Effets des immunostimulants sur la réponse immunitaire et la régulation de l'expression des TLR chez un poisson-chat asiatique, Pangasianodon hypophthalmus

Abstract

Pangasianodon hypophthalmus is an economically important Asian catfish and it is subjected to the well known aquaculture risk of bacterial infection (Edwarsiella ictaluri in this case). What is the reason why we studied, in this work, the effects of immunostimulants on the immune response and the regulation of TLR expression. Like all Teleostei, P. hypophthalmus presents during a pathogen attack an innate and an adaptative immune response, the first predominating the second. This response may be activated only by the previous recognition of pathogen by receptors, which the most important family is the Toll-like Receptors one (TLR). They are able to recognize a series of Pathogen Associated Molecular Patterns (PAMPs), of which the lipopolysaccharid (LPS), an essential constituent of the Gam negative bacterial cell wall. The use of this molecule as an immunostimulant may constitute an alternative to the use of antibiotics in P. hypophthalmus aquaculture. In this perspective, the objectives of this work are: 1°) assessing to which extent immunostimulants enhance the immune response of P. hypophthalmus and regulate TLR expression, 2°) verifying whether immunostimulants protect P. hypophthalmus against pathogens, and 3°) assessing how much time the protection is effective. According to our results and the current scientific literature, LPS doesn't seem to enhance the efficiency of P. hypophthalmus immune response during an E. ictaluri challenge test, so it doesn't constitute an effective protection against pathogens. According to the no completed condition of the TLR expression manipulation, we don't conclude regarding the action of immunostimulant like LPS on these ones.

Date of Award	2010
Original language	French
Supervisor	Patrick Kestemont (Supervisor) & Nguyen Thanh Phuong (Supervisor)