NEGATIVE REGULATORS MAY MEDIATE SOME OF THE INHIBITORY EFFECTS OF HIV-1-INFECTED STROMAL CELL-LAYERS ON ERYTHROPOIESIS AND MYELOPOIESIS IN HUMAN BONE-MARROW LONG-TERM CULTURES

This report presents results concerning the potential role of negative regulators in hematopoietic suppression observed in human immunodefic iency virus (HIV)-infected long-term cultures (LTC) of human bone marr ow cells, Confluent stromal cell layers established from human bone ma rrow cells were exposed to HIV-1(ADA), a monocytotropic strain of HIV- 1, A progressive increase in the concentration of HIV-1 p24 antigen in cultures exposed to HIV-1(ADA) demonstrated that there was a producti ve infection, Cells from both noninfected and HIV-infected stromal cel l layers produced factors that stimulated the proliferation of colony- forming units for granulocytes and macrophages (CFU-GM) from noninfect ed CD34(+) cells, In contrast, when noninfected CD34(+) cells were dir ectly cocultured on intact stromal cell layers fewer CFU-GM and burst- forming units for erythroid cells (CFU-GM) were detected in HN-infecte d LTC than in noninfected LTC, One week after the addition of CD34(+) cells, the number of CFU-GM in HIV-infected LTC in six of nine experim ents was reduced compared to noninfected control LTC, In those six exp eriments, the number of CFU-GM was only 53 +/- 5% (SEM) of the number in noninfected LTC, The number of BFU-E in HIV-1-infected LTC was only 46 +/- 5% of the number in noninfected LTC (n = 5), There were fewer BFU-E in HIV-1-infected LTC, whether or not there was a reduced number of CFU-GM, Neutralizing antibody to tumor necrosis factor alpha (TNF- alpha) had no effect on the number of BFU-E in HIV-infected LTC, The n umber of BFU-E, however, was 2.1 +/- 0.2-fold greater (n = 3) in HIV-i nfected LTC incubated with neutralizing antibody to interferona-alpha. In HIV-infected LTC with decreased numbers of CFU-GM, the number of C FU-CM was approximately 2-fold greater after incubation of HIV-infecte d LTC with anti-interleukin-4 (IL-4), The effect of anti-TNF-alpha was variable, and anti-transforming growth factor-beta had no effect on t he number of CFU GM in HIV-infected LTC, After 2 weeks, the number of CFU-GM in HN-infected LTC incubated with anti-IL-4 and anti-TNF-alpha was 2- to 4-fold greater than in untreated HIV-infected LTC, Antibody treatment did not promote an increase in the number of CFU CM in nonin fected LTC or in LTC in which CFU-GM numbers were not reduced after HI V infection. These results demonstrate that some cells in the stromal cell layers of LTC were targets for HIV-1(ADA), and that HIV-infected stromal cell layers suppressed or delayed the production of both CFU-G M and BFU-E. These results also suggest that hematopoietic suppression in HIV-infected LTC may be mediated by growth-in-hibitory cytokines t hat are different for erythropoiesis and myelopoiesis.