Two Litopenaeus vannamei HMGB proteins interact with transcription factors LvSTAT and LvDorsal to activate the promoter of white spot syndrome virus immediate-early gene ie1

White spot syndrome virus (WSSV) has caused great economic damage to shrimp aquaculture. Previous studies have shown that WSSV successfully usurps the immunity system of the host for its own gene regulation. To investigate the role of shrimp high mobility group box (HMGB) proteins in WSSV gene regulation, two Litopenaeus vannamei HMGB genes, LvHMGBa and LvHMGBb, were isolated by rapid amplification of cDNA ends (RACE). Recombinant LvHMGBa/b proteins were present in the nucleus of transfected Drosophila Schneider 2 (S2) cells. Luciferase reporter assays revealed that LvHMGBa/b upregulated the WSSV immediate-early (IE) gene (ie1) in a NF-κB and STAT binding site-dependent manner. GST pull-down assays demonstrated that LvHMGBa/b interacted with L. vannamei Dorsal (LvDorsal) and L. vannamei STAT (LvSTAT), respectively. LvHMGBa was highly expressed in hepatopancreas while HMGBb was highly expressed in stomach, intestine, heart, antennal gland, and epidermis. Moreover, an immune challenge assay demonstrated that the expression of LvHMGBa/b was upregulated by WSSV infection and that both mRNAs reached peak values at 24 h post-infection. To our knowledge, this is the first report that invertebrate HMGB proteins participates in viral gene regulation.