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K H Mills

Publications and source records attributed to K H Mills.

At least 37 records · Page 2Linked to original sources
PubMed1999

Glycerol-induced seizure: involvement of IL-1beta and glutamate.

It is widely accepted that interleukin-1beta (IL-1beta), a cytokine produced not only by cells of the immune system but also by cells of the central nervous system, modulates hippocampal function. Here we investigate the effect of a seizure-induced increase in hippocampal IL-1beta concentration on neurotransmitter release. We report that oral administration of glycerol evoked seizure activity in BALB/c mice. Associated with these convulsions was an induction of IL-1beta gene expression and a significant increase in cytokine protein in the hippocampus. Release of glutamate in synaptosomes prepared from hippocampi of these animals was reduced compared to control. These results are consistent with previous data suggesting a modulatory effect of IL-1beta on glutamate release in hippocampus.

Animals↗
PubMed1999

The adjuvant combination monophosphoryl lipid A and QS21 switches T cell responses induced with a soluble recombinant HIV protein from Th2 to Th1.

The induction of protective immunity with recombinant vaccines is dependent on the identification of adjuvant or delivery systems that can augment immune responses, especially cellular immune responses, to soluble protein antigen. In this study we demonstrate that an adjuvant formulation comprising QS21, a purified form of saponin and 3D-monophosphoryl lipid A (MPL), a nontoxic derivative of lipopolysaccharide (LPS), enhances cellular and humoral immune responses to a recombinant HIV protein. Analysis of cytokine secretion by antigen-specific T-cells from the spleen demonstrated that QS21 augmented Th1 and Th2 responses, whereas addition of 3D-MPL resulted in preferential induction of type 1 T-cells. Furthermore, analysis of the subclass of the IgG antibody in the serum in mice immunized with gp120 with the combined adjuvant formulation confirmed the selective activation of Th1 cells in vivo. 3D-MPL was found to enhance B7-1 expression and IL-12 production by macrophages, which are known to be involved in the LPS-induced enhancement of Th1 responses. Thus 3D-MPL appears to act as an adjuvant, without the toxicity associated with LPS, by controlled and selective potentiating effects on antigen presentation and T-cell activation.

AIDS Vaccines↗
PubMed1999

Interferon-gamma mediated immune effector mechanisms against Bordetella pertussis.

The role of IFN-gamma in reducing the intracellular load of Bordetella pertussis in murine macrophages in vitro has been examined. The results demonstrate that exposure to IFN-gamma can reduce bacterial load in viable macrophages and that this is associated with production of nitric oxide (NO). These observations provide a mechanism by which IFN-gamma may mediate its antimicrobial effect and support an important role for activated alveolar macrophages in the elimination of B. pertussis from the respiratory tract. Using intracellular iron chelation, it is shown that intracellular survival of B. pertussis is dependent on iron availability and suggest that iron restriction may be an important mechanism by which IFN-gamma influences bacterial survival within mouse macrophages. It is also shown that IFN-gamma may mediate its effect through NO independent mechanisms and that B. pertussis is sensitive to agents that stimulate the respiratory burst. Finally, it is shown that the concentration of L-tryptophan may be a limiting step in the intracellular survival of B. pertussis and that the induction of tryptophan degrading enzymes may be an additional mechanism through which IFN-gamma exerts its antimicrobial effects against B. pertussis.

Animals↗
PubMed1999

Fasciola hepatica suppresses a protective Th1 response against Bordetella pertussis.

Fasciolosis, like other helminth infections, is associated with the induction of T-cell responses polarized to the Th2 subtype. Respiratory infection with Bordetella pertussis or immunization with a pertussis whole-cell vaccine (Pw) induces a potent Th1 response, which confers a high level of protection against bacterial challenge. We have used these two pathogens to examine bystander cross-regulation of Th1 and Th2 cells in vivo and provide evidence of immunomodulation of host T-cell responses to B. pertussis by a concomitant infection with Fasciola hepatica. Mice with a coinfection of F. hepatica and B. pertussis exhibited a Th2 cytokine profile in response to F. hepatica antigens, similar to those infected with F. hepatica alone. By contrast, the Th1 response to B. pertussis antigens was markedly suppressed and the bacterial infection was exacerbated following infection with F. hepatica. Furthermore, an established Th1 response induced in mice by infection with B. pertussis or by parenteral immunization with Pw was also suppressed following infection with F. hepatica. This immunomodulatory effect of B. pertussis-induced responses by F. hepatica infection is significantly reduced, but not completely abrogated, in IL-4 knockout mice. Our findings demonstrate that Th2-inducing parasites can exert bystander suppression of protective Th1 responses to infection or vaccination with a bacterial pathogen and that the modulation is mediated in part by IL-4 and, significantly, is effective at both the induction and effector stages of the Th1 response.

