Protection of rabbits against experimental pasteurellosis by vaccination with a potassium thiocyanate extract of Pasteurella multocida.

Antigens were extracted from a virulent isolate of Pasteurella multocida (serotype 3, 12, 15:D) with potassium thiocyanate, and a vaccine was prepared. Pasteurella-free rabbits were vaccinated intranasally and intraconjuctivally twice with a 2-week interval and challenged intranasally with the homologous P. multocida serotype 2 weeks after the second vaccination. The vaccinated rabbits produced serum immunoglobulin G and nasal mucosal immunoglobulin A against P. multocida. The vaccine protected the challenged rabbits against clinical disease and death; however, otitis media was not prevented, and microscopic inflammatory lesions were occasionally noted in the lungs and nasal turbinates. In contrast, nonvaccinated, challenged rabbits became febrile, dyspnic, depressed, and anorectic, and five of six died within 4 days of challenge with severe lesions including pneumonia, pleuritis, otitis media, and bacteremia. The vaccine prevented death and colonization of challenge organisms in the blood and lung, but did not prevent colonization of the middle ear. The vaccine alone did not cause clinical disease or gross lesions, but did produce microscopic pulmonary inflammatory lesions.     

A potassium thiocyanate extract vaccine prepared from Pasteurella multocida 3:A protects rabbits against homologous challenge.

Potassium thiocyanate extracts of a virulent Pasteurella multocida 3:A rabbit isolate were prepared and used as a vaccine in rabbits. The extract contained protein, carbohydrate, hyaluronic acid, lipopolysaccharide, DNA, and RNA. The protein and lipopolysaccharide profiles of the extract were similar to those of the P. multocida cell membrane. Rabbits were vaccinated intranasally (i.n.) or intramuscularly (i.m.) four times at 1- or 3-week intervals and challenged i.n. with the homologous P. multocida 2 weeks after the last vaccination. Rabbits vaccinated with the extract by the i.n. route developed persisting serum immunoglobulin G (IgG) and nasal IgA antibodies, whereas rabbits immunized by the i.m. route produced persisting serum IgG and transient nasal IgA antibodies. The extract prevents the death of rabbits which were vaccinated by either route and challenged. Vaccination by the i.n. route in rabbits reduced the numbers of virulent P. multocida in nasal cavities and lungs and the prevalence and severity of rhinitis and pneumonia. These i.n.-vaccinated rabbits were also resistant to virulent P. multocida colonization in liver, spleen, uterus, and tympanic bullae. Similarly, i.m. vaccination in rabbits resulted in a reduction in the severity of rhinitis; the numbers of virulent P. multocida in lungs; and the prevalence of colonization in liver, spleen, uterus, and tympanic bullae. Vaccination by the i.n. route was superior to that by the i.m. route in that there was a significant reduction in the severity of pneumonia and numbers of virulent P. multocida in nasal cavities and lungs. Rabbits vaccinated with the extract without challenge showed no lesions.     

Protection of rabbits against experimental pasteurellosis by a streptomycin-dependent Pasteurella multocida serotype 3:A live mutant vaccine.

Pasteurella multocida (serotype 3:A) was isolated from a rabbit with clinical signs of suppurative rhinitis. This P. multocida strain was mutagenized with N-methyl-N'-nitro-N-nitrosoguanidine to obtain a genetically stable streptomycin-dependent mutant, from which a life vaccine was prepared. Pasteurella-free rabbits were inoculated intranasally three times at weekly intervals and challenged intranasally with a virulent serotype 3:A rabbit P. multocida isolate 2 weeks after the third vaccination. The rabbits were killed 2 to 3 weeks later. The vaccine did not cause clinical disease, death, or gross or microscopic lesions. Furthermore, the vaccine protected the challenge rabbits from developing clinical disease, death, and gross lesions. However, mild focal lung lesions were noted in several of the vaccinated-challenged animals. In contrast, nonvaccinated-challenged rabbits developed pyrexia and anorexia. Furthermore, three of four of these rabbits died with severe gross lesions including pyothorax, suppurative pericarditis, and fibrinopurulent pneumonia. Microscopically, the four nonvaccinated rabbits had moderate to severe suppurative pneumonia and mild to moderate suppurative rhinitis, and two had mild tympanitis. The mutant vaccine did not appear to colonize the nasal cavities. The vaccine prevented the colonization of the virulent challenge organism in lungs, liver, spleen, genital tracts, and blood, but not the nasal cavities.     

