Search Results (72)

Assessing mosquito vector competence for emerging arboviruses, including the underlying determinants of infection, is a foundational line of investigation towards understanding arbovirus transmission dynamics and vector–virus interactions. We developed a novel quantitative immune gene array that measures the relative expression of 22 immune genes with functional representation across five major immune pathways using quantitative reverse-transcriptase polymerase chain reaction. Homologous primers were developed for Culex tarsalis, Cx. quinquefasciatus, and Ae. aegypti mosquitoes. As an initial pilot test for this array, Cx. tarsalis and Ae. aegypti mosquitoes were orally challenged with Rift Valley fever virus (RVFV) MP12 strain. Midguts, legs/wings, and salivary glands were harvested at 3 and 7 days post-challenge. Differential gene expression was measured against Rpl32 as a housekeeping gene. This assay was sensitive enough to generate results for single mosquito midgut and salivary gland tissues, providing an initial snapshot of the types of gene expression patterns that can be observed for two mosquito species infected with MP12. This new tool will be broadly applicable for assessing mosquito immune profiles for arbovirus infection across major immune genes in five key pathways, as well as generating comparable results across mosquito and arbovirus systems. Full article

Rift Valley fever virus (RVFV) is a re-emerging, vector-borne pathogen endemic to Africa and the Arabian Peninsula, posing an increasing threat to human and animal health. Outbreaks have severe economic and social impacts on farmers, communities, and governments. Current diagnostic methods rely on PCR and ELISA; however, rapid pen-side tests would enable faster, cost-effective monitoring and outbreak control. Here, a species- and immunoglobulin class-independent capillary flow immunodiagnostic assay (lateral flow test; LFT) for detecting RVFV-specific antibodies is described. The assay uses a double-antigen approach, coupling the RVFV nucleocapsid protein, a major viral antigen, both to carbon nanoparticles and to a nitrocellulose membrane. The method was qualified with immune sera from sheep, calves, goats, and humans and benchmarked against a newly developed double-antigen ELISA and a commercial competition ELISA. Both the LFT and double-antigen ELISA demonstrated high specificity and sensitivity. This advancement brings RVFV-specific pen-side testing significantly closer to practical implementation. Full article

Severe fever with thrombocytopenia syndrome virus (SFTSV) is an emerging tick-borne bunyavirus that causes a severe viral hemorrhagic fever (SFTS), with a very high case mortality rate, expanding epidemic areas, and increasing incidence. Due to the lack of an effective drug or vaccine for SFTS, reducing the incidence and mortality of SFTS primarily relies on decreasing the density of ticks and the number of their host animals. However, which tick species and vertebrate animal serve as the major reservoir and animal host of SFTSV are not clearly understood. In May of 2023 and June of 2024, we collected 2437 ticks from domesticated animals and grassland in Suizhou City, a prefecture of Hubei Province in central China. A total of 195 domesticated animal blood samples were collected, including 152 goats, 26 cattle, and 17 dogs. Ticks were grouped for RNA extraction according to their life stages and feeding status. RNA from each animal’s blood and each group of ticks was extracted with an RNA extraction kit and tested for SFTSV with RT-PCR. Ticks were classified according to morphology, and representative ticks of each stage were confirmed with PCR amplification and DNA sequencing of the mitochondrial 16S RNA gene. Among the collected ticks, the majority were from goats (72.7%, 1772/2437), and Haemaphysalis longicornis was predominant, accounting for 99.47% (2425/2437), and other tick species were very rare, with 0.45% (11/2437) Rhipicephalus microplus, and 0.04% (1/2437) H. flava and Ixodes sinensis, respectively. We found SFTSV RNA in H. longicornis ticks with a minimum infection rate of 0.17% (4/2424) and in one goat (0.66%,1/152). In summary, we demonstrated that the H. longicornis tick is positive for SFTSV and that the goat is the major host of Haemaphysalis longicornis in Suizhou, central China. Our study suggests that controlling ticks on goats may play an important role in preventing SFTSV infection in China. Full article

Chalcones are flavonoid compounds containing an α,β-unsaturated ketone core that are often found in plants and have diverse biological activities including antiviral activity. For example, chalcone 8o was previously shown to have antiviral activity against human cytomegalovirus (HCMV) and human immunodeficiency virus (HIV); two viruses that use a nuclear phase to complete their growth cycle. Here, we synthesized ten new derivatives of 8o and tested them for antiviral activity against four RNA viruses that replicate exclusively in the cytoplasm, including prototype members of the paramyxovirus, flavivirus, bunyavirus, and coronavirus families. For example, chalcones 8o and 8p showed potent inhibition of PIV5 replication with minimal cytotoxicity in human fibroblast cultures. Time-of-addition studies showed that these chalcones inhibit an early stage of viral replication and prevent viral spread through cell cultures. Most importantly, our top performing chalcones showed potent in vitro antiviral activity against Zika virus, La Crosse Virus, and the coronavirus OC43. These studies offer mechanistic insight into chalcone-mediated inhibition of viral replication, demonstrate the influence of functional group changes of chalcone scaffolds on their efficacy as antivirals, and support the development of chalcones as broad-spectrum antiviral compounds. Full article

