FIG. 3.

HC-Ads and Ads mediate high levels of short-term HSV-1 TK expression in preimmunized non-tumor-bearing animals with minimal inflammation at 1 week after vector delivery. Animals were preimmunized with a systemic injection of adenovirus or with saline alone (nonimmunized) and 2 weeks later were injected intracranially with Ad-TK or HC-Ad-TK. Animals were euthanized 1 week after vector delivery, and brains from five animals per group were analyzed by immunocytochemistry (a to d). Representative images are shown. Low-magnification (left panels) and high-magnification (right panels) images of HSV1-TK immunoreactivity demonstrate high levels of HSV1-TK expression in animals treated with HC-Ad-TK or Ad-TK, regardless of their immunization status. Immunocytochemistry reveals minimal CD8⁺ lymphocytes (e to h) and macrophages/microglia (i to l) in the brains of all animals. Arrows indicate the injection site.