Codon usage adaptation of lytic viruses to their hosts is determinant for viral fitness. In this work, we analyzed the codon usage of adenoviral proteins by principal component analysis and assessed their codon adaptation to the host. We observed a general clustering of adenoviral proteins according to their function. However, there was a significant variation in the codon preference between the host-interacting fiber protein and the rest of structural late phase proteins, with a non-optimal codon usage of the fiber. To understand the impact of codon bias in the fiber, we optimized the Adenovirus-5 fiber to the codon usage of the hexon structural protein. The optimized fiber displayed increased expression in a non-viral context. However, infection with adenoviruses containing the optimized fiber resulted in decreased expression of the fiber and of wild-type structural proteins. Consequently, this led to a drastic reduction in viral release. The insertion of an exogenous optimized protein as a late gene in the adenovirus with the optimized fiber further interfered with viral fitness. These results highlight the importance of balancing codon usage in viral proteins to adequately exploit cellular resources for efficient infection and open new opportunities to regulate viral fitness for virotherapy and vaccine development.

This work was supported by grants from the Spanish Ministry of Economia y Competitividad BIO2014-57716-C2-2-R and receives partial support from the Generalitat de Catalunya SGR14/248. CIBER de Enfermedades Raras is an initiative of the ISCIII. CF group is partially financed by the Instituto de Salud Carlos III (IIS10/00014) and co-financed by Fondo Europeo de Desarrollo Regional (FEDER). We also acknowledge the support of COST Action BM1204 EUPancreas. E.V. was supported by a fellowship from the Gobierno Vasco, Spain.