Fabry disease is a lysosomal storage disorder caused by a deficiency of the lysosomal enzyme ␣-galactosidase A (␣-gal A). This enzymatic defect results in the accumulation of the glycosphingolipid globotriaosylceramide (Gb 3; also referred to as ceramidetrihexoside) throughout the body. To investigate the effects of purified ␣-gal A, 10 patients with Fabry disease received a single i.v. infusion of one of five escalating dose levels of the enzyme. The objectives of this study were: (i) to evaluate the safety of administered ␣-gal A, (ii) to assess the pharmacokinetics of i.v.-administered ␣-gal A in plasma and liver, and (iii) to determine the effect of this replacement enzyme on hepatic, urine sediment and plasma concentrations of Gb3. ␣-Gal A infusions were well tolerated in all patients. Immunohistochemical staining of liver tissue approximately 2 days after enzyme infusion identified ␣-gal A in several cell types, including sinusoidal endothelial cells, Kupffer cells, and hepatocytes, suggesting diffuse uptake via the mannose 6-phosphate receptor. The tissue half-life in the liver was greater than 24 hr. After the single dose of ␣-gal A, nine of the 10 patients had significantly reduced Gb3 levels both in the liver and shed renal tubular epithelial cells in the urine sediment. These data demonstrate that single infusions of ␣-gal A prepared from transfected human fibroblasts are both safe and biochemically active in patients with Fabry disease. The degree of substrate reduction seen in the study is potentially clinically significant in view of the fact that Gb 3 burden in Fabry patients increases gradually over decades. Taken together, these results suggest that enzyme replacement is likely to be an effective therapy for patients with this metabolic disorder.

We have identified a single rat monoclonal antibody, G7, that is a potent inducer of interleukin (IL-2) production from all functioning T cell hybridomas as well as from normal T cells. G7 is also mitogenic for normal T cells and is a very effective inducer of IL-2 receptor expression. On fluorescence-activated cell sorter analysis, G7 recognized a pan-T cell antigen. Immunoprecipitation studies demonstrated that G7 recognized a cell surface molecule of 28-32 kD that appeared to be identical to Thy-1 in coprecipitation studies. In addition, G7 precipitated a protein of 50 kD. The possible relationship of the putative molecular complex identified by G7 on murine cells to the molecular complex identified on human T cells with anti-T3 reagents is discussed. In addition, G7 should prove to be a very useful reagent for studying the early events of lymphocyte activation as well as an inducer of lymphokine-rich supernatants.

Thy-1, a glycoprotein of relative molecular mass 25,000 (25K), is a major constituent of the cell surface of mouse thymocytes, peripheral T cells and neurones. In man, Thy-1 is present on neurones and on a small percentage of thymocytes, but is absent from peripheral T cells. The amino-acid and complementary DNA sequences of Thy-1 indicate that it has a structure similar to an isolated V (variable region) domain of immunoglobulin. Although the function of Thy-1 is unknown, the ability of different anti-Thy-1 monoclonal antibodies to activate murine T cells or induce functional changes in neuronal cells in vitro suggests that Thy-1 is involved in transmembrane signalling. We now show that crosslinking of murine Thy-1 triggers a rapid rise in the cytoplasmic free calcium concentration ([Ca2+]i), not only in murine T cells and Thy-1.2-transfected human T cells, but also in murine B-lymphoma cells transfected with the murine thy-1.2 gene. These results indicate that the generation and transduction of the signal leading to the rise in [Ca2+]i is independent of the T-cell receptor and other T-cell-specific molecules. The preservation of the [Ca2+]i-modulating function of Thy-1 in various lymphoid cells of two species further suggests that the necessary signal either originates in the Thy-1 molecule itself or is generated in concert with a highly conserved molecules(s) associated with Thy-1.

Symptomatic cytomegalovirus (CMV) disease has been the standard endpoint for clinical trials in organ transplant recipients. Viral load may be a more relevant endpoint due to low frequency of disease. We performed a meta-analysis and systematic review of the literature. We found several lines of evidence to support the validity of viral load as an appropriate surrogate end-point, including the following: (1) viral loads in CMV disease are significantly greater than in asymptomatic viremia (odds ratio, 9.3 95% confidence interval, 4.6-19.3); (2) kinetics of viral replication are strongly associated with progression to disease; (3) pooled incidence of CMV viremia and disease is significantly lower during prophylaxis compared with the full patient follow-up period (viremia incidence: 3.2% vs 34.3%; P < .001) (disease incidence: 1.1% vs 13.0%; P < .001); (4) treatment of viremia prevented disease; and (5) viral load decline correlated with symptom resolution. Based on the analysis, we conclude that CMV load is an appropriate surrogate endpoint for CMV trials in organ transplant recipients.