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Biomedical subjects

G R Siber

Publications and source records attributed to G R Siber.

At least 127 records · Page 7Linked to original sources
PubMed1986

Correlation of the Km(1) immunoglobulin allotype with anti-polysaccharide antibodies in Caucasian adults.

Km allotype antigens are serologic markers expressed on kappa light chains of human immunoglobulins. To determine whether th Km phenotype of an individual is related to his ability to make antibodies to polysaccharide antigens, we correlated the Km allotypes of 129 healthy caucasian adults with the concentrations of specific antibodies to three bacterial polysaccharide antigens after immunization. The 14 individuals expressing the Km(1) allotype had lower concentrations of IgG, IgM, and IgA antibodies by enzyme-linked immunosorbent assay and total antibody by radioimmunoassay to Haemophilus influenzae type b and Neisseria meningitidis group C capsular polysaccharides when compared with the 115 Km(1) negative individuals. The Km-associated differences in H. influenzae type b and N. meningitidis group C antibody concentrations were confined to kappa light chain-containing antibody (P = 0.029 and 0.003, respectively). Similarly, the Km(1) positives had slightly lower kappa chain-containing Ig than the Km(1) negatives (P = 0.079). We conclude that genes in or near the kappa light chain locus play a role in the regulation of kappa-containing antibody production to some bacterial polysaccharides and perhaps to other antigens.

Adult↗
PubMed1986

Antibody response to pretreatment immunization and post-treatment boosting with bacterial polysaccharide vaccines in patients with Hodgkin's disease.

Overwhelming sepsis is a serious complication of staging splenectomy in Hodgkin's disease. To define an optimal immunization strategy, 51 patients received 14-valent pneumococcal, Haemophilus influenzae type b, and meningococcal group C vaccines before therapy and 2 to 12 months after completion of therapy. Natural antibody levels to bacterial polysaccharide antigens and the response to immunization were normal or only minimally impaired in patients with Hodgkin's disease compared with findings in healthy adults. The antibody response was not affected by the timing of immunization relative to splenectomy but was frequently impaired if chemotherapy was begun less than 10 days after immunization. Both post-immunization and "natural" antibody declines were significantly greater in patients with Hodgkin's disease than in healthy adults; the magnitude of the decline was related to the intensity of therapy. A spontaneous rebound in antibody concentrations was not seen during the 12 months after treatment. Booster immunizations of all three vaccines given during this period also failed to elicit an antibody increase.

Adolescent↗
PubMed1985

Recurrent sinopulmonary infection and impaired antibody response to bacterial capsular polysaccharide antigen in children with selective IgG-subclass deficiency.

We studied 20 children with recurrent sinopulmonary infections and serum IgG levels within the normal range, who had selective IgG-subclass deficiency. Twelve of the children were IgG2 deficient, five were IgG3 deficient, and three were deficient in both IgG2 and IgG3. IgA deficiency was present in 3 of the 20 patients. In the children with IgG2 deficiency, serum antibody concentrations to the capsular polysaccharide of Hemophilus influenzae type B (Hib) were significantly lower than those in age-matched controls, both before and after immunization with the Hib capsular polysaccharide antigen, which elicits antibody predominantly of the IgG2 subclass. In contrast, their serum antibody titers to the tetanus and diphtheria toxoid protein antigens, which elicit antibody predominantly of the IgG1 subclass, were normal in comparison with those of age-matched controls. These results suggest that impairment of the antibody response to specific microbial antigens predisposes patients with selective IgG-subclass deficiencies to recurrent infections. Thus, as an aid in determining therapy, children with recurrent infections and normal total serum IgG should be evaluated for this condition.

Adolescent↗
PubMed1985

Cross-reactivity of rabbit antibodies to lipopolysaccharides of Escherichia coli J5 and other gram-negative bacteria.

Antiserum to rough gram-negative mutants such as Escherichia coli J5 and Salmonella minnesota Re595 is thought to neutralize the toxic effects of lipopolysaccharides (LPSs). To verify that such antisera are capable of binding heterologous endotoxins, we examined IgG and IgM class antibodies induced in rabbits to a variety of LPSs. Immunization with rough mutants or lipid A induced high IgG antibody responses to the homologous purified LPS and relatively low but significant responses to heterologous LPSs. Increases in IgM antibodies were also primarily to homologous LPS. Immunization with smooth organisms induced little or no antibody to heterologous LPSs. Soluble LPS, outer membrane vesicles, and whole bacteria produced strong homologous inhibition but little or no heterologous inhibition in enzyme-linked immunosorbent assays. Cross-adsorption of antisera to rough mutants suggested that the IgG and IgM antibodies induced to heterologous LPS were adsorbed by the heterologous LPS and not by the core LPS used to immunize the animals. Rabbit antibody directed to J5 or Re595 LPS fails to bind to any substantial degree to heterologous LPS. Immunization with whole bacterial vaccines, particularly the rough mutants and lipid A, does increase antibody to a wide variety of antigens. The possibilities that the protective effects of antisera to rough mutants are due to a polyclonal antibody response or to the induction of as yet unidentified factor(s) deserve further investigation.

