[Protective effect of radix sophorae flavescentis mixture on intestinal mucosa in mice infected with Cryptosporidium parvum].

Objective: To investigate the protective effect of radix sophorae flavescentis (RSF) mixture on intestinal mucosa in mice infected with Cryptosporidium parvum.

Methods: Thirty BALB/c male mice were randomly divided into control group, infection group and RSF mixture treatment group. Mice of the posterior two groups were inoculated intragastrically with 1 x 10(5) C. parvum oocysts, immunosuppressed with dexamethasone (5 microg/ml) and gentamycin sulfate (40 microg/ml) in drinking water. At the 8th day post-infection, mice in RSF mixture treatment group were treated with 0.2 ml dose of RSF mixture twice a week (three-day intervals) for three weeks. The mice in infection group and RSF mixture treatment group were monitored for oocyst shedding in fecal pellets every two days after treatment. At 28 days after infection, experimental mice were sacrificed, jejunal tissue was removed for preparation of paraffin-embedded sections. The changes of CD3+, CD4+, CD8+ T lymphocytes and IgA plasmocytes in intestinal mucosa were determined by immunohistochemistry. In addition, jejunum of infected mice and treated mice were collected, and ultrastructural changes were observed under electron microscopy.

Results: Compared with infection group, the level of oocyst shedding was obviously lower and the time of the oocyst discharging was significantly shorter in RSF mixture treatment group. The proportion of CD3+, CD4+ T lymphocyte and CD4+/CD8+ T cell ratio in infection group (49.7% +/- 2.4%, 25.7% +/- 2.2%, 1.1 +/- 0.3) were significantly lower than that of treatment group (62.4% +/- 1.4%, 37.5% +/- 3.1%, 1.5 +/- 0.3) and control group (66.5% +/- 1.9%, 40.1% +/- 1.8%, 1.5 +/- 0.2) (P < 0.01). CD8+ T lymphocytes showed no significant difference in each group (P > 0.05). The number of IgA plasmocytes in treatment group (52.7 +/- 3.5) was significantly higher than that of control group (8.3 +/- 2.3) and infection group (33.7 +/- 2.6) (P < 0.01). After administration for three weeks, the damaged C. parvum parasites were seldom seen in mouse jejunum, and lysosomes appeared in large number, RSF mixture treatment improved mitochondrial structure and repaired microvilli. In infection group, mitochondria ridges were significantly broken and microvilli surrounding C. parvum oocysts were shed, resulting in the appearance of crater-like lesions on the surface, the oocyst wall and host cell membrane fused together.

Conclusion: RSF mixture is effective against Cryptosporidium parvum. The damage of intestinal mucosa in infected mice can be repaired after treatment.