Protection of budgerigars (Melopsittacus undulatus) against Chlamydophila psittaci challenge by DNA vaccinationTaher Harkinezhad, Katelijn Schautteet and Daisy Vanrompay
Department of Molecular Biotechnology, Ghent University, Faculty of Bioscience Engineering, Coupure Links 653, 9000 Ghent, Belgium
Received 28 January 2009; accepted 29 July 2009; published online 30 July 2009
Abstract - Plasmid DNA (pcDNA1::MOMP A) expressing the major outer membrane protein (MOMP) of Chlamydophila psittaci genotype A strain 89/1051 has been tested for its ability to induce protective immunity against Cp. psittaci challenge in budgerigars. Eight pairs of male and female budgerigars were housed in eight separate bird cages placed in two negative pressure isolators, four cages per group. All budgerigars were immunised twice intramuscularly with 100 g plasmid DNA. Both groups received a primary DNA inoculation at day 0 followed by a booster inoculation 3 weeks later. Group 1 received pcDNA1::MOMP A, while group 2 received the placebo vaccine pcDNA1. Budgerigars were challenged by aerosol 2 weeks following the booster vaccination. The challenge consisted of 108 TCID50 of the homologous Cp. psittaci genotype A strain. Cloacal and pharyngeal swabs of all budgerigars, taken prior to the experimental infection were negative in both PCR and culture. However, all budgerigars showed low pre-existing serum antibody titres. This indicates that animals were previously infected. Nevertheless, DNA immunisation could significantly reduce clinical signs, macroscopic lesions, pharyngeal and cloacal excretion as well as chlamydial replication, even in the presence of pre-existing serum antibodies, as compared to the placebo-vaccinated controls.
Key words: Chlamydophila psittaci / budgerigar (Melopsittacus undulatus) / DNA vaccination / MOMP
Corresponding author: Katelijn.Schautteet@UGent.be
© INRA, EDP Sciences 2009