A monoclonal antibody against a Pasteurella multocida outer membrane protein protects rabbits and mice against pasteurellosis.

Monoclonal antibodies (MAbs) directed against the 37.5-kDa outer membrane protein were produced by fusing myeloma cells with spleen cells obtained from mice immunized with a pathogenic strain of Pasteurella multocida isolated from a rabbit. Desirable MAbs were selected by enzyme-linked immunosorbent assay, whole-cell radioimmunoprecipitation (WC-RIP), and Western blot (immunoblot) analysis. WC-RIP and Western blot analyses, using MAb 1608 adsorbed with intact P. multocida cells and the eluted MAb, demonstrated that the antigen recognized by this MAb is exposed on the cell surface, is antibody accessible, and has an estimated molecular mass of 37.5 kDa. Treatment of outer membrane vesicles of P. multocida with proteinase K totally abrogated the MAb 1608 activity, indicating that this MAb binds to a protein antigenic determinant. Furthermore, MAb 1608 was nonreactive to purified lipopolysaccharide in Western blot analysis. Passive transfer studies showed that nine rabbits inoculated intranasally with MAb 1608 and homologously challenged intranasally had significantly reduced mortality, severity of pneumonia, prevalence of P. multocida colonization in nonrespiratory organs, and numbers of P. multocida in nasal cavities compared with the controls. Furthermore, the number of P. multocida in lungs was reduced 84,750-fold. Similarly, passive transfer experiments indicated that MAb 1608 protected mice against homologous and heterologous challenges with P. multocida strains bearing the antigenic determinant recognized by MAb 1608. However, no protection was afforded by MAb 1608 when mice were challenged with a P. multocida strain lacking the antigenic determinant recognized by MAb 1608. This study establishes that the 37.5-kDa outer membrane protein is the target for a protective MAb.     

Hyperimmune serum from rabbits immunized with potassium thiocyanate extract of Pasteurella multocida protects against homologous challenge.

Hyperimmune rabbit sera directed to the KSCN extract of 3:A Pasteurella multocida were characterized by enzyme-linked immunosorbent assay (ELISA), presolubilized cell radioimmunoprecipitation, and immunoblotting analysis. The results showed that the hyperimmune serum had a very high titer of immunoglobulin G ELISA antibody and a negligible immunoglobulin A ELISA antibody, precipitated 10 different outer membrane protein antigens by radioimmunoprecipitation, and reacted to 10 different membrane vesicle antigens of P. multocida by immunoblotting analysis. The hyperimmune rabbit sera were also evaluated for protective efficacy against experimental rabbit pasteurellosis by homologous challenge. Thirty-six rabbits were divided into four groups. Group 1, 2, and 3 rabbits were inoculated intranasally with hyperimmune rabbit serum, phosphate-buffered saline, or normal rabbit serum, respectively, at 24 h prior to and 24, 48, and 72 h after intranasal challenge with the virulent homologous P. multocida strain. Group 4 rabbits were inoculated with normal rabbit serum without challenge. Necropsies of surviving rabbits were performed 2 weeks postinfection. The mortality rates for groups 1 through 4 were 25% (3 of 12), 67% (8 of 12), 75% (6 of 8), and 0% (0 of 4), respectively. The prevalence and severity of pneumonia were significantly lower in the hyperimmune serum-treated rabbits. The prevalence of P. multocida colonization in lungs was significantly lower in group 1 rabbits, and the geometric mean CFU of P. multocida in lungs was 59,166-fold less in group 1 rabbits than in group 3 rabbits. The geometric mean CFU of P. multocida in nasal cavities of group 1 rabbits was significantly lower than that of group 3 rabbits. All challenged rabbits (groups 1,2, and 3) had elevated nasal immunoglobulin A and pulmonary (lung lavage) immunoglobulin A antibody levels at necropsy (day 14 postinfection). Similarly, all challenged rabbits had elevated levels of ELISA immunoglobulin G antibody in serum at day 14 but not at day 7 postinfection, indicating that rabbits receiving hyperimmune serum can mount a specific humoral immune response against the homologous challenge P. multocida organisms. We concluded that hyperimmune serum directed to the KSCN extract of 3:A P. multocida provides significant protection against homologous challenge in rabbits.     

