DOUBLE-SUBGENOMIC SINDBIS VIRUS RECOMBINANTS EXPRESSING IMMUNOGENIC PROTEINS OF JAPANESE ENCEPHALITIS-VIRUS INDUCE SIGNIFICANT PROTECTION IN MICE AGAINST LETHAL JEV INFECTION

A series of double-subgenomic Sindbis virus (dsSIN) recombinants that express cassettes encoding the immunogenic proteins of Japanese enceph alitis virus (JEV) [prM-E, prM-E-NSI, NSI-NS2A, 80%E (encodes the amin o-terminal 80% part of E), and NS1] were constructed and analyzed for their ability to confer protective immunity in mice against lethal cha llenge with neurovirulent JEV. The cassettes were introduced into both 5' [second subgenomic promoter of the vector precedes the SIN structu ral open reading frame (SP-ORF)] and 3' (the promoter follows the SP-O RF) dsSIN vectors. The longest cassette (prM-E-NSI) was 3.2 kb in leng th, which is remarkable for such a small vector virus as SIN (SIN geno me is roughly 11.8 kb in length). The level of expression of JEV prote ins appeared similar for both 5' and 3' recombinants. in general, the stability of the recombinants obtained was found to be low (expression was lost following one to five passages at low multiplicity of infect ion, depending on the recombinant). However, 5' recombinants containin g longer cassettes (prM-E-NS1, prM-E, NSI-NS2A) were more stable than the corresponding 3' recombinants. Intraperitoneal inoculation of mice with 10(7) PFU of dsSIN-JEV recombinants induced antibodies against J EV proteins and low titers of JEV-neutralizing antibodies were produce d by mice inoculated with recombinants expressing 80%E., prM-E, and pr M-E-NS1. A single immunization of mice with the dsSIN-prM-E or dsSIN-p rM-E-NS1 recombinants provided 40-65% protection against peripheral le thal challenge with 10(4) LD(50) of neurovirulent JEV. The results dem onstrate that genetically engineered togaviruses can be successfully u sed as vaccine vectors. (C) 1995 Academic Press, Inc.