North American eastern equine encephalitis virus (EEEV), an Alphavirus in the family Togaviridae, is classified in Category B of the NIH Priority Pathogens List, and as a high consequence livestock pathogen by the USDA because it is highly lethal for humans and equines, and because effective vaccines and therapies are lacking. In a mouse model of neurovirulent disease, EEEV infection induces only low levels of IFN-?, at least in part as a consequence of the failure to productively infect myeloid cells and lymphoid tissues; a critical type I IFN evasion strategy. An early and profound block on EEEV infectivity for myeloid-lineage cells occurs at the level of gene expression from the incoming vira genome (and presumably also translation of progeny genomes), suggesting that the efficiency with which this essential first step in replication is completed contributes significantly to cell/tissue tropism. We have recently published in Nature that: i) translation of the EEEV genome occurs with ~1,000-fold greater efficiency in mesenchymal than in myeloid cells dictated by nucleotide sequences in the 3' non-translated region (NTR); ii) myeloid cell-specific microRNA, miR142-3p, has four potential binding sites in this region and is responsible for this translation inhibition; and iii) on the other hand, the same region of the 3' NTR is required for replication in mosquito cells and mosquitoes. Specifically, we propose to identify and determine the effect of mutations in the EEEV genome that restore translation in mammalian myeloid-lineage cells in vitro and in vivo; and similarly characterize the effects of these mutations on mosquito cell replication capability. We anticipate that these studies will allow the identificatio and disablement of mechanisms utilized by EEEV to avoid IFN-? activity and, therefore, generate immunogenic, live-attenuated vaccine candidates that will not infect mosquitoes. Also, we will identify a highly restrictive miRNA binding domain which can be used for design of antiviral therapeutics. Finally, we anticipate that our findings regarding the tropism-determining activity of the EEEV 3' NTR will be recapitulated in other viruses and, thus, the studies will have broad applicability.
Eastern equine encephalitis virus (EEEV), an Alphavirus in the family Togaviridae, is classified in Category B of the NIH Priority Pathogens List, and as a high consequence livestock pathogen by the USDA. This virus is highly lethal for humans, equines and exotic birds such as emus and ostriches, but effective vaccines and antiviral therapies are lacking. This mosquito-borne virus is endemic to the entire eastern seaboard of North America from Canada to the Gulf Coast and, disturbingly, its endemic range and occurrence in human-feeding mosquitoes is increasing. The long-term goal of our studies is the rational design of antiviral therapeutics and live-attenuated vaccine strains by altering the cell tropism of the virus. We anticipate that immunogenic EEEV strains can be rationally designed by restoring the ability to replicate in myeloid cells (i.e., deleting miR142-3p binding sites) and thus preventing EEEV from avoiding the induction of type I interferon-mediated antiviral responses. Furthermore, miR142-3p could be delivered as a therapeutic to force EEEV replication in myeloid cells thereby attenuating an ongoing infection. Finally, as we expect that many more viruses will be found to have acquired cell-type specific miRNA binding sites for control of tissue tropism, our results may have applicability to many RNA viruses.
| Trobaugh, Derek W; Klimstra, William B (2017) Alphaviruses suppress host immunity by preventing myeloid cell replication and antagonizing innate immune responses. Curr Opin Virol 23:30-34 |
| Trobaugh, Derek W; Klimstra, William B (2017) MicroRNA Regulation of RNA Virus Replication and Pathogenesis. Trends Mol Med 23:80-93 |
| Hyde, Jennifer L; Chen, Rubing; Trobaugh, Derek W et al. (2015) The 5' and 3' ends of alphavirus RNAs--Non-coding is not non-functional. Virus Res 206:99-107 |
