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Biomedical subjects

G L Jones

Publications and source records attributed to G L Jones.

At least 55 records · Page 3Linked to original sources
PubMed1992

Protective immunization with invariant peptides of the Plasmodium falciparum antigen MSA2.

Three octapeptides from the N and C terminal C regions of the merozoite surface Ag 2 (MSA2) of Plasmodium falciparum elicit anti-MSA2 antibody when given as diphtheria toxoid conjugates. These antibodies also bind to the MSA2 homolog from the rodent malaria Plasmodium berghei. All mice vaccinated with these conjugates and challenged with an otherwise lethal inoculum of P. berghei showed substantial protection with most surviving. There was a inverse correlation between the development of the parasitemia and the antibody titer, with alum, algammulin, and CFA giving comparable results. These observations show that the conserved region of MSA2 could form the basis of a malaria vaccine when presented in a suitably immunogenic form, thus avoiding the problems of antigenic diversity [corrected].

Adjuvants, Immunologic↗
PubMed1992

Parasite-induced changes to localized erythrocyte membrane deformability in Plasmodium falciparum cultures.

The effect of intra-erythrocyte development of the Plasmodium falciparum parasite on local deformability of human erythrocyte membranes was studied by aspiration of cells into 0.56 micron diameter pores in polycarbonate filters and examination, after fixing, with a scanning electron microscope. As the aspiration pressure increased, the erythrocyte membrane was extruded into the filter pores. The pressure dependence of the protrusion length and the minimum pressure required to produce any deformation provided measures of the membrane shear and the bending moduli, respectively. At the trophozoite and, to a greater extent, schizont stage of development, host cell membrane deformability was significantly decreased. There was no appreciable difference between uninfected and ring-infected erythrocytes.

Animals↗
PubMed1992

Effect of an inhaled thromboxane mimetic (U46619) on in vivo pulmonary resistance and airway hyperresponsiveness in dogs.

1. We investigated the role of thromboxane A2 in the airway hyperresponsiveness that follows the inhalation of ozone in dogs by examining the responses to an inhaled thromboxane analogue (U46619). 2. Measurements of pulmonary resistance were made in anaesthetized dogs; the concentration of inhaled agonist causing an increase of 5 cmH2O l-1 s was calculated (provocative concentration). The effect of inhaled U46619 was studied on in vivo canine airway resistance, on airway responsiveness and on airways made hyperresponsive following the inhalation of ozone. 3. Inhaled thromboxane is a potent constrictor of the canine airway. The mean provocative concentration was 2.13 x 10(-4) M, compared to acetylcholine which was 3.23 x 10(-2) M. 4. Inhaled thromboxane did not result in the development of airway hyperresponsiveness to acetylcholine. Following U46619 inhalation the mean provocative concentration to acetylcholine was 3.92 x 10(-2) M. 5. Canine airway was not hyperresponsive to inhaled thromboxane following the inhalation of ozone. This was not due to an inhibition of acetylcholinesterase as the dogs were hyperresponsive to carbachol (a muscarinic agonist not degraded by endplate cholinesterase). 6. These experiments do not support a role for thromboxane in the development of airway hyperresponsiveness following the inhalation of ozone in dogs.

15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5↗
PubMed1992

Effect of an inhaled thromboxane mimetic (U46619) on airway function in human subjects.

Thromboxane A2(TxA2) has been implicated in the pathogenesis of airway hyperresponsiveness. The effects of inhaled TxA2 on human airway function have not been studied because of its short half-life. U46619 is a chemical that mimics the effects of TxA2. The purpose of this study was to evaluate the effects of inhaled U46619 on human airway function and methacholine airway responsiveness. Airway responsiveness to methacholine and U46619 was measured in 19 subjects (13 asthmatic and six normal) and expressed as the provocative concentration causing a 20% fall in FEV1 (PC20). On one day, methacholine alone was inhaled. On a second day, U46619 was inhaled, then 1 h later methacholine was inhaled. On a third day, U46619 was inhaled, then repeated 1 h later. In six subjects, the effects of isotonic saline or a subthreshold concentration of histamine or U46619 were examined on methacholine airway responsiveness. U46619 was 178 times more potent as a bronchoconstrictor than was methacholine. Airway responsiveness to methacholine was correlated to airway responsiveness to U46619 (r = 0.87, p = 0.001). Subthreshold concentrations of U46619, but not of histamine, increased methacholine airway responsiveness. The mean maximal fall in FEV1 after inhaled methacholine was 13.2% (SEM, 3.4%) after saline, 12.4% (SEM, 2.4%) after histamine, and 25.7% (SEM, 2.0%) after U46619 (p = 0.0004). This effect lasted less than 1 h. There was no tachyphylaxis to repeated inhalations of U46619. These results indicate that in human subjects inhaled U46619 is a potent bronchoconstrictor that, when present in the airways, can cause airway hyperresponsiveness to inhaled methacholine in asthmatic subjects.