Animals↗
PubMed1999

Mutants of Escherichia coli heat-labile toxin act as effective mucosal adjuvants for nasal delivery of an acellular pertussis vaccine: differential effects of the nontoxic AB complex and enzyme activity on Th1 and Th2 cells.

Mucosal delivery of vaccines is dependent on the identification of safe and effective adjuvants that can enhance the immunogenicity of protein antigens administered by nasal or oral routes. In this study we demonstrate that two mutants of Escherichia coli heat-labile toxin (LT), LTK63, which lacks ADP-ribosylating activity, and LTR72, which has partial enzyme activity, act as potent mucosal adjuvants for the nasal delivery of an acellular pertussis (Pa) vaccine. Both LTK63 and LTR72 enhanced antigen-specific serum immunoglobulin G (IgG), secretory IgA, and local and systemic T-cell responses. Furthermore, using the murine respiratory challenge model for infection with Bordetella pertussis, we demonstrated that a nasally delivered diphtheria, tetanus, and acellular pertussis (DTPa) combination vaccine formulated with LTK63 as an adjuvant conferred a high level of protection, equivalent to that generated with a parenterally delivered DTPa vaccine formulated with alum. This study also provides significant new information on the roles of the binding and enzyme components of LT in the modulation of Th1 and Th2 responses. LTK63, which lacks enzyme activity, promoted T-cell responses with a mixed Th1-Th2 profile, but LTR72, which retains partial enzyme activity, and the wild-type toxin, especially at low dose, induced a more polarized Th2-type response and very high IgA and IgG antibody titers. Our findings suggest that the nontoxic AB complex has broad adjuvant activity for T-cell responses and that the ADP-ribosyltransferase activity of the A subunit also appears to modulate cytokine production, but its effect on T-cell subtypes, as well as enhancing, may be selectively suppressive.

Adjuvants, Immunologic↗
PubMed1998

Bioaccumulation of radionuclides in fertilized Canadian Shield lake basins.

Radionuclide tracers of heavy metals (59Fe, 60Co, 65Zn, 75Se, 85Sr, 134Cs and 203Hg) representing potential contamination from nuclear power plants, industry and agriculture were added to separate basins of Lake 226, Experimental Lakes Area, northwestern Ontario. The two basins were part of a eutrophication experiment and differed in their trophic status; the north basin (L226N) was eutrophic whereas the south basin (L226S) was mesotrophic. Our objective was to determine the uptake of the radionuclides by biota and the effect of lake trophic status on their bioaccumulation. The trophic status of the lakes did not appear to have a marked effect on the accumulation of radionuclides by the biota. This may have been because of a mid-summer leakage of nutrients between the basins which enhanced primary production in L226S, because there is a time lag between primary production and the availability of the radionuclides to the fishes or because trophic status does not affect the uptake of at least some of these radionuclides. However, there was a tendency for faster uptake of the radionuclides in L226N by fish than L226S, but the differences were not significant. Concentrations in the biota generally decreased in the order: fathead minnow > pearl dace > tadpoles > slimy sculpin > leeches. Concentrations in biota generally decreased in the order. 65Zn > 203Hg > 75Se > 134Cs > 60Co > 85Sr = 59Fe. Cobalt-60 concentrations in tadpoles were greater than in the other biota. Radionuclide concentrations in the tissues of lake whitefish indicated that uptake was predominantly from food. Radionuclide concentrations were usually higher in the posterior gut, liver and kidney than in other tissues, whereas body burdens were generally high in the muscle for 75Se, 134Cs and 203Hg; kidney and gut for 60Co; and bone for 65Zn and 75Se. Mercury-203 burdens were also high in the bone and gut.

Agriculture↗
PubMed1998

Compartmentalization of T cell responses following respiratory infection with Bordetella pertussis: hyporesponsiveness of lung T cells is associated with modulated expression of the co-stimulatory molecule CD28.

