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1.
Verocytotoxic Escherichia (E.) coli strains are responsible for swine oedema disease, which is an enterotoxaemia that causes economic losses in the pig industry. The production of a vaccine for oral administration in transgenic seeds could be an efficient system to stimulate local immunity. This study was conducted to transform tobacco plants for the seed-specific expression of antigenic proteins from a porcine verocytotoxic E. coli strain. Parameters related to an immunological response and possible adverse effects on the oral administration of obtained tobacco seeds were evaluated in a mouse model. Tobacco was transformed via Agrobacteium tumefaciens with chimeric constructs containing structural parts of the major subunit FedA of the F18 adhesive fimbriae and VT2e B-subunit genes under control of a seed specific GLOB promoter. We showed that the foreign Vt2e-B and F18 genes were stably accumulated in storage tissue by the immunostaining method. In addition, Balb-C mice receiving transgenic tobacco seeds via the oral route showed a significant increase in IgA-positive plasma cell presence in tunica propria when compared to the control group with no observed adverse effects. Our findings encourage future studies focusing on swine for evaluation of the protective effects of transformed tobacco seeds against E. coli infection.  相似文献   

2.
Intestinal contents of suckling (n?=?45) and newly weaned (n?=?45) piglets, suffering from diarrhea in the province of Villa Clara in Cuba, were tested for viral, bacterial, and parasitic enteropathogens from May to June 2008. At least one enteropathogen was identified in 53.3 % of piglets and enterotoxigenic Escherichia coli (ETEC; 25.6 %) was the major pathogen; mostly STa+/STb+ or F4+/STa+/STb+ ETEC were isolated. The overall occurrence of the rest of pathogens was 10 % for transmissible gastroenteritis virus (TGEV) and Cryptosporidium parvum, 6.7 % for rotavirus A and Isospora suis, 5.6 % for α-toxigenic Clostridium perfringens, 3.3 % for verotoxigenic E. coli (VTEC), and 2.2 % for Salmonella enterica subspecies enterica serovar Newport. TGEV and α-toxigenic C. perfringens were only identified in suckling piglets, while Salmonella Newport and VTEC were only detected in weaned pigs. Porcine epidemic diarrhea virus (PEDV), β-toxigenic C. perfringens, Eimeria spp., and helminths were not identified. Eight kinds of mixed infections were detected in 25 % of enteropathogen positive piglets. ETEC was present in 10 of 12 mixed infections, and TGEV infections were never combined. This survey demonstrates that several enteropathogens are circulating in piggeries located in the province of Villa Clara in Cuba, and that is necessary to improve surveillance, prevention, and control of enteric infections in order to increase production efficiency.  相似文献   

3.
F4 enterotoxigenic Escherichia coli (ETEC) cause diarrhoea and mortality in piglets leading to severe economic losses. Oral immunization of piglets with F4 fimbriae induces a protective intestinal immune response evidenced by an F4-specific serum and intestinal IgA response. However, successful oral immunization of pigs with F4 fimbriae in the presence of maternal immunity has not been demonstrated yet. In the present study we aimed to evaluate the effect of maternal immunity on the induction of a systemic immune response upon oral immunization of piglets. Whereas F4-specific IgG and IgA could be induced by oral immunization of pigs without maternal antibodies and by intramuscular immunization of pigs with maternal antibodies, no such response was seen in the orally immunized animals with maternal antibodies. Since maternal antibodies can mask an antibody response, we also looked by ELIspot assays for circulating F4-specific antibody secreting cells (ASCs). Enumerating the F4-specific ASCs within the circulating peripheral blood mononuclear cells, and the number of F4-specific IgA ASCs within the circulating IgA+ B-cells revealed an F4-specific immune response in the orally immunized animals with maternal antibodies. Interestingly, results suggest a more robust IgA booster response by oral immunization of pigs with than without maternal antibodies. These results demonstrate that oral immunization of piglets with F4-specific maternal antibodies is feasible and that these maternal antibodies seem to enhance the secondary systemic immune response. Furthermore, our ELIspot assay on enriched IgA+ B-cells could be used as a screening procedure to optimize mucosal immunization protocols in pigs with maternal immunity.  相似文献   

