Antibody response to spike protein vaccines prepared from Semliki Forest virus

Subunit vaccines, containing the spike glycoproteins of Semliki Forest virus (SFV) in three different forms, have been prepared: detergent-solubilized monomers, detergent- and lipid-free octamers, and virosomes in which the spike proteins are reconstituted into phospholipid vesicles. Previous studies have shown that the octamers and the virosomes are very efficient in protecting mice against the encephalitis caused by virulent SFV (Morein, et al., 1978). In this study we have characterized the specific antibody responses in mice vaccinated with the three SFV vaccines and correlated them with the protection against SFV encephalitis. The multimeric forms induced high humoral antibody titres; two doses of only 1 microgram protein gave rise to specific antibody titres of 0.6 mg/ml. The monomeric form was much less immunogenic.