Emergence of Zika Virus in Culex tritaeniorhynchus and Anopheles sinensis Mosquitoes in China

Zika virus(ZIKV) has been isolated from mosquitoes such as Aedes, Mansonia uniformis, and Culex perfuscus; However,the isolation of ZIKV from Anopheles sinensis and Culex tritaeniorhynchus has not yet been reported. In June and July2018, 22,985 mosquitoes and 57,500 midges were collected in Jiangxi Province in southeastern China. Among them, six strains of ZIKV were isolated from mosquitoes: four from An. sinensis and two from Cx. tritaeniorhynchus. Molecular genetic analysis showed that the ZIKV isolated from An. sinensis and Cx. tritaeniorhynchus belonged to genotype 2 in the Asian evolutionary branch of ZIKV. In addition, the ZIKV strains isolated from An. sinensis and Cx. tritaeniorhynchus had amino acid substitutions identical to ZIKV strains prevalent in South America since 2015. This study is the first to isolate ZIKV from mosquito specimens collected in the wild of Jiangxi Province, China; This is also the first time that ZIKV has been isolated from An. sinensis and Cx. tritaeniorhynchus. Given that An. sinensis and Cx. tritaeniorhynchus have a very wide geographical distribution in China and even in eastern and southern Asia, the isolation of several strains of ZIKV from these two mosquitoes poses new challenges for the prevention and control of ZIKV infection in the mainland of China and countries and regions with the same distribution of mosquitoes.     

Vector Competence of American Mosquitoes for Three Strains of Zika Virus

In 2015, Zika virus (ZIKV; Flaviviridae; Flavivirus) emerged in the Americas, causing millions of infections in dozens of countries. The rapid spread of the virus and the association with disease outcomes such as Guillain-Barré syndrome and microcephaly make understanding transmission dynamics essential. Currently, there are no reports of vector competence (VC) of American mosquitoes for ZIKV isolates from the Americas. Further, it is not clear whether ZIKV strains from other genetic lineages can be transmitted by American Aedes aegypti populations, and whether the scope of the current epidemic is in part facilitated by viral factors such as enhanced replicative fitness or increased vector competence. Therefore, we characterized replication of three ZIKV strains, one from each of the three phylogenetic clades in several cell lines and assessed their abilities to be transmitted by Ae. aegypti mosquitoes. Additionally, laboratory colonies of different Culex spp. were infected with an American outbreak strain of ZIKV to assess VC. Replication rates were variable and depended on virus strain, cell line and MOI. African strains used in this study outcompeted the American strain in vitro in both mammalian and mosquito cell culture. West and East African strains of ZIKV tested here were more efficiently transmitted by Ae. aegypti from Mexico than was the currently circulating American strain of the Asian lineage. Long-established laboratory colonies of Culex mosquitoes were not efficient ZIKV vectors. These data demonstrate the capacity for additional ZIKV strains to infect and replicate in American Aedes mosquitoes and suggest that neither enhanced virus replicative fitness nor virus adaptation to local vector mosquitoes seems likely to explain the extent and intensity of ZIKV transmission in the Americas.     

Zika Virus: New Clinical Syndromes and Its Emergence in the Western Hemisphere

Zika virus (ZIKV) had remained a relatively obscure flavivirus until a recent series of outbreaks accompanied by unexpectedly severe clinical complications brought this virus into the spotlight as causing an infection of global public health concern. In this review, we discuss the history and epidemiology of ZIKV infection, recent outbreaks in Oceania and the emergence of ZIKV in the Western Hemisphere, newly ascribed complications of ZIKV infection, including Guillain-Barré syndrome and microcephaly, potential interactions between ZIKV and dengue virus, and the prospects for the development of antiviral agents and vaccines.     

