Development of an oral vaccine against the ostrich-specific mycoplasma, Mycoplasma struthionis

Van Tonder, Amanda (2013-03)

Thesis (MSc-)--Stellenbosch University, 2013.

Thesis

ENGLISH ABSTRACT: The ostrich-specific mycoplasmas Mycoplasma struthionis, Ms02 and Mycoplasma nasistruthionis, are associated with respiratory disease in ostriches, which is threatening the South African ostrich industry. Antibiotics are available to manage Mycoplasma infections, but a need to prevent infections led to an investigation into the development of vaccines against the ostrich-specific mycoplasma. After commercially available poultry mycoplasma vaccines proved to be unsuccessful in protecting ostriches against ostrich mycoplasma infections, the genome of M. struthionis was analysed and the OppA gene identified as a good vaccine candidate. The gene was isolated and used to develop the pCI-neo, VR1012 and VR1020 naked DNA vaccines. M. struthionis infects the respiratory tract of ostriches, therefore a vaccine that results in mucosal immunity is required. The use of a bacterial vector for DNA vaccines has been shown to elicit both a humoral and mucosal immune response. Salmonella enterica serovar typhimurium SL3261 was used to develop mucosal pCI-neo, VR1012 and VR1020 DNA vaccines. The pCI-neo mucosal DNA vaccine was found to be unstable in vivo and the stable mucosal VR1020 and VR1012 DNA vaccines were considered for subsequent vaccine trials. The tissue plasminogen activator (TSA) signal peptide found in the VR1020 plasmid to direct the secretion of the membrane protein, OppA, makes it a good candidate vaccine to compare against the naked DNA vaccine. A preliminary vaccine trial conducted with this vaccine was influenced by various factors including avian influenza and the statistical results proved to be invalid, but enzyme-linked immunosorbent assays (ELISAs) were developed for the successful measurement of the immune response of the ostriches. The dose of the mucosal vaccine administered in the preliminary trial might not have been enough to elicit an effective immune response in the ostriches. Different doses of the mucosal VR1012 and VR1020 DNA vaccines were therefore used in a second trial, but the trial was also influenced by a variety of factors. Even though the results of the vaccine trials were not successful, a few observations were made that could be used to improve future trials and reduce the effect of the factors on the vaccine trials, such as the effect of prior infection, as well as the stress on the ostriches.

AFRIKAANSE OPSOMMING: Die volstruis-spesifieke mikoplasmas, Mycoplasma struthionis, Ms02 en Mycoplasma nasistruthionis, word geassosieer met lugweg infeksies in voltruise, wat die Suid-Afrikaanse volstruisbedryf bedreig. Antibiotika is beskikbaar om mikoplasma infeksies te beveg, maar 'n wyse om infeksie te voorkom word benodig. Dus is 'n ondersoek geloods om effektiewe entstowwe te ontwikkel teen die volstruis mikoplasmas. Na die onsuksesvolle poging om pluimvee mikoplasma entstowwe, wat kommersiëel beskikbaar is, te gebruik om volstruise te beskerm teen volstruis mikoplasma infeksie, is die genoom van M. struthionis ondersoek en is die OppA geen geïdentifiseer as 'n entstof kandidaat. Die geen is geïsoleer en gebruik om die pCI-neo, VR1012 en VR1020 deoksiribonukleïensuur (DNS) entstowwe te ontwikkel. M. struthionis veroorsaak infeksie in die respiratoriese kanaal van volstruise, daarom moet die entstof lei tot 'n mukosale immuunrespons. Omrede daar al bewys is dat 'n bakteriële vektor, as draer van 'n DNS entstof, kan lei tot 'n humorale sowel as 'n mukosale immuunrespons, is Salmonella enterica serovar typhimurium SL3261 gebruik om mukosale pCI-neo, VR1012 en VR1020 DNS entstowwe te ontwikkel. In vivo was die mukosale pCI-neo DNS entstof onstabiel. Die stabiele mukosale VR1012 en VR1020 DNS entstowwe is gebruik vir die daaropvolgende entstof proewe. Die VR1020 plasmied bevat 'n weefsel plasminogeen aktiveerder seinpeptied wat die sekresie van die membraan protein, OppA, lei, wat dit 'n goeie kandidaat maak om te vergelyk met die skoon DNS entstof. 'n Verskeindenheid faktore, insluitend voëlgriep, het die voorlopige entstof proef, wat uitgevoer is met hierdie entstof, beïnvloed en daar was te veel variasie in die statistiese resultate om tot 'n gevolgtrekking oor elkeen van die entstowwe te kom. Die ensiem-gekoppelde immunosorberende toets wat ontwikkel is, was suskesvol daarin om die imuunrespons van die volstruis te meet. Die dosis van die mukosale entstof wat gebruik is in die voorlopige entstof proef, was dalk nie genoeg om 'n doeltreffend imuunrespons in die volstruise te ontlok nie. Verskillende dosisse van die mukosale VR1012 en VR1020 DNS entstowwe is dus gebruik in 'n tweede entstof proef, maar die entstof proef is ook beïnvloed deur verskeie faktore. Alhoewel die resultate van die entstof proewe nie na verwagting was nie, is observasies gemaak om toekomstige proewe te verbeter, soos om die effek van vorige infeksies, sowel as spanning op die volstruise te verminder.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/79834
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