Also just to clear the air a little...
kuru is not a virus, it is a prion! Its mechanism of infection therefore cannot to be translated to HTLV, HIV mechanisms as they are not the slightest bit related!
On the other hand, the importance of Kuru in the medical field is its contribution to understanding Mad cow Disease(a variant of Variant Creutzfeldt-Jakob)and the sheep equivalent 'scrappies'.Symptoms of which are characteristic of that observed in patients that suffered from Kuru!
Kuru however, cannot be a model for explaining species to species transfer of retrovirus simply because it is not a virus!