Discovery of a virus-induced Warburg effect in invertebrates

Using an in vivo multi-omics animal model to (i) characterize the key host mechanisms for virus replication and (ii) elucidate the global interactions between shrimp and WSSV, my team and our collaborative research partners were the first to discover and report on the system-level metabolic changes caused by a viral infection in invertebrates. We documented the increased glucose consumption and plasma lactate concentrations that are induced by WSSV at the genome replication stage. This switch to aerobic glycolysis is also seen in human cancer cells, where it is known as the Warburg effect. Furthermore, the WSSV-induced Warburg effect is regulated by the RAS-PI3K-Akt-mTOR pathway, and it is essential for viral replication. Based on changes in the proteome and metabolome of WSSV-infected shrimp hemocytes, we showed that several other metabolic pathways, including nucleotide biosynthesis, glutaminolysis and amino acid biosynthesis, were induced at the WSSV genome replication stage (12 hpi).

First report of virus-induced reductive glutamine metabolism in invertebrates

To better understand WSSV’s impact on shrimp aerobic glycolysis and glutamine metabolism, we then developed the first in vivo stable isotope tracing metabolomics platform for this non-model animal using labeled isotopes ([U-¹³C]glucose, [U-¹³C]glutamine and [1-¹³C]glutamine). At the virus replication stage, both classic oxidative and distinct IDH1-mediated reductive glutamine metabolism were triggered, and both were found to be crucial for viral replication. Tracking of [U-¹³C] glutamine also showed that a considerable proportion of glutamine was converted into lactate via oxidative glutamine metabolism, suggesting that the accumulation of lactate, which is the hallmark of Warburg effect, may not only be due to the increased uptake of glucose, but may also come from glutamine. Further, since the significant IDH1-mediated reductive glutamine metabolism induced by WSSV might supply the essential bio-building blocks for lipogenesis at the late stage of WSSV replication, we are currently investigating the effects of suppressing the IDH1-mediated reductive glutamine metabolic pathway in the selection and breeding of WSSV-resistant shrimp.

A comprehensive model of how AHPND-causing bacteria affect shrimp stomach and hepatopancreas

Based on our scientific findings between 2017 and 2022 we proposed the comprehensive model of AHPND pathogenesis: 1. The shrimp stomach is composed of epithelial cells, a mucus layer (or cuticle) and a lumen with gut microbiota. AHPND-causing V. parahaemolyticus enter the shrimp stomach through an oral route. 2. The pathogen releases metabolites into the lumen, causing dysbiosis of gut microbiota. 3. As a first line of defense, the host secretes more bile acid into the stomach lumen. 4. Increased bile acid in the stomach induces protective biofilm formation by V. parahaemolyticus and the release of PirAB^VP toxins into the lumen. 5. Colonizing bacteria may disrupt the cuticle layer, stimulating an exaggerated immune response and Rho activation in shrimp stomach epithelial cells. 6. Activation of the Rho-signaling pathway disrupts stomach epithelial cell tight junctions. Formation of intercellular gaps enables PirAB^VP toxins and bacteria to pass into the hepatopancreas. In addition, PirAB^VP toxins interact with hemocytes by binding with APN1 and causing cell lysis. The proPO-mediated over-immune response is triggered, causing sloughing of hepatopancreatic cells.