COMPARATIVE-EVALUATION OF ANTIBODIES INDUCED BY COMMERCIAL PASTEURELLA-HAEMOLYTICA VACCINES USING SOLID-PHASE IMMUNOASSAYS

The objective of this Study was to evaluate the ability of four commer cial vaccines to elicit antibodies against the leukotoxin (Lkt), capsu lar polysaccharide (CP), iron regulated outer membrane proteins (IROMP s), and whole cell (WC) antigens of Pasteurella haemolytica Al. Modifi ed double antibody sandwich enzyme linked immunosorbent assays (ELISAs ) were developed to measure antibody levels against Lkt, CP and IROMPs , An indirect ELISA was developed to measure the levels of antibody ag ainst WC antigens. The ideal cut off points for ELISAs were determined on receiver operating characteristic curves, using sera from 30 calve s injected subcutaneously with a live P. haemolytica 12296 strain as p ositive control and sera from 30 colostrum-deprived calves as negative control. The vaccines evaluated were: 'One Shot' (SmithK-line Beecham , West Chester, PA) a bacterin-toxoid, 'Presponse' (Langford Laborator ies, Guelph, Ontario) a Lkt-rich culture supernatant, 'Once PMH' (BioC or Inc., Omaha, NE) a modified live vaccine, and 'Septimune' (Fort Dod ge laboratories, Fort Dodge, IA) an outer membrane extract. Thirty, 4- 6 week old Holstein calves were randomized into 5 groups to receive on e of the four vaccines or a placebo (sterile phosphate buffered saline ). The calves were vaccinated intramuscularly on day 0 and on day 14, and bled on days 0, 14, and 28 to measure antibody levels against Lkt, CP, IROMPs, and WC antigens of P. haemolytica Al. 'One Shot', and 'On ce PMH' vaccinates showed a significant (P < 0.05) increase in antibod y levels against Lkt at 28 days. 'Once PMH' vaccinates also showed sig nificant (P < 0.05) increase in antibody levels against IROMPs at 28 d ays compared to the other four groups but this increase was not signif icant over time within the 'Once PMH' group. 'Presponse', 'Once PMH', and 'One Shot' vaccinates showed a significant (P < 0.05) increase in antibody levels against CP over time. These groups also had significan tly higher antibody levels against CP, compared to controls and 'Septi mune' vaccinates at 14 and 28 days (P < 0.05).