Antibodies to outer membrane proteins but not to lipopolysaccharide inhibit pulmonary proliferation of Pasteurella multocida in mice.

The role of rabbit antibodies against Pasteurella multocida outer membrane proteins and lipopolysaccharides (LPS) in resistance remains unknown. Pooled immune sera against P. multocida outer membranes were prepared from specific-pathogen-free rabbits immunized with sucrose gradient-purified P. multocida outer membranes. Western immunoblotting showed that purified outer membrane protein antibodies reacted strongly against the outer membrane proteins but not the purified LPS. Affinity-purified LPS antibodies exhibited strong reactivity against purified LPS and very little reactivity against outer membrane vesicles. Mice were inoculated intranasally with immune serum or normal rabbit serum, challenged intranasally with 10(6) CFU of P. multocida, and euthanatized 48 h later to determine the number of P. multocida organisms in the lungs. Mice inoculated with pooled immune serum had a 3,300-fold reduction (P less than 0.001) in the numbers of P. multocida in the lungs as compared with the controls. Similarly, mice inoculated with purified outer membrane protein antibodies had a 201-fold reduction (P less than 0.001) in the numbers of P. multocida. Conversely, mice inoculated with affinity-purified LPS antibodies had a 1.1-fold reduction (P greater than 0.50) in the numbers of P. multocida. These results show that antibodies against the outer membrane proteins but not the LPS are the components of rabbit immune sera which inhibit P. multocida proliferation in mouse lungs.     

Pasteurella multocida and Bordetella bronchiseptica infections in rabbits.

The natural history of infection with Pasteurella multocida and Bordetella bronchiseptica in domestic rabbits was studied prospectively at a commercial rabbitry. At weaning, about 25% of rabbits had nasal infections with P. multocida and 75% had infections with B. bronchiseptica. Infection of weanling rabbits paralleled nasal infections of their dams. The proportion of rabbits with both infections increased with age. At 2 to 4 months old, about 50% of rabbits with P. multocida or P. multocida and B. bronchiseptica infections had upper respiratory disease (URD), whereas rabbits with B. bronchiseptica infection had no disease. In rabbits about 10 months old, 75% with P. multocida or P. multocida and B. bronchiseptica infections had URD, whereas virtually none with B. bronchiseptica infection had disease. Disease of the nares, paranasal sinuses, middle ears, and lungs was associated with P. multocida and not B. bronchiseptica infection. In adult rabbits with nasal P. multocida infection, with or without signs of URD, about 80% had concurrent infection of the paranasal sinuses and middle ears and 20% had infection of the bronchi and lungs. In rabbits without nasal P. multocida infection, 20 to 35% had P. multocida infection of the paranasal sinuses and middle ears. Weanling rabbits with and without P. multocida infection had similar immunoglobulin G (IgG) levels. In rabbits observed prospectively, the only antibody differences between those transiently and persistently infected with P. multocida were a diminished IgA response in nasal lavages and an earlier IgM response in sera of transiently infected rabbits. IgG levels increased with the duration of infection. There was no relationship between immunoglobulin levels and freedom from P. multocida infection.     

Porcine circovirus type 2 infection decreases the efficacy of a modified live porcine reproductive and respiratory syndrome virus vaccine

