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1.
OBJECTIVE: To evaluate the efficacy of an orally administered vaccine of Mycoplasma hyopneumoniae that was prepared by spray drying or solvent evaporation. ANIMALS: Thirty 6-week-old, crossbred, specific-pathogen-free (SPF) pigs. PROCEDURE: Pigs were randomly allocated into 5 groups and housed in an SPF facility. Pigs in 2 groups (groups AQ and CAP) were fed M hyopneumoniae enteric-coated vaccine on days 0, 10, and 20. A third group (group IM) received an IM injection of M hyopneumoniae vaccine with aluminium hydroxide as an adjuvant on days 0, 10, and 20. The last 2 groups (non-vaccinated-challenged [NV-C] and nonchallenged [NC]) were fed a sham treatment. All 24 pigs in groups AQ, CAFP IM, and NV-C were challenge exposed with 5 ml of a 10% pneumonic lung suspension administered on day 40 via intubation of the trachea. All pigs were slaughtered and the lungs removed and examined for lesions on day 68. RESULTS: In vitro studies indicated that these 2 microencapsulation techniques formed an effective shell and protected mycoplasmal antigen from gastric acid. Results of inoculation and challenge tests indicated that microencapsulated M hyopneumoniae were sufficiently potent to induce an immune response and provide good protection. CONCLUSIONS AND CLINICAL RELEVANCE: Orally administered microencapsulated M hyopneumoniae vaccines induced an immune response and reduced the severity of lung lesions in challenge-exposed pigs. Results suggest that this novel method can be applied to other antigens, because the spray-drying process yielded an orally administered M hyopneumoniae vaccine that induced a good immune response.  相似文献   

2.
The effect of dextran sulfate (DS), known to be cytotoxic to macrophages, on the cell-mediated and humoral immune response to nonviable Mycoplasma hyopneumoniae in pigs was investigated. The cell-mediated immune response was determined by means of lymphocyte transformation a test, using uptake of [3H]thymidine in a microculture system and the humoral immune response by means of a microplate complement-fixation test. Peripheral blood lymphocytes from pigs vaccinated with nonviable M hyopneumoniae and DS incorporated substantially more [3H]thymidine than did those from pigs given Mycoplasma or DS alone. The transformation of lymphocytes from M hyopneumoniae-DS vaccinated pigs was enhanced when M hyopneumoniae cells used in the assay system were heated at 60 C for 30 minutes. Similarly prepared M flocculare and M hyorhinis cells also stimulated lymphocytes from M hyopneumoniae-DS vaccinated pigs, but not nearly as great as when M hyopneumoniae cells were used. The humoral antibody response and the cell-mediated immune response to nonviable M hyopneumoniae was markedly enhanced by DS. Pigs were vaccinated with nonviable M hyopneumoniae and/or DS 4 times and challenge exposed intratracheally with viable M hyopneumoniae. Pigs vaccinated with M hyopneumoniae and DS had less severe pneumonia than did nonvaccinated pigs.  相似文献   

3.
Objective To investigate the protective efficacy of a pool of denatured membrane protein antigens of Mycoplasma hyopneumoniae (J strain) in the molecular size range 70 to 85 kDa (F3 antigen) in combination with adjuvants for pigs challenged with M hyopneumoniae .
Design A vaccine efficacy experiment with assessment of serum and respiratory tract antibody responses.
Procedure F3 antigens were emulsified with five different adjuvants. To groups of three pigs per vaccine, four vaccines were given by intramuscular injection, and two vaccines, including one of those given intramuscularly, were given by intraperitoneal injection.
Results Compared to six unvaccinated pigs, animals vaccinated with F3 antigen displayed significantly reduced pneumonia (54% reduction in mean lung score) following experimental challenge. Analysis of post-vaccination, pre-challenge IgG and IgA ELISA antibody absorbances in serum and respiratory tract washings revealed no correlation with lung score. Six weeks after challenge, pigs previously vaccinated intramuscularly mostly demonstrated greater IgG and IgA responses in respiratory tract washings, and greater IgG serum antibody responses, than those vaccinated by intraperitoneal injection.
Conclusion Pigs vaccinated with M hyopneumoniae antigens in the molecular size range of 70 to 85 kDa showed a significant reduction in lung lesions compared with unvaccinated control animals after experimental challenge. IgG and IgA antibody concentrations in serum and respiratory tract washings after vaccination do not provide a useful prognostic indicator of protection from enzootic pneumonia.  相似文献   

