Journals of Gerontology Series A: Biological Sciences and Medical Sciences, Vol 53, Issue 4 B281-B286, Copyright © 1998 by The Gerontological Society of America

JOURNAL ARTICLE

Immunogenicity and efficacy of a DNA vaccine in aged mice

DM Klinman, J Conover, ET Bloom and W Weiss
Section of Retroviral Immunology, Division of Viral Products, Division of Cellular and Gene Therapies, Center for Biologics Research and Evaluation, Food and Drug ADministration, Bethesda.

The immunogenicity and protective efficacy of a DNA vaccine encoding the circumsporozoite protein of the Plasmodium yoelii malaria parasite was evaluated in young (2 months) versus aged (>26 months) BALB/c mice. The primary and secondary humoral immune response to aged mice was 19- and 7-fold lower, respectively, than that of similarly treated young animals (p<.01). Cytoxic T lymphocyte activity in aged mice was also lower than in younger animals. The vaccine response of aged animals was characterized by a 6-fold increase in interleukin-4 and a 3-fold increase in interferon-y (IFN-y) secreting cells, whereas in young animals immunization only stimulated the production of the type 1 cytokine IFN-y. Overall, 80% of young vaccinated mice were protected from subsequent challenge with live malaria sporozoites whereas only 40% of aged mice were protected. These results are the first to demonstrate that DNA vaccination induces less effective immunity in aged than young animals.