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Biomedical subjects

A M Jackson

Publications and source records attributed to A M Jackson.

At least 19 recordsLinked to original sources
PubMed2005

Increased expression of unusual EP repeat-containing proteins in the midgut of the tsetse fly (Glossina) after bacterial challenge.

Proteins containing a glutamic acid-proline (EP) repeat epitope were immunologically detected in midguts from eight species of Glossina (tsetse flies). The molecular masses of the tsetse EP proteins differed among species groups. The amino acid sequence of one of these proteins, from Glossina palpalis palpalis, was determined and compared to the sequence of a homologue, the tsetse midgut EP protein of Glossina m. morsitans. The extended EP repeat domains comprised between 36% (G. m. morsitans) and 46% (G. p. palpalis) of the amino acid residues, but otherwise the two polypeptide chains shared most of their sequences and predicted functional domains. The levels of expression of tsetse EP protein in adult teneral midguts were markedly higher than in midguts from larvae. The EP protein was detected by immunoblotting in the fat body, proventriculus and midgut, the known major immune tissues of tsetse and is likely secreted as it was also detected in hemolymph. The EP protein was not produced by the bacterial symbionts of tsetse midguts as determined by genome analysis of Wigglesworthia glossinidia and immunoblot analysis of Sodalis glossinidius. Bacterial challenge of G. m. morsitans, by injection of live E. coli, induced augmented expression of the tsetse EP protein. The presence of EP proteins in a wide variety of tsetse, their constitutive expression in adult fat body and midguts and their upregulation after immunogen challenge suggest they play an important role as a component of the immune system in tsetse.

Amino Acid Motifs↗
PubMed2004

Increase in peripheral blood mononuclear cell (PBMC)- and CD56+ cell-mediated killing of endometrial stromal cells by mycobacteria; a possible role in endometriosis immunotherapy?

BACKGROUND: Immunological therapies have shown promising results in the treatment of endometriosis. Mycobacteria are one of the most common immune therapies used in other diseases. We have assessed the effects of mycobacteria in altering the ability of peripheral blood mononuclear cells (PBMCs) and natural killer (NK) cells to kill endometrial stromal cells using an in vitro model. This may have implications in the immunotherapy of endometriosis. METHODS: Primary cultures of endometrial stromal cells were grown from female patients and PBMCs were extracted from healthy female volunteers. Effector cells (PBMCs or NK cells) were exposed to varying concentrations of mycobacteria before their ability to kill cultured endometrial cells was tested using a 51Cr-release assay. RESULTS: Treatment of effector cells with the Connaught Substrain Bacillus of Calmette and Guérin (BCG) led to increased killing of target cells by PBMCs and NK cells. The optimal concentration for treatment of effector cells with Connaught BCG was approximately 0.1 multiplicities of infection (m.o.i.). There was a trend towards increased killing after treatment with Pasteur BCG. CD56+ (NK) cells treated with BCG at 0.1 m.o.i. showed increased killing of target cells compared with untreated effector cells. CONCLUSIONS: Endometrial stromal cells are susceptible to killer cells activated by mycobacteria. This in vitro work suggests a possible role for mycobacteria in the immunotherapy of endometriosis.

Adult↗
PubMed2004

Anti-proliferative effect of mycobacteria, IFN-gamma and TNF-alpha on primary cultures derived from endometrial stroma: possible relevance to endometriosis?

PROBLEM: To assess the effects of mycobacteria and inflammatory cytokines on proliferation of endometrial stromal cells. An effect on endometrial stromal cell proliferation in vitro may suggest a similar effect on endometriotic cells in vivo. METHOD OF STUDY: Primary cultures of endometrial stromal cells were grown from female volunteers. Proliferation of cells was assessed by cell counting and incorporation of tritiated thymidine after exposure to mycobacteria or inflammatory cytokines. RESULTS: When assessed by cell counting, stromal cell growth was reduced following treatment with Connaught Bacillus of Calmette and Guérin (BCG) and Pasteur BCG: Mycobacterium smegmatis demonstrated a cytotoxic effect. Addition of the cytokines interferon (IFN)-gamma or tumour necrosis factor (TNF)-alpha at high concentrations led to a reduction in cell growth by 24 hr in two of three cell lines. A reduction in proliferation was also found when assessed by tritiated thymidine incorporation, which was statistically significant for Connaught BCG and M. smegmatis. CONCLUSIONS: Endometrial stromal cells are susceptible to the anti-proliferative effects of mycobacteria. The BCG and other mycobacteria are known immunomodulators in other disease conditions. Further work is required to assess whether these in vitro effects might translate into a useful therapy for endometriosis.

