs expressed higher levels of activation markers CD40 and major histocompatibility complex-II. These mice also produced more IL-12 and TNF-α postimmunization. Together, these results suggest that WBMs may improve Salmonella vaccine efficacy through an enhanced adaptive immune response.

Polyphasic characterization of Salmonella Enteritidis isolates on persistently contaminated layer farms during the implementation of a national control program with obligatory vaccination: a longitudinal study.

Since 2007, a national Salmonella control program including obligatory vaccination has been ongoing in Belgium. In this context, the aim of the present study was to investigate the diversity of Salmonella enterica serovar Enteritidis isolates on 5 persistently contaminated Belgian layer farms and to examine the potential sources and transmission routes of Salmonella Enteritidis contamination on the farms during successive laying rounds. A collection of 346 Salmonella isolates originating from the sampled farms were characterized using a combination of multilocus variable number of tandem repeat analysis (MLVA) and phage typing (PT). On each farm, one or 2 dominant MLVA-PT types were found during successive laying cycles. The dominant MLVA type was different for each of the individual farms, but some farms shared the same dominant phage type. Isolates recovered from hens' feces and ceca, egg contents, eggshells, vermin (mice, rats, red mites, and flies), and pets (dog and cat feces) had the same MLVA-PT type also found in the inside henhouse environment of the respective layer farm. Persistent types were identified in the layer farm inside environment (henhouse and egg collecting area). Furthermore, this study demonstrated cross-contamination of Salmonella between henhouses and between the henhouse and the egg collecting area. Additional isolates with a different MLVA-PT type were also recovered, mainly from the egg collecting area. A potential risk for cross-contamination of Salmonella between the individual layer farms and their egg trader was identified.

A novel adjuvant, mixture of alum and the beta-adrenergic receptor antagonist propranolol, elicits both humoral and cellular immune responses for heat-killed Salmonella typhimurium vaccine.

OBJECTIVE: To determine the efficacy of the mixture of propranolol (PRP), a beta-adrenergic receptor antagonist, and alum, as a new adjuvant, in the induction of humoral and cellular immunity in response to heat-killed Salmonella typhimurium (S. typhimurium) (HKST) as a model vaccine. METHODS: BALB/c mice were divided into five groups. Mice in the experimental groups received either the HKST vaccine alone or in combination with the adjuvant alum, PRP or the alum-PRP mixture. Mice in the negative control group received phosphate-buffered saline. All mice were immunized two times on days 0 and 14. Two weeks after the last immunization, immune responses to S. typhimurium were assessed. RESULTS: Administration of the alum-PRP mixture as an adjuvant increased the ability of the HKST vaccine to enhance lymphocyte proliferation, shifted the immune response towards a T-helper (Th) 1 pattern and increased S. typhimurium specific IgG, IgG2a and IgG1. This resulted in improved protective immunity against S. typhimurium. CONCLUSION: Administration of the alum-PRP mixture as an adjuvant in combination with the HKST vaccine, can enhance both humoral and cellular immunity and shift the immune responses to a Th1 pattern.

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.

Persistent Salmonella Enteritidis environmental contamination on layer farms in the context of an implemented national control program with obligatory vaccination.