Porcine reproductive and respiratory syndrome virus (PRRSV)-induced pneumonia is a major problem, and vaccination is used to reduce losses associated with PRRSV. Porcine circovirus type 2 (PCV2) causes lymphoid depletion, and there is concern that this adversely affects the immune response. The objective of this study was to investigate the effect of PCV2 infection on the efficacy of modified live virus (MLV) PRRSV vaccine. Sixty-nine 2-week-old pigs were randomly assigned to one of seven groups of 9 to 10 pigs each. At 6 weeks of age, pigs in groups 4, 5, and 6 were inoculated intranasally with PCV2 ISU-40895. At 8 weeks of age, groups 3, 4, 6, and 7 were vaccinated with a PRRSV MLV vaccine. At 12 weeks of age, groups 2, 3, and 4 were challenged with PRRSV SDSU73. All pigs were necropsied 14 days after PRRSV challenge. PCV2-infected, PRRSV-vaccinated, and PRRSV-challenged pigs had significantly (P < 0.05) more-severe macroscopic lung lesions than did the PRRSV-vaccinated and PRRSV-challenged pigs that were not exposed to PCV2 prior to PRRSV vaccination. Nonvaccinated PRRSV-infected pigs had a significantly (P < 0.001) higher incidence of PRRSV antigen in lungs than did all other groups except the group infected with PCV2 prior to PRRSV vaccination and challenge. The nonvaccinated PRRSV-challenged group and the group challenged with PCV2 prior to PRRSV vaccination and challenge had significantly (P < 0.001) lower average daily weight gain than did the control and the vaccinated groups. This work suggests that PCV2 infection has an adverse effect on the development of protective immunity induced by PRRSV vaccine.     

Identification of immunogenic outer membrane proteins of Pasteurella multocida 3:A in rabbits.

Four groups of protective rabbit immune sera were used to identify Pasteurella multocida outer membrane immunogens by a radioimmunoprecipitation procedure and Western blot (immunoblot) analysis. These are rabbit hyperimmune sera against KSCN extract of P. multocida (group 1) and rabbit immune sera against the KSCN extract of P. multocida (group 2), the outer membrane of P. multocida (group 3), and live P. multocida cells (group 4). Rabbits mounted an antibody response to 18 proteins found in the outer membrane of P. multocida, and the major antibody activities were directed to the 27,000-molecular-weight outer membrane protein (27K protein), as well as the 37.5K, 49.5K, 58.7K, and 64.4K outer membrane proteins. These outer membrane immunogens appear to be exposed on the cell surface and accessible to antibodies, since adsorption of these immune sera with intact P. multocida cells resulted in a significant reduction of antibody activities directed against these proteins, especially the 37.5K protein. Antibodies eluted from immune serum-P. multocida cell complexes were reactive to the 37.5K immunogen, confirming that this protein is exposed on cell surface and accessible to antibodies. Western blot analyses with group 1, 3, and 4 immune sera confirmed that the 27K, 37.5K, 49.5K, 58.7K, and 64.4K proteins are the major outer membrane immunogens of P. multocida in rabbits. Lung lavages of immunized rabbits also contained similar antibody activities directed against several outer membrane proteins, with major activities against the 37.5K and 64.4K proteins.     

Importance of serratia protease in the pathogenesis of experimental Serratia marcescens pneumonia.

The results of studies to evaluate the possible importance of serratia proteases in the development of experimental Serratia marcescens pneumonia revealed the following. (i) Administration of a highly purified serratia protease to the lungs of guinea pigs and mice resulted in extensive pulmonary edema and hemorrhage similar to that observed in animals having an experimentally induced, acute serratia pneumonia. (ii) Guinea pigs subcutaneously vaccinated with the protease developed low levels of antiprotease antibodies and were partially protected against serratia pneumonia, as demonstrated by a significant increase in survival time. Mice intranasally vaccinated with the protease also developed antiprotease antibodies and were protected against serratia pneumonia, as demonstrated by a significant increase in survival time and an increase in the number of survivors. (iii) Serratia protease was detected in lung tissue extracts prepared from the lungs of guinea pigs dying of serratia pneumonia. Our findings support the idea that serratia protease(s) is involved in the pathogenesis of experimental serratia pneumonia.     

Class-specific antibody responses to Mycoplasma pulmonis in sera and lungs of infected and vaccinated mice.

