Intrinsic features of Zika Virus non-structural proteins NS2A and NS4A in the regulation of viral replication

Robust antiviral innate immune response and miRNA regulatory network were identified in ZIKV-infected cells: implications in the pathogenesis of ZIKV infection

Zika virus (ZIKV) infection has emerged as a significant public health concern due to its association with fetal microcephaly and Guillain-Barre syndrome (GBS). Unfortunately, its detailed pathogenesis remains unclear. To better understand how ZIKV evades host antiviral immunity, we analyzed the microarray dataset (GSE98889) of ZIKV-infected primary human brain microvascular endothelial cells (hBMECs) retrieved from the gene expression omnibus (GEO). 160, 1423, 969, 829, and 600 differentially expressed genes (DEGs) were identified at 12, 24, 48, 72, and 216 hours post-ZIKV infection in hBMECs, respectively. Subsequently, 31 common DEGs across all time-points were selected for further analysis. Gene ontology (GO) functional analysis showed these 31 DEGs were mainly involved in the host antiviral innate immune responses. Protein-protein interaction (PPI) network analysis identified 10 hub genes (MX1, OAS1, OAS2, IFI44, IFI44L, IFIT1, IFIT2, IFIT3, IFIH1, and XAF1), which were all interferon-stimulated genes (ISGs) and upregulated. qRT-PCR was used to validate the expression patterns of these 10 hub genes in different ZIKV-infected cell lines. Finally, miRNA-mRNA regulatory network analysis revealed that hsa-miR-129-2-3p, hsa-miR-138-5p, hsa-miR-21-3p, hsa-miR-27a-5p, hsa-miR-449a, and hsa-miR449b-5p were key miRNAs regulating these hub genes. Our study showed that ZIKV infection activated the host innate immune response to restrict ZIKV infection. The common pathways, hub genes, and their regulatory miRNA network offer new insights into virus-host interactions, enhancing our understanding of ZIKV pathogenesis.

Diversities of African swine fever virus host-virus dynamics revealed by single-cell profiling

African swine fever virus (ASFV) causes epidemics with high mortality; however, effective vaccines and therapies remain missing. Here, we depict a temporal single-cell landscape of primary porcine alveolar macrophages (PAMs) exposed to three different virulent ASFV strains in vitro. We found that attenuated and low-virulence ASFV strains tend to exhibit higher viral loads than highly virulent strain, which may result from upregulated RNA polymerase subunit genes expression. On the host side, our study highlights the IRF7-mediated positive feedback loop to the activation of the interferon signaling pathway in cells exposed to attenuated and low virulent ASFV strains. Moreover, we unraveled the PAMs populations marked by expressions of the IFI16 and CD163, respectively, which produce high levels of interferon-stimulated genes (ISGs) and IL18 to regulate the host response to different virulent ASFV strains. Collectively, our data provide insights into the complex host-virus interactions with various ASFV strain infections, which may shed light on the development of effective antiviral strategies.IMPORTANCEThere is still no available research on the temporal transcriptional profile of host cells exposed to different virulent ASFV strains at the single-cell level. Here, we first profiled the temporal viral and host transcriptomes in PAMs exposed to high virulent, attenuated virulent, and low virulent ASFV strains. Our analysis revealed that attenuated and low-virulence ASFV strains tend to exhibit higher viral loads than highly virulent strains, which may result from upregulated RNA polymerase subunit genes expression. We also found a positive feedback loop of the interferon signaling pathway mediated through IRF7 and identified the populations of PAMs marked by IFI6 and CD163, respectively, which produce high levels of ISGs and IL18 to regulate host response to different virulent ASFV strains. Our study delineated a comprehensive single-cell landscape of host-virus dynamics across ASFV strains with different virulences and would provide an important resource for future research.

Functional Roles and Host Interactions of Orthoflavivirus Non-Structural Proteins During Replication

Orthoflavivirus, a genus encompassing arthropod-borne, positive-sense, single-stranded RNA viruses in the Flaviviridae family, represents clinically relevant viruses that pose significant threats to human and animal health worldwide. With warming climates and persistent urbanization, arthropod vectors and the viruses they transmit continue to widen their geographic distribution, expanding endemic zones. Flaviviruses such as dengue virus, Zika virus, West Nile virus, and tick-borne encephalitis virus cause debilitating and fatal infections globally. In 2024, the World Health Organization and the Pan American Health Organization declared the current dengue situation a Multi-Country Grade 3 Outbreak, the highest level. FDA-approved treatment options for diseases caused by flaviviruses are limited or non-existent, and vaccines are suboptimal for many flaviviruses. Understanding the molecular characteristics of the flavivirus life cycle, virus-host interactions, and resulting pathogenesis in various cells and model systems is critical for developing effective therapeutic intervention strategies. This review will focus on the virus-host interactions of mosquito- and tick-borne flaviviruses from the virus replication and assembly perspective, emphasizing the interplay between viral non-structural proteins and host pathways that are hijacked for their advantage. Highlighting interaction pathways, including innate immunity, intracellular movement, and membrane modification, emphasizes the need for rigorous and targeted antiviral research and development against these re-emerging viruses.

