White spot syndrome virus IE1 protein hijacks the host pentose phosphate pathway to fuel viral replication.

Viruses frequently reprogram host metabolism to support their replication. The pentose phosphate pathway (PPP), a key regulator of nucleotide synthesis and redox balance, is often targeted during infection. While PPP activation is well-known proviral mechanism in vertebrates, how this process occurs in invertebrate hosts remains unclear. Here, using the white spot syndrome virus (WSSV) and its penaeid shrimp host as a model, we identify a previously unrecognized viral strategy that directly reprograms the PPP through host-viral protein interaction. WSSV infection strongly induced the expression of key PPP enzymes, including glucose-6-phosphate dehydrogenase (G6PD) and transketolase-like 2 (TKTL2), and enhanced TKTL2 enzymatic activity. This activation increased the production of nicotinamide adenine dinucleotide phosphate (NADPH) and ribose-5-phosphate (R5P), two critical PPP metabolites. Functional assays confirmed that the PPP is essential for efficient WSSV replication, as knockdown or pharmacological inhibition of G6PD or TKTL2 significantly attenuated viral load and improved host survival. Mechanistically, the viral immediate-early protein IE1 was found to directly bind to the C-terminal region of TKTL2 (TKTL2-C1, residues 500-555), and enhance its enzymatic activity. This interaction promoted PPP flux, boosted NADPH and R5P biosynthesis, and suppressed reactive oxygen species (ROS) accumulation. Supplementation with NADPH, R5P, or a ROS scavenger restored viral replication defects caused by IE1 knockdown. Moreover, the IE1-binding fragment TKTL2-C1 acted as a competitive inhibitor that disrupted the IE1-TKTL2 interaction, decreased PPP flux, and reduced viral replication. Together, these findings demonstrate that WSSV IE1 directly activates host TKTL2 to rewire pentose phosphate metabolism, revealing a novel metabolic mechanism of viral pathogenesis and identifying the PPP as a potential target for antiviral intervention in aquaculture.