Search PubMed⌕ Search

Biomedical subjects

K W Hunter

Publications and source records attributed to K W Hunter.

53 records · Page 3Linked to original sources
PubMed1982

Modified human immune serum globulin for intravenous administration: in vitro opsonic activity and in vivo protection against group B streptococcal disease in suckling rats.

Human immune serum globulin (ISG) preparations were tested in an in vivo suckling rat protection assay and an in vitro opsonophagocytic assay against various types and strains of Group B streptococci (GBS). Standard ISG provided minimal protection in suckling rats against type III GBS sepsis, whereas preparations of ISG modified for intravenous administration (MISG) provided significant protection against all strains of type III, type II and type Ia GBS tested. Although less protection was obtained against type Ia strains, the survival in suckling rats challenged with all types of GBS varied from 73% to 91% with MISG therapy, as compared with 5% to 12% survival in untreated animals. In this in vivo model, MISG was protective even when administered after bacterial challenge, but had to be administered within 5 h of infection. MISG also had high in vitro opsonic activity against GBS types III and II, but was less effective with some type Ia strains. Just as MISG was more protective than ISG in vivo, it also was more opsonic in vitro. A detailed comparison of one lot of MISG with its parent ISG revealed that the modified preparation actually contained less IgG. When equivalent concentrations of affinity-purified IgG from both preparations were tested, the IgG from MISG was significantly more opsonic. Since the affinity purification procedure eliminated the possibility that IgM or substances introduced in the modification process were actually responsible for the enhanced bactericidal activity, it appears that the individual IgG molecules in MISG may be more effective. These studies suggest that MISG which has been modified by reduction and alkylation for intravenous administration may provide a valuable adjunct to chemotherapy in the treatment of GBS disease in the neonate.

Animal Population Groups↗
PubMed1982

Murine malaria: blood clearance and organ sequestration of Plasmodium yoelii-infected erythrocytes.

This study examined the mechanisms of clearance of Plasmodium yoelii-infected erythrocytes (RBC) from the peripheral circulation of mice. Parasitized RBC labeled with 51Cr were cleared from the blood of normal C57BL/6 mice at a much more rapid rate than were nonparasitized RBC, and preincubation of parasitized RBC in antiplasmodial antibody failed to significantly enhance clearance. This apparent antibody-independent clearance mechanism was markedly abrogated by splenectomy, indicating a major role for the spleen in parasitized RBC clearance. Macrophage inactivation by silica treatment also impaired parasitized RBC clearance, but to a lesser extent than splenectomy. Although abrogation of phagocytic function by silica treatment had little effect on splenic sequestration of parasitized RBC, hepatic sequestration was significantly depressed. Schizont- and late trophozoite-infected RBC were rapidly removed from the circulation, whereas RBC containing rings and early trophozoites showed less clearance over time. These data are consistent with the hypothesis that the architecture of the spleen serves as a sieve to entrap RBC that contain malarial parasites, particularly the more mature developmental forms.

Animals↗
PubMed1982

Temperature-induced in vitro transformation of Leishmania mexicana. I. Ultrastructural comparison of culture-transformed and intracellular amastigotes.

Promastigotes of Leishmania mexicana growing exponentially in vitro at 26 degrees C in mammalian cell culture medium with 10% serum were transformed to amastigote-like forms by elevating the incubation temperature to 34 degrees C. During the first 24-48 h of the transformation process the slender flagellated promastigotes lost their flagella and became smaller and more ovoid. By 72 h, transformation was complete with greater than 95% of the parasites viable as judged by vital dye exclusion. Moreover, these newly transformed parasites were capable of infecting the macrophage-like tumor cell line P388D1, and could reconvert to the promastigote stage upon return to an incubation temperature of 26 degrees C. The transformed amastigote-like parasites survived only 3 days in culture even with daily renewal of the culture medium, possibly indicating the requirement for some factor or factors normally present in the intracellular milieu. Ultrastructural studies revealed the same gross changes observed under light microscopy, and also demonstrated a close similarity in cellular organelles and membrane structure between amastigotes within phagolysosomes of P388D1 and the culture-derived amastigote forms. By these biologic and morphologic criteria the transformed parasites appear to be amastigotes, though further biochemical studies are needed to confirm their strict analogy to intracellular forms. However, the temperature-induced transformation process itself should provide an excellent model system for studying the effects of environment on eukaryotic gene expression.

Animals↗
PubMed1981

Levamisole: potentiation of primary immunoglobulin M antibody responses in suckling rats.

