HIV Tat protein potentiates in vitro granulomonocytic progenitor cell growth

The direct involvement of hematopoietic progenitor cells in AIDS which results in dysregulated hematopoiesis, probably due to regulatory factors yet to be determined, has been reported by us and others. In this study we demonstrate that the HIV-2 Tat gene product is released in supernatant of HIV-2-infected long-term bone marrow cultures (LTBMC). These Tat-containing supernatants specifically enhanced growth of CFU-GM in agar culture system and this promoting activity was specifically neutralized with anti-Tat antibodies. The use of different recombinant Tat proteins confirmed that Tat has been responsible for enhanced in vitro growth of CFU-GM after HIV-2 infection of LTBMC. Moreover, limiting dilution analysis showed that Tat acts directly on the CD34+ cell population in which it increases the frequency of IL3-responding cells.