In patients with relapsing-remitting multiple sclerosis, both BG-12 regimens, as compared with placebo, significantly reduced the proportion of patients who had a relapse, the annualized relapse rate, the rate of disability progression, and the number of lesions on MRI. (Funded by Biogen Idec; DEFINE ClinicalTrials.gov number, NCT00420212.).

G207 is a conditionally replicating derivative of herpes simplex virus (HSV) type-1 strain F engineered with deletions of both ␥ 1 34.5 loci and a lacZ insertion disabling the U L 39 gene. We have demonstrated the efficacy of G207 in treating malignant glial tumors in athymic mice, as well as the safety of intracerebral G207 inoculation in mice and in Aotus nancymai. We sought to determine the safety of G207 inoculation into cerebral malignant glial tumors in humans. Criteria for inclusion into this dose-escalation study were the diagnosis of histologically proven malignant glioma, Karnofsky score у70, recurrence despite surgery and radiation therapy, and an enhancing lesion greater than 1 cm in diameter.

Studies of the pathogenesis and molecular biology of JC virus infection over the last two decades have significantly changed our understanding of progressive multifocal leukoencephalopathy, which can be described as a subacute viral infection of neuroglial cells that probably follows reactivation of latent infection rather than being the consequence of prolonged JC virus replication in the brain. There is now sufficient evidence to suggest that JC virus latency occurs in kidney and B cells. However, JC virus isolates from brain or kidney differ in the regulatory regions of their viral genomes which are controlled by host cell factors for viral gene expression and replication. DNA sequences of noncoding regions of the viral genome display a certain heterogeneity among isolates from brain and kidney. These data suggest that an archetypal strain of JC virus exists whose sequence is altered during replication in different cell types. The JC virus regulatory region likely plays a significant role in establishing viral latency and must be acted upon for reactivation of the virus. A developing hypothesis is that reactivation takes place from latently infected B lymphocytes that are activated as a result of immune suppression. JC virus enters the brain in the activated B cell. Evidence for this mechanism is the detection of JC virus DNA in peripheral blood lymphocytes and infected B cells in the brains of patients with progressive multifocal leukoencephalopathy. Once virus enters the brain, astrocytes as well as oligodendrocytes support JC virus multiplication. Therefore, JC virus infection of neuroglial cells may impair other neuroglial functions besides the production and maintenance of myelin. Consequently our increased understanding of the pathogenesis of progressive multifocal leukoencephalopathy suggests new ways to intervene in JC virus infection with immunomodulation therapies. Perhaps along with trials of nucleoside analogs or interferon administration, this fatal disease, for which no consensus of antiviral therapy exists, may yield to innovative treatment protocols.

Early reports of pediatric HIV-1-associated neuropathology described the presence of viral particles in some astrocytes, implicating direct infection of the immature nervous system as a contributing factor to the observed neuropathology. Several recent reports suggest that in those astrocytes infected with HIV-1, the level of antigenic expression of the proviral genome is below the sensitivity limits of conventional histochemical techniques. Identification of these astrocytes would instead require the use of a highly sensitive radiolabeled DNA or RNA probe for in situ hybridization to detect the persistent viral nucleic acids. To test this hypothesis, we examined autopsy tissue from 12 infants and children with AIDS-associated encephalopathy for the presence of HIV-1-infected astrocytes using combined isotopic in situ hybridization for the detection of viral-specific nucleic acids and immunohistochemistry for the identification of astrocytes. We detected HIV-1 nucleic acids in astrocytes in subcortical white matter from four pediatric patients with moderate to extensive leukoencephalitis. While gp41 was detectable only on macrophages and multinucleated giant cells, HIV-1 Nef protein was present in cells morphologically identified as astrocytes in two of these patients, further suggesting that HIV-1 establishes a persistent rather than a productive infection in astrocytes. Subcortical astrocytes may therefore be an unrecognized reservoir for HIV-1 in the developing nervous system of some children with AIDS-associated leukoencephalitis.