ONE AMINO-ACID CHANGE ON THE CAPSID SURFACE OF POLIOVIRUS SABIN-1 ALLOWS THE ESTABLISHMENT OF PERSISTENT INFECTIONS IN HEP-2C CELL-CULTURES

Poliovirus mutants (PVpi) selected during the persistent infection of human neuroblastoma cells can establish secondary persistent infection s in nonneural HEp-2c cells (I. Pelletier, T. Couderc, S. Borzakian, E . Wyckoff, R. Crainic, E. Ehrenfeld, and F. Colbere-Garapin, 1991, Vir ology, 180, 729-737). Previous results from our laboratory have also s hown that, in the genome of PVpi S11 derived from the Sabin 1 strain, the genomic region involved in this phenotype contains 11 missense mut ations which map exclusively to the genes encoding the capsid proteins VPI and VP2. We report here the identification of precise viral deter minants able to confer the capacity to establish persistent infections in HEp-2c cell cultures to the lytic Sabin 1 strain. We used a strate gy based on the observation that PVpi, after a few months of persisten t infection in HEp-2c cells, tend to regain a more lytic phenotype in uninfected HEp-2c cell cultures. We constructed mutant Viruses carryin g only a few mutations potentially involved in the phenotype of persis tence. Two mutations were identified, one corresponding to the substit ution His>Tyr of amino acid 142 of VP2 and another corresponding to th e substitution Val>IIe of amino acid 160 of VP1. Mutants carrying one or the other of the two determinants established persistent infections in HEp-2c cell cultures in about 20% of the infections. Higher freque ncies were obtained with the mutant carrying both determinants (30%), and with PVpi S11 (63%), indicating that the effects of several determ inants can be cumulative. The two determinants are localized on the ca psid surface in a region known to be involved in the interactions betw een poliovirus and its cell receptor and in fact, we demonstrate here that in the case of the two persistent mutants, these interactions are modified. (C) 1998 Academic Press.