Immunologic response to Pasteurella haemolytica and resistance against experimental bovine pneumonic pasteurellosis, induced by bacterins in oil adjuvants

Immunogenicity of and protection afforded by Pasteurella haemolytica bacterins were studied in calves. Bacterins contained an aluminum hydroxide in gel (ALH) adjuvant or one of the following oil-in-water adjuvants: Freund's complete adjuvant (FCA), Freund's incomplete adjuvant (FIA), and trehalose dimycolate (TDM). On days 0 and 7, calves were vaccinated with phosphate-buffered saline solution (PBSS), a bacterin, or live P haemolytica. Transthoracic intrapulmonic challenge exposure was done on day 21. In 3 experiments, there were no significant (P greater than 0.05) differences between lung lesions induced in PBSS-or ALH bacterin-vaccinated calves. Both FCA and FIA bacterins significantly (P less than 0.05) enhanced resistance against challenge exposure. Resistance induced by FCA and FIA bacterins was comparable with that induced by vaccination with live P haemolytica. Calves vaccinated with FIA bacterin and challenge-exposed to P haemolytica at a concentration of 4.5 X 10(9) colony-forming units (4.5 times greater than used in the first 3 experiments) resisted challenge exposure similar to calves given live organisms. The TDM bacterin failed to enhance resistance. All bacterins caused a significant increase (P less than 0.05) in serum antibody to P haemolytica somatic antigens, as measured by a quantitative fluorometric immunoassay. Pasteurella haemolytica leukotoxin neutralizing antibody titers did not increase significantly (P greater than 0.05) in sera after vaccination with any bacterin. Vaccination with FCA and FIA bacterins resulted in a significant increase (P less than 0.001) in serum antibody to a carbohydrate-protein subunit of P haemolytica, as measured by an enzyme-linked immunosorbent assay.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of vaccination with live or killed Pasteurella haemolytica on resistance to experimental bovine pneumonic pasteurellosis

Using 6- to 8-month-old beef calves, 3 experiments were conducted to compare the effect of vaccination with live or killed Pasteurella haemolytica on resistance to a transthoracic challenge exposure with the organism and to correlate serum antibody response with resistance. In each experiment, calves were vaccinated twice at 1-week intervals and were challenge exposed 21 days after the first inoculation. Lung lesions were evaluated by a system, such that higher scores indicated the more severe lesions. In each experiment, calves immunized with live P haemolytica had lower lesion scores than calves vaccinated with saline solution or bacterin. In 2 of the experiments, the differences were significant (P less than 0.05). In all experiments, calves vaccinated parenterally with a commercial P haemolytica/P multocida bacterin or with a formalin-killed P haemolytica bacterin had lesion scores that were not significantly different (P greater than 0.05) than for control calves vaccinated with saline solution. Live and killed bacterial preparations induced a significant serum antibody response to P haemolytica as measured by a quantitative fluorometric immunoassay. The antibody response to vaccination was not affected by preexisting titers to P haemolytica. Serum antibody titers were not consistently as high for calves vaccinated with bacterins as for calves vaccinated with live organisms. Although high antibody titers correlated with low lesion scores when calves vaccinated with saline solution or live organisms were analyzed collectively, there was not a significant correlation between the 2 variables when calves, vaccinated with saline solution or with bacterin, were analyzed collectively. These data indicate that, although bacterins may induce a detectable serum antibody response, they do not induce protection against transthoracic challenge exposure to P haemolytica.     