4.
A field study was conducted in Brazil to evaluate the efficacy of single vaccination of pigs with two bacterins to prevent Mycoplasma hyopneumoniae lung lesions. The first (T1) treatment group (174 pigs) was injected with 2 mL of saline solution; group T2 (177 pigs) with 2 mL of bacterin A, and group T3 (174 pigs) with 2 mL of bacterin B. On days-on-test (DOT) 0, 35, 66, 97 and 125, blood samples and tonsil swabs were collected from selected pigs for antibody determination (indirect ELISA) and PCR assay for the presence of M. hyopneumoniae. Pigs were slaughtered on DOT 126-129 and lung lesions were scored blindly. Bacterin A vaccinated pigs had significantly (P < or = 0.05) lower lung lesion scores (0.2%) than bacterin B (0.4%) or saline-treated pigs (1.2%); there was also a significantly lower (P < or = 0.05) number of pigs with lung lesions (27.1%), than bacterin B (38.2%) or saline-treated (55.4%) pigs. The two vaccines had similar (P>0.05) results in terms of mean weight gain, average daily weight gain, feed efficiency, frequency of PCR positives, and there was similar antibody conversion (ELISA). It was concluded that although the productivity parameters and antibody conversions were similar, bacterin A was more effective in preventing and reducing the severity of lung lesions than bacterin B.  相似文献   

5.
A killed Mycoplasma hyopneumoniae vaccine was evaluated in a single swine herd in which the farrowing barn and weaner rooms were on one Mycoplasma-free farm, while the growing and finishing barn was on a separate farm on which Mycoplasma was present. The study was carried out in a cohort of pigs born in a 12-week period. Pigs born in 6 of the 12 wk were vaccinated and the rest were left as controls. The vaccine was administered twice at approximately 3 and 6 wk of age. Carcass characteristics, lung lesions, and growth rates were recorded on 893, 390, and 220 pigs, respectively. The vaccine reduced the prevalence of pneumonic lesions in slaughter hogs from 69% to 36% (P < 0.001). It also appeared to reduce the prevalence of pleuritis from 20% to 13%, but the difference was only statistically significant at P = 0.07. The vaccine had no effects on carcass characteristics except that carcasses of vaccinated pigs were, on average, 1 kg heavier than those of nonvaccinated pigs, and a smaller percentage of vaccinated pigs were shipped "light" (carcass weight < 70 kg). Two methods were used to estimate the effect of the vaccine on growth rates (as measured by days to 80 kg carcass weight) resulting in estimates of 11 and 2 d reduction attributable to vaccination, respectively. The latter estimate was probably an underestimate for reasons discussed in the paper.  相似文献   

6.
Pigs in three specialized fattening herds were studied with respect to the effect of infection with Mycoplasma hyopneumoniae on weight gain. Individual pigs were weighed four times at 4-week intervals during the fattening period and their daily weight gain over the rearing period was calculated. A blood sample was collected on each weighing occasion and analysed for the presence of antibodies to M. hyopneumoniae. The lungs of the principals were inspected at slaughter and the extent of pneumonic lesions was registered by a specially developed technique that has been proven to warrant a high degree of repeatability. No serum antibodies to M. hyopneumoniae were detected in one of the herds, and no pneumonic lesions were recorded at slaughter in that herd. In the other two herds, the prevalence of pigs with serum antibodies to M. hyopneumoniae increased from 6 to 54% and from 31 to 81%, respectively, during the fattening period. The prevalence of pneumonic lesions at slaughter in these herds was higher the later the pigs seroconverted. On the other hand, the extension of the lung lesions tended to be higher among pigs that seroconverted early during the rearing period. Infections with M. hyopneumoniae acquired early during the rearing, presumably strengthened by secondary infections and environmental errors, was found to decrease the daily weight gain of the pigs. However, even non-complicated M. hyopneumoniae infections acquired late in the fattening period were associated with reduced daily weight gain. That growth reduction was estimated to be at least 60 g (about 6%) after adjusting for herd, pen, initial weight and sex.  相似文献   

