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Biomedical subjects

R L Hunter

Publications and source records attributed to R L Hunter.

At least 73 records · Page 4Linked to original sources
PubMed1992

Effect of adjuvant formulations on the selection of B-cell epitopes expressed by a malaria peptide vaccine.

Because subunit vaccines may create artificial epitopes, the goal of this study was to concentrate the immune response toward protective epitopes contained in a peptide, [(NAGG)5]Y. This peptide consisted of five repeat sequences of the immunodominant epitope of the circumsporozoite protein of the simian malaria parasite Plasmodium cynomolgi and a terminal tyrosine. It was conjugated to bovine serum albumin and mixed with various adjuvant formulations, including block copolymers L121, L141, L180.5 and a lipopolysaccharide (LPS). Outbred mice were vaccinated with seven vaccine formulations. Postvaccination sera from each group of mice were then pooled, and antibody responses against peptide [(NAGG)5]Y or (NAGG)5 were tested in an enzyme-linked immunosorbent assay and against sporozoites of P. cynomolgi in an indirect fluorescent antibody assay. Although all groups elicited a high antibody response to the peptide [(NAGG)5Y], the presence of the tyrosine induced a different antibody response to the peptide (NAGG)5, and formulations containing LPS alone did not induce an antibody response to either (NAGG)5 or P. cynomolgi sporozoites. The formulation including both LPS and the copolymer L121 was the only one to inhibit the development of P. cynomolgi sporozoites in rhesus monkey hepatocytes by 50%. These results suggest that vaccine formulations influence B-cell epitope selection.

Animals↗
PubMed1991

Murine IgG isotype responses to the Plasmodium cynomolgi circumsporozoite peptide (NAGG)5. I. Effects of carrier, copolymer adjuvants, and lipopolysaccharide on isotype selection.

The tandem repeat peptide of the circumsporozoite protein of Plasmodium cynomolgi, (NAGG)5, conjugated to BSA or Salmonella flagella, was injected into mice with block copolymer and other adjuvants. The flagella carrier preferentially stimulated IgG2a antibodies to (NAGG)5 that constituted as much as 85% of the total IgG antibody whereas the BSA carrier stimulated as much as 98% IgG1. The distribution of isotypes of antibody to (NAGG)5 was also modified by using the copolymer adjuvants L121 or L141, either alone, or especially in combination with a nontoxic LPS. L121 or L141 increased the proportion of IgG2a and IgG2b antibodies to (NAGG)5 after immunization with (NAGG)5-BSA whereas LPS stimulated further increases in IgG2 antibodies (up to 69% of the total IgG). The hapten density, physical form of emulsion, and route of immunization further affected the isotypes produced in this study.

Acetylmuramyl-Alanyl-Isoglutamine↗
PubMed1991

Reduction of myocardial infarct size by poloxamer 188 and mannitol in a canine model.

Poloxamer 188 has been reported to inhibit thrombosis, decrease whole blood viscosity, and improve perfusion of damaged tissue. Mannitol has free radical scavenging capabilities that might contribute to myocardial salvage after ischemia. Because these agents appear to work in different ways, we studied their cardioprotective properties when they were used separately and in combination. After 75 minutes of left anterior descending coronary artery (LAD) occlusion, dogs received poloxamer 188 (48 mg/kg), mannitol (0.5 gm/kg), or both intravenously during an additional 15 minutes of LAD occlusion and for 45 minutes of reperfusion, whereas control dogs received an equal volume of saline solution. After surgery the animals were maintained for 24 hours and then killed. Areas of myocardial infarction (MI) and risk of infarction (R) were calculated by means of planimetric analysis of slices of myocardium stained with 1.5% triphenyltetrazolium and 0.5% Evans blue dye. The ratio of MI/R (mean +/- standard error of the mean) were: control, 25.6 +/- 1.8% (n = 10); poloxamer 188, 12.7 +/- 2.0% (n = 10); mannitol, 10.6 +/- 2.5% (n = 11); and poloxamer 188 plus mannitol, 8.0 +/- 4.1% (n = 10). Measurement of microvascular blood flow indicated a similar 86% to 91% reduction of blood flow to the area at risk in all treatment groups. Consequently both poloxamer 188 and mannitol appear to increase salvage of ischemic myocardium and a combination of the two may be more effective than either agent alone.

