Evaluation of the efficacy of intraperitoneal immunization in reducing Salmonella typhimurium infection in chickens

Influence of Pediococcus pentosaceus GT001 on Performance, Meat Quality, Immune Function, Antioxidant and Cecum Microbial in Broiler Chickens Challenged by Salmonella typhimurium

This study evaluated the effects of Pediococcus pentosaceus GT001 on Salmonella typhimurium (S. typhimurium)-challenged broiler chickens. Two hundred Ross 708 broiler day-old chicks with comparable weight were distributed at random into four treatments with five replicates and ten chicks per replicate. The following were the treatment groups: (B) basal diet (control); (B + S) basal diet and birds were challenged with S. typhimurium at 1.0 × 107 cfu/g; (B + P) basal diet + Pediococcus pentosaceus GT001 at 4.0 × 108 cfu/g; (B + P + S) basal diet + P. pentosaceus GT001 at 4.0 × 108 cfu/g and birds were challenged with S. typhimurium at 1.0 × 107 cfu/g. There was a significant reduction (p < 0.05) in the body weight of the Salmonella-infected birds compared to the other treatment groups. However, the FCRs of the broilers were comparable among the different treatment groups (p > 0.05). The lipid profile and liver function indices measured were significantly enhanced in the P. pentosaceus GT001-supplemented groups (B + P and B + P + S) compared to the group that was Salmonella-challenged (p < 0.05) but were similar to those in the control group. The serum antioxidant activities, such as the T-AOC, SOD, CAT, GHS-Px and MDA, were significantly improved in the P. pentosaceus GT001-supplemented groups (B + P and B + P + S) (p < 0.05). The MDA was similar in the B + P and B + P + S groups, but both were significantly lower than the control and the Salmonella groups. The administration of P. pentosaceus GT001 enhanced the lipase and amylase levels in both the serum and intestine of the broilers (p < 0.05). The immunoglobin (IgA, IgG, IgM) and cytokine (IL-10 and IL-6) levels in the serum were significantly higher in the B, B + P and B + P + S treatment groups (p < 0.05). The immune-related organs (bursa and spleen) were significantly influenced in the birds fed with P. pentosaceus GT001. No significant variation was noted among all the dietary treatments in terms of the measured meat quality indices. The small intestinal digesta content of the Salmonella load was below a detectable range after 14 days of infection (p < 0.05). No significant differences were observed among the different treatment groups in terms of the breast pH, drip loss and meat color (p > 0.05). The inclusion of P. pentosaceus GT001 also modified the community structure in the cecum. This indicates that it has health benefits and could be incorporated in the broiler diet.

The beneficial effects of a multistrain potential probiotic, formic, and lactic acids with different vaccination regimens on broiler chickens challenged with multidrug-resistant Escherichia coli and Salmonella

The effects of a multistrain potential probiotic (Protexin®), acids, and a bacterin from multidrug-resistant E. coli O26, O78, S. Enteritidis (1,9,12 g.m1,7), and S. Typhimurium (1,4,5,12.i.1,2) on the immune response, haematological parameters, cytokines, and growth parameters of broiler chickens challenged with bacterin live serotypes were investigated. Two experiments were designed using 300 one-day-old chicks (Arbor Acres) randomly assigned to 15 groups. The first experiment comprised 9 groups, including positive and negative control groups and other groups received Protexin®, acids, and the bacterin (0.2 ml/SC), either alone or in combination, on the 1st day. The second experiment contained 6 groups, including positive and negative control groups and other groups received a combination of Protexin®, acids, and the bacterin (0.5 ml/SC) on the 8th day. All the groups except the negative control groups were challenged on the 8th and 16th days in both experiments, respectively, with mixed live bacterin serotypes. The groups that received Protexin®, acids, and the bacterin either alone or in combination revealed significant improvements in the immune response to the bacterin (p ≤ 0.05). The groups in the 1st experiment and most the 2nd experiment groups showed a reduced mortality rate and decreased levels IFN-γ, IL-4, and IL-12 cytokines (p ≤ 0.05). Moreover, these groups demonstrated increases in haematological parameters and reduced rates of infection-caused anaemia. These groups showed significant increases in growth performance parameters, such as body weight, weight gain, and the feed conversion ratio (FCR) (p ≤ 0.05). There was a beneficial effect on 1-day-old chickens produced by combining Protexin®, acids, and the bacterin (0.2 ml/SC).

