Virion- and VAP-receptor recognition in the human adenovirus type 2 system

Abstract: This thesis is focused on the early steps of a complex virus-cell interaction. The human adenovirus type 2 (HAdV-2) infects permissive cells, by first recognizing a protein of the immunoglobulin superfamily that serves as the Coxsackie and adenovirus receptor (CAR). This attachment step is mediated by the adenovirus fiber protein. Subsequently, in order to proceed to a tighter binding, the viral penton base interacts with the fibronectin- and vitronectin receptors on the host cell surface. The attached virions are then internalized via receptor-mediated endocytosis, and inside the endosomes the virus penetrates the cell plasma membrane, and once inside the cytoplasm, migrates to the nucleus to start the replicative cycle. We have in this thesis studied in detail the importance of the endosomal acidic environment. We concluded that neither virus attachment, virus penetration, virus uncoating nor HAdV-2 receptor recirculation have a mandatory requirement for endosomal acidification. In order to study more in detail the actual virus attachment, different fragments of the adenovirus attachment protein, also called the fiber were cloned, expressed, purified and subsequently used to perform virus attachment/infection inhibition studies. We found that one of these fragments, the shaft, is also involved in the cell binding process. Finally to study the proteins involved in virus attachment at the cell surface we treated HeLa cells with the gentle detergent octylglucopyranoside in order to remove cell surface components and to further study their possible implication in the complex virus binding process. We have detected, purified and initially characterized one such protein and used it for virus attachment and infection inhibition studies.