Human immunodeficiency virus infection of T-lymphoblastoid cells reduces intracellular pH.

Alterations in plasma membrane function are induced by many cytopathic viruses, including human immunodeficiency virus type 1 (HIV-1). These alterations can result in changes in the intracellular content of ions and other small molecules and can contribute to cytolysis and death of the infected cell. The pH-sensitive fluorescent probe 2',7'-bis(2-carboxyethyl)-5,6-carboxyfluorescein-acetoxymethyl ester was used to quantitate intracellular pH (pHi) in HIV-1-infected T cells. Infection of cells from the CD4+ T-lymphoblastoid line HUT-78 (RH9 subclone) with HIV-1 strain LAI resulted in a significant decrease of pHi, from approximately 7.2 in mock-infected cells to below 6.7 by day 4 after infection, when cells were undergoing acute cytopathic effects. The pHi in persistently infected cells that survived the acute cytopathic effects of HIV-1 was approximately 6.8 to 7.0. Studies with amiloride, an inhibitor of the Na+/H+ exchange system, suggest that HIV-1-induced intracellular acidification in lymphocytes is due, in part, to dysfunction of this plasma membrane ion transport system. The alterations in pHi may mediate certain cytopathic effects of HIV-1, thereby contributing to depletion of CD4+ T lymphocytes in patients with AIDS.

Alteration of intracellular potassium and sodium concentrations correlates with induction of cytopathic effects by human immunodeficiency virus.

Increases in intracellular concentrations of potassium ([K+]i) and sodium ([Na+]i) occur concomitantly with cytopathic effects induced in a CD4+ T-lymphoblastoid cell line acutely infected by human immunodeficiency virus (HIV). This [K+]i increase was greater in cells infected by cytopathic HIV strains than in cells infected by less cytopathic strains. T cells persistently infected by HIV had an increased [K+]i but displayed an [Na+]i similar to that of mock-infected cells. HIV induced increases in [K+]i and [Na+]i after cytopathic infection of human peripheral blood mononuclear cells, but the magnitude of the Na+ changes did not correlate with the extent of the cytopathic effect. Enhanced movement of cations may osmotically drive water entry, resulting in balloon degeneration and lysis of HIV-infected cells. These observations offer potential approaches for antiviral therapies.

Reduction of human immunodeficiency virus production and cytopathic effects by inhibitors of the Na+/K+/2Cl- cotransporter.

Infection of CD4+ T-lymphoblastoid cells by cytopathic strains of HIV-1 results in an increase in cell volume that leads to lysis and cell death. The increase in volume is attributable in part to an HIV-induced increase in intracellular monovalent ion concentrations mediated by the plasma membrane-associated Na+/K+/2 Cl- cotransporter. Loop diuretics, which inhibit cotransporter activity, blocked HIV-induced HIV production and cytopathic effects at physiologically employed concentrations.

Measles virus replication in lungs of hispid cotton rats after intranasal inoculation.

Hispid cotton rats were inoculated intranasally with either measles virus (MV) Edmonston, a multipassaged, tissue culture-adapted strain of MV, or with one of three clinical MV isolates that had limited passages (three to five times) in tissue culture cells. MV Edmonston was recovered from the lungs of every (n = 37) hispid cotton rat inoculated with this virus for at least 7 days after virus inoculation. Peak pulmonary titers occurred on Day +4 (3.3-4.4 log10/g lung). Scattered areas of inflammation were observed interstitially in lung sections from infected animals stained with hematoxylin and eosin, and a similar pattern of diffuse fluorescence was seen in cryostat sections stained with an indirect fluorescent antibody procedure specific for virus antigens. Fluorescent antibody and virus isolation studies on lung lavage cells both suggested that lung leukocytes were a primary target of the virus. In contrast to these findings, virus was isolated only sporadically from hispid cotton rats inoculated with any of the clinical measles virus isolates. Despite the restricted growth of MV in these animals, cotton rats may be useful for studying certain aspects of measles virus pathogenesis and for screening potential antiviral compounds in vivo.