Aerosols↗
PubMed1991

A Plasmodium falciparum exo-antigen alters erythrocyte membrane deformability.

Here we describe a reduced membrane deformability of human erythrocytes when aspirated into 0.6 microns diameter in polycarbonate sieves, after exposure of uninfected cells to spent parasite-culture supernatant. This, taken in concert with a previous observation that intra-erythrocytic development of the parasite P. falciparum decreases host localised membrane deformability, may indicate a biological role for such parasite-induced changes in the rheological properties of the erythrocyte.

Animals↗
PubMed1991

Plasmodium falciparum polypeptides interacting with human red cell membranes show high affinity binding to Band-3.

P. falciparum proteins were labelled with [35S]methionine and harvested at various asexual stages. A number of parasite proteins bound to uninfected red cell membranes (ghosts). Some of these proteins differentially partitioned when ghosts were extracted with detergent. Several of these proteins bound very strongly to immobilised whole ghost proteins or immobilised purified Band-3 in a stage-specific manner, but not to a sham-coupled matrix or to immobilised Band-3 extract from cells rendered refractory to invasion. Such specific binding of parasite proteins to immobilised Band-3 supports recent conjecture as to its role as a host receptor during parasite invasion. However, our results demonstrate the complex and multifactorial nature of the interaction between parasite and host proteins during invasion and development.

Animals↗
PubMed1991

Decreased rotational diffusion of band 3 in Melanesian ovalocytes from Papua, New Guinea.

Melanesian ovalcytes from Papua New Guinea have an N-terminal extension of the band 3 polypeptide (Jones, G.L., Edmunson, H.M., Wesche, D., Saul, A. 1990. Biochim. Biophys. Acta 1096:33-40). The ovalocytes showed a threefold increase in shear elastic modulus as determined by micropipette aspiration measurements of membrane rigidity. Time-resolved phosphorescence anisotropy has been used to study the rotational freedom of band 3 in membranes prepared from ovalocytes. The ovalocytic polymorphism was found to be associated with a marked decrease in the rotational mobility of band 3. This may indicate participation of band 3 in large homoaggregates or in complexes with other proteins at the cytoplasmic surface. There was no morphological clustering of band 3 detectable by immunofluorescence microscopy.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1991

Ethanol euthanasia and its effect on the binding of antibody generated against an immunogenic peptide construct.

Mice were immunised with an immunogenic peptide construct CKNNNSTNSGI coupled to diphtheria toxoid as a carrier. This peptide sequence contains the epitope STNS which is the target of inhibitory monoclonal antibodies directed against the second merozoite surface antigen of Plasmodium falciparum. Antisera raised against the peptide construct were taken using an injection of 70 per cent ethanol or sodium pentobarbitone as methods of euthanasia and these methods compared by determining their effects on the binding specificity of the antibody to the antigen using the immunological criteria of immunofluorescence, immunoblotting criteria of immunofluorescence, immunoblotting and ELISA assays. There was no significant decrease in antibody binding with either sodium pentobarbitone, or ethanol with a final concentration of less than 30 per cent in mouse antisera. Antisera with an added ethanol concentration of 40 to 60 per cent relaxed antibody conformation and this raises the possibility of using the differential effects of ethanol as a tool in mapping antigenic fine structure of a range of antibodies directed against defined epitopes. The cross-reactive response of non-specific antibodies in polyclonal antisera was lowered at the suggested dosage for ethanol euthanasia. Ethanol has immense potential as an alternative method of euthanasia when barbiturate drugs, such as sodium pentobarbitone, are unavailable in specific experimental protocols. This may especially aid research workers in developing countries involved in vaccine development, antibody production and subsequent serological analysis.

Amino Acid Sequence↗
PubMed1991

Comparative immunogenicity of free and carrier-conjugated peptides derived from the constant regions of a polymorphic malarial surface antigen.

One peptide (L7) representing the entire constant N-terminal region, and two peptides (L5 and L6) representing the entire C-terminal constant region of the variable merozoite surface antigen MSA2, were synthesised by solid-state (tBOC) chemistry. Mice were immunised with the peptides alone and conjoined to the carrier protein diphtheria toxoid (DT) using the hetero-bifunctional reagent maleimidocaproyloxysuccinimide (MCS). Immune response was evaluated against the peptide itself by ELISA and against the intact protein MSA2 by immunoblotting and immunofluorescence assay (IFA). Whereas all peptides elicited a strong specific antipeptide response when administered as conjugates only L7 and L6 elicited an anti-peptide response in the absence of carrier. L5 and L7 conjugates elicited sera reactive with the intact MSA2, whereas only L7 elicited such specificity in the absence of carrier.

