Efficacy of Vaccination of Calves against Hemorrhagic Septicemia with a Live aroA Derivative of Pasteurella multocida B:2 by Two Different Routes of Administration

Abstract

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.Hemorrhagic septicemia (HS) caused by infection with Pasteurella multocida serotype B:2 is a commonly fatal systemic disease of cattle and buffaloes in countries of South and Southeast Asia (3, 22). The disease is peracute, having a short clinical course involving severe depression, pyrexia, submandibular edema, and dyspnea, followed by recumbency and death. Some control is achieved with alum-precipitated or oil adjuvant broth bacterins injected subcutaneously, but these vaccines have the disadvantage of providing only short-term immunity (4 to 6 months and up to 1 year for alum adjuvant and oil adjuvant vaccines, respectively) (21), and the high viscosity of oil adjuvant vaccines makes them unpopular among field users. The disease remains a significant obstacle to sustainable agriculture in the region, and in attempts to elicit longer-term immunity, live vaccines have been developed (14), although they have been ill defined and of questionable safety. On the other hand, a marker-free aroA deletion derivative (strain JRMT12) of a virulent field isolate of P. multocida B:2 (strain 85020) obtained from Sri Lanka has been shown to be attenuated and to confer a high degree of protection when used as a live vaccine in a mouse model of hemorrhagic septicemia (19). The construct is particularly suited to be a live vaccine candidate, as it possesses no...

Safety and Protective Efficacy of Intramuscular Vaccination with a LivearoADerivative ofPasteurella multocidaB:2 against Experimental Hemorrhagic Septicemia in Calves

“…The apparent association of different mean IgM titers with groups preceded any differences in treatment and was coincidental. There was no significant increase in either serum IgG or IgM concentrations during the days following primary vaccination with any of the vaccine doses, in agreement with our previous work (12) and with the observations of others (4,13,20). If anti-P. multocida serogroup A:3 IgM antibody was present, it may have reacted with the vaccine dose, a phenomenon reported previously (2), thereby reducing the titer, as seen at day 14, and thus minimizing the humoral response to vaccination.…”

“…with ca. 10 9 CFU of the P. multocida JRMT12 strain peaked at 24 h postvaccination and then declined (12), and a similar trend was also apparent in the present experiment after vaccination with 10 8 CFU. The low mean SAA concentrations and the lack of any significant differences in concentrations among the vaccinated groups after challenge suggest that vaccination with any of the three vaccine preparations was of similar efficacy in reducing the acute-phase protein response.…”

“…The lack of significant difference between the V1 and V2 groups was probably due to the administration of flunixin meglumine to group V1 calves. This was used previously (12) to reduce an anticipated risk of endotoxic shock at the high vaccination dose. A preparation of live gram-negative bacteria in the log phase of growth, such as the JRMT12 strain used in this study, will contain free endotoxin (19) in amounts proportional to the number of bacteria present, but attempts to remove the endotoxin by washing the bacteria in PBS followed by centrifugation were of little success and significantly reduced the viability of the preparation (J. C. Hodgson, unpublished observation).…”

“…Recently, we evaluated the efficacy of a live attenuated vaccine against experimental HS in calves, using a marker-free aroA deletion derivative of a virulent field isolate of P. multocida B:2 obtained from Sri Lanka (12). Calves that were immunized intramuscularly (i.m.)…”

Biochemical and proteomic investigation of bovine nasal secretion

“…Boosmann et al (1989 have shown that bovine SAA, increases 100-fold in cattle inoculated experimentally with E. coli LPS toxins. Other experimental studies have measured the SAA response in cattle following inoculation of pathogens associated with BRD like M. haemolytica (Horadagoda et al, 1993), bovine respiratory syncytial virus (BRSV) (Heegaard et al, 2000) and P. multocida (Hodgson et al, 2005). Serum amyloid-A was observed to be a sensitive APP that reacts faster than Hp following infections (Alsemgeest et al, 1994 andHoradagoda et al, 1994).…”