Toxoplasma gondii α‐amylase deletion mutant is a promising vaccine against acute and chronic toxoplasmosis

Abstract

Individuals with inhibited immunity may develop lethal toxoplasmosis; thus, a safe and effective vaccine is urged to be developed. Toxoplasma gondii (T. gondii) a-amylase (a-AMY) is one of the enzymes responsible for starch digestion. In the present study, we first generated a ME49Da-amy mutant and discovered that loss of a-AMY robustly grew in vitro but contributed to significant virulence attenuation in vivo. Therefore, we established a mouse model to explore the protective immunity of Da-amy mutant against acute and chronic toxoplasmosis. The results indicated that the survival rates of short-term or long-term immunized mice re-infected with the tachyzoites of multiple T. gondii strains were nearly 100%. ME49Da-amy not only could provide protective immunity against tachyzoites infection but also could resist the infection of tissue cysts. Furthermore, we detected that ME49Da-amy vaccination could effectively eliminate the proliferation of parasites in mice and prevent the formation of cysts. The significant increases of Th1-type cytokines, Th2-type cytokines and specific total IgG and IgG subclasses (IgG2a and IgG1) confirmed efficiency of a combination of cellular and humoral immunity against infection. In conclusion, ME49Da-amy attenuated strain can produce strong immune responses to provide efficient protection against toxoplasmosis, which signifies that ME49Da-amy mutant may be a potential vaccine candidate.

Starch Branching Enzyme 1 Is Important for Amylopectin Synthesis and Cyst Reactivation in Toxoplasma gondii

“…In addition, the fluorescence intensity of PAS staining also affirmed that the amylopectin level in the Δsbe1 and Δα-amyΔsbe1 mutants was lower than that in the ME49 strain during the tachyzoite and bradyzoite stages, showing a significantly enhanced fluorescence signal in bradyzoites ( Fig. 4E and 4G ), which was consistent with previous research ( 21 ). The above results further confirmed that SBE1 plays a vital role in amylopectin synthesis.…”

“…Based on our previous study ( 21 ), the loss of amylopectin degrading enzyme α-AMY caused abnormal amylopectin accumulation in bradyzoites, alleviated virulence, and decreased brain cyst formation. Furthermore, the absence of SBE1 led to starch synthesis defects but did not affect virulence and brain cyst formation.…”

“…2B ). It has been reported that deletion of amylopectin metabolic pathway enzymes has no effect on tachyzoite growth, yet may reduce brain cyst formation ( 14 , 21 ). However, the result was beyond expectation that the absence of SBE1 has almost no influence on brain cyst formation ( Fig.…”

Deletion of Toxoplasma Rhoptry Protein 38 (PruΔrop38) as a Vaccine Candidate for Toxoplasmosis in a Murine Model

“…As a result, we used varied genotypes of tachyzoites (RH, Pru, VEG, and TgcatBJ1) to assess the protective efficacy of PruΔ rop38 , with TgcatBJ1 being a ToxoDB#9 genotype strain isolated from stray cats [ 18 ]. Several atypical isolates are also commonly used in experiments to evaluate the efficacy of vaccine strains, such as the ToxoDB#9 genotype tachyzoites PYS [ 7 ], TgC7 [ 32 ], and C7719 [ 13 ], as well as the ToxoDB#3 tachyzoites WH-1 [ 33 ]. PruΔ rop38 could provide effective protection to mice against challenge by tachyzoites of varied genotypes.…”

Advances in Toxoplasma gondii Vaccines: Current Strategies and Challenges for Vaccine Development

“…Deleting carbamoyl phosphate synthetase II, an enzyme crucial for pyrimidine biosynthesis in T. gondii RH strain, conferred partial protection in mice [ 91 ]. Immunizing mice with the α-amylase knockout type II ME49 mutant invoked both cellular and humoral immune response and inhibited parasite proliferation [ 92 ]. Mice immunized with the adenylosuccinate lyase-deficient ME49 were protected upon a challenge infection with the type I RH, type II ME49, and type III VEG strains [ 93 ].…”