Serum IgG and IgM antibody response in cattle to antigens of Pasteurella haemolytica

The serum IgG and IgM antibody responses of 48 cattle vaccinated with live Pasteurella haemolytica (LIVE), formalin-killed P. haemolytica in Freund's incomplete adjuvant (FIA), or formalin-killed P. haemolytica in aluminum hydroxide adjuvant (ALH) to a variety of P. haemolytica antigens were evaluated. Enzyme-linked immunosorbent assays (ELISAs) were used to determine the sequential and day 21 IgG and IgM antibody responses to whole P. haemolytica (WB), a capsular carbohydrate-protein subunit (CPS) extracted from the organism, P. haemolytica capsular carbohydrate (CC), and P. haemolytica leukotoxin (LT). LIVE and FIA vaccinates developed generally higher IgG and IgM responses to all antigens compared to ALH vaccinates. LIVE vaccinates developed IgG responses to LT which were significantly higher (P less than 0.05) than all other vaccinates. In contrast, FIA vaccinates developed significantly higher IgG responses to CPS than all other vaccinates. On the basis of the ELISA results, similar or cross reacting antigenic sites were present in preparations containing surface antigens (WB, CPS and CC), but not LT. Disease resistance, as determined by experimental lesions induced in the 48 calves by transthoracic challenge with P. haemolytica, was significantly greater in the LIVE and FIA vaccinates compared with ALH vaccinates. No significant difference in resistance was detected between LIVE and FIA vaccinates. Lesions in ALH vaccinates were not significantly different than those in phosphate-buffered saline (PBS) controls. Increased IgG responses to all antigens were significantly associated with resistance to experimental disease; however, IgG responses to CPS were most highly correlated with resistance. The only IgM response which was significantly correlated with resistance was the response to CPS. These studies indicate that serum IgG antibody responses to various surface antigens of P. haemolytica, as well as LT, can enhance resistance to experimental pneumonic pasteurellosis. Serum IgM responses, however, do not appear to play a major role in resistance to experimental disease.     

Serum antibodies to Pasteurella haemolytica lipopolysaccharide: relationship to experimental bovine pneumonic pasteurellosis

An enzyme-linked immunosorbent assay was used to determine the serum antibody response to Pasteurella haemolytica lipopolysaccharide (LPS) for calves vaccinated with saline solution, a formalin-killed P haemolytica bacterin, or live P haemolytica. Bacterin-vaccinated calves had a lower antibody response to LPS than did calves vaccinated with live P haemolytica. Calves vaccinated with either saline solution or the bacterin were more susceptible to intrapulmonic challenge exposure with P haemolytica than were calves vaccinated with liver organisms. Serum antibody responses to P haemolytica LPS did not seem important for resistance to challenge exposure, because there was no significant correlation (P greater than 0.05) between the lung lesion score and antibody response to P haemolytica LPS. There was a highly significant correlation (P less than 0.001) between antibody detected against P haemolytica LPS and that against formalin-killed P haemolytica. Competitive binding studies indicated that P haemolytica LPS is a major antigenic determinant on the surface of P haemolytica. There did not seem to be substantial cross-reaction between LPS from P haemolytica and that from Escherichia coli (serotype O26:B6).     

Vaccination studies against experimental bovine Pasteurella pneumonia.

Vaccination-challenge experiments were conducted in colostrum-deprived calves to evaluate the efficacy of Pasteurella bacterins and vaccines against experimental pneumonic pasteurellosis. Calves were vaccinated with formalin-killed bacterins and live vaccines, then challenge exposed intratracheally with P. haemolytica or P. multocida. Infectious bovine rhinotracheitis virus was inoculated intranasally three to four days prior to P. haemolytica challenge-exposure. All calves were examined for macroscopic and microscopic lesions after being found dead or following euthanasia four to seven days after challenge exposure with the bacterial pathogen. Clinical, hematological, and pathological responses to challenge exposure in aluminum hydroxide absorbed P. haemolytica and P. multocida bacterin-treated calves were consistent with the pneumonic lesions of pulmonary pasteurellosis in the control calves. An oil-adjuvanted P. haemolytica bacterin limited clinical and pathological responses in the affected calves whereas a P. multocida oil-adjuvanted bacterin did not. Both clinical and pathological responses to challenge exposure in calves vaccinated with live Pasteurella vaccines were less severe than those of the control calves. Vaccine effectiveness appeared to be dose dependent.     

