gms | German Medical Science

International Conference on SARS - one year after the (first) outbreak

08. - 11.05.2004, Lübeck

Expression of SARS protein and assembly of virus-like particles


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  • Eduardo Mortola - Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK
  • corresponding author presenting/speaker Polly Roy - Department of Infectious and Tropical Diseases, London School of Hygiene & Tropical Medicine, London, UK

International Conference on SARS - one year after the (first) outbreak. Lübeck, 08.-11.05.2004. Düsseldorf, Köln: German Medical Science; 2004. Doc04sars3.04

The electronic version of this article is the complete one and can be found online at:

Published: May 26, 2004

© 2004 Mortola et al.
This is an Open Access article distributed under the terms of the Creative Commons Attribution License ( You are free: to Share – to copy, distribute and transmit the work, provided the original author and source are credited.



An effective vaccine against the SARS virus needs to induce neutralizing antibodies. Since the S protein is the receptor binding protein, it is the main target for a protective humoral immune response. In animal models the S protein has been shown to induce neutralizing antibodies and it is therefore an obvious choice for a candidate vaccine. However, full protection might be difficult to achieve with a single subunit vaccine and combining S with the other structural proteins into a multi-subunit vaccine should induce a stronger and more protective immune response. In order to generate an effective vaccine against the SARS virus we have initiated development of a non-replicating VLP-vaccine. To this end using the baculovirus system, initially we expressed each of the structural proteins individually; N, M, E and S proteins. For single gene expression, the genes encoding each individual protein were inserted separately into a transfer vector (pAcYM1) under the control of the polyhedrin promoter, and the expression level and authenticity of each protein were assessed. Subsequently we used our previously generated multi-promoter baculovirus expression vectors to express multi-component viral capsid structures by a single recombinant baculovirus. To prepare this the gene encoding the M protein were inserted into a transfer vector (pAc2Xp10) at the p10 site of the baculovirus genome; and the genes encoding the E and S protein were inserted into another transfer vector (pAcVC3) for the polyhedrin viral gene. The successful recombinant baculoviruses were examined for the expression of the three or four SARS proteins in insect cell culture. Each type of VLP was characterised biochemically, morphologically and immunologically. Using sucrose gradient purification, we found that membrane and envelope proteins are sufficient for the formation of VLP particles and were easily visible by electron microscopy. VLPs with S proteins were also expressed at a high level indicating that such multi-protein particles should induce strong protective antibodies. VLPs lack any genetic materials and thus pose no threat to human health. Although our present studies aim to design a successful SARS vaccine, some reports have demonstrated that VLPs could also represent a useful gene therapy delivery system.