Effects of delivery method on serological responses of bighorn sheep to a multivalent Pasteurella haemolytica supernatant vaccine.

The safety and efficacy of a remotely delivered multivalent Pasteurella haemolytica supernatant vaccine (serotypes A2 and T10) were examined in captive Rocky, Mountain bighorn sheep (Ovis canadensis canadensis). Twenty bighorn sheep were grouped according to baseline leukotoxin neutralizing antibody titers (< or =2 or >2 log2(-1)) and vaccination history (previously vaccinated or unvaccinated). Within these groups, animals were randomly assigned to one of two delivery treatments: hand injection (control) or biobullet implantation. All bighorns received a single dose from the same lot of vaccine (n = 10/treatment); four additional animals were injected intramuscularly with 0.9% saline as unvaccinated sentinels. Mild, transient lameness one day after hand injection or biobullet implantation was the only adverse effect. Serum neutralizing antibody titers to P. haemolytica leukotoxin differed between delivery treatments (P = 0.009) and among baseline titer/vaccination history groups (P = 0.013). Neutralizing titers were higher among hand-injected bighorns. Although neutralizing titers were lower among implanted bighorns than hand-injected controls at 1 wk (P = 0.002) and 2 wk (P = 0.021) after vaccination, seroconversion rates in response to implantation (6/10) and hand injection (9/10) did not differ (P = 0.303). Agglutinating antibody titers to T10 were high and did not vary over time or between delivery treatments. Agglutinating antibody titers to A2 in the hand-injected controls were not different (P > or = 0.07) than those in bighorns vaccinated with biobullet implantation. These data demonstrate that although hand injection elicits higher absolute titers, biobullet implantation may also stimulate effective antibody responses to P. haemolytica supernatant vaccine. Further evaluation of biobullet vaccination against pneumonic pasteurellosis in free-ranging populations of wild bighorn sheep is warranted.

Efficacy of a nonadjuvanted, outer surface protein A, recombinant vaccine in dogs after challenge by ticks naturally infected with Borrelia burgdorferi.

In a blinded, controlled study, thirty purpose-bred, Borrelia burgdorferi negative, mixed-breed dogs 10 to 12 weeks of age were randomly divided into three groups of ten animals each for the purpose of evaluating a recombinant nonadjuvanted B. burgdorferi OspA vaccine (Recombitek Lyme [Merial Limited]) for efficacy and safety. Two groups received two doses of two different lots ofa nonadjuvanted, OspA, recombinant vaccine; the third group served as nonvaccinated controls. All dogs were challenged 3 weeks after the second vaccination with blacklegged deer ticks (Ixodes scapularis) harvested from a B. burgdorferi endemic area in Rhode Island. Clinical signs, antibody titers by ELISA, Western blot assays, and isolation and polymerase chain reaction analyses of spirochetes from biopsy specimens were used to evaluate vaccine efficacy. Direct fluorescent antibody assay was used to evaluate the infection rate in the challenge ticks and in naïve ticks allowed to feed on study dogs after the dogs were infected (xenodiagnosis). Vaccinates responded with high levels of antibodies (determined by ELISA and measured by optical density [OD]), which did not rise after challenge. Vaccinates demonstrated no clinical signs, negative isolation of spirochetes on biopsy, only an OspA antibody pattern on Western blot assay, and negative isolation of spirochetes on biopsy, confirming that the vaccine blocked infection with B. burgdorferi in all vaccinated dogs (20/20). Control dogs demonstrated clinical signs (2/10), antibodies characteristic of infection with B. burgdoferi (10/10), isolation of spirochetes (10/10), and polymerase chain reaction (PCR) detection of spirochetes (9/10). The recombinant, nonadjuvanted B. burgdoferi vaccine protected 100% of vaccinates against infection after a severe challenge that infected 100% of control dogs. The OspA vaccine proved to be highly safe and effective in this study.

Evaluation of a multivalent Pasteurella haemolytica vaccine in bighorn sheep: protection from experimental challenge.

