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Infection and Immunity, January 2000, p. 38-45, Vol. 68, No. 1
Department of
Toxoplasmosis,1 Department of
Mycobacterial Immunology,2 and
Department of Cell Biology,3 Pasteur
Institute of Brussels, Brussels, and Innogenetics,
Industriepark Zwijnaarde, Ghent,4 Belgium
Received 4 May 1999/Returned for modification 14 June 1999/Accepted 5 October 1999
C57BL/6, C3H, and BALB/c mice were vaccinated with plasmids
encoding Toxoplasma gondii antigens GRA1, GRA7, and ROP2,
previously described as strong inducers of immunity. Seroconversion for
the relevant antigen was obtained in the majority of the animals. T. gondii lysate stimulated specific T-cell proliferation
and secretion of gamma interferon (IFN-
0019-9567/0/$04.00+0
Copyright © 2000, American Society for Microbiology. All rights reserved.
DNA Vaccination with Genes Encoding
Toxoplasma gondii Antigens GRA1, GRA7, and ROP2 Induces
Partially Protective Immunity against Lethal Challenge in
Mice
) in spleen cell cultures from vaccinated BALB/c and C3H mice but not in those from control mice.
Although not proliferating, stimulated splenocytes from DNA-vaccinated
C57BL/6 mice also produced IFN-
. No interleukin-4 was detected in
the supernatants of lysate-stimulated splenocytes from DNA-vaccinated
mice in any of the mouse strains evaluated. As in infected animals, a
high ratio of specific immunoglobulin G2a (IgG2a) to IgG1 antibodies
was found in DNA-vaccinated C3H mice, suggesting that a Th1-type
response had been induced. For BALB/c mice, the isotype ratio of the
antibody response to DNA vaccination was less polarized. The protective
potential of DNA vaccination was demonstrated in C3H mice. C3H mice
vaccinated with plasmid encoding GRA1, GRA7, or ROP2 were partially
protected against a lethal oral challenge with cysts of two different
T. gondii strains: survival rates increased from 10% in
controls to at least 70% after vaccination in one case and from 50%
to at least 90% in the other. In vaccinated C3H mice challenged with a
nonlethal T. gondii dose, the number of brain cysts was
significantly lower than in controls. DNA vaccination did not protect
BALB/c or C57BL/6 mice. Our results demonstrate for the first time in an animal model a partially protective effect of DNA vaccination against T. gondii.
*
Corresponding author. Mailing address: Department of
Toxoplasmosis, Pasteur Institute, Engelandstraat 642, B-1180
Brussels, Belgium. Phone: 32.2.373.32.03. Fax:
32.2.373.32.81. E-mail:
mvercamm{at}ben.vub.ac.be.
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