Kinetics of fusion of enveloped viruses with cells.
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Animals↗
Biomedical subjects
A Puri
Publications and source records attributed to A Puri.
Immunostimulant agents from Andrographis paniculata.
EtOH extract and purified diterpene andrographolides of Andrographis paniculata (Acanthaceae) induced significant stimulation of antibody and delayed type hypersensitivity (DTH) response to sheep red blood cells (SRBC) in mice. The plant preparations also stimulated nonspecific immune response of the animals measured in terms of macrophage migration index (MMI) phagocytosis of 14C-leucine labelled Escherichia coli and proliferation of splenic lymphocytes. The stimulation of both antigen specific and nonspecific immune response was, however, of lower order with andrographolide than with the EtOH extract, suggesting thereby that substance(s) other than andrographolide present in the extract may also be contributing towards immunostimulation.
Adjuvants, Immunologic↗
Hemagglutinin-neuraminidase enhances F protein-mediated membrane fusion of reconstituted Sendai virus envelopes with cells.
Reconstituted Sendai virus envelopes containing both the fusion (F) protein and the hemagglutinin-neuraminidase (HN) (F,HN-virosomes) or only the F protein (F-virosomes) were prepared by solubilization of the intact virus with Triton X-100 followed by its removal by using SM2 Bio-Beads. Viral envelopes containing HN whose disulfide bonds were irreversibly reduced (HNred) were also prepared by treating the envelopes with dithiothreitol followed by dialysis (F,HNred-virosomes). Both F-virosomes and F,HNred-virosomes induced hemolysis of erythrocytes in the presence of wheat germ agglutinin, but the rates and extents were markedly lower than those for hemolysis induced by F,HN-virosomes. Using an assay based on the relief of self-quenching of a lipid probe incorporated in the Sendai virus envelopes, we demonstrate the fusion of both F,HN-virosomes and F-virosomes with cultured HepG2 cells containing the asialoglycoprotein receptor, which binds to a terminal galactose moiety of F. By desialylating the HepG2 cells, the entry mediated by HN-terminal sialic acid receptor interactions was bypassed. We show that both F-virosomes and F,HN-virosomes fuse with desialylated HepG2 cells, although the rate was two- to threefold higher if HN was included in the viral envelope. We also observed enhancement of fusion rates when both F and HN envelope proteins were attached to their specific receptors.
Animals↗
Immunostimulant activity of a novel lipopeptide and its protective action against Leishmania donovani.
Novel lipopeptides 84/201 and 86/450 synthesized in this laboratory stimulated antibody and delayed type hypersensitivity (DTH) response to ovalbumin in guinea pigs. Lipopeptide 86/450 also stimulated antibody and DTH responses in albino mice and enhanced nonspecifically macrophage migration index (MMI), phagocytic activity and incorporation of [14C] glucosamine in peritoneal macrophages of the treated animals. Proliferative response of splenocytes from lipopeptide 86/450 treated animals was significantly higher than that from untreated controls. Peritoneal macrophages from lipopeptide 86/450 treated mice were less susceptible to Leishmania donovani promastigote invasion when co-cultured in vitro. The treated animals on challenge with L. donovani promastigote/amastigote showed 80 to 90% lower intake of infection than the control animals.
Adjuvants, Immunologic↗
Role of viral envelope sialic acid in membrane fusion mediated by the vesicular stomatitis virus envelope glycoprotein.
Fusion of vesicular stomatitis virus (VSV) with cells and liposomes before and after treatment with neuraminidase was studied using the R18 dequenching assay. Desialylation of VSV significantly enhanced the extent of fusion with Vero cells but affected neither the pH dependence nor the binding of VSV to Vero cells. The enhanced fusion of asialo-VSV was observed both at the plasma membrane as well as via the endocytic pathway. Both VSV and asialo-VSV fused with liposomes made of neutral phospholipid, but only asialo-VSV fused with liposomes containing a 1:1 mixture of neutral and negatively charged phospholipid. To examine factors which contribute to the extent of fusion, we analyzed the various activation and inactivation reactions that take place as a result of low-pH triggering of VSV prebound to the target membrane. Lag times for the onset of fusion were similar for VSV and asialo-VSV, indicating that desialylation did not affect the activation reactions. However, exposure of VSV bound to target membranes at pH 6.5 for 400 s led to considerable inactivation, whereas little inactivation was seen after desialylation of VSV. These results are analyzed in terms of a model which allows us to determine which components of the overall fusion process are dominated by viral envelope sialic acid.