The efficacy of a multivalent Pasteurella haemolytica vaccine (A1, A2, T10) in reducing morbidity and mortality associated with pneumonic pasteurellosis in bighorn sheep (Ovis canadensis) was examined. Fifteen captive bighorns were divided equally into three treatment groups based on vaccination status: control (no vaccination), one dose 10 days prior to challenge, or one or two doses 57 wk prior to challenge. At challenge, each bighorn received about 6.2 x 10(7) colony forming units of P. haemolytica (biotype T, serotype 10, biogroup 4-CDS; ribotype ECO; "Alamosa Canyon" strain) suspension sprayed into the proximal trachea. Vaccination reduced (P = 0.1) mortality in bighorns vaccinated 10 days prior to challenge as compared to controls. Although mortality rates in bighorns vaccinated 57 wk prior to challenge did not differ from controls (P = 0.26), a trend in reduced mortality was apparent. Ranked cumulative postmortem scores based on observed gross lesions and bacteriology did not differ (P > or = 0.14) between vaccinated animals and control animals. Neutralizing antibody titers to P. haemolytica leukotoxin were elevated (P = 0.003) at challenge in bighorns vaccinated 10 days before challenge, and neutralizing titers in bighorns from both vaccinated groups were elevated at death < or = 7 days after challenge (P < or = 0.004). In contrast, agglutinating antibody titers to P. haemolytica serotype A1 or T10 surface antigens did not differ between vaccinated and unvaccinated bighorns (P > or = 0.19). Based on these data, we believe that this experimental P. haemolytica vaccine is safe and can stimulate protective immunity from pneumonic pasteurellosis in bighorn sheep. Further evaluation of this vaccine as a tool in preventing and managing pasteurellosis in wild bighorn sheep appears warranted.

Evaluation of a multivalent Pasteurella haemolytica vaccine in bighorn sheep: safety and serologic responses.

We examined effects of a multivalent Pasteurella haemolytica vaccine (serotypes A1, A2, T10) on humoral immune responses and P. haemolytica isolation rates in bighorn sheep (Ovis canadensis). Thirty captive bighorns, divided into groups of three on the basis of age, sex, and previous history of pneumonic pasteurellosis, received 0, 1, or 2 vaccine doses. Mild, transient lameness in most bighorns 1 day after initial vaccination was the only adverse effect observed. Oropharyngeal (> or = 75%) and nasal (< or = 50%) isolation rates for P. haemolytica did not differ among treatment groups. Ten of 36 distinguishable biogroup variants accounted for about 87% of the 464 P. haemolytica isolates from bighorns, but prevalences of specific biogroups were not affected by vaccination. Bighorns receiving 1 or 2 vaccine doses showed marked elevations in leukotoxin neutralizing antibody titers beginning 1 wk after vaccination. Agglutinating antibody titers to serotype A1 and A2 surface antigens were also elevated in vaccinated bighorns within 2 wk after vaccination; agglutinating antibody titers to serotype T10 surface antigens were relatively high in all three groups but appeared unaffected by vaccination. Vaccination 7 to 14 wk prior to parturition elevated leukotoxin neutralizing antibody titers in colostrum, but neither leukotoxin neutralizing nor serotype A1 surface antigen agglutinating antibody titers differed through 16 wk of age among lambs born to dams from different vaccine dose groups. Our data demonstrate that this multivalent P. haemolytica vaccine is safe and stimulates marked antibody responses in bighorn sheep. Further evaluation of this vaccine as a tool in preventing and managing pasteurellosis in bighorn sheep appears warranted.

Comparison of protection of experimentally challenged cattle vaccinated once or twice with a Pasteurella haemolytica bacterial extract vaccine.

