Katherine Conant

The role of chemokines in human immunodeficiency virus infection.

Chemokines that bind to human immunodeficiency virus (HIV) co-receptors are potent and selective inhibitors of HIV infection. Therefore, ever since our discovery of this activity, we have proposed their role in controlling HIV infection as a third arm of the immune response, i.e. in concert with humoral and cellular responses. Research carried out in our laboratory, and performed independently by other groups, has recently strengthened this concept. Here, we critically analyze the evidence indicating the positive contribution of chemokines to HIV infection, their involvement with cognate and innate immunity, and the potential for their use in combating HIV infection.

IFN-γ inhibits AP-1 binding activity in human brain-derived cells through a nitric oxide dependent mechanism

It has been demonstrated that CNS levels of the cytokine IFN-gamma are elevated in association with a number of neuro-inflammatory diseases. In the present study, we have examined the effect of this cytokine on human brain derived cells. We show that prolonged treatment (22 h) of such cells with IFN-gamma inhibits the DNA binding activity of transcription factor AP-1. Furthermore, we show that this effect can be reversed by either N(G)-monomethyl-L-arginine (L-NMMA) or L-N5-(1-iminoethyl)ornithine (L-NIO), competitive inhibitors of nitric oxide synthase activity [Rees et al., 1990]. In addition, we show that treatment of brain-derived cells with the nitric oxide donor 3-morpholinosydnonimine, HCl (SIN-1), or [N-(b-D-glucopyranosyl)-N2-acetyl-S-nitroso-D,L-penicillaminamide] (glyco-SNAP-1), also inhibits the binding activity of AP-1. Together, these results suggest that IFN-gamma can inhibit AP-1 binding activity through a nitric oxide dependent mechanism.

Cell Cultures from Human Fetal Brain Provide a Model for HIV-1 Persistence and Reactivation in the Central Nervous System

Cell cultures derived from human fetal tissues have been used for many years for the laboratory diagnosis of viral infections. In 1971, cultures prepared from human fetal brain were used in the isolation of a human polyomavirus, JCV, which was identified as the etiologic agent for the demyelinating disease, progressive multifocal leukoencephalopathy.1,2 Since JCV infected the oligodendrocyte in the brain, it was thought that JCV also infected the oligodendrocyte or its precursor cell in cultures from fetal brain.3,4 Laboratory investigations of the lineage of fetal brain-derived cells revealed that these precursor cells were difficult to identify and were in small numbers compared with other neural-derived cells, such as astrocytes and neurons.4–6 Since JCV does not infect neurons in the brain or in cultures, astrocytes were implicated as the predominant cell type in these cultures in which JCV multiplied.7 This observation was later confirmed both in situ in histopathological samples and in cell cultures with the establishment of astrocyte cell lines susceptible to JCV infection.8,9 Although cultures from fetal brain tissue demonstrate a diverse population of cell types, it has been possible to prepare cultures highly enriched for astrocytes. It has been these astrocyte-pure cultures from human fetal brain that have served as cell substrates for studies of neurotropism of viral pathogens. With the observation that HIV-1 was neuroinvasive (a characteristic of the lentivirus family), and was demonstrated in patients with dementia, laboratory and clinical investigations began to determine whether HIV-1 was also neurotropic, i.e., able to infect neural-derived cells. Astrocyte cell cultures from human fetal brain were used to initiate these studies.

Characterization of the natural history of HIV-1 infection of astrocytes in the developing pediatric nervous system

1 Medical University of South Carolina, Charleston, SC; 2 Flinders Medical University, Adelaide, Australia: 3 Univ. of Nebraska Mediil Center, Omaha, NE There are increased numbers of activated mononuclear phagocytes, some which are HIV-infected, and astrocytosls in HIV encephalitis. It is postulated that these activated glia produce neurotoxins. SCID injected intracerebrally with HIV and human peripheral blood mononuclear cells, develop pathokqy resembling HIV encephalitis in humans. There are activated, HIV-infected human macrophages and gliosis. Astrocytosis correlates with the presence of virus and HIVinfected human macrophages. PCR of tissue distant from the inoculation site reveals HIV gag mRNA in more than 70% of brains, demonstrating the pervasiveness of HIV. Nef and tat/rev mRNA are also present. This model provides insights into the relationships between mononuclear phagocytes, HIV infection, cytokine production and gliosis.