Class-specific antibodies were measured by a solid-phase microradioimmunoassay in the sera and lung washings of mice after intranasal or intravenous inoculation with live Mycoplasma pulmonis and after systemic, intranasal, or combined vaccination with Formalin-inactivated mycoplasmas. After intranasal or intravenous inoculation with live organisms, serum antibodies were first detected in immunoglobulin M (IgM) followed by IgG2, IgG1, and IgA classes, but significant levels of IgA developed only in those mice inoculated intranasally. The appearance of antibodies in lung washings was later than in serum, but again these were predominantly IgG2 and IgG1. After inoculation with killed organisms, serum antibodies were predominantly IgG1, although IgG2, IgM, and, in intranasally vaccinated mice, IgA were also present. Only IgG1 was detected in lung washings from mice vaccinated systemically, but IgA and IgG2 were present in addition in animals vaccinated intranasally. Immunofluorescence studies indicated that some antibody in lung washings from the latter group of animals was produced locally. A comparison of the levels of various class-specific antibodies and resistance to intranasal challenge suggested that local antibody of any immunoglobulin class is capable of mediating resistance in the lungs to M. pulmonis infection.     

Efficacy of vaccination of calves against hemorrhagic septicemia with a live aroA derivative of Pasteurella multocida B:2 by two different routes of administration

Two groups of four calves each were immunized either intramuscularly (i.m. vaccinated) or intranasally (i.n. vaccinated) at 2 and 6 weeks of age with ca. 10(9) CFU of a derivative of P. multocida serotype B:2 strain 85020 containing a deletion in the aroA gene (strain JRMT12). Both groups of calves and three unvaccinated control calves were challenged subcutaneously at 8 weeks of age with ca. 10(7) CFU of the wild-type 85020 strain. The first and second vaccinations caused a significant pyrexia and increase in the mean demeanor score (P <0.05) in i.m. but not i.n. vaccinated calves. Serum agglutinating activity against whole cells of P. multocida strain 85020 and immunoglobulin G antibody concentrations increased after the second vaccination in i.m. but not in i.n. vaccinated animals, and this difference was statistically significant (P <0.05). Concentrations of serum amyloid A (SAA) increased significantly 3 h after both the primary (P <0.05) and booster (P <0.001) i.m. vaccinations, but not in i.n. vaccinated calves. All four i.m. vaccinated calves were solidly immune to challenge with wild-type P. multocida B:2. However, the mean rectal temperatures, demeanor scores, and serum SAA concentrations of i.n. vaccinated and control calves increased significantly (P <0.01). Three i.n. vaccinated and two control calves were killed for humane reasons within 14 h postchallenge, and postmortem examination revealed pathological lesions consistent with hemorrhagic septicemia. These data showed that the aroA mutant strain, given i.m. as two doses 4 weeks apart, acted as an effective live-attenuated vaccine strain to protect calves against challenge with the virulent parent strain.     

Immune selection for antigenic drift of major outer membrane protein P2 of Haemophilus influenzae during persistence in subcutaneous tissue cages in rabbits.

During persistence of nonencapsulated Haemophilus influenzae in the respiratory tracts of patients with chronic bronchitis, the major outer membrane proteins (MOMPs) P2 and P5 show antigenic drift. The hypothesis that appearance of antigenic variants is the consequence of antibody-dependent selection was tested in a rabbit model. Persistence of H. influenzae d1 was achieved in subcutaneous tissue cages for up to 948 days. During persistence in the rabbits, similar changes in MOMP P2 of H. influenzae occurred, as observed in isolates from chronic bronchitis patients. In rabbits vaccinated with strain d3 and in nonvaccinated rabbits, antigenic drift occurred later than in rabbits vaccinated with strain d1. High titers of antibodies against H. influenzae were measured in tissue cage fluid and serum. Vaccination of the rabbits with H. influenzae d1 or d3, an antigenic variant of strain d1, resulted neither in eradication of H. influenzae d1 nor in increased antibody titers in serum and tissue cage fluid. The sera of nonvaccinated rabbits during persistence had no strain d1-specific bactericidal activity in the presence of complement. Vaccination with H. influenzae d1 induced serum bactericidal activity against strain d1 in the presence of complement. However, a variant of strain d1 appearing in the tissue cages was not killed by this serum bactericidal activity. We conclude that immunological pressure leads to the selection of MOMP variants of H. influenzae and that these variants escape the antibody-mediated strain-specific bactericidal activity against H. influenzae.     

