The Bordetella adenylate cyclase toxoid (CyaA) targets cells expressing the alphaMbeta2 integrin receptor CD11b/CD18 (CR3 or Mac-1) and can penetrate into cytosol of professional antigen-presenting cells, such as dendritic cells. This allows us to use CyaA for delivery of passenger antigens into the cytosolic pathway of processing and MHC class I-restricted presentation, which can promote induction of antigen-specific CD8+ cytotoxic T-lymphocyte immune responses. We show here that vaccination with a genetically detoxified CyaA336/E7 protein, carrying the full-length oncoprotein E7 of the human papilloma virus 16 inserted at position 336 of the cell-invasive AC domain of CyaA, induces an E7-specific CD8+ T-cell immune response and confers on mice protective, as well as therapeutic immunity against challenge with TC-1 tumor cells expressing the E7 oncoprotein. The therapeutic efficacy of priming with the CyaA336/E7 vaccine could further be enhanced by a heterologous booster immunization with a highly attenuated modified vaccinia virus Ankara (MVA) expressing the E7 protein fused to the lysosome-associated membrane protein (LAMP1). These results establish the potential of CyaA as a new antigen delivery tool for prime/boost immunotherapy of tumors.

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3-beta-Hydroxysteroid dehydrogenase (3-beta-HSD) activity coded for by the A44L gene of vaccinia virus (VV) was demonstrated in CV-1 cultures infected by all five VV strains tested, viz. WR, Praha virus, DRYVAX Wyeth-derived virus (DD), LIVP and MVA. Deletion of the A44L gene in two Praha virus-derived clones (the moderately virulent P13 and the highly attenuated P20), the WR and DD viruses resulted in absence of 3-beta-HSD activity from infected cultures. The virulence for mice of P13 was not affected, and that of WR was only slightly decreased, by the A44L gene deletion. Recombinant VVs expressing either varicella-zoster virus glycoprotein E (VZV-gE) or hepatitis B virus preS2-S protein (HBV-preS2-S) and their respective A44L deleted mutants were used in immunogenicity tests in mice. In terms of antibody response to VV and the recombinant proteins, the deletion resulted in a lowering the immunogenicity in the moderately virulent clone P13 virus and its progenies. In the highly attenuated P20 and DD viruses and their progenies no effects were apparent.

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