Serum antibodies to antigens derived from a saline extract of Pasteurella haemolytica: correlation with resistance to experimental bovine pneumonic pasteurellosis

The serum antibody response was determined to 6 antigen groups (AG's) derived from a saline extract (SE) of Pasteurella haemolytica, serotype 1. Using an enzyme-linked immunosorbent assay, sera were analyzed from 65 calves that had been previously vaccinated with saline, the unfractionated SE, a bacterin, or live P. haemolytica. The serum antibody responses to the 6 AG's were correlated with resistance to an experimental transthoracic challenge with the organism. The antibody responses to AG's 1, 5, and 6 appeared to be potentially important in resistance to challenge. In the 3 experiments conducted, a significantly higher (p less than 0.05) increase in antibody was seen to AG's 1, 5, and 6 in calves vaccinated with live organisms compared to those vaccinated with the bacterin. A significant correlation (p less than 0.05) was seen between high antibody to AG 1 and resistance to challenge in all 3 experiments. In 2 of the 3 experiments, a significant correlation (p less than 0.05) was seen among high antibody titers to AG's 5 and 6 and resistance, whereas in 1 experiment the correlation was significant (p less than 0.05) between antibody to AG 4 and resistance. A rise in antibody to AG's 2 and 3 was seen only in calves vaccinated with SE. Because AG's 1, 5, and 6 are higher in carbohydrate than the other AG's, this suggests that antibody to polysaccharide antigens may be important to resistance. Other potentially protective antigens of P. haemolytica are discussed.     

Immunologic response and resistance to experimentally induced pneumonic pasteurellosis in cattle vaccinated with various dosages of lyophilized Pasteurella haemolytica

Pasteurella haemolytica was lyophilized in an enriched soybean polypeptone broth. Lyophilization in this medium resulted in a mean 10-fold loss in P haemolytica viability, as opposed to up to a 10(4)-fold loss in viability when other media were used. Lyophilized P haemolytica was reconstituted and used as a live vaccine in 3 experiments. Calves were challenge exposed by transthoracic injection with virulent P haemolytica. In experiment 1, 2 subcutaneous injections (7-day interval between injections) with 5 ml of recently harvested (1 X 10(9) colony-forming units [CFU]/ml) or lyophilized (1 X 10(8) CFU/ml) P haemolytica significantly (P less than 0.001) enhanced resistance against challenge exposure, compared with resistance in calves given saline solution or sterile medium (control calves) or calves vaccinated with lyophilized organisms at a concentration of 1 X 10(6) CFU/ml. In experiment two, 1, 2, or 5 ml of lyophilized P haemolytica (1 X 10(8) CFU/ml) significantly (P less than 0.05) enhanced resistance, compared with resistance in calves given saline solution (control calves). In experiment three, 1 or 2 injections of lyophilized P haemolytica significantly (P less than 0.01) enhanced resistance against challenge exposure, compared with that of calves given saline solution. The mean lesion score for calves given 1 injection was not significantly higher than the mean lesion score for the group given 2 injections. Vaccination with lyophilized P haemolytica vaccine caused significant (P less than 0.05) increases in serum antibody to P haemolytica somatic antigens, to a carbohydrate-protein subunit of the organism, and to leukotoxin.     

Sequential titration of bovine lung and serum antibodies after parenteral or pulmonary inoculation with Pasteurella haemolytica

Calves were vaccinated by intrabronchial or subcutaneous injection of formalinized Pasteurella haemolytica. Antibody in serum, nasal washings, and bronchoalveolar washings was titrated sequentially before and after calves were vaccinated and then challenge exposed with live homologous bacteria. Bronchoalveolar washings were collected by fiberoptics bronchoscopy, and antibody was titrated by indirect (antiglobulin) bacterial agglutination. Responsiveness to vaccination was related in initial serum antibody concentrations. Calves with serum antibody titers of 1:20 or more were nonresponsive, whereas with few exceptions, calves having titers of less than 1:20 responded to vaccination. Results indicated that serum and lung antibody were induced by subcutaneous or by intrabronchial inoculation of formalinized P haemolytica. By either route of immunization, serum antibody was more persistent than was lung antibody, and pulmonary challenge exposure with live P haemolytica did not alter existing titers.     

