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J L Hughes

Publications and source records attributed to J L Hughes.

At least 19 recordsLinked to original sources
PubMed1995

Interleukin 12 suppresses autoantibody production by reversing helper T-cell phenotype in hepatitis B e antigen transgenic mice.

Helper T (Th) cells are classified as Th1 or Th2 cells by virtue of cytokine secretion and function as mediators of cellular or humoral immunity, respectively. Cytokines also regulate the differentiation of Th cells. For example, interleukin (IL)-12 promotes Th1 and suppresses Th2 cell development, suggesting that IL-12 may be useful therapeutically in Th2-mediated autoimmune and allergic disorders. Therefore, the effect of systemic IL-12 treatment on in vivo autoantibody synthesis in hepatitis B e antigen (HBeAg)-expressing transgenic mice, which is dependent on self-reactive Th2 cells, was examined. Low-dose IL-12 significantly inhibited autoantibody production by shifting the Th2-mediated response toward Th1 predominance. Additionally, previous studies suggest that a predominance of HBeAg-specific Th2-type cells may contribute to chronicity in hepatitis B virus infection. Therefore, IL-12 may also prove beneficial in modulating the HBeAg-specific Th response to favor viral clearance in chronic hepatitis B virus infection.

Animals↗
PubMed1995

The hepatitis nucleocapsid as a vaccine carrier moiety.

The "carrier effect," defined as the provision of T cell recognition sites physically linked to B cell epitopes in order to provide Th cell function for antibody synthesis, is well known. Peptides, proteins, and more recently particulate protein antigens have been used for this purpose. The hepatitis B core antigen represents a highly immunogenic antigen in humans as well as in experimental animal models. Studies in mice have provided insight into this enhanced immunogenicity. For example, HBcAg directly activates B cells (i.e., T cell independence), HBcAg elicits strong T cell responses, and HBcAg is efficiently processed and presented by antigen presenting cells (APCs). These characteristics suggested that HBcAg may be an ideal carrier moiety for B cell epitopes requiring additional Th cell function. Therefore, a number of HBV and non-HBV B cell epitopes have been chemically linked or fused by recombinant methods to HBcAg as a method to increase immunogenicity with significant success. We have designed bacterial expression vectors that allow insertion of heterologous B cell epitopes at various positions within HBcAg particles and permit efficient purification of hybrid HBcAg particles. Studies of positional effects have demonstrated that an internal insertion into a dominant HBcAg-specific B cell site represents a superior location for enhanced antibody production. Immunogenicity studies have been extended to protection against experimental challenge in several systems. For example, a malaria CS repeat sequence derived from P. berghei was inserted into HBcAg at the internal site, and purified hybrid HBcAg/CS particles were highly immunogenic and protected 100% of experimentally challenged BALB/c mice. This system has also been exploited for purposes of oral vaccination by expressing genes coding for hybrid HBcAg particles in live, avirulent vaccine strains of Salmonella species.

Administration, Oral↗
PubMed1995

Characterization of self-reactive T cells that evade tolerance in hepatitis B e antigen transgenic mice.

Previous studies of hepatitis B e antigen (HBeAg)-expressing transgenic (Tg31e) mice have indicated that the degree of T cell tolerance was epitope specific. For example, T cells specific for residues 120-131 of HBeAg are profoundly tolerant, whereas a proportion of T cells specific for residues 129-140 escape tolerance induction in B10. S x B10-Tg31e mice. To understand the basis for differential tolerance towards two T cell sites on the same self antigen, we characterized T cell recognition of HBeAg by primary T cells and T cell hybridomas derived from HBeAg-Tg and non-Tg mice. The self-reactive T cells surviving in B10-Tg31e mice exhibited a unique fine specificity, albeit still focussed on HBeAg residues 129-140, which could be distinguished from the HBeAg-specific T cell repertoire in non-Tg B10 mice. Further, self-reactive T cells were comprised predominantly of Th2-type cells that preferentially evaded tolerance induction as compared to their Th1 counterparts. Because HBeAg may act as a tolerogen during the vertical transmission of chronic hepatitis B virus (HBV) infection, these results suggest that a predominance of HBeAg-specific Th2 cells expressing a limited repertoire may influence the initiation or the maintenance of the HBV chronic carrier state.

