Amino acid mutations of the infectious clone from Chinese EIAV attenuated vaccine resulted in reversion of virulence.

The Chinese equine infectious anemia virus (EIAV) donkey-leukocyte attenuated vaccine (DLV) provides a unique natural model system by which attenuated mechanism and immunological control of lentivirus replication may be studied. We analyzed the critical consensus mutations that occurred during the viral passages in vitro and in vivo for vaccine's preparation. Based on the full-length infectious clone pLGFD3 (EIAV vaccine background) and according to mutations displayed during viral attenuation, we successfully constructed an infectious clones pLG5-3-l in which gag and env genes were point-mutated by overlap PCR mutagenesis strategy. pLG5-3-l was proved to have the ability of effective replication in vitro cells culture systems by Reverse Transcriptase Assay and virion observation under electron microscopy. Results of the in vivo experiments indicated that marked differences occurred between the mutated virus and their parental virus in clinical manifestation and plasma viral replication during 6-month observation period. In contrast to asymptom of animals infected with pLGFD3-V, the mutated virus (pLG5-3-l-V) developed typical clinical progression in the corresponding experimentally infected animals. The results of the distinct differences in clinical profiles and viral dynamics before and after mutation of EIAV infectious clone will help to understand the protective mechanism of Chinese EIAV vaccine and shed light on novel HIV vaccine design.