Bats are major reservoirs of deadly human viruses. While retroviruses, such as the human immunodeficiency virus, are among the most significant of virus families that have jumped from animals into humans, whether bat retroviruses have the potential to infect and cause disease in humans remains unknown. We reported the discovery of the first infectious bat retrovirus, the Hervey pteropid gammaretrovirus (HPG), circulating in populations of the Australian black flying fox (Pteropus alecto) (Hayward J, Tachedjian M et al., 2020, PNAS 177(17)). HPG is closely related to the pathogenic koala retrovirus (KoRV) and gibbon ape leukemia virus (GALV). Given the role of bats in viral transmission networks, HPG may pose a threat to other animals of ecological, economic, or domestic importance.
We have generated HPG-specific antibodies and an in vitro replication competent HPG reporter construct (HPG-iGFP) carrying a green fluorescent protein internally encoded within the HPG gag gene. The HPG-iGFP construct alone generates immature, non-infectious, fluorescent viral particles in mammalian cells, and when expressed alongside wild-type HPG, produces infectious, fluorescent hybrid virions (HPG-iGFP-H). Mammalian cells infected with HPG-iGFP-H express Gag-GFP proteins enabling fluorescence-based visualisation and quantification by methods including fluorescence microscopy and high content imaging.
HPG-iGFP is being used to analyse viral protein kinetics and infectivity in diverse mammalian cells. This will enable novel insights into gammaretroviral biology and the range of animal species that may be susceptible to infection by HPG.