Vaccination with a DNA vaccine encoding Toxoplasma gondii ROP54 induces protective immunity against toxoplasmosis in mice

•T. gondii ROP54 can modulate some aspects of the host immune response.•Vaccination with T. gondii ROP54 DNA vaccine induced strong humoral and cellular responses.•Significant reduction in brain cyst number was observed after vaccination with pVAX-ROP54.•Vaccination with pVAX-ROP54 resulted a significant prolonged the mice survival time.•ROP54 might be a potential vaccine candidate against acute and chronic toxoplasmosis.

Toxoplasma gondii is an obligatory intracellular protozoan, which infects most of the warm-blooded animals, causing serious public health problems and enormous economic losses worldwide. The rhoptry effector protein 54 (ROP54) has been indicated as a virulence factor that promotes Toxoplasma infection by modulating GBP2 loading onto parasite-containing vacuoles, which can modulate some aspects of the host immune response. In order to evaluate the immuno-protective value of ROP54, we constructed a eukaryotic recombinant plasmid expressing T. gondii ROP54 and intramuscularly immunized Kunming mice with this recombinant plasmid against acute and chronic toxoplasmosis. All mice immunized with pVAX-ROP54 elicited a high level of specific antibody responses, a significant increase of lymphocyte proliferation, and a significant level of Th1-type cytokines (IFN-γ, IL-2 and IL-12p70), in addition to an increased production of Th2-type cytokines (IL-4 and IL-10). These results demonstrated that pVAX-ROP54 induced significant cellular and humoral (Th1/Th2) immune responses, which extended the survival time (13.0 ± 1.15 days for pVAX-ROP54 vs 6.7 ± 0.48 days for pVAX I, 6.8 ± 0.42 days for PBS and 6.5 ± 0.53 for blank control) and significantly reduced cyst burden (35.9% for pVAX-ROP54, 1% for pVAX I and 2% for PBS, compared with blank control) of immunized mice. These results indicate that the recombinant ROP54 plasmid can provide partial protection and might be a potential vaccine candidate against acute and chronic toxoplasmosis.

Graphical abstractThe recombinant ROP54 plasmid can provide partial protection and might be a potential vaccine candidate against acute and chronic toxoplasmosis.Download high-res image (57KB)Download full-size image