DNA vaccination with a gene encoding Toxoplasma gondii GRA6 induces partial protection against toxoplasmosis in BALB/c mice

Parasit Vectors. 2011 Nov 9;4(1):213. [Epub ahead of print]

DNA vaccination with a gene encoding Toxoplasma gondii GRA6 induces partial protection against toxoplasmosis in BALB/c mice.

Sun XM, Zou J, Saeed A A E, Yan WC, Liu XY, Suo X, Wang H, Chen QJ.
Abstract
ABSTRACT:

BACKGROUND: Infection with protozoa Toxoplasma gondii causes serious public health problems and is of great economic importance worldwide. Protection from acute toxoplasmosis is known to be mediated by CD8+ T cells, but the T. gondii antigens and host genes required for eliciting protective immunity have been poorly defined. The T. gondii dense granule protein 6 (GRA6), recently proved to be highly immunogenic, produces fully immune protection in T. gondii infected BALB/c mice with an H-2Ld gene. The CD8+ T cell response of H-2Ld mice infected by the T. gondii strain seemed to target entirely to a single GRA6 peptide HF10-H-2Ld complex.

RESULTS: To determine whether GRA6-based DNA vaccine can elicit protective immune response to T. gondii in BALB/c mice, we constructed a eukaryotic expression vector pcDNA3.1-HisGRA6 and tested its immunogenicity in mouse model. BALB/c mice were vaccinated intramuscularly with three doses of GRA6 DNA and then challenged with a lethal dose of T. gondii RH strain tachyzoites. All immunized mice developed high levels of serum anti-GRA6 IgG antibodies, and in vitro splenocyte proliferation was strongly enhanced in mice adjuvanted with levamisole (LMS). Immunization with pcDNA3.1-HisGRA6 with LMS resulted in 53.3% survival of challenged BALB/c mice as compared to 40% survival of BALB/c without levamisole. Additionally, immunized Kunming mice without an allele of H-2Ld failed to survive.

CONCLUSIONS: Our result supports the concept that the immune response is MHC restricted. This study has a major implication for vaccine designs using a single antigen in a population with diverse MHC class I alleles.

PMID:22070984[PubMed - as supplied by publisher]