Bordetella pertussis Filamentous Hemagglutinin Enhances the Immunogenicity of Liposome-Delivered Antigen Administered Intranasally

In an attempt to increase the immunogenicity of mucosally delivered antigens, we incorporated the Bordetella pertussis filamentous hemagglutinin (FHA) adhesin into liposomes containing the glutathione S-transferase of Schistosoma mansoni (Sm28GST) as a model antigen. Outbred mice immunized twice intranasally with liposomes containing a constant suboptimal dose of Sm28GST and increasing doses of FHA produced anti-Sm28GST antibodies in a FHA dose-dependent manner. The addition of 3 μg of FHA to the liposomes induced more than 10-fold-higher anti-Sm28GST antibody titers, compared to those induced by liposomes without FHA. The presence of FHA did not alter the nature of the humoral immune response, and the sera contained anti-Sm28GST immunoglobulin G1 (IgG1), IgG2a, and IgG2b. However, anti-Sm28GST IgA was only detected when at least 3 μg of FHA was added to the preparation. These results show a promising potential for FHA to enhance the immunogenicity of mucosally administered antigens incorporated into liposomes.     

Reconstitution of B-cell-depleted mice with B cells restores Th2-type immune responses during Plasmodium chabaudi chabaudi infection.

In mice depleted of B cells from birth by treatment with anti-immunoglobulin M(mu) antibodies, progression from a Th1- to a Th2-regulated immune response during primary infection with Plasmodium chabaudi chabaudi fails to occur. While Th1-type immunity limits parasitemia, in the absence of B cells, chronic low-grade infections persist. Here, we show that reconstituting immune, and to a lesser extent naive, B cells to mice rendered deficient in B-cell function through anti-immunoglobulin M(mu) pretreatment restores the CD4+ T-cell response to the Th2 type later in P. c. chabaudi infection and with it the capacity to eliminate infection. This finding provides clear evidence that B cells are required for switching the balance of immune regulation between CD4+ T cells from Th1 to Th2 during P.c. chabaudi infection and supports the concept that B cells, through antibody production, are needed for effective antimalarial immunity.     

Neuronal histamine in the gut wall releasable by gastrin and cholecystokinin

Histamine accumulated in the ligated vagus nerve of the rat, both above and below the ligature; maximum accumulation was after 4 h. The finding is suggestive of axonal flow. Further evidence for histamine in peripheral nerves was obtained in experiments showing that the guinea-pig gut wall could be labelled with [3H]histamine. The experiments were carried out with isolated strips of stomach wall and taenia coli. Electrical stimulation released [3H]histamine from these specimens. The release could be blocked by Ca2+-free medium or by tetrodotoxin. The release was unaffected by vagal denervation or chemical sympathectomy (6-hydroxydopamine) but prevented by reserpinization. Gastrin-17 and cholecystokinin-39 released radioactivity by a tetrodotoxin-sensitive mechanism. The possible existence of a gastrin/cholecystokinin-sensitive neuronal pool of histamine in the gut wall offers a new perspective on the postulated role of histamine as a physiological stimulant of gastric acid secretion and might explain why H2-receptor antagonists block gastrin-stimulated acid secretion.     

Appraisal in the diagnostic laboratory of three commercially available anaerobic cabinets

Three commercially available anaerobic cabinets are described and their performance in relation to one another and to a standard anaerobic jar technique are reported upon from a clinical laboratory.     

Unit activity in posterior association cortex of cat.

1. "Association" neurons in the posterior middle suprasylvian gyrus of cat were found to be predominantly polysensory, with 82% of the units in the chloralose-anesthetized preparation responding to auditory, visual, and somatic stimuli. There was no evidence of response differentiation associated with cortical depth distribution. Most units responded with a short-latency response (median 35-60 ms) to all stimulus modalities, with the response to visual stimulation occurring at the shortest latency. Among polysensory cells, almost half responded with equal probability to auditory, visual, and somatic stimulation. The visual stimulus was the most potent for those cells responding with a higher probability to a single modality. Varying degrees of response complexity were noted in some cells in terms of changes in responsivity over time, discharge to stimulus offset, and inhibition of spontaneous activity. The unitary discharge was seen to occur on the negative peak and slope of the locally recorded evoked potential. When only the larger amplitude spikes were analyzed, most of the unitary activity occurred on the negative peak of the evoked potential. Almost half of trimodally responsive cells displayed similar phase relationships between unitary activity and evoked potentials for all three modalities. The absolute refractory period for most cells was from 200 to 300 ms, with relative refractory periods extending up to 30 s...     

Intimin from enteropathogenic Escherichia coli restores murine virulence to a Citrobacter rodentium eaeA mutant: induction of an immunoglobulin A response to intimin and EspB.

