PubMed Health⌕ Search

Biomedical subjects

C P Mallett

Publications and source records attributed to C P Mallett.

18 recordsLinked to original sources
PubMed2001

Safety and immunogenicity of a proteosome-Shigella flexneri 2a lipopolysaccharide vaccine administered intranasally to healthy adults.

We studied the safety and immunogenicity of a Shigella flexneri 2a vaccine comprising native S. flexneri 2a lipopolysaccharide (LPS) complexed to meningococcal outer membrane proteins-proteosomes-in normal, healthy adults. A two-dose series of immunizations was given by intranasal spray, and doses of 0.1, 0.4, 1.0, and 1.5 mg (based on protein) were studied in a dose-escalating design. The vaccine was generally well tolerated. The most common reactions included rhinorrhea and nasal stuffiness, which were clearly dose related (P < or = 0.05). These reactions were self-limited and generally mild. The vaccine elicited S. flexneri 2a LPS-specific immunoglobulin A (IgA), IgG, and IgM antibody-secreting cells (ASCs) in a dose-responsive manner. At doses of 1.0 or 1.5 mg, highly significant (P < 0.001) increases in ASCs of all antibody isotypes occurred and 95% of subjects had an ASC response in at least one antibody isotype. Dose-related serum antibody responses were observed, with geometric mean two- to fivefold rises in specific serum IgA and IgG titers and two- to threefold rises in IgM in the 1.0- and 1.5-mg-dose groups (P < 0.0001 for each isotype). Elevated serum antibody levels persisted through day 70. Increases in fecal IgG and IgA and also in urinary IgA specific for S. flexneri 2a LPS were demonstrated. These were most consistent and approached statistical significance (P = 0.02 to 0.12 for various measures) on day 70 after the first dose. The magnitude of immune responses to intranasally administered proteosome-S. flexneri 2a LPS vaccine is similar to those reported for live vaccine candidates associated with protective efficacy in human challenge models, and further evaluation of this product is warranted.

Administration, Intranasal↗
PubMed1998

Transcutaneous immunization with cholera toxin protects mice against lethal mucosal toxin challenge.

We recently reported that application of cholera toxin (CT) to the skin results in transcutaneous immunization and induces a systemic Ab response to both CT and coadministered Ags. In this paper, we demonstrate antitoxin IgG and IgA Abs in sera, lung washes, and stool samples from immunized mice as well as a broad spectrum of IgG subclasses (IgG1, IgG2a, IgG2b, and IgG3) in the sera. Mice immunized with CT by the transcutaneous route exhibited significant protection from intranasal challenge with a lethal dose of CT. Thus, clinically relevant immunity against mucosal toxin challenge can be achieved via the transcutaneous route.

Administration, Cutaneous↗
PubMed1998

Identification of epitope and surface-exposed domains of Shigella flexneri invasion plasmid antigen D (IpaD).

Transport and surface expression of the invasion plasmid antigens (Ipa proteins) is an essential trait in the pathogenicity of Shigella spp. In addition to the type III protein secretion system encoded by the mxi/spa loci on the large virulence plasmid, transport of IpaB and IpaC into the surrounding medium is modulated by IpaD. To characterize the structural topography of IpaD, the Geysen epitope-mapping system was used to identify epitopes recognized by surface-reactive monoclonal and polyclonal antibodies produced against purified recombinant IpaD or synthetic IpaD peptides. Surface-exposed epitopes of IpaD were confined to the first 180 amino acid residues, whereas epitopes in the carboxyl-terminal half were not exposed on the Shigella surface. By using convalescent-phase sera from 10 Shigella flexneri-infected monkeys, numerous epitopes were mapped within a surface-exposed region of IpaD between amino acid residues 14 and 77. Epitopes were also identified in the carboxyl-terminal half of IpaD with a few convalescent-phase sera. Comparison of IpaD epitope sequences with Salmonella SipD sequences indicated that very similar epitopes may exist in the carboxyl-terminal region of each protein whereas the IpaD epitopes in the surface-exposed amino-terminal region were unique for the Shigella protein. Although the IpaD and SipD homologs may play similar roles in transport, the dominant serum antibody response to IpaD is against the unique region of this protein exposed on the surface of the pathogen.