Distinct Replication Kinetics, Cytopathogenicity, and Immune Gene Regulation in Human Microglia Cells Infected with Asian and African Lineages of Zika Virus

Zika virus (ZIKV), a mosquito-borne flavivirus, is a significant global health concern due to its association with neurodevelopmental disorders such as congenital Zika syndrome (CZS). This study aimed to compare the replication kinetics, viral persistence, cytopathogenic effects, and immune gene expression in human microglia cells (CHME-3) infected with an Asian lineage ZIKV (PRVABC59, referred to as ZIKV-PRV) and an African lineage ZIKV (IBH30656, referred to as ZIKV-IBH). We found that ZIKV-PRV replicated more efficiently and persisted longer while inducing lower levels of cell death and inflammatory gene activation compared with ZIKV-IBH. These findings suggest that the enhanced replication and persistence of ZIKV-PRV, along with its ability to evade innate immune responses, may underlie its increased neuropathogenic potential, especially in the context of CZS. In contrast, ZIKV-IBH, with its stronger immune gene activation and higher cytopathogenicity, may lead to more acute infections with faster viral clearance, thereby reducing the likelihood of chronic central nervous system (CNS) infection. This study provides crucial insights into the molecular and cellular mechanisms driving the differential pathogenicity of ZIKV lineages and highlights the need for further research to pinpoint the viral factors responsible for these distinct clinical outcomes.

An evolutionarily conserved ubiquitin ligase drives infection and transmission of flaviviruses

Mosquito-borne flaviviruses such as dengue (DENV) and Zika (ZIKV) cause hundreds of millions of infections annually. The single-stranded RNA genome of flaviviruses is translated into a polyprotein, which is cleaved equally into individual functional proteins. While structural proteins are packaged into progeny virions and released, most of the nonstructural proteins remain intracellular and could become cytotoxic if accumulated over time. However, the mechanism by which nonstructural proteins are maintained at the levels optimal for cellular fitness and viral replication remains unknown. Here, we identified that the ubiquitin E3 ligase HRD1 is essential for flaviviruses infections in both mammalian hosts and mosquitoes. HRD1 directly interacts with flavivirus NS4A and ubiquitylates a conserved lysine residue for ER-associated degradation. This mechanism avoids excessive accumulation of NS4A, which otherwise interrupts the expression of processed flavivirus proteins in the ER. Furthermore, a small-molecule inhibitor of HRD1 named LS-102 effectively interrupts DENV2 infection in both mice and Aedes aegypti mosquitoes, and significantly disturbs DENV transmission from the infected hosts to mosquitoes owing to reduced viremia. Taken together, this study demonstrates that flaviviruses have evolved a sophisticated mechanism to exploit the ubiquitination system to balance the homeostasis of viral proteins for their own advantage and provides a potential therapeutic target to interrupt flavivirus infection and transmission.

Immune Recognition versus Immune Evasion Systems in Zika Virus Infection

The reemergence of the Zika virus (ZIKV) infection in recent years has posed a serious threat to global health. Despite being asymptomatic or mildly symptomatic in a majority of infected individuals, ZIKV infection can result in severe manifestations including neurological complications in adults and congenital abnormalities in newborns. In a human host, ZIKV is primarily recognized by RIG-like receptors and Toll-like receptors that elicit anti-viral immunity through the secretion of type I interferon (IFN) to limit viral survival, replication, and pathogenesis. Intriguingly, ZIKV evades its host immune system through various immune evasion strategies, including suppressing the innate immune receptors and signaling pathways, mutation of viral structural and non-structural proteins, RNA modulation, or alteration of cellular pathways. Here, we present an overview of ZIKV recognition by the host immune system and the evasion strategies employed by ZIKV. Characterization of the host-viral interaction and viral disease mechanism provide a platform for the rational design of novel prophylactic and therapeutic strategies against ZIKV infection.

A peptide derived from the N-terminal of NS2A for the preparation of ZIKV NS2A recognition polyclonal antibody

Zika virus non-structural protein NS2A participates in viral replication, organization, and budding, as well as escaping host immunity. NS2A also involved in the induction of microcephaly by ZIKV. However, the above studies were mainly performed through NS2A with a tag due to the lack of available antibodies against NS2A. ZIKV NS2A is a multiplex transmembrane protein, which leads to difficulties in the preparation of its recognition antibodies, thus seriously affecting the study of ZIKV NS2A. In this study, we found that a peptide (GSTDHMDHFSLGVLC) derived from the N-terminal of ZIKV NS2A coupled to KLH induced antibodies recognizing ZIKV NS2A in rabbits. The purified polyclonal antibody recognized ZIKV NS2A in ZIKV-infected cells with high efficiency and specificity, as detected by western blot and immunofluorescence assay. Our study has important implications for the preparation of ZIKV NS2A antibodies and the in-depth study of ZIKV NS2A.

Recent two-year advances in anti-dengue small-molecule inhibitors

Dengue is an acute tropical infectious disease transmitted by mosquitoes, which has posed a major challenge to global public health. Unfortunately, there is a lack of clinically proven dengue-specific drugs for its prevention and treatment. As the pathogenesis of dengue has not been fully elucidated, the development of specific drugs is seriously hindered. This article briefly describes the pathogenesis of dengue fever, the molecular characteristics, and epidemiology of dengue virus, and focuses on the potential small-molecule inhibitors of dengue virus, including on-target and multi-targeted inhibitors, which have been reported in the past two years.