Kinetics of human-T cell leukemia virus type 2 (HTLV-2) mRNA expression in PBMCs isolated from infected subjects

The analysis of HTLV-2 expression during the infection process is essential to understand the influence of viral gene products in proliferation, cell cycle and signalling. To date, very little information has been obtained on the profile and temporal regulation of HTLV-2 gene expression in infected cells.

To address this point, time course of transcription of individual HTLV-2 viral mRNAs was evaluated by real time RT-PCR using splice-junction-specific primers. PBMCs from HTLV-2B infected patients were cultured with IL-2 and the level of the different mRNAs analysed at the following time points: 0, 2, 4, 8, 21 and 48 hours.

The results obtained showed an early transcription of tax/rex regulatory transcript, followed by p28-p22/p20 rex-2 and by a gradual and steady increase of gag/pol structural transcripts and of 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 findings 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 the structural mRNAs are expressed at a later time point. Moreover, the level of expression of the accessory genes was lower than that of structural viral genes.

This study identified distinct patterns of expression of HTLV-2 transcripts in infected PBMCs, thus indicating that the control of viral gene expression is highly regulated both in its kinetics and expression level.

Further studies are currently being performed to investigate the kinetics of gene expression of HTLV-2A subtype in transiently transfected human T cells.