Effects of an inactivated porcine circovirus type 2 (PCV2) vaccine on PCV2 virus shedding in semen from experimentally infected boars

The objective of the present study was to determine the effect of an inactivated porcine circovirus type 2 (PCV2) vaccine on PCV2b virus shedding in the semen of experimentally infected boars by measuring the immunological response and the PCV2b DNA load in blood and semen. Twelve boars were randomly divided into three groups. The boars in group 1 (n = 4) were immunized with an inactivated PCV2 vaccine and were challenged with PCV2b. The boars in group 2 (n = 4) were only challenged with PCV2b. The boars in group 3 (n = 4) served as negative controls. The number of PCV2 genome copies of PCV2 in the serum and semen were significantly lower in vaccinated challenged boars than in nonvaccinated challenged boars at 7, 10, 14, 21, 32, 35, 42, 49, and 60 days postinoculation. The number of PCV2b genomes in the semen correlated with the number of PCV2b genomes in the blood in both vaccinated challenged (R = 0.714) and nonvaccinated challenged (R = 0.861) boars. The results of the present study demonstrate that the inactivated PCV2 vaccine significantly decreases the amount of PCV2b DNA shedding in semen from vaccinated boars after experimental infection with PCV2b.     

Aerosol vaccination of mice with a live, temperature- sensitive recombinant influenza virus.

Mice were vaccinated intranasally (i.n.) or with small-particle aerosols (SPA; 2 mum) or large-particle aerosols (LPA; 8 mum) of an attenuated, temperature-sensitive, recombinant A influenza (H3N2) virus, ts-1 (E). Serum virus-neutralizing and hemagglutination inhibition antibodies were detected for all vaccinated mice by 28 days. Bronchoalveolar wash fluids had increased levels of immunoglobulin (IgG, IgA) only in the i.n. -vaccinated mice. Hemagglutination and virus-neutralizing antibodies were detected in the SPA- and i.n. -vaccinated groups but not in the LPA vaccinates. Upon challenge with SPA of a mouse virulent H3N2 influenza vitus, total protection was obtained for the SPA- and I.N. -vaccinated mice, whereas only 89% of the LPA group survived. Replication of the challenge virus was signifcantly repressed in both the lower and upper respiratory tracts of the three groups of vaccinated mice compared to the nonvaccinated controls. The protection afforded the SPA- and i.n. -vaccinated mice was the same as measured for mice after recovery from earlier subelthal active infection with virulent virus.     

Capsular and somatic serotypes of Pasteurella multocida isolates recovered from healthy and diseased rabbits in Texas.

A total of 111 Pasteurella multocida isolates recovered from healthy and diseased rabbits were typed for capsular and somatic antigens by the typing systems of Carter and Heddleston, respectively. The major serotypes of the 48 P. multocida isolates recovered from nasal cavities of healthy rabbits were serotypes 12:A (33%), nontypable:A (50%), and nontypable:D (10%). Similarly, the major serotypes of the 63 P. multocida isolates obtained from rabbits with rhinitis, pneumonia, conjunctivitis, tympanitis, or cutaneous abscesses were serotypes 12:A (32%), nontypable:A (30%), and 3:A (16%). Serotype 12:A was predominant, regardless of whether the isolates were recovered from healthy or diseased rabbits.     

Evaluation of recombinant lipidated P2086 protein as a vaccine candidate for group B Neisseria meningitidis in a murine nasal challenge model

Neisseria meningitidis is a major causative agent of bacterial meningitis in human beings, especially among young children (相似文献   

Oral immunization of pigs with viable or inactivated Actinobacillus pleuropneumoniae serotype 9 induces pulmonary and systemic antibodies and protects against homologous aerosol challenge.