Molecular Evolution of Zika Virus during Its Emergence in the 20th Century

Zika virus (ZIKV) is a mosquito-borne flavivirus first isolated in Uganda in 1947. Although entomological and virologic surveillance have reported ZIKV enzootic activity in diverse countries of Africa and Asia, few human cases were reported until 2007, when a Zika fever epidemic took place in Micronesia. In the context of West Africa, the WHO Collaborating Centre for Arboviruses and Hemorrhagic Fever at Institut Pasteur of Dakar (http://www.pasteur.fr/recherche/banques/CRORA/) reports the periodic circulation of ZIKV since 1968. Despite several reports on ZIKV, the genetic relationships among viral strains from West Africa remain poorly understood. To evaluate the viral spread and its molecular epidemiology, we investigated 37 ZIKV isolates collected from 1968 to 2002 in six localities in Senegal and Côte d''Ivoire. In addition, we included strains from six other countries. Our results suggested that these two countries in West Africa experienced at least two independent introductions of ZIKV during the 20^th century, and that apparently these viral lineages were not restricted by mosquito vector species. Moreover, we present evidence that ZIKV has possibly undergone recombination in nature and that a loss of the N154 glycosylation site in the envelope protein was a possible adaptive response to the Aedes dalzieli vector.     

寨卡病毒非结构蛋白研究进展

自2015年巴西确诊首个寨卡病毒感染病例以来,该病毒在全球范围内迅速蔓延,引发了大规模疫情。寨卡病毒感染不仅会导致新生儿小头畸形,还会引起格林-巴利综合征,后者是一种严重的神经系统疾病,可以导致患者瘫痪乃至死亡。但是目前并没有特异性的疫苗或药物可以用于阻断寨卡病毒的感染。近几年来,寨卡病毒在复制传播过程中多个关键蛋白的结构逐步得到解析,在一定程度上为其致病机制的阐释提供了理论基础,并对特异性药物设计具有一定指导意义。主要对寨卡病毒多个非结构蛋白的三维空间结构研究进展及其抑制剂研发的主要方向进行了综述,以期为药物靶点的分析筛选及抗病毒药物的开发设计提供参考。     

Generation of A Stable GFP-reporter Zika Virus System for High-throughput Screening of Zika Virus Inhibitors

Zika virus(ZIKV) is associated with severe birth defects and Guillain-Barre′ syndrome and no approved vaccines or specific therapies to combat ZIKV infection are currently available. To accelerate anti-ZIKV therapeutics research, we developed a stable ZIKV GFP-reporter virus system with considerably improved GFP visibility and stability. In this system a BHK-21 cell line expressing DC-SIGNR was established to facilitate the proliferation of GFP-reporter ZIKV. Using this reporter virus system, we established a high-throughput screening assay and screened a selected plant-sourced compounds library for their ability to block ZIKV infection. More than 31 out of 974 tested compounds effectively decreased ZIKV reporter infection. Four selected compounds, homoharringtonine(HHT), bruceine D(BD), dihydroartemisinin(DHA) and digitonin(DGT), were further validated to inhibit wild-type ZIKV infection in cells of BHK-21 and human cell line A549.The FDA-approved chronic myeloid leukemia treatment drug HHT and BD were identified as broad-spectrum flavivirus inhibitors. DHA, another FDA-approved antimalarial drug effectively inhibited ZIKV infection in BHK-21 cells. HHT, BD and DHA inhibited ZIKV infection at a post-entry stage. Digitonin was found to have inhibitory activity in the early stage of viral infection. Our research provides an efficient high-throughput screening assay for ZIKV inhibitors. The active compounds identified in this study represent potential therapies for the treatment of ZIKV infection.     

Molecular Recognition Features in Zika Virus Proteome

Viruses have compact genomes that encode limited number of proteins in comparison to other biological entities. Interestingly, viral proteins have shown natural abundance of either completely disordered proteins that are recognized as intrinsically disorder proteins (IDPs) or partially disordered segments known as intrinsically disordered protein regions (IDPRs). IDPRs are involved in interactions with multiple binding partners to accomplish signaling, regulation, and control functions in cells. Tuning of IDPs and IDPRs are mediated through post-translational modification and alternative splicing. Often, the interactions of IDPRs with their binding protein partner(s) lead to transition from the state of disorder to ordered form. Such interaction-prone protein IDPRs are identified as molecular recognition features (MoRFs). Molecular recognition is an important initial step for the biomolecular interactions and their functional proceedings. Although previous studies have established occurrence of the IDPRs in Zika virus proteome, which provide the functional diversity and structural plasticity to viral proteins, the MoRF analysis has not been performed as of yet. Many computational methods have been developed for the identification of the MoRFs in protein sequences including ANCHOR, MoRFpred, DISOPRED3, and MoRFchibi_web server. In the current study, we have investigated the presence of MoRF regions in structural and non-structural proteins of Zika virus using an aforementioned set of computational techniques. Furthermore, we have experimentally validated the intrinsic disorderness of NS2B cofactor region of NS2B–NS3 protease. NS2B has one of the longest MoRF regions in Zika virus proteome. In future, this study may provide valuable information while investigating the virus host protein interaction networks.     

