Doublecortin (Dcx) is a microtubule-associated protein expressed by migrating neuroblasts in the embryo and in the adult subventricular zone (SVZ). The adult SVZ contains neuroblasts that migrate in the rostral migratory stream (RMS) to the olfactory bulbs. We have examined the distribution and phenotype of Dcx-positive cells in the adult mouse SVZ and surrounding regions. Chains of Dcx-positive cells in the SVZ were distributed in a tight dorsal population contiguous with the RMS, with a separate ventral population comprised of discontinuous chains. Unexpectedly, Dcx-positive cells were also found outside of the SVZ: dorsally in the corpus callosum, and ventrally in the nucleus accumbens, ventromedial striatum, ventrolateral septum, and bed nucleus of the stria terminalis. Dcx-positive cells outside the SVZ had the morphology of migrating cells, occurred as individual cells or in chain-like clusters, and were more numerous anteriorly. Of the Dcx-positive cells found outside of the SVZ, 47% expressed the immature neuronal protein class III beta-tubulin, 8% expressed NeuN, a marker of mature neurons. Dcx-positive cells did not express molecules found in astrocytes, oligodendrocytes, or microglia. Structural and immunoelectron microscopy revealed that cells with the ultrastructural features of neuroblasts in the SVZ were Dcx+, and that clusters of neuroblasts emanated ventrally from the SVZ into the parenchyma. Our results suggest that the distribution of cells comprising the walls of the lateral ventricle are more heterogeneous than was thought previously, that SVZ cells may migrate dorsally and ventrally away from the SVZ, and that some emigrated cells express a neuronal phenotype.

Up to 18 million of individuals are infected by the protozoan parasite Trypanosoma cruzi in Latin America, one third of whom will develop chronic Chagas disease cardiomyopathy (CCC) up to 30 years after infection. Cardiomyocyte destruction is associated with a T cell-rich inflammatory infiltrate and fibrosis. The presence of such lesions in the relative scarcity of parasites in the heart, suggested that CCC might be due, in part, to a postinfectious autoimmune process. Over the last two decades, a significant amount of reports of autoimmune and molecular mimicry phenomena have been described in CCC. The authors will review the evidence in support of an autoimmune basis for CCC pathogenesis in humans and experimental animals, with a special emphasis on molecular mimicry as a fundamental mechanism of autoimmunity.

The specificity and function of T helper (Th) immune responses underlying the induction, progression, and resolution of experimental autoimmune myocarditis (EAM) in A/J mice are unclear. Published data suggest involvement of both Th1 and Th2 responses in EAM; however, the previous inability to assess antigen-specific in vivo and in vitro T cell responses in cardiac myosin immunized animals has confounded our understanding of this important model of autoimmune myocarditis. The goal of our study was to develop an alternative model of EAM based on a recombinant fragment of cardiac myosin, in hopes that the recombinant protein will permit measurement of functional T cell responses that is not possible with purified native protein. A/J mice immunized with a recombinant fragment of cardiac myosin spanning amino acids 1074-1646, termed Myo4, developed severe myocarditis characterized by cardiac hypertrophy, massive mononuclear cell infiltration and fibrosis, three weeks post-immunization. The mice also developed an IgG1 dominant humoral immune response specific for both Myo4 and purified cardiac myosin. The in vitro stimulation of splenocytes harvested from Myo4-immunized animals with Myo4 resulted in cellular proliferation with preferential production of the Th1-and Th17-associated cytokines, IFN-γ, IL-17 and IL-6, respectively. Production of IL-4 was negligible by comparison. This study describes a new model of EAM, inducible by immunization with a specific fragment of cardiac myosin, from which antigenspecific analyses reveal an importance for both Th1 and Th17 immunity.

Chagas disease, caused by infection with the protozoan parasite Trypanosoma cruzi, is a major public health problem in Central and South America. The pathogenesis of Chagas disease is complex and the natural course of infection is not completely understood. The recent development of bioluminescence imaging technology has facilitated studies of a number of infectious and noninfectious diseases. We developed luminescent T. cruzi to facilitate similar studies of Chagas disease pathogenesis. Luminescent T. cruzi trypomastigotes and amastigotes were imaged in infections of rat myoblast cultures, which demonstrated a clear correlation of photon emission signal strength to the number of parasites used. This was also observed in mice infected with different numbers of luminescent parasites, where a stringent correlation of photon emission to parasite number was observed early at the site of inoculation, followed by dissemination of parasites to different sites over the course of a 25 day infection. Whole animal imaging from ventral, dorsal and lateral perspectives provided clear evidence of parasite dissemination. The tissue distribution of T. cruzi was further determined by imaging heart, spleen, skeletal muscle, lungs, kidneys, liver and intestines ex vivo. These results illustrate the natural dissemination of T. cruzi during infection and unveil a new tool for studying a number of aspects of Chagas disease, including rapid in vitro screening of potential therapeutic agents, roles of parasite and host factors in the outcome of infection, and analysis of differential tissue tropism in various parasite-host strain combinations.

Chagas' heart disease (CHD), caused by the parasite Trypanosoma cruzi, is the most common form of myocarditis in Central America and South America. Some humans and experimental animals develop both humoral and cell-mediated cardiac-specific autoimmunity during infection. Benznidazole, a trypanocidal drug, is effective at reducing parasite load and decreasing the severity of myocarditis in acutely infected patients. We hypothesized that the magnitude of autoimmunity that develops following T. cruzi infection is directly proportional to the amount of damage caused by the parasite. To test this hypothesis, we used benznidazole to reduce the number of parasites in an experimental model of CHD and determined whether this treatment altered the autoimmune response. Infection of A/J mice with the Brazil strain of T. cruzi leads to the development of severe inflammation, fibrosis, necrosis, and parasitosis in the heart accompanied by vigorous cardiac myosin-specific delayed-type hypersensitivity (DTH) and antibody production at 21 days postinfection. Mice succumbed to infection within a month if left untreated. Treatment of infected mice with benznidazole eliminated mortality and decreased disease severity. Treatment also reduced cardiac myosin-specific DTH and antibody production. Reinfection of treated mice with a heartderived, virulent strain of T. cruzi or immunization with myosin led to the redevelopment of myosinspecific autoimmune responses and inflammation. These results provide a direct link between the levels of T. cruzi and the presence of autoimmunity and suggest that elimination of the parasite may result in the reduction or elimination of autoimmunity in the chronic phase of infection.