Mycoplasma gallisepticum (MG) is an important pathogen of poultry worldwide that causes chronic respiratory disease (CRD) in chickens and infectious sinusitis in turkeys. Vaxsafe MG (strain ts-11) is a live attenuated temperature sensitive vaccine that has been proven to be effective in controlling CRD in chickens, but it is not efficacious in turkeys. The gapA gene, which encodes a mature cytadhesin protein with a molecular weight of approximately 105 kDa, is not expressed in strain ts-11 because a 20 base pair reiterated sequence introduces a frame shift and causes premature truncation of the translated peptide. A GapA positive clone, MG ts-304, isolated from strain ts-11 has been shown to have enhanced efficacy in chickens. Here we describe studies we conducted to assess the safety and efficacy of the MG ts-304 vaccine candidate in turkeys. We found that MG ts-304 was able to colonise the trachea of 3-week-old turkeys and was safe, even at a tenfold overdose, inducing no adverse clinical signs of respiratory disease or significant gross lesions in the respiratory tract (air sacs or trachea), and was poorly transmissible to in-contact birds. We also showed that it was efficacious when administered to 3-week-old turkeys, inducing protective immunity against challenge with the M.gallisepticum wild-type strain Ap3AS. MG ts-304 is therefore a promising live attenuated vaccine candidate for use in turkeys.
Keywords: GapA; Mycoplasma gallisepticum; Mycoplasmosis; Turkeys; Vaccine; ts-304.
Copyright © 2018. Published by Elsevier Ltd.