Tat-induced Promoter Activation Of The Equine Infection Anemia Virus Long Terminal Repeat

Equine infectious anemia virus (EIAV), a lentivirus within the Retroviridae family, is the causative agent of equine infectious anemia (EIA). The Chinese donkey leukocyte attenuated strain of EIAV (EIAV-DLA) was the only successful lentivirus vaccine up to now, which has been applied extensively in China against EIA. EIAV-DLA can serve as a model for study on lentivirus vaccines. The EIAV proviral genomic long-terminal repeat (LTR) is a eukaryotic promotor, which plays an important regulatory role on transcription and replication of the virus.There are two sites mutations occured in the LTR of the Chinese EIAV attenuated vaccine during its attenuation process from a wide type strain. One located at the beginning of TAR, which changed from A to G; another is the appending site of poly (A) which changed from CA to AA. Here, we use a CAT report gene to evaluate the promoter activety of LTRs from EIAV wide type strain (EIAV-LN), donkey leukocyte attenuated EIAV (EIAV-DLA), donkey fetal dermal cell attenuated EIAV ( EIAV-FDD), as well as two mutated LTR clones. EIAV trans-activator protein (Tat) was expressed in mammalian expressing vector pCDNA3.1(+) and was co-transfected with different LTR plasmids in the donkey fetal dermal cells. The CAT assay showed tat can specifically increase promoter activities of EIAV-FDD LTR, mutated FDD LTRs, but not of LTR from EIAV-DLA. The mutations in the TAR and poly (A) did not affect the activities induced by Tat, suggesting the rest part sequences of LTR may play a important role on Tat-LTR interaction.