TRANS-ENCAPSIDATION OF A POLIOVIRUS REPLICON BY DIFFERENT PICORNAVIRUS CAPSID PROTEINS

A trans-encapsidation assay was established to study the specificity o f picornavirus RNA encapsidation. A poliovirus replicon with the lucif erase gene replacing the capsid protein-coding region was coexpressed in transfected HeLa cells with capsid proteins from homologous or hete rologous virus. Successful tuans-encapsidation resulted in assembly an d production of virions whose replication, upon subsequent infection o f HeLa cells, was accompanied by expression of luciferase activity. Th e amount of luciferase activity was proportional to the amount of tran s-encapsidated virus produced from the cotransfection. When poliovirus capsid proteins were supplied in trans, >2 x 10(6) infectious particl es/ml were produced. When coxsackievirus B3, human rhinovirus 14, meng ovirus, or hepatitis A virus (HAV) capsid proteins were supplied in tr ans, all but HAV showed some encapsidation of the replicon. The overal l encapsidation efficiency of the replicon RNA by heterologous capsid proteins was significantly lower than when poliovirus capsid was used, trans-encapsidated particles could be completely neutralized with spe cific antisera against each of the donor virus capsids. The results in dicate that encapsidation is regulated by specific viral nucleic acid and protein sequences.