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