Th1 genetic adjuvants modulate immune responses in neonates

In these studies, we address the ability of DNA encoding Th1 cytokines to b ias the isotype of antibody raised by neonatal or adult immunization with a n influenza hemagglutinin expressing DNA (HA-DNA). Neonatal mice coimmunize d with HA-DNA and either IL-12 or IFN-gamma -expressing DNA developed IgG2a -biased immune responses, regardless of inoculation method. In contrast, th e Th1 genetic adjuvants had no effect on IgG subtype patterns in adults. In neonatal mice, the Th1 genetic adjuvants also shifted the pattern of lymph okine production by recall splenocytes from a mixed response of IFN-gamma a nd IL-5 to exclusively IFN-gamma. In adults, despite the failure to change the isotype pattern of the antibody response, a shift towards IFN-gamma pro duction also occurred for recall splenocytes following coimmunzation with I L-12. Thus, coinoculation of Th1 genetic adjuvants had greater effects on t he nature of the immune response in the neonate than in adults. (C) 2001 Pu blished by Elsevier Science Ltd.