HEAT SHOCK PROTEIN ENHANCES RESISTANCE TO A STRAIN OF Vibrio parahaemolyticus WHICH CAN CAUSE ACUTE HEPATOPANCREATIC NECROSIS DISEASE (AHPND) BY ACTIVATING SHRIMP IMMUNITY

Acute hepatopancreatic necrosis disease (AHPND) caused by the bacterium Vibrio parahaemolyticus carrying toxin producing plasmid (VP_AHPND), has led to severe mortalities in farmed penaeid shrimp throughout Asia. Our studies reported that a chronic non-lethal heat shock (chronic-NLHS) could enhance Penaeus vannamei to be tolerant to VP_AHPND infection. The results showed that the shrimp exposed to chronic NLHS had higher survival rate (>50%) than that of the non-heated shrimp control (20%) when they were challenged with VP_AHPND. Furthermore, the qRT-PCR analysis revealed that the expression of heat shock proteins, LvHSP70 and LvHSP90, as well as other immune-related genes, LvproPO1 and LvCrustin1, were induced upon exposure of shrimp to chronic NLHS. Moreover, gene silencing of LvHSP70 and LvHSP90 eradicated the VP_AHPND tolerance in the chronic NLHS shrimp and decreased PO activity. The recombinant LvHSP70 (rLvHSP70) was successfully overexpressed in E. coli system and dose dependent (1.0 nmol) of rLvHSP70 injection induced the expression of several immune-related genes (LvMyD88, LvIKKε, LvIKKβ, LvCrustin1, LvPEN2, LvPEN3, LvproPO1, LvproPO2, and LvTG1) in the shrimp immune system. Interestingly, rLvHSP70 enhances P. vannamei resistance to VP_AHPND infection increasing survival rate from 20% (control group) to >75%. These results suggested that LvHSP70 plays crucial roles in bacterial defense by activating shrimp immune system.