Real-time reverse transcriptase PCR for the endogenous koala retrovirus reveals an association between plasma viral load and neoplastic disease in koalas
Rachael Tarlinton,1 Joanne Meers,2 Jon Hanger3,4 and Paul Young1
1Department of Microbiology and Parasitology, School of Molecular and Microbial Sciences, University of Queensland, St Lucia 4072, Queensland, Australia
2School of Veterinary Science, University of Queensland, St Lucia 4072, Queensland, Australia
3Dreamworld, Coomera, Queensland, Australia
Koala retrovirus (KoRV) is a newly described endogenous retrovirus and is unusual in that inserts comprise a full-length replication competent genome. As koalas are known to suffer from an extremely high incidence of leukaemia/lymphoma, the association between this retrovirus and disease in koalas was examined. Using quantitative real-time reverse transcriptase PCR it was demonstrated that KoRV RNA levels in plasma are signiﬁcantly increased in animals suffering from leukaemia or lymphoma when compared with healthy animals. Increased levels of KoRV were also seen for animals with clinical chlamydiosis. A signiﬁcant positive association between viral RNA levels and age was also demonstrated. Real-time PCR demonstrated as much as 5 log variation in KoRV proviral DNA levels in genomic DNA extracted from whole blood from different animals. Taken together these data indicate that KoRV is an active endogenous retrovirus and suggests that it may be causally linked to neoplastic disease in koalas.