Animals↗
PubMed1991

Adjuvant activity of non-ionic block copolymers. V. Modulation of antibody isotype by lipopolysaccharides, lipid A and precursors.

Non-ionic block copolymers and lipopolysaccharides are both effective immunological adjuvants which are thought to act via distinct mechanisms. We hypothesized that they might produce synergistic effects when used together. We prepared a series of lipopolysaccharide (LPS) preparations ranging from the smallest precursor, lipid X through complete LPS with O-polysaccharide chains. Three preparations with reduced toxicity, monophosphoryl lipid A, partially hydrolysed Ra-LPS and LPS of Rhodopseudomonas sphaeroides were also utilized. All LPS preparations except the smallest were effective adjuvants for inducing early antibody responses to trinitrophenyl-conjugated hen egg albumin (TNP-HEA) when injected in squalane-in-water emulsions with copolymer L141. Only the larger LPS preparations induced sustained antibody responses. By itself, emulsions of copolymer L141 induced a predominant IgG1 antibody isotype response with lesser amounts of IgG2a and IgG2b. Surprisingly, all of the LPS preparations tested increased the proportion of IgG2 isotypes even though some had little effect on overall titres. The detoxified Ra-LPS (Ra-detox) was the most effective preparation for both increasing antibody titres and inducing the desirable IgG2a and IgG2b isotypes. These results demonstrate that the combination of LPS and block polymer adjuvants can produce synergistic effects without unacceptable toxicities.

Adjuvants, Immunologic↗
PubMed1991

Immunogenicity of Streptococcus pneumoniae type 14 capsular polysaccharide: influence of carriers and adjuvants on isotype distribution.

This project investigated the effects of novel carriers and adjuvants on the isotype of murine immunoglobulin G (IgG) antibody to pneumococcal capsular polysaccharide type 14 (S14PS). S14PS conjugated to bovine serum albumin induced a weak antibody response which was 100% IgG1 following injection without adjuvant. The same polysaccharide conjugated to flagella of Salmonella typhi induced an antibody response which was 88% IgG3. S14PS-bovine serum albumin was injected with block copolymer L121 or Quil A in squalane-in-water emulsions. The copolymer L121 was at least as effective as Quil A or complete Freund adjuvant in inducing IgG antibodies. IgG1 was the dominant subclass for all. Addition of monophosphoryl lipid A, but not the threonyl derivative of muramyl dipeptide or nontoxic Rhodopseudomonas sphaeroides lipopolysaccharide, to copolymer L121 increased production of the IgG2a, IgG2b, and IgG3 subclasses. S14PS-flagella with copolymer L121 induced higher titers with a markedly altered isotype distribution: 13% IgG1, 52% IgG2a, 6% IgG2b, and 29% IgG3. Monophosphoryl lipid A added to L121 reduced IgG1 antibody to 5%, but increased IgG2a antibody to 14%, IgG2b antibody to 3%, and IgG3 antibody to 78%. These studies demonstrate that both the carrier and the adjuvant can influence the titer and isotype distribution of antipolysaccharide antibody responses.

Adjuvants, Immunologic↗
PubMed1990

Induction of macrophage Ia expression in vivo by a synthetic block copolymer, L81.

Certain synthetic, nonionic, block copolymers of polyoxypropylene and polyoxyethylene are potent immunoadjuvants. While investigating their mechanisms of action, we found that one of these copolymers, L81, induced the expression of macrophage Ia in vivo. L81 is a 2750-Da, linear copolymer with a 43-unit core of hydrophobic polyoxypropylene flanked on each side by 3 U of hydrophilic polyoxyethylene. It induced threefold to sevenfold increases in the proportion of peritoneal macrophages expressing I-A from 5 to 7 days after an i.p. injection of 5 mg. As little as 1 mg caused a twofold increase. I-A density increased with time after injection of L81. Macrophages induced by L81 actively synthesized I-A, showing an 18-fold increase in biosynthetic capacity. Ia induction did not require the presence of mature T lymphocytes, because similar increases in I-A expression were seen in athymic and euthymic mice. L81-induced macrophages were 10-fold more effective than normal macrophages in presenting Ag to a T cell hybridoma. Other functional studies showed that they were primed for the secretion of superoxide ion and could be stimulated in vitro by IFN-gamma and LPS to lyse tumor target cells. These results suggest that the induction of macrophage Ia expression by L81 may play a role in its activity as an immunoadjuvant.