Animals↗
PubMed1995

Preferential recognition of hepatitis B nucleocapsid antigens by Th1 or Th2 cells is epitope and major histocompatibility complex dependent.

Regulatory T-helper (Th) cells have been categorized into two functional subsets, Th1 and Th2 cells, which produce distinct lymphokines. In general, Th1 cells mediate cellular immune responses and Th2 cells mediate humoral immunity. Recent serological studies suggest that the Th1-Th2 balance may be relevant in acute and chronic hepatitis B virus (HBV) infections. The purpose of this study was to determine the potential of the nucleocapsid antigens (Ags) (hepatitis B core and e Ags [HBc/eAg]) of HBV to preferentially elicit either a Th1 or a Th2 dominant response. For this purpose, H-2 congenic B10.S and B10 mice were immunized with HBc/eAg, and Ag-specific T-cell proliferative responses, T-cell helper function, and T-cell cytokine production were analyzed. The results indicated that B10.S mice preferentially develop a Th1-like response whereas B10 mice preferentially develop a Th2-like response after immunization with HBc/eAg. Furthermore, the preferential Th1 and Th2 response patterns were reproduced when 12-residue peptides representing the dominant HBc/eAg-specific T-cell sites for B10.S (peptide 120-131) and B10 (peptide 129-140) mice were used as immunogens. Therefore, the combination of the T-cell site recognized and the major histocompatibility complex restricting element can in large part determine the Th phenotype of the HBc/eAg-specific T-cell response. Other factors that influenced Th phenotype were the presence of exogenous cytokines, Ag structure, and tissue distribution.

Amino Acid Sequence↗
PubMed1995

Orthopedic management of knee dislocations. Comparison of surgical reconstruction and immobilization.

Thirty-nine patients with 43 complete knee dislocations managed between 1973 and 1990 were reviewed retrospectively to compare the results of surgical reconstruction to nonreconstructive treatment of these injuries. The average patient age was 34 years and the average follow-up was 5 years (range: 1 to 18 years). Patients were evaluated by physical examination and the Lysholm knee scoring scale. Fourteen knees (33%) sustained popliteal vessel injury and five (9%) required amputation. Peroneal and tibial nerve injuries involved 13 knees (30%). Twenty-five of 39 patients (64%) sustained other associated fractures. Three patients sustained associated paraplegia and nine were lost to follow-up, leaving 25 knees available for follow-up examination. Thirteen knees were managed by surgical reconstruction of their ligamentous injuries and 12 were managed by nonreconstructive means. The surgically treated group had an average Lysholm knee score of 80 compared with the nonreconstructive group with an average score of 66. Average range of motion of was 106 degrees for the surgical group and 95 degrees for the nonreconstructive group. Despite the severity of the initial injury and the potential presence of vascular/nerve injuries, surgical reconstruction provides superior results to immobilization alone in the management of these injuries.

Adolescent↗
PubMed1994

Soluble CTLA-4 can suppress autoantibody production and elicit long term unresponsiveness in a novel transgenic model.

Activation of Ag-specific T cells often requires costimulatory signals in addition to the primary signal mediated through the TCR. The CD28-B7 interaction provides one important costimulatory signal. Previous studies have shown that a soluble CD28 homologue, CTLA4lg, binds B7 with high affinity and can inhibit CD28-B7-mediated costimulation in vitro and in vivo. In this study we examined the ability of soluble human CTLA4lg to inhibit autoantibody production in vivo. For this purpose we used a novel transgenic (Tg) model of autoantibody production. Hepatitis B eAg-expressing Tg mice can be induced to produce autoantibody to the circulating autoantigen (HBeAg) by the injection of a T cell recognition site that fails to elicit T cell tolerance in these mice. Autoimmunity in this model is quantitative because serum autoantibody and autoantigen concentration are inversely correlated and easily measurable by ELISA. In this system a single regimen of CTLA4lg treatment significantly suppressed primary autoantibody production and variably led to long term unresponsiveness. Furthermore, in vivo treatment with CTLA4lg inhibited both T cell activation and T cell-B cell interactions.

