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Biomedical subjects

A J Stagg

Publications and source records attributed to A J Stagg.

At least 19 recordsLinked to original sources
PubMed2000

Generation of protective immune responses to plague by mucosal administration of microsphere coencapsulated recombinant subunits.

We have investigated noninvasive immunization to plague. Recombinant subunit antigens, F1 and V from Yersinia pestis, were coencapsulated in biodegradable poly(L100 LD(50's) inhalational challenge with virulent Y. pestis. These data expand on previous findings from our laboratories, providing further insight into the mechanics of safeguarding mice from plague through nasal immunization. Further, these results demonstrate that in a murine model, solid protection from pneumonic plague can be engendered by two intranasal administrations of appropriately formulated recombinant proteins.

Administration, Intranasal↗
PubMed1999

Murine dendritic cells internalize Leishmania major promastigotes, produce IL-12 p40 and stimulate primary T cell proliferation in vitro.

Metacyclic Leishmania promastigotes (PM), transmitted by sand-fly bite, are likely to interact initially with cells of the dendritic cell (DC) lineage(s) in the epidermis or dermis. Epidermal Langerhans cells internalize L. major amastigotes (AM) and transport them to draining lymph nodes (Moll, H., Fuchs, H., Blank, C. and Röllinghoff, M., Eur. J. Immunol. 1993. 23: 1595) but little is known about the interaction of DC with PM. The present study demonstrates that DC are able to internalize PM and that the fate of the parasites within DC differs from that within macrophages (Mphi). DC took up small numbers of PM which did not differentiate into AM but appeared to be degraded; Mphi internalized large numbers of PM into parasitophorous vacuoles where they differentiated into AM. In response to direct stimulation with PM, DC from both C3H ("resistant" to L. major infection) and BALB/c ("susceptible") up-regulated production of IL-12 p40. In contrast, IL-12 production by Mphi was not detected. DC exposed to either metacyclic PM or PM culture supernatants were also able to stimulate proliferative responses in lymph node T cells from naive mice. These data indicate that DC have the capacity to promote protective Th1 immune responses in Leishmania infection and suggest that DC exposed to PM may be useful in immunotherapy and vaccination.

Animals↗
PubMed1999

The SCID/Beige mouse as a model to investigate protection against Yersinia pestis.

In this study, we have shown that severe combined immunodeficient/beige mice reconstituted with hyperimmune Balb/c lymphocytes can be used as a model to demonstrate adoptive and passive protection against plague infection. Reconstitution of severe combined immunodeficient/beige mice was successful in nine out of ten mice as demonstrated by spleen colonisation and sustained circulating immunoglobulin titres. Furthermore, an increase in antibody titre was evident after a booster immunisation of reconstituted mice. Presence of circulating antibody correlated with protection against a systemic plague challenge and indicated that in reconstituted mice adoptive transfer of a functional immune system had occurred. The severe combined immunodeficient/beige mouse was also used to demonstrate passive protection against inhaled and systemic plague infection. The reconstituted severe combined immunodeficient/beige mouse model demonstrating protective immunity against plague will be further developed to identify the immune cell subsets responsible for this protection.

Adoptive Transfer↗
PubMed1999

Inflammatory disease in HLA-B27 transgenic rats.

UNLABELLED: A spontaneous inflammatory disease in rats transgenic for HLA-B27 resembles the B27-associated human spondyloarthropathies. Colitis and arthritis, the two most important features, require T cells, gut bacteria, and high expression of B27 in bone marrow-derived cells. Control rats with HLA-B7 remain healthy. Most rats with HLA-Cw6 (associated with psoriasis vulgaris) remain healthy; a minority develop mild and transient disease. Rats with a mutant B27 with a Cys67-->Ser substitution resemble wild-type B27 transgenics, but with a lower prevalence of arthritis. A similar phenotype is seen in B27 rats co-expressing a viral peptide that binds B27. Disease-prone LEW but not F344 B27 rats develop high serum IgA levels concurrent with disease progression. Colitis is associated with high interferon-gamma, arthritis with high interleukin-6. Disease is similar in B27 LEW, F344, and PVG rats, but the DA background is protective. CONCLUSIONS: The spondyloarthropathy-like disease in rats is specific for HLA-B27 but does not require Cys67. Arthritis but not colitis is particularly sensitive to B27 peptide-binding specificity. Genetic background exerts a strong influence, but some phenotypic differences exist between permissive strains that do not influence disease susceptibility. The data favor a role for B27 peptide presentation in arthritis, but other mechanisms to explain the role of B27 have not been excluded.

Amino Acid Sequence↗
PubMed1998

Vaccines against Chlamydia: approaches and progress.