Cell Count↗
PubMed2004

The major hormone-specific discontinuous epitopes on human chorionic gonadotrophin.

The hormone human chorionic gonadotrophin (hCG) shows extensive sequence homology with LH. Thus, many of the antigenic epitopes on hCG are shared with LH, leading to immunological cross-reaction between these two hormones. Anti-fertility and anti-cancer vaccines based upon hCG should ideally target only the hCG-specific epitopes. The hCG-unique linear epitopes located in the C-terminal peptide of the hCG beta-chain are well characterised. In contrast, the hCG-specific discontinuous epitopes, termed beta1, beta6 and beta7, have remained poorly defined. By generating hCG beta-chain molecules containing single amino acid substitutions we have identified R10, N13, R60 and Q89 as being important in the formation of the beta1 epitope, with R60 providing a particularly dominant residue. We also show that the amino acid residue Q89 contributes to the beta7 epitope, whilst D61 plays a role in both the beta6 and beta7 epitopes.

Amino Acid Substitution↗
PubMed2002

A recombinant E. coli vaccine to promote MHC class I-dependent antigen presentation: application to cancer immunotherapy.

We have examined the potential of recombinant Escherichia coli expressing listeriolysin O (LLO) to deliver tumour antigens to dendritic cells (DCs) for cancer immunotherapy. Using OVA as a model tumour antigen, we have shown in murine DCs that E. coli expressing cytoplasmic LLO and OVA proteins can deliver the OVA K(b)-restricted epitope SIINFEKL for MHC class I presentation. In contrast, when E. coli expressing OVA alone were used, MHC class II presentation of the OVA 323-339 I-A(b)-restricted peptide was predominant. When injected in vivo, DCs pulsed with E. coli expressing LLO and OVA induced production of cytotoxic T-lymphocytes capable of lysing an OVA-expressing melanoma cell line (B16-OVA) and resulted in suppression of tumour growth following challenge with B16-OVA. Immunisation of mice by direct injection of E. coli LLO/OVA provided a more potent anti-tumour response, resulting in complete protection in 75% of mice. Injection of live bacteria was not necessary as immunisation with paraformaldehyde-fixed E. coli LLO/OVA provided an even stronger anti-tumour response against B16-OVA. Altogether, our data highlight the potential of this system as a novel and efficient strategy for tumour immunotherapy.

Animals↗
PubMed2001

The response of human dendritic cells to recombinant adenovirus, recombinant Mycobacterium bovis Bacillus Calmette Guerin and biolistic methods of antigen delivery: different induction of contact-dependant and soluble signals.

Dendritic cells (DCs) are the most potent antigen presenting cells for inducing T-cell immune responses. The ability to grow human DCs from monocyte precursors provides an abundant source of these cells, which can be modified in vitro to present antigens. Re-administration of modified DCs to patients as vaccines has been shown in some cases to induce immune responses against cancer and infectious disease. Gene delivery to DCs provides an intracellular source of antigen for efficient and persistent loading of major histocompatibility complex (MHC) class I molecules. The aim of this study was to use monocyte-derived DCs (MD-DCs) from healthy donors to compare in vitro gene transfer, mediated by adenovirus, M. bovis Bacillus Calmette Guerin (BCG) and biolistic delivery. Efficiency of transfection and effect on DC phenotype, allostimulatory capacity and cytokine secretion was investigated. Adenovirus and BCG both showed a comparable ability to transfect MD-DCs, whereas the biolistic delivery by gene gun was unsuccessful in the reporter gene delivery. BCG transfection promoted MD-DC maturation as is apparent in the surface phenotype, allostimulatory capacity and cytokine secretion from cells. In comparison, adenovirus and biolistic delivery had a reduced effect on MD-DCs although enhancement of co-stimulatory and MHC molecule expression occurred in the cells of some donors. Both BCG and adenovirus represent useful vectors for gene transfer to human DCs. The effect of BCG on DC maturation may provide additional signals for the induction of antigen-specific T-cell responses.