Abatacept↗
PubMed1994

Extrathymic expression of the intracellular hepatitis B core antigen results in T cell tolerance in transgenic mice.

We previously developed a transgenic (Tg) murine lineage (B10.S-Tg31e), which secretes the hepatitis B e Ag (HBeAg) into the serum at a concentration of 10 ng/ml. This serum concentration was sufficient to render B10.S-Tg31e mice functionally tolerant at the T cell but not B cell level. To determine the tolerogenic potential of an intracellular form of this Ag, namely the hepatitis B core Ag (HBcAg), expressed outside the thymus, the B10.S-Tg10c lineage was developed. In B10.S-Tg10c mice the HBcAg is expressed as an intracellular "self"-Ag predominantly in the liver, and cannot be detected in the serum, the thymus or in nonthymic lymphoid tissue. Despite the liver-specific and intracellular location of this transgenic self-protein, B10-STg10c mice demonstrate a significant degree of HBcAg-specific T cell tolerance at the level of T cell proliferation. Similarly, in vivo anti-HBc antibody production after HBcAg immunization is significantly reduced as compared with non-Tg littermate controls. No spontaneous anti-HBc antibody is produced in B10.S-Tg10c mice, however, adoptive transfer of HBcAg-specific T cells from non-Tg B10.S mice elicits anti-HBc specific "autoantibody" production. Interestingly, antibodies with specificity for the HBeAg as well as the HBcAg are produced. Antibody production in B10.S-Tg10c mice adoptively transferred with T cells indicates that sufficient native HBcAg can gain access to the extracellular compartment to engage HBcAg-specific B cells that are clearly not tolerant in this model. No liver injury was observed as a consequence of HBcAg expression, even in B10.S-Tg10c mice adoptively transferred with HBcAg-specific T cells. Unless HBcAg is unique in this regard, these results suggest that organ-specific, intracellular self-Ag may be released during normal cell turnover in sufficient concentrations to elicit systemic T cell tolerance. B10.S-Tg10c mice also serve as an immunologic model system for chronic infection with the HBeAg-negative mutant of the hepatitis B virus.

Animals↗
PubMed1994

Pitfalls in the prenatal diagnosis of peroxisomal beta-oxidation defects by chorionic villus sampling.

Variability in the level of expression of very long chain fatty acids (VLCFAs) is documented in cultured chorionic villus (CV) cells derived from two fetuses, one at risk for an unusual peroxisomal fatty acid beta-oxidation defect, and the other at risk for the X-linked form of adrenoleucodystrophy (ALD). Cells from early subcultures of chorionic cells from both cases gave normal values for VLCFA ratios. The results for the fetus at risk for the beta-oxidation defect were interpreted to indicate that the fetus was not affected; however, at birth, the infant was clinically and biochemically affected. In the case of the fetus at risk for X-linked ALD, although VLCFAs were normal in subculture 1, the levels of these fatty acids increased dramatically in subculture 3, suggesting an abnormal fetus. Termination of the pregnancy and subsequent biochemical and morphological follow-up confirmed that the fetus was indeed affected by ALD.

Adrenal Cortex↗
PubMed1993

Establishment of a normal range of morphometric values for peroxisomes in paediatric liver.

The size and number of hepatic peroxisomes was investigated in 16 control paediatric liver biopsies from patients ranging in age from 3 months to 18 years one fetal liver specimen and one paediatric autopsy liver. The area, diameter, volume density (Vv), numerical density (Nv) and surface density (Sv) of the peroxisomes was recorded using randomly selected electron micrographs. The mean diameter of peroxisomes in control paediatric liver was 0.56 microns, the mean Vv was 1.67%, the mean Nv was 0.125 per micron+3 and the mean Sv was 0.161 per micron. No correlation was found between the size and number of hepatic peroxisomes and the age or sex of the patient. Peroxisomes in the fetal liver were smaller than those in biopsy tissue and had a mean diameter of 0.42 micron. Peroxisomes were identified in autopsy tissue and were enlarged with a mean diameter of 0.75 micron, most probably due to post-mortem swelling. A range of morphometric values in paediatric liver has now been established.

