Properties of a novel DNA virus from the tsetse fly, Glossina pallidipes

Virus particles were isolated from hypertrophied salivary glands of the tsetse fly, Glossina pallidipes collected near Mombasa, Kenya. Purified virus particles were rod-shaped, 57 nm wide by 700 to 1300 nm long. Particle lengths fell into two size classes, with 'short' particles averaging 869 nm and 'long' particles 1175 nm. The virus particles morphologically resembled elongated baculovirus nucleocapsids although, unlike baculoviruses, no fully enveloped virions were found in purified preparations. The particles contained double-stranded DNA which appeared to be linear when analysed by electrophoresis in agarose gels, ethidium bromide-caesium chloride gradient centrifugation or electron microscopy (EM). There was some evidence for the DNA being heterogeneous in size from EM studies and from the observation that restriction enzyme analysis failed to provide a clear profile of DNA fragments. Protein from purified virions contained at least 12 polypeptides with a major component of 39 000 mol. wt. These results suggest that the virus cannot be placed in any of the existing taxonomic groupings of DNA viruses.