低剂量隐孢子虫感染正常和免疫抑制小鼠的效应研究

目的 研究低剂量隐孢子虫感染正常和免疫抑制小鼠的相关效应指标，了解低剂量隐孢子虫感染的风险及相关效应。方法 采用地塞米松作为免疫抑制剂，建立小鼠的免疫抑制模型，再给予不同剂量的隐孢子虫攻击，比较不同的效应指标。结果 免疫抑制组小鼠脾重指数、胸腺指数与对照组比较差异有显著性（P〈0．05）。免疫抑制小鼠IgG、IgM含量与对照组比较差异亦有显著性（P〈0．05）。免疫抑制情况下粪便白细胞计数与相应的对照组比较，50、100、500个卵囊剂量组之间差异均有显著性（P〈0．05）。免疫抑制组与对照组的腹泻发生率，500个剂量组差异有显著性（P〈0．05）。将剂量对数和腹泻发生率作回归分析，免疫抑制和对照组的剂量对数和腹泻发生率呈现较好的线性关系（P〈0．05）。结论 较低剂量（10～50个卵囊）的隐孢子虫即可引起小鼠感染并出现腹泻症状，且出现粪便白细胞排出增加。在较低剂量条件下，免疫抑制小鼠粪便白细胞、腹泻发生率均高于相应的对照组，且潜伏期缩短，免疫抑制小鼠感染低剂量隐孢子虫发病的风险更大。

Study on the efficacy of low amount Cryptosporidium infection to immunocompetent and immunosuppressed mice

Objective To study the risk and efficacy of infection with low dosage of Cryptosporidium to immunosuppressed mice or immunocompetent mice. Methods The immunosuppressed animal model was established by DEX administration. The immunosuppressed mice infected with different amount of Cryptosporidium were contrasted with immunocompetent mice which were infected with same amount. Results The spleen and thymus weight index of immunosuppressed mice were significantly (P<0.05) lower than that of immunocompetent mice. The serum IgG and IgM of immuosuppressed mice were also significantly (P<0.05) lower than that of immunocompetent mice. The count of leukocytes in feces of immunosuppressed mice were significant different (P<0.05) from that of immunocompetent mice in 50-, 100-, and 500-oocyst infection groups. It was showed that the morbidity of diarrhea was statistically higher when compared with immunocompetent mice in 500-oocyst infection group (P<0.05), and possessed good regression (P<0.05) in both immunosuppressed groups and control groups. Conclusion The results shows that lower count of Crytosporidium oocyst (10 to 50) could make mice affected and result in diarrhea with increasing count of leukocytes in feces. The morbidity of diarrhea is higher and the incubation period is shorter in immunosuppressed mice. It is indicated that immunosuppression can make mice more susceptible to lower amount Cryptosporidium infection.