4.
The enhanced effect of cytokine combinations has been assessed empirically, based on their immunobiological mechanisms. However, far less is known of the enhanced protection of practical cytokine combinations against viral infection in the livestock industry, due to cost and production issues associated with mass administration. This study demonstrates the enhanced protection of oral co-administration of swine interferon-α (swIFN-α) and interleukin-18 (swIL-18) against infection with transmissible gastroenteritis virus (TGEV) in piglets using attenuated Salmonella enterica serovar Typhimurium as carrier of cytokine proteins. A single oral co-administration of S. enterica serovar Typhimurium expressing swIFN-α and swIL-18 induced enhanced alleviation of the severity of diarrhea caused by TGEV infection, compared to piglets administered S. enterica serovar Typhimurium expressing swIFN-α or swIL-18 alone. This enhancement was further observed by the reduction of TGEV shedding and replication, and the expression of IFN-stimulated gene products in the intestinal tract. The results suggest that the combined administration of the swIFN-α and swIL-18 cytokines using attenuated S. enterica serovar Typhimurium as an oral carrier provides enhanced protection against intestinal tract infection with TGEV.  相似文献   

5.
Porcine edema disease (ED) is a life-threatening toxemia caused by enteric infection with Shiga toxin 2e (Stx2e)-producing Escherichia coli (STEC) in weaned piglets. We previously reported that the stx2eB-transgenic lettuce 2BH strain shows potential for use as an oral vaccine candidate against ED. However, the 2BH strain expressed a hemagglutinin (HA)-tag together with Stx2eB and contained non-canonical N-glycosylation. Therefore, we developed two Stx2eB-lettuce strains, the 3 (G+) strain in which the HA-tag was removed from 2BH, and the 3 (G-) lettuce strain, in which the 73rd Asn was replaced with Ser to prevent non-canonical N-glycosylation of Stx2eB from the 3 (G+) strain. We examined the protective effect of these newly developed two strains compared with the previous 2BH strain against ED using a colostrum-deprived piglet STEC infection model. We found that the N-glycosylated 2BH and 3 (G+) strains relieved the pathogenic symptoms of ED in STEC-challenged piglets, whereas the non-glycosylated 3 (G-) strain did not. N-Glycosylation of the Stx2eB product in lettuce may be involved in the immune response in piglets.  相似文献   

6.
We have previously developed a novel attenuated Salmonella Typhimurium (S. Typhimurium) ΔcpxR Δlon vaccine. This study was carried out to examine whether this vaccine could effectively protect growing piglets against Salmonella infection. Attenuated S. Typhimurium secreting the B subunit of Escherichia coli heat-labile enterotoxin was also used as a mucosal adjuvant. Pregnant sows in groups A and B were primed and boosted with the vaccine and mucosal adjuvant, whereas sows in groups C, D and E received PBS. Piglets in groups A and C were intramuscularly primed with formalin-inactivated vaccine and orally boosted with live vaccine, while piglets in groups B, D and E received PBS. Piglets in groups A, B, C, and D were challenged with a wild type virulent S. Typhimurium at the 11th weeks of age. Colostrum sIgA and IgG titers in vaccinated groups A and B sows were approximately 50 and 40 times higher than those of non-vaccinated groups C, D and E sows (P < 0.001). Serum IgG titers of group A piglets were also significantly higher than those of groups D and E piglets during the study (P < 0.001). Furthermore, no clinical signs were observed in group A piglets during the entire experimental period after the challenge, while diarrhea was observed in many of the piglets in groups B, C, and D. No Salmonella was isolated from fecal samples of the groups A and C piglets on day 14 after challenge, whereas the challenge strain was isolated from several piglets in groups B and D. These results indicate that vaccination of the piglets with the vaccine and mucosal adjuvant in addition to vaccination of their sows induced effective protection against Salmonella infections in the growing piglets.  相似文献   