Adolescent↗
PubMed1993

Morphometry of peroxisomes and immunolocalization of peroxisomal proteins in the liver of patients with generalised peroxisomal disorders.

Hepatic peroxisomes were studied by morphometric and immunocytochemical techniques in control patients and in four Zellweger syndrome patients, two infantile Refsum's (IRD) patients, one neonatal adrenoleukodystrophy (NALD) patient, and three patients with peroxisomal disorders (PD) which do not fit any currently recognised classification, but have disorders involving a defect in peroxisomal biogenesis. Peroxisomes which were ultrastructurally abnormal and greatly reduced in size and/or number were found in two of the Zellweger syndrome patients, and the NALD and IRD patients. There was variation in their numerical density ranging from none at all in two of the Zellweger syndrome patients to normal numbers in the IRD patients. In most patients there was a decrease in the immunolabelling of catalase over the peroxisomes. In the Zellweger syndrome and NALD patients, the small, abnormal peroxisomes did not label for any of the beta-oxidation proteins. The IRD patients and the PD patients however, were heterogeneous with respect to beta-oxidation labelling. The ultrastructural heterogeneity of peroxisomes in these peroxisomal disorders patients indicates there may be genotypic differences between the major groups and also within each group. The common factor in all the patients in this study where peroxisomes were present was the presence in the hepatic peroxisomes of an electron dense centre which did not label immunocytochemically for catalase or the beta-oxidation enzymes. This electron dense centre may indicate a structural abnormality in the peroxisomes in these patients.

Acetyl-CoA C-Acetyltransferase↗
PubMed1992

Ultrastructure and immunocytochemistry of hepatic peroxisomes in rhizomelic chondrodysplasia punctata.

Peroxisomes were studied in the liver of two rhizomelic chondrodysplasia punctata patients using electron microscopy and catalase cytochemistry. Immunoelectron microscopy was carried out on the liver of one of these patients using antibodies to catalase, acyl-CoA oxidase, bifunctional protein, 3-ketoacyl-CoA thiolase and a 68 kDa peroxisomal membrane protein, in conjunction with protein-A colloidal gold. Moderately to markedly enlarged, flocculent peroxisomes were found in both patients. In one patient they were very heterogeneous with regard to the number per hepatocyte. The peroxisomes had very low levels of catalase as indicated by cytochemistry and immunocytochemistry. The three beta-oxidation enzymes were localised normally within the peroxisomes. The 68 kDa membrane protein was localised to the peroxisomal membranes. Some extra membrane loops were also identified using this antibody.

3,3'-Diaminobenzidine↗
PubMed1992

The position of heterologous epitopes inserted in hepatitis B virus core particles determines their immunogenicity.

The nucleocapsid (HBcAg) of the hepatitis B virus (HBV) has been suggested as a carrier moiety for vaccine purposes. We investigated the influence of the position of the inserted epitope within hybrid HBcAg particles on antigenicity and immunogenicity. For this purpose, genes coding for neutralizing epitopes of the pre-S region of the HBV envelope proteins were inserted at the amino terminus, the amino terminus through a precore linker sequence, the truncated carboxy terminus, or an internal site of HBcAg by genetic engineering and were expressed in Escherichia coli. All purified hybrid HBc/pre-S polyproteins were particulate. Amino- and carboxy-terminal-modified hybrid HBc particles retained HBcAg antigenicity and immunogenicity. In contrast, insertion of a pre-S(1) sequence between HBcAg residues 75 and 83 abrogated recognition of HBcAg by 5 of 6 anti-HBc monoclonal antibodies and diminished recognition by human polyclonal anti-HBc. Predictably, HBcAg-specific immunogenicity was also reduced. With respect to the inserted epitopes, a pre-S(1) epitope linked to the amino terminus of HBcAg was not surface accessible and not immunogenic. A pre-S(1) epitope fused to the amino terminus through a precore linker sequence was surface accessible and highly immunogenic. A carboxy-terminal-fused pre-S(2) sequence was also surface accessible but weakly immunogenic. Insertion of a pre-S(1) epitope at the internal site resulted in the most efficient anti-pre-S(1) antibody response. Furthermore, immunization with hybrid HBc/pre-S particles exclusively primed T-helper cells specific for HBcAg and not the inserted epitope. These results indicate that the position of the inserted B-cell epitope within HBcAg is critical to its immunogenicity.

