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Biomedical subjects

W E Robinson

Publications and source records attributed to W E Robinson.

At least 37 records · Page 2Linked to original sources
PubMed1998

Resistance to the anti-human immunodeficiency virus type 1 compound L-chicoric acid results from a single mutation at amino acid 140 of integrase.

L-Chicoric acid is an inhibitor of human immunodeficiency virus type 1 (HIV-1) integrase in vitro and of HIV-1 replication in tissue culture. Following 3 months of selection in the presence of increasing concentrations of L-chicoric acid, HIV-1 was completely resistant to the compound. Introduction of the mutant integrase containing a single glycine-to-serine amino acid change at position 140 into the native, L-chicoric acid-sensitive virus demonstrated that this change was sufficient to confer resistance to L-chicoric acid. These results confirm through natural selection previous biochemical studies showing that L-chicoric acid inhibits integrase and that the drug is likely to interact at residues near the catalytic triad in the integrase active site.

Amino Acid Substitution↗
PubMed1998

Calcium speciation and exchange between blood and extrapallial fluid of the quahog Mercenaria mercenaria (L.).

Calcium and small organic molecules (e.g., tyrosine, MW 181 Da) introduced into the extrapallial fluid (EPF) of the quahog Mercenaria mercenaria exhibit rapid fluxes across the outer mantle epithelium and are distributed throughout the circulatory system within 3 h. Larger molecules (e.g., bovine serum albumin, MW 66,000 Da) are less readily exchanged between EPF and blood. The protein compositions of blood plasma and EPF are different, with at least seven protein bands expressed more prominently in the EPF. Equilibrium dialysis experiments reveal that Ca2+ constitutes only 2% of the total Ca in plasma; most of the Ca (85%) is bound to macromolecules, and the remaining 13% is present as dialyzable low molecular weight moieties. This distribution cannot be explained by speciation of inorganic Ca alone, since the MINTEQA2 equilibrium speciation model predicts that 79%-86% of the Ca should be present as Ca2+, with the remainder as CaSO4 (20%-13%). However, inclusion of a weakly Ca-binding organic molecule (log10 Ka approximately 2 M-1) into MINTEQA2 could fully reconcile modeling with experimental measurements. Results suggest that calcium transport in blood plasma and EPF is mediated by a suite of proteins and small organic ligands with a low affinity for Ca.

Animals↗
PubMed1997

Lymphokine-activated cytotoxicity in peripheral blood mononuclear cells of severely immunocompromised HIV-infected patients.

The authors determined the natural killer (NK) and lymphokine-activated killer (LAK) activities of peripheral blood mononuclear cells (PBMCs) from a severely immunocompromised (CD4 cell counts < 100/mm3) group of AIDS patients, using K562 and U937 target cells. An increase in cytotoxicity was observed in the PBMCs of all 17 patients following a 48 h incubation with the combination of 400 U/ml of recombinant gamma interferon plus 20 U/ml of natural interleukin-2. Although NK and LAK activities were significantly higher in healthy controls than in patients, patients' LAK activity was higher than the NK activity of controls. The authors also demonstrated that the use of medium containing fetal bovine serum, when compared with medium containing autologous serum, increases NK activity without affecting LAK activity. Lymphokine augmentation of cytotoxicity is achievable in severely immunocompromised AIDS patients and might be of benefit in delaying opportunistic infections and malignancies.

Acquired Immunodeficiency Syndrome↗
PubMed1997

Predominance of detrimental humoral immune responses to HIV-1 in AIDS patients with CD4 lymphocyte counts less than 400/mm3.

