Combined prime-boost vaccination against tick-borne encephalitis (TBE) using a recombinant vaccinia virus and a bacterial plasmid both expressing TBE virus non-structural NS1 protein SE Aleshin1, AV Timofeev1,5, MV Khoretonenko1, LG Zakharova2, GV Pashvykina2, JR Stephenson3, AM Shneider4 and AD Altstein*2

Background: Heterologous prime-boost immunization protocols using different gene expression systems have proven to be successful tools in protecting against various diseases in experimental animal models. The main reason for using this approach is to exploit the ability of expression cassettes to prime or boost the immune system in different ways during vaccination procedures. The purpose of the project was to study the ability of recombinant vaccinia virus (VV) and bacterial plasmid, both carrying the NS1 gene from tick-borne encephalitis (TBE) virus under the control of different promoters, to protect mice against lethal challenge using a heterologous prime-boost vaccination protocol. Results: The heterologous prime-boost vaccination protocol, using a VV recombinant and bacterial plasmid, both containing the NS1 TBE virus protein gene under the control of different promoters, achieved a high level of protection in mice against lethal challenge with a highly pathogenic TBE virus strain. No signs of pronounced TBE infection were detected in the surviving animals. Conclusion: Heterologous prime-boost vaccination protocols using recombinant VV and bacterial plasmids could be used for the development of flavivirus vaccines. Background Prime-boost immunization protocols using different expression systems have proven to be successful tools in protecting experimental animals against various important human diseases [1] including tuberculosis [2], AIDS [3], and hepatitis C [4]. The success of such vaccination schemes depends upon the efficiency of the expression systems, of which, recombinant vaccinia virus(VV) and bacterial plasmid vectors are among the more common systems studied [6-8]. Moreover, it has been shown that when at least one component in a prime-boost vaccination scheme includes a plasmid vector, there is a strong Published: 02 August 2005 BMC Microbiology 2005, 5:45 doi:10.1186/1471-2180-5-45 Received: 22 April 2005 Accepted: 02 August 2005 This article is available from: http://www.biomedcentral.com/1471-2180/5/45 © 2005 Aleshin et al; licensee BioMed Central Ltd. This is an Open Access article distributed under the terms of the Creative Commons Attribution License (http://creativecommons.org/licenses/by/2.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. BMC Microbiology 2005, 5:45 http://www.biomedcentral.com/1471-2180/5/45