Severe fever with thrombocytopenia syndrome virus (SFTSV) is a tick-borne bunyavirus with a mortality rate of up to 30%. There is no specific treatment for SFTSV. This article systematically reviews the progress of major anti-SFTSV drugs. The nucleotide analogues (favipiravir, 4′-fluorouridine diphosphate prodrug VV261) have shown clinical potential. Calcium channel blockers (nifedipine, etc.) block virus invasion by inhibiting calcium influx. Monoclonal antibody (S2A5/SNB02) has achieved targeted therapy, and SNB02 nanoantibody has entered clinical trials. However, many candidate agents predominantly focus on a single target, such as viral RdRp or host calcium channels, which makes it difficult to block the entire viral replication cycle and may accelerate the accumulation of resistant mutations. In addition, the low bioavailability of small-molecule drugs, the obstacles to industrial-scale production of antibody-based therapies, and the lack of Phase III clinical evidence severely restrict their clinical translation. Future research should focus on exploring viral replication mechanisms, developing drugs against key viral proteins, and designing multi-target combination therapies and novel drug delivery systems. Full article

Background: Severe fever with thrombocytopenia syndrome virus (SFTSV) is a highly pathogenic bunyavirus with a high case-fatality ratio for which there is no approved vaccine. Studies have assessed different vaccine technologies. However, few studies have yet assessed the immunogenicity of heterologous prime-boost regimens. Methods: Here, we compare a lipid nanoparticle (LNP)-encapsulated nucleoside-modified mRNA-based vaccine encoding the SFTSV glycoproteins, Gn and Gc, to our recently described recombinant VSV SFTSV (rVSV-SFTSV) vaccine in single dose, homologous, and heterologous prime-boost regimens in mice. Results: We show that all regimens protect from pathogenic SFTSV challenge and elicit strong long-lasting antibody responses. Furthermore, strong cellular immunity is elicited by mRNA-LNP immunizations and by heterologous immunization with an rVSV-SFTSV prime and mRNA-LNP boost. Cellular responses robustly polarized towards a type 1 response, characterized by high levels of IFNγ, TNFα, and IL-2. Immunization with mRNA led to a mixed type 1/type 2 immune response, as determined by antibody isotypes IgG1 and IgG2c. We found that homologous immunization leads to stronger antibody responses while heterologous immunization drives a slightly stronger cellular response. Conclusions: Taken together, the vaccine platforms described here represent strong vaccine candidates for further development. Full article

Crimean–Congo hemorrhagic fever virus (CCHFV) causes severe or fatal infections in humans and is geographically widespread. The virus has coevolved with its tick vectors, establishing persistent infections critical to its transmission. This study explored the mechanisms underpinning these persistent infections, using tick cell lines and the Hazara virus (HAZV) as a biosafety level 2 (BSL-2) model for CCHFV. Initially, an RT-qPCR protocol was developed to detect HAZV in tick cells. The study then focused on the production of virus-derived DNA (vDNAs) by tick cells as a defensive response to infection. These vDNAs regulate viral particle production, enabling tick cells to maintain viability and establish persistent infections. The experiments characterized vDNAs production, viral titers, and subcellular localization, and they examined the effect of the reverse transcriptase inhibitor azidothymidine triphosphate (AZT). The results showed that all tested tick cell lines supported HAZV replication, achieving persistent infections without cytopathic effects. vDNAs was detected in both the cytoplasm and nucleus, and its formation was dependent on HAZV infection. Importantly, vDNAs presence was linked to infection persistence; cells treated with AZT exhibited a marked reduction in vDNAs production and an associated increase in viral particle production, which correlated with higher cell death. These findings underscore the critical role of vDNAs in balancing viral replication and promoting long-term cell survival in tick cells, highlighting their importance in the coevolution of tick-borne viruses and their vectors. Full article