The humoral immune response to human immunodeficiency virus type 1 (HIV-1) was studied in 25 AIDS patients with CD4 lymphocyte counts of less than 400/mm3. Humoral immune responses against tissue culture adapted strains of HIV-1, and two limited-passage patient isolates were investigated. Total anti-HIV antibody levels were not significantly different between different individuals. Neutralizing titres against HIVLA1 and HIVSF2 were 10- to 100-fold higher than against clinical isolates. The complement-mediated, antibody-dependent enhancement of HIV-1 infection titre was high (mean 1:14,000). Antibody-complement mediated cytotoxicity of both HIVLA1 and HIVSF2 was ineffective using human complement as a complement source. The antibody-dependent, cell-mediated cytotoxicity (ADCC) activity varied against the four isolates with tissue culture-adapted strains being more susceptible than clinical isolates. Finally, an ADCC effector cell function, natural killer or NK activity, was measured for all 25 patients, and NK activity of patients was decreased by nearly 75% compared to uninfected individuals. In summary, beneficial humoral immune responses are low in HIV-1 infected individuals with CD4 counts of less than 400/mm3 if the in vitro assay system is constructed to best mimic the in vivo situation. These results suggest that the lack of functional antibody responses to HIV may play an important role in viral pathogenesis.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Magnetic properties of tunicate blood cells. II. Ascidia ceratodes.

The magnetic properties of intact blood cells of the tunicate Ascidia ceratodes have been measured up to 50 kOe with a SQUID susceptometer. Analysis of total metal contents by plasma emission spectroscopy and V(IV) content by epr indicates that approximately 5% of the accumulated vanadium is +4 vanadyl ion. Measured values of the magnetic moment Mp at different values of the applied magnetic field H over the temperature range T = 2-100 K depend on the magnitude of the field indicating magnetic anisotropy of the ground state. The slope of the Mp vs. H/T curve at high temperature is significantly higher than expected from electron spin S = 1 per vanadium(III) ion. The model that fits these data best is a dimer with one V(III) S = 1 ion ferromagnetically coupled to a second V(III) S = 1 ion, with spin-coupling constant J = 3.5 cm-1, and 5% of the total vanadium content in the form of a V(IV) S = 1/2 ion. Since vanadium in A. ceratodes is known to reside in at least three different types of blood cell, the excellent fit indicates that the metal is stored predominantly as a dimer regardless of blood cell type. Ferromagnetic coupling implies that the two vanadium ions in the dimer are connected by an unprotonated mu-oxo bridge.

Animals↗
PubMed1996

Inhibitors of HIV-1 replication [corrected; erratum to be published] that inhibit HIV integrase.

HIV-1 replication depends on the viral enzyme integrase that mediates integration of a DNA copy of the virus into the host cell genome. This enzyme represents a novel target to which antiviral agents might be directed. Three compounds, 3,5-dicaffeoylquinic acid, 1-methoxyoxalyl-3,5-dicaffeoylquinic acid, and L-chicoric acid, inhibit HIV-1 integrase in biochemical assays at concentrations ranging from 0.06-0.66 microgram/ml; furthermore, these compounds inhibit HIV-1 replication in tissue culture at 1-4 microgram/ml. The toxic concentrations of these compounds are fully 100-fold greater than their antiviral concentrations. These compounds represent a potentially important new class of antiviral agents that may contribute to our understanding of the molecular mechanisms of viral integration. Thus, the dicaffeoylquinic acids are promising leads to new anti-HIV therapeutics and offer a significant advance in the search for new HIV enzyme targets as they are both specific for HIV-1 integrase and active against HIV-1 in tissue culture.

Antiviral Agents↗
PubMed1996

Drug leads from the Kallawaya herbalists of Bolivia. 1. Background, rationale, protocol and anti-HIV activity.

Aqueous, organic and alcoholic extracts of over 100 samples of 60 species of Kallawaya medicinal herbs representing 30 plant families were assayed to compare their toxicity and ability to protect MT-2 T-lymphoblastoid cells from the cytopathic effect of human immunodeficiency virus (HIV). The results are reported as a therapeutic index (TI) which was > 25 for eighteen species, including seven > 50 and one > 100. The anti-HIV activity resided primarily in the aqueous rather than in the organic extracts and was concentrated in plants used in ethnomedicine to treat lung and liver diseases.

Acquired Immunodeficiency Syndrome↗
PubMed1996

Interferon-gamma and interleukin-2 stimulate production of a soluble factor by L1210 and P815 tumor targets to promote macrophage activation.

