Studies on immune responses to Bordetella avium in turkeys

Abstract

Systemic and mucosal humoral immune responses to an experimental B. avium infection were evaluated by using an ELISA technique. The three isotypes of immunoglobulin, IgG, IgA and IgM, were detected in serum, tracheal washings and lacrimal secretions in response to an intra-nasal and intraocular bacterial challenge of 1-day-old turkeys. The IgM response was the earliest, starting at 2 weeks and reaching a peak at 4-5 weeks after infection. The IgA response was early, steady and lower in comparison. The IgG response was prominent and long lasting. The IgG response started at 3 weeks, reached a peak at 5-6 weeks and slowly declined by 8 weeks. The total immune response declined by 8 weeks as the clearance of 6. avium approached completion. In this study, the cumulative antibody titers closely corresponded with decreasing numbers of bacteria. The transfer of parenterally administered IgG was assayed in turkeys using 8. avium specific IgG and ELISA as a model. Purified IgG, specific to B. avium was injected and samples of serum and tracheal washings were collected and assayed by ELISA at various time intervals. The IgG intravenously injected was detected in tracheal washings as early as 5 minutes PI, with peak levels occuring 10 minutes post-injection (PI). A rapid decline in serum IgG from 10 to 60. minutes PI was followed by a more gradual decline to baseline levels by 24 hours PI. The levels of IgG in serum, tracheal washings and lacrimal secretions were closely corresponding after 10 minutes PI. These results indicate rapid transfer of IgG from the blood to viii mucosal secretions. The role of parenterally administered IgG in the colonization and clearance of B. avium from the tracheal surface was assayed. The IgG prevented colonization and also aided in the clearance of B. avium from the tracheal surface. This study showed that IgG, transferred from the bloodstream to mucosal surfaces, could inhibit colonization and promote clearance of infection. A monoclonal antibody based-latex bead agglutination test was developed to differentiate B. avium from 6. branchiseptica and B. avium-iiiie bacteria. All 40 isolates of B. avium tested showed a positive reaction with this test. None of the 24 S. avium-Wke isolates showed a positive reaction. Out of 17 B. bronchiseptica isolates, two had minor cross reactions. Manuscript for submission to Avian Diseases.