7.
A Mycoplasma hyopneumoniae vaccine (Respisure, Pfizer AH) was tested for its effects on antibody formation, daily weight gain (DWG) in different growing periods, lung lesions and quality of meat (chemical composition, physicochemical properties and fatty acid composition). Two groups of conventional piglets were used for the investigation. One group of 11 females and 11 males was vaccinated intramuscularly at the age of 1 and 3 weeks. The other group of 22 piglets was left nonvaccinated as control. The results showed that antibodies against M. hyopneumoniae in the vaccinated group had been formed 14 days after the second vaccination and remained present till the end of the study at 147 days of age. In the nonvaccinated group, seroconversion started at 49 days of age and by the end of the study 10 out of 22 pigs had become seropositive. Vaccinated pigs achieved significantly higher daily weight gain (+30 g) and finishing body weight (+6.04 kg) than the nonvaccinated animals. In addition, the vaccinated pigs showed lesions involving 3.27% of the lung surface in average, while in the nonvaccinated pigs 9.04% of the lung surface was affected. Investigation of meat quality showed that the longissimus dorsi muscle of vaccinated pigs contained significantly lower percentage of fat (-0.63%) and its tryptophan/hydroxyproline ratio was significantly lower (-23.57) in comparison with the control animals. In addition, some other parameters also showed a favourable tendency, e.g. lean meat percentage was 0.91% higher, the protein content of the longissimus dorsi muscle was 0.35% higher, its water-binding capacity was also higher by 0.78%, its monounsaturated fatty acid concentration was 2.97% lower, while its polyunsaturated fatty acid content was 1.65% higher in the vaccinated pigs than in the nonvaccinated animals.  相似文献   

8.
Oral microencapsulated Mycoplasma hyopneumoniae vaccines were tested for their ability to prevent mycoplasmal pneumonia in pigs. Eighteen four-week-old specific pathogen free pigs were divided into six groups of three. Each pig of groups 1 to 4 was inoculated intramuscularly with formalin-inactivated M hyopneumoniae in adjuvant and boosted orally 14 days later with four different microencapsulated vaccine microspheres. Group 5 was used as a positive control. All 15 pigs of groups 1 to 5 were challenged at 28 days after the first vaccination by an intratracheal inoculation of pneumonic lung suspension. The three pigs of group 6 were used as a negative control. All four vaccinated groups showed some protection when challenged, but the protection was more solid in pigs boosted with vaccine D (group 4) which contained less porcine serum in the microsphere. The study indicates that oral vaccination with M hyopneumoniae could play a role in prevention and eradication of mycoplasmal pneumonia in the pig.  相似文献   

9.
The systemic and respiratory local immune response induced by the intradermal administration of a commercial inactivated Mycoplasma hyopneumoniae whole-cell vaccine (Porcilis® MHYO ID ONCE – MSD AH) in comparison with two commercial vaccines administered via the intramuscular route and a negative control (adjuvant only) was investigated. Forty conventional M. hyopneumoniae-free pigs were randomly assigned to four groups (ten animals each): Group A = intradermal administration of the test vaccine by using the needle-less IDAL® vaccinator at a dose of 0.2 ml; Group B = intramuscular administration of a commercially available vaccine (vaccine B); Group C = intramuscular administration of the adjuvant only (2 ml of X-solve adjuvant); Group D = intramuscular administration of a commercially available vaccine (vaccine D). Pigs were vaccinated at 28 days of age. Blood and bronchoalveolar lavage (BAL) fluid samples were collected at vaccination (blood only), 4 and 8 weeks post-vaccination. Serum and BAL fluid were tested for the presence of antibodies by ELISA test. Peripheral blood monomorphonuclear cells (PBMC) were isolated to quantify the number of IFN-γ secreting cells by ELISpot. Moreover, cytokine gene expression from the BAL fluid was performed. Total antibodies against M. hyopneumoniae and specific IgG were detected in serum of intradermally and intramuscularly (vaccine B only) vaccinated pigs at 4 and 8 weeks post-vaccination. M. hyopneumoniae specific IgA were detected in BAL fluid from vaccinated animals (Groups A and B) but not from controls and animals vaccinated with the bacterin D (p < 0.05). Significantly higher gene expression of IL-10 was observed in the BAL fluid at week 8 post-vaccination in the intradermally vaccinated pigs (p < 0.05). The results support that the intradermal administration of an adjuvanted bacterin induces both systemic and mucosal immune responses. Moreover, the intramuscularly administered commercial vaccines each had a different ability to stimulate the immune response both systemically and locally.  相似文献   