We have used a murine respiratory challenge model to examine the local T cell responses in the lung during infection with Bordetella pertussis. T cells from lung parenchyma and airways of naive and infected mice were refractory to both antigen and mitogen stimulation in the presence of lung macrophages. Furthermore irradiated mononuclear cells from the lungs suppressed antigen and mitogen-induced proliferation, but not IFN-gamma production, by splenic T cells. Removal of macrophages and stimulation of purified lung T cells in the presence of irradiated splenic antigen-presenting cells fully restored the response to mitogen. However, T cells purified from the lung during the acute phase of infection with B. pertussis failed to proliferate or produce detectable levels of IL-2, IL-4, IL-5 or IFN-gamma in response to purified bacterial antigens. In contrast, splenic T cells from these animals produced high levels of IL-2 and IFN-gamma and proliferated strongly to a range of bacterial components. Phenotypic analysis of bronchoalveolar lavage cells during the course of infection revealed transient infiltration of neutrophils, followed by macrophages, CD4+ T cells and smaller numbers of CD8+ T cells and gammadelta+ T cells. Cell surface expression of B7 on infiltrating macrophages and CTLA-4 on T cells did not change significantly during infection. However, expression of the CD28 co-stimulatory molecule was profoundly reduced on lung T cells during the acute phase of infection. In contrast, lung T cells from mice primed by B. pertussis infection or vaccination were resistant to CD28 down-regulation. These results suggest compartmentalization of T cell responses between the lung and the periphery during B. pertussis infection and that B. pertussis may have immunomodulatory properties on local T cell populations in the lungs of naive mice.

Animals↗
PubMed1998

Distinct T-cell subtypes induced with whole cell and acellular pertussis vaccines in children.

Recent clinical trials have demonstrated that new generation acellular pertussis vaccines can confer protection against whooping cough. However, the mechanism of protective immunity against Bordetella pertussis infection induced by vaccination remains to be defined. We have examined cellular immune responses in children immunized with a range of acellular and whole cell pertussis vaccines. Immunization of children with a potent whole-cell vaccine induced B. pertussis-specific T cells that secreted interferon-gamma (IFN-gamma), but not interleukin-5 (IL-5). In contrast, T cells from children immunized with acellular pertussis vaccines secreted IFN-gamma and/or IL-5 following stimulation with B. pertussis antigens in vitro. These observations suggest that protective immunity conferred by whole-cell vaccines, like natural immunity, is mediated by type 1 T cells, whereas the mechanism of immune protection generated with acellular vaccines may be more heterogeneous, involving T cells that secreted type 1 and type 2 cytokines.

Antigens, Bacterial↗
PubMed1998

Approaches to new vaccines.

The explosive technological advances in the fields of immunology and molecular biology in the last 5 years had an enormous impact on the identification of candidate vaccines against diseases, which until a few years ago seemed uncontrollable. Increased knowledge of the immune system has helped to define the mechanisms that underlie successful immunization and is now being exploited to develop improved versions of existing vaccines and new vaccines against emerging pathogens, tumors, or autoimmune diseases. An understanding of the mechanisms of action of novel adjuvants and the development of new vector and delivery systems will have a major impact on vaccine strategies. The use of DNA encoding antigens from pathogenic viruses, bacteria, and parasites as vaccines is a new approach that is receiving considerable attention. This and other innovative approaches, including vaccine production in plants, are appraised in this review. The successful eradication of smallpox and the imminent eradication of poliomyelitis by worldwide immunization campaigns provide positive examples of how the vaccine-mediated approach can lead to disease elimination; with the advent of new vaccines and improved delivery systems, there is no scientific reason why these successes cannot be repeated.

Adjuvants, Immunologic↗
PubMed1998

Pertussis toxin potentiates Th1 and Th2 responses to co-injected antigen: adjuvant action is associated with enhanced regulatory cytokine production and expression of the co-stimulatory molecules B7-1, B7-2 and CD28.

Pertussis toxin (PT) is a major virulence factor of Bordetella pertussis which exerts a range of effects on the immune system, including the enhancement of IgE, IgA and IgG production, delayed-type hypersensitivity reactions, and the induction of experimental autoimmune diseases. However, the mechanism by which PT mediates adjuvanticity remains to be defined. In this investigation we have shown that PT can potentiate antigen-specific T cell proliferation and the secretion of IFN-gamma, IL-2, IL-4 and IL-5 when injected with foreign antigens. A chemically detoxified PT and a genetic mutant with substitutions/deletions in the S-1 and B oligomer components that abrogate enzymatic and binding activity displayed no adjuvant properties. In contrast, a non-toxic S-1 mutant devoid of enzymatic activity but still capable of receptor binding retained its adjuvanticity, augmenting the activation of both Th1 and Th2 subpopulations of T cells. In an attempt to address the mechanism of T cell activation, we found that PT stimulated the production of IFN-gamma and IL-2 by naive T cells and IL-1 by macrophages. Therefore potentiation of distinct T cell subpopulations may have resulted in part from the positive influence of IFN-gamma on the development of Th1 cells and the co-stimulatory role of IL-1 for Th2 cells. Furthermore, PT augmented expression of the co-stimulatory molecules B7-1 and B7-2 on macrophages and B cells, and CD28 on T cells, suggesting that the adjuvant effect may also be associated with facilitation of the second signal required for maximal T cell activation. This study demonstrates that the immunopotentiating properties of PT are largely independent of ADP-ribosyltransferase activity, but are dependent on receptor binding activity and appear to involve enhanced activation of T cells.

