Immunoneuroendocrine alterations in patients with progressive forms of chronic Chagas disease.

We studied the features of parallel immunoneuroendocrine responses in patients with different degrees of chronic Chagas myocarditis (indeterminate, mild/moderate or severe). A systemic inflammatory scenario was evident in patients with severe myocarditis compared to healthy subjects. This was paralleled by a disrupted activation of the hypothalamus-pituitary-adrenal axis, characterized by decreased concentrations of dehydroepiandrosterone-sulfate (DHEA-s) and an unbalanced cortisol/DHEA-s ratio, reinforcing the view that severe Chagas disease is devoid of an adequate anti-inflammatory milieu, likely involved in pathology. Our study constitutes the first demonstration of neuroendocrine disturbances, in parallel to a systemic inflammatory profile, during progressive human Chagas disease.

The mitotic clock in skeletal muscle regeneration, disease and cell mediated gene therapy.

The regenerative capacity of skeletal muscle will depend on the number of available satellite cells and their proliferative capacity. We have measured both parameters in ageing, and have shown that although the proliferative capacity of satellite cells is decreasing during muscle growth, it then stabilizes in the adult, whereas the number of satellite cells decreases during ageing. We have also developed a model to evaluate the regenerative capacity of human satellite cells by implantation into regenerating muscles of immunodeficient mice. Using telomere measurements, we have shown that the proliferative capacity of satellite cells is dramatically decreased in muscle dystrophies, thus hampering the possibilities of autologous cell therapy. Immortalization by telomerase was unsuccessful, and we currently investigate the factors involved in cell cycle exits in human myoblasts. We have also observed that insulin-like growth factor-1 (IGF-1), a factor known to provoke hypertrophy, does not increase the proliferative potential of satellite cells, which suggests that hypertrophy is provoked by increasing the number of satellite cells engaged in differentiation, thus possibly decreasing the compartment of reserve cells. We conclude that autologous cell therapy can be applied to specific targets when there is a source of satellite cells which is not yet exhausted. This is the case of Oculo-Pharyngeal Muscular Dystrophy (OPMD), a late onset muscular dystrophy, and we participate to a clinical trial using autologous satellite cells isolated from muscles spared by the disease.

The involvement of laminin in anti-myocardial cell autoimmune response in murine Chagas disease.

The pathogenesis of chronic chagasic cardiomyopathy associated with Chagas disease is still controversial, although evidence indicates a T cell-dependent autoimmune process. Using a mouse model for chronic Chagas disease, we previously evidenced that hearts grafted within the ears of Trypanosoma cruzi infected syngeneic recipients were rejected through a CD4+ T cell-dependent mechanism. Moreover, we showed that such a process was dependent on laminin-mediated interactions, since it could be abrogated by anti-laminin or anti-laminin receptor antibodies. In this review the same passive cell transfer model is considered for discussion: the participation of the laminin alteration in the composition of the inflammatory infiltrate formed in response to the antimyocardial autoreactive CD4+ T cells, as well as the presence of laminin-binding cytokines. Finally we suggest the existence of a relationship between the inflammatory infiltrate, the laminin contents and deposition of pro-inflammatory laminin-binding cytokines, which may act in concert during the generation of Chagas disease-related cardiomyopathy.

Involvement of laminin and its receptor in abrogation of heart graft rejection by autoreactive T cells from Trypanosoma cruzi-infected mice.

Extracellular matrix ligands and receptors have been identified as determining in vivo lymphocyte positioning and activation, including effector functions in alloreactive responses. Herein we evaluated the involvement of laminin and its receptor, the very late antigen 6 (VLA-6) integrin, in CD4+ T cell-dependent autoreactivity, using a transplantation model for the autoimmune myocarditis occurring in mice chronically infected with Trypanosoma cruzi. Previous work showed that syngeneic mouse hearts grafted in the ears of chronic chagasic recipients were rejected through a CD4+ T cell-dependent mechanism. Rejection also occurred when cells from chagasic animals were transferred adjacent to hearts transplanted into naive recipients. Here, we observed the formation of a thick laminin network during rejection, with donor-derived CD4+ T cells concentrated in the laminin-rich areas. Most importantly, anti-laminin as well as anti-laminin receptor Ab inhibited the rejection of syngeneic hearts by T cells from chagasic animals. Our results suggest that interaction of the VLA-6 molecule with laminin is involved in triggering the antimyocardial autoreactive process by driving the influx of CD4+ T cells to the heart. They also support the concept that an Ag-specific T cell response, even an autoreactive one, can be modulated by in vivo interactions involving extracellular matrix ligands and receptors. In this regard, our study represents, to our knowledge, the first in vivo evidence for laminin-mediated T cell echotaxis, with simultaneous experimental demonstration of ligand and receptor involvement. Lastly, our findings indicate that treatment with anti-VLA-6 Abs can be effective in suppressing autoimmune disease activity.