Previously it was established that L1210 mouse leukemia and a variety of other tumor cell types produced a soluble factor(s), designated tumor-derived recognition factor (TDRF), which synergized with interferon-gamma (IFN-gamma) and interleukin-2 (IL-2) or lipopolysaccharide (LPS) to promote increased tumor necrosis factor-alpha (TNF-alpha) and nitric oxide synthase (NOS) mRNA synthesis by murine macrophages (M phi). Other work revealed that pretreatment of L1210 tumor targets with IFN-gamma rendered them more susceptible to NO-mediated killing by LPS-activated M phi. Now we have combined these observations to determine if pretreatment of L1210 or P815 tumor targets with IFN-gamma and/or IL-2 would augment production of TDRF to enhance M phi activation. Results confirmed that pretreatment of either L1210 or P815 targets with 200 u/ml of IFN-gamma or 1,000 u/ml of IL-2 significantly increased their susceptibility to M phi-mediated cytotoxicity owing to increased NO production. Similar pretreatment of L1210 targets with suboptimal concentrations of IFN-gamma and IL-2 in combination resulted in additive rather than synergistic augmentation of NO-mediated cytotoxicity by cytotoxic M phi. Pretreatment of L1210 targets with IFN-gamma or IL-2 alone or in combination increased the production of TDRF above constitutive levels as demonstrated by increased production of NO and induction of NOS mRNA expression by cytotoxic M phi. Thus IFN-gamma and/or IL-2 promoted increased TDRF production by tumor targets which in turn promoted M phi generation of tumor cytotoxic NO. It appears that M phi activating cytokines have a dual role in acting on certain tumor targets to augment the process of M phi activation through the increased elicitation of immunopotentiating tumor-derived soluble factor(s).

Animals↗
PubMed1996

Dicaffeoylquinic acid inhibitors of human immunodeficiency virus integrase: inhibition of the core catalytic domain of human immunodeficiency virus integrase.

Integration of a cDNA copy of the human immunodeficiency virus (HIV) genome is mediated by an HIV-1-encoded enzyme, integrase (IN), and is required for productive infection of CD4+ lymphocytes. It had been shown that 3,5-dicaffeoylquinic acid and two analogues were potent and selective inhibitors of HIV-1 IN in vitro. To determine whether the inhibition of IN by dicaffeoylquinic acids was limited to the 3,5 substitution, 3,4-, 4,5-, and 1,5-dicaffeoylquinic acids were tested for inhibition of HIV-1 replication in tissue culture and inhibition of HIV-1 IN in vitro. All of the dicaffeoylquinic acids were found to inhibit HIV-1 replication at concentrations ranging from 1 to 6 microM in T cell lines, whereas their toxic concentrations in the same cell lines were > 120 microM. In addition, the compounds inhibited HIV-1 IN in vitro at submicromolar concentrations. Molecular modeling of these ligands with the core catalytic domain of IN indicated an energetically favorable reaction, with the most potent inhibitors filling a groove within the predicted catalytic site of IN. The calculated change in internal free energy of the ligand/IN complex correlated with the ability of the compounds to inhibit HIV-1 IN in vitro. These results indicate that the dicaffeoylquinic acids as a class are potent and selective inhibitors of HIV-1 IN and form important lead compounds for HIV drug discovery.

Amino Acid Sequence↗
PubMed1995

Functional activities of 20 human immunodeficiency virus type 1 (HIV-1)-specific human monoclonal antibodies.

Antibodies that are useful in the treatment of HIV infection should result in virus neutralization or lysis of infected cells but should not enhance infection. In this study, the potential clinical use of 20 HIV-1-specific human monoclonal antibodies (HuMAbs) was determined by measuring their enhancing (C-ADE) activities using HIVLAI as the target virus. Two HuMAbs mediated both C-ADE and ADCC, two exclusively neutralized, and five exclusively mediated ADCC. Ten HuMAbs demonstrated no activity in any of the three assays. Three antibodies that neutralized HIVLAI were tested against HIVSF2; all three also neutralized HIVSF2. Four of five HuMAbs mediating ADCC against HIVLAI that were also tested against HIVSF2 had ADCC activity against HIVSF2. These results demonstrate that many HuMAbs have unique functions, allowing the separation of potentially beneficial and harmful activities. Combinations of HuMAbs with ADCC and neutralizing functions may have therapeutic utility.