10.
We compared the efficacy of 3 commercial vaccines against swine influenza A virus (SIV) and an experimental homologous vaccine in young pigs that were subsequently challenged with a variant H3N2 SIV, A/Swine/Colorado/00294/2004, selected from a repository of serologically and genetically characterized H3N2 SIV isolates obtained from recent cases of swine respiratory disease. The experimental vaccine was prepared from the challenge virus. Four groups of 8 pigs each were vaccinated intramuscularly at both 4 and 6 wk of age with commercial or homologous vaccine. Two weeks after the 2nd vaccination, those 32 pigs and 8 nonvaccinated pigs were inoculated with the challenge virus by the deep intranasal route. Another 4 pigs served as nonvaccinated, nonchallenged controls. The serum antibody responses differed markedly between groups. After the 1st vaccination, the recipients of the homologous vaccine had hemagglutination inhibition (HI) titers of 1:640 to 1:2560 against the challenge (homologous) virus. In contrast, even after 2nd vaccination, the commercial-vaccine recipients had low titers or no detectable antibody against the challenge (heterologous) virus. After the 2nd vaccination, all the groups had high titers of antibody to the reference H3N2 virus A/Swine/Texas/4199-2/98. Vaccination reduced clinical signs and lung lesion scores; however, virus was isolated 1 to 5 d after challenge from the nasal swabs of most of the pigs vaccinated with a commercial product but from none of the pigs vaccinated with the experimental product. The efficacy of the commercial vaccines may need to be improved to provide sufficient protection against emerging H3N2 variants.  相似文献   

11.
The interaction between Mycoplasma hyopneumoniae and Pasteurella multocida in experimental pneumonia was investigated in conventional pigs. The experimental animals were 49 days old when inoculated with M. hyopneumoniae; they were inoculated with P. multocida after 23 days, and killed 13 days later. In pigs inoculated only with P. multocida, clinical signs and lung lesions were not observed, and the agent was not recovered. Pigs inoculated with M. hyopneumoniae developed fever, moderate cough and dyspnea which tended to disappear, and small proliferative lung lesions from which M. hyopneumoniae was isolated. Pigs inoculated with both agents had higher fever, severe cough and dyspnea which tended to aggravate, and extensive exudative lung lesions from which organisms were isolated. All animals had similar growth rates, but the group infected with both agents consumed 60% more food. Therefore, M. hyopneumoniae causes mild pneumonia, whereas P. multocida is not pathogenic alone but aggravates the pneumonia initiated by M. hyopneumoniae.  相似文献   

12.
The efficacy of Mycoplasma hyopneumoniae oral vaccine was investigated in microsphere dosage form. A co-spray drying process was used to apply an encapsulating material, Eudragit L30 D-55, to microspheres containing Mycoplasma hyopneumoniae antigens. The microspheres were generally effective (>93%) with protein release at pH 7.4, but almost none were released at pH 1.2, for 3 hr in an in vitro dissolution test. An SPF-swine model was used to evaluate the effectiveness of the microspheres as an oral vaccine, and the related immune responses. The serum's systemic IgG against M. hyopneumoniae was evoked by ELISA analysis, after a 2nd immunization of all pigs. The vaccinated groups' mean lesion score was significantly lower after the Mycoplasma hyopneumoniae challenge than that of the nonvaccinated/challenged groups (P<0.05). This study strongly suggests that the oral microspheres vaccine prepared by a co-spray drying method can provide effective protection against M. hyopneumoniae infection in pigs.  相似文献   

13.
The 6-chloro analogue of norfloxacin (compound A) administered continuously in the feed at 400 ppm for 21 days markedly reduced the extent and activity of pneumonic lesions in pigs with pneumonia induced experimentally with an homogenate of pneumonic lung and broth cultures of Mycoplasma hyopneumoniae. Norfloxacin at 100 ppm or compound A at 200 ppm in the feed did not reduce the extent of lung lesions, although half the pigs treated with norfloxacin had lesions which appeared histologically to be healing. M hyopneumoniae was detected either by culture or immunofluorescence in the lungs of 60 per cent of the pigs treated with compound A at 400 ppm compared with all the pigs in the other groups. These results were related to the amount of drug in the lungs and body fluids during therapy. Only compound A at 400 ppm produced concentrations in the lungs and bronchial secretions exceeding the minimum inhibitory concentration against M hyopneumoniae. Mycoplasmacidal concentrations were not reached either in the lungs or bronchial secretions which might account partly for the frequent detection of M hyopneumoniae in the lungs after treatment. Drug resistance did not appear to be responsible for the persistence of M hyopneumoniae in vivo since the M hyopneumoniae isolates from the pigs after therapy were sensitive in vitro to both quinolones. As daily weight gain and feed-conversion efficiency improved in all groups of treated pigs compared with the controls, these effects were probably unrelated to the antimycoplasmal activities of the two quinolones.  相似文献   

