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G R Siber

Publications and source records attributed to G R Siber.

At least 109 records · Page 6Linked to original sources
PubMed1990

Interpretation of IgG subclass values: a comparison of two assays.

Because we have noted discordant results in the measurement of IgG subclass concentrations by means of a widely available commercial radial immunodiffusion (RID) kit in comparison with an enzyme-linked immunosorbent assay (ELISA) developed at the Centers for Disease Control (CDC), we conducted in a blinded manner a comparison of the two assays, using sera from 48 healthy children. The correlation coefficients between the assays were 0.92, 0.82, 0.93, and 0.86 for the IgG1, IgG2, IgG3, and IgG4 assays, respectively. However, the RID assay assigned lower values for IgG1 and IgG4 determinations than the ELISA did. Furthermore, the "normal lower range values" provided by the RID assay were higher for each IgG subclass. When the sera from the healthy control subjects were analyzed with the RID assay, 12 (25%) of 48 subjects had values below the normal range for at least one subclass measurement. In contrast, with the CDC ELISA, all values were within the 95% confidence limits determined for the CDC ELISA. We suggest that age-specific normal limits be established with the use of sera from many healthy subjects for any assay measuring IgG subclass concentrations. As new groups of immunodeficiencies are defined and potential therapies are advocated, careful attention to assay standardization will result in a clearer delineation of these disease groups and of their response to treatment.

Child↗
PubMed1990

Kappa and lambda light chain composition of antibody to the capsular polysaccharide of Haemophilus influenzae type b.

Concentrations of total immunoglobulins bearing kappa and lambda light chains were measured in the sera of 215 healthy white children aged 6 months to 10 years. Both kappa and lambda concentrations increased with age. However, the concentration of immunoglobulins bearing kappa light chains increased at a greater rate than those bearing lambda light chains (P = .01). Thus, the kappa:lambda ratio of the youngest children (6-24 months) was significantly lower than that of the oldest (25-130 months) (P = .0015). The relationship between the IgG antibody concentration and the light chain composition of the specific antibody directed to Haemophilus influenzae type b (Hib) polysaccharide was also assessed in 62 of 215 serum samples with detectable Hib antibody. The IgG Hib antibody concentration was strongly correlated with the kappa:lambda Hib antibody ratio (r = .60, P = .001), and this correlation was independent of age. Thus, light chain selection and response to polysaccharides may be regulated by common mechanisms that mature late in ontogeny.

Antibodies, Bacterial↗
PubMed1989

Ig allotype-linked regulation of class and subclass composition of natural antibodies to group A streptococcal carbohydrate.

To determine the importance of genes located in or near the Ig constant regions in regulating the human antibody response, we correlated Ig allotypic markers with total Ig concentrations and natural antibody concentrations to the streptococcal group A carbohydrate (A-CHO) in 193 healthy adult blood donors. The major correlations between Ig allotypes and total Ig and specific antibody concentrations were observed with the Gm(f;n;b) haplotype. When compared with Gm(f;n;b) negative individuals, Gm(f;n;b) positives had significantly higher concentrations of total IgG2 (p less than 0.001) and IgG2 anti A-CHO (p less than 0.05), lower concentrations of total IgG1 (p less than 0.001) and IgG1 anti A-CHO (p less than 0.001), and lower concentrations of total IgM (p less than 0.001) and IgM anti A-CHO (p less than 0.05). We conclude that individuals with the Gm(f;n;b) haplotype respond preferentially with IgG2 rather than IgG1 subclass antibodies. This increased capacity to respond with IgG2 antibodies may be reflected in the magnitude of the total antibody response when the IgG2 subclass comprises a major proportion of the response, as occurs in the adult response to many polysaccharide Ag.

Adult↗
PubMed1988

Selective defect in the antibody response to Haemophilus influenzae type b in children with recurrent infections and normal serum IgG subclass levels.