Rift Valley fever virus (RVFV) is a mosquito-transmitted bunyavirus that can cause substantial morbidity and mortality in livestock and humans, for which there are no currently available licensed human therapeutics or vaccines. Therefore, the development of safe and effective antivirals is both necessary and urgent. The Gc protein is the primary target of the neutralizing antibody response related to Rift Valley fever virus. Here, we report one Gc-specific neutralizing antibody (NA137) isolated from an alpaca and one bispecific antibody (E2-NA137), the protective efficacies of which we evaluated in A129 mice. In this prophylactic study, the survival rates of the NA137 and E2-NA137 groups were both 80%, and in the treatment study, the survival rates were 20% and 60%, respectively. Altogether, our results emphasize that NA137 and E2-NA137 provide a potential approach for treating RVFV either prophylactically or therapeutically. Full article

Background: Severe fever with thrombocytopenia syndrome virus (SFTSV) is a novel tick-borne bunyavirus, causing the hemorrhagic infectious disease of SFTS, with a case fatality rate up to 30% due to the absence of effective therapeutic interventions. Therefore, it is urgent to develop safe and effective therapeutic drugs to control this viral hemorrhagic fever. Methods: The activity of verteporfin (VP), screened from an FDA-approved drugs library, against SFTSV, was systematically evaluated in Huh7 cells in a wide range of concentrations. We performed time-of-addition experiments with VP, along with binding, endocytosis, and membrane fusion assays, to determine which part of the SFTSV life cycle VP has its effect on. The potential targets of VP were detected by a drug affinity responsive target stability (DARTS) assay. Results: VP exhibited a potent anti-SFTSV activity by blocking the initial viral binding to the target cells during viral entry via significantly inducing the degradation of the viral Gn protein. Conclusions: The VP-induced inhibition of SFTSV binding, the first step of viral invasion, suggested that VP might be an ideal and potent anti-SFTSV agent due to its prophylaxis and therapeutic effects on viral infection. Full article

Recent outbreaks of Oropouche virus (OROV) in Latin America demonstrate shifting epidemiological trends, with increasing clinical severity and geographic expansion driven by environmental and anthropogenic factors, many of which remain uncertain. Viral evolution with new reassortant strains, changes in vectors, environmental degradation, and human activities have been postulated as factors that have facilitated its spread into new areas beyond the Amazon Basin. Multiple reports starting in July 2024 of pregnant women with Oropouche fever developing vertical infections and adverse perinatal outcomes, including placental infection, stillbirth, and fetal infections with microcephaly and malformation syndromes, have reinforced the public health significance of this disease. Here, we describe the evidence surrounding this re-emerging epidemic threat, examine these changes, and propose specific strategies for enhanced surveillance and a public health response. Full article

The Rift Valley fever virus (RVFV) causes haemorrhagic fever, encephalitis, and permanent blindness and has been listed by the WHO as a priority pathogen. To study RVFV pathogenesis and identify small-molecule antivirals, we established a novel In Vivo model using zebrafish larvae. Pericardial injection of RVFV resulted in ~4 log₁₀ viral RNA copies/larva, which was inhibited by the antiviral 2′-fluoro-2′-deoxycytidine. The optical transparency of the larvae allowed detection of RVFV_eGFP in the liver and sensory nervous system, including the optic tectum and retina, but not the brain or spinal cord. Thus, RVFV-induced blindness likely occurs due to direct damage to the eye and peripheral neurons, rather than the brain. Treatment with the JAK-inhibitor ruxolitinib, as well as knockout of stat1a but not stat1b, enhanced RVFV replication to ~6 log₁₀ viral RNA copies/larva and ultra-bright livers, although without dissemination to sensory neurons or the eye, thereby confirming the critical role of stat1 in RVFV pathogenesis. Full article

Rift Valley fever phlebovirus (RVFV) is a zoonotic mosquito-borne pathogen endemic to sub-Saharan Africa and the Arabian Peninsula which causes Rift Valley fever in ruminant livestock and humans. Co-infection with divergent viral strains can produce reassortment among the L, S, and M segments of the RVFV genome. Reassortment events can produce novel genotypes with altered virulence, transmission dynamics, and/or mosquito host range. This can have severe implications in areas where RVFV is endemic and convolutes our ability to anticipate transmission and circulation in novel geographic regions. Previously, we evaluated the frequency of RVFV reassortment in a susceptible ruminant host and observed low rates of reassortment (0–1.7%). Here, we tested the hypothesis that reassortment occurs predominantly in the mosquito using a highly permissive vector, Culex tarsalis. Cells derived from Cx. tarsalis or adult mosquitoes were co-infected with either two virulent (Kenya-128B-15 and SA01-1322) or a virulent and attenuated (Kenya-128B-15 and MP-12) strain of RVFV. Our results showed approximately 2% of virus genotypes isolated from co-infected Cx. tarsalis-derived cells were reassortant. Co-infected mosquitoes infected via infectious bloodmeal resulted in a higher percentage of reassortant virus (2–60%) isolated from midgut and salivary tissues at 14 days post-infection. The percentage of reassortant genotypes isolated from the midguts of mosquitoes co-infected with Kenya-128B-15 and SA01-1322 was similar to that of mosquitoes co-infected with Kenya-128B-15 and MP-12- strains (60 vs. 47%). However, only 2% of virus isolated from the salivary glands of Kenya-128B-15 and SA01-1322 co-infected mosquitoes represented reassortant genotypes. This was contrasted by 54% reassortment in the salivary glands of mosquitoes co-infected with Kenya-128B-15 and MP-12 strains. Furthermore, we observed preferential inclusion of genomic segments from the three parental strains among the reassorted viruses. Replication curves of select reassorted genotypes were significantly higher in Vero cells but not in Culex—derived cells. These data imply that mosquitoes play a crucial role in the reassortment of RVFV and potentially contribute to driving evolution of the virus. Full article

