Johan Skog

Adenoviruses Use Lactoferrin as a Bridge for CAR-Independent Binding to and Infection of Epithelial Cells

ABSTRACT Most adenoviruses bind to the coxsackie- and adenovirus receptor (CAR). Surprisingly, CAR is not expressed apically on polarized cells and is thus not easily available to viruses. Consequently, alternative mechanisms for entry of coxsackievirus and adenovirus into cells have been suggested. We have found that tear fluid promotes adenovirus infection, and we have identified human lactoferrin (HLf) as the tear fluid component responsible for this effect. HLf alone was found to promote binding of adenovirus to epithelial cells in a dose-dependent manner and also infection of epithelial cells by adenovirus. HLf was also found to promote gene delivery from an adenovirus-based vector. The mechanism takes place at the binding stage and functions independently of CAR. Thus, we have identified a novel binding mechanism whereby adenovirus hijacks HLf, a component of the innate immune system, and uses it as a bridge for attachment to host cells.

Human adenovirus serotypes 4p and 11p are efficiently expressed in cell lines of neural tumour origin.

Most currently used adenovirus vectors are based upon adenovirus serotypes 2 and 5 (Ad2 and Ad5), which have limited efficiencies for gene transfer to human neural cells. Both serotypes bind to the known adenovirus receptor, CAR (coxsackievirus and adenovirus receptor), and have restricted cell tropism. The purpose of this study was to find vector candidates that are superior to Ad5 in infecting human neural tumours. Using flow cytometry, the vector candidates Ad4p, Ad11p and Ad17p were compared to the commonly used adenovirus vector Ad5v for their binding capacity to neural cell lines derived from glioblastoma, medulloblastoma and neuroblastoma cell lines. The production of viral structural proteins and the CAR-binding properties of the different serotypes were also assessed in these cells. Computer-based models of the fibre knobs of Ad4p and Ad17 were created based upon the crystallized fibre knob structure of adenoviruses and analysed for putative receptor-interacting regions that differed from the fibre knob of Ad5. The non CAR-binding vector candidate Ad11p showed clearly the best binding capacity to all of the neural cell lines, binding more than 90% of cells of all of the neural cell lines tested, in contrast to 20% or less for the commonly used vector Ad5v. Ad4p and Ad11p were also internalized and produced viral proteins more successfully than Ad5. Ad4p showed a low binding ability but a very efficient capacity for infection in cell culture. Ad17p virions neither bound or efficiently infected any of the neural cell lines studied.

Glioma-specific antigens for immune tumor therapy.

This review describes glioma-specific antigens important in immunotherapy of glioma tumors. The structure and function of these antigens and recent immunotherapy data are summarized. Also, some important aspects of tumor formation are outlined. The roles of neuronal precursor cells and tumor stroma cells are discussed. The stroma cells of the tumor may be of interest as a target for tumor therapy, especially since they are less heterogeneous than the tumor cells. To date, the clinical benefit of immunotherapy has been very limited. Immunotherapy is, however, still an extremely promising approach to tumor therapy and it will most likely be implemented as a future treatment option for many types of tumors. The current shortcomings of immunotherapy will probably diminish as we start to understand and are able to modulate tumor-induced immunosuppression. There is also a need for a continued search for new tumor-specific antigens and to optimize protocols for vaccine administration.