Adjuvants, Immunologic↗
PubMed1998

A murine model in which protection correlates with pertussis vaccine efficacy in children reveals complementary roles for humoral and cell-mediated immunity in protection against Bordetella pertussis.

The results of phase 3 efficacy trials have shown that acellular and whole-cell pertussis vaccines can confer protection against whooping cough. However, despite the advances in vaccine development, clinical trials have not provided significant new information on the mechanism of protective immunity against Bordetella pertussis. Classical approaches based on measurement of antibody responses to individual antigens failed to define an immunological correlate of protection. A reliable animal model, predictive of acellular and whole-cell pertussis vaccine potency in children, would facilitate an elucidation of the mechanism of immune protection against B. pertussis and would assist in the regulatory control and future development of pertussis vaccines. In this study, we have shown that the rate of B. pertussis clearance following respiratory challenge of immunized mice correlated with vaccine efficacy in children. Using this model together with mice with targeted disruptions of the gamma interferon (IFN-gamma) receptor, interleukin-4 or immunoglobulin heavy-chain genes, we have demonstrated an absolute requirement for B cells or their products in bacterial clearance and a role for IFN-gamma in immunity generated by previous infection or immunization with the whole-cell pertussis vaccine. The results of passive immunization experiments suggested that protection early after immunization with acellular pertussis vaccines is mediated by antibody against multiple protective antigens. In contrast, more complete protection conferred by previous infection or immunization with whole-cell pertussis vaccines reflected the induction of Th1 cells. Our findings suggest that the mechanism of immunity against B. pertussis involves humoral and cellular immune responses which are not directed against a single protective antigen and thus provide an explanation for previous failures to define an immunological correlate of protection.

Animals↗
PubMed1998

A respiratory challenge model for infection with Bordetella pertussis: application in the assessment of pertussis vaccine potency and in defining the mechanism of protective immunity.

The evaluation of vaccines for human use usually requires the development of appropriate animal models and the definition of laboratory correlates of immunity. Traditionally whole cell pertussis vaccines have been controlled by using an active mouse protection test, which measures protection following intracerebral challenge with Bordetella pertussis. However, this test is unsuitable for assessing the potency of the new generation acellular pertussis vaccines. In the present study we demonstrate that a murine respiratory challenge model for infection with B. pertussis is suitable for assessing the potency of acellular and whole cell pertussis vaccines. To allow standardization of different vaccines we have expressed the area under the clearance curve for immunized mice as a ratio of that for non-immunized controls to obtain a potency index. A comparison of estimated vaccine efficacy in children with potency in the murine model results in a highly significant correlation (r = 0.976, p < 0.001). Furthermore, we have used this model to define the protective mechanism of immunity against respiratory infection with B. pertussis and demonstrate a requirement for both specific T and B cells. In accordance with studies in humans, no clear relationship was observed between monotypic serum antibody responses against the putative protective antigens of B. pertussis and protection. In contrast, the most potent protection was observed when the T cell response is polarized to the Th1 subtype.

Animals↗
PubMed1997

Atypical disease after Bordetella pertussis respiratory infection of mice with targeted disruptions of interferon-gamma receptor or immunoglobulin mu chain genes.

Using a murine respiratory challenge model we have previously demonstrated a role for Th1 cells in natural immunity against Bordetella pertussis, but could not rule out a role for antibody. Here we have demonstrated that B. pertussis respiratory infection of mice with targeted disruptions of the genes for the IFN-gamma receptor resulted in an atypical disseminated disease which was lethal in a proportion of animals, and was characterized by pyogranulomatous inflammation and postnecrotic scarring in the livers, mesenteric lymph nodes and kidneys. Viable virulent bacteria were detected in the blood and livers of diseased animals. An examination of the course of infection in the lung of IFN-gamma receptor-deficient, IL-4-deficient and wild-type mice demonstrated that lack of functional IFN-gamma or IL-4, cytokines that are considered to play major roles in regulating the development of Th1 and Th2 cells, respectively, did not affect the kinetics of bacterial elimination from the lung. In contrast, B cell-deficient mice developed a persistent infection and failed to clear the bacteria after aerosol inoculation. These findings demonstrate an absolute requirement for B cells or their products in the resolution of a primary infection with B. pertussis, but also define a critical role for IFN-gamma in containing bacteria to the mucosal site of infection.

Aerosols↗