[Show abstract][Hide abstract] ABSTRACT: Microneme protein 3 (MIC3) is an important adhesion molecule expressed by Toxoplasma gondii and Neospora caninum that plays a crucial role in invasion. In our study, we found that recombinant TgMIC3 (rTgMIC3) was recognized by both T. gondii-reactive sera and hyper-immune serum against N. caninum. Polyclonal antibodies against TgMIC3 reacted with N. caninum by western blot and immunofluorescence assay (IFA). These results indicate that MIC3 is a novel cross-reactive antigen expressed in N. caninum and T. gondii. To evaluate the immune-protective effect of TgMIC3, we created the eukaryotic expression vector pcDNA3.1-TgMIC3, transfected this vector into HEK293T cells by lipofection, and evaluated TgMIC3 expression in HEK293T cells using western blot and IFA. Then, groups of BALB/c mice were immunized with recombinant TgMIC3 protein, pcDNA3.1-TgMIC3, or two-vaccine immunization. The mice were challenged with T. gondii RH or N. caninum Nc-1 tachyzoites 14 days after the final immunization. The survival time of T. gondii-infected mice was recorded, and the parasite burden in the brain of N. caninum-infected mice 30 days post-infection was measured using real-time PCR. The results demonstrated that mice immunized with TgMIC3-based vaccines elicited high antibody titers. After parasitic challenge, mice immunized with pcDNA-TgMIC3 exhibited prolonged survival when infected with T. gondii tachyzoites and a lower parasitic burden in the brains of mice challenged with N. caninum tachyzoites. These results demonstrate that TgMIC3 is a cross-protective antigen expressed in T. gondii and N. caninum and could elicit some protection against toxoplasmosis and neosporosis.
No preview · Article · Jul 2015 · Parasitology Research
[Show abstract][Hide abstract] ABSTRACT: Cats are essential in the epidemiology of Toxoplasma gondii because they are the only hosts that can excrete the environmentally resistant oocysts in nature. This study was aimed to determine the seropositivity, distribution of genotypes and mouse virulence of T. gondii from stray cats in Beijing, China. A total of 64 serum samples, 23 feces and tissue samples were collected from stray cats in Beijing. Antibodies to T. gondii were assayed by the modified agglutination test (MAT). 57.8% (37/64) of these stray cats had titers of 1:20 or higher and were considered positive with infection. T. gondii oocysts were not found in feces of the 23 cats. Tissues of 23 cats were bioassayed in mice and 11 T. gondii isolates were obtained. The genotype of these isolates were identified by 11 PCR-RFLP markers, including SAG1, (3'+5')SAG2, alt.SAG2, SAG3, BTUB, GRA6, c22-8, c29-2, L358, PK1, and an apicoplast marker, Apico. Only one genotype was identified. This genotype, designated as ToxoDB genotype #9, was previously reported in cats, pigs and human from Guangdong and Gansu provinces in China and animals from a few other countries. To determine mouse virulence of this lineage of parasites, one isolate was randomly selected and inoculated into BABL/c mice, the result showed that it is intermediately virulent to mice. These results indicated that an atypical, intermediately virulent T. gondii lineage is widespread in China. The high seropositivity of T. gondii in stray cats posts potential risk of transmission of the parasite to human population in the region.
No preview · Article · Jan 2012 · Veterinary Parasitology