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Proceedings of the 10th International Colloquium on Paratuberculosis

Proceedings of the 10th International Colloquium on Paratuberculosis

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#213 C<strong>on</strong>structi<strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> auxotrophic leuD mutant <str<strong>on</strong>g>of</str<strong>on</strong>g> Mycobacterium avium subspecies<br />

paratuberculosis K10 as a live attenuated vaccine candidate<br />

Jenn-Wei Chen, Subhash Chandra, Tzu-Yi Ma, Maria A. P. Moreira, Yung-Fu Chang, College <str<strong>on</strong>g>of</str<strong>on</strong>g> Veterinary<br />

Medicine, Cornell University, USA<br />

Background: Mycobacterium avium subspecies paratuberculosis is an obligate pathogenic bacterium in <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

genus Mycobacteria. It is intracellular pathogens and reside inside host cells primarily macrophage. MAP<br />

causes Johne’s disease in cattle and o<str<strong>on</strong>g>the</str<strong>on</strong>g>r ruminants, and is resp<strong>on</strong>sible for an ec<strong>on</strong>omy loss to dairy industry.<br />

It has l<strong>on</strong>g been suspected as a causative agent in Crohn’s disease in humans, although this c<strong>on</strong>necti<strong>on</strong><br />

is c<strong>on</strong>troversial. It is urgently needed to develop a vaccine with a better protecti<strong>on</strong> and fewer side effects. We<br />

have c<strong>on</strong>structed a live attenuated MAP leuD mutant as a live vaccine candidate.<br />

Methods: A phage-mediated allelic exchange technique was used to delete leuD gene. The MAP leuD<br />

gene deleti<strong>on</strong> was c<strong>on</strong>firmed by both PCR and DNA sequence. The complementati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> leuD by pVV16-leuD<br />

vector abolished its leucine requirement for growth. Mice were used to perform a vaccine trial.<br />

Result: C57BL/6 mice were used to determine <str<strong>on</strong>g>the</str<strong>on</strong>g> pathogenicity <str<strong>on</strong>g>of</str<strong>on</strong>g> MAP LeuD mutant. We found that<br />

mice infected with wild type <str<strong>on</strong>g>of</str<strong>on</strong>g> MAP with a larger liver and spleen than that <str<strong>on</strong>g>of</str<strong>on</strong>g> leuD mutant. Histopathological<br />

examinati<strong>on</strong> also showed <str<strong>on</strong>g>the</str<strong>on</strong>g> leuD mutant strain infected mice have a mild inflammati<strong>on</strong> in spleen and liver<br />

than that <str<strong>on</strong>g>of</str<strong>on</strong>g> wild type. Preliminary data also indicated that <str<strong>on</strong>g>the</str<strong>on</strong>g> leuD mutant could induce protecti<strong>on</strong> against<br />

challenge in a mouse model.<br />

C<strong>on</strong>clusi<strong>on</strong>: Management <str<strong>on</strong>g>of</str<strong>on</strong>g> Johne’s disease has been a challenge to farmers. We c<strong>on</strong>structed auxotrophic<br />

leuD mutant <str<strong>on</strong>g>of</str<strong>on</strong>g> MAP K10 as a live attenuated vaccine candidate which could induce a better protecti<strong>on</strong><br />

against MAP infecti<strong>on</strong>. Based <strong>on</strong> our preliminary mouse study, this new vaccine candidate may be used as<br />

a live attenuated vaccine against Johne’s disease.<br />

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