Infections of the eye and genital tract with the bacterium Chlamydia trachomatis are a major cause of morbidity worldwide and are costly to treat. Development of a vaccine capable of protecting against infection or severe disease presents special challenges but would be the most effective long-term option for control of chlamydial disease. Progress has been made in understanding protective and pathological immune mechanisms in these infections, and a number of potential vaccine candidates have been developed.

Animals↗
PubMed1998

Efficacy of doxycycline and ciprofloxacin against experimental Yersinia pestis infection.

The efficacies of ciprofloxacin and doxycycline prophylaxis and therapy were assessed against experimental pneumonic plague infections induced by two strains of Yersinia pestis in a mouse model. When exposed to an aerosol of Y. pestis strain GB, containing 8.39 x 10(5) +/- 4.17 x 10(4) cfu, the retained dose was 7.3 x 10(3) +/- 2.3 x 10(3) cfu. When exposed to an aerosol of Y. pestis strain CO-92, containing 1.86 x 10(5) +/- 7.4 x 10(3) cfu, the retained dose was 3.4 x 10(4) +/- 2.6 x 10(3) cfu. Both strains resulted in a respiratory and systemic infection closely resembling human pneumonic plague. Ciprofloxacin prophylaxis and therapy was successful against both strains for up to 24 h after challenge, but not after 48 h. Both doxycycline prophylaxis and therapy regimens were ineffective against both strains, although strain CO-92 was more susceptible in vitro to doxycycline than strain GB and supra-MIC levels were achieved in the serum and lungs of the animal.

Animals↗
PubMed1998

Protection against ascending infection of the genital tract by Chlamydia trachomatis is associated with recruitment of major histocompatibility complex class II antigen-presenting cells into uterine tissue.

A mouse model of ascending infection following intravaginal inoculation with a strain of Chlamydia trachomatis isolated from humans has been used to identify immune mechanisms associated with protection against genital infection. BALB/c and C3H mice differed in their susceptibilities to infection and inflammatory disease. In both mouse strains, ascension of the organism and recruitment of bone marrow-derived mononuclear leukocytes were evident in uterine tissue 1 week postinfection. By 3 weeks the organism had been cleared and inflammation had been resolved in the BALB/c mice, but both persisted in the C3H animals. In athymic nude BALB/c mice both the organism and inflammation persisted, indicating the influence of the hosts' immune response on the outcome of infection. Both BALB/c and C3H mice had a Th1 response in draining lymph nodes, with predominant production of gamma interferon and tumor necrosis factor alpha, low levels of interleukin-10, and no detectable levels of interleukin-4. However, the composition of the early uterine infiltrate differed in these two mouse strains. Cell surface labeling and analysis of light scatter properties by flow cytometry identified a population of large, CD45(+) major histocompatibility complex class II mononuclear cells, which were a prominent feature of the infiltrates in BALB/c mice but were present in significantly lower numbers in C3H mice. These cells expressed the costimulatory molecules CD86 and CD40 and stimulated allogeneic T cells, suggesting that these mononuclear cells are a population of antigen-presenting cells and that they may play a role in clearing antigen and protecting against inflammatory disease in BALB/c mice. An additional level of immunological control may thus exist in genital chlamydial infection.

Animals↗
PubMed1997

A sub-unit vaccine elicits IgG in serum, spleen cell cultures and bronchial washings and protects immunized animals against pneumonic plague.

In this study, the protection afforded against aerosolized Yersinia pestis by injection of an alhydrogel-adsorbed sub-unit vaccine has been compared with that given by an existing killed whole cell vaccine licensed for human use. The sub-unit vaccine protected mice against exposure to > 10(4) colony-forming units (c.f.u.) of virulent plague organisms (100 LD50 doses), whereas the whole cell vaccine provided only 50% protection against 1.8 x 10(3) c.f.u. In sub-unit vaccinees, IgG to each of the F1 and V antigens contained in the vaccine, was detected in serum, on direct secretion by spleen cells and in broncho-alveolar washings (BAL). In killed whole cell vaccinees, physiologically significant levels of IgG to F1 only were detectable in equivalent samples. Levels of F1-specific IgG in serum, secreted from spleen cells and in BAL were significantly higher (P < 0.01) in sub-unit compared with killed whole cell vaccinees. IgA was not detected in BAL from intra-muscularly dosed sub-unit vaccinees and thus the protection achieved against inhalational challenge with Yersinia pestis is attributed to the induction of systemic immunity to both the F1 and V antigens in the sub-unit vaccine. The enhanced protective efficacy of this sub-unit vaccine over an existing vaccine has been demonstrated in an animal model of pneumonic plague.

Animals↗
PubMed1997

Human blood dendritic cells: binding to vascular endothelium and expression of adhesion molecules.

