Induction of virus-induced IDDM in virus resistant mice without lymphocyte maturation

Coxsackievirus B3 infection compromises endothelial-dependent vasodilation of coronary resistance arteries

The mechanisms of coronary artery dysfunction in coxsackievirus B3 (CVB3)-mediated viral myocarditis are poorly understood. We used pressure myography of mouse septal coronary arteries to determine the early and late effects of CVB3 infection on vascular function. Male CD-1 mice (age 6-7 weeks) were infected with CVB3 (1.75 x 10(10) pfu, i.p.). Control mice were injected with PBS. Mice were killed at 3, 7, and 42 days post infection, and the ventricular septal artery was dissected and mounted on a pressure myograph. Pressure-induced myogenic tone was similar in CVB3-infected and sham-infected mice at 3 and 7 days post infection. However, at 42 days post infection constriction of septal arteries to pressures equal to or less than 60 mm Hg was enhanced in CVB3-infected mice compared with sham controls. Agonist-induced vasodilation, as assessed by response to acetylcholine (1 nM-3 microM), was unaltered at early time points (days 3 and 7) in CVB3-infected mice. At later time points (day 42), there was a significant decrease in ACh-induced vasodilation in CVB3-infected mice. Bosentan, an ET-1 (ETA and ETB) receptor antagonist, did not completely ameliorate the reduced ACh-induced vasodilation in 42-day infected mice, indicating that ET-1 does not contribute to vascular dysfunction. Smooth muscle function, as measured by constriction to KCl or dilation to sodium nitroprusside, was unchanged in infected mice at early and late time points. Immunohistochemistry and ET-1 immunoassay were then performed to assess ET-1 levels in CVB3- and sham-infected hearts. There were no differences in ET-1 protein localization or levels at 42 days post infection in sham- and CVB3-infected animals. Finally, in situ hybridization and TUNEL staining were performed to assess viral localization and cell death in CVB3-infected hearts. There was no detectable CVB3 or TUNEL positivity in the endothelium of coronary arteries. Therefore, late impairment of endothelial-dependent vasorelaxation of coronary resistance vessels in CVB3-induced myocarditis does not appear to involve altered ET-1 expression but may be secondary to decreased stimulated NO secretion by the endothelium.

Innate immune response to encephalomyocarditis virus infection mediated by CD1d

CD1d-reactive natural killer T (NKT) cells can rapidly produce T helper type 1 (Th1) and/or Th2 cytokines, can activate antigen-presenting cell (APC) interleukin-12 (IL-12) production, and are implicated in the regulation of adaptive immune responses. The role of the CD1d system was assessed during infection with encephalomyocarditis virus (EMCV-D), a picornavirus that causes acute diabetes, paralysis and myocarditis. EMCV-D resistance depends on IL-12-mediated interferon-gamma (IFN-gamma) production. CD1d-deficient mice, which also lack CD1d-reactive NKT cells, were substantially more sensitive to infection with EMCV-D. Infected CD1d knockout mice had decreased IL-12 levels in vitro and in vivo, and indeed were protected by treatment with exogenous IL-12. IFN-gamma production in CD1d knockout mice was decreased compared with that in wild-type (WT) mice in response to EMCV-D in vitro, although differences were not detected in vivo. Treatment with anti-asialo-GM1 antibody, to deplete NK cells, caused a marked increase in susceptibility of WT mice to EMCV-D infection, whereas CD1d knockout mice were little affected, suggesting that NK-cell-mediated protection is CD1d-dependent. Therefore, these data indicate that CD1d is essential for optimal responses to acute picornaviral infection. We propose that CD1d-reactive T cells respond to early immune signals and function in the innate immune response to a physiological viral infection by rapidly augmenting APC IL-12 production and activating NK cells.

Granzyme B in atherosclerosis and transplant vascular disease: association with cell death and atherosclerotic disease severity

Apoptosis of intimal cells is an important contributor to the pathogenesis of atherosclerosis and transplant vascular disease (TVD). Since the activated immune response may be a key regulator of apoptosis in these lesions, we used immunohistochemistry to characterize the presence and localization of granzyme B, a major mediator of the cytotoxic immune response, in advanced atherosclerosis and TVD. Formalin-fixed, paraffin-embedded transverse sections from human left anterior descending coronary arteries were cut serially and stained with antibodies specific for granzyme B, smooth muscle alpha-actin, CD68, and CD3. The amount of granzyme B staining was semi-quantitated on a 0-5+/5+ scale. Also, TUNEL staining and in situ hybridization was performed to visualize cells undergoing cellular damage suggestive of apoptosis, and to localize granzyme B mRNA, respectively. Granzyme B localization was similar in both diseases. This protease was absent in arteries with mild atherosclerosis, but was abundant in the intima and media of vessels with advanced atherosclerosis and TVD. Within the intima, granzyme B localized to TUNEL-positive foam cells surrounding lipid-rich atheromas. Staining of serial sections with granzyme B and either smooth muscle alpha-actin, anti-CD68, or anti-CD3 showed that granzyme B localized to smooth muscle cells, macrophages, and T-cells. Further, in situ hybridization for granzyme B mRNA in TVD cases localized its expression to infiltrating leukocytes and not foam cells. In conclusion, the presence of granzyme B in advanced atherosclerotic lesions and TVD is associated with increasing disease severity and cell death. These observations suggest that granzyme B-mediated apoptosis may contribute to the pathogenesis of these diseases.