Five healthy horses were inoculatedwith the equine infectious anemia virus donkey leucocyte attenuated vaccine(DLA-EIAV), the virus derived from infectious molecular clone of DLA-EIAV(vOK8226) and the chimeric virus based on vOK8226 with substitution of LTR from virulent EIAV(vOKVltr), respectively. On day 220 post-inoculation, the five inoculated horses and two control horses were challenged with the virulent EIAV, all the horses were subjected to clinical observation, tissue patho- logical determina...