Escherichia coli Heat-Labile Enterotoxin B Subunit Combined with Ginsenoside Rg1 as an Intranasal Adjuvant Triggers Type I Interferon Signaling Pathway and Enhances Adaptive Immune Responses to an Inactivated PRRSV Vaccine in ICR Mice

Porcine reproductive and respiratory syndrome virus (PRRSV) is a major pathogen that has threatened the global swine industry for almost 30 years. Because current vaccines do not provide complete protection, exploration of new preventive strategies is urgently needed. Here, we combined a heat-labile enterotoxin B subunit of Escherichia coli (LTB) and ginsenoside Rg1 to form an intranasal adjuvant and evaluated its enhancement of immune responses in mice when added to an inactivated-PRRSV vaccine. The combination adjuvant synergistically elicited higher neutralizing and non-neutralizing (immunoglobulin G and A) antibody responses in the circulatory system and respiratory tract, and enhanced T and B lymphocyte proliferation, CD4⁺ T-cell priming, and cytotoxic CD4⁺ T cell activities in mononuclear cells from spleen and lung tissues when compared to the PRRSV vaccine alone, and it resulted in balanced Th1/Th2/Th17 responses. More importantly, we observed that the combination adjuvant also up-regulated type I interferon signaling, which may contribute to improvement in adaptive immune responses. These results highlight the potential value of a combined adjuvant approach for improving the efficacy of vaccination against PRRSV. Further study is required to evaluate the efficacy of this combined adjuvant in swine.

Challenges in Vaccinating Layer Hens against Salmonella Typhimurium

Salmonella Typhimurium is among the most common causes of bacterial foodborne gastrointestinal disease in humans. Food items containing raw or undercooked eggs are frequently identified during traceback investigation as the source of the bacteria. Layer hens can become persistently infected with Salmonella Typhimurium and intermittently shed the bacteria over the course of their productive lifetime. Eggs laid in a contaminated environment are at risk of potential exposure to bacteria. Thus, mitigating the bacterial load on farms aids in the protection of the food supply chain. Layer hen producers use a multifaceted approach for reducing Salmonella on farms, including the all-in-all-out management strategy, strict biosecurity, sanitization, and vaccination. The use of live attenuated Salmonella vaccines is favored because they elicit a broader host immune response than killed or inactivated vaccines that have been demonstrated to provide cross-protection against multiple serovars. Depending on the vaccine, two to three doses of Salmonella Typhimurium vaccines are generally administered to layer hens within the first few weeks. The productive life of a layer hen, however, can exceed 70 weeks and it is unclear whether current vaccination regimens are effective for that extended period. The objective of this review is to highlight layer hen specific challenges that may affect vaccine efficacy.

Effects of Achyranthes bidentata Polysaccharides on Intestinal Morphology, Immune Response, and Gut Microbiome in Yellow Broiler Chickens Challenged with Escherichia coli K88

