Specificity of Drosophila innubila Nudivirus infection in Drosophila cell culture

Viral host range is an important aspect of both viral biology but also the pragmatic issue of producing viral stocks for experimentation. Host range is important both in terms of the species a virus can infect (taxonomy), and the types of host cells the virus can infect (tropism). Nudiviruses are large DNA viruses that infect several arthropods and are generally poorly studied. Several nudiviruses infect Drosophila species including the Drosophila innubila Nudivirus (DiNV). We aimed to identify cell lines that support the replication of DiNV both for the sake of understanding host range, and to develop a system for large scale production of the virus for infection. We utilized cell lines from the focal host, D. innubila, as well as available cell lines from D. virilis and D. melanogaster and inoculated with both a wild-collected pool of "naïve" virus and a D. innubila cell culture-adapted isolate. We found that virus from wild caught flies infected cells from the 3 cell lines and replicated its genome, but the passage 1 fluids from these infections were unable to reinfect upon introduction to new cells. In contrast, a cell culture-adapted strain of DiNV infected the same Drosophila cells (though relatively poorly in D. melanogaster cells) and produced infectious progeny that infected new cells. Thus, our cell culture-adapted virus developed the ability to infect broadly and produce infectious virions.