14.
The objective of this study was to evaluate the efficacy of a new Mycoplasma hyopneumoniae bacterin against a Korean M. hyopneumoniae challenge under experimental conditions. Fifteen pigs were allocated randomly into 3 groups (5 pigs per group) that were designated in 1 of 3 ways: vaccinated-challenged, unvaccinated-challenged, or unvaccinated-unchallenged. The pigs in the vaccinated-challenged group were immunized with an M. hyopneumoniae whole-cell bacterin at a 1.0 mL dose-level at 21 d old. At 42 d old (0 d post-challenge), the pigs in the vaccinated-challenged and unvaccinated-challenged groups were inoculated intranasally with a strain of Korean M. hyopneumoniae. Vaccinated-challenged pigs elicited a strong cell-mediated immunity as measured by M. hyopneumoniae-specific interferon-γ secreting cells when compared with unvaccinated-challenged pigs. Vaccination of pigs with this new M. hyopneumoniae bacterin reduced nasal shedding and lung lesions. The evaluated vaccine was therefore considered effective in controlling M. hyopneumoniae infection.  相似文献   

15.
The objective of this study was to compare the efficacy and safety of single-strain and multi-strain vaccines for the prevention of the respiratory facet of porcine reproductive and respiratory syndrome. The study comprised six groups of pigs (A through F, eight pigs per group). At the beginning of the study (Day 0) Groups C and D were vaccinated with a single-strain vaccine, and Groups E and F were vaccinated with a multi-strain vaccine. The multi-strain vaccine contained five attenuated strains of PRRSV including the strain used as the single-strain vaccine. On Day 28 Groups B (nonvaccinated/challenged control), D, and F were challenged with a highly virulent field strain of PRRSV that was unrelated to any of the strains used for vaccination. Group A was kept as a nonvaccinated/nonchallenged control. On Day 42 all pigs were necropsied. Their lungs and lymph nodes were examined for virus-induced changes. Serum samples obtained at weekly intervals during the study and lung lavage fluids obtained at necropsy were tested for the presence and titer of PRRSV. Serum samples were also tested for antibody. The presence and severity of clinical signs and lesions were the primary means by which vaccine efficacy and safety were evaluated. Both vaccines provided a high level of protective immunity to challenge. However, appreciable lymph node enlargement in pigs vaccinated with multi-strain vaccine, with or without subsequent challenge, raised a question as to its safety. Collectively these results indicate that both single-strain and multi-strain attenuated PRRSV vaccines can be effective immunogens, but additional studies in regard to safety are needed before multi-strain vaccines can be recommended for routine field use.  相似文献   

16.
The nasal and serum antibody response of two groups of pigs, vaccinated with adjuvant containing formalinized or sonicated Bordetella bronchiseptica bacterins was compared with the response of a nonvaccinated group. The tube agglutination test was used to determine agglutinin titers. Following vaccination, all pigs were challenged intranasally with the vaccine strain of Bordetella, after which the nasal Bordetella flora of vaccinated and nonvaccinated pigs was investigated. Sera and nasal secretions from both vaccinated groups exhibited markedly higher agglutinin titers than the control group and serum titers were higher than those in nasal secretions. No differences in agglutinating antibody response were evident between the two vaccines. Serum antibody titers exceeded nasal titers and persisted over a longer period of time. Systemic vaccination resulted in an increased nasal clearance of the vaccine strain by the groups of pigs vaccinated with sonicated or formalined bacterin, whereas no such clearance was evident in the nonvaccinated control group.  相似文献   

17.
应用本实验室构建的嵌合型猪圆环病毒（PCV1—2）及真核表达质粒pcDNA3．1／V5-His-ORF2作为免疫原免疫母源抗体ELISA效价在0．07～0．60不等的商品猪,9头猪随机分为4组,1组（3头）肌肉注射免疫10^3.5 TCID50的PCV1-2／头,2组（2头）肌肉注射真核表达质粒200μg／头,3组（2头）肌肉注射空载体（pcDNA3．1）200μg／头,4组（2头）不免疫作为攻毒对照组。于免疫后42d,PCV1—2组及真核表达质粒组产生了PCV2抗体。免疫后42d所有组攻毒PCV2和PRRSV,剂量分别为2×10^4.5 TCID50／头和10^6 TCID50／头。攻毒后21d,攻毒对照组猪淋巴结比免疫组显著肿大,免疫组猪血清、淋巴结中PCV2病毒栽量低于对照组,攻毒对照组猪淋巴结中PCV2抗原含量高于免疫组。这些结果表明,嵌合型PCV1-2及真核表达质粒肌肉注射免疫商品猪后,对PCV2感染能产生保护性免疫应答,有可能成为候选疫苗。  相似文献   