Animals↗
Dextran sulfate inhibits fusion of influenza virus and cells expressing influenza hemagglutinin with red blood cells.
The influence of dextran sulfate with molecular weights of 500,000 and 8000 on binding and fusion of influenza virus (X31 strain) and of cells expressing influenza hemagglutinin (GP4F) with red blood cells (RBC) was investigated by spectrofluorimetry using virus and RBC labeled with the fluorescent dye octadecyl rhodamine B (R18). There was no significant inhibition of binding of virus and GP4F cells to red blood cells by dextran sulfate, but the polymer strongly inhibited the low pH induced fusion. Virus-RBC fusion was completely blocked by the high molecular weight dextran sulfate at concentrations as low as 0.5 mg/ml. Inhibition of RBC-GP4F cell fusion by dextran sulfate in the same concentration range was not as pronounced but the effect was potentiated by Ca2+. The polymer was only inhibitory when added at early steps of the fusion reaction, but the pH-induced conformational change of the hemagglutinin was not affected by dextran sulfate as measured by its susceptibility to proteolytic digestion. Removal of dextran sulfate after low pH-requiring steps allowed the system to fuse at neutral pH indicating that the inhibitory effect requires the continuous presence of dextran sulfate during the fusion reaction.
3T3 Cells↗
Immunostimulant Activity of Picroliv, the Iridoid Glycoside Fraction of Picrorhiza kurroa, and its Protective Action against Leishmania donovani Infection in Hamsters1.
Picroliv, a standardised fraction from root and rhizome of PICRORHIZA KURROA, consisting of iridoid glycosides and shown to be responsible for its hepatoprotective activity, was studied for immunostimulant activity. Oral administration of Picroliv (10 mg/kg x 7 days) in mice prior to immunization with sheep red blood cells (SRBC) resulted in a significant increase in haemagglutinating antibody (HA) titre, plaque forming cells (PFC), and delayed hypersensitivity (DTH) response to SRBC. Picroliv enhanced the non-specific immune response characterized by an increase in macrophage migration index (MMI), [ (14)C]-glucosamine uptake, phagocytosis of [ (14)C]-leucine labelled ESCHERICHIA COLI, chemiluminescence of peritoneal macrophages, and higher uptake of [ (3)H]-thymidine in the lymphocytes of treated mice. It also induced a high degree of protection in golden hamsters against challenge infection with LEISHMANIA DONOVANI promastigotes.
Journal Article↗
Drug-induced liver injury.
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Antitubercular Agents↗
An indirect fluorescent antibody (IFA) test for the serodiagnosis of Kala-Azar.
The IFA test developed using Leishmania donovani promastigote and amastigote antigens showed very high antibody titre in clinically and parasitologically established cases (30) of kala-azar, the geometrical mean reciprocal titre (GMRT) being 870 +/- 5.4 and 5370 +/- 1.80 respectively with the two antigens. In contrast, the GMRT of normal subjects of endemic area was only 12.44 +/- 6.19 and 80.35 +/- 1.66 respectively with these antigens. None of the subjects from non-endemic area suffering with other parasitic diseases, such as malaria, filaria, amoebiasis, leprosy or tuberculosis (20 cases each) gave a positive response to any of the antigen. The test holds promise in the diagnosis of Kala-azar.
Animals↗
Immunostimulant activity of Picroliv, the iridoid glycoside fraction of Picrorhiza kurroa, and its protective action against Leishmania donovani infection in hamsters.
Picroliv, a standardised fraction from root and rhizome of Picrorhiza kurroa, consisting of iridoid glycosides and shown to be responsible for its hepatoprotective activity, was studied for immunostimulant activity. Oral administration of Picroliv (10 mg/kg x 7 days) in mice prior to immunization with sheep red blood cells (SRBC) resulted in a significant increase in haemagglutinating antibody (HA) titre, plaque forming cells (PFC), and delayed hypersensitivity (DTH) response to SRBC. Picroliv enhanced the non-specific immune response characterized by an increase in macrophage migration index (MMI), [14C]-glucosamine uptake, phagocytosis of [14C]-leucine labelled Escherichia coli, chemiluminescence of peritoneal macrophages, and higher uptake of [3H]-thymidine in the lymphocytes of treated mice. It also induced a high degree of protection in golden hamsters against challenge infection with Leishmania donovani promastigotes.