Animals↗
PubMed1997

Disassociation of oxidant-induced ATP depletion and DNA damage from early cytotoxicity in LLC-PK1 cells.

To determine the mechanism(s) of oxidant-mediated cell lysis in renal tubular epithelial cells, we determined ATP depletion, DNA damage, lipid peroxidation, and cytotoxicity in LLC-PK1 cells exposed to 500 microM hydrogen peroxide for 1 h with and without inhibitors of lipid peroxidation including a lazaroid compound, 2-methylaminochroman (2-MAC), and Trolox, a vitamin E analog. ATP levels were determined by luciferin-luciferase, DNA damage by the alkaline unwinding technique, lipid peroxidation by the generation of malondialdehyde, and early cytotoxicity (5 h) by the release of 51Cr, whereas late cytotoxicity (24 h) was determined by release of [3H]leucine from prelabeled cells. Cells exposed to 500 microM hydrogen peroxide demonstrated significant (P < 0.01) ATP depletion, DNA damage, and lipid peroxidation, followed by cell death at 5 h. Concentrations of 0.1-25 microM 2-MAC or 25-500 microM Trolox each markedly and significantly (P < 0.01) inhibited lipid peroxidation and early cytotoxicity but had little to no effect on ATP depletion or DNA damage. Thus oxidant-stressed cells remained intact for several hours despite significant ATP depletion and DNA damage when lipid peroxidation was inhibited with the antioxidant compounds. At 24 h, 2-MAG and Trolox had lost their protective effect, suggesting that mechanisms other than lipid peroxidation play a role in later cytotoxicity. We conclude that ATP depletion and DNA damage are not the primary mediators of early cytotoxicity following oxidant stress, whereas lipid peroxidation plays an central role in mediating early cytotoxicity following oxidant injury.

Adenosine Triphosphate↗
PubMed1995

Antibody and cytokine responses in a mouse pulmonary model of Shigella flexneri serotype 2a infection.

A murine pulmonary model was used to study the mucosal immune response to Shigella flexneri serotype 2a infection. Inoculation of BALB/cJ mice with shigellae via the intranasal route resulted in bacterial invasion of bronchial and alveolar epithelia with concomitant development of acute suppurative bronchiolitis and subsequent development of lethal pneumonia. The pathology of pulmonary lesions resembled the colitis that characterizes shigellosis in humans and primates. Significant protection against a lethal dose of S. flexneri 2a was observed in mice previously infected with two sublethal doses of the homologous strain. Immunity against lethal challenge was associated with decreased bacterial invasion of the mucosal epithelium. Over the course of two sublethal challenges, which constituted primary and secondary immunizations, mice developed pulmonary and serum immunoglobulin G and A antibody recognizing both lipopolysaccharide and invasion plasmid antigens IpaB and IpaC. Immune mice and naive control mice differed in lung lavage cytokine levels following lethal challenge. Immune mice developed significantly elevated levels of pulmonary gamma interferon within 6 h of challenge, while naive control mice developed elevated levels of this cytokine later during the initial 24-h period. Both groups had elevated levels of gamma interferon during the 24- to 48-h period of infection. Both groups also had elevated levels of tumor necrosis factor alpha within 6 h of challenge, but the control mice had significantly higher levels at the 48- and 72-h time points. Elevated levels of interleukin-4 were observed only in immunized mice. This cytokine appeared within 24 h and receded between 48 and 72 h. Fluorescence-activated cell sorter analysis of lung parenchymal cells showed that both groups experienced an initial influx of monocytes, but the proportion of this cell type began to recede in immunized mice after 48 h of infection, while peak levels were maintained in the control animals. These studies suggest that elements of local B lymphocyte activity, as well as Th1 and Th2 lymphocyte activity, may contribute to the survival of immune mice after intranasal challenge with shigellae.

Administration, Intranasal↗
PubMed1995

Intransal or intragastric immunization with proteosome-Shigella lipopolysaccharide vaccines protects against lethal pneumonia in a murine model of Shigella infection.