Amino Acid Sequence↗
PubMed1991

Immunological fine structure of the variable and constant regions of a polymorphic malarial surface antigen from Plasmodium falciparum.

The 51-kDa merozoite surface antigen MSA2 of Plasmodium falciparum shows considerable strain-dependent polymorphism. Although marked sequence variation occurs in the central region of the molecule, the N and C-terminal sequences are highly conserved. A number of monoclonal antibodies directed against MSA2 have been described which inhibit parasite growth in vitro, but these are all directed against variable regions. In an attempt to raise strain independent antibodies we have prepared peptide-diphtheria toxoid (DT) constructs from 36 N-terminal octapeptides spanning the constant region and extending into the variable region of the FCQ/27 PNG variant staggered by one amino acid at either end. Similarly, we prepared 26 C-terminal octapeptides spanning the C-terminal constant region as well as 10 octapeptides from the variable region of the Indochina I variant MSA2. Most of the peptides elicited antipeptide titres in excess of 1/10(4) when administered to mice as peptide-DT adducts emulsified with Freund's complete adjuvant. Only 3 of the 43 N- and C-terminal constant region peptides elicited antibodies which reacted appropriately on immunofluorescence (IFA) or immunoblotting analysis with the intact MSA2 of both strains studied (FCQ/27 and Indochina I), whereas 3 other peptides from the variable region elicited antibodies reactive with the parent MSA2 only. Peptide constructs eliciting antibodies recognising the intact protein corresponded to elements in the cognate sequence of high antigenicity as predicted by the Jameson and Wolf algorithm.

Amino Acid Sequence↗
PubMed1991

The effect of antioxidants on ozone-induced airway hyperresponsiveness in dogs.

The role of oxygen radicals in causing ozone-induced airway hyperresponsiveness in dogs was examined by pretreating dogs with allopurinol and/or deferoxamine mesylate (desferal), which are inhibitors of oxygen radical generation, before ozone inhalation. Acetylcholine airway responsiveness was measured before and after either air or ozone inhalation (3 ppm for 20 min) on 5 experimental days separated by at least 2 wk. On each day, the dogs were pretreated intravenously with allopurinol (50 mg/kg) followed by inhaled desferal (1,000 mg inhalation) or with allopurinol followed by the diluent for desferal or with the diluent for allopurinol and desferal or with both diluents. The effect of ozone on acetylcholine airway responsiveness was expressed as the differences in the log-transformed preozone-postozone acetylcholine provocative concentrations. When dogs received both diluents or either treatment alone, ozone inhalation caused airway hyperresponsiveness. The mean log differences for the preozone-postozone acetylcholine provocative concentration were 0.804 (SEM, 0.17) for both diluents, 0.524 (SEM, 0.16) for allopurinol alone, and 0.407 (SEM, 0.22) for desferal alone. However, the combination of allopurinol and desferal significantly inhibited the development of ozone-induced airway hyperresponsiveness, the log difference being 0.195 (SEM, 0.11) (p less than 0.05), without inhibiting ozone-induced neutrophil influx into the airways. The results suggest that the production of oxygen radicals is important in the pathogenesis of ozone-induced airway hyperresponsiveness.

Acetylcholine↗
PubMed1990

Human erythrocyte Band-3 has an altered N terminus in malaria-resistant Melanesian ovalocytosis.

There is a high prevalence of the erythrocyte polymorphism ovalocytosis associated with reduced susceptibility to malaria in Papua New Guinea. The major erythrocyte integral membrane protein, Band-3, showed markedly increased phosphorylation in whole cells or isolated ghosts from ovalocytic individuals. The cytoplasmic domain of the ovalocyte Band-3 was found to be approx. 3 kDa larger than the normocytic protein. The N-terminal sequence of the ovalocytic Band-3 was different from the reported sequence for human Band-3, suggesting that the increased size results from an N-terminal extension. Since this is the region of Band-3 which is phosphorylated and interacts with the red cell cytoskeleton, it is likely that this alteration in ovalocytic Band-3 is the underlying cause of the diverse alterations in ovalocytic cells including increased phosphorylation, increased membrane rigidity, decreased agglutinability by blood group antibodies and refractoriness to invasion by malarial parasites.

Anion Exchange Protein 1, Erythrocyte↗
PubMed1990

Protein phosphorylation during the asexual life cycle of the human malarial parasite Plasmodium falciparum.