Adjuvants, Immunologic↗
Interactions of CD4+ plasma membrane vesicles with HIV-1 and HIV-1 envelope glycoprotein-expressing cells.
To study interactions between the human immunodeficiency virus type 1 (HIV-1) envelope glycoprotein (gp120-gp41) and the receptor in the target membrane, CD4, a new experimental system utilizing CD4-carrying plasma membrane vesicles (CD4 PMVs) was developed. CD4 PMVs were prepared by hypotonic lysis of HeLa cells expressing CD4 after infection with recombinant vaccinia virus containing the CD4 cDNA. The CD4 PMVs carried up to 680 CD4 molecules per vesicle. Their fusion with cells expressing gp120-gp41 after infection with recombinant vaccinia virus was monitored by fluorescence video microscopy by using lipophilic fluorescent dyes. Fluorescence changes as a result of fusion occurred within 30 min at 37 degrees C, and little fluorescence changes were seen with cells expressing the noncleaved HIV-1 envelope glycoprotein (gp160). The preincubation of CD4 PMVs with HIV-1 reduced its infectivity 10-fold. The CD4 PMVs were more effective in inhibiting syncytia formation than sCD4. These results demonstrate that CD4 PMVs could be used to study the mechanisms of HIV-1 envelope-mediated fusion and have the potential to inactivate HIV-1.
Animals↗
Single cell fusion events induced by influenza hemagglutinin: studies with rapid-flow, quantitative fluorescence microscopy.
Fusion of individual human erythrocytes to fibroblasts expressing the influenza virus hemagglutinin Cells were attached to coverslips fitted in a specially designed flow chamber mounted on a microscope stage, and fusion was triggered by rapid acidification to pH less than 5.2. Fusion between single cell pairs was monitored by a fluorescence increase due to redistribution of fluorescent dyes between either membrane or cytoplasmic compartments of fusing cells. The single cell fusion events were broadly heterogenous in lag times, rise times, and overall shape of the curves. Lag times obtained with a water-soluble dye were within the range obtained with a water-soluble dye were within the range obtained with the membrane-bound fluorophores, (10-160 s). Fusion was both all-or-nothing and irreversible, in that once dye redistribution in any cell commenced, it completed, regardless of pH. Short pulses of pH 4.9 for 6-10 s led to about half of the cell pairs fusing, but pulses greater than 14 s were as effective as constant low pH. Pulses that were too short to trigger fusion did not partially activate nor deactivate the fusion process, as shown by the ability of a second acidification to cause fusion of the same cells, with similar lag times. These results indicate that the overall hemagglutinin-mediated fusion process is composed of at least two stages, one required for commitment of the hemagglutinin to a fusogenic state that is pH-dependent and a maturation stage that is pH-independent.
Animals↗
Multicenter controlled trial comparing high-frequency jet ventilation and conventional mechanical ventilation in newborn infants with pulmonary interstitial emphysema.
One hundred forty-four newborn infants with pulmonary interstitial emphysema were stratified by weight and severity of illness, and randomly assigned to receive treatment with high-frequency jet ventilation (HFJV) or rapid-rate conventional mechanical ventilation (CV) with short inspiratory time. If criteria for treatment failure were met, crossover to the alternate ventilatory mode was permitted. Overall, 45 (61%) of 74 infants met treatment success criteria with HFJV compared with 26 (37%) of 70 treated with CV (p less than 0.01). Eighty-four percent of patients who crossed over from CV to HFJV initially responded to the new treatment, and 45% ultimately met success criteria on HFJV. In contrast, only 9% of those who crossed over from HFJV to CV responded well to CV (p less than 0.01), and the same 9% ultimately met success criteria (p less than 0.05). Therapy with HFJV resulted in improved ventilation at lower peak and mean airway pressures, as well as more rapid radiographic improvement of pulmonary interstitial emphysema, in comparison with rapid-rate CV. Survival by original assignment was identical. When survival resulting from rescue by the alternate therapy in crossover patients was excluded, the survival rate was 64.9% for HFJV, compared with 47.1% for CV (p less than 0.05). The incidence of chronic lung disease, intraventricular hemorrhage, patent ductus arteriosus, airway obstruction, and new air leak was similar in both groups. We conclude that HFJV, as used in this study, is safe and is more effective than rapid-rate CV in the treatment of newborn infants with pulmonary interstitial emphysema.