The present study was conducted to investigate the effects of dietary Achyranthes bidentata polysaccharide (ABPS) supplementation on performance, immune response, intestinal mucosal morphology, and gut microbiome in yellow-feathered broilers challenged with Escherichia coli K88. A 2 × 2 factorial design was used for the trial. Two hundred and forty one-day-old female broilers were randomly assigned to four treatments: (1) negative-control broilers were fed by a basal diet and saline (NG); (2) positive-control broilers were fed by a basal diet and orally challenged with 10⁸ CFU E. coli K88 (CNG); (3) ABP group broilers were fed by a basal diet containing ABPS (500 mg/kg of feed) and saline; (4) CABP group broilers were fed by a basal diet containing ABPS (500 mg/kg of feed) and orally challenged with 10⁸ CFU E. coli K88. Growth performance, serum biochemical indexes, immune responses, intestinal mucosal morphology, and cecal microbial community structure were evaluated. The ABP group had greatest body weight (BW), average daily body weight gain (ADG), and intestinal villus height compared to other treatments (p < 0.05). The CABP group had a higher villus height/crypt depth ratio (V/C) compared with other treatments (p < 0.05). The expression levels of NF-κB were lower in the ABP group. The CNG group had higher Escherichia coli and Enterococcus contents in cecal samples compared to other treatments (p < 0.05). Serum glucose, uric acid, TNF-α, and Secretory Immunoglobulin A (S-IgA) levels were higher in broilers challenged with E. coli (p < 0.001) than that with saline. Broilers challenged with E. coli had reduced taxa richness in the cecal samples. Sequencing of 16S rRNA genes in cecal samples revealed that a lower proportion of Firmicutes and a higher proportion of Proteobacteria were detected in the broilers challenged with E. coli. Compared with the controls, dietary ABPS supplementation increased serum total protein, albumin, and S-IgA levels, but decreased serum glucose, uric acid, and TNF-α levels in broilers (p < 0.05). Diet supplemented with ABPS increased the Firmicutes/Bacteroidetes ratio and the abundance of Ruminococcaceae and Lachnospiraceae, and altered cecal microbiota community structure. These results suggest that ABPS can promote growth performance and improve intestinal morphology and microbiota community structure in broilers challenged with E. coli K88.

A Long-Term Efficacy Trial of a Live, Attenuated Salmonella Typhimurium Vaccine in Layer Hens

Salmonella remains one of the most common causes of bacterial foodborne gastrointestinal disease in humans. Raw eggs or food items containing undercooked eggs are frequently identified as the source of Salmonella. Salmonella Typhimurium contamination of table eggs most commonly occurs when they are laid in a contaminated environment. Several control strategies, including vaccination, are widely used to mitigate the total Salmonella load. It is unclear, however, whether live attenuated Salmonella vaccines are efficacious over the life span of a layer hen. Live attenuated Salmonella vaccines have been favored due to their ability to illicit a strong humoral immune response. The lifespan of a layer hen ranges between 60 and 80 weeks and the long term efficacy of attenuated vaccine strains has not been investigated. In this study, commercial brown layer chicks were vaccinated at day old, 6 weeks of age, and again at 10 weeks of age with the Bioproperties Vaxsafe^TM STM1 aroA mutant vaccine. Birds were challenged at 18 weeks of age with Salmonella Typhimurium DT9 (MLVA 03 15 08 11 550). Feces and eggs were monitored for S. Typhimurium for 40 weeks post-infection. Birds produced a strong immune response following the final dose which was administered intramuscularly. The serum antibody response to S. Typhimurium DT9 infection did not differ between challenged groups. Fecal shedding and egg contamination was highly variable and did not differ significantly between vaccinated and unvaccinated birds that had been challenged with S. Typhimurium DT9. Total bacterial load in feces was quantified using qPCR. No significant difference was detected between unvaccinated and vaccinated birds after challenge.

No protection in chickens immunized by the oral or intra-muscular immunization route with Ascaridia galli soluble antigen

In chickens, the nematode Ascaridia galli is found with prevalences of up to 100% causing economic losses to farmers. No avian nematode vaccines have yet been developed and detailed knowledge about the chicken immune response towards A. galli is therefore of great importance. The objective of this study was to evaluate the induction of protective immune responses to A. galli soluble antigen by different immunization routes. Chickens were immunized with a crude extract of A. galli via an oral or intra-muscular route using cholera toxin B subunit as adjuvant and subsequently challenged with A. galli. Only chickens immunized via the intra-muscular route developed a specific A. galli antibody response. Frequencies of γδ T cells in spleen were higher 7 days after the first immunization in both groups but only significantly so in the intra-muscularly immunized group. In addition, systemic immunization had an effect on both Th1 and Th2 cytokines in caecal tonsils and Meckel's diverticulum. Thus both humoral and cellular immune responses are inducible by soluble A. galli antigen, but in this study no protection against the parasite was achieved.