7.
Eleven of 20 piglets inoculated orally with Escherichia coli:0101:KU460(A):NM and one of 18 piglets inoculated orally with E. coli:08:K87, K88a, b:H19 developed enteric colibacillosis. Successful reproduction of the disease was associated with recovery of a dense growth in a nearly pure culture of the inoculated strain from the feces. Piglets which remained clinically normal had none, or very few, of the inoculated strain in their feces. Seventeen control piglets inoculated orally with the non-enteropathogenic E. coli:043:K —:H28 remained normal.  相似文献   

8.
Porcine edema disease (ED) is a toxemia that is caused by enteric infection with Shiga toxin 2e (Stx2e)‐producing Escherichia coli (STEC) and is associated with high mortality. Since ED occurs most frequently during the weaning period, preweaning vaccination of newborn piglets is required. We developed stx2eB‐transgenic lettuce as an oral vaccine candidate against ED and examined its protective efficacy using a piglet STEC infection model. Two serially developed Stx2eB‐lettuce strains, 2BN containing ingredient Stx2eB constituting a concentration level of 0.53 mg Stx2eB/g of powdered lettuce dry weight (DW) and 2BH containing ingredient Stx2eB constituting a concentration level of 2.3 mg of Stx2eB/g of powdered lettuce DW, were evaluated in three sequential experiments. Taken the results together, oral administration of Stx2eB‐lettuce vaccine was suggested to relieve the pathogenic symptoms of ED in piglets challenged with virulent STEC strain. Our data suggested that Stx2eB‐lettuce is a promising first oral vaccine candidate against ED.  相似文献   

9.
To examine and compare the pathogenicity of cytotoxic necrotising factor (CNF)-producing Escherichia coli, two litters of piglets were infected orally with 1010E coli O88 or 1010E coli O32 strains. Of the six piglets infected with E coli O88, two died within 24 hours and three developed blood-stained diarrhoea. The other piglets were killed one, five, six and eight days after infection, when bacterial cultures indicated an overwhelming bacteraemic infection with E coli O88 in the early stages followed by clearance through the large intestine. The pathological changes consisted of an early enteritis, progressing to enterocolitis and a bacteraemic spread to the lungs. The histopathological changes were characteristic of toxaemic effects in brain, heart, liver and kidney, and characterised by congestion, oedema and exudation. Infection with E coli O32 produced a milder but similar enterocolitis, also with bacterial colonisation in the lungs. The histopathological findings again reflected a toxaemia. The enteritis was more persistent after E coli O32 infection and the strain persisted in large numbers in the intestine. No evidence of bacterial adherence to the intestinal mucosa was found with either strain. Enteroinvasion was only evident in one E coli O884-nfected piglet, but the consistent occurrence of interstitial pneumonia showed the predilection of these organisms for the lung. The results confirm the toxigenic properties of CNF+E coli and suggest an important role for this organism in enteric infection of young pigs.  相似文献   