Adenoviruses, Human↗
PubMed2001

Expression of Interleukin-18, a Th1 cytokine, in human gastric mucosa is increased in Helicobacter pylori infection.

Interleukin-18 (IL-18), a cytokine that promotes Th1 responses, is processed to the active mature protein by caspase-1. The effects of Helicobacter pylori infection on gastric IL-18 and caspase-1 were examined. In antral mucosa, IL-18 mRNA expression was greater (P<.01) in H. pylori-positive (n=40) than in H. pylori-negative patients (n=29) with normal mucosa. Inactive precursor (24 kDa) and mature (18 kDa) IL-18 were present in antral biopsy specimens from uninfected and infected subjects. In corpus mucosa, mature IL-18 and a 16-kDa protein, corresponding to inactive IL-18, were present. Active caspase-1 p20 subunit was detected in antral and corpus mucosa of infected and uninfected subjects. These data show that, although H. pylori infection is associated with increased antral IL-18 mRNA expression, mature IL-18 protein and active caspase-1 p20 are present in mucosa of both H. pylori-infected and -uninfected subjects. IL-18 may have an important role in promoting gastric Th1 responses in H. pylori infection.

Adult↗
PubMed2001

Human dendritic cells genetically engineered to express a melanoma polyepitope DNA vaccine induce multiple cytotoxic T-cell responses.

PURPOSE: To assess the therapeutic potential of a melanoma polyepitope vaccine in human cells. Polyepitope DNA vaccines encoding T-cell epitopes have been demonstrated in murine systems to generate multiple cytotoxic T-cell responses to different antigens. Here, for the first time we demonstrate the ability of a melanoma polyepitope to stimulate lymphocytes from normal human donors to simultaneously generate multiple antigen-specific responses. EXPERIMENTAL DESIGN: Human dendritic cells (DC), transduced with a melanoma-polyepitope cDNA, were used to activate autologous lymphocytes from naïve donors as an in vitro model of DNA vaccination. Lymphocytes were primed with polyepitope or mock-transduced DC, boosted with peptide, then measured for antigen-specific cytotoxicity. RESULTS: Lymphocytes primed with polyepitope-transduced DC and boosted with peptide generated multiple cytotoxic responses. By contrast lymphocytes primed with mock-transfected DCs and boosted with peptide gave no specific cytotoxicity. However, when lymphocytes were repeatedly stimulated with polyepitope-transduced DCs immunodominance was seen with CTLs being generated to only one epitope, MART(27-35). CONCLUSIONS: We show in a human system that a melanoma polyepitope primes CTL to multiple epitopes. However, repeated stimulation by the polyepitope restricts the response to only the MART1 epitope. Thus, although polyepitope vaccines are an effective way of priming multiple naïve T-cell responses, continual boosting with polyepitope vaccines may, as a result of immunodominance, restrict the CTL. These findings have important implications for the use of DNA polyepitope vaccines in cancer immunotherapy.

Animals↗
PubMed2000

Role for CD40-CD40 ligand interactions in the immune response to solid tumours.

