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Biomedical subjects

F L Lyon

Publications and source records attributed to F L Lyon.

9 recordsLinked to original sources
PubMed1988

Adjuvant activity of Escherichia coli heat-labile enterotoxin and effect on the induction of oral tolerance in mice to unrelated protein antigens.

The ability of Escherichia coli heat-labile enterotoxin (LT) to influence the induction and maintenance of tolerance was examined in animals primed orally with a soluble protein antigen, ovalbumin (OVA), or in animals primed orally with two unrelated protein antigens administered simultaneously, OVA and bovine serum albumin (BSA). LT is immunologically and structurally related to the cholera enterotoxin (CT), which has been shown to be capable of abrogating oral tolerance to protein antigens when delivered simultaneously with the antigens. In this study, simultaneous administration of LT with OVA was shown to prevent the induction of tolerance to OVA and to increase the serum anti-OVA IgG response 30- to 90-fold over OVA-primed and PBS-primed animals, respectively. This effect was determined to be a function of the enzymatically active A subunit of the toxin since the B (binding) subunit alone was unable to influence tolerance induction. Animals fed LT with OVA after the initial OVA prime developed a significantly lower serum IgG and mucosal IgA anti-OVA response than those fed LT with OVA in the initial immunization, indicating that prior exposure to the antigen reduces the effectiveness of LT to influence tolerance and its ability to act as an adjuvant. LT was not able to abrogate tolerance once it had been established. Serum IgG and mucosal IgA responses in animals receiving LT on only a single occasion, that being upon first exposure to antigen, were equivalent to responses after three OVA/LT primes, indicating that commitment to responsiveness occurs early and upon first exposure to antigen.(ABSTRACT TRUNCATED AT 250 WORDS)

Adjuvants, Immunologic↗
PubMed1987

Basidiospore allergens: determination of optimal extraction methods.

Five methods were tested by RAST for allergen extraction from seven basidiospore species Armillaria tabescens, Chlorophyllum molybdites, Coprinus quadrifidus, Pleurotus ostreatus, Calvatia cyathiformis, Pisolithus tinctorius, and Scleroderma sp. With each basidiospore type, extracted allergen activity varied according to the method employed. In general, defatting of spores with ethyl ether, followed by homogenization in 0.125 M NH4HCO3 buffer, resulted in greatest allergen yield. In order to compare extracts from different isolates, batches of Pleurotus ostreatus spores obtained from different locations and over different time periods were analysed. Spores harvested from the same basidiomycete species in different areas varied in allergen (RAST) and protein (HPLC profile) content. The spores obtained from the same location over a 1-2 year period did not differ significantly. These results indicate that basidiospores can be stored for several years and that spore extracts from different locations can vary. These studies will help in the future to provide better characterized extracts for clinical studies.

Allergens↗
PubMed1986

Innate and acquired immune responses against Candida albicans in congenic B10.D2 mice with deficiency of the C5 complement component.

Congenic mice, sufficient or deficient with respect to the C5 component of complement, were evaluated for their innate and acquired immune responses to Candida albicans. When unimmunized mice were challenged intravenously and sacrificed at intervals for cultural analyses of kidneys, it was clear that C5-sufficient mice were able to deal more effectively with C. albicans during the first week after challenge than C5-deficient mice. When immunized mice were challenged intravenously to assess the development of protective responses, an intact complement cascade appeared to contribute to the more rapid clearance of fungi during the first few weeks following challenge, but by the fourth week after challenge, the numbers of fungi had decreased significantly in both types of mice and were at levels which were not significantly different. No significant differences were detected in the development of delayed hypersensitivity or Candida-specific antibody between C5-sufficient and C5-deficient mice either. C5-deficient mice did have slightly elevated levels over the C5+ mice, but this may simply reflect the prolonged antigenic load during the first 3 weeks following intravenous challenge in both immune and nonimmune animals. The later-acting complement components, while appearing to contribute to the early inhibition of the growth of C. albicans in the nonimmune animal, had no adverse effect on the development of specific immune responses, in that delayed hypersensitive responses were equivalent between the two groups, antibody response was not significantly altered and the ultimate outcome of challenge in immunized animals was not affected.