To investigate the binding properties of dendritic cells (DC) to vascular endothelium, a comparative analysis was undertaken of DC, monocytes and lymphocytes isolated from the blood of 25 healthy subjects using monolayers of human umbilical vein endothelial cells as the adherence substrate. More blood DC (mean 24% adherence) were adherent to endothelial monolayers than monocytes (mean 18%; P < 0.001) and lymphocytes (mean 12%; P < 0.001). When the monolayers were pretreated with tumour necrosis factor-alpha (TNF-alpha) all leucocyte populations exhibited an increased attachment, but there was still greater binding of DC (mean 37% adherence) in comparison with monocytes (mean 23%; P < 0.001) and lymphocytes (mean 18%; P < 0.001). Flow cytometric analysis revealed that in relation to monocytes and lymphocytes the DC had a higher surface expression of the adhesion molecules CD11a (P < 0.05), CD11c (P < 0.005) and CD54 (P < 0.005) but a lower prevalence of cells bearing CD49d (mean 38%; P < 0.05) and the homing receptor CD62L (mean 14%; P < 0.001). CD1a was present on 22% of DC and virtually absent from the surface of monocytes and lymphocytes. The intensity of expression of the beta1-integrins, CD49c, CD49d and CD49e was greater on DC than lymphocytes and monocytes (P < 0.05). Antibody blocking studies demonstrated that DC binding to untreated and TNF-alpha-treated endothelium was dependent upon the expression of CD11a, CD18 and CD49d, and the simultaneous application of anti-CD18 and anti-CD49d antibodies produced an approximate 70% inhibition of adhesion (P < 0.001). Thus, the expression of both beta1- and beta2-integrins contributes to the adhesive interaction between DC and endothelium.

Cell Adhesion↗
PubMed1996

Antigen-presenting cells but not lymphocytes in the joint may indicate the cause of reactive arthritis.

T cells and antigen-presenting cells (APC) accumulate in the joint in reactive arthritis and there are reports that the T cells are a population selected for responsiveness to the causative agent. In this work, the latter view is questioned by detailed studies of the antigen specificities of the lymphocytes within the joint (SFMC) and peripheral blood (PBMC) of patients with reactive arthritis triggered by infection with Chlamydia trachomatis. Using a hanging-drop microculture system. SFMC displayed enhanced responses not only to antigens from the triggering organism, but also to other antigens, including PPD and tetanus toxoid, to which the patients were likely to have had prior exposure. No evidence was obtained for a dominant cross-reactive T-cell response to epitopes common to these antigen preparations, confirming the polyclonal nature of the infiltrate. In contrast to the broad specificity of the T-cell infiltrate, two experimental approaches indicated that APC within the joint carried chlamydial antigen. The failure of antigen-bearing APC to interact with T cells at this site may underlie the inability to clear microbial antigen from the joint.

Antigen Presentation↗
PubMed1995

A comparison of Plague vaccine, USP and EV76 vaccine induced protection against Yersinia pestis in a murine model.

The median lethal dose (MLD) of a pathogenic strain of Yersinia pestis was established by three routes of administration in three strains of mouse. There was no significant difference between the MLDs in the different strains of mouse. The MLD by the subcutaneous route in Balb/C and an outbred line was approximately 1 c.f.u.; the MLD following intraperitoneal administration was tenfold higher. There were significant differences in the mean times to death after administration of the challenge by different routes. The relative efficacy of a live attenuated vaccine strain of Y. pestis (EV76) was compared with that of the formaldehyde-killed vaccine (Plague vaccine, USP). EV76 protected against high challenge doses (up to 5.75 x 10(6) MLD), though immunized animals showed side effects of varying severity. The killed vaccine was less effective in terms of dose-protection (deaths occurred after challenge with 4000 MLD) and several of the vaccinated animals suffered sub-lethal, plague-related sequelae to the challenge.

Animals↗
PubMed1994

Failure in antigen responses by T cells from patients with common variable immunodeficiency (CVID).

Antigen-driven responses by T cells from patients with CVID and normal subjects have been assessed. Low-density cells enriched for antigen-presenting dendritic cells were cultured with T cells using a 20-microliters hanging drop system. T cells from all subgroups of CVID patients showed markedly reduced responses to the recall antigens purified protein derivative (PPD) or tetanus toxoid, whereas responses by cells from patients with X-linked agammaglobulinaemia, used as a disease control, were in the normal range. However, primary allo-stimulation of CVID T cells was normal. CVID cells from two patients failed to respond to stimulation with a neoantigen, an HIV env peptide, under conditions where normal T cells did respond. These data illustrate a profound defect in antigen-stimulated T cell proliferation in vitro in all groups of CVID patients, but do not distinguish whether the defect is in the presenting cell or in the T lymphocyte. In vivo, germinal centre B cells are thought to present antigen to primed T cells to obtain essential signals (e.g. CD40 ligand and IL-2) for B cell survival and progression to immunoglobulin secretion. A failure of antigen-specific T cell function in vivo in CVID would thus not provide the primed T cells needed for B cell rescue, and could be the primary defect leading to the low immunoglobulin production in this condition.

