COMPARATIVE EXPRESSION OF THE prM/E GENES OF CENTRAL EUROPEAN ENCEPHALITIS (CEE) VIRUS FROM STABLYTRANSFORMED INSECT CELL LINES AND FROM CELLS INFECTED WITH RECOMBINANT BACULOVIRUSES

Abstract

To attempt to identify a convenient system for producing large quantities of antigen for diagnosis of tick-borne encephalitis, the expression of the prM/E genes of Central European encephalitis (CEE) virus was compared in different insect cell systems: recombinant baculovirus infected cell cultures and stablytransformed cell lines. Recombinant baculoviruses were prepared that expressed the prM/E genes of CEE under control of the immediate early promoter, ie1, or two late promoters, polyhedrin or p10, of the baculovirus Autographa californica nuclear polyhedrosis virus. These recombinant baculoviruses were used to infect cultured Spodoptera frugiperda (Sf9) and Trichoplusia ni (T. ni) insect cells. Expressed prM and E proteins were readily detected by radiolabeling and immunoprecipitation. Both of the late promoter recombinants produced more of the expressed proteins than did the early promoter recombinant. Stable lines of Sf9 and T. ni cells were produced with the prM/E genes inserted into the host chromosomes under control of ie1. This provided an insect cell line that could continuously express and secrete the CEE proteins allowing the antigen to be collected from the supernatant indefinitely. Stably- transformed Sf9 and T. ni cells secreted prM/E subviral particles. Particles were characterized and compared to those from a wild-type tick-borne encephalitis (TBE) complex virus, Langat (LGT) virus. The subviral particles recovered from supernatants of the stably-transformed cells were demonstrated to be spherical particles with a diameter of about 35 nm and a density of 1.14 g/cm3.