Claude Daniel

A BASIS FOR ALLOREACTIVITY : MHC HELICAL RESIDUES BROADEN PEPTIDE RECOGNITION BY THE TCR

The high frequency of alloreactive T cells is a major hindrance for transplantation; however, the molecular basis for alloreactivity remains elusive. We examined the I-Ep alloreactivity of a well-characterized Hb(64-76)/I-Ek-specific murine T cell. Using a combinatorial peptide library approach, we identified a highly stimulatory alloepitope mimic and observed that the recognition of the central TCR contact residues (P3 and P5) was much more flexible than that seen with Hb(64-76)/I-Ek, but still specific. Therefore, alloreactive T cells can recognize a self-peptide/MHC surface; however, the allogeneic MHC molecule changes the recognition requirements for the central region of the peptide, allowing a more diverse repertoire of ligands to be recognized.

Structural and functional impairment of the hypothalamo-pituitary-interrenal axis in fish exposed to bleached kraft mill effluent in the St Maurice River, Quebec

The effects of bleached kraft mill effluent (BKME) on blood cortisol levels and the morphology of the pituitary-interrenal axis were investigated in two species of teleost fish, the northern pike, Esox lucius, and the yellow perch, Perca flavescens, sampled upstream and downstream from a pulp and paper mill on the St Maurice River, Quebec. Fish were acutely stressed by a standardized capture and sampling protocol at both sites, and their ability to elevate blood cortisol levels in response to the capture stress was compared. Blood cortisol levels in fish from the upstream site (>100 ng/ml plasma) were higher than the levels in fish from the BKME site, and the pituitary corticotropes and the interrenal steroidogenic cells of the upstream fish were larger and had larger nuclei compared with cells from the downstream fish. The low blood cortisol levels in fish exposed to BKME were correlated to cellular atrophy within the hypothalamo-pituitary-interrenal (HPI) axis. The reduced ability to elevate blood cortisol in response to an acute stress may be an endocrine dysfunction occuring in fish chronically exposed to chemical stressors in their environment

Effects of acute exposure to mercury chloride and methylmercury on plasma cortisol, T3, T4, glucose and liver glycogen in rainbow trout (Oncorhynchus mykiss)

Abstract Juvenile rainbow trout (Oncorhynchus mykiss) were exposed to mercury chloride HgCl2 (28 and 112 μg/l Hg2+), and to methylmercury chloride CH3HgCl (6, 12 and 24 μg/l Hg) for 4, 72 and 168 h to determine the effects of sublethal doses of these compounds on the hypothalamo-pituitary-interrenal and the hypothalamo-pituitary-thyroid axes. Exposure to both mercurial compounds significantly increased plasma cortisol, plasma thyroxine (T4) and plasma glucose levels. Similar trends were observed in plasma triiodothyronine (T3) levels. A decrease in liver glycogen reserves was detected after 1 week of exposure to 6 μg/l CH3HgCl. Our results indicate that both mercurial compounds stimulate the pituitary-interrenal and the pituitary-thyroid axis and modify the carbohydrate metabolism in juvenile rainbow trout, and that the organic mercury CH3Hg+ is a more potent chemical stressor than the inorganic Hg2+.

Effects of acute and subacute exposures to cadmium on the interrenal and thyroid function in rainbow trout, Oncorhynchus mykiss

Juvenile rainbow trout, Oncorhynchus mykiss, were exposed to 0.4, 0.8 and 2.4 mg Cd 1−1 (CdCl2 in water) for 2, 4, 24, and 96 h and to 0.4 and 0.8 mg Cd 1−1 for 1 week to investigate the effects of short term exposures to Cd on the interrenal and thyroid function. Acute (2–4 h) exposure increased both plasma cortisol and T4 levels but had no effect on plasma T3. Following a subacute exposure (1 week), plasma cortisol levels of the exposed fish increased compared with controls, plasma T4 levels decreased and plasma T3 levels remained stable. An increase in plasma glucose and a decrease in liver glycogen was detected in fish exposed for 1 week, no effect on weight gain was found. Short term exposures to sublethal concentrations of Cd induce changes in the endocrine status and carbohydrate metabolism of the fish.