Animals↗
PubMed1991

Identification of a catalase-negative sub-population of peroxisomes induced in mouse liver by clofibrate.

The peroxisomal compartment in mouse liver was investigated using rate sedimentation of liver subfractions on sucrose density gradients. Treatment of mice with clofibrate, a hypolipidemic agent and peroxisome proliferator, resulted in the formation of small particles which were devoid of catalase and urate oxidase, but which were identified as peroxisomal on the basis of content of the clofibrate-induced peroxisomal beta-oxidation enzymes (fatty acyl-CoA oxidase, hydratase/dehydrogenase bifunctional protein, and thiolase) and the 68 kDa peroxisomal integral membrane protein. Immunoelectron microscopy confirmed the membrane-bound organellar nature and enzyme composition of these particles. These particles were absent in normal mice, and were increased to a maximal level within 2 days of clofibrate treatment. These data have been taken as indicative of a role of these particles in the mechanism of drug-induced peroxisome proliferation.

Acetyl-CoA C-Acetyltransferase↗
PubMed1991

Autoantibody production in hepatitis B e antigen transgenic mice elicited with a self T-cell peptide and inhibited with nonself peptides.

Studies in hepatitis B e antigen (HBeAg)-expressing transgenic mice indicate that self tolerance to two T-cell determinants on the same transgenic self molecule can differ markedly. The dominant T-cell site on HBeAg is tolerogenic, whereas a proportion of T cells recognizing a second T-cell site evade tolerance induction, persist in the periphery, and can be activated in vivo by a single injection of a 12-residue T-cell self peptide. The self-reactive T cells mediate in vivo autoantibody production sufficient to neutralize detection of the autoantigen in serum. Furthermore, autoantibody production can be inhibited by nonself peptides that compete with the self peptide for binding to major histocompatibility complex molecules. This model illustrates that T cells specific for an immunogenic T-cell site on a nonsequestered autoantigen can escape tolerance induction and, more importantly, can mediate autoreactivity in vivo. Furthermore, these results suggest that synthetic T-cell sites may be useful as immunotherapeutic agents for the purpose of circumventing nonresponse to HBeAg during persistent hepatitis B virus infection.

Amino Acid Sequence↗
PubMed1990

Importance of subtype in the immune response to the pre-S(2) region of the hepatitis B surface antigen. I. T cell fine specificity.