10.
《Veterinary microbiology》1986,11(3):271-283
Escherichia coli colonies isolated from 50 diarrhoeic and 29 healthy piglets were investigated for several properties related to pathogenicity, such as production of heat-labile (LT) and heat-stable (STa) enterotoxins, presence of K88 and K99 colonization antigens, mannose-resistant haemagglutinating activity (MRHA), β-haemolysis and antibiotic resistance. The objective was to establish the toxic and adhesive abilities of E. coli strains that cause porcine diarrhoea in Galician farms. Fifty-seven colonies from 14 diarrhoeic piglets formed STa, while no STa+ colony was detected from healty piglets. Thirty-four of the 57 STa+ colonies were resistant to gentamicin. Sixteen representative STa+ strains isolated from the 14 infected piglets were serotyped, investigated for plasmid content and examined by electron microscopy. Of these STa+ strains, 15 belonged to serotype 0141:K85ab and carried on their surface the fimbrial antigen P987. The remaining representative STa+ strain belonged to serotype 0101:K30 and was K99+, being the only STa+ strain with MRHA activity. All 15 STa+ P987+ strains possessed a similar plasmid pattern, with three plasmids ranging in molecular weight from 33 × 106 to 74 × 106; nine of the gentamicin-resistant strains possessed an additional plasmid of molecular weight 16 × 106, which was absent in the six gentamicin-sensitive strains. Strains producing LT or K88 antigen were not detected. Forty-one MRHA+ colonies were isolated at similar rates from both diarrhoeic and healthy piglets. Twelve of the 19 non-enterotoxigenic MRHA+ strains of which the O-group was established, belonged to serogroups (01, 02, 07, 08, 09 and 075) typical of the human E. coli strains that cause extraintestinal infections. Finally, a statistically significant association between haemolytic and MRHA activities in porcine E. coli was found. In conclusion, it was found that STa+E. coli strains belonging to serotype 0141:K85ab:P987 are associated with porcine diarrhoea in Galicia. Additionally, no correlation between the isolation of non-ETEC MRHA+ strains and diarrhoea was observed.  相似文献   

11.
Enhancing and/or modulating innate and adaptive immunity by cytokines appears to be greatly useful to provide effective protective immunity against infectious diseases. However, an effective delivery system for mass administration in livestock industry is needed because of limitations such as cost, labor, time, and protein stability. Here the immunomodulatory functions of swine interleukine-18 (swIL-18), known as IFN-γ-inducing factor (IGIF), were evaluated in a vaccination model of pseudorabies virus (PrV) using attenuated Salmonella enterica serovar Typhimurium as the oral delivery system. The oral administration of S. enterica serovar Typhimurium expressing swIL-18 prior to vaccination with inactivated PrV vaccine induced enhanced levels of serum PrV-specific IgG and its IgG2 isotype, compared to administration of S. enterica serovar Typhimurium harboring the empty vector. Furthermore, S. enterica serovar Typhimurium expressing swIL-18 mounted Th1-biased cellular immune responses against PrV antigen, as evaluated by the production of IFN-γ and IL-4 from peripheral blood mononuclear cells of piglets. Subsequently, Th1-biased immunity induced by S. enterica serovar Typhimurium expressing swIL-18 showed rapid response and rendered piglets displayed more alleviated clinical signs following the virulent PrV challenge. Also, this alleviation of clinical signs was further confirmed by the reduction of nasal excretion of PrV after challenge. The present study demonstrates the extended use of immunomodulatory functions of swIL-18 orally delivered by attenuated S. enterica serovar Typhimurium.  相似文献   

12.
Oral administration of attenuated Salmonella vaccine may provide valuable advantages such as low cost, easy preparation, and safety. Attenuated Salmonella vaccines also serve as carriers of foreign antigens and immunomodulatory cytokines. Presently, an attenuated Salmonella enterica serovar Typhimurium strain was used as a carrier for open reading frame 7 (ORF7) protein of porcine reproductive and respiratory syndrome virus (PRRSV), a swine pathogen of significant global economic importance. Initially, an attenuated S. enterica serovar Typhimurium expressing ORF7 gene derived from PRRSV Korean isolate was constructed. Following oral administration of a single dose of the attenuated Salmonella vaccine expressing PRRSV ORF7, humoral and cell-mediated immune responses specific for ORF7 were induced at both systemic and mucosal sites including spleen, mesenteric lymph node, Peyer's patch, and laminar propria, as evaluated by determining serum ORF7-specific IgG and mucosal IgA responses, as well as Th1- and Th2-type cytokine production from antigen-stimulated T cells. The induced humoral responses were sustained for at least 12 weeks post-immunization. In particular, the immunized mice displayed immune responses to both the foreign ORF7 antigen and Salmonella itself. The results indicate the value of attenuated S. enterica serovar Typhimurium as an oral carrier of PRRSV antigenic proteins to induce effective systemic and mucosal immunity.  相似文献   

