Human astrocytes can be infected with HIV-1 both in vivo and in vitro. However, the amount of HIV-1 structural and nonstructural protein production is low compared to that of the macrophage or the microglial cell in the brain. In an in vitro model using human fetal astrocytes, several weeks following infection or transfection, cocultivation with uninfected lymphocytes or stimulation with the cytokines TNF-alpha and IL1-beta will increase viral production from this cell type. In the current work we have demonstrated that phorbol 12-myristate 13-acetate (PMA) also increases HIV-1 p24 production from the primary human astrocyte. Using electrophoretic mobility shift assay (EMSA) in combination with supershift studies using specific antibodies, we demonstrated that PMA, like TNF~alpha increases the p50/p65 form of NF- KB. Furthermore, we also showed that the protein kinase inhibitor H7 inhibits PMA and TNF-alpha associated increases in HIV-1 expression at a time when it has little to no inhibitory effect on the associated increases in p50/p65 NF~kB. Thus, unless p50/p65 NF-kB or its binding is affected by H7 in a manner that cannot be resolved by EMSA, an increase in this form of NF-kB is not always sufficient to increase HIV-1 expression from the astrocyte. We have also shown in vivo infection of astrocytes with HIV-1 expressing the nonstructural protein, nef. This observation was confirmed independently by other investigators in pediatric cases. The role of the infected astrocyte in the pathogenesis of HIV-1-associated encephalopathy continues to be studied. Also, HIV-1 appears to establish a persistent infection in the stromal cells of the lymphoid tissues. The similarities of this infection to that of the astrocyte is being studied at the molecular level targeting NF-kB induction and binding to the HIV-1 LTR. The Laboratory is also investigating the ability of specific RNases to inhibit the multiplication of HIV-1 in lymphocyte cell lines. Onconase and bovine seminal RNase were shown to block infection of HIV-1 in productivity infected cell lines. This block appears from an intracellular mechanism of RNase activity.
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