Discovery of insect and human dengue virus host factors

Abstract

Dengue fever (DF) is the most frequent arthropod-borne viral disease of humans, with almost half of the world's population at risk of infection1. The high prevalence, lack of an effective vaccine, and absence of specific treatment conspire to make DF a global public health threat1, 2. Given their compact genomes, dengue viruses (DENV 1-4) and other flaviviruses likely require an extensive number of host factors; however, only a limited number of human, and an even smaller number of insect host factors have been identified3-10. To discover insect host factors required for DENV-2 propagation, we carried out a genome-wide RNA interference screen in Drosophila melanogaster cells using a well-established 22,632 dsRNA library. This screen identified 116 candidate dengue virus host factors (DVHFs) (Supplementary Fig. 1). While some were previously associated with flaviviruses (e.g., V-ATPases and alpha-glucosidases)3-5, 7, 9, 10, most DVHFs were newly implicated in DENV propagation. The dipteran DVHFs had eighty-two readily recognizable human homologues and, using a targeted siRNA screen, we showed that forty-two of these are human DVHFs. This indicates remarkable conservation of required factors between dipteran and human hosts. This work suggests novel approaches to control infection in the insect vector and the mammalian host.

RNAi screening reveals requirement for host cell secretory pathway in infection by diverse families of negative-strand RNA viruses

“…The advent of siRNA technology and the availability of genome-wide siRNA libraries have been useful in identifying host factors required for influenza virus, an NS RNA virus, and several positive-strand RNA viruses, as well as HIV (10)(11)(12)(13)(14)(15)(16)(17)(18)(19). The lack of similar studies with other NS RNA viruses has limited the understanding of the role of host cell factors in replication of these viruses.…”

Replication of not-known-vector flaviviruses in mosquito cells is restricted by intracellular host factors rather than by the viral envelope proteins

“…Permissivity to flavivirus infection is determined by many different hostcell factors that may either be required for efficient infection of mammalian and arthropod cells (host susceptibility factors, HSFs) or restrict infection in certain cells (host resistance factors, HRFs) (Krishnan et al, 2008;Sessions et al, 2009). For example, .40 candidate HSFs have been identified that are required for growth of the mosquito-borne dengue virus (DENV) type 2 in arthropod, but not in mammalian, cells (Sessions et al, 2009). It is largely unknown which viral determinants are responsible for host tropism and vector specificity, i.e.…”

“…Many flaviviruses have evolved unique strategies to adapt to the special requirements of their specific target cells (reviewed recently by Fernandez-Garcia et al, 2009). Permissivity to flavivirus infection is determined by many different hostcell factors that may either be required for efficient infection of mammalian and arthropod cells (host susceptibility factors, HSFs) or restrict infection in certain cells (host resistance factors, HRFs) (Krishnan et al, 2008;Sessions et al, 2009). For example, .40 candidate HSFs have been identified that are required for growth of the mosquito-borne dengue virus (DENV) type 2 in arthropod, but not in mammalian, cells (Sessions et al, 2009).…”

“…In addition, members of the NF90/NFAR protein group were shown to regulate replication of the related pestiviruses by specific association with regulatory elements in the 59 and 39 untranslated regions (Isken et al, 2003), whilst several HSFs have been shown to regulate hepatitis C virus replication (Okamoto et al, 2006). However, interestingly, several (putative) RNA-binding proteins that allow DENV2 to replicate in Drosophila (dipteran) cells, but are dispensable as HSFs in human hepatoma cells (Sessions et al, 2009), have been identified. Moreover, recently the innate antiviral immune system of invertebrates, namely the RNA interference (RNAi) pathway of recognizing and silencing double-stranded viral RNA, has been shown to play a major role for the replication of DENV and WNV in their respective mosquito hosts (Brackney et al, 2009;Sanchez-Vargas et al, 2009).…”

Expression of dengue virus NS3 protein inDrosophilaalters its susceptibility to infection

“…To achieve this goal, and to better characterize the innate immune response against the virus, several approaches have been followed using either Aedes or Drosophila models. These approaches include genome wide RNAi interference screen in Drosophila, 6 whole-genome microarray in Aedes aegypti 7 and evolutionary dynamics of immune-related genes and pathways in disease-vector mosquitoes. 8 Importantly, the antimicrobial Toll pathway was shown to control Dengue virus infection in Aedes aegypti 9-11 but was not required for Wolbachia mediated dengue virus interference in Drosophila.…”