Reactive oxygen species (ROS) are conventionally classified as toxic consequences of aerobic life, and the brain is particularly susceptible to ROS-induced oxidative stress and damage owing to its high energy and oxygen demands. In this context, NAPDH oxidases (Nox) are a widespread source of brain ROS implicated in seizures, stroke, and neurodegeneration. A physiological role for ROS generation in normal brain function has not been established, despite the fact that mice and humans lacking functional Nox proteins exhibit cognitive deficits. Using molecular imaging with Peroxyfluor-6 (PF6), a new selective fluorescent indicator for hydrogen peroxide (H2O2), we show that adult hippocampal stem/progenitor cells (AHPs) generate H2O2 through Nox2 to regulate intracellular growth signaling pathways, which in turn maintains their normal proliferation in vitro and in vivo. Our results challenge the traditional view that brain ROS are solely deleterious by demonstrating that controlled ROS chemistry is needed for maintaining specific cell populations.

The long-term consequences of adenovirus-mediated conditional cytotoxic gene therapy for gliomas remain uncharacterized. We report here detection of active brain inflammation 3 months after successful inhibition of syngeneic glioma growth. The inflammatory infiltrate consisted of activated macrophages/microglia and astrocytes, and T lymphocytes positive for leucosyalin, CD3 and CD8, and included secondary demyelination. We detected strong widespread herpes simplex virus 1 thymidine kinase immunoreactivity and vector genomes throughout large areas of the brain. Thus, patient evaluation and the design of clinical trials in ongoing and future gene therapy for brain glioblastoma must address not only tumor-killing efficiency, but also long-term active brain inflammation, loss of myelin fibers and persistent transgene expression.

The results in the macaque suggest that intravitreal injection of AAV2 would produce high levels of gene expression at the human fovea, important in retinal gene therapy, but not in the central retina beyond the fovea.

CD46 is used by human group B adenoviruses (Ads) as a high-affinity attachment receptor. Here we show evidence that several group B Ads utilize an additional receptor for infection of human cells, which is different from CD46. We tentatively named this receptor receptor X. Competition studies with unlabeled and labeled Ads, recombinant Ad fiber knobs, and soluble CD46 and CD46 antibodies revealed three different subgroups of group B Ads, in terms of their receptor usage. Group I (Ad16, -21, -35, and -50) nearly exclusively uses CD46. Group II (Ad3, -7p, and -14) utilizes receptor X and not CD46. Group III (Ad11p) uses both CD46 and the alternative receptor X. Interaction of group II and III Ads with receptor X occurs via the fiber knob. Receptor X is an abundantly expressed glycoprotein that interacts with group II and III Ads at relatively low affinity in a Ca 2؉ -dependent manner. This receptor is expressed at high levels on human mesenchymal and undifferentiated embryonic stem cells, as well as on human cancer cell lines. These findings have practical implications for stem cell and gene therapy.Human adenoviruses (Ads) have been classified into six subgroups (A to F) currently containing 51 serotypes. Group B Ads form two genetic clusters, B1 (Ad3, Ad7, Ad16, Ad21, and Ad50) and B2 (Ad11, Ad14, Ad34, and Ad35) (44). Most B1 Ads are mainly associated with acute respiratory disease and, unlike the species C Ads (e.g., Ad5), do not establish persistence (43). The B2 serotypes 11p, 34, and 35 have mainly been associated with infections of the kidneys and urinary tract. Recently, gene transfer vectors based on group B Ads have shown promise for cell and gene therapy. Vectors containing fibers from group B Ads efficiently transduce human cell types that are relatively refractory to infection with classical serotype Ad5 vectors, including malignant tumor cells (30, 39), hematopoietic stem cells (26,35,46), mesenchymal stem (MES) cells (9, 18), dendritic cells (DC) (5, 27, 28), lymphocytes (33), chorion villus cells, and endothelial cells (13).CD46 has been identified as a cellular receptor for group B Ads (7, 32, 37) whereby the two distal extracellular domains of CD46 are involved in Ad binding (6, 7). In humans, CD46 is a ubiquitously expressed membrane protein with complement regulatory functions.A series of data suggest the existence of an additional group B Ad receptor(s). (i) Several groups found that Ad3 and Ad7 do not use CD46 for infection (7, 21), (ii) Ad3 and Ad7 (group B1) and Ad35 (group B2) do not compete for binding on HeLa cells (31,35), and (iii) Ad11p fiber knob can completely block binding of wild-type Ad35 to A549 cells, while recombinant Ad35 fiber knob cannot completely block Ad11p binding (22,41). While these data suggest that Ad3 and Ad7 and probably Ad11 can use a receptor that is different from CD46, the nature of this receptor(s) remains elusive. In this study, we investigated receptor usage by group B Ads on human cells and laid the groundwork for identification of the receptor. Also, the...