Complete protection against lethal Toxoplasma gondii infection in mice immunized with a plasmid encoding the SAG1 gene

TY - JOUR

T1 - Complete protection against lethal Toxoplasma gondii infection in mice immunized with a plasmid encoding the SAG1 gene

AU - Nielsen, H V

AU - Lauemøller, S L

AU - Christiansen, L

AU - Buus, S

AU - Fomsgaard, A

AU - Petersen, E

N1 - Keywords: Adoptive Transfer; Animals; Antibodies, Protozoan; Antigens, Protozoan; CD8-Positive T-Lymphocytes; Epitopes, T-Lymphocyte; Humans; Immunization; Mice; Mice, Inbred BALB C; Mice, Inbred C3H; Plasmids; Protozoan Proteins; Protozoan Vaccines; Th1 Cells; Toxoplasma; Toxoplasmosis, Animal; Vaccines, DNA

PY - 1999

Y1 - 1999

N2 - Infection with the protozoan parasite Toxoplasma gondii is transmitted to humans from infected animals by tissue cysts and oocysts excreted by cats. Immunization with inactivated parasites or recombinant proteins has at best shown partial protection. We constructed a plasmid expressing the SAG1 surface antigen of T. gondii, p1tPASAG1, and showed that animals immunized with the plasmid produce anti-SAG1 antibodies which recognize the native SAG1. Mice immunized with p1tPASAG1 showed 80 to 100% protection against challenge with the non-cyst-producing, virulent RH isolate, compared to an 80% mortality in mice immunized with empty plasmid, which is the greatest efficacy of any vaccine against T. gondii produced so far. The SAG1 molecule was analyzed for potential cytotoxic T-lymphocyte (CTL) epitopes, and four peptides with the best fit were synthesized. The ability of the peptides to stimulate gamma interferon production by CD8(+) T cells from p1tPASAG1-immunized mice was tested in an ELISPOT assay, and one new CTL epitope was identified. Adoptive transfer of CD8(+) T cells from p1tPASAG1-immunized to naïve mice showed partial protection. In conclusion, DNA vaccination with p1tPASAG1 gave effective protection in mice against T. gondii infection and the protection could be adoptively transferred by purified CD8(+) T cells.

AB - Infection with the protozoan parasite Toxoplasma gondii is transmitted to humans from infected animals by tissue cysts and oocysts excreted by cats. Immunization with inactivated parasites or recombinant proteins has at best shown partial protection. We constructed a plasmid expressing the SAG1 surface antigen of T. gondii, p1tPASAG1, and showed that animals immunized with the plasmid produce anti-SAG1 antibodies which recognize the native SAG1. Mice immunized with p1tPASAG1 showed 80 to 100% protection against challenge with the non-cyst-producing, virulent RH isolate, compared to an 80% mortality in mice immunized with empty plasmid, which is the greatest efficacy of any vaccine against T. gondii produced so far. The SAG1 molecule was analyzed for potential cytotoxic T-lymphocyte (CTL) epitopes, and four peptides with the best fit were synthesized. The ability of the peptides to stimulate gamma interferon production by CD8(+) T cells from p1tPASAG1-immunized mice was tested in an ELISPOT assay, and one new CTL epitope was identified. Adoptive transfer of CD8(+) T cells from p1tPASAG1-immunized to naïve mice showed partial protection. In conclusion, DNA vaccination with p1tPASAG1 gave effective protection in mice against T. gondii infection and the protection could be adoptively transferred by purified CD8(+) T cells.

M3 - Journal article

C2 - 10569750

SN - 0019-9567

VL - 67

SP - 6358

EP - 6363

JO - Infection and Immunity

JF - Infection and Immunity

IS - 12

ER -