Toxoplasma gondii (T. gondii) rhoptry
proteins (TgROPs) have been considered main targets and
indicator molecules for immune diagnosis and prophylaxis since they initially present during the process of invasion. In this study, the effect of intramuscularly injecting the genetic
vaccine pVAX-ROP22 was evaluated, made by inserting the TgROP22 sequence into the eukaryotic expression vector of pVAX I, into BALB/c mice. The levels of
IgG,
IgG1, and
IgG2a in pVAX-ROP22 vaccinated animals were integrally increased. It was uncovered by
cytokine profile analyses that the levels of IFN-γ and
IL-2 were significantly increased, while no significant changes were detected in
IL-4 and
IL-10 levels. In addition, we found that immunization with pVAX-ROP22 significantly prolonged the survival time (13.80 ± 1.75 d) of mice after challenge
infection with the virulent T. gondii RH strain, in comparison with those of control animals (died within 10 d). Moreover, the number of brain
cysts (1,406 ± 277) in the animals subjected to pVAX-TgROP22 vaccination decreased remarkably (P < 0.05) compared with the blank control mice (2,333 ± 473), and the size of brain
cysts in pVAX-TgROP22 group was significantly smaller than the groups of blank, PBS and pVAXI. These results suggested that TgROP22 as
DNA vaccine could trigger strong humoral and cellular responses and induce partial protection against
toxoplasmosis.