13.
The efficacy of a new vaccine against neonatal Escherichia coli diarrhoea in piglets containing purified F4ab, F4ac, F5 and F6 fimbriae and detoxified heat‐labile toxin (LT) was tested in challenge experiments by the method described by the European Pharmacopoeia (3rd edn, EDQM, Council of Europe, Strasbourg, France). A group of 11 young sows from a herd without E. coli problems was vaccinated 6–8 and 2–4 weeks prior to expected farrowing and another group of nine young sows were non‐vaccinated controls. Escherichia coli antibody titres were determined in serum samples taken from the sows before first vaccination and before farrowing and in colostrum samples. The newborn piglets were allowed to suckle colostrum from their mother immediately after birth. The piglets were marked with individually numbered ear tags. Approximately 12 h after birth, 118 piglets from vaccinated sows and 79 piglets from non‐vaccinated control sows were challenged by oral instillation of 5 ml of a freshly prepared culture of one of the challenge strains [O8:K87:F4ab (LT+) or O149:K91:F4ac (LT+) or O9:K30:F5 or O9:K103:F6 respectively]. The challenge cultures contained as a mean 6.8 × 109 CFU/ml. After challenge the piglets were observed for 7 days and mortality and morbidity were recorded. Vaccinated sows developed significant levels of antibody titres in colostrum and serum. Control sows stayed at a low/seronegative level. The protective efficacy was excellent because 66.7–87.5% of the piglets from vaccinated sows remained without clinical signs after challenge. Only 0.0–28.0% of the piglets from non‐vaccinated sows remained healthy and more than 47.1% of the piglets in this group died after challenge. It is concluded that the new vaccine is very effective in protection of piglets against neonatal E. coli diarrhoea.  相似文献   

14.
Colibacillosis is a systemic disease responsible for important economic losses in poultry breeding; fluoroquinolones, including danofloxacin, are used to treat diseased animals. The purpose of the present study was to estimate pharmacokinetic–pharmacodynamic (PK-PD) surrogates for bacteriostasis, bactericidal activity and bacterial elimination against Escherichia coli O78/K80, using a PK-PD approach, for danofloxacin in turkeys after oral administration. Eight healthy turkeys, breed BUT 9, were included in a two-way crossover study. The drug was administered intravenously (i.v.) and orally at a dose rate of 6 mg/kg bw. The values of the elimination half-life and the total body clearance after i.v. administration were 8.64 ± 2.35 h and 586.76 ± 136.67 ml kg-1h-1, respectively. After oral administration, the values of the absolute bioavailability and the elimination half-life were 78.37± 17.35% and 9.74± 2.93 h, respectively. The minimum inhibitory concentration against the investigated strain in turkey serum was 0.25 μg/ml, four times higher than in broth. The lowest effective ex vivo AUC24/MIC ratios required for bacteriostasis, bactericidal activity, and total killing of E. coliO78/K80 were 0.416 h, 1.9 h and 6.73 h, respectively. The oral dose of 6 mg/kg used in the present study could be interpreted as being sufficient to eliminate E. coli with an MIC 0.25 μ g/ml. However, considering the demand that antimicrobial resistance should be avoided by complete bacterial elimination, PK-PD considerations suggest that an even higher dose of 32 mg/kg per day or 0.7 mg/kcal per day should be evaluated in clinical trials.  相似文献   