On 27 May 2024, the Cuban Ministry of Health reported the first outbreak of Oropouche fever on the island. The etiologic agent, Oropouche virus (OROV), is a poorly understood arbovirus that has been known since the 1960s and represents a public health burden in Latin America. We report the whole-genome characterization of the first European OROV isolate from a returning traveler from Cuba with Oropouche fever-like symptoms. The isolate was obtained from the patient’s serum; whole-genome sequencing was performed by next-generation sequencing, followed by phylogenetic analysis and genetic variability studies. The analysis showed that the most closely related sequence was from the French Guiana 2020 outbreak. Interestingly, our isolate is a reassortant virus, included in a highly supported monophyletic clade containing recent OROV cases (Brazil 2015–Colombia 2021), separated from the other four previously known genotypes. More deeply, it was found to be included in a distinct branch containing the sequences of the Brazil 2022–2024 outbreak. The reassortment event involved the S and L segments, which have high similarity with sequences belonging to a new cluster (here defined as OROV_SCDC_2024), while the M segment shows high similarity with older sequences. These results likely describe the viral strain responsible for the current outbreak in Cuba, which may also reflect the ongoing outbreak in Latin America. Further studies are needed to understand how OROV evolves towards traits that facilitate its spread and adaptation outside its original basin, and to track its spread and evolution in the European continent. Full article

Oropouche virus (OROV) is an emerging arbovirus endemic in Latin America and the Caribbean that causes Oropouche fever, a febrile illness that clinically resembles some other arboviral infections. It is currently spreading through Brazil and surrounding countries, where, from 1 January to 1 August 2024, more than 8000 cases have been identified in Bolivia, Brazil, Columbia, and Peru and for the first time in Cuba. Travelers with Oropouche fever have been identified in the United States and Europe. A significant occurrence during this epidemic has been the report of pregnant women infected with OROV who have had miscarriages and stillborn fetuses with placental, umbilical blood and fetal somatic organ samples that were RT-PCR positive for OROV and negative for other arboviruses. In addition, there have been four cases of newborn infants having microcephaly, in which the cerebrospinal fluid tested positive for IgM antibodies to OROV and negative for other arboviruses. This communication examines the biology, epidemiology, and clinical features of OROV, summarizes the 2023–2024 Oropouche virus epidemic, and describes the reported cases of vertical transmission and congenital infection, fetal death, and microcephaly in pregnant women with Oropouche fever, addresses experimental animal infections and potential placental pathology findings of OROV, and reviews other bunyavirus agents that can cause vertical transmission. Recommendations are made for pregnant women travelling to the regions affected by the epidemic. Full article

The order Bunyavirales belongs to the class of Ellioviricetes and is classified into fourteen families. Some species of the order Bunyavirales pose potential threats to human health. The continuously increasing research reveals that various viruses within this order achieve immune evasion in the host through suppressing interferon (IFN) response. As the types and nodes of the interferon response pathway are continually updated or enriched, the IFN suppression mechanisms and target points of different virus species within this order are also constantly enriched and exhibit variations. For instance, Puumala virus (PUUV) and Tula virus (TULV) can inhibit IFN response through their functional NSs inhibiting downstream factor IRF3 activity. Nevertheless, the IFN suppression mechanisms of Dabie bandavirus (DBV) and Guertu virus (GTV) are mostly mediated by viral inclusion bodies (IBs) or filamentous structures (FSs). Currently, there are no effective drugs against several viruses belonging to this order that pose significant threats to society and human health. While the discovery, development, and application of antiviral drugs constitute a lengthy process, our focus on key targets in the IFN response suppression process of the virus leads to potential antiviral strategies, which provide references for both basic research and practical applications. Full article