Effects of a probiotic, Enterococcus faecium, on growth performance, intestinal morphology, immune response, and cecal microflora in broiler chickens challenged with Escherichia coli K88

The effects of feeding dehydrated Enterococcus faecium on growth performance, immune response, and cecal microflora in broiler chickens challenged with Escherichia coli K88 were investigated. Two hundred eighty-eight 1-d-old birds were randomly assigned to 4 treatments: negative control birds (N-con) fed a basal diet and not challenged with E. coli K88; positive control birds (P-con) fed a basal diet and challenged with E. coli K88; birds fed a basal diet including dehydrated E. faecium (Ef) at 1 × 10(9) cfu/kg of feed and challenged with E. coli K88; and birds fed a basal diet including the antibiotic colistine sulfate (Anti) at 10 mg/kg of feed and challenged with E. coli K88. Birds fed E. faecium had greater (P < 0.05) BW on d 14, 21, and 28 and greater (P < 0.05) jejunal villus height on d 21 and 28 compared with birds on the other treatments. Jejunal crypt depth was decreased (P < 0.05) in birds fed either E. faecium or antibiotic compared with P-con treatment birds on d 10, 21, and 28. Birds fed E. faecium had a greater (P < 0.05) concentration of IL-4 in their jejunal mucosa than did those in the N-con treatment group on d 10, 14, and 21. Infected birds, with or without E. faecium feeding, had a higher (P < 0.05) tumor necrosis factor-α and secreted IgA in their jejunal mucosa than did those in the N-con treatment group on d 10 and 14. Birds fed E. faecium had lower (P < 0.05) concentrations of E. coli on d 14 and 28, less (P < 0.05) Clostridium perfringens on d 28, greater Lactobacillus counts on d 14 and 21, and greater (P < 0.05) Bifidobacterium in their cecal contents on d 21 than did the P-con birds. These results suggest that E. faecium can promote growth performance, improve intestinal morphology, and beneficially manipulate the cecal microflora in broilers challenged with E. coli K88.

Immunological responses to vaccination following experimental Lawsonia intracellularis virulent challenge in pigs

Although a live attenuated vaccine has been used extensively to provide immunity against porcine proliferative enteropathy (PE) caused by Lawsonia intracellularis, the nature of the protective response is an area of considerable interest for the control of PE. Two trials investigated immune responses in pigs after oral and intramuscular (IM) vaccination followed by virulent L. intracellularis challenge. After an oral vaccination with 10(5.9) TCID50 organisms, significantly increased serum and mucosal secretions of IgM, IgG and higher mucosal TNF-α and TGF-β1 were detected by day 17, together with a trend towards higher levels of IFN-γ and IL-6. Pigs vaccinated IM produced elevated serum antibody titres but mucosal immune responses were not detected. After challenge with virulent L. intracellularis, non-vaccinated control pigs had higher PE lesion scores and excreted significantly higher numbers of L. intracellularis in faeces than the vaccinated pigs. Reduced intestinal pathology and faecal L. intracellularis shedding were evident in the vaccinated groups. The results indicated that protection was associated with mucosal cytokine and specific IgG and IgA responses after vaccination and that systemic antibody responses were boosted following challenge. However in the search for an immune correlate with protection, a causal association was not evident from a kinetic analysis of immune parameters in serum, ileal pathology and faecal shedding.

Immunogenicity of novel nanoparticle-coated MSP-1 C-terminus malaria DNA vaccine using different routes of administration

An important aspect in optimizing DNA vaccination is antigen delivery to the site of action. In this way, any alternative delivery system having higher transfection efficiency and eventual superior antibody production needs to be further explored. The novel nanoparticle, pDNA/PEI/γ-PGA complex, is one of a promising delivery system, which is taken up by cells and is shown to have high transfection efficiency. The immunostimulatory effect of this novel nanoparticle (NP) coated plasmid encoding Plasmodium yoelii MSP1-C-terminus was examined. Groups of C57BL/6 mice were immunized either with NP-coated MSP-1 plasmid, naked plasmid or NP-coated blank plasmid, by three different routes of administration; intravenous (i.v.), intraperitoneal (i.p.) and subcutaneous (s.c). Mice were primed and boosted twice at 3-week intervals, then challenged 2 weeks after; and 100%, 100% and 50% mean of survival was observed in immunized mice with coated DNA vaccine by i.p., i.v. and s.c., respectively. Coated DNA vaccine showed significant immunogenicity and elicited protective levels of antigen specific IgG and its subclass antibody, an increased proportion of CD4(+) and CD8(+) T cells and INF-γ and IL-12 levels in the serum and cultured splenocyte supernatant, as well as INF-γ producing cells in the spleen. We demonstrate that, NP-coated MSP-1 DNA-based vaccine confers protection against lethal P. yoelii challenge in murine model across the various route of administration and may therefore, be considered a promising delivery system for vaccination.

