Expressing the Pro-Apoptotic Reaper Protein via Insertion into the Structural Open Reading Frame of Sindbis Virus Reduces the Ability to Infect Aedes aegypti Mosquitoes

Arboviruses continue to threaten a significant portion of the human population, and a better understanding is needed of the determinants of successful arbovirus infection of arthropod vectors. Avoiding apoptosis has been shown to be one such determinant. Previous work showed that a Sindbis virus (SINV) construct called MRE/rpr that expresses the Drosophila pro-apoptotic protein Reaper via a duplicated subgenomic promoter had a reduced ability to orally infect Aedes aegypti mosquitoes at 3 days post-blood meal (PBM), but this difference diminished over time as virus variants containing deletions in the inserted reaper gene rapidly predominated. In order to further clarify the effect of midgut apoptosis on disseminated infection in Ae. aegypti, we constructed MRE/rprORF, a version of SINV containing reaper inserted into the structural open reading frame (ORF) as an in-frame fusion. MRE/rprORF successfully expressed Reaper, replicated similarly to MRE/rpr in cell lines, induced apoptosis in cultured cells, and caused increased effector caspase activity in mosquito midgut tissue. Mosquitoes that fed on blood containing MRE/rprORF developed significantly less midgut and disseminated infection when compared to MRE/rpr or a control virus up to at least 7 days PBM, when less than 50% of mosquitoes that ingested MRE/rprORF had detectable disseminated infection, compared with around 80% or more of mosquitoes fed with MRE/rpr or control virus. However, virus titer in the minority of mosquitoes that became infected with MRE/rprORF was not significantly different from control virus. Deep sequencing of virus populations from ten mosquitoes infected with MRE/rprORF indicated that the reaper insert was stable, with only a small number of point mutations and no deletions being observed at frequencies greater than 1%. Our results indicate that expression of Reaper by this method significantly reduces infection prevalence, but if infection is established then Reaper expression has limited ability to continue to suppress replication.     

First Report of the Detection of DENV1 in Human Blood Plasma with Near-Infrared Spectroscopy

Dengue virus (DENV) is the world’s most common arboviral infection, with an estimated 3.9 million people at risk of the infection, 100 million symptomatic cases and 10,000 deaths per year. Current diagnosis for DENV includes the use of molecular methods, such as polymerase chain reaction, which can be costly for routine use. The near-infrared spectroscopy (NIR) technique is a high throughput technique that involves shining a beam of infrared light on a biological sample, collecting a reflectance spectrum, and using machine learning algorithms to develop predictive algorithms. Here, we used NIR to detect DENV1 artificially introduced into whole blood, plasma, and serum collected from human donors. Machine learning algorithms were developed using artificial neural networks (ANN) and the resultant models were used to predict independent samples. DENV in plasma samples was detected with an overall accuracy, sensitivity, and specificity of 90% (N = 56), 88.5% (N = 28) and 92.3% (N = 28), respectively. However, a predictive sensitivity of 33.3% (N = 16) and 80% (N = 10) and specificity of 46.7% (N = 16) and 32% (N = 10) was achieved for detecting DENV1 in whole blood and serum samples, respectively. DENV1 peaks observed at 812 nm and 819 nm represent C-H stretch, peaks at 1130–1142 nm are related to methyl group and peaks at 2127 nm are related to saturated fatty groups. Our findings indicate the potential of NIR as a diagnostic tool for DENV, however, further work is recommended to assess its sensitivity for detecting DENV in people naturally infected with the virus and to determine its capacity to differentiate DENV serotypes and other arboviruses.     

5种虫媒病毒悬浮芯片检测方法的建立

目的建立同时检测1~4型登革病毒、乙型脑炎病毒、西尼罗病毒、森林脑炎病毒和黄热病病毒等5种虫媒病毒的悬浮芯片检测方法。方法根据GenBank发表的上述病毒的序列,通过生物信息学分析和参考相关文献,在黄病毒属高度保守的NS5区设计属通用引物和种特异检测探针。将探针共价交联到不同的Luminex色标微球上,利用属通用引物进行RT-PCR扩增,与混合微球杂交,最后利用Luminex200仪器分析荧光强度值。结果将平均荧光强度的判定阈值定为背景对照的两倍可以对这5种共8型病毒进行有效鉴定。通过多批次的实验,均能准确鉴定出上述5种病毒,没有出现交叉反应,且批次间的平均荧光值偏离不大,变异系数(CV)均小于8%,表明本方法的特异性和稳定性均较好。在空斑滴定病毒的基础上,对本方法的检测敏感性进行了验证,结果表明对乙脑和黄热病病毒的检测敏感性可达到1.4个PFU,对西尼罗病毒可达14个PFU。进而将本方法用于检测55份临床标本和传代标本,其检测结果和种特异RT-PCR方法相比,具有很高的一致性,而且其在混合样本的快速检测中具有显著的优势。结论通过设计合适的引物和探针,成功建立了可同时检测和分型5种虫媒病毒的悬浮芯片方法,为疾病的诊断和预防以及流行病学调查提供了新的手段。     

