Past and Current Projects
Virus Emergence
Viruses emerge by gaining mutations permitting infection of new hosts. However, emergence cannot be sustained unless certain parameters are met. We are trying to determine what precisely these parameters are. One important characteristic is virus transmission rate. In a report published in The American Naturalist, we describe how manipulating transmission rate can allow virus persistence or lead to virus extinction. Fig. 3 from Dennehy et al. 2006 shows viral persistence at several transmission rates.
The work establishes the basic source-sink dynamics of populations of phi6 growing on native and novel hosts. We can use the data generated by the paper to predict population persistence for phages at given transmission rates and to construct sources and sinks in future experiments.
Figure 3: Population sizes after each cycle of growth and transmission in serial passage experiments in three host regimes. A, Populations passaged on PP at transmission rates from 108 to 105; B, populations passaged on ERA at transmission rates from 107 to 105; C, populations passaged on alternating hosts, beginning with PP, at transmission rates from 108 to 105. Points are offset for clarity. Error bars are1 SD.
Virus Traps
Viruses will bind to any cell possessing the correct receptor. This leaves them vulnerable to engineered cells expressing the correct receptor, but are otherwise not viable for productive infection. In work published in Ecology Letters, we described a mathematical model to predict the effectiveness of virus traps in driving viruses to extinction. We validated the model using bacteriophage phi6 and a naturally occuring trap host. We found that traps could indeed drive viruses to extinction. The figure below accompanied a New York Times article about the work.
Black Hole Sinks
Viruses emerge by gaining mutations permitting them to infect new hosts. Usually emerging viruses have low fitness on the new hosts, thus exist in sink populations (i.e. those where deaths > births). Viruses in sinks will eventually go extinct without local adaptation. We investigated the process of local adaptation when migration into the population was permitted. We used three different sources of migrants: ancestors, evolved on native host, evolved on novel host. Surprisingly, as long as genetic variation was entering population, adaptation to novel host was observed.