Animals↗
PubMed1985

Binding and neutralization of bacterial lipopolysaccharide by colistin nonapeptide.

Polymyxin nonapeptides, proteolytic derivatives of polymyxin antibiotics, are less toxic than their parent compounds but retain some of their antibacterial activities. To confirm and expand observations that polymyxin nonapeptides have anti-endotoxin activity, we studied the ability of colistin nonapeptide to bind to bacterial lipopolysaccharide (LPS) and to inhibit the effects of LPS on Limulus amoebocyte lysate and lymphocyte mitogenicity. Colistin nonapeptide was purified by high-pressure liquid chromatography and was demonstrated to bind to LPS by equilibrium dialysis. The ability of colistin nonapeptide to render E. coli ATCC 25922 cells sensitive to erythromycin was abrogated by 50% after incubation with E. coli O18 LPS in a ratio by weight of LPS to colistin nonapeptide of 3.9:1. The presence of 4 micrograms of colistin nonapeptide or colistin per ml increased by 130- and 800-fold, respectively, the concentration of E. coli O113 LPS required to produce 50% gelation of Limulus amoebocyte lysate as measured by a spectrophotometric assay. Neutralization of LPS by colistin nonapeptide was time and concentration dependent. In contrast to the neutralization seen with LPS derived from a colistin-sensitive organism, colistin nonapeptide neutralized very little LPS extracted from a strain of Serratia marcescens that was resistant to colistin. Colistin nonapeptide also inhibited LPS-induced [3H]thymidine uptake by splenic lymphocytes, but its activity was less than 1/10 that of colistin. We conclude that colistin nonapeptide binds to LPS and possesses antiendotoxin activity. However, the anti-endotoxin activity of the nonapeptide is considerably less than that of its parent compound, colistin.

Chromatography, High Pressure Liquid↗
PubMed1985

Decreased protective efficacy of reduced and alkylated human immune serum globulin in experimental infection with Haemophilus influenzae type b.

Conventionally prepared immune serum globulin frequently produces severe side effects when administered intravenously. A modified preparation in which 4 to 5 interchain disulfide bonds have been reduced and alkylated has been made for intravenous use. However, reduction and alkylation may affect Fc-mediated functions of immunoglobulin G, particularly its ability to fix complement by the classical pathway. To determine whether reduction and alkylation alters the protective activity of immune serum globulin in vivo we compared it with two less harshly prepared globulins (pH 4 treated or ultrafiltered) in an infant rat model of Haemophilus influenzae b infection. Antibody binding to the capsular and noncapsular components of H. influenzae b and in vitro bactericidal activity were similar in the globulin preparations. Infant rats were treated with various doses of globulins adjusted to provide identical concentrations of anticapsular antibodies as measured by the Farr radioactive antigen binding assay. At high doses of anticapsular antibody (greater than 1,500 ng per pup), all preparations protected well. At marginal doses (750 ng per pup), however, rats given reduced and alkylated globulin had a significantly greater incidence of bacteremia (P less than 0.05), meningitis (P less than 0.01), and death (P less than 0.05) and a higher magnitude of bacteremia (P less than 0.02) than rats who received pH4-treated or ultrafiltered globulins. These differences were not due to differences in anticapsular antibody concentrations achieved in the serum. The 50% protective serum concentrations of anticapsular antibody in this model were 200 to 300 ng/ml for reduced and alkylated globulin and 100 to 200 ng/ml for acid-treated globulin. Absorption of the globulins with purified H. influenzae b capsule reduced in vitro bactericidal activity and rat protective activity. However, the magnitude of bacteremia was lower in rats receiving absorbed pH 4-treated globulin than in those receiving absorbed reduced and alkylated globulin (P less than 0.05). We conclude that reduced and alkylated immunoglobulin G provides significantly less protective activity against H. influenzae b infection in this model than globulins not so modified, and we suggest that the altered Fc function of the immunoglobulin G, such as the decreased ability to fix complement by the classical pathway or decreased Fc-mediated opsonization, may be responsible for this impairment.

