Effective subunit vaccines against an enveloped animal virus

Abstract

VACCINES are available to act against many of the diseases caused by enveloped viruses. The efficacy and safety of the vaccines depend on the method used to convert the virus into a vaccine. Whole viruses that have been attenuated or killed are effective, but both of these types of vaccines may give rise to undesirable side effects which limit their use1–3. These complications are caused by the virus genome or by toxic components in the virus preparations. The components that give rise to the side effects do not seem to be those that are important for evoking protective immunity and it is therefore possible to prepare vaccines which contain only the necessary antigenic subunits, which for the enveloped viruses are the spike glycoproteins4–7. But although subunit vaccines have proved safer than whole virus vaccines, their immunogenicity is generally lower8,9, perhaps because the form in which the proteins are presented in the vaccines is not optimal for eliciting a strong immune response10. In support of that explanation, we present here evidence that a lethal infection of mice with Semliki Forest virus can be prevented by a single vaccination with the virus spike protein, provided it is presented as a micellar aggregate of the protein or as protein reconstituted into vesicles of egg lecithin. The monomer form of the spike protein solubilised with detergent is very much less effective.