The formation of attaching and effacing (A/E) lesions is central to the pathogenesis of enteropathogenic Escherichia coli (EPEC)-mediated disease in humans and Citrobacter rodentium (formerly C. freundii biotype 4280)-mediated transmissible colonic hyperplasia in mice. Closely related outer membrane proteins, known as intimins, are required for formation of the A/E lesion by both EPEC (Int(EPEC)) and C. rodentium (Int(CR)). A secreted protein, EspB (formally EaeB), is also necessary for A/E-lesion formation. Here we report that expression of a cloned Int(EPEC), encoded by plasmid pCVD438, restores murine virulence to an intimin-deficient mutant of C. rodentium DBS255. Replacement of Cys937 with Ala abolished the ability of the cloned EPEC intimin to complement the deletion mutation in DBS255. Ultrastructural examination of tissues from wild-type C. rodentium and DBS255(pCVD438)-infected mice revealed multiple A/E lesion on infected cells and loss of contact between enterocytes and basement membrane. Histological investigation showed that although both wild-type C. rodentium and DBS255(pCVD438) colonized the descending colon and induced colonic hyperplasia in orally infected 21-day-old mice, the latter strain adhered to epithelial cells located deeper within crypts. Nonetheless, infection with the wild-type strain was consistently more virulent, as indicated by a higher mortality rate. All the surviving mice, challenged with either wild-type C. rodentium or DBS255(pCVD438), developed a mucosal immunoglobulin A response to intimin and EspB. These results show that C. rodentium infection provides a relevant, simple, and economic model to investigate the role of EPEC proteins in the formation of A/E lesions in vivo and in intestinal disease.     

Cloning and Sequencing of a Candida albicans Catalase Gene and Effects of Disruption of This Gene

Catalase plays a key role as an antioxidant, protecting aerobic organisms from the toxic effects of hydrogen peroxide, and in some cases has been postulated to be a virulence factor. To help elucidate the function of catalase in Candida albicans, a single C. albicans-derived catalase gene, designated CAT1, was isolated and cloned. Degenerate PCR primers based on highly conserved areas of other fungal catalase genes were used to amplify a 411-bp product from genomic DNA of C. albicans ATCC 10261. By using this product as a probe, catalase clones were isolated from genomic libraries of C. albicans. Nucleotide sequence analysis revealed an open reading frame encoding a protein of 487 amino acid residues. Construction of a CAT1-deficient mutant was achieved by using the Ura-blaster technique for sequential disruption of multiple alleles by integrative transformation using URA3 as a selectable marker. Resulting mutants exhibited normal morphology and comparable growth rates of both yeast and mycelial forms. Enzymatic analysis revealed an abundance of catalase in the wild-type strain but decreasing catalase activity in heterozygous mutants and no detectable catalase in a homozygous null mutant. In vitro assays showed the mutant strains to be more sensitive to damage by both neutrophils and concentrations of exogenous peroxide that were sublethal for the parental strain. Compared to the parental strain, the homozygous null mutant strain was far less virulent for mice in an intravenous infection model of disseminated candidiasis. Definitive linkage of CAT1 with virulence would require restoration of activity by reintroduction of the gene into mutants. However, initial results in mice, taken together with the enhanced susceptibility of catalase-deficient hyphae to damage by human neutrophils, suggest that catalase may enhance the pathogenicity of C. albicans.     

Contribution of histamine and prostanoids to bronchoconstriction provoked by inhaled bradykinin in atopic asthma

Bradykinin, a nonapeptide cleavage product of high molecular weight kininogen, is a potent bronchoconstrictor agonist in asthma; however, its mechanism of action is not known. Since bradykinin has been shown to stimulate mediator release from mast cells and augment the release of prostanoids, we have examined the effect of a selective histamine H1 receptor antagonist, terfenadine and a potent cyclooxygenase inhibitor, flurbiprofen on bronchoconstriction provoked by inhaled bradykinin in asthma. As a bronchial provocation procedure bradykinin challenge was repeatable to within 1 doubling dilution. In nine atopic asthmatic subjects, terfenadine 180 mg, when compared to placebo, increased the geometric mean provocation concentration of inhaled agonist required to reduce FEV1 by 20% of baseline (PC20) from 0.7 to greater than 22.9 mg/ml for histamine (P less than 0.01) and 0.3 to 0.5 mg/ml for bradykinin (P less than 0.01). In a further nine atopic asthmatics, flurbiprofen 150 mg when compared to placebo produced a small but significant protection of the airways against bradykinin, geometric mean PC20 increasing from 0.40 to 0.79 mg/ml (P less than 0.05). We conclude that bradykinin is a potent bronchoconstrictor agonist in asthma, being approximately 9.5 times more potent than histamine in molar terms. Pharmacological intervention with terfenadine and flurbiprofen led to a significant protection of the airways against the constrictor effect of bradykinin but the effect in each case was small. Thus, while histamine and prostanoids may contribute as mediators of bradykinin-induced bronchoconstriction, they are unlikely to account for the majority of the response.