Dietary supplementation with vitamin E modulates avian intestinal immunity

The effect of dietary vitamin E on immunoglobulin A (IgA) antibody production, which acts as the first line of defence at the intestinal mucosa, has not been evaluated in chickens. In the present study the impact of the inclusion of supplementary levels of vitamin E to the diet, on total and antigen-specific IgA antibody titres, T-cell subsets and Ia+ cells, was assessed. From hatching, chickens received a maize-based diet which was supplemented with either 25, 250, 2500 or 5000 mg dl-α-tocopherol acetate/kg. Primary immunisation with tetanus toxoid (T. toxoid) emulsified in a vegetable oil-in-water adjuvant was administered by the intraperitoneal route at 21 d of age. At 35 d of age all birds received an oral booster vaccination of T. toxoid. Significantly higher total IgA antibody titres were present in the day 42 intestinal scrapings of birds receiving the 5000 mg/kg vitamin E-supplemented diet (VESD) (P=0·05) and a notable increase was observed in birds receiving the 250 mg/kg VESD (P=0·06). At days 21 and 42 total serum IgA antibody titres of birds receiving the 250 mg/kg VESD was significantly higher (P<0·05) than the control birds. Following immunisation with T. toxoid, birds receiving the 250 and the 5000 mg/kg VESD had elevated anti-T. toxoid IgA antibody titres in final day intestinal scrapings, which, for the latter group was statistically significant (P=0·02). Both of these groups also demonstrated increased titres of anti-T. toxoid IgA in the serum at day 42. Birds receiving the 250 mg/kg VESD exhibited a notable increase in the percentage of T-helper cells and Ia+ cells in peripheral blood on day 26. The results illustrate the potential for some levels of dietary vitamin E supplementation to act as an immunomodulator of total and antigen-specific IgA antibody.

Memory antibody responses of broiler and leghorn chickens as influenced by dietary vitamin E and route of sheep red blood cell administration

Influences of dietary levels of vitamin E fed to hens and their progeny, and routes of SRBC inoculation on antibody responses of diverse populations of chickens were studied. Populations were a commercial broiler sire line (C), 2 commercial broiler dam lines (A and B), and Leghorn lines selected for high (H) or low (L) antibody response to SRBC. Dams from lines A and B were fed diets supplemented with either 10 or 300 IU/kg of vitamin E, whereas dams from lines H and L received only the diet with 10 IU of vitamin E/kg. Progeny from matings of C males with A and B females as well as H and L females mated to males from their respective lines were hatched on the same day and fed diets supplemented with either 10 or 300 IU/kg of vitamin E. Breeders were the same age and eggs were incubated in the same machine. Chicks were inoculated on d 14 intravenously with 0.1 mL of a 0.5% suspension of SRBC or intramuscularly with 0.1 mL of a 25% suspension of SRBC. Antibody response was measured 6 and 14 d later. Chicks received a booster i.m. inoculation of 0.1 mL of 25% SRBC on d 28. Titers were again measured 6 and 14 d later. Level of vitamin E fed to dams did not affect progeny BW or plasma vitamin E levels. Although titers were higher following i.v. than i.m. inoculation, the degree of difference varied among stocks. Dietary vitamin E level interacted with inoculation route with a greater response to the higher than lower level of vitamin E for i.v., but there was no difference for i.m. There were stock x level of vitamin E and stock x route of inoculation interactions for secondary responses to SRBC inoculation. Stock rankings after the first inoculation were not predictive of the rankings after the second inoculation. The 30-fold increase in dietary level of vitamin E resulted in >12-fold differences in plasma levels of vitamin E. Overall, there was a stock-dependent influence of dietary vitamin E on growth and humoral antibody response.

