Adenovirus retargeting to surface expressed antigens on oral mucosa

Head and neck squamous cell carcinomas develop in preneoplastic mucosal fields that can extend over several centimeters in diameter. Most of these fields are microscopically recognized as dysplasias. These fields are often not adequately treated and might cause local relapse. Previous investigations demonstrated that mouthwash therapy with oncolytic adenoviruses appears to be a good option for the treatment of these fields, although, at present, with limited efficacy.

Immunohistochemistry on normal and preneoplastic mucosa was applied to determine the expression levels of the coxsackie adenoviral receptor (CAR) and a few surface antigens that might allow retargeting: Ly-6D, CD44v6 and K928. Monoclonal antibodies directed against these surface antigens were used for retargeting of adenoviruses in model experiments with organotypic cultures of mucosal epithelium. A bispecific single chain antibody was constructed against both the adenoviral knob and Ly-6D.

Immunohistochemical staining revealed that CAR is present only at a low level in the basal layers of the oral mucosa of both normal and dysplastic lesions. By contrast, Ly-6D, CD44v6 and K928 were abundantly expressed and Ly-6D even on the most superficial layers. Monoclonal antibodies against Ly-6D and CD44v6 were shown to enhance infection in an organotypic cell culture by one log. Based on these observations, we constructed a bispecific single chain antibody against Ly-6D and adenovirus fiber knob, and showed that this engineered molecule allows efficient CAR-independent infection.

Retargeting of oncolytic adenovirus to other surface molecules might improve the efficacy of virotherapy of preneoplastic fields in the oral mucosa.