Animals↗
PubMed1986

Oral immunization of mice with attenuated Salmonella enteritidis containing a recombinant plasmid which codes for production of the B subunit of heat-labile Escherichia coli enterotoxin.

We used Salmonella enteritidis serotype dublin strain SL1438, a nonreverting, aromatic-dependent, histidine-requiring mutant, as a recipient for a recombinant plasmid coding for production of the nontoxic B subunit of the heat-labile Escherichia coli enterotoxin. The S. enteritidis derivative EL23 produced heat-labile enterotoxin subunit B that was indistinguishable from heat-labile enterotoxin subunit B produced by strains of E. coli or Salmonella typhi harboring the same plasmid. Mice immunized orally with strain EL23 developed progressively increasing mucosal and serum antibody responses to both heat-labile enterotoxin subunit B and to the lipopolysaccharide of the vaccine strain. The mucosal antibody response was shown to be immunoglobulin A specific and to be capable of neutralizing the biological activities of both E. coli heat-labile enterotoxin and cholera enterotoxin in vitro.

Administration, Oral↗
PubMed1985

Chemical and enzymatic variation in the cell walls of pathogenic Candida species.

Cell walls, isolated from seven pathogenic species of Candida, were lipid extracted and fractionated by treatment with ethylenediamine or enzymatically hydrolyzed using chitinase and laminarinase. Two different chitinase preparations were used, one from Streptomyces sp. which had some beta-1,3-glucanase activity, and another from Serratia marcescens which did not have glucanase activity. Laminarinase was a commercial preparation. The monosaccharide constituents of whole cell walls and the fractions derived from them were determined qualitatively and quantitatively by gas-liquid chromatography of the products of a mild acid hydrolysis and by the phenol - sulfuric acid assay of the products of a stronger acid hydrolysis. The monomeric constituents of the enzymatic hydrolyses were analyzed using gas-liquid chromatography. Approximately 50% of all walls was soluble in ethylenediamine. Glucose and mannose were the only monosaccharides found in all of the fractions derived from ethylenediamine extraction examined. Similarities among the strains, based upon relative amounts of glucose and mannose, were more apparent than differences, but statistical analyses of the data revealed a general trend of decreasing similarity in the following order, C. albicans and C. stellatoidea, C. tropicalis and C. parapsilosis, and C. pseudotropicalis, C. guilliermondii, and C. krusei. In the enzymatic assays, mannose and glucose were released by laminarinase, whereas glucose and N-acetyl-D-glucosamine or N-acetyl-D-glucosamine alone were released by the chitinases. These assays supported the trend in relationships cited above, with the data being somewhat more definitive.

Acetylglucosamine↗
PubMed1983

Cellular immunity in a cutaneous model of cryptococcosis.