Adjuvants, Immunologic↗
PubMed1990

Increased whole blood viscosity during coronary artery bypass surgery. Studies to evaluate the effects of soluble fibrin and poloxamer 188.

This study was designed to test the hypothesis that soluble fibrin complexes resulting from the trauma of surgery could produce elevated blood viscosity, to characterize the soluble fibrin polymers, and to evaluate in vitro the effect of a new hemorheologic agent, poloxamer 188, on viscosity in these abnormal situations. Ten patients undergoing aortocoronary bypass surgery were studied before and at various times after surgery. By 6 h after surgery, the mean hematocrit decreased by 23%, fibrinogen decreased 48%, and erythrocyte sedimentation rate decreased 33%, whole blood viscosity at a low shear rate rose on average of 69% and soluble fibrin rose 118%. Over the 6-day observation period, the concentrations of soluble fibrin paralleled the changes in viscosity, whereas the concentrations of fibrinogen varied nearly inversely with viscosity. The effects of various forms of fibrinogen and fibrin were tested by additions to normal blood. Soluble fibrin polymers, but not fibrin monomers, increased blood viscosity two to three fold. Poloxamer 188 reduced the viscosity of all patient samples to the normal range. These data support the hypothesis that increased whole blood viscosity at low shear rates is caused by hydrophobic adhesion of fibrin polymers to red cells and that poloxamer 188 normalizes viscosity by effectively disrupting the weak hydrophobic bonds.

Biopolymers↗
PubMed1990

Immunoendocrine modulation and stimulation of hematopoiesis with the ionophore copolymer T150R1.

T150R1, an 8000-dalton copolymer with sodium ionophore activity, has been shown to modulate cellular responses in multiple systems. In this article, we studied its effects on lymphoid and hematopoietic organs in the context of the adrenal-pituitary axis. When injected in mice as an oil in water emulsion, T150R1 caused a rapid, profound, and dose-dependent thymic involution accompanied by splenic hyperplasia. Time course experiments with a 2.5-mg dose revealed that the thymus size was minimal at Day 2, rose to normal by Day 14, then enlarged and gradually returned to normal by Week 6 postinjection. Thymic involution was due to cellular depletion of the cortical area, whereas thymic enlargement was due to cortical hyperplasia. Splenomegaly was seen as early as Day 4, peaked by Day 14, and gradually returned to normal by Week 6. The splenic enlargement was due to hyperplasia of the red pulp, with evidence of proliferating erythropoietic, myelopoietic, and megakaryopoietic precursors. In addition, the bone marrow was stimulated and extramedullary hematopoiesis was present in the liver. The effects of T150R1 on the thymus appeared to be mediated by corticosteroids while the effects on hematopoiesis were not. Corticosterone and ACTH levels were increased in treated animals. Adrenalectomy diminished the T150R1-induced thymic involution but enhanced the splenic hyperplasia. Hypophysectomy did not prevent thymic involution, suggesting that T150R1 has endocrine stimulatory effects. These data suggest that T150R1 represents a new class of ionophores which may act on excitable cells within the endocrine, immune, and hematopoietic systems.

Adrenalectomy↗
PubMed1989

An improved method for determining the microbial inhibitory activity of serum and its application to the study of patients with leukemia.

Numerous investigators have demonstrated that derangements in serum transferrin and iron can contribute to susceptibility to infection, but the complexity and imprecision of assays have impeded both research and development of clinical testing in this area. This article describes an automated assay for measuring the microbial inhibitory activity of transferrin in serum and its use in patients with acute myelogenous leukemia (AML) and in normal controls. The assay measured the ability of heat-inactivated serum to inhibit the growth of an antibiotic-resistant strain of Pseudomonas aeruginosa. The serum dilutions were prepared in a special low iron chemically defined broth. An inhibition index, the reciprocal of the serum dilution producing 50% inhibition of bacterial growth when compared with the growth in broth alone, was determined. The results showed the serum from the patients with leukemia had a significantly lower inhibition index than that of controls (16 +/- 11 vs. 35 +/- 13, P less than 0.01). In addition, they had higher serum iron levels (162 +/- 65 vs. 75 +/- 27, P less than 0.01), lower serum transferrin levels (231 +/- 65 vs. 309 +/- 71, P less than 0.01), and higher percentage saturation of transferrin with iron (59 +/- 21 vs. 20 +/- 8, P less than 0.01) than did controls. Because the assay uses equipment available in many clinical laboratories, it could be developed for routine use as an index of susceptibility to infection in selected patients.

