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(a) What we have—natural viruses that infect normal cells in the context of their natural infection pathway
586389.fig.001b
(b) What we want—oncolytic viruses that attack tumor cells at their primary and associated sites of metastasis
Figure 1: Why we need directed evolution. (a) The starting point of all oncolytic viruses are naturally occurring viruses which infect normal cells they encounter along their standard route of entry. (b) The goal is to develop oncolytic viruses which selectively infect and replicate in cells they would never naturally encounter.