15.
To counteract the effects of perinatal hypoxia in piglets, the oral administration of caffeine to sows with induced parturition was evaluated. On day 113 of gestation 9 sows received 27 mg/kg body weight (BW) of caffeine mixed with 200 g of standard diet. The same amount of feed without the addition of caffeine was administered to 9 control sows. Additionally, on day 113 of gestation, all sows were treated by two injections in the perianal area of 1 mg of alfaprostol (at 8:00 am and 14:00 pm), and on the morning of farrowing by 14 IU of oxytocin in the perianal area. Caffeine did not affect BW of piglets and size of litters; however piglets from treated sows showed a higher capacity to adapt to extra-uterine life. Particularly, they showed a greater thermoregulatory ability (P<0.001) and a higher percentage of viability score≥7 compared to piglets from control sows (92% vs. 75%, respectively; P=0.030). Caffeine furthermore reduced the frequency of high serum biopterin values (>80 nmol/L) in piglets born from treated sows (P=0.001). In conclusion, the caffeine orally administered to sows with induced parturition showed a protective effect on the consequences of neonatal hypoxia in tissue ischemia–reperfusion injury in piglets.  相似文献   

16.
The neonatal requirements for maternal passive immunity and the lactation immunobiology with regard to sow immunisation for neonatal protection are reviewed. A vaccination protocol which combines oral and parenteral antigen administration to produce antibody activity mediated mainly by IgM is described. Its efficacy in affording protection to neonatal piglets was tested against a lethal oral infection with a virulent strain of Escherichia coli "Abbottstown". Piglets suckled on vaccinated or non-vaccinated sows were exposed to an infective challenge in the gastrointestinal tract and the relative pathology in test and control groups observed over the neonatal period. Death ensued in 76 per cent of piglets suckled on control sows and 26 per cent of piglets suckled on sows vaccinated by two intramuscular injections. Litters suckled on orally vaccinated sows were able to resist a similar infective challenge, there being only one fatality out of 42 piglets.  相似文献   

17.
Mucosal immunization is advantageous over other routes of antigen delivery because it can induce both mucosal and systemic immune responses. In this study, we have developed fimbriae protein of enterotoxigenic Escherichia coli (ETEC) F41 was stably expressed on the surface Lactobacillus casei 525. The method of expressing vaccine antigens in L. casei induces both systemic and mucosal immunity after oral or intranasal administration. We demonstrate that an oral or intranasal vaccine based on live recombinant L. casei 525 protects infant mice from ETEC F41 infection. This platform technology can be applied to design oral or intranasal vaccine delivery vehicles against several microbial pathogens.  相似文献   

18.
The goal of the current experiment was to assess the clinical efficacy of oxfendazole (OFZ) administered as a single oral dose (30 mg/kg) to pigs naturally parasitized with Ascaris suum, Oesophagostomum spp., Metastrongylus spp. and Trichuris suis. Thirty-six local ecotype piglets were divided into three independent experiments, named I, II and III (n = 12 each), respectively. Each experiment involved two different groups (n = 6): Untreated Control and OFZ treated. Animals were naturally parasitized with A. suum (Experiments I, II and III), Oesophagostomum spp. (Experiments I and II), T. suis (Experiments II and III) and Metastrongylus spp. (Experiment I). Pigs in the treated group received OFZ (Synanthic®, Merial Ltd., 9.06% suspension) orally at 30 mg/kg dose. At five (5) days post-treatment, animals were sacrificed and the clinical efficacy of the OFZ treatment was established following the currently available WAAVP guidelines for a controlled efficacy test. None of the animals involved in this experiment showed any adverse events during the study. OFZ treatment given as a single 30 mg/kg oral dose showed a 100% efficacy against all the nematode parasites present in the three experiments. In conclusion, under the current experimental conditions, OFZ orally administered to naturally parasitized piglets at a single dose of 30 mg/kg was safe and highly efficacious (100%) against adult stages of A. suum, Oesophagostomum spp., T. suis and Metastrongylus spp.  相似文献   

