The mechanisms of HIV-induced bone marrow abnormalities are not well understood. In order to delineate the cell type/s susceptible to HIV-1 infection within the bone marrow, and to determine the effects of infection on stromal functions, we have utilized the bone marrow stromal progenitor cells. Human bone marrow cells were cultured in the presence or absence of HIV-1 (RF-strain) exposure. Productive infection was monitored each week by determining p24 levels in the culture supernatants. Although, the presence of provirus was detected by PCR amplification of stromal cell DNA using HIV-1 specific primers, the p24 levels were undetectable after the 2nd week. The latent virus, however, could be rescued from the infected bone marrow cells, upon co-culturing with MT-4 cells. A peak increase in p24 levels was observed within a week of co-culturing. This demonstrated a persistent but non-productive infection of the bone marrow stroma. Combined in situ hybridization for HIV-1 RNAs, and immuno-staining for specific cell surface markers, delineated the infected cell type. HIV-1 specific RNAs were observed predominantly in CD83(a dendritic cell specific marker) positive cells. Another rare cell population, morphologically distinct from dendritic cells, was also positive for HIV-1, however, the identity of these cells was not further characterized. The CD83+ cells also expressed the HIV-1 Tat protein as evident by immunostaining with a polyclonal anti-Tat antibody. This suggested a putative role for the Tat protein, in causing stromal cell dysfunctions. The effect of exposure to viable or heat inactivated HIV-1, or to recombinant Tat protein, on the growth of distinct stromal progenitor colonies were monitored at the 2nd and at the 4th week. Both the number and the size of stromal colonies were significantly suppressed (30-50%) upon exposure to viable HIV-1, as well as to the Tat protein. The mRNA levels for cytokines (TNF-, MIP-1 , IL-1 , IL-6 and TGF- 1), were evaluated by semi-quantitative RT-PCR and were found to be 200,120,180,150 and 83 percent of control, respectively. These studies suggested that HIV-1 can predominantly infect dendritic progenitor cells within the bone marrow stroma, and may impair their self-renewal capability and hematopoietic supportive functions. These studies also implicate a novel role for the Tat protein in both HIV-1 latency, and pathogenesis within the stroma] microenvironment.
|Original language||English (US)|
|Issue number||11 PART II|
|State||Published - Dec 1 2000|
ASJC Scopus subject areas
- Cell Biology