An endogenous gibbon ape leukemia virus (GALV) identified in a rodent (Melomys sp.) from Indonesia

ABSTRACT
Gibbon ape leukemia virus (GALV) and koala retrovirus (KoRV) most likely originated from a cross-species transmission of an ancestral retrovirus into koalas and gibbons via one or more intermediate as yet unknown hosts. A highly similar virus to GALV has been identified in an Australian rodent (Melomys burtoni) after extensive screening of Australian wildlife. GALV-like viruses have also been discovered in several Southeast Asian species although screening has not been extensive and viruses discovered to date are only distantly related to GALV. We therefore screened 26 Southeast Asian rodent species for KoRV- and GALV-like sequences, using hybridization capture and high-throughput sequencing, in the attempt to identify potential GALV and KoRV hosts. Only one species, an undescribed species of Melomys from Indonesia, was positive yielding an endogenous provirus very closely related to a strain of GALV. The sequence of the critical receptor domain for GALV infection in the Indonesian Melomys sp. was consistent with the susceptibility of the species to GALV infection. The discovery of a GALV in a second Melomys species provides further evidence that Melomys may play a role in the spread of GALV-like viruses, especially since the genus is found in Indonesia, Papua New Guinea and Australia, connecting the home ranges of koalas and gibbons.

IMPORTANCE
The gibbon ape leukemia virus (GALV) and the koala retrovirus (KoRV) are very closely related, yet their hosts are neither closely related nor overlap geographically. Direct cross-species infection between koalas and gibbons is unlikely. Therfore, GALV and KoRV may have arisen via a cross-species transfer from an intermediate host that overlaps in range with both gibbons and koalas. Using hybridization capture and high-throughput sequencing, we have screened a wide range of rodent candidate hosts from Southeast Asia for KoRV- and GALV-like sequences. Only a Melomys species from Indonesia was positive for GALV. We report the genome sequence of this newly identified GALV, the critical domain for infection of its potential cellular receptor and its phylogenetic relationships with the other previously characterized GALVs. We hypothesize that the genus Melomys may have played a key role in cross-species transmission to other taxa.