Alkylation↗
PubMed1985

Turbidimetric method for quantifying serum inhibition of Limulus amoebocyte lysate.

This study describes a method to quantify the inhibition of lipopolysaccharide (LPS) activity by serum with a turbidimetric Limulus amoebocyte lysate assay. Assays were performed in multiwell microplates, and turbidity was measured as the optical density at 380 nm with a microplate spectrophotometer. LPS potency was measured as the 50% maximal Limulus amoebocyte response (LR50) of LPS diluted with saline. By comparing LR50s in saline, LPSs from various species of bacteria were standardized against the U.S. Reference Standard Endotoxin, lot EC-5. The potency of Escherichia coli O113 and O18 and Serratia marcescens LPSs was found to be equal to that of the reference standard EC-5, whereas LPSs from two salmonella species were half as potent. The least potent LPSs tested, obtained from Klebsiella pneumoniae and E. coli rough mutant J5, were 5- and 10-fold less potent, respectively, than EC-5. As a measure of inhibition, the LR50 of LPS in serum was compared to the LR50 of LPS in saline. Serum inhibited the potency of LPS 103- to 6,400-fold compared with saline. A positive correlation was found between standardized potency in saline and serum inhibition of the various LPSs tested. Thus, LPSs from E. coli O113, O18, and EC-5 and S. marcescens, which exhibited the highest potency in saline, were inhibited the most by serum. Likewise, E. coli J5 and K. pneumoniae LPSs, which were the least potent tested, were the least inhibited. The degree of inhibition of all types of LPS tested increased with increasing serum concentration.

Blood↗
PubMed1985

Neutralization of bacterial lipopolysaccharides by human plasma.

To quantify the neutralization of bacterial lipopolysaccharide (LPS) by human plasma, dilutions of Escherichia coli O113 LPS were incubated with plasma, followed by the addition of Limulus amebocyte lysate (LAL). The reaction between the LPS and LAL was monitored spectrophotometrically, and the concentration of LPS resulting in 50% lysate response (LR50) was determined. Analysis of 145 outdated plasma samples yielded a range of LR50 between 6 and 1,500 ng/ml. Pools of plasma with high and low LR50 were prepared. The pool with high LR50 neutralized 166-fold more E. coli 0113 LPS, 190-fold more E. coli 0111B4 LPS, 42-fold more Klebsiella pneumoniae LPS, and 29-fold more Salmonella typhimurium LPS than did the pool with low LR50. Each pool had similar immunoglobulin G (IgG) and IgM antibody levels to homologous LPS, measured by an enzyme-linked immunosorbent assay. Analysis of 212 fresh-frozen plasma units revealed a range of LR50 between 48 and 6,000 ng/ml. Incubation of LPS in a pool of fresh-frozen plasma with high LR50 elicited significantly less fever in the rabbit pyrogen test than did LPS incubated in plasma with low LR50 (fever index, 2.68 +/- 0.61 degrees C X h and 3.52 +/- 0.66 degrees C X h, respectively; P = 0.003). We conclude that there is a 100-fold range in the endotoxin-neutralizing capacity of human plasma and that this variation is not due to LPS-specific IgG or IgM antibodies. Further investigations are needed to determine whether differing susceptibility of patients to the effects of LPS is due to differences in the endotoxin-neutralizing capacity of their plasma and whether plasma screened for high endotoxin-neutralizing capacity may be therapeutically useful in endotoxemia.

Animals↗
PubMed1985

Correlation between G2m(n) immunoglobulin allotype and human antibody response and susceptibility to polysaccharide encapsulated bacteria.