Antibodies, Monoclonal↗
PubMed1995

Antibodies to the putative SIV infection-enhancing domain diminish beneficial effects of an SIV gp160 vaccine in rhesus macaques.

OBJECTIVE: To demonstrate that antibodies against amino acids (aa) 603-622 of the SIV gp41 transmembrane glycoprotein enhance infection of SIV in vivo. DESIGN: A synthetic peptide derived from aa 603-622 of SIVmac251 gp41 was synthesized and tested for immunogenicity in rabbits and SIV-infected rhesus macaques. Next, SIV-naive animals were immunized with either a recombinant vaccinia virus expressing the SIV gp160 envelope glycoprotein (VVrgp160) and boosted three times with aa 603-622 (group 1, four animals), wild-type vaccinia virus and boosted with aa 603-622 (group 2, two animals), or VVrgp160 followed by three doses of an irrelevant peptide (group 3, two animals). Animals were challenged with SIVmac251. RESULTS: Peptide aa 603-622 was immunogenic in rabbits. SIV-infected rhesus monkeys immunized with the peptide developed two-three log increases in antibodies to this peptide and antibodies that could enhance SIV infection in vitro. SIV-naive rhesus macaques in group 1 had higher levels of antibody to the peptide by enzyme-linked immunosorbent assay and higher levels of enhancing antibodies at the time of SIV challenge than the animals in groups 2 or 3. Following challenge with SIVmac251 the group 1 animals had detectable p27 antigen longer than animals in group 2 and 3 and died of simian AIDS before the respective animals in the two control groups (P < 0.05 by log-rank test). CONCLUSIONS: aa 603-622 of SIV gp41, like aa 579-613 of HIV gp41, can stimulate production of antibodies that enhance SIV and HIV infection in vitro. Furthermore, immunization with this peptide suppressed beneficial effects of a gp160 vaccine and appeared to enhance SIV infection in vivo.

Animals↗
PubMed1993

Gut contents: a significant contaminant of Mytilus edulis whole body metal concentrations.

Ingested matter can have a significant effect on whole body metal concentration measurements in Mytilus edulis. Depuration of mussels in clean seawater for 36 h prior to dissection eliminates most of these contaminating gut contents. Depuration followed by metal analyses is the most direct method of determining mussel tissue metal bioburdens. After being transplanted into a plume of primary treated sewage effluent in Salem Harbor, Massachusetts for 32 days, Al, Cr, and Fe concentrations in depurated mussels were significantly lower than those determined for either non-depurated mussels or for depurated mussels to which fecal concentrations of Al, Cr, and Fe were added back in. Although mathematical methods developed by both Ouellette (1978) and Boehm et al. (1988) could be applied to non-depurated mussels in order to correct for errors associated with gut metal contamination, these indirect methods were not as reliable as depuration prior to analysis.

Animals↗
PubMed1992

In vivo incorporation of 14C-phenylalanine into ascidian tunichrome.

Ascidia ceratodes exposed to 14C-phenylalanine in the surrounding seawater incorporates the radiolabel into newly biosynthesized tunichrome molecules. Radioactivity can be detected in tunichrome extracted from circulating blood cells within one day following initial exposure to the radiolabel; weak activity (less than or equal to 4 microCi/mol tunichrome = 22 nmol phenylalanine/mol tunichrome) is detected in 1 to 10 days; significantly higher amounts of radiolabel (57 microCi/mol tunichrome = 318 nmol phenylalanine/mol tunichrome) appear 20 days after seawater exposure. Therefore, phenylalanine can function as a precursor in the biosynthesis of tunichrome.

Animals↗
PubMed1992

Generation and characterization of a human monoclonal antibody that neutralizes diverse HIV-1 isolates in vitro.