寨卡病毒,不仅仅是小头畸形

寨卡病毒(Zika virus,ZIKV)属于黄病毒科黄病毒属,由蚊虫叮咬传播。ZIKV发现于1947年。2007年以来,由于基因突变,ZIKV获得了更强的神经嗜性和在蚊虫体内播散的能力,因而在全球加快流行,并与成人吉兰-巴雷综合征和胎儿小头畸形的发生密切相关。最近的临床观察和动物研究进一步表明,ZIKV感染引起的临床症状复杂多样,所造成的疾病不仅仅是小头畸形,它还能够损伤雄性生殖系统,干扰下丘脑对神经内分泌系统的调节,引起多种激素分泌缺陷,导致生长发育迟缓和学习记忆能力损伤。因此,对于先天感染ZIKV的新生儿,不仅要在孕期监测小头畸形的发生,出生后也需进行长期的跟踪观察;对于出生后感染ZIKV的婴幼儿以及学龄前儿童,无论病情轻重,也需要进行随访,以明确ZIKV感染的远期影响。     

Vectors,Hosts, and Control Measures for Zika Virus in the Americas

We examine Zika virus (ZIKV) from an ecological perspective and with a focus on the Americas. We assess (1) the role of wildlife in ZIKV disease ecology, (2) how mosquito behavior and biology influence disease dynamics, and (3) how nontarget species and ecosystems may be impacted by vector control programs. Our review suggests that free-ranging, non-human primates may be involved in ZIKV transmission in the Old World; however, other wildlife species likely play a limited role in maintaining or transmitting ZIKV. In the Americas, a zoonotic cycle has not yet been definitively established. Understanding behaviors and habitat tolerances of Aedes aegypti and Aedes albopictus, two ZIKV competent vectors in the Americas, will allow more accurate modeling of disease spread and facilitate targeted and effective control efforts. Vector control efforts may have direct and indirect impacts to wildlife, particularly invertebrate feeding species; however, strategies could be implemented to limit detrimental ecological effects.     

Recent Advances in Animal Models of Zika Virus Infection

An infection by Zika virus(ZIKV), a mosquito-borne flavivirus, broke out in South American regions in 2015, and recently showed a tendency of spreading to North America and even worldwide. ZIKV was first detected in 1947 and only 14 human infection cases were reported until 2007. This virus was previously observed to cause only mild flu-like symptoms.However, recent ZIKV infections might be responsible for the increasing cases of neurological disorders such as GuillainBarre′ syndrome and congenital defects, including newborn microcephaly. Therefore, researchers have established several animal models to study ZIKV transmission and pathogenesis, and test therapeutic candidates. This review mainly summarizes the reported animal models of ZIKV infection, including mice and non-human primates.     

An Immunocompetent Mouse Model of Zika Virus Infection

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Zika Virus Baculovirus-Expressed Virus-Like Particles Induce Neutralizing Antibodies in Mice

The newly emerged mosquito-borne Zika virus (ZIKV) strains pose a global challenge owing to its ability to cause microcephaly and neurological disorders. Several ZIKV vaccine candidates have been proposed, including inactivated and live attenuated virus vaccines, vector-based vaccines, DNA and RNA vaccines. These have been shown to be efficacious in preclinical studies in mice and nonhuman primates, but their use will potentially be a threat to immunocompromised individuals and pregnant women. Virus-like particles (VLPs) are empty particles composed merely of viral proteins, which can serve as a safe and valuable tool for clinical prevention and treatment strategies. In this study, we used a new strategy to produce ZIKV VLPs based on the baculovirus expression system and demonstrated the feasibility of their use as a vaccine candidate. The pre-membrane (prM) and envelope (E) proteins were co-expressed in insect cells and self-assembled into particles similar to ZIKV. We found that the ZIKV VLPs could be quickly and easily prepared in large quantities using this system. The VLPs were shown to have good immunogenicity in immunized mice, as they stimulated high levels of virus neutralizing antibody titers, ZIKV-specific IgG titers and potent memory T cell responses. Thus, the baculovirus-based ZIKV VLP vaccine is a safe, effective and economical vaccine candidate for use against ZIKV.