Resistance of C57BL/6 Mice to Different Artemisinin-sensitive Strains of PbK173 / 中国实验方剂学杂志

ABSTRACT

ObjectiveThe tolerance of C57BL/6 mice to artemisinin-sensitive and -resistant strains of Plasmodium berghei （Pb） K173 and the differences in blood parameters， spleen coefficient and spleen structure during infection were compared to explore whether the artemisinin resistance of Pb would aggravate malaria infection. MethodPbK173 artemisinin-sensitive and -resistant strains were tested in parallel. C57BL/6 mice were randomly divided into 1 control group， 4 artemisinin-sensitive strain groups and 4 artemisinin-resistant strain groups by body weight. Each infection group was simultaneously inoculated （ip） with 1×107 infected red blood cells （iRBCs） of sensitive/resistant strain. For the mice in the survival test group， the body weight was recorded every day post infection， and the tail vein blood smear was collected to calculate the Pb infection rate. In the other infection groups， peripheral blood and spleen were collected on 2， 5 and 9 d after infection. Peripheral blood parameters， spleen coefficient， pathological section of spleen and spleen cells were detected in each group. ResultOn 1-3 d after infection， the infection rate of the resistant strain （0.4±0.0， 0.8±0.1， 1.9±0.4）% was always higher than that of the sensitive strain （0.2±0.1， 0.4±0.1， 1.1±0.3）% （P<0.01）. From the 4th d of infection， the infection rate of the two groups gradually approached. The survival period of the sensitive strain group （20.5±1.2） d was shorter than that of the resistant strain group （23.3±1.4） d （P<0.01）. On the 9th d， the white blood cell count of the sensitive strain group （16.2±1.1）×109 cells/L was higher than that of the resistant strain group （10.6±1.8）×109 cells/L （P<0.01）. Flow cytometry analysis of spleen cells showed that the sensitive strain group （3.6±0.4） demonstrated a higher CD4+/CD8+ value than the resistant strain group （2.3±0.2） on the 9th d （P<0.01）. The spleen of C57BL/6 infected mice was gradually enlarged during infection， and on the 9th d， the resistant strain group （3.1±0.1）% showed a higher spleen coefficient than the sensitive strain group （2.7±0.2）% （P<0.01）. In the early stage of C57BL/6 infected mice， the red pulp of spleen was hyperemic and swollen. On the 9th d， the marginal area of the spleen disappeared and the structure of the red and white pulp was destroyed. ConclusionWithout drug treatment， the protective immune responses of peripheral blood and spleen of C57BL/6 mice were more sensitive to PbK173 artemisinin-sensitive strain. The artemisinin-resistant strain of PbK173 bred with mouse-to-mouse blood transmission and increased artemisinin dose exhibited shortened growth period and reduced toxicity.