To determine whether genetic factors influence the human antibody response to polysaccharides, we correlated Ig allotypes with the concentrations of antibody to 14 bacterial capsular antigens in 130 actively immunized Caucasian adults. The 88 individuals possessing G2m(n), an allotype antigen of IgG2 subclass heavy chains, had significantly higher postimmunization antibody levels to Haemophilus influenzae type b (Hib) and 8 of 11 pneumococcal types (P less than 0.05) than the 42 lacking this antigen. For Hib, pneumococcus type 14, and meningococcus group C, an increased response was observed in IgG class but not in IgM or IgA classes of antibody. The G2m(n) positive individuals also had higher preimmunization antibody levels to most polysaccharide antigens. Total IgG2 concentrations were correlated with the mean postimmunization antibody concentrations to pneumococci (P = 0.005), but this correlation was independent of G2m(n) by multiple regression analysis. To determine if the lack of G2m(n) was associated with increased susceptibility to infection, we compared the frequencies of various Ig allotypes in 98 children infected with Hib and 98 matched controls. Caucasian children with Hib infections other than epiglottitis were significantly more likely to lack the G2m(n) allotype than controls (P less than 0.05). G2m(n) negative Caucasian children less than or equal to 18 mo old have a 5.1-fold higher risk of nonepiglottitic Hib infections than G2m(n) positive children (P less than 0.01). We conclude that allotypic variants of the gamma-2 heavy chain genes, or genes in linkage equilibrium with them, exert a regulatory influence on the caucasian antibody response to a variety of immunologically distinct bacterial polysaccharide antigens. Young Caucasian children of the low responder phenotype, i.e., those lacking the G2m(n) allotype, are genetically predisposed to Hib and perhaps other bacterial infections.

Adult↗
PubMed1984

Preparation of human hyperimmune globulin to Haemophilus influenzae b, Streptococcus pneumoniae, and Neisseria meningitidis.

As a first step in exploring the feasibility of passive antibody prophylaxis and therapy of serious infections caused by common encapsulated bacteria, we have immunized healthy adults with Haemophilus influenzae type b vaccine, 14-valent pneumococcal vaccine, and meningococcal group A and C vaccine; collected plasma by repeated pheresis; and purified a hyperimmune globulin termed bacterial polysaccharide immune globulin by the cold-ethanol fractionation method of Cohn and Oncley. Specific antibacterial antibody concentrations were measured in individual donors before and after immunization. In addition, antibody concentrations were measured in plasma pools prepared from immunized donors and from unimmunized controls and in the immunoglobulin-containing Cohn-Oncley fractions II and III derived from the respective plasma pools. A comparison of Cohn-Oncley fractions II, which contain primarily immunoglobulin G and which are used therapeutically as immune globulin, revealed that antibody to H. influenzae type b was enriched 15.3-fold and that antibody to meningococcal serogroups and pneumococcal types was enriched a mean of 4.4-fold (range, 1.2- to 9.9-fold). Enrichment of antibacterial antibody in Cohn fraction III, which contains substantial amounts of immunoglobulin M and immunoglobulin A in addition to immunoglobulin G, closely paralleled that in fraction II. Only antibodies to pneumococcal types 1 and 7 were increased disproportionately in fraction III. Based on the clinical experience that conventional immune serum globulin at a dose of 100 mg/kg protects agammaglobulinemic patients for ca. 1 month, we estimate that bacterial polysaccharide immune globulin, in similar dosage, will provide protection from systemic H. influenzae type b infection for 4 to 6 months and from pneumococcal and meningococcal infections for 3 to 4 months.

Antibodies, Bacterial↗
PubMed1983

High-performance liquid chromatographic quantitation of trimethoprim, sulfamethoxazole, and N4-acetylsulfamethoxazole in body fluids.

We describe a rapid, precise and simple procedure for the quantitative determination of trimethoprim, sulfamethoxazole, and N4-acetylsulfamethoxazole in body fluids by reversed-phase high-performance liquid chromatography. This method utilizes antipyrine as an internal standard with the compounds detected by dual-wavelength monitoring at 225 nm and 254 nm after a single-step extraction. Precision, sensitivity, and accuracy of this assay are within the range of clinical utility; the coefficient of variation is less than or equal to 3%, sensitivity less than 0.5 micrograms/ml for all compounds, and recovery greater than 97%. The short time for performance and small sample size makes the assay ideal for clinical drug monitoring and pharmacokinetic studies.

Chromatography, High Pressure Liquid↗
PubMed1983

Efficacy of human hyperimmune globulin in prevention of Haemophilus influenzae type b disease in infant rats.