Blood Bactericidal Activity↗
PubMed1989

Modification of acute focal ischemia in rabbits by poloxamer 188.

We studied the effect of a synthetic copolymer surfactant, poloxamer 188, on cerebral blood flow in a rabbit model of focal cerebral ischemia. Following retro-orbital craniectomy, the parietal branch of the middle cerebral artery was occluded with bipolar current. Cerebral blood flow was measured by the hydrogen clearance technique using platinum-iridium electrodes placed within the parietal cortex. Ten rabbits were infused with 50 mg/kg poloxamer 188 in saline beginning 30 minutes after occlusion; 12 control rabbits received an equal volume of saline. Poloxamer 188 increased blood flow significantly in areas of severe or moderate ischemia but had little effect in areas with mild or no ischemia. The improvement in blood flow could not be accounted for by hemodilution, and the copolymer did not affect blood viscosity at any shear rate from 1 to 100 sec-1. We hypothesize that poloxamer 188 increases circulation in ischemic tissue by inhibiting adhesive interactions among proteins (fibrin and fibrinogen) and cells in the microcirculation.

Animals↗
PubMed1988

In vitro release of histamine from murine mast cells by block co-polymers composed of polyoxyethylene and polyoxypropylene.

A series of block co-polymers composed of polyoxyethylene and polyoxypropylene were investigated for their ability to induce in vitro activation of mouse mast cells. We found that six of these co-polymers could cause histamine release from mouse mast cells in vitro. At low concentrations, the most efficacious co-polymer, T130R2, caused rapid and extensive concentration-dependent release of histamine from mouse mast cells. The release process was not cytotoxic; it required metabolic energy and was not accompanied by release of lactate dehydrogenase. Optimal release of histamine was dependent on both calcium and sodium ions in the extracellular medium. The degree of in vitro histamine release correlated with in vivo inflammation and in vitro ionophore activity. We believe that this represents the first report of the activation of mediator-containing cells by an ionophore selective for monovalent cations. These copolymers may therefore represent new reagents for investigations of cellular excitation.

Adjuvants, Immunologic↗
PubMed1988

Histamine release from human basophils by synthetic block co-polymers composed of polyoxyethylene and polyoxypropylene and synergy with immunologic and non-immunologic stimuli.

Co-polymers composed of polyoxyethylene and polyoxypropylene have been shown previously to trigger histamine release from mouse peritoneal mast cells; this property quantitatively is directly related to the ionophorous ability of these compounds to cause a functional exchange of intracellular K+ for extracellular Na+ across the cell membrane. We investigated the effect of an inflammatory copolymer, T130R2, on human basophils. The data demonstrate that T130R2 can cause calcium-dependent histamine release from human basophils in vitro. Further, at concentrations that do not cause histamine release, this co-polymer markedly augments release by suboptimal concentrations of the lectin Con A or anti-IgE antibody and the phorbol ester 12-O-tetradecanoyl-phorbol-13-acetate but not the calcium ionophore A23187. Thus, these co-polymers induce mediator release from cells of both rodents and humans. In both instances it is likely that calcium-dependent cell triggering is the result of an influx of sodium ions with concomitant depolarization of the transmembrane potential. In common with the calcium ionophore A23187, the co-polymer T130R2 has the ability to synergize with stimuli which trigger the IgE receptor as well as those which directly activate the cellular calcium- and phospholipid-dependent protein kinase.

Adjuvants, Immunologic↗
PubMed1988

Ion transport mediated by copolymers composed of polyoxyethylene and polyoxypropylene.