Bronchopulmonary Dysplasia↗
A dissection of steps leading to viral envelope protein-mediated membrane fusion.
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Hemagglutinin Glycoproteins, Influenza Virus↗
Adjuvant activity of some nonpyrogenic hydrophobic analogues of muramyl dipeptide in enhancing the primary humoral and cell mediated immune responses in guinea pig model.
Five muramyl dipeptide analogues synthesized by derivatization of gamma-carboxyl of D-isoglutamine residue of MDP into alkyl amides or incorporation of lysine residue at the site via epsilon-NH2 function were evaluated for immuno-adjuvant activity. Derivatization of gamma-carboxyl of D-isoglutamine into butyl, octyl and dibutyl residues stimulated delayed type of hypersensitivity (DTH) response, the maximum stimulation being observed with octyl amide. Introduction of lauryl amide residue abolished DTH response. The antibody response was impaired with all the alkyl amide analogues except for the lysyl amide derivative with which the response was higher than MDP. Correlation was observed between DTH response and macrophage migration.
Acetylmuramyl-Alanyl-Isoglutamine↗
Effect of erythrocyte transbilayer phospholipid distribution on fusion with vesicular stomatitis virus.
To identify the specific component(s) in the target membrane involved in fusion of vesicular stomatitis virus (VSV), we examined the interaction of the virus with human erythrocyte membranes with asymmetric and symmetric bilayer distributions of phospholipids. Fusion was monitored spectrofluorometrically by the octadecylrhodamine dequenching assay. Fusion of VSV with lipid-symmetric erythrocyte ghosts was rapid at 37 degrees C and low pH, whereas little or no fusion was observed with lipid-asymmetric ghosts. Conversion of phosphatidylserine in the lipid-symmetric ghost membrane to phosphatidylethanolamine by means of the enzyme phosphatidylserine decarboxylase did not alter the target membrane's susceptibility to VSV fusion. Spin-labeled phospholipid analogues with phosphatidylserine, phosphatidylethanolamine, and phosphatidylcholine headgroups incorporated into the outer leaflet of lipid-asymmetric erythrocytes did not render those membranes fusogenic. Electron spin resonance spectra showed an increased mobility of a phosphatidylcholine spin-label incorporated into the outer leaflet of lipid-symmetric erythrocyte ghosts as compared to that of lipid-asymmetric ghosts. These results indicate that the susceptibility to VSV fusion is not dependent on any particular phospholipid but rather is related to packing characteristics of the target membrane.
Electron Spin Resonance Spectroscopy↗
Conformational changes and fusion activity of influenza virus hemagglutinin of the H2 and H3 subtypes: effects of acid pretreatment.
Marked differences were observed between the H2 and H3 strains of influenza virus in their sensitivity to pretreatment at low pH. Whereas viral fusion and hemolysis mediated by influenza virus X:31 (H3 subtype) were inactivated by pretreatment of the virus at low pH, influenza virus A/Japan/305/57 (H2 subtype) retained those activities even after a 15-min incubation at pH 5.0 and 37 degrees C. Fusion with erythrocytes was measured by using the octadecylrhodamine-dequenching assay with both intact virions and CV-1 monkey kidney cells expressing hemagglutinin (HA) on the plasma membrane. To study the nature of the differences between the two strains, we examined the effects of low-pH treatment on the conformational change of HA by its susceptibility to protease digestion, exposure of the fusion peptide, and electron microscopy of unstained, frozen, hydrated virus. We found that the respective HA molecules from the two strains assumed different conformational states after exposure to low pH. The relationship between the conformation of HA and its fusogenic activity is discussed in the context of these experiments.
Erythrocytes↗
Adaptogenic activity of Indian Panax pseudoginseng.
The crude extract and saponins of Indian pseudoginseng and saponins of Korean ginseng have been studied using a battery of biological tests in rats and mice. Indian pseudoginseng saponins were found to exhibit better activity than the Korean ginseng saponins in several tests employed. The results indicate a need for in-depth study of Indian pseudoginseng as an adaptogenic agent, after cultivation of the plant under controlled conditions.
Animals↗