Sindbis Vectors Suppress Secretion of Subviral Particles of Japanese Encephalitis Virus from Mammalian Cells Infected with SIN-JEV Recombinants

Double-subgenomic Sindbis virus (dsSIN) recombinants that express cassettes encoding prM-E or a C-terminally truncated form of E of Japanese encephalitis virus (JEV) were constructed. The products were efficiently expressed in both mammalian and mosquito cell lines infected with the dsSIN recombinants. However, suppression of prM-E secretion from mammalian cells infected with dsSIN-prM-E recombinants was observed. This suppression was more pronounced late in infection (50% during an 8-hr chase). The prM-E secreted from both mammalian and mosquito cells was in the form of subviral particles as determined by velocity gradient centrifugation, sensitivity to nonionic detergent, and analysis of processing of N-linked glycans. The truncated E protein expressed by the dsSIN recombinants was secreted efficiently from both mammalian and mosquito cells. Coinfection experiments with the dsSIN-JEV recombinants + wild-type vaccinia virus and vP829 + SIN demonstrated that the reduced level of secretion of subviral particles exhibited by the dsSIN-JEV recombinants was due to an inhibitory effect of the dsSIN vectors. Furthermore, this inhibitory effect was accounted for by the SIN nonstructural proteins since SIN replicons that express prM-E cassette in place of the SIN structural protein open reading frame exhibited a low level of subviral particle secretion. No self-propagating infectious particles were produced in cells transfected with SIN replicons that encode the JEV prM-E cassette. The suppression of subviral particle secretion was apparently correlated with the inhibition of cell protein synthesis which is mediated in SIN-infected vertebrate cells by expression of the SIN nonstructural proteins.