Safety and efficacy ofSalmonellagallinarum9R vaccine in young laying chickens

Salmonella enterica subsp. enterica serovar Gallinarum (S. gallinarum) is the agent of fowl typhoid, and the 9R vaccine is a commercially available, live vaccine for the prevention of fowl typhoid. The aim of this study was to assess the safety and efficacy of the 9R vaccine in young chickens. The mean weights of 5-week-old chickens vaccinated with one and 10 doses at 2 weeks old were 450.3+/-33.83 g and 446.8+/-35.68 g, respectively, which were statistically lower (P<0.05) than the mean weight (475.5+/-44.17 g) of the control group. Using the same procedure, the mean weights of chickens vaccinated with one and 10 doses at the age of 4 and 6 weeks were 721.3+/-64.03 g and 723.7+/-63.92 g, and 1114.2+/-92.21 g and 1078.27+/-68.93 g, respectively. Compared with the mean weights (725.7+/-49.50 g and 1104.3+/-92.34 g, respectively) of the control groups, there was no difference in terms of statistical significance (P < 0.05). In addition, all vaccinated birds showed no clinical signs and survived the time course of the experiment. When all chickens were challenged with the wild-type S. gallinarum 21 days after one-dose vaccination, the mortalities between the vaccinated group and the control group were 0% to 5% and 95% to 100%, respectively. In addition, the control group demonstrated a 95% to 100% re-isolation rate of the challenge strain in internal organs and the caecum, while in the vaccinated group only a 1% to 60% re-isolation rate was observed. In this study, we showed that adjusting the minimum vaccination age of the 9R vaccine to 4 weeks is acceptable considering the safety and efficacy of the vaccine.

Effects of Lactobacilli and an acidophilic fungus on the production performance and immune responses in broiler chickens

Accumulated lines of evidence indicate that inactivated probiotics could have beneficial effects similar to those of live probiotics. Two strains of disrupted, cobalt-enriched, lactic acid bacteria (Lactobacillus acidophilus and Lactobacillus casei) and a disrupted fungal mycelium (Scytalidium acidophilum) were spray-mixed onto a mash basal feed, in 2 concentrations, prior to pelleting. The effects of these probiotics on production performance and immune response in broiler chickens were investigated. The production parameters, including BW, feed intake (FI), BW gain (BWG), and feed conversion ratio (FCR), were monitored weekly during a 6-wk trial. The immune response was evaluated by immunizing the birds with the antigen keyhole limpet hemocyanin (KLH) followed by a serological assay to measure blood IgA and IgG titers. Some of the production parameters were significantly improved by low L. casei (LCL; for BW and BWG), high L. acidophilus (LAH; for BW and BWG), and high fungal (FH; for BW, BWG, and FI) in comparison with the nonadditive control (NC-). However, these 3 treatments (LCL, LAH, and FH) did not enhance the measured immune responses. Instead, the titers of serum KLH-specific IgA in high L. casei (LCH) and low L. acidophilus (LAL) were significantly higher than those of NC-, 10 d after immunization. None of the probiotic treatments increased the titer of KLH-specific IgG in blood. Our results indicate that disrupted and cobalt-enriched L. acidophilus or L. casei was able to enhance production performance of broiler chickens. The fungal mycelium, S. acidophilum, when used at a high concentration, also demonstrated its potential for the first time to be used as a probiotic. In addition, the optimal concentration for administering probiotics is strain dependent. A higher dose does not always result in a better performance.

