ABSTRACT
Objective:To investigate the regulation and mechanism of chronic Trichinella spiralis ( Ts) infection on liver immunopathology in mice co-infected with Plasmodium berghei ANKA( PbA). Methods:According to body weight, 64 specific pathogen free female Kunming mice (6 - 8 weeks old, weighting 22 - 25 g) were divided into 4 groups by using random number table method. Control group: uninfected; Ts group: mice were mono-infected with 30 Ts larvae by oral gavage on day 0; PbA group: mice were mono-infected with 1 × 10 6PbA-infected red blood cells in 0.1 ml of phosphate buffer (PBS) administered by intraperitoneal injection on day 121; co-infected ( Ts+PbA) group: mice were infected with 30 Ts larvae by oral gavage and intraperitoneal injected with 1 × 10 6PbA-infected red blood cells in 0.1 ml PBS on day 121 after Ts infection. There were 16 mice in each group, in which 10 mice in each group were monitored for the survival rate. The peripheral red blood cell parasitemia of PbA group and Ts + PbA group were monitored every other day by light microscope examination of Giemsa-stained thin tail-blood smears from day 3 after PbA infection. Mice were sacrificed at day 135 after Ts infection and/or at day 15 after PbA infection, the mouse body weight and liver weight were measured, and the liver index were calculated. Ts-infected mice were monitored by a light microscope examination of diaphragm compression slide. Under a light microscope, the liver pathology and liver fibrosis of mice were observed and compared with hematoxylin-eosin (HE) staining and Sirius red staining, respectively. The F4/80 + Kupffer cells in liver of mice were examined by immunohistochemical staining. Results:After infection with Ts or PbA, Ts larvae cysts were observed in diaphragm tissues and PbA were observed in red blood cells under the light microscope. After PbA infection, there was no significant difference in survival rate between PbA group and Ts+ PbA group ( P > 0.05). Compared with PbA group, the peripheral red blood cell parasitemia was significantly decreased in Ts+ PbA group on days 11 and 15 after PbA infection (%: 27.104 ± 7.623 vs 45.032 ± 9.849, 60.218 ± 2.776 vs 76.778 ± 6.351, P < 0.05), and the liver index and the liver pathology score were significantly decreased in Ts+ PbA group ( P < 0.05). Sirius red staining showed that the positive area of liver fibrosis in Ts+ PbA group was significantly higher than that in PbA group ( P < 0.05). Immunohistochemical staining showed that the average optical density value of F4/80 + Kupffer cells in Ts+ PbA group was significantly higher than that in PbA group ( P < 0.01). Conclusion:Chronic Ts infection may reduce the peripheral red blood cell parasitemia, increase F4/80 + Kupffer cells expression in liver, and attenuate liver pathology in mice co-infected with PbA.