Previous studies of murine T cell recognition of the pre-S(2) region of the hepatitis B surface Ag (HBsAg) identified high (H-2b,d,q), intermediate (H-2s,k), and low to nonresponder (H-2f) haplotypes. However, these studies utilized the y subtype of HBsAg. The purpose of this study was to examine the influence of viral subtype on T cell recognition of the pre-S(2) region and to identify specific T cell recognition sites in a panel of H-2 congenic strains. Immunization with pre-S(2) containing HBsAg particles of the d and y subtypes indicated that T cell recognition of the pre-S(2) region is predominantly subtype-specific in murine strains of eight different H-2 haplotypes. Furthermore, the B10.M strain (H-2f) classified as a T cell nonresponder to the y subtype of the pre-S(2) region responds efficiently to the d subtype, indicating that pre-S(2) responder status can be subtype-dependent as well as subtype-specific. Studies using a truncated pre-S(2) polypeptide and synthetic peptides illustrated that the C-terminal sequence (p148-174) of the pre-S(2) region is the dominant focus of T cell recognition in multiple murine strains. Specifically, 17 distinct T cell recognition sites were defined within the C-terminal half of the pre-S(2) region. The fine specificity of T cell recognition of the pre-S(2) region was dependent on the H-2 haplotype of the responding strain. T cell recognition of all 17 sites was subtype specific, which is consistent with the fact that the C-terminal sequence is highly polymorphic between the d and y subtypes of the pre-S(2) region. Lastly, it was shown that the ability of synthetic peptides to elicit T cells cross-reactive with the native pre-S(2) region was variable and depended on the nature of the immunizing peptide. The pre-S(2)-containing HBsAg vaccines currently in clinical trials are composed of ra single subtype, either d or y. The results of this study suggest that both subtypes should be incorporated to increase the frequency of T cell responders to the pre-S(2) region, and to insure Th cell memory relevant to infection with hepatitis B virus of either the d or y subtypes.

Amino Acid Sequence↗
PubMed1990

Importance of subtype in the immune response to the pre-S(2) region of the hepatitis B surface antigen. II. Synthetic Pre-S(2) immunogen.

One purpose of this study was to examine the influence of viral subtype on in vivo antibody production to the pre-S(2) region of the hepatitis B surface Ag. Immunization with hepatitis B surface Ag particles containing the pre-S(2) region of the d or y subtypes identified the B10.M (H-2f) strain as an antibody nonresponder to the pre-S(2) and S regions after immunization with the y subtype, but as an antibody responder to the pre-S(2) and S regions after immunization with the d subtype. Both the S region and pre-S(2) region-specific antibody responses emanated from pre-S(2)/d-specific Th cell function because B10.M mice are T cell nonresponsive to the S region of both subtypes. Although responder/nonresponder status of the B10.M strain was dependent on the pre-S(2) subtype used for immunization, the anti-pre-S(2) antibody produced was totally cross-reactive on both subtypes. This is consistent with the conserved nature of the dominant pre-S(2) antibody-binding site and the highly polymorphic nature of the pre-S(2) sequence that represents the focus of T cell recognition. These data suggest that, to fully benefit from the inclusion of pre-S(2) region sequences, third generation hepatitis B virus vaccines should contain both the d and y subtype sequences of the pre-S(2) region to increase the frequency of pre-S(2) and S-specific antibody responses and to insure Th cell memory relevant to both viral subtypes. A second purpose of this study was to "design" a synthetic pre-S(2) immunogen based on combining the dominant B and T cell recognition sites into a single peptide. A composite peptide consisting of the dominant T cell recognition sequence p151-174 positioned N-terminal to the dominant B cell site p133-143 (i.e., p151-174(133-143] yielded an effective pre-S(2) synthetic immunogen. Interestingly, the orientation of the T and B cell determinants and the context of the T cell site within the larger composite peptide influenced both antibody fine specificity and T cell fine specificity.

Amino Acid Sequence↗
PubMed1990

Pathology of hepatic peroxisomes and mitochondria in patients with peroxisomal disorders.

The morphology of hepatic peroxisomes in five patients with metabolic disorders believed to be due to inherited defects of peroxisomal function or biogenesis is described. Electron microscopy and cytochemical staining for catalase were used to identify peroxisomes in two boys with infantile Refsum's disease (IRD), a girl with autopsy confirmed neonatal adrenoleukodystrophy (NALD), and two boys with pseudo-Zellweger syndrome (PZS). In the patients with IRD and NALD hepatic peroxisomes were significantly reduced in size and number and contained electron dense centres. In the liver of the patients with PZS the peroxisomes were enlarged. Morphologically abnormal peroxisomes were also detected in autopsy tissue from one boy with PZS using electron microscopy. Lamellar-lipid inclusions and mitochondria with crystalline inclusions and/or abnormal cristae are also described in two patients, one with IRD, the other with NALD.

Adrenoleukodystrophy↗