Stable expression of HIV-1 Nef induces changes in growth properties and activation state of human astrocytes

Objective: Nef was shown to be the predominant viral protein expressed in H IV-1-infected astrocytes in vivo and in vitro suggesting a distinct role of Nef in this cell type. Nef-induced activation of T cells is well described , whereas the functional activities of Nef in astrocytes are unknown. Our a im was to examine the effect of Nef on growth properties and activation of astrocytes. Design: Human Nef-expressing astrocytic cell lines were established by stab le transfection With different wild-type and mutant nf genes derived from l aboratory isolates and brain tissue. Methods: Nef-expressing astrocytes were characterized in terms of growth pr operties (proliferation, growth in soft agar, focus formation) and morpholo gy. Apoptotic cell death and expression of activation markers were determin ed by fluorescent antibody cell sorting. Results: Astrocytic cell lines revealed persistent Nef expression - detecta ble at the levels of mRNA and protein - and showed altered growth propel-ti es and morphology. Elevated expression of activation markers such as glial fibrillary acidic protein and CD88 (complement receptor C5a) was observed; these are regarded as markers for inflammatory processes in the brain. This effect was independent of the nef type or the expression level of the Nef protein. In contrast with previous reports no evidence for increased apopto tic cell death was found in astrocytes expressing Nef stably. Conclusions: Our findings suggest that Nef changes the cellular properties of astrocytes, thus contributing to astrocyte activation and induction of a strogliosis in the central nervous system of individuals with AIDS. (C) 199 9 Lippincott Williams & Wilkins.