Improvement of the systemic prime/oral boost strategy for systemic and local responses

This paper describes oral boost immunisations of primed animals as an alternative oral vaccination strategy. Mice were primed orally (PO), intranasally (IN), subcutaneously (SC), or intraperitoneally (IP) with ovalbumin (OVA) with or without adjuvant. Boost immunisations were given orally with or without cholera toxin (CT) as adjuvant. Prime immunisations induced variable IgA and IgG(1) titres in serum depending on the route. A subsequent oral boost increased these titres. Use of an adjuvant in the priming significantly increased serum IgA and, to a lesser extend, IgG(1). Oral boost immunisation induced significantly higher serum IgA titres in animals primed via the SC, IP and the IN route compared to the PO route. This was independent of the use of CT. Three oral boosts with OVA plus 5 microg CT given in 5 days to primed mice revealed higher IgA titres compared to single oral boosts and anti-OVA IgA titres in faeces were also detected. Finally, we put together our findings and propose a systemic priming/oral boost strategy in which mice were primed via the SC route with 100 microg OVA plus 50 microg Butyl16-p(AA), and subsequently orally boosted with three doses of 300 microg OVA plus 5 microg CT each. We concluded that oral immunisation is more effective in IN, SC, or IP primed mice than in PO primed mice, and that the IgA antibody response in serum and faeces can be improved by increasing the immunisation frequency and the use of appropriate adjuvants in primary and boost immunisation. The here-formulated strategy improves the probability of success of oral vaccination. The results are discussed in the light of the development of edible vaccines.

Effect of route of inoculation on humoral immune response of White Leghorn chickens selected for high or low antibody response to sheep red blood cells

Effects of route of SRBC inoculation and antigen dosage on primary and secondary antibody response of White Leghorn lines selected for high (HA) or low (LA) 5-d antibody response to a single i.v. inoculation with 0.1 mL of a 0.25% suspension of SRBC were studied in two trials. In the first trial, chicks from parents of generation S24 of each line were randomly assigned to one of four treatments. At 35 d of age, they were inoculated into the brachial vein with 0.1 mL of 0.25% suspension of SRBC or into the breast muscle with 0.1 mL of 0.25, 2.50, or 25.00% SRBC. Plasma SRBC antibody was measured 3, 6, 10, and 20 d later. In the second trial, chicks from parents of generation S25 of each line were randomly assigned to treatment groups. At 28 d of age they were inoculated with 0.1 mL of 0.25% SRBC into the brachial vein, 0.1 mL of 25.00% SRBC into the thigh (T-L) or breast muscle (B-L), or 0.5 mL of 25.00% SRBC into the thigh (T-H) or breast muscle (B-H). Twenty-one days later, chicks (except five per group) were given a booster inoculation of 0.1 mL of 25.00% SRBC into the thigh muscle. Six and 10 d after each inoculation, plasma SRBC antibody, IgG, and IgM titers were measured. The SRBC antibody titers after primary i.v. inoculation with SRBC were always higher for HA than LA chicks. When inoculations were i.m., differences between lines varied with dosage. Low dosages inoculated into the breast failed to induce line differences consistently, whereas at higher dosages, titers were greater for HA than LA chicks regardless of inoculation site. For Line LA, inoculation into the thigh elicited higher titers than inoculations into the breast. Antibody titers to the booster inoculation of SRBC were similar for the lines.

Humoral immunity to cholera toxin and ovalbumin in the brushtail possum (Trichosurus vulpecula)

AIM

To compare the humoral immune responses of female possums to ovalbumin (OVA) and cholera toxin (CT) administered using different routes and dosage regimes.

METHODS

Three groups of mature female possums were immunised intragastrically (n=15) or surgically (intraileal, n=4; Peyer's patches, n=4). Levels of antibodies to OVA and CT in serum, ileal, vaginal, oviduct and uterine secretions were measured by indirect enzyme-linked immunosorbent assay (ELISA). All manipulations were conducted under general anaesthesia.

RESULTS

Antibodies to CT increased significantly in serum (p<0.001) and in lateral vaginal secretions (p<0.05) after intragastric immunisation using 250-1000 microg CT. Simultaneous intragastric administration of CT with 3 mg OVA did not significantly increase antibody levels to OVA. When OVA (3 mg) and CT (250 microg) were injected into the ileum, followed by intragastric administration 4 weeks later, antibody levels to CT were significantly (p<0.05) increased in serum, uterine and medial vaginal secretions, and antibody levels to OVA were significantly (p<0.05) increased in serum and medial vaginal secretions. When OVA (3 mg) with Incomplete Freund's adjuvant was injected directly into Peyer's patches, followed by peritoneal administration 4 weeks later, antibody levels in serum, ileal and reproductive-tract secretions were generally higher than those that resulted from the other immunisation treatments.

