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Proceedings of the 10th International Colloquium on Paratuberculosis

Proceedings of the 10th International Colloquium on Paratuberculosis

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PPDj detected 50% <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> heifers as MAP positives at <str<strong>on</strong>g>the</str<strong>on</strong>g> first sampling, 60% at <str<strong>on</strong>g>the</str<strong>on</strong>g> sec<strong>on</strong>d<br />

sampling and less than 20% <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> last sampling date. In comparis<strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> antigen 85B<br />

(Ag85B), which share high homology with o<str<strong>on</strong>g>the</str<strong>on</strong>g>r mycobacteria such as MAA, detected 50%<br />

as positive <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> first sampling and 60% as positive <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> sec<strong>on</strong>d and third sampling. In<br />

general, <str<strong>on</strong>g>the</str<strong>on</strong>g> antigens detected <str<strong>on</strong>g>the</str<strong>on</strong>g> highest percentage <str<strong>on</strong>g>of</str<strong>on</strong>g> heifers as positives <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> sec<strong>on</strong>d<br />

and third sampling with excepti<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> PPDj. The groups <str<strong>on</strong>g>of</str<strong>on</strong>g> latency proteins and secreted<br />

proteins detected 50% to 60% as positive <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> sec<strong>on</strong>d and third sampling. Similarly, <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

three ESAT-6 family peptides (MAP160, esxH, esxU) detected 50% to 60% as positive <strong>on</strong><br />

<str<strong>on</strong>g>the</str<strong>on</strong>g> sec<strong>on</strong>d and third sampling. The two protein antigens selected as not present in MAA,<br />

detected 30% to 50% <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> heifers as positives, whereas <str<strong>on</strong>g>the</str<strong>on</strong>g> protein antigen selected from<br />

an immunological hot spot regi<strong>on</strong> detected 30% to 40% <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> heifers as positive.<br />

DISCUSSION AND CONCLUSION<br />

The IFN-� resp<strong>on</strong>ses fluctuated between <str<strong>on</strong>g>the</str<strong>on</strong>g> three sampling dates, which indicate <str<strong>on</strong>g>the</str<strong>on</strong>g> importance<br />

<str<strong>on</strong>g>of</str<strong>on</strong>g> repeated test for evaluati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> novel antigen performance in <str<strong>on</strong>g>the</str<strong>on</strong>g> IFN-� test. Surprisingly, PPDj<br />

detected less than 20% as positive <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> third sampling, but 50% to 60% at <str<strong>on</strong>g>the</str<strong>on</strong>g> first two<br />

sampling dates. For <str<strong>on</strong>g>the</str<strong>on</strong>g> majority <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> antigens, <str<strong>on</strong>g>the</str<strong>on</strong>g> highest percentage <str<strong>on</strong>g>of</str<strong>on</strong>g> positive animals<br />

was detected at <str<strong>on</strong>g>the</str<strong>on</strong>g> sec<strong>on</strong>d and third sampling dates. There is no evident explanati<strong>on</strong> for <str<strong>on</strong>g>the</str<strong>on</strong>g><br />

low percentage <str<strong>on</strong>g>of</str<strong>on</strong>g> animals detected by PPDj <strong>on</strong> <str<strong>on</strong>g>the</str<strong>on</strong>g> third sampling date and this result do not<br />

agree with <str<strong>on</strong>g>the</str<strong>on</strong>g> result for <str<strong>on</strong>g>the</str<strong>on</strong>g> majority <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> antigens. On <str<strong>on</strong>g>the</str<strong>on</strong>g> o<str<strong>on</strong>g>the</str<strong>on</strong>g>r hand, <str<strong>on</strong>g>the</str<strong>on</strong>g> observed<br />

fluctuati<strong>on</strong>s may emphasise <str<strong>on</strong>g>the</str<strong>on</strong>g> need for an alternative to PPDj in <str<strong>on</strong>g>the</str<strong>on</strong>g> IFN-� test. For<br />

optimizati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> IFN-� test well-characterised antigens should be included to induce specificity<br />

to MAP and reduce cross-reacti<strong>on</strong>s to envir<strong>on</strong>mental mycobacteria. To obtain high specificity <str<strong>on</strong>g>of</str<strong>on</strong>g><br />

<str<strong>on</strong>g>the</str<strong>on</strong>g> IFN-� test a combinati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> perhaps three novel antigens should be included. The optimal<br />

combinati<strong>on</strong> <str<strong>on</strong>g>of</str<strong>on</strong>g> novel antigens to be included in a MAP specific IFN-� test remains to be selected.<br />

ACKNOWLEDEMENTS<br />

Technicians Abdellatif El Ghazi and Sardar Ahmad have d<strong>on</strong>e most <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> ELISAs. This<br />

study was co-funded by <str<strong>on</strong>g>the</str<strong>on</strong>g> European Commissi<strong>on</strong> within <str<strong>on</strong>g>the</str<strong>on</strong>g> Sitxh Framework Programme,<br />

as part <str<strong>on</strong>g>of</str<strong>on</strong>g> <str<strong>on</strong>g>the</str<strong>on</strong>g> project ParaTBTools (c<strong>on</strong>tract no. 023106 (FOOD)).<br />

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