A dose-defined aerosol infection of pigs was used to study the immunogenic and protective potentials of oral immunization with dead or live Actinobacillus pleuropneumoniae serotype 9 reference strain CVI 13261 against an aerogenic challenge. Pigs were vaccinated with a single dose of 10(11) CFU of viable (n = 8) or inactivated (n = 8) A. pleuropneumoniae given orally in a gelatin capsule. After 3 weeks, vaccinated pigs and nonvaccinated controls were challenged aerogenically with a dose of 10(8) CFU of A. pleuropneumoniae CVI 13261. The protective efficacy of oral immunization was evaluated by clinical and postmortem examinations. Bronchoalveolar lavage in pigs was performed during the experiment to obtain lavage samples for assessment of local antibodies. Isotype-specific antibody responses in sera and in bronchoalveolar lavage fluids were determined by enzyme-linked immunosorbent assays based on whole-cell antigen. Oral immunization did not induce clinical side effects. After aerosol challenge, two animals of both vaccinated groups (25% in each case) showed a moderate fever for 2 days, whereas all four pigs (100%) of the nonvaccinated control group developed severe fever. In contrast to the controls, which developed severe pleuropneumonia, the vaccinated pigs had only mild pulmonary lesions. Three weeks after challenge, 13 of 16 vaccinated pigs (81%) were found to be free of pathomorphological changes of the lungs. From two of these pigs immunized with live bacteria we were able to reisolate A. pleuropneumoniae. A significant systemic and pulmonary increase in the concentrations of immunoglobulin A (IgA), IgM, and IgG antibodies reactive with A. pleuropneumoniae was detectable after aerosol challenge in both vaccinated groups. Immunization with viable bacteria was found to induce significantly higher concentrations of each Ig isotype in bronchoalveolar lavage fluids and sera than immunization with inactivated A. pleuropneumoniae. These serological findings were not reflected in the reduction in clinical disease after challenge in comparison to the case for the pigs vaccinated with inactivated bacteria. We concluded that a single oral administration of A. pleuropneumoniae provides partial clinical protection against aerosol challenge infection in the respiratory tract.     

Evaluation of transport media for Pasteurella multocida isolates from rabbit nasal specimens.

A suitable medium for the transport of Pasteurella multocida in nasal specimens from rabbits was investigated by using pure cultures of the organism and nasal swabs from infected rabbits. First, the ability of eight transport media to preserve the viabilities of P. multocida strains isolated from rabbits was studied. Cary-Blair medium and Leibovitz medium no. 15 (L-15) were found to be superior to the other six media tested, enabling survival of the organism for more than 14 days at room temperature. Second, the survival of P. multocida in nasal specimens was evaluated on both Cary-Blair medium and L-15. The recovery rate of the organism from these two media was more than 80 to 90% during 4 days of storage and decreased gradually with increasing preservation time. There were no significant differences (P > 0.05) in recovery rates of the organism between Cary-Blair medium and L-15. On the basis of these results, we recommend the use of Cary-Blair medium for the transport of P. multocida in rabbit nasal specimens because of the ease of transport of nasal swabs by mail.     

Evaluation of a recombinant vaccinia virus containing pseudorabies (PR) virus glycoprotein genes gp50, gII,and gIII as a PR vaccine for pigs

Summary Pigs vaccinated twice intramuscularly with a highly attenuated strain of vaccinia virus (NYVAC) containing gene inserts for pseudorabies virus (PRV) glycoproteins gp50, gII, and gIII produced neutralizing antibodies for PRV and were less clinically affected than were nonvaccinated pigs following oronasal exposure to virulent PRV. Also, following oronasal exposure to virulent PRV the duration of virulent virus shedding by pigs that had been vaccinated intramuscularly with the recombinant virus was statistically less (p<0.05) than that of nonvaccinated pigs and like that of pigs vaccinated twice intramuscularly with inactivated PR vaccine. Intramuscular vaccination with the recombinant virus was compatible with the most commonly used differential diagnostic tests, namely those based on PRV glycoproteins gX and gI. Serum antibodies for these glycoproteins were absent from the sera of all pigs before and after vaccination with recombinant virus; whereas, they were present in the sera of all of the same pigs after they were exposed to virulent PRV. In contrast to the effectiveness of the recombinant virus administered intramuscularly, neither serum antibody nor clinical protection against PRV was detected when aliquots of the same recombinant virus preparation were administered either orally or intranasally. The latter finding suggests that recombinant virus replicates poorly, if at all, at these sites. If so, the dissemination of recombinant virus from vaccinated pigs to nonvaccinated pigs or other animals in contact seems unlikely.