18.
The level of antigen-specific interferon-gamma (IFN-gamma) production can be used as an indicator of cellular immunity. In this study, we investigated the role of cellular immune response in protection against classical swine fever virus (CSFV). Pigs were vaccinated once with CSFV vaccine and challenged 6 days post-vaccination (dpv). Vaccinated animals had significantly higher CSFV-specific IFN-gamma secreting cells than the unvaccinated pigs (p<0.05) at the time of challenge and were protected against CSFV infection, whereas the control pigs died within 14 days post-infection (dpi). In the second experiment, pigs were vaccinated once with either CSFV vaccine or CSFV vaccine combined with Aujeszky's disease (AD) vaccine and challenged at 140 dpv. All vaccinated pigs developed both CSFV-specific, cellular and antibody responses and were protected against CSFV infection. However, differences in cellular, but not antibody, responses were observed in the two vaccinated groups. The group vaccinated with CSFV vaccine developed a significantly higher number of CSFV-specific, IFN-gamma secreting cells (p<0.05), exhibited a shorter fever period and less pathological changes, when compared with the group vaccinated with the combined vaccine. The kinetics of IFN-gamma production, following challenge in the two vaccinated groups, were also different. Taken together, our results indicated that CSFV-specific, IFN-gamma production could be detected early after antigen exposure and correlated with protection against CSFV challenge. Our findings highlight the role of cellular immune responses in porcine anti-viral immunity.  相似文献   

19.
Rats and pigs were vaccinated against Trichinella spiralis spiralis either by feeding infective larvae of the subspecies, Trichinella spiralis nativa in musculature or by gavage. The number of larvae established in the musculature of vaccinated nonchallenged and vaccinated challenged rats and pigs were negligible and statistically comparable, while highly significant infections were established in the nonvaccinated challenged rats and pigs. High vaccination doses of T. spiralis nativa gave virtually complete protection to challenge with T. spiralis spiralis in pigs. The results of one trial in rats with a lower vaccination dose of larvae suggest that there is a minimal vaccination dose of larvae required to elicit marked resistance to challenge. The low numbers of muscle larvae established due to the high vaccination doses of larvae confirm the low infectivity of the subspecies, T. spiralis nativa in rats and pigs.  相似文献   

20.
The efficacy of a muramidase-released protein (MRP) and extracellular factor (EF) vaccine in preventing infection and disease in pigs challenged either with a homologous or a heterologous Streptococcus suis serotype 2 strain (MRP+EF+) was compared with the efficacy of a vaccine containing formalin-killed bacterin of S. suis serotype 2 (MRP+EF+). The enhancement of the immune response by different adjuvants (a water-in-oil emulsion [WO] and an aluminium hydroxide-based adjuvant [AH]) and their side effects were also studied. The MRP and EF were purified by affinity chromatography. Pigs were vaccinated twice at three weeks and six weeks of age and challenged intravenously with virulent S. suis serotype 2 strains (MRP+EF+) at eight weeks of age. At challenge, the pigs vaccinated with MRP+EF/WO had high anti-MRP and anti-EF titres and were protected as effectively as pigs vaccinated with WO-formulated vaccines with bacterin. Eight of the nine pigs survived the challenge and almost no clinical signs of disease were observed. The titres obtained with the MRP+EF/AH vaccine were low and only two of the five pigs were protected. Pigs vaccinated with either MRP or EF were less well protected; three of the four pigs died after challenge but the clinical signs of disease were significantly less severe than those observed in the placebo-vaccinated pigs. The protective capacity of the bacterin/AH vaccine was very low, and the mortality among these pigs was as high as in the placebo-vaccinated pigs (80 per cent). Postmortem histological examination revealed meningitis, polyserositis and arthritis in the clinically affected pigs. The results demonstrate that a subunit vaccine containing both MRP and EF, formulated with the WO adjuvant, protected pigs against challenge with virulent S. suis type 2 strains.  相似文献   

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