Research Of Pathogennicity And Paneth Cell Lesions In Kunming Mice Fed ToxoDB#17 Strain Toxoplasma Gondii Oocysts

To study the pathogencity and distribution in Kunming mice fed Toxo DB#17 strain oocysits,this paper was studied in 4 weeks Kunming mice after feeding 104 oocysts/mice,105 oocysts/mice,106 oocysts/mice of Toxo DB#17 sporulated oocysts.Three mice of each group were killed At 6 hours after inoculation(HAI)and 1,3,8 days after inoculation(DAI).Tissues of all organs including the small intestine were made paraffin section,which were stained by HE(hematoxylin and eosin)and IHC(immunohistochemistry)to examine histological lesions and the distribution of T.gondii,the change of the quantity of Paneth cells,granules and lysozyme in the small intestine.The main findings were as follows:1.Procedure of isolation and identification of oocysts of Toxo DB#17 T.gondii.Antibodies to T.gondii were found in 21 of 42(50%)of cats by the modified agglutination test(cut-off 1:25).Viable T.gondii was isolated from tissues of eight of 21 seropositive but not from 21 seronegative(<1:25)cats.DNA derived from cell cultured tachyzoites of all nine T.gondii isolates was characterized by PCR–RFLP.Four genotypes were found;the genotypes oftissue isolates were Toxo DB #9 in six,Toxo DB #2 in one,and Toxo DB #17 in one.Feed the mice containing Toxo DB #17 brain cysts to serological negative cat and collect fresh cat feces every day.Centrifuge the cat feces after rinsing by the sucrose flotation solution,examined the smear with microscopy and checked unsporulated oocysts.Add 2% sulfuric acid solution and preservate at room temperature to make it sporulate.2.The pathogencity of Kunming mice fed Toxo DB#17 oocysts.Diluting the collected oocysts from 106 oocysts/ml to 1 oocysts/ml,and add moderate 3% sodium hydroxide(including phenol red)to neutralize it.Fed the oocysts to mice and observe the clinical symptoms and pathogencitty of mice.Depressed,arched,messy hair were temporary within a week in high consistency group,low concentration group were at normal mental state.Minimun lethal dose was 102 oocysts/ml,the shortest period of death was 37 days.3.The distribution of tachyzoites and lesions in organs.Three groups mince were all infected at every time points.Overall,the number of infected mice gradually increased as the dose increased as well as lesions.We found necrocytosis in mesenteric lymph nodes,spleen swelling,severe pulmonary congestion and perivascular inflammation.4.The relationship between small intestine lesions and positive area of toxoplasma gondii in mice fed oocysts.HI scoring results showed that as the infection time gone on the HI scoring showed the trend of decreased first and increased later.The results of immunohistochemical staining showed that as the infection time gone on the positive area of toxoplasma in the small intestine was increasing.Microscopic examination showed that intestine villus epithelial necrosis,hemorrhage in the lamina propria and lymphocyte proliferation,lamina propria was significant thickening,the capillaries in the lamina propria were serious hyperemia,lymphocytes infiltrate,the intestinal glands were destroyed,paneth cells and granules were lost or decrease.5.The results of the changes in crypt,Paneth cells and their granules.The total number of crypts,PCs in the intestine cross-section,granules of cross sections showed the trend of increased first and decreased later.6.The influence on Toxo DB#17 oocysts induced-murine lysozyme in the small intestine.The results of immunohistochemical staining showed that lysozyme in the small intestine were not expressed.