Abstract
Transspecies transmission of retroviruses is a frequent event, and the human immunodeficiency virus-1 (HIV-1) is a well-known example. The gibbon ape leukaemia virus (GaLV) and koala retrovirus (KoRV), two gammaretroviruses, are also the result of a transspecies transmission, however from a still unknown host. Related retroviruses have been found in Southeast Asian mice although the sequence similarity was limited. Viruses with a higher sequence homology were isolated from Melomys burtoni, the Australian and Indonesian grassland melomys. However, only the habitats of the koalas and the grassland melomys in Australia are overlapping, indicating that the melomys virus may not be the precursor of the GaLV. Viruses closely related to GaLV/KoRV were also detected in bats. Therefore, given the fact that the habitats of the gibbons in Thailand and the koalas in Australia are far away, and that bats are able to fly over long distances, the hypothesis that retroviruses of bats are the origin of GaLV and KoRV deserves consideration. Analysis of previous transspecies transmissions of retroviruses may help to evaluate the potential of transmission of related retroviruses in the future, e.g., that of porcine endogenous retroviruses (PERVs) during xenotransplantation using pig cells, tissues or organs.
Highlights
IntroductionWhereas some recent transspecies transmission of retroviruses, for example, the transmission of a lentivirus from chimpanzees to humans resulting in the human immunodeficiency virus-1 (HIV-1)
Whereas some recent transspecies transmission of retroviruses, for example, the transmission of a lentivirus from chimpanzees to humans resulting in the human immunodeficiency virus-1 (HIV-1)or the transmission of a simian immunodeficiency virus (SIV) from sooty mangabeys to humans resulting in HIV-2, have been well studied [1], other transspecies transmissions have still not been fully analysed
Since similar sequences have been found in mice, but not in rats and hamsters, it was suggested that porcine endogenous retroviruses (PERVs) originated from mouse endogenous retroviruses approximately three and 10 million years ago [3]
Summary
Whereas some recent transspecies transmission of retroviruses, for example, the transmission of a lentivirus from chimpanzees to humans resulting in the human immunodeficiency virus-1 (HIV-1). Searching for the precursor virus, retroviruses related to KoRV and GaLV have been described in rodents such as South East Asian mice (e.g., Mus caroli [9,10] and Mus dunni [11]), as well as in two subspecies of Melomys burtoni in Australia and Indonesia [12,13]. These viruses are close relatives, it is still difficult to explain how gibbons and koalas, living in such diverse habitats, could be infected with the precursor virus. Vaccination can be difficult in animals carrying an endogenous KoRV which produces a subsequent tolerance against the vaccine [49]
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