Concerns regarding vaccination as a management strategy against koala retrovirus

Koalas are of great cultural, ecological and economic significance to Australia. However, they are in steep decline throughout much of their geographic range, with the recently endogenized koala retrovirus (KoRV) presumed to be a contributing factor. Olagoke, et al. 1 have proposed vaccination against KoRV as a suitable control mechanism to reduce the severity of KoRV infections and suggest that their recombinant vaccine is effective at invoking a neutralising immune response and significantly reducing viral loads. Here, we report the findings of our own attempts to detect antibodies specific to the KoRV envelope protein (Env) in infected animals. Antibodies against Env were undetectable in all animals, as would be expected in the case of an endogenous virus antigen which should proceed towards a pathway of self-tolerance. This finding calls into question the results of Olagoke, et al. 1, and prior work by this team 2,3. Following a critical review of this work 1-3, we have identified a number of assay inaccuracies and possible over interpretations of the data and conclude that further work to develop and test a vaccine against KoRV in koalas is not supported by evidence.