Clinical symptoms of mice infected with four rabies viruses and brain tissue histopathology observation

ObjectiveClinical symptoms and pathological change of mice brain infected with four strains rabies vi-ruses including fixed virulent virus strain CVS-24,Guangxi street virus strain GX074,avirulent virus strain rRC-HL and recombinant virus strain rRC-HL△G were compared to provide reference for revealing pathogenesis of rabies virus.MethodStrains CVS-24,GX074,rRC-HL and rRC-HL△G were injected into the brain of the SPF Kunming mice re-spectively,and the mice injected DMEM were as control.Each mouse was injected 30μL virus.After the mice were in-jected,body weight and death situation of them were observed continuously.Brain tissue from the dying mice was made into paraffin sections and the pathological change of brain tissue could be observed after H&E staining.ResultCom-pared with mice in DMEM group,the weight of mice in rRC-HL group first decreased and then returned to normal, whereas the weight of mice in other injected groups rapidly decreased until death.The mice in DMEM group and rRC-HL group did not die during the entire test period.Mice in CVS-24 group,GX074 group and rRC-HLΔG group all died after the injection.In addition,dead mice in CVS-24 group occurred the earliest(day 5 after infection),and the mice all died on day 6 after infection.By observing the pathological changes of mouse brain tissue,it was found that the inflammatory response of brain tissue in rRC-HL group was the most serious.The nerve fibers were disordered,the neuronal cells were deformed,the edges of the cells were not clear,a small amount of cells contracted or even disappeared.Hippocampalglial cells infiltrated,neurotropic phenomena was obvious,and severe vascular cuffing were observed.The inflammatory re-sponse in rRC-HLΔG group was less serious.In GX074 and CVS-24 groups,slight pathological changes in mice brain tis-sues were observed,and a spot of neurotropic phenomena was found.ConclusionThe clinical symptoms of the three virulent strains(rRC-HLΔG,GX074,and CVS-24)are more obvious and the fatality rates are 100%.However,the in-flammatory response is milder than that of avirulent strains.It shows that the virulent strain of rabies virus might inhibit the occurrence of inflammatory reaction by inhibiting the production of pro-inflammatory cytokines in mice brain,there-by blocking the innate immune response of the mice brain,which is not conducive to elimination of the virus.