OBJECTIVE: The purpose of this study was to develop and characterize human monoclonal antibodies (HuMAb) that neutralize HIV-1. DESIGN: Based upon previous studies involving the generation of HuMAb that neutralize other enveloped viruses, we thought it feasible to generate HuMAb that might neutralize HIV-1. METHODS: A HuMAb was generated by fusing splenic B-cells from an HIV-positive patient with a mouse myeloma cell line. Flow cytometry was used to determine surface reactivity of the HuMAb on HIV-infected and non-infected cells. Radioimmunoprecipitation was employed to elucidate the antigen recognized by the HuMAb. A cell survival assay was used to determine the ability of the HuMAb to neutralize divergent isolates of HIV-1 in the presence or absence of complement. A gp120-CD4 inhibition enzyme-linked immunosorbent assay (ELISA) was developed in order to initiate studies to determine the mechanism of neutralization by the HuMAb. RESULTS: An anti-HIV HuMAb was generated that neutralized two HIV-1 isolates (IIIB and MN) without complement and which neutralized one divergent isolate (RF) and one clinical isolate in the presence of complement. This HuMAb, designated S1-1, was found, by flow cytometric analysis, to react with the surface of HIV-1-infected but not with uninfected cells. Radioimmunoprecipitation analysis demonstrated that S1-1 binds to native HIV gp120, but not dithiothreitol (DTT)-treated gp120. In addition, HuMAb S1-1 did not bind to denatured HIV antigens in Western blot analysis. HuMAb S1-1 effectively inhibited the binding of gp120 to soluble CD4 in ELISA. CONCLUSIONS: These results suggest that the epitope recognized by S1-1 is conformational and conserved among diverse HIV-1 isolates and may represent an uncharacterized HIV neutralizing domain within or close to the CD4 binding domain on gp120. HuMAb S1-1 might have a role to play in vaccine development or passive immunotherapy.

Antibodies, Monoclonal↗
PubMed1991

Two immunodominant domains of gp41 bind antibodies which enhance human immunodeficiency virus type 1 infection in vitro.

Four of eight human monoclonal antibodies (huMAbs) to gp41 were identified which could enhance human immunodeficiency virus type 1 (HIV-1) infection in vitro by complement-mediated antibody-dependent enhancement (C'-ADE). These enhancing huMAbs were mapped to two distinct domains on the HIV-1 gp41 transmembrane glycoprotein by using synthetic peptides. The first domain, amino acids 579 to 613 (peptide AA579-613), was recognized by three of the four enhancing huMAbs. The AA579-613 peptide blocked C'-ADE of HIV-1 infection in vitro whether it was mediated by these three huMAbs or by human polyclonal anti-HIV serum. The second domain, amino acids 644 to 663, bound the remaining enhancing huMAb. This peptide weakly blocked C'-ADE mediated by the huMAb and by an HIV immune globulin fraction but did not block C'-ADE mediated by a patient's serum. The patient's serum did react with the peptide in an enzyme immunoassay. The huMAbs to the two domains could interact in vitro to enhance HIV-1 infection in a synergistic manner. These two domains, which bind enhancing antibodies, are conserved between HIV-1 isolates as well as between HIV-2 and simian immunodeficiency virus isolates. These data demonstrate the existence of two conserved regions within the HIV-1 gp41 which bind enhancing antibodies; these two domains, amino acids 579 to 613 and 644 to 663, may prove important in HIV-1 vaccine development and in immunopathogenesis of HIV-1 infection.

Amino Acid Sequence↗
PubMed1990

Complement-mediated antibody-dependent enhancement of HIV-1 infection requires CD4 and complement receptors.

In this study it is demonstrated that complement-mediated antibody-dependent enhancement (C'-ADE) of HIV-1 infection in vitro is blocked by murine monoclonal antibodies to CD4 and complement receptor type 2 (CR2) while HIV-1 infection in the absence of C'-ADE is blocked by anti-CD4 but not anti-CR2 monoclonal antibodies. The anti-CR2 murine monoclonal antibody, OKB7, blocked C'-ADE of HIV-1 infection at concentrations greater than 1 microgram/ml. The anti-CD4 monoclonal antibody, OKT4a, but not OKT4f blocked C'-ADE at concentrations greater than 0.06 microgram/ml. HIV-1 infections were quantitated by cytopathic effect, indirect immunofluorescence, and reverse transcriptase release. It appears from these in vitro studies that C'-ADE of HIV-1 infection requires both CD4 and complement receptors while HIV-1 infection in the absence of antibody and complement requires only CD4.

Antibodies, Monoclonal↗