Antigen-Presenting Cells↗
PubMed1993

Antigen-presenting cell types.

Different antigen-presenting cells elicit responses in different T-cell populations for primary activation, secondary stimulation and cytotoxic effector functions. Maturing bone marrow derived dendritic cells may acquire and process antigens, transport them to lymph nodes and activate naive T cells located there. By contrast, follicular dendritic cells, acquiring antigen-antibody complexes, maintain 'memory' via B-cell activation. Effector memory T cells recognize various tissue cells bearing antigen and we speculate that they may also target specialized antigen-presenting dendritic populations.

Animals↗
PubMed1993

Primary human T-cell responses to the major outer membrane protein of Chlamydia trachomatis.

The major outer membrane protein (MOMP) of Chlamydia trachomatis is the main candidate antigen for a synthetic vaccine against chlamydial infection. Antibodies to surface-exposed epitopes on MOMP neutralize chlamydial infectivity but little is known about T-cell recognition of the molecule. We have measured primary human T-cell responses to recombinant fragments of MOMP as well as to the whole organism and synthetic MOMP peptides. Using antigen-pulsed low density cells (LDC) we were able to stimulate proliferative responses with T cells from most naive individuals. This response was antigen dose dependent and displayed an absolute requirement for dendritic cells in the antigen-presenting cell (APC) population. Several T-cell epitopes were identified in MOMP and one which stimulated T cells from 80% of donors was resolved as a 12 amino acid synthetic peptide. Dual cell surface labelling and cell cycle analysis by FACS revealed that both CD4+ and CD8+ T cells were stimulated in these cultures. The fact that we were able to obtain proliferative responses and interferon-gamma (IFN-gamma) production to MOMP using cells from cord bloods confirmed that these are genuine primary responses. These experiments have identified a region on MOMP, to which T cells from most humans make a primary response, which may be useful in a chlamydial vaccine. The approach is useful for vaccine development in general.

Amino Acid Sequence↗
PubMed1991

The distribution and functional properties of dendritic cells in patients with seronegative arthritis.

Dendritic cells (DC), potent antigen-presenting cells, are known to be increased in numbers in inflammatory lesions in rheumatoid arthritis and juvenile chronic arthritis. In this study, patients with seronegative arthritis were studied; the distribution and functional properties of DC enriched low density cells (LDC) from peripheral blood (PB) and synovial fluid (SF) were compared. The composition of LDC from both sources was similar, comprising approximately 30% DC, 60% monocytes with few T lymphocytes. SF was significantly enriched for LDC compared with paired peripheral blood (P less than 0.0001) or peripheral blood from healthy controls (P less than 0.001). In contrast, patient PB contained fewer LDC (P less than 0.05) overall than healthy controls. LDC from both sources were potent simulators of allogeneic PB T cells in a mixed leucocyte reaction (MLR), but in four out of 10 patients SF LDC were significantly more stimulatory. In autologous MLRs (AMLRs) SF T cells were not stimulated by either LDC population. This anergy of T cells was confined to the joint as patient PB T cells showed an AMLR response to PB LDC which was similar to that seen in cells from healthy controls. PB T cells also responded to SF LDC; in a minority of patients SF LDC caused significantly greater stimulation in AMLR than PB LDC and the possibility is discussed that this may represent presentation of antigen acquired in vivo.

Arthritis↗
PubMed1991

Peripheral blood and synovial fluid T cells differ in their response to alloantigens and recall antigens presented by dendritic cells.

Properties of T cells from inflammatory lesions were analysed by comparing the response of peripheral blood (PB) and synovial fluid (SF) T cells from 19 patients with a range of arthropathies to enriched allogeneic dendritic cells (DC) in a primary mixed leucocyte reaction (MLR). In 17 patients the proliferative response of SF T cells was significantly (P less than 0.05) less than that of PB lymphocytes. The reduced response of SF T cells was observed in all disease categories studied and could not be attributed to differences in cell number requirements or response kinetics. Addition of recombinant interleukin-2 enhanced the response of SF T cells in a dose-dependent manner. Cell mixing experiments suggested that active suppression was not the underlying mechanism of the poor MLR response of SF T cells. In contrast to the MLR response. SF T cells were able to mount vigorous proliferative responses to recall antigen presented by autologous antigen-presenting cells. The possibility is discussed that T cells compartmentalized at inflammatory lesions are a unique population with a diminished ability to interact with DC and respond to primary stimuli but an ability to respond to secondary antigenic challenge.

Arthritis↗