Three groups of calves (15-18 per group) were injected twice at a 3-week interval with 2 doses of phosphate buffered saline (PBS, CONTROL group), 2 doses of PRESPONSE, a Pasteurella haemolytica A1 bacterial extract vaccine (PRESPONSE-2 group) or 1 dose of PBS followed by a 2nd vaccination with 1 dose of PRESPONSE (PRESPONSE-1 group). Three weeks after the 2nd vaccination, the calves were challenged intratracheally with P. haemolytica A1. Calves were evaluated clinically for 3 days prior to challenge and for 5 days after challenge. Six days postchallenge, calves were either euthanized or sent to slaughter and the lungs were evaluated for percent pneumonic tissue. There was a significant effect of single or double application of vaccine on clinical scores (P = 0.0409). Percent pneumonic tissue at necropsy was significantly affected by vaccine group (P = 0.014). Calves in the CONTROL group had significantly higher percent pneumonic tissue after arcsine transformation (45.30%) than calves in any group receiving PRESPONSE, regardless of vaccination frequency (25.18% and 25.78%, for calves receiving 2 doses or 1 dose of PRESPONSE, respectively). Both serum toxin neutralizing and direct agglutinating titers were negatively correlated with percent pneumonic tissue. Most importantly, 1 dose of PRESPONSE was as efficient as 2 doses at eliciting a protective immune response. It is concluded that the presence of P. haemolytica as a natural commensal in the upper respiratory tract of the calf can effectively prime the animal, and allow the animal to respond in an anamnestic nature to only 1 dose of this vaccine.

Sialoglycoprotease of Pasteurella haemolytica A1: detection of antisialoglycoprotease antibodies in sera of calves.

Log phase culture supernate from Pasteurella haemolytica biotype A, serotype 1 contains a proteolytic enzyme specific for O-sialoglycoproteins. Using two methods, Western immunoblotting and enzyme neutralization assay, it was demonstrated that certain bovine sera from two previous P. haemolytica A1 vaccination and challenge trials contained antibodies (Ab) (isotypes IgG1 and IgG2 on Western immunoblot) to the sialoglycoprotease (Gcp). In these trials, selected calves were vaccinated twice with either the commercial culture supernate vaccine Presponse or given phosphate-buffered saline (PBS). One trial was conducted during spring, P. haem XIX, and the other during the winter, P. haem XXI. Although there was no clear evidence for induction of anti-Gcp in response to vaccination, several calves seroconverted following intrapulmonary challenge with live P. haemolytica A1. This is the first report of anti-Gcp Ab in bovine sera. The results indicated that the Gcp is immunogenic and that the bacterium produces the enzyme in vivo. Further, animals with an anti-Gcp response had less pneumonia at necropsy, suggesting the Gcp may induce protective immunity.

Clinical and serological evaluation of a Pasteurella haemolytica A1 capsular polysaccharide vaccine.

The purified capsular polysaccharide (CPS) of Pasteurella haemolytica A1 was examined for its ability to protect cattle from experimental challenge with logarithmic-phase P. haemolytica. Several preparations of P. haemolytica antigens were utilized in the experiment including CPS, log-phase P. haemolytica culture supernatant, P. haemolytica recombinant leucotoxin (rLKt) and various combinations of the above. CPS alone or in combination with culture supernatant or rLkt elicited no protection; rather, administration of CPS was associated with a high incidence of anaphylaxis (36% of calves). Although a classical biphasic humoral immune response to CPS could be detected in all calves that received this compound, this T-dependent response was not correlated with resistance to experimental challenge. The complexity of protective immunity in pneumonic pasteurellosis is emphasized by this study, and clinical anaphylaxis associated with response to CPS may be implicated in the pathogenesis of disease.

Efficacy of recombinant leukotoxin in protection against pneumonic challenge with live Pasteurella haemolytica A1.

The recombinant leukotoxin (rLKT) of the bacterium Pasteurella haemolytica A1 was examined for its ability to protect cattle from experimental challenge with logarithmic-phase P. haemolytica. Six different vaccines were utilized in the experiment: P. haemolytica culture supernatant, P. haemolytica culture supernatant enriched with rLKT, rLKT alone, P. haemolytica culture supernatant enriched with Escherichia coli supernatant not containing LKT, E. coli supernatant alone, and phosphate-buffered saline. rLKT alone showed no protective capacity against development of clinical signs of respiratory disease or against development of postmortem lung lesions after experimental challenge. It was, however, shown to enhance the efficacy of the culture supernatant vaccine and decrease clinical signs and pneumonic lesions. The complexity of protective immunity in this disease is emphasized in this study, and, although LKT is an important virulence factor of the organism, an immune response to LKT alone does not protect animals against disease.