We studied 15 children with recurrent infections and normal serum IgG, IgM, IgA, and IgG-subclass levels. After immunization, the geometric mean serum IgG antibody concentration to Haemophilus influenzae type b (Hib) was eightfold lower than that of age-matched control subjects (p = 0.002). The patients also had a lower geometric mean concentration of serum IgM and IgA directed to Hib, although these differences did not reach significance. However, the groups did not differ in their response to diphtheria toxoid and pneumococcal polysaccharides. To confirm these findings, an additional 11 patients were identified and immunized. The geometric mean serum IgG anti-Hib concentration for this group of patients was also significantly lower than of normal subjects (p = 0.004). We propose that the defect in the antibody response to Hib may be a marker for a poor antibody response to a variety of bacterial and viral antigens that results in an increased propensity to recurrent infections. The defect was not associated with IgG-subclass deficiency. The identification of children with selective antibody deficiency and recurrent infections is important for diagnostic and therapeutic reasons.

Adolescent↗
PubMed1988

Postvaccination susceptibility to invasive Haemophilus influenzae type b disease in infant rats.

To evaluate the possibility that immunization with a capsular polysaccharide vaccine decreases immunity in the immediate postvaccination period and renders an animal susceptible to invasive Haemophilus influenzae type b disease, we passively immunized infant rat pups with an immune globulin preparation, vaccinated them with an H. Influenzae type b capsular polysaccharide vaccine at a wide range of doses, and challenged them with H. influenzae type b given intraperitoneally. Bacteremia occurred in 89% of protected, vaccinated pups compared with 17% of protected, unvaccinated pups (p = 0.0001). In protected, vaccinated pups the rate of bacteremia resembled that in unprotected, unvaccinated control pups and did not vary with the dose of vaccine administered. The magnitude of bacteremia and the incidence of meningitis in protected, vaccinated pups exceeded that occurring in the protected, unvaccinated control animals, but these effects diminished with the dose of vaccine. Diminution of anticapsular antibody occurred in association with the largest doses of vaccine. We conclude (1) that the administration of H. influenzae type b capsular polysaccharide vaccine in infant rats is associated with a diminution of passively acquired anticapsular antibody immediately after vaccination and (2) that experimental challenge with H. influenzae type b at this time produces disease resembling that in animals not passively given protection.

Animals↗
PubMed1988

Gentamicin penetration into cerebrospinal fluid in experimental Haemophilus influenzae meningitis.

We studied the effect of meningitis and the method of parenteral gentamicin administration (intramuscular injection, a 30-min intravenous infusion, or intravenous bolus administration) on achievable concentrations of drug in cerebrospinal fluid (CSF). In normal animals, only intravenous bolus administration of 2 to 8 mg/kg produced a gentamicin concentration of greater than 0.1 microgram/ml in CSF in some animals. All CSF samples contained less than the limit of detection (0.1 microgram/ml) after the intramuscular administration of 6 mg/kg. In animals with meningitis, gentamicin penetration into cisternal CSF was increased significantly after a bolus administration of 6 mg/kg (mean, 0.197 +/- 0.063 microgram/ml in normal animals versus 1.68 +/- 0.38 micrograms/ml in animals with meningitis; P less than 0.01). In meningitic animals that received 6 mg/kg as an intravenous bolus, lumbar CSF had the highest maximum concentration (4.25 +/- 1.08 micrograms/ml), in comparison with ventricular CSF (3.10 +/- 0.66 micrograms/ml). The gentamicin concentration in cisternal CSF decreased more slowly than it did in serum (elimination half-life, 238.70 +/- 64.56 min in cisternal CSF versus 82.73 +/- 2.91 min in serum), yielding a relative increase in the percentage of penetration. We conclude that maximum penetration by gentamicin into CSF occurs after intravenous bolus administration and that the maximum concentration occurs in lumbar CSF.

Animals↗
PubMed1988

Prevention of pneumococcal otitis media in chinchillas with human bacterial polysaccharide immune globulin.