19.
The objective of this study was to develop and evaluate new baits for the oral delivery of vaccine preparations to 2–4 month-old wild boar piglets. Baits were prepared using a matrix composed of wild boar feed, wheat flour, paraffin, sacarose and cinnamon-truffle powder attractant with polyethylene capsules dipped into the matrix to introduce vaccine formulation. Physical stability studies demonstrated that baits were stable for at least three days at temperatures as high as 42 °C. Recombinant Escherichia coli expressing the membrane-displayed BM95-MSP1a fusion protein were used to test bacterial viability in the baits and the antibody response in orally immunized wild boar. The E. coli viability was not significantly affected after bait incubation at 25 and 37 °C for 96 h. Bait acceptance studies using artificial feeders in the field showed that baits were accepted by 2–3 month-old animals, the preferred age for vaccination. Orally immunized wild boar piglets excreted recombinant E. coli in the feces and developed antibody titers to recombinant BM95-MSP1a protein, thus confirming that vaccine composition was released and reached the wild boar gastrointestinal track. The results of these experiments support the use of these baits for oral delivery of vaccine formulations to 2–4 month-old wild boar piglets.  相似文献   

20.
AIMS: To determine factors that may influence the efficacy of an oral pelleted vaccine containing Mycobacterium bovis bacille Calmette-Guérin (BCG) to induce protection of brushtail possums against tuberculosis. To determine the duration of protective immunity following oral administration of BCG.

METHODS: In Study 1, a group of possums (n=7) was immunised by feeding 10 pellets containing dead Pasteur BCG, followed 15 weeks later with a single pellet of live Pasteur BCG. At that time, four other groups of possums (n=7 per group) were given a single pellet of live Pasteur BCG orally, a single pellet of live Danish BCG orally, 10 pellets of live Pasteur BCG orally, or a subcutaneous injection of live Pasteur BCG. For the oral pelleted vaccines, BCG was formulated into a lipid matrix, and each pellet contained approximately 107 colony forming units (cfu) of BCG, while the vaccine injected subcutaneously contained 106 cfu of BCG. A sixth, non-vaccinated, group (n=7) served as a control. All possums were challenged by the aerosol route with a low dose of virulent M. bovis 7 weeks after vaccination, and killed 7–8 weeks after challenge. Protection against challenge with M. bovis was assessed from pathological and bacteriological findings.

In Study 2, lipid-formulated live Danish BCG was administered orally to three groups of possums (10–11 per group), and these possums were challenged with virulent M. bovis 8, 29 or 54 weeks later. The possums were killed 7 weeks after challenge, to assess protection in comparison to a non-vaccinated group.

RESULTS: The results from Study 1 showed that vaccine efficacy was not adversely affected by feeding dead BCG prior to live BCG. Feeding 10 vaccine pellets induced a level of protection similar to feeding a single pellet. Protection was similar when feeding possums a single pellet containing the Pasteur or Danish strains of BCG. All vaccinated groups had significantly reduced pathological changes or bacterial counts when compared to the non-vaccinated group. In Study 2, oral administration of Danish BCG induced protection against challenge with M. bovis, which persisted for at least 54 weeks after vaccination. Some protection was observed in possums challenged 54 weeks after vaccination, but this protection was significantly less than that observed in groups vaccinated 29 or 8 weeks prior to challenge. There was a strong relationship between the proportion of animals producing positive lymphocyte proliferation responses to M. bovis antigens and protection against challenge with M. bovis.

CONCLUSIONS: Factors considered potentially capable of interfering with vaccination, including feeding dead BCG to possums prior to feeding live BCG, feeding multiple doses of BCG at one time, and changing strains of BCG, were shown not to interfere with the acquisition of protective immune responses in possums. Protection against tuberculosis was undiminished up to 29 weeks after vaccination with BCG administered orally. It is concluded that vaccination of possums by feeding pellets containing BCG is a robust and efficient approach to enhance the resistance of these animals to tuberculosis.  相似文献   

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