L5P: news development for specific sero-diagnosis of Mycobacterium avium subsp. paratuberculosis infection
Résumé
Background: Unlike other MAC members, Mycobacterium avium subsp. paratuberculosis does not produce the GPL on the surface of the cell wall but a lipopentapeptide called L5P or LP01. The molecular and genetic characterization of this antigen demonstrated that L5P is specific to Mycobacterium avium subsp. paratuberculosis. L5P produced by chemical synthesis was used to show that this molecule is suitable to detect Mycobacterium avium subsp. paratuberculosis infected animals. Currently available diagnostic tests are based on the use of whole cell antigen that are mainly not Mycobacterium avium subsp. paratuberculosis specific and that require a pre-absorption step with antigen of Mycobacterium phlei. These diagnostics detect animals with a late infection but are not sensitive enough to detect early infection. We hypothesize that the pre-absorption step prevents detection of informative populations of immunoglobulins, especially in animals with “asymptomatic shedding” not detected by the current serology-based diagnostics.
Objective: Assess the potential of L5P and soluble variants for the serological diagnosis of Mycobacterium avium subsp. paratuberculosis infection using collections of sera from different contexts.
Method: In order to find the best compound for use in serology we chemically synthesized L5P and derivatives of L5P including water-soluble forms. These pure compounds were evaluated on three collections of serum, each well characterized from infected and non-infected cattle, goats and sheep.
Results: ROC analysis showed that L5P and also water-soluble derivatives are suitable for the development of a serological diagnostic test. Advantageously, these pure synthetic Mycobacterium avium subsp. paratuberculosis specific antigens can be produced at low cost.