CONCLUSIONS

Administration of OVA induced an antibody response in serum and in reproductive and alimentary tract secretions when administered with CT directly into the ileum, or when injected into Peyer's patches and peritoneum. CT was a potent enteric immunogen.

Salmonella: immune responses and vaccines

Salmonella infections are a serious medical and veterinary problem world-wide and cause concern in the food industry. Vaccination is an effective tool for the prevention of Salmonella infections. Host resistance to Salmonella relies initially on the production of inflammatory cytokines leading to the infiltration of activated inflammatory cells in the tissues. Thereafter T- and B-cell dependent specific immunity develops allowing the clearance of Salmonella microorganisms from the tissues and the establishment of long-lasting acquired immunity to re-infection. The increased resistance that develops after primary infection/ vaccination requires T-cells cytokines such as IFNgamma TNFalpha and IL12 in addition to opsonising antibody. However for reasons that are not fully understood seroconversion and/or the presence of detectable T-cell memory do not always correlate with the development of acquired resistance to infection.Whole-cell killed vaccines and subunit vaccines are used in the prevention of Salmonella infection in animals and in humans with variable results. A number of early live Salmonella vaccines derived empirically by chemical or u.v. mutagenesis proved to be immunogenic and protective and are still in use despite the need for repeated parenteral administration. Recent progress in the knowledge of the genetics of Salmonella virulence and modern recombinant DNA technology offers the possibility to introduce multiple defined attenuating and irreversible mutations into the bacterial genome. This has recently allowed the development of Salmonella strains devoid of significant side effects but still capable of inducing solid immunity after single oral administration. Live attenuated Salmonella vaccines have been used for the expression of heterologous antigens/proteins that can be successfully delivered to the immune system. Furthermore Salmonella can transfer plasmids encoding foreign antigens under the control of eukaryotic promoters (DNA vaccines) to antigen-presenting cells resulting in targeted delivery of DNA vaccines to these cells. Despite the great recent advances in the development of Salmonella vaccines a large proportion of the work has been conducted in laboratory rodents and more research in other animal species is required.

Vaccines against the avian enteropathogens Eimeria, Cryptosporidium and Salmonella

The worldwide poultry industry provides a substantial proportion of the nutritional requirement of the human population. To keep pace with the increasing demand for the high-quality, low-cost protein source that poultry provides, intensive rearing practices have been developed within the past few decades. For example, chickens are housed routinely in crowded environments under adverse conditions, and genetic strains have been selected for rapid growth, high protein-to-fat content and superior egg-laying characteristics. A major negative consequence of these practices has been an increase in the incidence of diseases. Enteric diseases in particular have emerged as a major problem threatening the future viability of the poultry industry. A variety of methods have been used to combat avian diseases in the commercial setting, including improved farm management practices, the use of antibiotic drugs, the selection of disease-resistant strains of chickens, and the manipulation of the chicken's immune system. In the latter category, the development of vaccines against the major avian diseases has become a priority in the poultry industry. This review will highlight recent progress in vaccine development against three major avian enteric pathogens: Eimeria, Cryptosporidium and Salmonella.

Immunity, vaccination and the avian intestinal tract

Defence of the intestinal mucosal surface from enteric pathogens is initially mediated by secretory IgA (SIgA). As oral immunization of non-replicating antigen induces minimal SIgA antibody titers, novel immunization strategies which selectively induce mucosal immune responses in mammals are now being assessed in chickens. The strategies reviewed include the route of antigen delivery, the incorporation of antigenic components in delivery vehicles, the inclusion of immunomodulators in the vaccine formula or in the diet, and manipulation of intestinal microflora. The differences in anatomical organization and immunological mechanisms between birds and mammals must be considered when manipulating avian intestinal immunity with the latest immunotechnologies developed for mammals. Our knowledge of the function and functioning of the avian mucosal system is discussed. Progress in our understanding of this system, the location of precursor IgA B cells and antigen sampling by these sites is not as advanced as knowledge of the mammalian system, highlighting the need for ongoing research into the avian application of novel vaccination strategies.