CD40-mediated interactions play an important role in the response to infections, transplantation, and cancer by affecting the development, activation, proliferation and differentiation of a variety of immune cells. In the current study we examined the role of CD40-mediated interactions in immune responses to bladder, pancreatic and breast carcinomas as well as melanoma cell lines using soluble human CD40L (rhCD40L) or anti-CD40 mAb in vitro. CD40 expression was readily detected in a large proportion of the cell lines and was augmented but not induced de novo by treatment with IFNgamma. Treatment of CD40-positive cell lines with rhCD40L or anti-CD40mAb enhanced cell surface expression of ICAM-1 and FAS and stimulated the production of IL-6, IL-8, GROalpha, GM-CSF and TNFalpha but not IL-4, IL-10, TGFbeta, MCP-1, RANTES, MIP-1beta, or IP-10. In addition, incubation of CD40+ tumour cell lines with immobilised rhCD40L or anti-CD40 mAb in vitro resulted in significant inhibition of proliferation and a corresponding decrease in viability. This CD40-mediated inhibition of cell growth was due, at least in part, to alterations in cell cycle and the induction of apoptosis. Transfection of CD40-negative tumour cell lines with the cDNA for CD40 conferred responsiveness to rhCD40L and anti-CD40 antibody. Finally, the presence of CD40 on the surface of carcinoma lines was found to be an important factor in the generation of tumour-specific T cell responses.

3T3 Cells↗
PubMed2000

Mechanisms of action of intravesical bacille Calmette-Guérin: local immune mechanisms.

The local immune response to mycobacteria is complex, but mycobacterial antigen presentation by phagocytes to T helper cells is the pivotal interaction. Bacille Calmette-Guérin (BCG) vaccination is associated with the development of antituberculosis immunity but not necessarily with antitumor immunity. Animal studies have shown that an intact host immune system is required for the antitumor activity of BCG. Immunosuppressed and, particularly, T cell-depleted individuals fail to respond to BCG immunotherapy. Clinical and laboratory evidence suggest that the antitumor activity is concentrated at the site of BCG administration, which reinforces the view that local immune mechanisms are responsible for this phenomenon.

Administration, Intravesical↗
PubMed2000

Diagnosis of malignant melanoma by general practitioners and hospital specialists.

The aim of this study was to audit all malignant melanomas confirmed histologically in the Scarborough Health District over six years, prompted by the continuing rise in incidence rate nationally and relatively high number of malignant melanomas excised by general practitioners (GPs) in this area. A total of 157 malignant melanomas were diagnosed (60% from females and 40% from males) over the six years; primary excisions being carried out by GPs (37%) and hospital specialists (63%). The clinical diagnosis of malignant melanoma was made in 9% of GP cases and 35% of the hospital specialist cases. However another 45.5% of GP cases, and 38% of hospital specialist cases were regarded as suspicious pigmented lesions clinically. The histological diagnosis was of superficial spreading malignant melanoma in 72% of the GP and 69% of the hospital specialist cases. Most of the GP melanomas were excised with a lateral margin of 2 mm or less (71%); around half of the hospital excisions had a margin of over 2 mm (49%). Most melanomas were 2 mm or less in depth (Breslow depth) in both the GP (81%) and hospital specialist (75%) series. Over the six year period (1993-98) the incidence of malignant melanomas has continued to rise, but Breslow depth at diagnosis has not changed significantly. It is therefore important to continue with early recognition of this condition by GPs in the first instance, reduction in its incidence being the long term goal. During five years of the study there were only 67 lesions thought clinically to be malignant melanoma (26 GP and 41 hospital specialist cases), but which proved to be benign histologically.

Clinical Competence↗
PubMed1999

Enhancing the immunotherapeutic potential of mycobacteria by transfection with tumour necrosis factor-alpha.