Block copolymers composed of polyoxyethylene and polyoxypropylene were found to increase the influx of Na+ and the efflux of K+ from human erythrocytes. They were, however, ineffective at promoting the transport of Ca2+. The size of the ion fluxes induced by the copolymers correlated with their efficacy in stimulating inflammation. These compounds were also found to induce conductance increases in planar lipid bilayers in a nonvoltage dependent and nonstepwise manner. In both experimental systems, ion transport was facilitated only under temperature and ionic-strength conditions in which the polymers form aggregates in aqueous solution. In neither system did the concentration dependence of transport activity exhibit a pronounced cooperativity. These observations are consistent with the view that aqueous monomers of these surface active agents partition into the membrane, where they facilitate the conductive movement of monovalent cations by means of a carrier type mechanism. As a novel class of ionophores, these substances are of practical interest because they can be water soluble and are potentially reversible.

Biological Transport↗
PubMed1987

Electrophoretic mobility, concentration, and activity of alpha 1-antitrypsin in serum of patients undergoing bone-marrow transplantation.

We have observed an electrophoretically abnormal, nonfunctional species of alpha 1-antitrypsin in serum from patients who were receiving bone-marrow transplants for treatment of leukemia or aplastic anemia. Three of four patients in whose serum this protein appeared died soon after; the fourth recovered, and the disappearance of the abnormal alpha 1-antitrypsin paralleled his recovery. This suggests that the inability to maintain functional activity of alpha 1-antitrypsin predisposes patients to life-threatening complications during recovery from bone-marrow transplants.

Anemia, Aplastic↗
PubMed1986

Densitometric quantitation of high resolution agarose gel protein electrophoresis.

The authors developed a cost-effective procedure for high-resolution protein electrophoresis in agarose gel which results in electrophoretic patterns that can be both visually interpreted and densitometrically quantitated. Unique features include the development of special molds for the preparation of several gels simultaneously and the combination of chemical with densitometric procedures to accurately quantitate the protein fractions in both normal and pathologic sera. Since the albumin concentrations obtained by densitometric scan of either cellulose acetate or agarose gel were erratic with respect to colorimetric (ACA) or immunochemical (ICS) measurements, the authors incorporated colorimetric measurements of albumin and total protein with densitometric quantitation of the electrophoretic bands into an algorithm for calculating protein concentrations. The densitometric quantitation of the gamma globulin fractions compared well with the sum of the immunochemically determined IgG and IgM concentrations (r = 0.98). Alpha and beta globulins were calculated using mathematically adjusted densitometric scan percentages and the total alpha and beta globulin protein concentration. The agarose gel procedure was more sensitive than cellulose acetate in the detection of paraprotein bands in a comparison of 93 sera containing paraproteins.

Blood Protein Electrophoresis↗
PubMed1986

The adjuvant activity of nonionic block polymer surfactants. III. Characterization of selected biologically active surfaces.

We evaluated the molecular and physicochemical properties of surfaces formed by defined layers of block copolymers which were especially effective as adjuvants or in the induction of granulomas. The copolymers which were adjuvants formed hydrophilic surfaces with a large area. They bound protein in a way which left it particularly accessible to antibody and induced the activation of complement. Copolymers which induced granulomas, in contrast, formed hydrophobic crystalline surfaces. They bound less protein and did not activate complement, but were toxic for macrophages. Their surfaces were found to be similar to those of the mycobacterial glycolipid trehalose-6,6'-dimycolate or quartz, in that they consisted of regular geometric arrays of hydrophilic and hydrophobic adsorptive domains. These studies demonstrated that changes in the size and arrangement of hydrophilic and hydrophobic blocks in copolymers produce a diversity of surface physicochemical properties which correlate with biologic activity.

Adjuvants, Immunologic↗
PubMed1985

Direct measurement of antibody production in cell suspensions using an enzyme-linked immunosorbent assay.

We have developed an enzyme-linked immunosorbent assay (ELISA) to measure antibody production in cell suspensions using highly sensitive avidin-biotinylated peroxidase (ABC) reagents. The cells are serially diluted in media and placed directly on a standard antigen-coated microtiter plate for 6 h, and the plate is then washed and processed to determine the bound antibody. The amount of antibody detected is reduced by puromycin indicating in vitro synthesis. Standard errors of the means of optical density readings of replicate samples are less than 10%. The background readings and readings obtained using non-immune cells are negligible, demonstrating no significant contamination by endogenous peroxidases.

Animals↗