To determine the protective efficacy of human hyperimmune globulin to Haemophilus influenzae type b disease in an infant rat model, we compared hyperimmune globulin containing 600 mug of anti-polyribophosphate (PRP) antibody per ml to conventional immune globulin containing 66 mug of anti-PRP antibody per ml. The hyperimmune globulin was fractionated from the pooled plasma of 55 adult donors immunized with PRP, the capsular polysaccharide of H. influenzae type b. The disappearance of passively administered antibody was biphasic, with a linear first-order disappearance curve during the first 7 days. The initial half-life for anti-PRP antibody was 2.38 days in rats nasally colonized but not detectably bacteremic with H. influenzae type b and significantly longer (half-life, 10.3 days; P < 0.01) in noncolonized animals. Hyperimmune globulin afforded 10 times the protection of conventional globulin against bacteremia and meningitis. Globulin depleted of anti-PRP antibody offered no protection. The initial serum antibody levels and the levels during the 8-day observation period predicted protection. Rats maintaining serum antibody levels greater or equal to 50 ng/ml to day 8 had a 10% bacteremia and 5% meningitis incidence in contrast with 95% bacteremia (P < 0.001) and 55% meningitis (P < 0.001) in rats with less than 50 ng of anti-PRP antibody per ml. We conclude that studies of the pharmacology and efficacy of hyperimmune globulin are warranted in high-risk children unable to respond to active immunization.

Animals↗
PubMed1982

Enhanced detection with an enzyme-linked immunosorbent assay of candida mannan in antibody-containing serum after heat extraction.

A double-antibody, solid-phase enzyme-linked immunosorbent assay was developed for detection of candida antigen(s) in serum and body fluids. The assay detected mannan purified from Candida albicans cells with a sensitivity of 1 ng/ml in buffer, but it was 1,000-fold less sensitive in pooled human serum. Because antibody appeared to be the major blocking factor in serum, a rapid and efficient heat-extraction method for recovering mannan from antibody-containing serum was devised. The assay detected antigenemia within 24 hr in all of 30 lethally infected rats, and antigenemia persisted until their deaths. Eight of 15 patients with documented or suspected candidiasis had antigenemia at levels ranging from 5 to greater than 1,000 ng/ml.

Animals↗
PubMed1982

Moxalactam pharmacokinetics in children.

We measured the serum concentrations of moxalactam in 10 children receiving antibiotic prophylaxis for surgery and in 18 children treated for documented or suspected infections. Moxalactam was administered intravenously at a dose of 50 mg/kg every 8 h. After the first dose in 28 patients, mean moxalactam concentrations 5 min, 30 min, 2 h, and 8 h after infusion were 257, 177, 82.2, and 17.5 micrograms/ml, respectively. The mean half-life (T 1/2) was 2.44 h (range: 0.55 to 7.96 h). The mean distribution volume (VD) was 0.30 liters per kg. No significant accumulation was observed with multiple doses. Prophylactic and therapeutic groups had similar serum levels, T 1/2, and VD. The five infants less than 1 year of age had a lower mean 30-min level (P less than 0.01), larger VD (P less than 0.001) and longer T 1/2 (P less than 0.025) than the children older than 1 year. A dose of 50 mg/kg produced 30-min levels in excess of 64 microgram/ml in all patients studied, but 8-h trough levels were below the minimal inhibitory concentrations breakpoint of 17 mg/ml in 32% of patients.

Adolescent↗
PubMed1982

Blood-group-A-like substance in a preparation of pneumococcal vaccine.

A platelet transfusion from a blood group O donor, immunized 1 month before with Pneumovax, caused a hemolytic reaction in a blood group A recipient. Forty-five of 59 group O donors (76%) and all of nine group B donors immunized with Pneumovax had a fourfold or higher anti-A response. Half of the anti-A antibody in high titered donors was in the IgG fraction. Pneumovax contained approximately 30 micrograms of an A-like substance per dose; polyvalent pneumococcal vaccines prepared by two other manufactures contained very low and probably subimmunogenic concentrations. Several culture media prepared from animal tissues contained as antigen of similar physical, immunologic, and chemical properties, and were the most likely source of the contaminant. Manufacturing procedures have since been revised to eliminate A-like substances.

ABO Blood-Group System↗
PubMed1982

Evaluation of a commercial latex particle agglutination test for rapid diagnosis of Haemophilus influenzae type b infection.

The effectiveness of a commercially available latex particle agglutination test (Bactogen) in the diagnosis of invasive Haemophilus influenzae type b infection was evaluated. Bactogen correctly diagnosed all 27 patients with bacteriologically proven H influenzae type b infection (sensitivity 100%). Two of 39 patients with proven, non-H influenzae type b infections had false-positive tests (specificity 95%). One of 103 sera and 0 of 55 urine specimens from hospitalized adults contained detectable H influenzae type b antigen. Bactogen is a sensitive, specific, commercially available test for rapid diagnosis of H influenzae type b infection.

Evaluation Studies as Topic↗