In vitro lymphocyte proliferative responses and gamma-interferon production as measures of cell-mediated immunity of cattle exposed to Pasteurella haemolytica.

Cell-mediated immune mechanisms may play a role in the pathogenesis and prevention of pneumonia in cattle caused by Pasteurella haemolytica serotype A1. To determine the circumstances required to stimulate and identify cell-mediated immune responses, calves were vaccinated with a commercial P. haemolytica bacterin or a live commercial P. haemolytica vaccine, or were infected intratracheally with virulent P. haemolytica. All calves were challenge-exposed intratracheally with P. haemolytica 31 d after vaccination or prior infection. Peripheral blood mononuclear cells and mediastinal and superficial cervical lymph node cells were stimulated with antigens prepared from P. haemolytica to evaluate in vitro proliferative responses and gamma-interferon production as measures of cell-mediated immunity. Strong proliferative responses and gamma-interferon production were detected in lymph node cells from calves vaccinated with the live vaccine and from infected calves, especially in response to stimulation with an outer membrane protein preparation from P. haemolytica. Greater proliferative responses and gamma-interferon production were associated with the lymph node nearer the site of bacterin administration (superficial cervical lymph node) or the site of infection (mediastinal lymph node), whereas greater proliferative responses and gamma-interferon production were associated with the more distant lymph node (mediastinal lymph node) in calves vaccinated with the live vaccine. Neither proliferative responses nor gamma-interferon production were detected in peripheral blood mononuclear cells from calves that were vaccinated for or infected with P. haemolytica. Antileukotoxin antibody titers were determined by a serum neutralization assay, and protection against pneumonic lesions was more closely correlated with antileukotoxin antibody responses than with lymphocyte proliferation or gamma-interferon responses.     

Effect of prior natural exposure to Pasteurella haemolytica on resistance to experimental bovine pneumonic pasteurellosis

The effect of prior natural exposure to Pasteurella haemolytica, as determined serologically, was studied with respect to resistance to experimental pneumonic pasteurellosis in 20 calves from 3 experiments. Resistance to challenge exposure was measured using a lesion-scoring system. As measured by a quantitative fluorometric immunoassay, naturally acquired serum antibody titers to the organisms were 0 to 228. There was a significant correlation (P less than 0.05) between high naturally acquired antibody titers and resistance to transthoracic challenge exposure with P haemolytica.     

Efficacy of a streptomycin-dependent, live Pasteurella haemolytica vaccine against challenge exposure to Pasteurella haemolytica in cattle

A streptomycin-dependent, live Pasteurella haemolytica vaccine was given in 1 or 2 doses to 2 groups of weaned calves; 2 other groups of calves were not vaccinated. All calves in the vaccinated groups and calves in 1 of the nonvaccinated groups were stressed by transport, intratracheally inoculated with bovine herpesvirus type-1 (Cooper strain), and then intratracheally inoculated with P haemolytica type A1. The 4th group of calves (nonvaccinated controls) was not stressed and were not intratracheally inoculated with virus or bacteria. Mean daily weight gains, total clinical sign scores, lung lesion scores, plasma fibrinogen concentrations, and antibody titers against P haemolytica were determined at various intervals. Calves that had been vaccinated twice had greater mean daily weight gains and lower total clinical sign scores and lung lesion scores than did nonvaccinated, challenge-exposed calves, but the difference was not significant (P greater than 0.05). Calves vaccinated once had the greatest mean daily weight gains, the lowest total clinical sign scores, and the lowest lung lesion scores when compared with the other 2 challenge-exposed groups of calves. Mean daily weight gains and total clinical sign scores of calves vaccinated once were significantly different (P less than 0.05) than those of calves vaccinated twice. Nonvaccinated, nonchallenge-exposed control calves did not develop clinical signs of disease, did not develop lung lesions, and had consistently positive daily weight gains, and had scores in these areas that were significantly different (P less than 0.05) from those of all challenge-exposed groups of calves. Increases in plasma fibrinogen concentrations corresponded to infection with P haemolytica.(ABSTRACT TRUNCATED AT 250 WORDS)     

Aerosol vaccination of calves with pasteurella haemolytica against experimental respiratory disease.

