Injection of DNA encoding granulocyte-macrophage colony-stimulating factorrecruits dendritic cells for immune adjuvant effects

An important issue for effective vaccines is the development of potent adju vants that can facilitate induction or augmentation of immunity. Granulocyt e-macrophage colony-stimulating factor (GM-CSF) is a growth factor for myel oid progenitors of monocytes and dendritic cells (DC), which upon maturatio n are antigen-presenting cells (APC). The adjuvant effects of inoculation o f DNA encoding GMCSF into skin were studied. Initial experiments examined w hether the GM-CSF gene injected into the skin of mice could affect the dens ity of epidermal DC (Langerhans cells). DNA encoding GM-CSF delivered by pa rticle bombardment into skin resulted in a significant increase of epiderma l DC at the inoculation site. kinetic analysis of epidermal recruitment aft er GM-CSF inoculation showed an increase in DC that peaked at seven days. T his increase was accompanied by recruitment of DC into draining lymph nodes . The adjuvant effects of DNA encoding GM-CSF inoculated into skin were mea sured by the ability to augment antibody and T-cell responses against poorl y immunogenic tumor antigens. Peptide immunization at skin sites containing epidermal DC newly recruited by GM-CSF DNA elicited T-cell responses again st mutant p53, whereas peptide immunization of control skin sites did not e licit any detectable T-cell responses. Likewise, generation of antibodies f ollowing immunization with DNA encoding human gp75(TRP1), a tyrosinase fami ly member expressed by melanomas, was accelerated and protection from tumor challenge augmented by GM-CSF DNA.