1991 Mack Forster Award Lecture. HLA and disease: from epidemiology to immunotherapy

Le kétoconazole antagonise les effets immuno-gonadotropes au test de la nage forcée chez le rat mâle Wistar

On a souvent rapporté que la dépression s’installe suite à des perturbations des activités de l’axe corticotrope et du système immunitaire. L’objectif de cette étude était d’explorer les effets du kétoconazole, un dérivé d’imidazole, inhibiteur de la stéroïdogénèse gonadique et surrénalienne, sur les variations du nombre de leucocytes totaux et des pourcentages de sous-populations leucocytaires, au cours de la nage forcée chez le rat (test de Porsolt), un test consiste à tester l’efficacité des antidépresseurs. Des cathéters ont été implantés, sous anesthésie générale, dans la carotide droite, et des prises de sang (0,2 mL) ont été réalisées à des intervalles de 15 min au cours de l’expérimentation, alors que les animaux pouvaient se comporter librement. Les degrés d’anxiété et d’activité locomotrice des rats ont été mesurés au labyrinthe en croix surélevée et au test des champs ouverts. La nage forcée a provoqué des fluctuations du système immunitaire et de la testostéronémie, lesquelles qui ont été inhibées suite au traitement des animaux au kétoconazole. Cet effet a été obtenu également sur le plan comportemental (labyrinthe en croix surélevée, nage forcée) dans le sens d’une amélioration (effets anxiolytique et antidépresseur). Ces résultats suggèrent que les réponses comportementales et physiologiques sont inter-reliées d’une manière multifactorielle et que la corticostérone joue un rôle clé dans la pathogénie des maladies psychiatriques.

Association of a missense mutation of the laminin alpha2 gene with tuberculoid type of leprosy in Indonesian patients

Leprosy, an infection caused by Mycobacterium leprae, has a specific tropism for the myelinating Schwann cells of peripheral nerves. Recently, the G domain of laminin alpha2 has been shown to be a mediator for M. leprae to bind to alpha-dystroglycan in Schwann cells. In order to analyse the association of leprosy with the mediator, three genetic polymorphisms encoding the G domain of the laminin alpha2 chain were analysed by direct sequencing in 53 leprosy patients and 58 healthy contact individuals from Indonesia. There was no significant difference in the incidence of the polymorphisms between patients and non-patients. Remarkably, it was found that a missense mutation (T7809C) substituting valine with alanine (V2587A) was found to be more frequent in the tuberculoid type than in the lepromatous type leprosy. It is supposed that this missense mutation is one of the determinant factors in the early onset of peripheral nerve damage in Indonesian tuberculoid leprosy patients.

Decreased frequency of HLA-DRB1 13 alleles in Frenchwomen with HPV-positive carcinoma of the cervix

Specific types of human papillomaviruses (HPV) are associated with most cases of pre-invasive and invasive neoplasia of the uterine cervix. HLA phenotype influences susceptibility and resistance to viral infections and may therefore influence the course of HPV-associated tumors. Some data suggest that specific HLA class-II alleles may be associated with protection from or susceptibility to papillomavirus-associated lesions, but these results are still controversial. Using molecular probes, we looked for associations between specific DQA1, DQB1, DRB1 HLA class-II alleles, HPV types and cervical cancer. The analysis was performed on a population of 126 patients with invasive cervical cancer. For HLA typing, 165 healthy individuals were taken as controls. The DRB1 1301/02 allele frequency significantly decreased in patients (11%) as compared to controls (29%). This difference in frequency was dependent on the HPV-positive status of tumors and was no longer significant in the group of HPV-negative lesions. The same trends were observed with the DRB1 1301/02-DQA1 0103-DQB1 0603 haplotype frequency. An increase in the frequency of the DRB1 1401/07 and DRB1 03 alleles was observed in patients under 40. Contrary to what has been reported in the literature, no increase in the DRB1 15 allele frequency was observed in our series and only a slight increase in the DQB1 03 frequency was found in patients (70%) compared to controls (58%). In our study, no positive correlations between cervical cancer in Frenchwomen and specific HLA DR-DQ haplotypes has been found. In contrast, a negative correlation between DRB1 1301/ 02 alleles and HPV-positive tumors has been observed. This may suggest a protective effect of DR13 against HPV-associated lesions of the cervix.

Arginine at positions 13 or 70-71 in pocket 4 of HLA-DRB1 alleles is associated with susceptibility to tuberculoid leprosy

Evaluation of human histocompatibility leukocyte antigen (HLA) class II genes in 54 cases of tuberculoid leprosy (TL) and 44 controls has shown a positive association with HLA-DRB1 alleles that contain Arg13 or Arg70-Arg71. Among TL patients, 87% carry specific alleles of DRB1 Arg13 or Arg70-Arg71 as compared to 43% among controls (p = 5 x 10(-6)) conferring a relative risk of 8.8. Thus, susceptibility to TL involves three critical amino acid positions of the beta chain, the side chains of which, when modeled on the DR1 crystal structure, line a pocket (pocket 4) accommodating the side chain of a bound peptide. This study suggests that disease susceptibility may be determined by the independent contribution of polymorphic residues participating in the formation of a functional arrangement (i.e., pocket) within the binding cleft of an HLA molecule.

GAD65 is recognized by T-cells, but not by antibodies from NOD-mice

Since the 64kDa-protein glutamic acid decarboxylase (GAD) is one of the major autoantigens in T-cell mediated Type 1 diabetes, its relevance as a T-cell antigen needs to be clarified. After isolation of splenic T-cells from non-obese diabetic (NOD) mice, a useful model for human Type 1 diabetes, we found that these T-cells proliferate spontaneously when incubated with human GAD65, but only marginally after incubation with GAD67, both recombinated in the baculovirus system. No effect was observed with non-diabetic NOD mice or with T-cells from H-2 identical NON-NOD-H-2g7 control mice. It has been published previously that NOD mice develop autoantibodies against a 64kDa protein detected with mouse beta cells. In immunoprecipitation experiments with sera from the same NOD mice and 35S-methionine-labelled GAD, no autoantibody binding could be detected. We conclude firstly that GAD65 is an important T-cell antigen which is relevant early in the development of Type 1 diabetes and secondly that there is an antigenic epitope in the human GAD65 molecule recognized by NOD T-cells, but not by NOD autoantibodies precipitating conformational epitopes. Our results therefore provide further evidence that GAD65 is a T-cell antigen in NOD mice, being possibly also involved in very early processes leading to the development of human Type 1 diabetes.