Higher Transactivation Activity Associated with LTR and Tat Elements from BF Intersubtype Recombinant Variants

GABRIELA TURK*,; M CAROBENE,; A MONCZOR,; A RUBIO,; M GOMEZ-CARRILLO,; H SALOMON

Denver, CO -USA-

Conferencia; 13th Conference on Retroviruses and Opportunistic Infections; 2006

Foundation for Retrovirology and Human Health

Background:  In spite of extensive molecular and epidemiological data about HIV-1 circulating recombinant forms (CRF), the implications of recombination are still not clear for accessory protein biological activities. We therefore studied transcriptional activity associated to the long terminal repeat (LTR) and Tat structures from the BF intersubtype recombinant virus.  Methods:  We included in this study, 25 samples from HIV-infected patients. LTR and Tat coding region were polymerase chain reaction (PCR)-amplified and sequenced. Tat primary structure of 23 of these samples, corresponding to BF recombinants, was analyzed in search of polymorphisms at active domains. Phylogenetic analysis of LTR was performed and sites for transcription factors binding were investigated. LTR and Tat of representative samples were cloned into a GFP-reporter and an expression vector, respectively. After co-transfection of 293T cells, GFP expression was analyzed by flow cytometry; t test was used for statistical analysis.   Results:  Of 23 samples previously characterized as BF recombinants, 22 showed a recombination breakpoint within the tat coding region. LTR region from 14 of 25 BF samples clustered with the F subtype while the remaining clustered with the B subtype. At both HIV regions, major active domains were conserved, when compared with F and B subtypes consensus, although characteristic polymorphisms were observed. At the functional level, LTR BF and Tat BF showed the strongest activity, while LTR B and Tat BF turned out to be the weaker combination (p = 0.004 and p = 0.001 when compared to LTR B / Tat B, respectively). Conclusions:  Data presented here show transcriptional differences associated with the LTR and Tat coding region from BF recombinants circulating in Argentina. Although LTR and Tat sequences were thoroughly studied and several changes were observed, no direct relationship between these changes and transcriptional level differences could be established. This improvement might be a consequence of the recombination process between 2 different HIV-1 subtypes. Selection forces would have favored the spreading of these recombinant forms. To our knowledge, this is the first work that shows higher transcriptional activity of a widely spread HIV-1 circulating recombinant form than its pure subtype counterpart.