Clinical and experimental observations suggest that immune globulin may prevent otitis media (OM) in children. We performed experiments in chinchillas to test the hypothesis that human bacterial polysaccharide immune globulin (BPIG) might prevent OM caused by Streptococcus pneumoniae. Animals were given BPIG or saline intraperitoneally on day 0. On day 3 the epitympanic bulla was inoculated with S. pneumoniae type 7F. All 12 saline-treated and none of 12 BPIG-treated animals developed pneumococcal OM by day 7 (P less than 0.0001). Bacteremia developed in 6 of 12 saline- and 0 of 12 BPIG-treated animals (P = 0.007). Death with pneumococcal OM occurred within 28 days in 5 of 12 saline- and 0 of 12 BPIG-injected animals (P = 0.02). A chinchilla-specific immunoassay was used to show that surviving saline-injected animals developed serum anticapsular antibody; BPIG-treated animals had no detectable response. At levels of anticapsular immunoglobulin G similar to those of human adults, BPIG given systemically prevented pneumococcal OM and disseminated infection in chinchillas. BPIG may be of value in preventing human bacterial infection and may also inhibit development of antibody if it affects local infection or colonization. Specific immunoglobulin G antibody may provide an important antibacterial defense of mucosal surfaces of the respiratory tract.

Animals↗
PubMed1987

Haemophilus influenzae type b unsuspected bacteremia.

To further define the clinical features and natural history of unsuspected Haemophilus influenzae type b (Hib) bacteremia, we retrospectively reviewed the records of 322 Hib infections observed during a 45-month period at Children's Hospital, Boston. We identified 31 patients with unsuspected Hib bacteremia and 19 with unsuspected Hib antigenemia and sterile blood cultures. Bacteremic patients were typically under two years of age (81%), had high fevers (mean = 39.5 degrees C), and frequently had otitis media (65%) diagnosed as their only focus of infection at presentation. Nineteen of 31 were empirically treated with oral antibiotics. Ten of 31 (32%) developed focal infectious complications consisting of meningitis (n = 7), cellulitis (n = 2), and pneumonia (n = 1). Children with focal infectious complications differed from those without infectious complications in having a significantly higher mean fever of 40.3 degrees C compared to 39.7 degrees C (P less than 0.05). Five of 19 (26%) empirically treated patients developed focal complications (all meningitis) compared to five of 12 (42%) untreated patients. Blood cultures at follow-up visit were positive in three of 19 (9%) treated patients and seven of 12 (42%) untreated patients (P less than 0.05). Of the 19 children with antigenemia and sterile blood cultures, 16 (84%) were empirically treated with antibiotics, and none had positive blood cultures or focal infections on follow-up evaluation. Children with occult Hib bacteremia are at high risk for developing serious focal infections, particularly meningitis, despite empiric antibiotic therapy. Once Hib bacteremia is suspected, strong consideration should be given to parenteral in hospital antibiotic therapy. The utility of rapid antigen detection for identifying high-risk patients requires further evaluation.

Antigens, Bacterial↗
PubMed1987

Effect of complement depletion on anticapsular-antibody-mediated immunity to experimental infection with Haemophilus influenzae type b.

Antibody to the capsular polysaccharide of Haemophilus influenzae type b (Hib) was not protective in infant rats depleted of complement by cobra venom factor (CoVF) even when serum antibody levels were many times the minimum protective level. Partial protection from Hib infection was achieved in CoVF-treated rats only if they were passively hyperimmunized with large doses of immunoglobulin G Hib capsular polysaccharide antibody. In addition, nonimmune CoVF-treated rats had higher mortality and blood bacterial density than nonimmune rats with intact complement systems.

Animals↗
PubMed1987

Endotoxin neutralization with rabbit antisera to Escherichia coli J5 and other gram-negative bacteria.

To study the mechanisms of protection against endotoxin challenge offered by antisera to smooth and rough gram-negative organisms, we have developed an assay to quantitate endotoxin neutralization based on inhibition of the Limulus amoebocyte lysate test. Dilutions of different bacterial lipopolysaccharides (LPSs) were incubated with hyperimmune rabbit sera against Escherichia coli O113, E. coli O18, and rough mutants E. coli J5 and Salmonella minnesota Re595 and were then combined with limulus lysate. The gelation reaction induced by LPS in the lysate was monitored spectrophotometrically, and the concentration of LPS resulting in a 50% lysate response was determined and correlated with antibody titers measured by enzyme-linked immunosorbent assay. Antisera to smooth organisms neutralized homologous LPS markedly and heterologous LPSs only minimally relative to neutralization by preimmune serum. Neutralization of homologous LPS occurred immediately without preincubation of serum and LPS. Antisera to rough mutants neutralized more heterologous LPS than did antisera to smooth organisms. However, this heterologous neutralization required preincubation of serum and LPS and did not appear to be correlated with antibody concentrations. We conclude that antisera to LPS rapidly neutralize the biological activity of the homologous LPS, as detected by limulus lysate, and that neutralization is at least in part antibody mediated. Antisera to rough-mutant organisms slowly neutralized the activity of heterologous LPSs, but this effect appeared not to be correlated with concentrations of antibody to the LPS of the rough mutant, as measured by enzyme-linked immunosorbent assay.

