Viruses evade the innate immune response by suppressing the production or activity of cytokines such as type I interferons (IFNs). Here we report the discovery of a mechanism by which the SARS-CoV-2 virus coopts an intrinsic cellular machinery to suppress the production of the key immunostimulatory cytokine IFN-β. We reveal that the SARS-CoV-2 encoded nonstructural protein 2 (NSP2) directly interacts with the cellular GIGYF2 protein. This interaction enhances the binding of GIGYF2 to the mRNA cap-binding protein 4EHP, thereby repressing the translation of the Ifnb1 mRNA. Depletion of GIGYF2 or 4EHP significantly enhances IFN-β production, which inhibits SARS-CoV-2 replication. Our findings reveal a target for rescuing the antiviral innate immune response to SARS-CoV-2 and other RNA viruses.

Currently, no approved antiviral therapeutic is available for treatment or prevention of Ebola virus (EBOV) infection. In this study, we characterized an EBOV-glycoprotein (GP) pseudotyped HIV-1-based vector system in different cell cultures, including human umbilical vein endothelial cells (HUVECs) and human macrophages, for the screening of anti-EBOV-GP agent(s). Based on this system, we demonstrated that an aqueous extract (CHPV) from the Chinese herb Prunella vulgaris displayed a potent inhibitory effect on EBOV-GP pseudotyped virus (EBOV-GP-V)-mediated infection in various cell lines, including HUVEC and macrophage. In addition, our results indicated that CHPV was able to block an eGFP-expressing Zaire ebola virus (eGFP-ZEBOV) infection in VeroE6 cells. The anti-EBOV activity of CHPV was exhibited in a dose-dependent manner. At a 12.5 μg/ml concentration, the CHPV showed a greater than 80% inhibition of EBOV-GP-V and eGFP-EBOV infections. Likewise, our studies suggested that the inhibitory effect of CHPV occurred by binding directly to EBOV-GP-Vs and blocking the early viral events. Interestingly, our results have shown that CHPV was able to enhance the anti-EBOV activity of the monoclonal antibody MAb 2G4 against EBOV-GP. Overall, this study provides evidence that CHPV has anti-EBOV activity and may be developed as a novel antiviral approach against EBOV infection.

c DNA viruses often target cellular proteins to modulate host cell cycles and facilitate viral genome replication. However, whether proliferation of white spot syndrome virus (WSSV) requires regulation of the host cell cycle remains unclear. In the present study, we show that two WSSV paralogs, IE1 and WSV056, can interact with Litopenaeus vannamei retinoblastoma (Rb)-like protein (lv-RBL) through the conserved LxCxE motif. Further investigation revealed that IE1 and WSV056 could also bind to Drosophila retinoblastoma family protein 1 (RBF1) in a manner similar to how they bind to lv-RBL. Using the Drosophila RBF-E2F pathway as a model system, we demonstrated that both IE1 and WSV056 could sequester RBF1 from Drosophila E2F transcription factor 1 (E2F1) and subsequently activate E2F1 to stimulate the G 1 /S transition. Our findings provide the first evidence that WSSV may regulate cell cycle progression by targeting the Rb-E2F pathway. White spot syndrome virus (WSSV), the only species of the genus Whispovirus, family Nimaviridae, is a major pathogen of shrimp. It is a large double-stranded DNA virus with a broad host range among crustaceans (1). Although WSSV was first discovered 20 years ago, the mechanism by which this virus modulates cellular pathways during infection remains to be explored.The immediate early (IE) genes of DNA viruses encode regulatory proteins critical for the initiation of primary infection and the switch from latent to lytic infection (2). Twenty-one IE genes have been identified from WSSV so far (3-5). IE1 is the most studied WSSV IE protein. It has been found to exhibit transactivation and DNA-binding activities (6), suggesting that it has a role as a transcription factor. Based on detailed mapping of IE1 promoters, progress has been made in understanding the cellular regulation of IE1 expression. Several transcription factors have been found to affect IE transcription, including shrimp homologs of STAT (7, 8), NF-B (9, 10), and a TATA box binding protein (11). JAK-STAT and NF-B pathways are believed to be critical for antiviral defense (12, 13); therefore, the findings for WSSV indicate that this virus takes advantage of the host immune system to assist its own proliferation. The biological significance of IE1 during WSSV infection was demonstrated by RNA interference experiments which revealed that depletion of IE1 strongly inhibits the replication of WSSV (11). A recent report showed that the shrimp thioredoxin PmTrx can bind to IE1 and restore its DNAbinding activity under oxidizing conditions, indicating a role for IE1 in WSSV pathogenicity (14). However, since little is known about the targets (proteins or genes) of IE1, how this viral protein functions during infection remains unknown.Interestingly, a new member of the WSSV IE proteins, WSV056 (5), is highly homologous to IE1 in its amino acid sequence, implying a potential similarity in function. Further analysis showed that both of the proteins contain a conserved LxCxE motif at the C terminus, which is characteristic of prote...