Equine infectious anemia virus derived from a molecular clone persistently infects horses

A full-length of molecular clone of equine infectious anemia virus (EIAV) was isolated from a persistently infected canine fetal thymus cell line (CfZTh). Upon transfection of equine dermis cells, the clone, designated CL22, yielded infectious EIAV particles (CL22-V) that relicated in vitro in both Cf2Th cell and an equine dermis cell strain. Horses Infected with CL22-V developed an antibody response to viral proteins and possessed viral DNA in peripheral blood mononuclear cells, as determined by polymerase chain reaction assays. In addition, horses infected with CL22-V became persistently infected and were capable of transmitting the infection by transfer of whole blood to uninfected horses. However, CL22-Y, like the parental canine cell-adapted virus, did not cause clinical signs in infected horses. Reverse transcriptase assays of CL22-V- and virulent ElAY-infected equine mononuclear cell cultures indicated that the lack of virulence of CL22-V was not due to an inability to infect and replicate in equine mononuclear cell in vitro.