Time course of Human-T cell Leukemia Virus type 2 (HTLV-2) gene expression in PBMCs from infected patients

The analysis of HTLV expression during the infection process is essential to understand the influence of viral gene products in proliferation, cell cycle and signalling. Very little information has so far been obtained on the quantification and timing of HTLV-2 viral transcription, therefore the aim of the study was to further investigate the kinetics of different HTLV-2 transcripts. The time course of transcription of the viral mRNAs, tax/rex, gag/pol, env, p28- p22/p20 rex-1 and -2, p10/p11 and p?, was evaluated using splice-junction-specific primers to quantify all HTLV-2 transcripts by real time RT-PCR. To this end, PBMCs from HTLV-2B infected patients were cultured with IL-2 and mRNA analysed at different time points: 0, 2, 4, 8, 21 and 48 hours. The results obtained showed an early transcription of tax/rex, followed by p28- p22/p20 rex-2 and by a gradual and steady increase of gag/pol and p28- p22/p20 rex-1. The level of expression of gag/pol and p28- p22/p20 rex-2 was about 103-104 fold higher than tax/rex and p28- p22/p20 rex-1. These results indicate that the expression of different HTLV-2 genes follows a distinct timing in PBMCs isolated from infected patients. The regulatory transcripts are the first to be expressed whereas structural ones are expressed at a later time point. Moreover, the level of expression of accessory genes was significantly lower than that of structural viral genes. In conclusion, distinct patterns of expression of HTLV-2 were found in infected PBMCs thus indicating that the control of gene transcription is highly regulated both in its kinetics and expression.