The influence of levamisole (LMS) on the primary immunoglobulin M (IgM antibody response of suckling rats was investigated. Although suckling rats did make a direct plaque-forming cell (PFC) response to sheep red blood cells (SRBC), the magnitude of this response was much lower than that of adult rats. LMS treatment (2.5 mg/kg) markedly potentiated the anti-SRBC response in 10-day-old rats, but this enhanced PFC response never attained adult levels. In contrast, LMS failed to boost the anti-SRBC response of adult rats, although the adult response to suboptimal antigenic stimuli was enhanced. The ontogeny of immunological responsiveness to SRBC was not influenced by LMS; only existing responses could be modulated. The potentiating effect of LMS was dose-dependent, with high doses causing suppression. The influence of LMS did not involve the earlier appearance of PFC. Since LMS augmented the PFC response to SRBC when administered before or after antigen, it appears that both the inductive phase and the proliferative phase of antibody production can be modulated. Finally, the PFC responses to a more thymus-independent antigen (2,4,6-trinitrophenyl-Ficoll) was boosted, suggesting that LMS may be capable of directly influencing B lymphocytes. These findings indicate that the functional immunodeficiency of the neonatal antibody response can be improved by LMS treatment.

Adjuvants, Immunologic↗
PubMed1981

Hypergammaglobulinemia and erythrocyte autoantibody complicate enzyme immunoassay of antimalarial antibody.

Enzyme immunoassay of specific antimalarial antibody in sera from Plasmodium yoelii-infected mice was complicated by hypergammaglobulinemia and erythrocyte (RBC) autoantibody. Malarious serum had higher immunoglobulin levels which resulted in a substantial nonspecific adsorption of antibody to antigen uncoated microliter wells even in the presence of a surfactant. Since it was possible that some of the antibody binding to solid phase-bound malarial antigen was also due to nonspecific adsorption, the antibody binding of nonimmune serum was compared to that of malarial immune serum diluted to an equivalent immunoglobulin concentration. This allowed differentiation of specific antimalarial antibody binding from nonspecific adsorption of immunoglobulin. Although malarial antigen was partially purified from intraerythrocytic parasites, it bound a significant amount of rabbit anti-mouse RBC antibody, indicating the presence of residual RBC antigens. Serum from immune mice, but not nonimmune mouse serum, also showed substantial binding to RBC stroma antigen, suggesting that a component of the observed antibody binding to malarial antigen was anti-RBC antibody. Hypergammaglobulinemia and the induction of RBC autoantibody may both be related to the polyclonal activating property of the malaria infected mice necessitates a more conservative interpretation of specific antimalarial antibody levels until a more purified malarial antigen is available.

Animals↗
PubMed1981

Type III group B streptococcal strain differences in susceptibility to opsonization with human serum.

Human serum opsonins to type III Group B streptococci (GBS) were studied in an in vitro opsonophagocytic assay. Two type III GBS test strains were susceptible (893 and IIINor) and two resistant (891 and 892) to opsonization by the majority of sera from 15 healthy adults. Four individuals with undetectable or low opsonic titers to the test strains were immunized with pneumococcal vaccine; immunization with pneumococcal vaccine induced a titer rise in all but one instance when susceptible GBS strains were tested. In contrast, only a single titer rise was detected when resistant GBS strains were employed in the test. These results indicate that immunization with a cross-reacting antigen (identical to core antigen of type III GBS) fails to induce opsonic antibody to all strains of type III GBS. A resistant strain was made highly susceptible to neutrophil killing in vitro by exposure to neuramindase prior to incubation with opsonic serum. Using a fluorescent lectin-binding assay, this enzyme appeared to remove surface sialic acid, suggesting that sialic acid is an antiphagocytic factor. However, the possibility that other surface moieties may act as antiphagocytic factors cannot be ruled out. Both opsonic susceptible and resistant strains absorbed opsonic antibody from serum, which suggests that the GBS antiphagocytic factors do not prevent binding of antibody to resistant bacteria. These findings indicate that demonstration of serum opsonic activity to one strain of type III GBS may not accurately depict opsonic activity to other strains. In addition, immunization with core antigen did not enhance opsonic activity against all GBS strains. These data also point out the need to use assays which measure functional antibody, since demonstration of antibody binding may not reflect its ability to facilitate bacterial phagocytosis and killing.

Adult↗
PubMed1980

Diminished bacterial defences with intralipid.

'Intralipid', a lipid emulsion used in parenteral nutrition, impaired bacterial clearance and enhanced bacterial virulence in mice. In addition it inhibited the chemotaxis of human neutrophils in vitro. Intralipid may enhance the risk of bacterial sepsis in certain patients.