Laminin/VLA-6 interactions and T cell function.

A growing number of investigators consider extracellular matrix (ECM) proteins to be determinant factors in lymphocyte positioning and activation. One major ECM component is laminin, which is constitutively expressed in the thymus as well as in thymus-dependent areas of peripheral lymphoid organs. In the thymus, laminin is produced by epithelial and dendritic cells, and appears to mediate interactions with thymocytes through specific laminin receptors, in particular the integrin VLA-6. This receptor is also expressed by peripheral T cells, and is apparently involved in effector T cell migration and activation. We showed that CD4+ T lymphocytes from chronic chagasic mice exhibited an increase in the absolute and relative number of cells with high VLA-6 expression. Additionally, it is likely that VLA-6/laminin interactions are required for the development of the CD4+T cell-dependent anti-myocardial autoreactive process that occurs in these animals. Lastly, laminin can bind to some cytokines, a fact that may represent an additional mechanism by which this extracellular matrix component modulates the behavior of T lymphocytes. Taken together, the present data strongly indicate that interactions involving laminin and VLA-6 are functionally linked to relevant events in T cell physiology, comprising entrance of pro-thymocytes into the thymus, intrathymic T cell migration and differentiation, as well as the functioning of mature T lymphocytes, including effector cells.

Laminin/VLA-6 interactions and T cell function

A growing number of investigators consider extracellular matrix (ECM) proteins to be determinant factors in lymphocyte positioning and activation. One major ECM component is laminin, which is constitutively expressed in the thymus as well as in thymus-dependent areas of peripheral lymphoid organs. In the thymus, laminin is produced by epithelial and dendritic cells, and appears to mediate interactions with thymocytes through specific laminin receptors, in particular the integrin VLA-6. This receptor is also expressed by peripheral T cells, and is apparently involved in effector T cell migration and activation. We showed that CD4+ T lymphocytes from chronic chagasic mice exhibited an increase in the absolute and relative number of cells with high VLA-6 expression. Additionally, it is likely that VLA-6/laminin interactions are required for the development of the CD4+ T cell-dependent anti-myocardial autoreactive process that occurs in these animals. Lastly, laminin can bind to some cytokines, a fact that may represent an additional mechanism by which this extracellular matrix component modulates the behavior of T lymphocytes. Taken together, the present data strongly indicate that interactions involving laminin and VLA-6 are functionally linked to relevant events in T cell physiology, comprising entrance of pro-thymocytes into the thymus, intrathymic T cell migration and differentiation, as well as the functioning of mature T lymphocytes, including effector cells.

Is the thymus a target organ in infectious diseases?

The thymus is a central lymphoid organ, in which T cell precursors differentiate and generate most of the so-called T cell repertoire. Along with a variety of acute infectious diseases, we and others determined important changes in both microenvironmental and lymphoid compartments of the organ. For example, one major and common feature observed in acute viral, bacterial and parasitic diseases, is a depletion of cortical thymocytes, mostly those bearing the CD4-CD8 double positive phenotype. This occurs simultaneously to the relative enrichment in medullary CD4 or CD8 single positive cells, expressing high densities of the CD3 complex. Additionally we noticed a variety of changes in the thymic microenvironment (and particularly its epithelial component), comprising abnormal location of thymic epithelial cell subsets as well has a denser Ia-bearing cellular network. Moreover, the extracellular matrix network was altered with an intralobular increase of basement membrane proteins that positively correlated with the degree of thymocyte death. Lastly, anti-thymic cell antibodies were detected in both human and animal models of infectious diseases, and in some of them a phenomenon of molecular mimicry could be evidenced. Taken together, the data reviewed herein clearly show that the thymus should be regarded as a target in infectious diseases.