Emerging infections: Principles of emergence
Program Leader: Mark Denison
SE-RP-001: Platforms for synthesis and testing of emerging zoonotic viruses
Vanderbilt University
Ralph Baric
University of North Carolina
Bats represent approximately 20% of all mammalian species, and are increasingly recognized as vectors for virus evolution and transmission to other species, including humans. A large and constantly increasing number of Bat coronaviruses are being identified, including many with genetic similarity to known human coronaviruses of different groups, specifically SARS-CoV. The overall goals of this project are to dissect the molecular mechanisms of cross-species transmission of coronaviruses, and to develop platform strategies platform that will allow rapid response to natural, inadvertent, or intentional introduction of these viruses into the human population. In this year, using information from sequence databases, we have designed four Bat-CoV genomes from viruses that are non-cultivatable and that represent different virus groups and genetic distance from SARS-CoV. Using the pattern of coronavirus reverse genetics developed in our group, the cDNA fragments for these viruses have been commercially synthesized and are being assembled for transcription and recovery in culture. Over the next year we plan to recover the bat viruses and determine their fitness and adaptation. Spike genes that cover the majority of the range of identified coronaviruses, have been synthesized and will be used to test for virus entry in a Bat-CoV background and to develop broadly neutralizing polyclonal and monoclonal antibodies. We also are testing computer modeling and silico design approaches to predict and test changes in spike that result in trans-species movement of coronaviruses. The designed spike proteins will be tested in the Bat-SRBD background. From the host side, we have obtained ACE2 receptors from different Asian bat species and will test the expression of these receptors and their ability to support productive infection of bat CoVs. Finally, we are testing effect of substitution of known attenuating mutations or deletions in coronavirus replicase gene on the recovery and growth of bat genomes, in order to define conserved interactome networks and broadly applicable attenuating strategies.
SE-NO-001: A genetic systems approach to host-pathogen interactions in orthopoxvirus infections
(Funding for this project ended March 1, 2010)
University of Florida
The orthopoxviruses, smallpox (variola), ectromelia and to a lesser extent monkeypox virus have narrow host ranges but for others (vaccinia and cowpox viruses) the host range is much more extensive. In light of bioterrorism concerns and the question of how viruses "jump" into new host species (both major concerns of SERCEB), it is imperative to study and identify host gene networks that determine and regulate host range. However, little is known about host genes that determine permissiveness, restriction or clinical course of disease. To elucidate such host genes, we will screen a panel of genetically diverse, C57BL/6J and DBA/2J advanced recombinant inbred (BXD ARI) mice for susceptibility to infection beginning with cowpox and ectromelia virus to establish the system and thereafter monkeypox virus. These mice and relevant services are provided by the SAID Core E. The relative permissiveness of a given virus, coupled with the genetic profiling of the infected versus the uninfected animals and an advanced bioinformatic analysis (genenetwork.org) will identify specific host genes/pathways which are critical for resistance/susceptibility of the infections and provide us a better understanding of the relationship between host and pathogen. These results will provide insight into the design of new intervention strategies, new targets for antiviral therapies and provide clues as to how "species jumping" might occur and identify combinations of biomarkers of host susceptibility/resistance genes that can be used for prognostic purposes and a platform for the screening of other pathogens. We propose the following specific aims:
- Aim 1: We will determine the extent by which variation in host genotype modulates the infection phenotype of Ectromelia, Cowpox and Monkeypox viruses. Infection conditions will be standardized and disease evaluated in parental and BXD mice
- Aim 2: We will map quantitative trait loci (QTL), define relevant known and novel networks of candidate genes and pathways that are likely to contribute to disease severity and.
- Aim 3: We propose strategies to confirm and exploit the implicated genes/pathways to develop antivirals and intervention strategies.
