Due to the very efficient nuclear entry mechanism of adenovirus and its low pathogenicity for humans, adenovirus-based vectors have become gene delivery vehicles that are widely used for transduction of different cell types, especially for quiescent, differentiated cells, in basic research, in gene therapy applications, and in vaccine development. As an important basis for their use as gene medicine, adenoviral vectors can be produced in high titers, they can transduce cells in vivo with transgenes of more than 30 kb, and they do not integrate into the host cell genome. Recent advances in the development of adenoviral vectors have brought considerable progress on issues like target cell specificity and tropism modification, long-term expression of the transgene, as well as immunogenicity and toxicity in vivo, and have suggested that the different generations of non-replicative and replicative vectors available today will each suit best for certain applications.

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The organization of the major (L1) and minor (L2) proteins in the human papillomavirus capsid is still largely unknown. In this study we analysed the disulphide bonding between L1 proteins and the association of L2 proteins with capsomers using virus-like particles obtained in insect cells by co-expression of the L1 and L2 genes of human papillomavirus type 33. About 50% of the L1 protein molecules in these particles (1.29 g/cm z) formed disulphide-bonded trimers. Reduction of the intermolecular disulphide bonds by dithiothreitol (DTT) treatment caused disassembly of virus-like particles into capsomers. This indicates that disulphide bonds between capsomers at the threefold symmetry positions of the capsid are essential for the assembly of the papiUomavirus capsid. In contrast, the L2 protein was not engaged in intermolecular disulphide bonding. The L2 protein remained associated with capsomers on disassembly by treatment with DTT. When the disassembly was carried out in 0"65 u-NaC1, complete L2 protein molecules bound preferentially to capsomer oligomers, whereas truncated L2 protein molecules bound only to monomers. In 0.15 u-NaCl only complete L2 protein molecules remained bound to capsomers. This indicates that different regions of the L2 protein molecule are differentially involved in the association of the papillomavirus capsid.Papillomaviruses are a subfamily of the papovaviruses. The properties shared by these viruses include a circular dsDNA genome, a nonenveloped virion and an icosahedral capsid. Papillomaviruses have a specific tropism for epithelial cells and have been found in a great variety of species. More than 70 types of human papillomavirus (HPV) have been recognized but only a few, e.g. HPV-I (which induces cutaneous warts), can be isolated as virus particles. The other HPVs, e.g. HPV-16 or HPV-33 (which are associated with genital carcinoma), have only been identified by cloning their genomes from epithelial lesions. Moreover, no system exists for the efficient propagation of HPVs in vitro.

A panel of six monoclonal antibodies recognizing at least three different antigenic regions has been raised against the L1 major capsid protein of human papillomavirus type 33 (HPV-33), which is associated with cervical carcinoma. The antigenic sites defined by these antibodies have been mapped and classified as typerestricted or broadly cross-reactive using bacterially expressed L1 fusion proteins of a variety of HPV types.Conformational and linear epitopes have been distinguished using native and denatured virus-like particles. HPV infection of genital lesions has been analysed using both monoclonal antibodies and DNA amplification by PCR. The antibodies obtained should be useful to probe the structure of HPV capsids and to develop a general assay for the detection and classification of productive HPV infections.

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