Zika virus (ZIKV) infection is associated with severe neurological complications such as congenital microcephaly, yet no safe and effective vaccine is currently available. A critical challenge in ZIKV vaccine development arises from cross-reactive, non- or sub-neutralizing antibodies, which may enhance dengue virus (DENV) infection through antibody-dependent enhancement (ADE). Herein, we report a vaccine strategy utilizing Mi3 nanoparticles to display the Envelope (E) protein domain III (EDIII) of ZIKV, which induces protective immunity against ZIKV infection in murine models. Compared to an EDIII subunit vaccine, the Mi3-EDIII nanoparticle vaccine elicited significantly higher antibody responses and stronger cell-mediated immune responses. In C57BL/6 mice, maternal immunization with Mi3-EDIII protected the neonates against ZIKV-caused symptoms, including body weight loss, neurological abnormalities, retardation of brain development, and mortality. In interferon-α/β receptor knockout (Ifnar1-/-) C57BL/6 mice, Mi3-EDIII immunization conferred effective protection against lethal ZIKV challenge. Notably, unlike ZIKV convalescent sera, Mi3-EDIII immune sera did not enhance DENV infection in human chronic myelogenous leukemia K562 cells, suggesting the absence of ADE-prone antibody induction. Our results demonstrate that Mi3-EDIII is a promising vaccine candidate against ZIKV infection and warrants further development.

Viral hemorrhagic septicemia virus (VHSV) is a major pathogen affecting freshwater and marine fish species, posing a significant threat to global aquaculture. Reverse genetics systems are essential for studying viral replication, and host interactions, as well as developing vaccines and therapeutics. In this study, we developed a reverse genetics platform for VHSVLB2018 strain, a genetically distinct VHSV genotype IVa strain which exhibits low genomic identity with other Asian isolates, using a dual RNA polymerase I/II transcription vector. We successfully rescued recombinant VHSV in mammalian (B7GG) and fish (FHM and EPC) cell lines, and engineered recombinant VHSV strains expressing EGFP (rVHSV-EGFP) and cherry (rVHSV-Cherry) fluorescent proteins. Phenotypic analysis revealed that unmodified recombinant VHSV (rVHSV) exhibited growth kinetics and virulence similar to the wild-type VHSV, while fluorescent protein-expressing variants showed attenuated replication and virulence, with the rVHSV-EGFP strain displaying the greatest attenuation. Utilizing the rVHSV-EGFP strain, we conducted antiviral compound screening and identified three promising inhibitors-xanthohumol, octyl gallate, and rottlerin that effectively inhibit VHSV replication. Time-of-addition assays further revealed that xanthohumol and rottlerin targeted the viral replication stage, while octyl gallate interfered with viral internalization. This reverse genetics system provides a versatile platform for studying VHSV pathogenesis, developing live-attenuated vaccines, and screening antiviral compounds, enhancing our understanding of this pathogen and offering new tools for aquaculture disease management.

Emerging tick-borne viruses are posing an increasing health concern. However, there is limited knowledge about the distribution characteristics of tick virome in Yunnan Province, southwestern China, where it is distinguished by its diverse eco-climatic zones and rich biodiversity, making it a hotspot for studying tick-borne pathogens. The present study aimed to explore the diversity and ecological characteristics of tick virome in Yunnan Province, especially to identify novel potentially pathogenic viruses threatening human and vertebrate animals, and to investigate host-specific viral tropisms and their transmission characteristics. Using a meta-transcriptomic approach, the study analyzed the viromes of 448 individual ticks and approximately 10,000 eggs collected from nine counties with different hosts, altitudes and landscapes. The ticks encompassed eight species across four genera. The study focused on delineating virome diversity profiles, evaluating host-specific viral tropisms, and investigating potential transovarial transmission through viral contigs identification and Sanger sequencing. The study identified 53 viral families, revealing significant virome diversity and geographic and environmental specificity. Haemaphysalis and Ixodes ticks exhibited greater viral richness and abundance, with host taxonomy being a primary influencing factor. We determined 102 viral genomes encompassing 35 species, comprising 15 novel viruses identified when their RNA-dependent RNA polymerase/DNA polymerase sequences exhibited <90% amino acid identity to known viruses. The novel vectors for vertebrate-related or potentially pathogenic viruses were also detected, thus providing new insights into transmission cycles. The evidence for transovarial transmission was reinforced by the absence of significant differences in Chuviridae and Nairoviridae families between female ticks and their eggs. These findings underscore the necessity of continuous surveillance to avert the spillover of emerging pathogens.