Marion Cannac

Flaviviruses are positive-sense RNA viruses that rely entirely on host translation machinery to express their genome, making protein synthesis a central point of vulnerability. Interferon-stimulated genes (ISGs) exploit this dependence through diverse and mechanistically distinct strategies. PKR and IFIT proteins interfere primarily with translation initiation by targeting initiation factors or cap recognition, whereas SLFN11 and SAMD9L impair elongation through codon- and tRNA-dependent mechanisms. In parallel, ZAP, SHFL, and ISG20 inhibit translation by excluding viral RNAs from ribosomes or promoting their degradation. These antiviral activities highlight that ISG-mediated restriction is often highly selective, targeting viral RNAs on features such as cap structure, nucleotide composition, codon usage, and RNA folding. As a result, translation emerges as a central interface of host–virus conflict, where subtle differences between viral and cellular mRNAs can be exploited to achieve potent antiviral effects while preserving host protein synthesis. This minireview highlights recent advances in the identification and characterization of ISGs that restrict flavivirus protein synthesis and integrates them into a unified framework based on their primary mechanism of action. Emphasizing how host defenses target multiple stages of translation provides a conceptual basis for understanding how innate immunity controls flavivirus replication and highlights viral translation as a promising target for selective antiviral strategies.

Médecine/sciences (M/S), revue internationale dans le domaine de la recherche biologique, médicale et en santé

Usutu virus (USUV) and West Nile virus (WNV) are two closely related emerging mosquito-borne flaviviruses. Their natural hosts are wild birds, but they can also cause severe neurological disorders in humans. Both viruses are efficiently suppressed by type I interferon (IFN), which interferes with viral replication, dissemination, pathogenesis and transmission. Here, we show that the replication of USUV and WNV are inhibited through a common set of IFN–induced genes (ISGs), with the notable exception of ISG20, which USUV is resistant to. Strikingly, USUV was the only virus among all the other tested mosquito-borne flaviviruses that demonstrated resistance to the 3′–5′ exonuclease activity of ISG20. Our findings highlight that the intrinsic resistance of the USUV genome, irrespective of the presence of cellular or viral proteins or protective post-transcriptional modifications, relies on a unique sequence present in its 3′ untranslated region. Importantly, this genomic region alone can confer ISG20 resistance to a susceptible flavivirus, without compromising its infectivity, suggesting that it could be acquired by other flaviviruses. This study provides new insights into the strategy employed by emerging flaviviruses to overcome host defense mechanisms.

Flaviviruses comprise a large number of arthropod-borne viruses, some of which are associated with life-threatening diseases. Flavivirus infections are rising worldwide, mainly due to the proliferation and geographical expansion of their vectors. The main human pathogens are mosquito-borne flaviviruses, including dengue virus, Zika virus, and West Nile virus, but tick-borne flaviviruses are also emerging. As with any viral infection, the body’s first line of defense against flavivirus infections is the innate immune defense, of which type I interferon is the armed wing. This cytokine exerts its antiviral activity by triggering the synthesis of hundreds of interferon-induced genes (ISGs), whose products can prevent infection. Among the ISGs that inhibit flavivirus replication, certain tripartite motif (TRIM) proteins have been identified. Although involved in other biological processes, TRIMs constitute a large family of antiviral proteins active on a wide range of viruses. Furthermore, whereas some TRIM proteins directly block viral replication, others are positive regulators of the IFN response. Therefore, viruses have developed strategies to evade or counteract TRIM proteins, and some even hijack certain TRIM proteins to their advantage. In this review, we summarize the current state of knowledge on the interactions between flaviviruses and TRIM proteins, covering both direct and indirect antiviral mechanisms.

Anticancer immunotherapies are therapeutics aimed at eliciting immune responses against tumor cells. Immunotherapies based on adoptive transfer of engineered immune cells have raised great hopes of cures because of the success of chimeric antigen receptor T-cell therapy in treating some hematologic malignancies. In parallel, advances in detailed analyses of the microenvironment of many solid tumors using high-dimensional approaches have established the origins and abundant presence of tumor-associated macrophages. These macrophages have an anti-inflammatory phenotype and promote tumor growth through a variety of mechanisms. Attempts have been made to engineer macrophages with chimeric receptors or transgenes to counteract their protumor activities and promote their antitumor functions such as phagocytosis of cancer cells, presentation of tumor antigens, and production of inflammatory cytokines. In this review, we cover current breakthroughs in engineering myeloid cells to combat cancer as well as potential prospects for myeloid-cell treatments.