Gene therapy hits a snag
Using gene therapy to combat cancer depends on delivering the genes to the tumour on a "vector" - usually an adenovirus thought to be harmless to the host. But long-term follow-up of survivors of gene therapy for brain glioblastoma shows that the therapy causes chronic brain inflammation (Nat Med 1999;5:1256-63). Three months after glioma growth was inhibited through gene therapy, researchers found activated macrophages/microglia and astrocytes, positive T cells, secondary demyelination, widespread immunoreactivity to a herpes simplex virus 1 enzyme, and the genome of the adenovirus vector throughout large areas of the brain. This could pose an important stumbling block for the future use of gene therapy.
Persistence of memory
Our understanding of the immune response to infection, and of immunization, may be revolutionized by recent research into T cells. The immune response after vaccination results from the property of "memory," which is established in appropriate lymphocytes. It was thought that these "memory T cells" are activated when they "see" the offending antigen, together with a major histocompatibility protein, and that there was a continuing requirement for antigen stimulation for memory T cells to work. Now 2 studies in mice show that memory T cells - both CD4 and CD8 cells - never forget (Science 1999;286:1377-81,1381-3). Even in mice genetically altered to lack major histocompatibility complex proteins and never exposed to the antigen before, memory T cells launched an immune response to invading pathogens.