The aim of this study was to closely examine the Salmonella enterica serovar Enteritidis environmental contamination on persistently positive layer farms in Belgium during successive laying cycles. All of the farms were required to vaccinate their layers under the national control program for Salmonella. Seven farms with previous or current Salmonella Enteritidis contamination were monitored during different stages of the laying period and after cleaning and disinfection (CD). Environmental samples, including from the equipment and vermin, were taken in the henhouse and egg-collecting area. Dilutions were performed to define the degree of Salmonella Enteritidis contamination. Eggshells, egg contents, and ceca were also tested for Salmonella. At the end of the first sampled laying period, 41.6% of the environmental samples were contaminated with Salmonella Enteritidis. After CD, the prevalence dropped to 11.4%. On average, the prevalence in the second laying period increased again: 17.8, 18.4, and 22.3% at the onset, middle, and end of the lay period, respectively. After CD before the third laying period, the prevalence decreased to 6.6% and stabilized at the onset of lay (6.3%). During lay, as well as after CD, a wide variety of contaminated environmental samples were found; for example, in the henhouse, in the egg-collecting area, on mobile equipment and in or on vermin. In the henhouse during laying, the most recurrent and highly contaminated sites were the overshoes, floor, manure belt, and hen feces. The egg-collecting area had a significantly higher number of contaminated samples compared with that of the henhouse. For both sites, the floor appeared to be the most suitable sampling site to estimate the Salmonella Enteritidis status of the farms. Eggshell and egg content contamination varied between 0.18 and 1.8% and between 0.04 and 0.4%, respectively. In total, 2.2% of the analyzed ceca contained Salmonella Enteritidis. This study revealed that Salmonella Enteritidis is present in the environment of persistently Salmonella Enteritidis-contaminated layer farms, demonstrated that in many cases Salmonella Enteritidis contamination was not eliminated after CD, and identified the egg-collecting area as a critical point on most farms.

Feeding a diet containing a fructooligosaccharide mix can enhance Salmonella vaccine efficacy in mice.

Fructooligosaccharides (FOS) are considered prebiotics because of their ability to promote growth of specific beneficial gut bacteria, such as bifidobacteria. Some studies reported potential immune-modulating properties. The aim of this study was to investigate the effect of FOS:inulin mix on murine response to Salmonella vaccine and evaluate the relevance toward protection against Salmonella infection. Balb/c mice were fed a diet containing 5% FOS:inulin mix or a control diet 1 wk before oral immunization with a suboptimal dose of live attenuated Salmonella typhimurium vaccine. Four weeks after vaccination, mice were infected with LD100 of virulent S. typhimurium. Specific blood Salmonella immunoglobulin G and fecal immunoglobulin A significantly increased in mice fed the diet containing prebiotics compared with control mice 4 wk postimmunization. Peritoneal macrophage phagocytic activity also significantly increased in FOS:inulin-fed mice at 1 wk postimmunization compared with control mice. No detectable effects were observed on the percentage of lymphoid cell subsets in the spleen. However, production of cytokines, interferon-gamma, interleukin-12, and tumor necrosis factor alpha, was numerically increased in spleen cell cultures stimulated with mitogens from FOS:inulin-fed mice 1 and 4 wk postimmunization. Salmonella translocation to lymphoid organs was not affected by feeding FOS:inulin. However, the improved response to Salmonella vaccine was concomitant with an increase in the survival rate of FOS:inulin-fed mice upon challenge with virulent Salmonella. No detectable effects were observed on the composition or the metabolic activity of the microbiota. Overall, the data suggest that a diet supplemented with FOS:inulin mix stimulates mucosal immunity and seems to improve efficacy of an oral vaccine.

Partially assembled K99 fimbriae are required for protection.

Antibodies to K99 fimbriae afford protection to F5+ bovine enterotoxigenic Escherichia coli (ETEC). Previous studies show that murine dams immunized with Salmonella vaccine vectors stably expressing K99 fimbriae confer protection to ETEC-challenged neonatal pups. To begin to address adaptation of the K99 scaffold to display heterologous B- and T-cell epitopes, studies were conducted to determine how much of the assembled K99 fimbria is required to maintain protective immunity. Sequential deletions in the K99 gene clusters were made, resulting in diminished localization of the K99 fimbrial subunit in the outer membrane. As placement of the K99 fimbrial subunit became progressively contained within the vaccine vector, diminished immunoglobulin A (IgA) and IgG1 antibody titers, as well as diminished Th2-type cytokine responses, were observed in orally immunized mice. Deletion of fanGH, which greatly reduced the export of the fimbrial subunit to the outer membrane, showed only partial reduction in protective immunity. By contrast, deletion of fanDEFGH, which also reduced the export of the fimbrial subunit to the outer membrane but retained more subunit in the cytoplasm, resulted in protective immunity being dramatically reduced. Thus, these studies showed that retention of K99 fimbrial subunit as native fimbriae or with the deletion of fanGH is sufficient to confer protection.

