Glucose And Mannose Analogs Inhibit KSHV Replication By Blocking NGlycosylation And Inducing The Unfolded Protein Response

SCHLESINGER, MARIANA; ANUJ AHUJA; MCDONALD, CHRISTIAN; ALVAREZ CANETE, CAROLINA ALEJANDRA; NUÑEZ DEL PRADO, ZELMIRA; JULIÁN NAIPAUER; LAMPIDIS, THEODORE; ENRIQUE A. MESRI

Conferencia; 24th International KSHV Conference 2022; 2022

Kaposi’s sarcoma-associated herpesvirus (KSHV) is the etiological agent for Kaposi’s sarcoma (KS), an HIV/AIDS-associated malignancy. Effective treatments against KS remain to be developed. The sugar analog 2-deoxy-glucose (2-DG) is an anti-cancer agent that is well-tolerated and safe in patients and was recently demonstrated to be a potent antiviral against KSHV and SARS-CoV-2. A better understanding of the cellular mechanisms affected by 2-DG could offer new avenues for innovative therapies against KSHV. However, because 2-DG inhibits glycolysis and N-glycosylation, identifying its molecular targets is challenging. Additionally, induction of ER stress by 2-DG seems to be a promising strategy against KSHV. For these reasons, we aimed to compare the antiviral effect of 2-DG to 2-fluoro-deoxy-d-glucose (2-FDG), a glycolysis inhibitor, and 2-deoxy-fluoro-d-mannose (2-DFM), a specific N-glycosylation inhibitor. At doses similar to those clinically achievable with 2DG, the three drugs impair KSHV replication and virion production in iSLK.219 cells via down-regulation of viral structural glycoprotein expression (K8.1 and gB), 2-DFM the most potent KSHV inhibitor. Consistently with the higher potency of 2-DFM, we found that D-mannose rescues KSHV glycoprotein synthesis and virus production, indicating that inhibition of N-glycosylation is the main antiviral target of the sugar analogs. We also demonstrated that suppression of N-glycosylation by the sugar analog drugs triggers ER stress and activates the host unfolded protein response (UPR), counteracting KSHV-induced inhibition of the PERK branch, particularly ATF4 and CHOP expression. Finally, we found that these sugar analogs induce autophagy (a pro-survival mechanism) and, thus, inhibit viral replication which plays a protective role against KSHV-induced cell death. This evidence supports their direct antiviral effect and potential therapeutic use. In summary, our work identifies the inhibition of N-glycosylation leading to ER stress and UPR activation as an anti-enveloped virus target, and sugar analogs such as 2DG and the newly identified 2-DFM as antiviral drugs.