Animals↗
PubMed1980

Decreased phytohemagglutinin-induced aggregation and C5a-induced chemotaxis of human newborn neutrophils.

Phytohemmagglutinin (PHA)-induced lectin aggregation, chemotactic response to C5a, and random migration were measured on paired samples of neutrophils obtained from human peripheral blood and cord blood of normal newborn infants. The mean aggregation rate (+/- 1 SD) of adult neutrophils with PHA was 16.8 +/- 4.4 vs. 12.0 +/- 3.6 for newborn neutrophils (P less than 0.005), and the mean percent aggregation of adult neutrophils was 56.2 +/- 9.2 vs. 45.6 +/- 8.3 for newborn neutrophils (P less than 0.005). Exposure to newborn plasma had no affect on adult neutrophil aggregation. Whereas vinblastine (VBL) decreased both the percent and rate of PHA-induced adult neutrophil aggregation, only the rate of newborn neutrophil aggregation was reduced by VBL. Newborn neutrophil chemotactic response to C5a, was reduced by 80% (P less than 0.0025), and showed a positive correlation with percent PHA-induced aggregation (r = 0.6037, P less than 0.05). On the other hand, random migration was not significantly reduced and did not correlate with PHA-induced aggregation. These observations suggest that the decreased chemotactic responsiveness of newborn neutrophils may be due to developmental membrane differences which adversely affect the number and/or availability of C5a resceptors. Lectin-induced aggregation studies of other chemotactic defects may identify similar differences.

Cell Aggregation↗
PubMed1979

Serum opsonic activity in rodent malaria: functional and immunochemical characteristics in vitro.

The functional and immunochemical characteristics of serum opsonic activity in rodent malaria were examined in the present study. Schizont- and late trophozoite-enriched populations of Plasmodium berghei-infected red blood cells (IRBC) were isolated on a Ficoll density-gradient and used in an in vitro phagocytosis system composed of serum and monolayer cultures of rat peritoneal macrophages. Hyperimmune serum augmented the phagocytosis of IRBC to a greater degree than did nonimmune serum. When either IRBC or macrophages were pre-incubated with serum, the phagocytosis-promoting factors acted on the IRBC rather than on the macrophages in a manner characteristic of serum opsonins. The opsonic activity was specific for IRBC since noninfected red blood cells were rarely phagocytized and were unable to absorb opsonic activity from serum. The opsonic activity of both hyperimmune and nonimmune sera was heat stable, and unaffected by agents known to inactivate or inhibit complement (cobra venom factor and ethylenediaminetetraacetic acid). Finally, the opsonic activity was identified in preparations of purified IgG isolated from both hyperimmune and nonimmune sera.

Animals↗
PubMed1979

Defective resistance to Plasmodium yoelii in CBA/N mice.

The role of B lymphocytes in resistance to malaria was studied in defective and normal F1 mice derived from CBA/N mice, a strain with an X-linked B cell defect. When infected with normally nonlethal Plasmodium yoelii, immune defective F1 male mice had higher parasitemias and more prolonged infections than normal F1 mice, as well as a 50% mortality rate. Before infection the plasma levels of IgM and IgG were lower in defective F1 males than normal F1 mice. The polyclonal IgM and IgG responses of infected abnormal F1 mice were delayed and lower in absolute magnitude than those of normal F1 mice. Furthermore, specific IgM and IgG anti-plasmodial antibody titers, as determined by radioimmunoassay, were depressed on day 12 in the defective F1 males. Although IgG titers approached those of the normal F1 mice on day 19, defective F1 male IgM titers remained depressed. These data demonstrate that an X-linked gene that affects B cell function influences malarial resistance in mice, presumably via a decreased specific IgM response, and the slow development of a specific IgG response to P. yoelii infection.

Animals↗
PubMedDate not supplied

Intravenous immunoglobulin in the treatment of neonatal sepsis: therapeutic strategies and laboratory studies.

IGIV appears to have a promising future in treating and perhaps preventing neonatal bacterial infections. However, all IGIV lots do not contain equal amounts of pathogen-specific IgG with functional opsonic activity. To ensure effective therapy it will be important to inform physicians that the IGIV lots available for use contain functional antibacterial antibody to the responsible pathogens. To optimize therapy IGIV may need to be given early in the infection and doses may need to be repeated if pathogen-specific antibody is rapidly depleted. Further, clinical studies will be necessary to determine if IGIV will be a valuable adjunct to antibiotic therapy in neonatal GBS infections.

Animals↗