Mice immunized intransally or intragastrically with proteosome vaccines containing either Shigella sonnei or S. flexneri 2a lipopolysaccharide were protected against lethal pneumonia caused by homologous organisms in an experimental murine intranasal challenge model of Shigella infection. Histopathological analysis demonstrated that immunization also protected against the progressive lesions resulting from invasion of the pulmonary mucosa by S. sonnei. These data show that mucosal proteosome-lipopolysaccharide vaccines can protect against lethal bacterial pneumonia and indicate that such vaccines are promising candidates for protection against intestinal shigellosis.

Animals↗
PubMed1995

Protection against local Shigella sonnei infection in mice by parenteral immunization with a nucleoprotein subcellular vaccine.

Nucleoprotein subcellular (NPS) vaccine, consisting of ribosome-bound O polysaccharide, was prepared from avirulent Shigella sonnei. NPS vaccine was tested for safety and protective activity in the mouse intranasal challenge model of Shigella infection. The vaccine was nontoxic when injected in doses up to 10,000 micrograms, and a single subcutaneous injection of as little as 0.1 micrograms gave significant protection against a lethal intranasal challenge with S. sonnei. These data demonstrate the induction of local protective immunity by parenteral immunization, support the concept of the ribosome as a potent vaccine vector, and give additional evidence for the protective activity of the NPS vaccine against Shigella infection.

Animals↗
PubMed1993

Evaluation of Shigella vaccine safety and efficacy in an intranasally challenged mouse model.

Five Shigella vaccine candidates (EcSf2a-1, EcSf2a-2, Sfl124, T32-Istrati and SMD) were tested for safety and efficacy in Balb/cJ mice using an intranasal challenge model. Experiments in this model suggest that (i) the relative attenuation of vaccines can be determined in mice by intranasal inoculation, (ii) all vaccines tested elicited antibacterial mucosal immunity protecting against pulmonary infection with Shigella flexneri 2a, (iii) protection was associated with serum IgA and/or IgG antibody recognizing the 2a somatic antigen.

Administration, Intranasal↗
PubMed1992

Patterns of antibody specificity during the BALB/c immune response to hen eggwhite lysozyme.

We tested 49 BALB/c antilysozyme mAb from seven intervals during the immune response to lysozyme for patterns of specificity and avidity. We found that the antibody epitopes in composite covered at least 80% of the lysozyme surface, and their patterns of overlap suggest a continuum of potential antibody epitopes. Previously observed regional specificities, which emerged at different times in the immune response, were more discretely defined in late response antibodies, when the majority of mAb could be assigned to one of three functionally nonoverlapping complementation groups. The area covered by each antigenic region may be greater than an individual epitope, and may include multiple epitopes that overlap structurally and functionally to varying degrees. Connectivity between antigenic regions was seen in interactions among early and late stage antibodies, and among secondary stage mAb, but not among tertiary stage mAb from hyperimmunized mice. Patterns of overlap of early and late response antibodies suggest that the organization of antibody specificities change during the progression from primary to secondary to tertiary response. Over the same period in the response, the average relative avidity of IgG1 kappa mAb did not increase, suggesting that "affinity maturation" of serum antibodies reflects an increase in the number and diversity of antibodies, rather than an overall increase in the avidity of individual antibodies.

Animals↗
PubMed1989

Direct quantitative in situ hybridization studies of Ig VH utilization. A comparison between unstimulated B cells from autoimmune and normal mice.

This study examines Ig VH utilization in murine lupus with emphasis on the relative contribution of 3' and 5' gene families. We used in situ hybridization with 35S-labeled ssRNA probes to detect VH expression in individual spleen cells. Cells were taken from unmanipulated animals, and were not stimulated in vitro. This approach allows analysis of VH usage among only those B cells which have undergone activation in vivo, while minimizing the potential for skewing in vitro. We compared usage of the 3' 7183 and Q52 families with the more 5' J558 family in adult NZB, MRL-lpr/lpr, and nonautoimmune NIH Swiss mice. VH utilization in the autoimmune strains was proportionate to VH family size, and was not biased toward the 3' families when compared with the Swiss repertoire. Moreover, 3' skewing did not develop in NZB mice with increasing age. Thus, systemic autoimmunity is not associated with impaired normalization of the adult repertoire away from the 3' bias of early ontogeny. Instead, our data support a stochastic model for VH gene usage in the activated B cells and plasma cells of adult lupus mice.

