THE BOVINE IMMUNODEFICIENCY-LIKE VIRUS (BIV) IS TRANSCRIPTIONALLY ACTIVE IN EXPERIMENTALLY INFECTED CALVES

We have studied the infection by the bovine immunodeficiency-like viru s (BIV) in three experimentally infected calves, by polymerase chain r eaction (PCR) and reverse transcription-polymerase chain reaction (RT- PCR), from the peripheral blood mononuclear cells (PBMC). Two primer p airs located in the gag and pol regions of the viral genome allowed to detect the viral genomic DNA by PCR, as well as the unspliced genomic viral RNA transcript, by RT-PCR. We also present the evidence of the presence in peripheral blood mononuclear cells (PBMCs) of a mRNA trans cript of the regulatory trans-activator tat gene, according to the spl icing pattern of the viral genome, by use of reverse transcription fol lowed by nested PCR. The active expression of the virus in these anima ls was further assessed by the sequential rescue of the virus from uns timulated PBMCs in cell culture, from 4 weeks until 15 months followin g the infection.