Intranasal immunization with Toxoplasma gondii SAG1 induces protective cells into both NALT and GALT compartments

Abstract

Intranasal (i.n.) immunization with the SAG1 protein of Toxoplasma gondii plus cholera toxin (CT) provides protective immunity. The aim of this study was to analyze the cellular activation of several mucosal compartments after i.n. immunization. Cervical and mesenteric lymph node (CLN and MLN, respectively) lymphoid cell and intraepithelial lymphocyte (IEL) passive transfer experiments were performed with CBA/J mice immunized i.n. with SAG1 plus CT. CLN and MLN cells and IEL isolated 42 days after immunization conferred protective immunity on naive recipient mice challenged with strain 76K T. gondii, as assessed by the reduction in the number of brain cysts. There were proliferative specific responses in nose-associated lymphoid tissue and the CLN and MLN cells from mice immunized with SAG1 plus CT, but no cytokine was detectable. Thus, protective immunity is associated with a specific cellular response in the nasal and mesenteric compartments after i.n. immunization.

FIG. 1

Adoptive transfer of CLN and MLN primed with SAG1 plus CT to CBA/J mice. For MLN and CLN adoptive transfer, six naive mice were given around 3 × 10⁷ cells from donor mice. They were challenged by the oral route with 80 cysts of strain 76K T. gondii 1 day after the transfer. Protection was assessed by counting the cysts in the brain 1 month later. Statistical significance was calculated by the ANOVA test as indicated by asterisks. For the SAG1-plus-CT group compared to the phosphate-buffered saline (PBS) or CT group: ∗∗, P < 0.0003; ∗, P < 0.01. The results are representative of two independent experiments.

FIG. 2

Adoptive transfer of SAG1-plus-CT-primed IEL to CBA/J mice. Six naive CBA/J mice were given 2 × 10⁶ primed or unprimed IEL from donors and challenged by the oral route with 80 cysts of strain 76K T. gondii 4 days after the transfer. These results are representative of two independent experiments. ∗∗, P < 0.01. PBS, phosphate-buffered saline.

FIG. 3

Phenotypic analysis of gut IEL subsets from CBA/J mice after immunization with SAG1 plus CT. Lymphocyte suspensions were prepared from four mice, and the relative percentages of Thy1.2⁺ or CD8β⁺ fluorescent IEL were determined by cytofluorimetric analysis of 5 × 10⁵ cells.