Three experiments were conducted on calves in which the efficacy of vaccination with live Pasteurella haemolytica in aerosol was tested by challenge with sequential aerosol exposure to bovine herpesvirus 1 and P. haemolytica. Neither single nor multiple aerosol vaccinations protected against the experimental disease. Macroscopically recognizable rhinitis, tonsillitis, tracheitis and pneumonia occurred in both controls and vaccinates. In one experiment as many as three aerosol vaccinations with live P. haemolytica for up to 20 minutes failed to elicit clinical signs in exposed calves. Pasteurella haemolytica was isolated less frequently from tissues of vaccinated calves than from those of nonvaccinated calves. Pasteurella haemolytica was isolated from deep nasal swabs of 4/14 vaccinated calves five and six days after viral exposure. It was concluded that although bovine herpesvirus 1 vaccination has been shown previously to prevent the experimental disease produced by bovine herpesvirus 1-P. haemolytica, live P. haemolytica vaccination by aerosol will not provide the same protection.     

Safety and efficacy testing of a novel multivalent bovine bacterial respiratory vaccine composed of five bacterins and two immunogens

Bovine bacterial respiratory diseases have been one of the most serious problems due to their high mortality and economic loss in calves. The vaccinations of bovine bacterial respiratory vaccines have been complex because of no multivalent vaccine. In this study, novel multivalent bovine bacterial respiratory vaccine (BRV) was developed and tested for its safety and efficacy. BRV was composed of two immunogens and five bacterins. These were leukotoxoid and bacterin of Mannheimia haemolytica type A, outer membrane protein and bacterin of Pasteurella multocida type A, and bacterins of Haemophilus somnus, Mycoplasma bovis, and Arcanobacterium pyogenes. ELISA antibody titers to five bacterial antigens in vaccinated guinea pigs increased, compared with those in unvaccinated ones. BRV was safe for calves and pregnant cattle in this study. In calves challenged with M. haemolytica and P. multocida, the average daily weight gain and antibody titers of vaccinated calves increased, and respiratory symptoms (P<0.05) and treatment frequency (P<0.01) of vaccinated calves significantly decreased, compared with those of unvaccinated calves. Interestingly, the antibody titers of M. haemolytica leukotoxoid and Mycoplasma bovis were closely related with the reduction of respiratory symptoms. BRV would be an ecomonical measure for the protection against bovine bacterial respiratory diseases.     

Bovine pneumonic pasteurellosis: effect of culture age of Pasteurella haemolytica used as a live vaccine

Five experiments were conducted that compared aerosol immunization of calves with live Pasteurella haemolytica from logarithmic (6 hour) or stationary (20 to 22 hour) phase cultures. Calves were challenge exposed by transthoracic injection with P haemolytica. In 4 experiments, calves inoculated with 6-hour cultures had slightly lower mean lesion scores (indicating greater resistance to challenge exposure) than those inoculated with 20- to 22-hour cultures. High antibody titers, as detected by a quantitative fluorometric immunoassay or the indirect hemagglutination test, correlated directly with lung resistance (based on lesion scores) regardless of the age of the culture used as the immunogen.     

Effects of various vaccination protocols on passive and active immunity to Pasteurella haemolytica and Haemophilus somnus in beef calves.

