The Temporal And Spatial Distribution Of A Variant And A Classic Pseudorabies Virus In Mice Via Intranasal Route Infection

In recently years,the attenuated strain vaccine could not provided fully protection for the emerging of variant pseudorabies virus(PRV)strains.The outbreaks of pseudorabies(PR)in domestic swine farms were resulting in sizable economic loss.In this study,we used the variant strain PRV(LY-2015)and the classic strain PRV(Halv)infected the SPF Kunming mice via intranasal route.Through immunohistochemical(IHC),in situ hybridization and PCR,we located the virus distribution in brain.The propagated of the virus in neurons system were conducted by detected the virus distribution in various periods.The research served to fill the gaps in the study of the virus distribution in the mice brain infected with variant strains of PRV to lay a foundation for precise diagnosis and inpediment of transmission.1 The Clinical Symptoms of the Infected MiceIn the group of LY-2015 PRV(2,000TCID50),the mice began to appeal coarse,lethargic,anorexic and show clinical symptoms at 48 h.p.i..After 60h's infection,there were indication of excitement and scratching facial skin at 60 h.p.i..while At 84 h.p.i.,the majority of mice possessed of skin burst due to the scratching and the mice died.As for mice infected with the same titer of the classical strains PRV,no symptoms were observed.In the group of Halv PRV(10,000TCID50),the clinical symptoms which similar to the LY-2015 group began to appear 72 h.p.i,and there were mass mortality at 96 h.p.i.It proved that virulent of pseudorabies variant LY-2015 PRV is stronger than the Halv PRV.2 The ascending pathway of virus infectionAfter mice being infected with the LY-2015 PRV,the virus first appeared in the nasal mucosa epithelial cells and then particles from trigeminal nerve nucleus,sympathetic nerve nucleus and facial nerve nucleus all detected,indicating through which the virus went up and caused central nerve infection.While after mice being infected with the Halv PRV,virus from trigeminal nerve nucleus,sympathetic nerve nucleus sympathetic nerve nucleus and parasympathetic nerve nucleus all detected,indicating that classic strain Halv PRV transmit along trigeminal nerve,sympathetic nerve and parasympathetic nerve for upgoing.3 The distribution of virus in infected mice brainMost of the virus distributed in spinal cord,pons and the majority part of medulla oblongata after infected mice with 2,000TCID50 of LY-2015 PRV.There are less virus in thalamus on the contrary.And at 84 h.p.i,the virus widely spread in brain.In the group of Halv PRV(10,000TCID50),the virus transmission to spinal cord,pons and medulla oblongata.There were plenty of particles in cerebrum as well.And it is the most widespread in brain at 96 h since the infection.It is demonstrated that the transmission of the classic strain is slower than the variant ascending in axon.And the LY-2015 PRV have stronger virulence.The mice resulted in a predating death after the infection.Only a small amount of virus transmit to the central nerve,which distributed in the lateral part of hypothalamus and under the thalamus nucleus in the middle.In addition,the IHC was negative at 120 h.p.i with 2,000TCID50 of LY-2015 PRV.But the ISH was positive.The result showed that the virus gene existed in cerebrum without the virus replication.It is indicated that the virus existed in the toleranced mice as latented infection after the mice infected by PRV.The virus gene integrated in peripheral nerve nucleus without replication.The results above illustrated that the LY-2015 PRV have stronger virulence than the Halv PRV.The Halv PRV could infected mice effectively only at higher virus titer.Under effective infection of Kunming mice by intranasal inoculation,the pseudorabies variant(LY-2015)went up through trigeminal nerve nucleus,sympathetic nerve nucleus and facial nerve nucleus;most of the virus distributed medulla oblongata and pons.The classic(Halv)strain transmitted along trigeminal nerve,sympathetic nerve and parasympathetic nerve for upgoing;there were inapoortional plenty of virus in spinal cord,pons,medulla oblongata and cerebrum.When the infection is effective,the toleranced mice indicated being latently infected,with no sign of clinical symptoms,and virus gene was integrated in the cell included of peripheral nerve,while the gene did not complete replication.