Recent evidence has suggested that extensive changes in the phosphorylation profile of red cell membrane proteins are associated with the invasion and development of the malarial parasite. In order to further define the role of parasite protein phosphorylation in these events we have looked at this phosphorylation using: (1) continuous metabolic labelling with [32P]orthophosphate, (2) pulse-labelling with [32P]orthophosphate and [35S]methionine, (3) autophosphorylation of infected cells using [gamma-32P]ATP, (4) invasion of prelabelled red cells. Many parasite proteins were labelled, some differentially according to the phosphorylation protocol employed, and we were able to partially characterise several of the major parasite phosphoproteins in terms of their association with host cell membrane and the stage specificity of phosphorylation.

Animals↗
PubMed1990

Rotational dynamics of the integral membrane protein, band 3, as a probe of the membrane events associated with Plasmodium falciparum infections of human erythrocytes.

Time-resolved phosphorescence anisotropy was used to study the molecular organisation of band 3 in the erythrocyte membrane. Three different rotational relaxation regimes of mobile band 3 were resolved. These populations may represent different aggregation states of band 3 within the membrane, or they may result from association of band 3 with other proteins at the cytoplasmic surface. The polycation spermine decreases the apparent mobility of band 3 by a mechanism that does not involve the underlying cytoskeleton. A monoclonal antibody directed against the cytoplasmic portion of band 3 can also cause an increase in the immobile fraction of band 3 molecules. This monoclonal antibody will inhibit invasion of erythrocytes by malaria parasites. Membranes prepared from erythrocytes infected with mature stages of the malaria parasite, Plasmodium falciparum, show altered dynamic properties corresponding to a marked restriction of band 3 mobility.

Animals↗
PubMed1990

The inhibitory influence of tracheal mucosa mounted in close proximity to canine trachealis.

Reduced smooth muscle contractile responses to agonists occur in the presence of epithelium, perhaps due to the release of an epithelium-derived relaxing factor (EpDRF). It is not clear whether the release of EpDRF requires the direct attachment of the epithelium to the smooth muscle. In the present study, using isolated canine tracheal smooth muscle strips, we examined whether the inhibitory effects of airway mucosa require the attachment of the mucosa to smooth muscle. The smooth muscle contractile responses to acetylcholine and histamine were reduced in the presence of airway mucosa, whether the mucosa was attached or in close proximity. The inhibitory effect mediated by the airway mucosa therefore is not dependent on mucosal attachment to smooth muscle. This phenomenon appears to be due to the release of a soluble, short-acting mediator from the airway mucosa.

Acetylcholine↗
PubMed1990

Identification of two promiscuous T cell epitopes from tetanus toxin.

Tetanus toxoid-specific T cell clones were isolated from a human donor. To determine the T cell epitopes recognized by the clones, 30 peptides representing amphipathic alpha helical regions of the tetanus toxin were screened for ability to induce proliferation of the clones. Two T epitopes were identified. These occurred within peptides 12 and 21, and had the amino acid sequences NSVDDALINSTKIYSYFPSV and PGINGKAIHLVNNESSE, respectively. An unusual feature was that both peptides could be presented to their respective T cell clones by antigen-presenting cells of many HLA specificities. Further investigation of peptide 12 showed that the epitope was only seven amino acids in length and had a very hydrophobic sequence, namely YSYFPSV. The ability of the T cell epitope-containing peptides 12 and 21 to interact with many different HLA alleles means they may potentially be very useful as "universal carrier molecules" in synthetic vaccines.

Amino Acid Sequence↗
PubMed1990

Peptide vaccines derived from a malarial surface antigen: effects of dose and adjuvants on immunogenicity.

Peptides P2122 (CKNNNSTNSGI) and P513 (CSQRSTNSAST) containing an epitope of a malarial surface antigen (MSA2) recognised by inhibitory monoclonal antibodies were conjugated to diphtheria toxoid (DT) protein and formulated with various gel-based and water in oil emulsion adjuvants in vaccine trials in mice and rabbits. The P2122-DT construct was effective in raising antibodies reactive with both the immunising peptide and the native antigen. Effective adjuvanticity as measured by the titre of the anti-peptide or anti-protein response in mice varied in the order: Algammulin, Montanide ISA 50 greater than or equal to Freund's adjuvant, Montanide ISA 708, 721, 70 much greater than alum, Squalene Arlacel greater than SAF-1. A similar order of adjuvant efficacy: Freund's greater than alum greater than Squalene Arlacel greater than SAF-1, was observed in rabbits.

Adjuvants, Immunologic↗