Two field trials were conducted in a beef cow herd in Saskatchewan to determine the effectiveness of a combined Pasteurella haemolytica and Haemophilus somnus vaccine in increasing passively and actively acquired antibodies in beef calves. Vaccination of dams at 4 and/or 7 weeks prepartum was associated with increased antibody titers to P. haemolytica and H. somnus in their serum (P < 0.05), colostrum (P < 0.05), and serum of their calves at 3 days and 1 month of age (P < 0.05). There was no significant (P > 0.05) difference in antibody titers in the colostrum and serum of calves from single or double vaccinated dams. Calves vaccinated at 1 and 2 months of age in the face of maternal antibodies to P. haemolytica and H. somnus had significantly (P < 0.05) higher antibodies to P. haemolytica and H. somnus at 4 and 6 months of age than did unvaccinated calves. Calves vaccinated at 3 and 4 months of age in the face of low levels of preexisting antibodies had significantly (P < 0.05) higher antibodies to P. haemolytica at 5 months of age and to H. somnus at 5 and 6 months of age than did unvaccinated calves. Calves vaccinated once at 4 months of age had significantly (P < 0.05) higher antibody titers to P. haemolytica and H. somnus at 4.5 months of age than did unvaccinated calves, but this difference was not apparent at 6 months of age.(ABSTRACT TRUNCATED AT 250 WORDS)     

Preliminary studies with a live streptomycin-dependent Pasteurella multocida and Pasteurella haemolytica vaccine for the prevention of bovine pneumonic pasteurellosis.

Twelve Pasteurella-free Holstein-Friesian calves were used in a study to test the efficacy of a live streptomycin-dependent Pasteurella multocida A:3 and streptomycin-dependent Pasteurella haemolytica A1 vaccine. The calves were inoculated intramuscularly twice at 14-day intervals with either the streptomycin-dependent vaccine, containing 1 X 10(6) colony forming units/mL P. multocida and 4 X 10(8) colony forming units/mL P. haemolytica, commercial bacterin, or phosphate buffered saline. Two weeks following the second vaccination, all calves were challenged by intranasal inoculation of 10(8) TCID50/4.0 mL infectious bovine rhinotracheitis virus followed three days later by intratracheal injection with 2.3 X 10(7) colony forming units/mL of a 16 hour culture of P. multocida A:3 and 2.6 X 10(8) colony forming units/mL of an 8 hour culture of P. haemolytica A1. Seven days after challenge with Pasteurella, calves were killed for collection of tissues at necropsy. Each calf was given a score based on macroscopic and microscopic lesions. The scores for the calves receiving live vaccines were significantly lower (p less than 0.025) than those for the controls. Also, the calves receiving live vaccines had a significant (p less than 0.05) increase in the level of serum antibody to P. haemolytica. The results of this preliminary study showed that the streptomycin-dependent vaccine offered better protection than the commercial bacterin against a virulent homologous challenge.     

Immune responses of calves antigenically stimulated and challenge exposed with Anaplasma marginale during tick infestation or treatment with dexamethasone

Similar anamnestic antibody responses to a 2nd injection of a Anaplasma marginale vaccinal antigen were observed in calves infested with the tick Dermacentor albipictus and in tick-free calves. When challenge exposure of these calves to virulent A marginale was done, infestation with the tick Boophilus microplus increased anemia (P less than 0.01), but did not suppress antibody production to A marginale or increase parasitemia. None of the vaccinated calves, regardless of infestation, experienced clinical anaplasmosis. Mitogenic responses of lymphocytes from infested animals were unaltered by either infestation. Tick infestations did not cause immune suppression in the calves, whereas use of dexamethasone resulted in a significantly lower antibody response (P less than 0.05) after a 2nd injection of vaccinal antigen. After challenge with virulent A marginale, dexamethasone-treated calves showed more pronounced parasitemia (P less than 0.01) and anemia (P less than 0.01) than did control calves. Anaplasmosis did not prevent the calves from developing resistance to reinfestation, which was accompanied by immediate, but not delayed, hypersensitivity reactions against homologous tick extracts. Dermacentor albipictus did not seem to share common antigenic determinants with B microplus, since extracts from the latter did not elicit immediate hypersensitivity responses in calves sensitive to D albipictus extracts. Calves were somewhat resistant to reinfestation as evidenced by reduced numbers of adult fed ticks, decreased weights of ticks after feeding, and smaller egg masses.     

