Immune and bacterial toxin genes expression in different giant tiger prawn, penaeus monodon post-larvae stages following AHPND-causing strain of vibrio parahaemolyticus challenge

Abstract

Acute Hepatopancreatic Necrosis Disease (AHPND), a disease caused by Vibrio parahaemolyticus (VpAHPND), kills Penaeid shrimps worldwide, resulting in severe economic losses during aquaculture. To further understand how Penaeus monodon post-larvae (PL) respond towards infection of this pathogenic bacterium, the expression of several important immune and bacterial toxin genes in three stages of P. monodon PL (PL15, PL30 and PL45) upon VpAHPND challenge, were determined. A 20-hrs challenge test with 2.7 × 107 cfu ml−1 of VpAHPND resulted 81, 65 and 1.7% mortality respectively for PL30, PL15 and PL45, indicating that PL30 was most vulnerable to VpAHPND. The immune response of shrimp PL at this stage was robust, with Toll-like receptor (TLR), prophenoloxidase (proPO), lysozyme (lyso) and penaeidin (PEN) augmented approximately 10.7, 4.7, 6.5 and 3.2-fold, respectively. The expression initiated at one hour post-infection (h.p.i), peaked at 16 h.p.i and 20 h.p.i, and decreased at 18 h.p.i, indicating the crucial involvement of these immune related genes in the defence and recovery of the first-line defence mechanisms during VpAHPND infection. This work also revealed that toxR gene represents a good indicator gene for Vibrio detection whereas PIR A, for VpAHPND pathogenicity determination of P. monodon. Overall, these findings provided novel insights into the immune response and VpAHPND susceptibility of different P. monodon PL stages during infection, with outcomes potentially useful in enhancing the application of health therapy and biosecured aquaculture practices to minimize the damaging risk of AHPND towards sustainable production of P. monodon. Keywords: Penaeus monodon, AHPND, PIR a, Immunity genes, Bacterial toxin gene