Salmonella typhimurium grown in iron-rich media, inactivated with ferric chloride and adjuvanted with homologous bacterial DNA is potent and efficacious vaccine in mice.

The present study describes our attempt to construct a novel vaccine formulation that affords full protection against murine typhoid under experimental conditions. Ferric chloride, 100mM, as inactivating agent, bacterial growth under iron-rich conditions and homologous bacterial DNA as adjuvant were used for construction of the experimental Salmonella typhimurium vaccine. The vaccine inoculated twice at 2 weeks interval in Swiss albino mice elicited statistically significant IgG levels when compared with non-adjuvanted and other control groups. All the mice inoculated with the novel vaccine withstood challenge with 50 LD(50) dose of S. typhimurium strain St 585. No significant safety problems were found in mice.

A laboratory study of an inactivated bivalent iron restricted Salmonella enterica serovars Enteritidis and Typhimurium dual vaccine against Typhimurium challenge in chickens.

A commercial inactivated iron restricted Salmonella Typhimurium and Salmonella Enteritidis vaccine was used to vaccinate chicks at 1 day and again at 4 weeks of age, with challenge by a high and a low dose of S. Typhimurium given either orally or by contact with seeder birds inoculated orally with a high dose of S. Typhimurium. In all three challenge regimes, the shedding of challenge strain was reduced significantly (p < 0.05) in vaccinated birds compared with unvaccinated controls. Vaccination reduced colonisation of internal organs after challenge by contact seeder birds. However, no effect of vaccination upon colonisation of internal organs after either high or low oral challenge was apparent. In conclusion, the data indicate that the vaccine should be a useful tool in the control of S. Typhimurium infection in chickens.

Modulation of human humoral immune response through orally administered bovine colostrum.

Eighteen healthy volunteers were randomized into two treatment groups and consumed liquid prepackaged bovine colostrum whey and placebo for 7 days. On days 1, 3 and 5, an attenuated Salmonella typhi Ty21a oral vaccine was given to all subjects to mimic an enteropathogenic infection. The circulating antibody secreting cells and the expression of phagocytosis receptors of the subjects before and after oral immunization were measured with the ELISPOT assay and flow cytometry. All subjects responded well to the vaccine. No significant differences were observed in ELISPOT values for IgA, IgG, IgM, Fcgamma and CR receptor expression on neutrophils and monocytes between the two groups. There was a trend towards greater increase in specific IgA among the subjects receiving their vaccine with bovine colostrum. These results suggest that bovine colostrum may possess some potential to enhance human special immune responses.

Immunopotentiation of a developed Salmonella enterica serotype enteritidis vaccine by thymulin and zinc in meat chicken breeders.

The humoral immunity, spleen and thymus weight indices, lymphocyte count in the thymus cortex, and granuloma diameter at vaccination sites were assessed in four differently immunopotentiated groups of meat chicken breeders. Breeders in the first two groups were given a killed Salmonella enterica serotype Enteritidis (SE) vaccine subcutaneously at 15 and 19 weeks of age. Breeders in the third and fourth groups were left unvaccinated. Breeders in the first group were further immunopotentiated with zinc and thymulin. Each bird in the first group was given the immunopotentiators intraperitoneally in a volume of 0.1 ml at intervals of 3 days for a period of 3 weeks, starting at 15 weeks of age. At each time, each bird in the first group received thymulin (10 ng) and ZnCl2 (1 micromol/L), using a carboxymethyl cellulose carrier, totalling 90 ng thymulin and 9 micromol of ZnCl2 per bird. Each bird in the first three groups was challenged orally with 6.7 x 10(6) cfu/ml of highly virulent SE organisms, at an age of 22 weeks. The first group, which had received zinc and thymulin, had the earliest and highest humoral immune response to SE (p<0.05). This was observed at 2 and 4 weeks after the first vaccination. In addition, the first group had the highest mean thymus weight index, and the highest mean lymphocyte count in the thymus cortex. No significant difference was observed between the first two vaccinated groups in the mean granuloma diameter developed at the two vaccination sites 48 h after administration of the vaccine (p>0.05).

