Myra Jennings

Human immunodeficiency virus type 1 (HIV-1) fusion with model membranes : kinetic analysis and the role of lipid composition, pH and divalent cations

The kinetics and extent of HIV-1 fusion with model membranes was studied. HIV-1 was labeled with octadecyl rhodamine B chloride, and fusion was monitored continuously as the dilution of the probe into target membranes. The results were analyzed by a mass action model which yielded good simulations and predictions for the kinetics and final extents of fluorescence increase. The model determined the percent of virions capable of fusing and rate constants of fusion, aggregation and dissociation. Ultrastructural analysis of the virus and reaction products by electron microscopy also provided evidence of HIV-1 fusion with membranes lacking CD4. HIV-1 fusion activity depends on the target membrane lipid composition according to the sequence: cardiolipin (CL) > > phosphatidylinositol > CL/dioleoylphosphatidylcholine (DOPC) (3:7), phosphatidic acid > phosphatidylserine (PS), PS/cholesterol (2:1) > PS/PC (1:1), PS/phosphatidylethanolamine (1:1) > DOPC, erythrocyte ghosts. Reduction of pH from 7.5 generally enhances the rate and extent of HIV-1 fusion. Physiologically relevant concentrations of calcium stimulate HIV-1 fusion with several liposome compositions and with erythrocyte ghost membranes. The fusion products of HIV-1 with liposomes consist of a single virus and several liposomes. The mass action analysis revealed that, compared to intact virions, the fusion products show a striking reduction in the fusion rate constant. Like influenza and Sendai viruses, HIV-1 fusion with membranes containing its own envelope glycoprotein(s) is strongly inhibited. Unlike these viruses, HIV-1 fusion is promoted by physiological levels of calcium. HIV-1 fusion with liposomes is qualitatively similar to simian immunodeficiency virus fusion.

Passive immunization of macaques against SIV infection

Passive immunization with plasma from an inactivated‐whole SIVmac vaccine protected monkey conferred complete or partial protection to rhesus macaques challenged intravenously 4 or 18 hours later with 10 AID50 of homologous cell‐free virus. In contrast, passive immunization with inactivated plasma or purified immunoglobulin (Ig) from SIVmac infected asymptomatic monkeys failed to protect any recipients similarly challenged and may have enhanced infection and accelerated disease. Administered 24 hours post challenge, anti‐SIV Ig may also have enhanced the infection.

Characterization of Monoclonal Antibodies that Distinguish Simian Immunodeficiency Virus Isolates from each Other and from Human Immunodeficiency Virus Types 1 and 2

Two monoclonal antibodies (MAbs) against p27 and one against p17 of simian immunodeficiency virus (SIV) from rhesus macaques were produced and characterized by reacting with disrupted, viral antigens on immunoblots. Human immunodeficiency virus type 1 (HIV-1), HIV-2 and SIV isolates from sooty mangabey, stump-tailed macaque, rhesus macaque and African green monkey (SIVSM, SIVStM, SIVMAC and SIVAGM) were used for comparative analysis. The p27 monoclonal antibodies HE3 and FA2 reacted with SIVMAC and SIVSM, but not with HIV-1, HIV-2, SIVStM and SIVAGM. The p17 monoclonal antibodies reacted with SIVMAC and SIVStM, but not HIV-1, HIV-2, SIVSM and SIVAGM. The differential reactivity of these monoclonal antibodies indicated that common conserved antigenic epitopes are shared between SIVMAC and SIVSM with respect to p27 MAbs and between SIVMAC and SIVStM with respect to p17. Since these MAbs reacted differently with the SIV isolates, they are useful reagents for comparative pathogenesis studies for differentiating SIV isolates.

Adhesion of lymphocytic cells to human trophoblast cells in vitro

The adherence of lymphocytic MOLT-4/clone 8 cells and normal human peripheral blood mononuclear cells (PBMCs) to primary cultures of term human syncytiotrophoblast has been characterized. Adherence was measured using a fluorescence-based assay in which leukocytic cells were labelled with calcein-AM. Adherence of MOLT cells to syncytiotrophoblast increased in a time-dependent fashion up to about 4 h after which adhesion decreased. Adhesion was detectable at 4 degrees C but was greatly reduced compared to that seen at 37 degrees C. Binding increased linearly as the ratio of MOLT cells to trophoblast was increased. Scanning and transmission electron microscopy of MOLT cell-trophoblast cocultures revealed lymphocytes adherent to the free microvillous surface of the syncytiotrophoblast masses. MOLT cells also adhered to cytotrophoblast but the extent of binding was lower than to syncytiotrophoblast. Normal human peripheral blood mononuclear cells adhered to syncytiotrophoblast. Preincubation of trophoblast cells with trypsin in the presence of calcium had no effect on subsequent adhesion of MOLT cells. However, preincubation of trophoblast cells with trypsin in the absence of divalent cations reduced subsequent adhesion. Adhesion of MOLT cells to syncytiotrophoblast was dependent on magnesium and calcium. These results show for the first time that lymphocytic cells adhere to isolated human syncytiotrophoblast and raise the possibility that this may be an important phenomenon in vivo.

Neurotoxicity of amphotericin B methyl ester in dogs

Clinical and neuropathologic effects of chronically administered intravenous (iv) amphotericin B mester (AME) were observed in 3 male dogs (2 German shorthaired pointers and 1 pit bull). Each dog rec 6.2-7.3g of AME (299–327 mg/kg body weight) over a period of 11–12 weeks. One dog developed neurologic signs of severe diffuse brain dysfunction and at necropsy all 3 dogs had a marked leukoencephalopathy, most severe in centrum ovale and subcortical white matter of frontal lobes. Brain histopathology included diffuse myelin loss, oligodendrocyte depletion, accumulation of macrophages filled with sudanophilic lipid, fibrillary astrogliosis, and swelling or fragmentation of many axons. Two control dogs administered iv glucose showed no neuropathologic abnormalities. These findings closely resemble the clinical and neuropathologic abnormalities that developed in patients during the first human trial of AME for treatment of fungal infections, but differ from those of animal studies that did not closely simulate the long-term drug administration required for antifungal therapy in humans. It was concluded that before human clinical trial is authorized, experimental protocols for animal studies of drug toxicity should reflect the anticipated human use of the drug, both in dose and duration.

Antigen detection for human immunodeficiency virus.

The recent development of enzyme immunoassay procedures for the direct determination of human immunodeficiency virus (HIV) antigens has been of significant benefit in both clinical and research applications. The historical development of HIV antigen assays as well as their current and future applications for use in the clinical microbiology laboratory are reviewed. A detailed description of selected commercially available assays is presented, and a comparison is made of various parameters, including sensitivity, specificity, and cost. The use of the HIV antigen assay as an alternative to the reverse transcriptase assay in virus culture applications is also discussed. In addition, the diagnostic and prognostic utility of the HIV antigen assay is considered for various patient groups, including neonatal, high-risk asymptomatic, seronegative, and seropositive patient populations. The use of the HIV antigen assay as an adjunct to anti-HIV antibody testing, as well as its utility in assessing the therapeutic efficacy of antiviral drug therapy, is discussed. The biology of HIV antigen expression and modulation of anti-HIV antibody titers during infection are also discussed in terms of two possible models.