Isolation and Characterization of a Novel Gammaherpesvirus from a Microbat Cell Line

Shabman, Reed S.; Shrivastava, Susmita; Tsibane, Tshidi; Attie, Oliver; Jayaprakash, Anitha; Mire, Chad E.; Dilley, Kari E.; Puri, Vinita; Stockwell, Timothy B.; Geisbert, Thomas W.; Sachidanandam, Ravi; Basler, Christopher F.

This study identifies what appears to be the first replication-competent bat gammaherpesvirus, an almost complete standard draft genome, and the first transcript map of a bat herpesvirus. As described in the ATCC product information sheet, the MVI-it cells were isolated from an "interscapular tumor; possibly basal cell" from an "adult female" bat. In addition, "the line was derived from a tumor found in a bat from Frio Cave, Texas. The tumor was in the skin, not attached to underlying muscle or bone." The impetus to perform RNA-seq on the MVI cells was a desire to profile the innate immune response of bat cells to virus infection. The characterization of the innate immune transcriptome will be published elsewhere, but analysis of RNA-seq results led to the serendipitous identification of herpesvirus-like mRNA sequences. The identification of apparent fulllength transcripts for viral structural proteins, including gB, glycoprotein H, major capsid protein, and tegument proteins, as well as proteins involved in virus genome replication, such as DNA polymerase, single-stranded DNA (ssDNA) binding protein, and thymidine kinase, points to ongoing virus replication in the cells. Further evidence for productive infection was obtained from electron microscopy images from the MVI-it cells which show the presence of what appear to be herpesvirus particles. The morphology and intracellular location are consistent with gammaherpesviruses. Although it is possible that cells in the culture harbor virus in a latent form and although we have not determined what percentage of cells contain virus genome, the fact that tissue culture supernatants from the MVI cells could transmit the infection to Vero cells proved the presence of ongoing productive replication as the cells were maintained in culture. Because it was from virus amplified on Vero cells that the full-length genome was determined, we can be certain that the genome sequence derives from an infectious virus. Since the genome sequence corresponds to the transcriptome data obtained in the bat cell line, it is clear that the virus growing on the Vero cells is the same virus that infects the bat cells.