Anti-Sa antibodies and antibodies against cyclic citrullinated peptide are not equivalent as predictors of severe outcomes in patients with recent-onset polyarthritis

The prognostic value of two antibodies targeting citrullinated antigens, anti-Sa and anti-cyclic citrullinated peptide (CCP), present at inclusion, was evaluated prospectively in a cohort of 165 consecutive patients with recent-onset or early polyarthritis (EPA) followed for up to 30 months. Patients were treated according to current Good Clinical Practice standards. Predefined outcomes were severe arthritis and persistent arthritis. At inclusion, a median of 3 months after disease onset, 133 (81%) patients fulfilled at least four American College of Rheumatology criteria for rheumatoid arthritis and 30 (18%) had erosive changes on radiographs of hands and feet. Disease-modifying anti-rheumatic drugs were used in close to 80% of the patients at 30 months. Joint damage increased linearly over time, whereas disease activity declined markedly and remained low at each follow-up. Autoantibodies were identified in 76 (46%) patients: rheumatoid factor (RF) in 68 (41%), anti-CCP in 53 (33%), and anti-Sa in 46 (28%). All three antibodies were correlated, but anti-Sa antibodies best predicted severity at 18 and 30 months. RF and anti-CCP performed less well. For both outcomes, anti-Sa alone performed better than any combination of antibodies. The presence of any autoantibody identified about 50 to 60% of the patients with poor outcomes. In multivariate analysis, anti-Sa (odds ratio (OR) 8.83), the presence of erosions at inclusion (OR 3.47) and increasing age (OR 1.06/year) were significantly associated with severity, whereas RF and anti-CCP were not significant predictors. Persistent arthritis was present in up to 84% of patients; autoantibodies were specific but poorly sensitive predictors of this outcome. We conclude that assays for antibodies against citrullinated antigens differ in their ability to predict poorer outcomes in patients with EPA. In our EPA cohort treated in accordance with current standards, detection of anti-Sa but not of RF or anti-CCP antibodies, in combination with clinical and radiological variables present at the first encounter, allowed the identification of a subgroup of EPA patients suffering more rapid and more severe joint damage over 30 months.

Antiperlecan antibodies are novel accelerators of immune-mediated vascular injury.

Acute vascular rejection (AVR) is characterized by immune‐mediated vascular injury and heightened endothelial cell (EC) apoptosis. We reported previously that apoptotic ECs release a bioactive C‐terminal fragment of perlecan referred to as LG3. Here, we tested the possibility that LG3 behaves as a neoantigen, fuelling the production of anti‐LG3 antibodies of potential importance in regulating allograft vascular injury. We performed a case–control study in which we compared anti‐LG3 IgG titers in kidney transplant recipients with AVR (n = 15) versus those with acute tubulo‐interstitial rejection (ATIR) (n = 15) or stable graft function (n = 30). Patients who experienced AVR had elevated anti‐LG3 titers pre and posttransplantation compared to subjects with ATIR or stable graft function (p < 0.05 for both mediators). Elevated pretransplant anti‐LG3 titers (OR: 4.62, 95% CI: 1.08–19.72) and pretransplant donor‐specific antibodies (DSA) (OR 4.79, 95% CI: 1.03–22.19) were both independently associated with AVR. To address the functional role of anti‐LG3 antibodies in AVR, we turned to passive transfer of anti‐LG3 antibodies in an animal model of vascular rejection based on orthotopic aortic transplantation between fully MHC‐mismatched mice. Neointima formation, C4d deposition and allograft inflammation were significantly increased in recipients of an ischemic aortic allograft passively transferred with anti‐LG3 antibodies. Collectively, these data identify anti‐LG3 antibodies as novel accelerators of immune‐mediated vascular injury and obliterative remodeling.

ICAM-1 isoforms: specific activity and sensitivity to cleavage by leukocyte elastase and cathepsin G

The extracellular moiety of ICAM‐1 consists of five Ig‐like domains, the first and third domains mediating adhesion to integrin ligands. The ICAM‐1 gene, however, gives rise to the expression of five alternative splice variants containing two, three, or four Ig‐like domains. In this work, we have investigated whether the rearrangement of the architecture of ICAM‐1 affects its structural properties and function. We showed that, in contrast to the common form, all alternative isoforms of ICAM‐1 were susceptible to cleavage by leukocyte elastase and cathepsin G. We found that the length of an isoform did not influence the susceptibility to proteolysis. The molecular diversity provided by the skipping of entire Ig domains and the level of expression on the APC, however, significantly influenced their ability to potentiate the proliferation of T cells. Finally, we found that the expression of minor ICAM‐1 isoforms encoding the third Ig‐like domains was sufficient to sustain neutrophil infiltration in the liver and confer exon‐5‐targeted ICAM‐1‐deficient mice susceptibility to LPS‐induced septic shock. These findings not only demonstrate that ICAM‐1 isoforms are fully functional, but support the concept that alternative RNA splicing in the Ig superfamily may fulfill distinct roles during the development of the immune response.

