[Research Advance on Toxoplasma gondii Rhoptry Protein 2 Family as Candidate Vaccine Molecules].

Toxoplasma gondii rhoptry protein 2 family (ROP2 family), secreted by the rhoptry, plays an important role in T. gondii invasion of host cells and its virulence. The ROP2 family members include ROP2, ROP4, ROP5, ROP8, ROP13, ROP16, ROP17, and ROP18. Recent studies have found that these members are potential vaccine candidates against toxoplasmosis, and can induce the protective immunity of the host. This paper reviews the research advance on the ROP2 family members as DNA or protein vaccines against toxoplasmosis.

Protective immunity induced by peptides of AMA1, RON2 and RON4 containing T-and B-cell epitopes via an intranasal route against toxoplasmosis in mice.

BACKGROUND: Toxoplasma gondii is a ubiquitous protozoan intracellular parasite, the causative agent of toxoplasmosis, and a worldwide zoonosis. Apical membrane antigen-1 (AMA1) and rhoptry neck protein (RON2, RON4) are involved in the invasion of T. gondii. METHODS: This study chemically synthesized peptides of TgAMA1, TgRON2 and TgRON4 that contained the T- and B-cell epitopes predicted by bioinformatics analysis. We evaluated the systemic response by proliferation, cytokine and antibody measurements as well as the mucosal response by examining the levels of antigen-specific secretory IgA (SIgA) in the nasal, vesical and intestinal washes obtained from mice after nasal immunization with single (AMA1, RON2, RON4) or mixtures of peptides (A1 + R2, A1 + R4, R2 + R4, A1 + R2 + R4). We also assessed the parasite burdens in the liver and brain as well as the survival of mice challenged with a virulent strain. RESULTS: The results showed that the mice immunized with single or mixed peptides produced effective mucosal and systemic immune responses with a high level of specific antibody responses, a strong lymphoproliferative response and significant levels of gamma interferon (IFN-γ), interleukin-2 (IL-2) and IL-4 production. These mice also elicited partial protection against acute and chronic T. gondii infection. Moreover, our study indicated that mixtures of peptides, especially the A1 + R2 mixture, were more powerful and efficient than any other single peptides. CONCLUSIONS: These results demonstrated that intranasal immunisation with peptides of AMA1, RON2 and RON4 containing T- and B-cell epitopes can partly protect mice against toxoplasmosis, and a combination of peptides as a mucosal vaccine strategy is essential for future Toxoplasma vaccine development.

Partial protective effect of intranasal immunization with recombinant Toxoplasma gondii rhoptry protein 17 against toxoplasmosis in mice.

Toxoplasma gondii (T. gondii) is an obligate intracellular protozoan parasite that infects a variety of mammals, including humans. An effective vaccine for this parasite is therefore needed. In this study, RH strain T. gondii rhoptry protein 17 was expressed in bacteria as a fusion with glutathione S-transferase (GST) and the recombinant proteins (rTgROP17) were purified via GST-affinity chromatography. BALB/c mice were nasally immunised with rTgROP17, and induction of immune responses and protection against chronic and lethal T. gondii infections were investigated. The results revealed that mice immunised with rTgROP17 produced high levels of specific anti-rTgROP17 IgGs and a mixed IgG1/IgG2a response of IgG2a predominance. The systemic immune response was associated with increased production of Th1 (IFN-γand IL-2) and Th2 (IL-4) cytokines, and enhanced lymphoproliferation (stimulation index, SI) in the mice immunised with rTgROP17. Strong mucosal immune responses with increased secretion of TgROP17-specific secretory IgA (SIgA) in nasal, vaginal and intestinal washes were also observed in these mice. The vaccinated mice displayed apparent protection against chronic RH strain infection as evidenced by their lower liver and brain parasite burdens (59.17% and 49.08%, respectively) than those of the controls. The vaccinated mice also exhibited significant protection against lethal infection of the virulent RH strain (survival increased by 50%) compared to the controls. Our data demonstrate that rTgROP17 can trigger strong systemic and mucosal immune responses against T. gondii and that ROP17 is a promising candidate vaccine for toxoplasmosis.

[Construction, expression and kinase function analysis of an eukaryocyte vector of rhoptry protein 17 in Toxoplasma gondii].

OBJECTIVE: To construct and express the eukaryocytic expression vector of rhoptry protein 17 of Toxoplasma gondii RH strain (TgROP17) and analyze its kinase function. METHODS: The open reading frame of TgROP17 gene was amplified from total RNA in T. gondii RH strain by RT-PCR, and cloned into p3 x Flag-CMV-14 vector to construct recombinant plasmid p3xFlag-CMV-14/TgROP17. After colony-PCR confirming, double restriction enzyme digestion and DNA sequencing, the eukaryotic expression vector p3xFlag-CMV-14/TgROP17 was transfected into HEK 293T cells. The target gene was examined by RT-PCR and the recombinant protein was detected by Western blotting. The kinase activity of TgROP17 was identified by Western blotting and its apoptotic function was assessed by flow cytometry. RESULTS: The size of RT-PCR product was 1 850 bp. The recombinant plasmid p3xFlag-CMV-14/ TgROP17 was confirmed by colony-PCR, double restriction enzyme digestion and DNA sequencing. RT-PCR and Western blotting analysis showed that TgROP17 was expressed in the p3xFlag-CMV-14/TgROPl7 transfected-HEK 293T cells rather than in mock cells. The amplified gene was with 1,850 bp and the target protein was about M, 70,000. Western blotting analysis showed that c-Jun was phosphorylated by TgROP17. Flow cytometry analysis indicated that camptothecin-induced apoptosis was inhibited by TgROP17 with an inhibition rate of 20.6% and 24.1% at 6 h and 12 h after coculture, respectively, which was higher than that of the control (P < 0.05). CONCLUSION: The eukaryotic expression vector p3xFlag-CMV-14/TgROP17 is constructed. TgROP17 has kinase activity and playes an anti-apoptosis role.

[Indications for colonoscopy examination and its disease distribution: a report of 5690 cases].

OBJECTIVE: To explore the indications for colonoscopy examination and the distribution of diagnostic diseases. METHOD: From Jan. 2000 to Dec. 2004, 5960 patients received colonoscopy examination in our colorectal center. The indications for colonoscopy examination and the distribution of its diagnostic diseases were analyzed. RESULTS: There were 3096 males and 2594 females,and the mean age was (52+/-15) years. The reasons for colonoscopy included hemafecia (26.9%), atypical abdominal pain (25.8%), diarrhea or increased frequency of stool (11.1%), anal tenesmus or discomfort (7.6%), constipation (7.0%),mucous or bloody purulent stool (3.0%), intra-rectal mass or abdominal mass on physical examination (0.9%), re- examination after colonoscopic polypectomy (10.9%), re-examination after operation for colorectal cancer(1.5%), simple health examination (2.2%). Colonoscope reached the cecum in 97.7% of the cases,and at least one disease was found in 2283 cases (40.1%). Among them,colorectal cancer accounted for 10.3%, colorectal polyps 19.6%, ulcerative colitis 4.3%, and Crohn's disease 0.5% respectively. CONCLUSION: The indications for colonoscopy are too strict to screen the early stage colorectal cancer. Colonoscopy should be performed in the cases with symptoms such as bloody stool, diarrhea, abdominal pain, constipation, or with colorectal polyps, after operation for colorectal cancer,or as members of hereditary colorectal cancer family.