Use of Insecticide-Treated House Screens to Reduce Infestations of Dengue Virus Vectors,Mexico

Dengue prevention efforts rely on control of virus vectors. We investigated use of insecticide-treated screens permanently affixed to windows and doors in Mexico and found that the screens significantly reduced infestations of Aedes aegypti mosquitoes in treated houses. Our findings demonstrate the value of this method for dengue virus vector control.     

Patents related to dengue virus infection

This review discusses patents relevant to dengue virus infection. Dengue virus is a mosquito-transmitted flavivirus that usually causes an acute self-limited febrile illness, but may result in more severe life threatening disease. The lack of animal models that replicate features of the human disease has inhibited developing an understanding of the pathophysiology of dengue virus infection and consequently, limited investigation into potential therapeutics. However, there has been considerable progress in vaccine development and recent insights into the identity of the cells infected during the course of dengue virus infection and characterisation of cell-surface receptors used to mediate infectivity, have provided important information with therapeutic implications. There is no treatment for dengue virus infection and no vaccine is yet available, new approaches are urgently needed.     

Evaluation of Antiviral Activity of Cyclic Ketones against Mayaro Virus

Mayaro virus (MAYV) is a neglected arthropod-borne virus found in the Americas. MAYV infection results in Mayaro fever, a non-lethal debilitating disease characterized by a strong inflammatory response affecting the joints and muscles. MAYV was once considered endemic to forested areas in Brazil but has managed to adapt and spread to urban regions using new vectors, such as Aedes aegypti, and has the potential to cause serious epidemics in the future. Currently, there are no vaccines or specific treatments against MAYV. In this study, the antiviral activity of a series of synthetic cyclic ketones were evaluated for the first time against MAYV. Twenty-four compounds were screened in a cell viability assay, and eight were selected for further evaluation. Effective concentration (EC₅₀) and selectivity index (SI) were calculated and compound 9-(5-(4-chlorophenyl]furan-2-yl)-3,6-dimethyl-3,4,5,6,7,9-hexahydro-1H-xanthene-1,8(2))-dione (9) (EC₅₀ = 21.5 µmol·L⁻¹, SI = 15.8) was selected for mechanism of action assays. The substance was able to reduce viral activity by approximately 70% in both pre-treatment and post-treatment assays.     

RNAi-mediated immunity provides strong protection against the negative-strand RNA vesicular stomatitis virus in Drosophila

Activation of innate antiviral responses in multicellular organisms relies on the recognition of structural differences between viral and cellular RNAs. Double-stranded (ds)RNA, produced during viral replication, is a well-known activator of antiviral defenses and triggers interferon production in vertebrates and RNAi in invertebrates and plants. Previous work in mammalian cells indicates that negative-strand RNA viruses do not appear to generate dsRNA, and that activation of innate immunity is triggered by the recognition of the uncapped 5' ends of viral RNA. This finding raises the question whether antiviral RNAi, which is triggered by the presence of dsRNA in insects, represents an effective host-defense mechanism against negative-strand RNA viruses. Here, we show that the negative-strand RNA virus vesicular stomatitis virus (VSV) does not produce easily detectable amounts of dsRNA in Drosophila cells. Nevertheless, RNAi represents a potent response to VSV infection, as illustrated by the high susceptibility of RNAi-defective mutant flies to this virus. VSV-derived small RNAs produced in infected cells or flies uniformly cover the viral genome, and equally map the genome and antigenome RNAs, indicating that they derive from dsRNA. Our findings reveal that RNAi is not restricted to the defense against positive-strand or dsRNA viruses but can also be highly efficient against a negative-strand RNA virus. This result is of particular interest in view of the frequent transmission of medically relevant negative-strand RNA viruses to humans by insect vectors.