Protection from lethal coronavirus infection by affinity-purified spike glycoprotein of murine hepatitis virus, strain A59

Abstract Murine hepatitis viruses provide excellent animal models for the study of virus-induced diseases of the central nervous system and gastrointestinal tract. Several studies have indirectly provided evidence that the spike glycoprotein (S) of these coronaviruses bears determinants for pathogenesis and the induction of protective immunity. In order to directly evaluate the immunogenicity of this protein, it was purified by affinity chromatography with an in vitro neutralizing and in vivo protective monoclonal antibody which immunoprecipitated the 180-kDa spike glycoprotein of the neurotropic A59 strain of murine hepatitis virus (MHV-A59). Mice immunized twice with approximately 1 μg of purified S in Freunds adjuvant developed high titers of neutralizing and fusion inhibiting antibodies, even though the protein was at least partially denaturated after elution from the affinity column. Moreover, these mice were protected from lethal encephalitis when challenged intracerebrally with 10 LD50 of MHV-A59. This study provides a direct demonstration of the importance of the coronavirus spike glycoprotein in the induction of a protective immune response.

In vitro response to ACTH of the interrenal tissue of rainbow trout (Oncorhynchus mykiss) exposed to cadmium

Plasma cortisol levels and responsiveness of the interrenal tissue to ACTH were determined in rainbow trout (Oncorhynchus mykiss) subjected to acute and subchronic exposures of cadmium (Cd) in the water. Plasma cortisol levels were significantly increased after 2 days of exposure to 1 m gC d l 1 . They decreased to basal levels after 7 and 14 days of exposure. They significantly increased again after 30 days of exposure. The responsiveness of the interrenal tissue to ACTH was evaluated in vitro by monitoring the secretion of cortisol after stimulation of the head kidneys with 10 7 M of ACTH for 10 min in perifusion. The responsiveness to ACTH of the interrenal tissue of fish exposed to 1 m gC d l 1 for 2, 7 and 14 days and 5 m gC d l 1 for 7 days was not significantly different from controls. On the other hand, the interrenal tissue of fish exposed to 1 m gC d l 1 for 30 days secreted significantly larger amounts of cortisol in response to ACTH compared to controls. The significance of these findings to the interrenal dysfunction previously diagnosed in fish from lakes contaminated by heavy metals is discussed.

The DERAA HLA-DR alleles in patients with early polyarthritis: protection against severe disease and lack of association with rheumatoid arthritis autoantibodies.

OBJECTIVE To define the association of alleles encoding the HLA-DR rheumatoid arthritis (RA) protective epitope (DERAA) with the presence of RA-associated antibodies at study inclusion and with severe outcome in patients with early polyarthritis (EPA). METHODS Consecutive EPA patients (n = 210) were evaluated early (mean of 4.8 months after diagnosis) and prospectively (for 30 months). HLA class II typing was performed by polymerase chain reaction using sequence-specific primers, and HLA-DR alleles DERAA, RA-associated shared epitope (SE), and non-SE/non-DERAA (neither SE nor DERAA) were identified. RA-associated antibodies identified were anti-Sa/citrullinated vimentin, anti-cyclic citrullinated peptide 2, and IgM rheumatoid factor. Severe disease was defined according to a preset threshold of joint destruction and/or functional limitation. RESULTS DERAA and SE alleles were present in 62 and 110 of the 210 EPA patients, respectively. At 30 months, severe disease was present in 78 patients (37%). In contrast to SE alleles, DERAA alleles were not associated with the production of RA-associated antibodies, but were strongly protective against severe disease at 30 months (odds ratio 0.30, P < 0.001). DERAA alleles emerged as a strong, independent protective marker on multivariate analysis. The protective effect of DERAA was seen only in patients who did not already have erosions at study inclusion, was independent of the presence of antibodies, but was not associated with spontaneous remission. CONCLUSION In our EPA cohort, the presence of a DERAA sequence was a strong independent predictor of a better prognosis, but only in the absence of erosive disease that was already present at inclusion. Identification of DERAA alleles may help in managing the large subgroup of EPA patients who do not have erosions at baseline.