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Identification of diverse full-length endogenous betaretroviruses in megabats and microbats

Joshua A Hayward12, Mary Tachedjian3, Jie Cui4, Hume Field5, Edward C Holmes46, Lin-Fa Wang378 and Gilda Tachedjian129*

Author Affiliations

1 Retroviral Biology and Antivirals Laboratory, Centre for Virology, Burnet Institute, Melbourne, VIC, 3004, Australia

2 Department of Microbiology, Monash University, Clayton, VIC, 3800, Australia

3 CSIRO Animal, Food and Health Sciences, Australian Animal Health Laboratory, Geelong, VIC, 3220, Australia

4 Sydney Emerging Infections and Biosecurity Institute, School of Biological Sciences and Sydney Medical School, The University of Sydney, Sydney, NSW, 2006, Australia

5 Queensland Centre for Emerging Infectious Diseases, Department of Agriculture, Fisheries, and Forestry, Brisbane, QLD, 4007, Australia

6 Fogarty International Center, National Institutes of Health, Bethesda, MD, 20892, USA

7 Emerging Infectious Disease Program, Duke-NUS Graduate Medical School, Singapore, Singapore

8 Department of Microbiology and Immunology, The University of Melbourne, Parkville, VIC, 3010, Australia

9 Department of Medicine, Monash University, Melbourne, VIC, 3004, Australia

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Retrovirology 2013, 10:35  doi:10.1186/1742-4690-10-35

Published: 27 March 2013



Betaretroviruses infect a wide range of species including primates, rodents, ruminants, and marsupials. They exist in both endogenous and exogenous forms and are implicated in animal diseases such as lung cancer in sheep, and in human disease, with members of the human endogenous retrovirus-K (HERV-K) group of endogenous betaretroviruses (βERVs) associated with human cancers and autoimmune diseases. To improve our understanding of betaretroviruses in an evolutionarily distinct host species, we characterized βERVs present in the genomes and transcriptomes of mega- and microbats, which are an important reservoir of emerging viruses.


A diverse range of full-length βERVs were discovered in mega- and microbat genomes and transcriptomes including the first identified intact endogenous retrovirus in a bat. Our analysis revealed that the genus Betaretrovirus can be divided into eight distinct sub-groups with evidence of cross-species transmission. Betaretroviruses are revealed to be a complex retrovirus group, within which one sub-group has evolved from complex to simple genomic organization through the acquisition of an env gene from the genus Gammaretrovirus. Molecular dating suggests that bats have contended with betaretroviral infections for over 30 million years.


Our study reveals that a diverse range of betaretroviruses have circulated in bats for most of their evolutionary history, and cluster with extant betaretroviruses of divergent mammalian lineages suggesting that their distribution may be largely unrestricted by host species barriers. The presence of βERVs with the ability to transcribe active viral elements in a major animal reservoir for viral pathogens has potential implications for public health.

Retrovirus; Betaretrovirus; Endogenous; Evolution; Bats; Pteropus; Myotis; Rhinolophus