Animals↗
PubMed1989

A substantial proportion of the adult BALB/c available B cell repertoire consists of multireactive B cells.

A variety of studies have documented multireactive antibodies in both the preimmune and naturally activated repertoire, but the relationship of these primarily IgM multireactive antibodies to antigen-specific primary and secondary response antibodies is currently not defined. In order to characterize the BALB/c preimmunization specificity repertoire and the baseline of naturally activated antibodies from which the immune response to a specific antigen (hen egg-white lysozyme, HEL) develops, panels of polyclonally activated blast-derived hybridomas (BlAbs) and natural antibody hybridomas (NAbs) from the spleens of unimmunized mice were screened for binding to a panel of nine complex antigens. Over half of the IgM-secreting BlAbs produced antibodies that were antigen-reactive; of these, over half were multireactive, i.e. capable of binding more than one complex antigen. There was no bias towards self vs foreign or thymus-dependent vs thymus-independent antigens. The frequency of antigen-reactive NAbs was about half the frequency of antigen-reactive antibodies found among the BlAbs. However, over half of the antigen-reactive NAbs were also multireactive, and the reactivity profile within the antigen-reactive subset of NAbs was similar to that within the antigen-reactive subset of BlAbs. These results suggest that the available repertoire of adult spleen cells contains a high proportion of multireactive antibodies, and that a subset of the available repertoire is randomly activated, yielding a small proportion of natural antibodies which closely reflect a random sampling of the available repertoire. Although monospecific precursor cells are rare, monospecific IgM BlAbs were found for all antigens in the panel except staphylococcal nuclease and mouse IgG. Monospecific as well as multireactive HEL-binding BlAbs were found at frequencies comparable to other protein antigens in the panel, and HEL-reactive NAbs were also present. On the other hand, it has previously been shown that HEL-reactive IgM antibodies (including multireactive antibodies whose specificities include HEL) are rare or absent in both the primary and secondary response to HEL. This cannot be attributed to an absence of available precursor B cells, and most likely reflects an early recruitment of HEL-reactive clones into the peripheral B cell pool. The possibility that polyreactive B cells may serve as precursors for some HEL-specific IgG antibodies is discussed.

Animals↗
PubMed1989

Organ reactive autoantibodies from non-immunized adult BALB/c mice are polyreactive and express non-biased VH gene usage.

To examine the naturally activated autoreactive B cell repertoire, we analyzed a panel of hybridomas from unmanipulated adult BALB/c spleen cells for reactivity patterns and VH gene usage. We found a pattern of VH usage that was diverse and appeared to reflect the germline repertoire. Although all but one natural antibody hybridoma (NAb) were initially selected for organ rather than antigen binding, the majority of organ reactive IgM NAbs were polyreactive, expressing a broad range of reactivity patterns for both self and foreign antigens, that were unique for each NAb and were not indiscriminate. Our results are consistent with the hypothesis that many naturally activated adult B cells are highly polyreactive and that autoreactivity is a consequence of polyreactivity. We suggest that the population of NAbs exhibiting organ reactivity overlaps the populations of other IgM autoantibodies that have been described previously, and that these all derive from a pool of polyreactive IgM antibodies which are polyclonally activated in the early immune response. These polyreactive natural antibodies may represent a first line of defense and offer protection for the host against a variety of foreign agents.

Animals↗
PubMed1988

Unusual joining sites in the H and L chains of an anti-lysozyme antibody.

Nucleotide sequences of HyHEL-5, an antibody specific for chicken lysozyme (HEL), indicated unusual joins in the third complementarity-determining region of both the H and L chains. The VK-JK recombination site is unusual in that codon 96, normally derived from the JK gene segment, is deleted entirely, making the L3 one amino acid shorter than normal. Examination of the HyHEL-5 Fab-HEL x-ray structure suggests that the conformation of L3 is clearly important for Ag specificity. A comparison of the HyHEL-5 L3 with that of the structurally related antibody J539 indicates that the deleted residue significantly alters the conformation of the L3 turn. The H chain VH-DH join is also unusual; the VH junction site has probably occurred between the second and third nucleotides of codon 92, with the addition of five random nucleotides that encode for unusual amino acids Leu93 and His94. Although the conformation of H3 is different from what would be predicted from other H3 conformations and is clearly important to the complementarity of HyHEL-5 to HEL, the specific residues at the VH-DH join do not appear to directly contribute to Ag binding. It is not possible to attribute the main chain conformation of H3 to the particular sequence produced by the join; the structural features of H3 may be due to interactions with HEL and/or with other antibody residues.

