Preliminary investigations into ostrich mycoplasmas : identification of vaccine candidate genes and immunity elicited by poultry mycoplasma vaccines

[摘要] ENGLISH ABSTRACT: Ostrich farming is of significant economical importance in South Africa. Three ostrich mycoplasmas,Ms01, Ms02 and Ms03 have been identified previously, and were provisionally named 'Mycoplasmastruthiolus' (Ms) after their host Struthio camelus. Ostrich mycoplasmas are the major causativeorganisms of respiratory diseases, and they cause stock losses, reduced production andhatchability, and downgrading of carcasses and therefore lead to large economic losses to theindustry. In order to be pathogenic to their host, they need to attach through an attachmentorganelle, the so-called tip structure. This structure has been identified in the poultry mycoplasma,M. gallisepticum, and is made up of the adhesin GapA and adhesin-related CrmA. Currently, noostrich mycoplasma vaccine is commercially available and for this reason the need to develop onehas arisen. Therefore the first part of this study was dedicated to the identification and isolation ofvaccine candidate genes in the three ostrich mycoplasmas. Four primer approaches for polymerasechain reactions (PCR's), cloning and sequencing, were used for the identification of adhesin oradhesin-related genes from Ms01, Ms02 and Ms03. The primer approaches revealed that the targetgenes could not be identified due to the high diversity of sequences that were generated. Thereforesequences were also compared with those of other mycoplasma species in BLAST searches.Results showed that the most significant hit was with the human pathogen M. hominis oppD, whichis located in the same operon as the membrane protein P100 involved in adhesion. Other hits werewith ABC transporters which may also play a role in cytadhesion.The second part of this study was aimed at testing whether two poultry mycoplasma vaccines, M.synoviae and M. gallisepticum, can be used in ostriches to elicit immune responses until an ostrichmycoplasma vaccine has been developed. Ostriches on three farms of different age groups in theOudsthoorn district were therefore vaccinated with these vaccines in a vaccine trial. The enzymelinkedimmunosorbent assay (ELISA) was used to test the level of antibody response. Resultsshowed that both vaccines elicited an immune response in all three age groups. A high percentageof the ostriches reacted positively, which indicates that both vaccines elicit antibody responses andmay therefore give protection against ostrich mycoplasma infections.

[发布机构] Stellenbosch University