Cloning and expression of a 30 kDa surface antigen of Pasteurella haemolytica

Pasteurella haemolytica biotype A serotype 1 is the principal etiologic agent of bovine pneumonic pasteurellosis. A clear understanding of the pathogenesis of this disease and the mechanisms of resistance to it has been limited by a lack of information on the important antigens of the organisms. Using recombinant DNA techniques we have cloned a segment of DNA from P. haemolytica A1 that encodes three proteins of 28, 30, and 32 kDa. Two of these proteins, 30 and 28 kDa, react strongly on a Western blot with a bovine serum raised against live cells of P. haemolytica A1. The gene for the 30 kDa protein was localized to a 3.1 kbp EcoRI fragment, and expression of the 30 kDa protein was found to be independent of an E. coli promoter. The 30 kDa protein comigrated with a 30 kDa P. haemolytica protein that was susceptible to radioiodination and presumably exposed on the bacterial cell surface. The other principal radiolabeled P. haemolytica proteins were 100, 45, and 15 kDa. Antibodies against the 30 kDa protein, isolated from E. coli carrying the recombinant plasmid, recognized 30 kDa and 15 kDa proteins in P. haemolytica serotypes 1-15 and caused agglutination of whole P. haemolytica A1 cells. Cattle vaccinated with live P. haemolytica, P. haemolytica outer membrane proteins, or the cloned 30 kDa protein developed antibodies to the cloned 30 kDa protein as detected by Western blotting and densitometry. Sera were obtained from cattle vaccinated with live or killed P. haemolytica or saline and challenged with P. haemolytica. Those sera were evaluated for antibody responses to the cloned 30 kDa protein. High antibody responses to the 30 kDa protein significantly correlated (P less than 0.01) with resistance to challenge. From these studies it is concluded that the 30 kDa protein represents a surface antigen of P. haemolytica A1 that may be important in inducing immunity to P. haemolytica.     

Lamb model in the study of immunity to enteropathogenic Escherichia coli infections

Three groups of ewes were vaccinated with formalin inactivated, whole cell, aluminum hydroxide adjuvanted bacterins prepared from capsulated enteropathogenic Escherichia coli (EEC). Lambs born to and suckling these ewes, compared with lambs of nonvaccinated control ewes, were highly resistant to homologous EEC challenge exposure. Lambs of ewes vaccinated with products prepared from K99 antigen-positive, noncapsulated E coli were highly resistant to heterologous EEC challenge exposure. In both cases, lambs of vaccinated ewes had significantly (P less than 0.005) less morbidity and mortality, fewer challenge inoculum-type E coli per rectal swab evaluation, and had superior weight gains over a 4-day period. Immunoglobulin assay of 122 lamb sera (collected 12 hours after birth) failed to reveal any correlation between serum immunoglobulin values and morbidity or mortality. When tested by plate agglutination technique, using whole cell antigens, or by reverse radial immunodiffusion, using purified capsular antigens, colostral whey samples of vaccinated ewes did not have increased capsular antibody titers. The K99 serum antibody values of K99 antigen-vaccinated ewes were markedly higher than were those of ewes vaccinated with other bacterins or of control ewes.     

Bovine pneumonic pasteurellosis: experimental induction in vaccinated and nonvaccinated calves.

A study was undertaken to investigate the effects of the immune response induced by combined aerosol and parenteral vaccination on the lung lesions induced in calves by Pasteurella haemolytica AI. Twenty-four calves, twelve of which had been vaccinated with killed P. haemolytica by aerosol and subcutaneous injection in Freund's complete and incomplete adjuvant were challenged by intratracheal inoculation of live P. haemolytica. Serological response to vaccination was not marked but was best measured by the whole cell agglutination test or by indirect bacterial agglutination rather than by the passive haemagglutination test. Titres of vaccinates were positively correlated with the degree of pneumonic change following challenge while in nonvaccinated controls, titres were negatively correlated with lung lesions. These findings suggest the occurrence of an immunologically mediated hypersensitivity pneumonitis in the lungs of vaccinates and point to the potential efficacy of live bacterial aerosols for stimulation of protective immunity in pneumonic pasteurellosis.