Amino Acid Sequence↗
PubMed1986

Role of glutathione in protecting endothelial cells against hydrogen peroxide oxidant injury.

To determine the mechanism responsible for the enhanced susceptibility of endothelial cells to oxidant injury in the absence of glucose, we induced endothelial cell injury with oxygen radicals in the presence of various oxygen radical scavengers and measured endothelial cell levels of glutathione after oxidant injury in the presence and absence of glucose. Endothelial cells were damaged with toxic oxygen radicals generated by phorbol myristate acetate (PMA)-activated polymorphonuclear leukocytes (PMNs) or xanthine-xanthine oxidase in the presence and absence of glucose and catalase (scavenger of hydrogen peroxide), superoxide dismutase (scavenger of superoxide radical), isoleucine, valine, and serine (scavengers of hypochlorous acid), or mannitol, ethanol, benzoic acid, dimethyl sulfoxide, and dimethyl thiourea (scavengers of hydroxyl radical). Endothelial cell injury was quantitated by 2-deoxy-[1-3H] glucose or chromium 51 release assays or both. In each oxidant-generating system, in the presence and absence of glucose, only catalase significantly protected endothelial cells from oxidant injury (P less than 0.001). When endothelial cells were damaged by hydrogen peroxide generated with xanthine-xanthine oxidase in the presence of glucose, endothelial cell levels of glutathione remained unchanged. In contrast, when endothelial cells were damaged with xanthine-xanthine oxidase in the absence of glucose, endothelial cell levels of glutathione fell to less than 50% of baseline (P less than 0.05). Xanthine-xanthine oxidase-mediated endothelial cell damage and depletion of glutathione in the absence of glucose were similar to results obtained in the presence of glucose when glutathione was depleted with buthionine sulfoximine, diethyl maleate, or 1-chloro-2,4-dinitrobenzene.(ABSTRACT TRUNCATED AT 250 WORDS)

Benzoates↗
PubMed1985

Dental caries vaccine: some problems solved?

The interest in a dental caries vaccine has been great over the past few years. Studies have shown two possible problems using Streptococcus mutans as an immunogen: (i) the production of heart reactive antibody, and (ii) the need to protect against several serotypes. Possible solutions to these problems are discussed.

Animals↗
PubMedDate not supplied

Epidermal growth factor accelerates recovery of LLC-PK1 cells following oxidant injury.

In renal tubular epithelial cells, oxidant injury results in several metabolic alterations including ATP depletion, decreased Na+K+ATPase activity, and altered intracellular sodium and potassium content. To investigate the recovery of LLC-PK1 cells following oxidant injury and to determine if recovery can be accelerated, we induced oxidant stress in LLC-PK1 cells with 500 microM hydrogen peroxide for 60 min. Identical cohorts of oxidant-stressed cells were incubated in recovery medium without epidermal growth factor (EGF) or recovery medium containing 25 ng EGF per ml. ATP levels, Na+K+ATPase activity in whole cells, Na+K+ATPase activity in disrupted cells, and intracellular sodium and potassium ion content were determined at 0, 5, 24, 48, and 72 h following oxidant injury in each cohort of cells. In oxidant-stressed cells recovering in medium without EGF, ATP levels, Na+K+ATPase activity, and intracellular ion content improved but continued to remain substantially lower than control values at all time points following oxidant stress. In cells recovering in medium with EGF, ATP levels, Na+K+ATPase activity, and the intracellular potassium-to-sodium ratio were significantly higher at nearly all time points than values in cells recovering in medium alone. In cells recovering with added EGF, Na+K+ATPase activity had improved to control levels, whereas ATP levels and intracellular ion content approached control values by 72 h following oxidant stress. We conclude that oxidant-mediated ATP depletion, altered Na+K+ATPase activity, and intracellular ion content remain depressed for several d following oxidant stress and that EGF accelerated recovery of LLC-PK1 cells from oxidant injury.

Adenosine Triphosphate↗