In an attempt to enhance the anti-tumour properties of mycobacteria we have developed recombinant forms of Mycobacterium smegmatis which express and secrete biologically active human tumour necrosis factor-alpha (TNF-alpha). This was achieved by transfecting M. smegmatis using shuttle plasmids incorporating the cDNA sequence for the human TNF-alpha mature peptide. In vitro experiments on a panel of human bladder tumour cell lines (EJ18, MGH-U1, RT4, RT112) indicate that our genetically modified mycobacteria are more effective than wild-type at inducing or up-regulating the expression of intracellular adhesion molecule-1 and the secretion of an array of proinflammatory cytokines [interleukin-1 (IL-1), IL-6, IL-8, granulocyte-macrophage colony-stimulating factor]. We have also demonstrated increased adhesion molecule and cytokine expression in response to mycobacteria transfected with vector containing no gene insert. However, this was not as pronounced as that observed following tumour cell stimulation by the TNF-alpha-transfected strain. In contrast, in three out of four tumour cell lines all M. smegmatis strains were found to down-regulate the secretion of the anti-inflammatory cytokine transforming growth factor-beta1. Our studies have also confirmed that M. smegmatis is a powerful inhibitor of bladder tumour cell growth and revealed that its antiproliferative potency is enhanced by transfecting with human TNF-alpha and, to a lesser extent, with vector alone. All M. smegmatis strains were effective in the activation of peripheral blood leucocyte cultures. However, no differences were observed in the ability of the TNF-alpha-transfected, mock-transfected and wild-type mycobacteria to induce tumour cell killing activity. These results suggest that the immunomodulatory effects of M. smegmatis can be enhanced by transfection with vectors which allow the secretion of human TNF-alpha, thus increasing mycobacterial immunotherapeutic potential.

Cloning, Molecular↗
PubMed1999

The biological action of choriogonadotropin is not dependent on the complete native quaternary interactions between the subunits.

Human CG (hCG) is a member of the glycoprotein hormone family characterized by a heterodimeric structure consisting of a common alpha-subunit noncovalently bound to a hormone-specific beta-subunit. The two subunits are highly intertwined and only the heterodimer is functional, implying that the quaternary structure is critical for biological activity. To assess the dependence of the bioactivity of hCG on the heterodimeric interactions, alpha- and beta-subunits bearing mutations that prevent assembly were covalently linked to form a single chain hCG. Receptor binding and signal transduction of these analogs were tested and their structural integrity analyzed using a panel of monoclonal antibodies (mAbs). These included dimer-specific mAbs, which react with at least four different epitope sites on the hormone, and some that react only with the free beta-subunit. We showed that there was significant loss of quaternary and tertiary structure in several regions of the molecule. This was most pronounced in single chains that had one of the disulfide bonds of the cystine knot disrupted in either the alpha- or beta-subunit. Despite these structural changes, the in vitro receptor binding and signal transduction of the single chain analogs were comparable to those of the nonmutated single chain, demonstrating that not all of the quaternary configuration of the hormone is necessary for biological activity.

Animals↗
PubMed1998

Epitopes of human chorionic gonadotropin and their relationship to immunogenicity and cross-reactivity of beta-chain mutants.

PROBLEM: Human chrionic gonadotropin (hCG) is a placental glycoprotein hormone, a heterodimeric molecule, consisting of alpha and beta chains. It induces the synthesis of progesterone, which is essential for the maintenance of the fertilized egg. Antibodies directed against hCG can, therefore, prevent pregnancy and serve as a vaccine. hCG belongs to the glycoprotein hormone family and shares the alpha chain with the other members. The beta chain is a hormone-specific subunit that is unique to hCG, but still possesses 85% amino acid homology with the beta chain of luteinizing hormone (LH), which means that prolonged immunization with hCG produces antibodies that cross-react with LH. METHOD OF STUDY: We have taken an approach involving the mutation of beta hCG to eliminate cross-reactive epitopes without affecting the natural folding of the polypeptide chain and thus the unique beta hCG-specific epitopes. RESULTS: Several mutants have been constructed that have maintained the binding to hCG-specific monoclonal antibodies (mAbs) but have lost the ability to bind to a panel of LH cross-reactive mAbs. To investigate the immunogenicity of selected mutants, mice were immunized with expression plasmid DNA, containing the gene for wild-type beta hCG and two mutants: mutant 3, with four amino acid substitutions (68 Arg-->Glu; 74 Arg-->Ser; 75 Gly-->His; 79 Val-->His), and mutant 7, with a single amino acid substitution (68 Arg-->Glu). CONCLUSIONS: Although both mutants were able to elicit antibody responses in at least some animals, the levels were less than those seen with the wild-type beta hCG DNA, and there seems still to be a residual cross-reactivity with LH. Attempts to improve the immunogenicity of the mutants and to further modify the sequence to remove the cross-reactivity are currently underway.

Animals↗