Evaluation of an autogenous Salmonella bacterin and a modified live Salmonella serotype Choleraesuis vaccine on a commercial dairy farm.

OBJECTIVE: To compare the efficacy of a Salmonella bacterin and a modified live Salmonella ser. Choleraesuis vaccine on a commercial dairy. ANIMALS: 450 cows in late gestation and 80 calves. PROCEDURE: Group-1 cows (n = 150) were vaccinated once with a modified live S. Choleraesuis (serogroup C1) strain 54 (SC54) vaccine, group-2 cows (150) were vaccinated on enrollment and 30 days later with a Salmonella ser. Montevideo (serogroup C1) bacterin, and group-3 cows (150) served as unvaccinated controls. One gallon of colostrum harvested from the first 80 cows to calve was fed to each calf. Outcome assessments included fecal shedding of Salmonella spp for the first 10 days after parturition (cows) or birth (calves), milk production, involuntary culling rate, mastitis incidence, antimicrobial use, and mortality rate. RESULTS: Salmonellae were isolated from 306 of 309 (99%) cows and 64 of 74 (86.5%) calves. Shedding frequency was less in SC54-vaccinated cows and calves that received colostrum from those cows, compared with the other groups, and vaccination was specifically associated with less shedding of serogroup C1 salmonellae. Production data were similar among groups. CONCLUSIONS AND CLINICAL RELEVANCE: Vaccination of pregnant cows with an autogenous Salmonella bacterin had no effect on fecal shedding of salmonellae, whereas vaccination with a modified live S. Choleraesuis vaccine reduced the frequency of fecal shedding of serogroup C1 salmonellae during the peripartum period. A commercial S. Choleraesuis vaccine licensed for use in swine may be more efficacious than autogenous Salmonella bacterins on dairies infected with serogroup C1 salmonellae.

Safety and immune responses to attenuated Salmonella enterica serovar typhi oral live vector vaccines expressing tetanus toxin fragment C.

Attenuated Salmonella enterica serovar Typhi vaccine strain CVD 908-htrA was used as a vector to deliver fragment C of tetanus toxin as a single-dose oral tetanus vaccine candidate to elicit protective levels of serum tetanus antitoxin. Twenty-one healthy adult volunteers received doses of 1.6 x 10(7) to 8.2 x 10(9) CFU of one of two strains, CVD 908-htrA(pTETnir15) or CVD 908-htrA(pTETlpp), which contained plasmid-encoded fragment C, with sodium bicarbonate, and the safety and immune responses to serovar Typhi antigens and tetanus toxin were assessed. No volunteer had fever or positive blood cultures after vaccination, although diarrhea occurred in 3 volunteers and vomiting in 2 volunteers within 3 weeks after vaccination. Most volunteers excreted the vaccine strain in the first 72 h after vaccination. Three of nine volunteers who received 10(8) CFU or higher doses of the CVD 908-htrA(pTETlpp) construct developed rises in serum antitoxin antibodies. The serum and cellular immune responses to serovar Typhi antigens were less frequent than those previously observed in volunteers who ingested the parent strain CVD 908-htrA. This study demonstrates that fragment C of tetanus toxin delivered orally to volunteers in an S. Typhi vector can elicit protective levels of serum antitoxin.