TWO VARIANTS OF DISK ABALONE (Haliotis discus discus) MYD88 INVOLVED IN INFLAMMATORY RESPONSES VIA NF-ΚB ACTIVATION    

Disk abalone (Haliotis discus discus) has become one of the commercially important marine gastropod species in Korean aquaculture industry. However, abalone production has been severely affected by pathogenic infections, such as bacteria, virus and parasites. Therefore, understanding about novel innate immune components, mechanisms and their responses against pathogens is vital for develop appropriate disease prevention strategies in abalone aquafarm industry. In present study, we identified two myeloid differentiation factor 88 (MyD88) molecules from disk abalone and their post innate-immune and inflammatory responses were characterized. The MyD88 is a critical adaptor in the TLR/IL-1R signaling pathway, which play an important role in immune responses via activating the NF-ΚB.

The abalone MyD88 1 and 2 (AbMyD88-1, 2) resembled typical domain structural features including characteristic N-terminal death domain and a C-terminal Toll/IL-1 receptor (TIR) domain known to be important for the functions of MyD88 in mammals. The phylogenetic analysis revealed that the AbMyD88-1 and 2 closely related to their in-vertebrate counterparts. Abalone MyD88-1 and 2 mRNA was ubiquitously expressed in all the tissues analyzed with the highest expression at muscles and hemocytes respectively. Moreover we examined the expression profiles of AbMyD88 genes at deferent developmental stages of disk abalone. The AbMyD88-1 and 2 mRNA transcripts were differentially modulated upon Vibrio parahaemolyticus, Listeria monocytogenes, viral hemorrhagic septicemia virus (VHSV), LPS and poly I:C in abalone hemocytes and gills. Overexpression of AbMyD88-1 and 2 in HEK293T cells exhibited significant activation of NF-ΚB. Thereafter, we determined their inflammatory responses by overexpressing the AbMyD88-1 and 2 in RAW264.7 murine macrophage cells. Significantly induced nitric oxide production and up-regulated expression of inflammatory marker genes, such as iNOS and cox-2 were detected in AbMyD88-1 and 2 transfected RAW264.7 cells upon LPS stimulation. Furthermore, pro-inflammatory cytokines, including IL-1ß, IL-6 and TNF-α were up-regulated in AbMyD88-1 and 2 transfected RAW264.7 cells after treatment with LPS. Collectively these observations suggest that the AbMyD88-1 and 2 involved in post-innate immune responses and inflammatory responses in abalone.