Animals↗
PubMed1986

Passive immunization against disease due to Haemophilus influenzae type b: concentrations of antibody to capsular polysaccharide in high-risk children.

From the pooled plasma of 54 adult donors immunized with Haemophilus influenzae type b capsular polysaccharide (CP), a human hyperimmune globulin termed bacterial polysaccharide immune globulin (BPIG) was prepared. The pharmacokinetics of antibody to H. influenzae type b CP in high-risk children was compared after BPIG and conventional immune serum globulin (ISG) were administered intramuscularly at a dose of 0.5-0.6 ml/kg. The increase in antibody level four to seven days after injection was ninefold higher with BPIG than with ISG and remained higher throughout the three-month follow-up period. The mean half-life of antibody to H. influenzae type b CP was similar after BPIG (27 days) and ISG (29 days). Antibody levels returned to baseline one to two months after ISG but remained significantly above baseline three months after BPIG (mean concentration, 385 ng/ml). Based on the assumption that 150 ng of IgG antibody to H. influenzae type b CP/ml is the minimal protective level, it is concluded that a single intramuscular dose of 0.5 ml of BPIG/kg will protect children for four months.

Anemia, Sickle Cell↗
PubMed1986

Functional characterization of human IgG, IgM, and IgA antibody directed to the capsule of Haemophilus influenzae type b.

Antibody to the capsular polysaccharide (CP) of Haemophilus influenzae b (Hib) is bactericidal, opsonic, and protective. Minimum protective levels of primarily IgG antibody to Hib CP, calculated from passive immunization studies, have been found to be approximately .06-.15 microgram/ml of serum. The human response to antigenic challenge with the Hib capsule, however, includes production of antibody to Hib CP of different isotypes whose function against Hib is unclear. In order to characterize the function of antibody to Hib CP of different isotypes, we purified human IgG, IgM, and IgA from the serum of an adult donor who had been previously immunized with purified Hib CP vaccine. The globulin preparations were greater than 99% isotypically pure, contained large quantities of anticapsular antibody, and differed in function against Hib. IgG antibody to Hib CP was bactericidal and opsonic for human polymorphonuclear leukocytes (PMNLs) in the presence of complement and protective in infant rats. IgM, although more bactericidal than IgG (P less than .01) and equally protective in rats, opsonized Hib poorly for PMNLs. IgA was not bactericidal or opsonic and did not prevent bacteremia and meningitis in rats challenged with Hib. We conclude that antibody directed against the capsule of Hib differs in antibacterial function depending on class. These data may be important to acurately estimate minimum protective levels of anticapsular antibody after vaccination or natural infection and may have implications for the manner in which the host clears Hib from the circulation.

Animals↗
PubMed1986

Neutralization and lipoprotein binding of lipopolysaccharides in tolerant rabbit serum.

We examined the ability of sera drawn from rabbits made tolerant to lipopolysaccharide (LPS) from Escherichia coli O18 to inhibit heterologous LPS-induced gelation of Limulus lysate. Compared with a pool of pretolerant sera, a pool of tolerant sera from these rabbits neutralized 5.5-fold more LPS from Salmonella typhimurium, 4.9-fold more LPS from Pseudomonas aeruginosa, and 10.0-fold more LPS from Klebsiella pneumoniae. Because previous studies have found that LPS bound to lipoprotein is less toxic than unbound LPS, we also studied the binding of LPS lipoprotein fractions in the serum pools by using fractionation with a cesium chloride-equilibrium density gradient. Radiolabeled LPS from E. coli O113 bound much more rapidly to lipoprotein fractions in tolerant serum than in pretolerant serum (after 11 min of incubation, 66.1% vs. 16.5% binding, respectively).

Animals↗