Abstract:

Objective To investigate the levels of serum amyloid P component in the lung and brain tissues in different stages in fourteen-day old BALB/c suckling mice infected with EV71.Methods Mice were randomly divided into two groups, the experimental group with 35 suckling mice and the control group with 29 suckling mice. Animals in the experimental group were injected intraperitoneally with 0.1 mL 1 × 107 TCID50/mL EV71 stocks, and those in the mock control group were mock-infected with an equal amount of phosphate-buffered saline (PBS). Mice were monitored daily to observe activity, rash, reactivity, hair color, physical activity and paralysis, and experimental group was divided into 5 stages according to the signs and symptoms of infection. Mental reaction period (day 2), partial paralysis period (day 3), paralysis stage (day 3), death (3-4 days) and the convalescent phase (on day 10 mice were still alive). 6-8 mice that showed lethargy, weakness, limb shake, or paralysis were chosen, and killed upon symptom onset. Other survivors were monitored for up to 10 days and then killed. Tissue samples, including brain and lung, were collected from the mice. Levels of SAP were determined by enzyme-linked immunosorbent assay (ELISA) and the changing trend of SAP levels in different stages was analyzed.Results ①Mice showed less activity on day 2 post-infection and some were limb shake, some even paralysis to death on day 3 post-infection. It suggested that EV71 infected mice model was established successfully. There was no significant difference in body weight between the experimental group and the control group during the period of mental reaction, but the difference was statistically significant between two groups in the period of partial paralysis, paralysis, death and recovery period. ③ There was significant difference of SAP levels in both lung and brain tissues between the experimental groups and controls in five stages (P<0.05). In the experimental group, level of brain SAP was 2-9 times than that in the control group, and level of SAP in lung tissues was 1.5-8 times than in the control group. Brain SAP levels in experimental group in partial paralysis, paralysis period and period of death were significantly higher than those in mental reaction period (P<0.05). But it showed no statistical significance in lung between partial paralysis, paralysis, death and the convalescent. Levels SAP of recovery period decreased significantly in brain and lung tissue than those in period of mental reaction, but still higher than the level of the control group.Conclusion SAP is highly expressed in the brain and lung tissues of suckling mice infected with EV71, and it may be used as an index for judging the severity and prognosis of EV71 infection.