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 HIV-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 aim was to examine the effect of Nef on growth properties and activation of astrocytes.


METHODS
Human Nef-expressing astrocytic cell lines were established by stable transfection with different wild-type and mutant nef genes derived from laboratory isolates and brain tissue.


METHODS
Nef-expressing astrocytes were characterized in terms of growth properties (proliferation, growth in soft agar, focus formation) and morphology. Apoptotic cell death and expression of activation markers were determined by fluorescent antibody cell sorting.


RESULTS
Astrocytic cell lines revealed persistent Nef expression--detectable at the levels of mRNA and protein--and showed altered growth properties 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 apoptotic 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 astrogliosis in the central nervous system of individuals with AIDS.
Kohleisen
B
B
GSF-National Research Center for Environment and Health, Institute of Molecular Virology, Neuherberg, Germany.
Shumay
E
E
Sutter
G
G
Foerster
R
R
Brack-Werner
R
R
Nuesse
M
M
Erfle
V
V
D017209:Apoptosis; D001253:Astrocytes / Q000473:pathology* / Q000502:physiology / Q000821:virology*; D001483:Base Sequence; D002455:Cell Division; D002460:Cell Line; D017931:DNA Primers / Q000235:genetics; D015870:Gene Expression; D015693:Gene Products, nef / Q000235:genetics; D015754:Genes, nef; D005904:Glial Fibrillary Acidic Protein / Q000502:physiology; D015658:HIV Infections / Q000276:immunology / Q000473:pathology / Q000821:virology; D015497:HIV-1 / Q000235:genetics* / Q000276:immunology / Q000472:pathogenicity*; D006801:Humans; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013601:T-Lymphocytes / Q000276:immunology / Q000821:virology; D014774:Virulence / Q000235:genetics; D054311:nef Gene Products, Human Immunodeficiency Virus
D017931:DNA Primers; D015693:Gene Products, nef; D005904:Glial Fibrillary Acidic Protein; D054311:nef Gene Products, Human Immunodeficiency Virus