The temporal development of cellular immune responses in mice inoculated cutaneously with viable Cryptococcus neoformans 145 was determined in vivo and in vitro by comparing several antigen preparations for their efficacy in the assays selected. Three antigens derived from C. neoformans 145, viz., a culture filtrate preparation (CneF-145), a membrane extract (B-HEX), and soluble cytoplasmic substances (SCS), were compared for their ability to detect delayed hypersensitivity (DH) in vivo in a footpad assay or to stimulate lymphocytes in vitro in a thymidine incorporation assay. DH to B-HEX could be demonstrated as early as 1 week after infection, whereas significant responses to SCS and CneF-145 were not regularly detected until 3 weeks after infection. Substantial reactions were observed to all three antigens up to 12 weeks, although they peaked at 2 to 3 weeks. Reactions to B-HEX and SCS were somewhat better than those to CneF. Differences in the efficacies of the three antigens were not obvious after the sixth week of infection, however. In vitro, lymph node cells from infected animals were stimulated significantly with all three antigens beginning at week 1. As with DH, however, responses to CneF-145 were usually less than those to SCS and B-HEX. In vitro lymphocyte responses waned after approximately 6 weeks, whereas DH responses were clearly positive through 12 weeks. In addition to the studies in infected animals, animals immunized with heat-killed cells of C. neoformans 145 or 184 were tested 6 to 8 days later for DH with CneF-145, CneF-184, or B-HEX derived from C. neoformans 145. The CneF-145 and CneF-184 were equally effective for detecting DH, regardless of the cryptococcal strain used for immunization. Likewise, the B-HEX detected equivalent responses in mice sensitized with each cryptococcal strain. Since all three antigens were soluble and easily extracted and since each elicited significant cellular immune responses in infected animals, further studies involving their specificity and the nature of their reactive components seems warranted as they may help evaluate immune responses in humans infected with this fungus.

Animals↗
PubMed1982

Immunization of mice by intracutaneous inoculation with viable virulent Cryptococcus neoformans: immunological and histopathological parameters.

Immune responses, including protection and delayed hypersensitivity, were evaluated in experimental murine cryptococcosis. Mice were immunized by the intracutaneous inoculation of viable virulent Cryptococcus neoformans yeasts. Response to the cutaneous infection was evaluated histologically and by cultural assays of the internal organs, as well as by intravenous challenge with the same strain. Protection was assessed by survival, histopathology, and quantitative organ culture. The intracutaneous inoculation of cryptococci resulted in a local inflammatory response that effectively limited dissemination of the organisms systemically and induced the development of delayed hypersensitivity demonstrable with a membrane extract of C. neoformans and with soluble cytoplasmic substances. A protective response was induced by the cutaneous inoculation of cryptococci as well, in that immunized animals survived longer, with about 25% of the challenged group ridding themselves completely of the cryptococci. Protection could be demonstrated by cultural analyses, but all animals, whether control or immunized, allowed considerable multiplication of the inoculum during the first 4 weeks after intravenous challenge. It would appear, therefore, that the protective mechanism(s) required additional antigenic stimulation before it could eventually function to eliminate all cryptococci from tissues. Histologically, there were no differences in pathology of the internal organs between immunized and unimmunized animals. Although the model described herein for the induction of immune responses in murine cryptococcosis has at least one drawback, viz., the presence of cryptococci in the skin lesion of many animals throughout the duration of the experiment, it does have the advantage that the immune responses were stimulated by a virulent strain and only minimal dissemination occurred. Therefore, lymphocytes could be removed from animals that were not contaminated with cryptococci for in vitro and in vivo transfer.

Animals↗
PubMed1981

Immunological relatedness among Candida albicans and other pathogenic Candida species.

Membrane-mitochondrial (butanol-hot phosphate-buffered saline) and cytosol (soluble cytoplasmic substances) extracts from seven pathogenic species of Candida were used in in vivo and in vitro immunological assays to study antigenic similarities among the strains with respect to C. albicans. Mice were sensitized with C. albicans serotype A for footpad testing or to provide cells for lymphocyte stimulation assays, and guinea pigs were immunized with whole cells or butanol-hot phosphate-buffered saline extracts of C. albicans to obtain antisera for immunodiffusion assays. When extracts from each of the seven species were used in the assays, they consistently segregated, as determined by statistical or subjective analyses, into three groups. Extracts of C. albicans serotype A or B and C. stellatoidea were the most immunologically reactive in all assays, indicating close similarities between those two species, whereas extracts of C. tropicalis and C. parapsilosis elicited only moderate responses. Extracts from C. krusei, C. guilliermondii, and C. pseudotropicalis were hypo- or nonreactive in the assays, indicating a low level of antigenic relatedness to C. albicans.

Animals↗