Compositions, methods and uses of a recombinant virus and/or recombinant viral vector encoding a distinct antibody or antibody fragment generated from high-diversity nucleic acid library are presented. Preferably, the recombinant virus is genetically modified, low immunogenic virus, for example, an E2b-deleted adenovirus. The high-diversity nucleic acid library comprises or is derived from (1) a VH-CDR1/2 sub-library, (2) a plurality of VH-CDR3 sub-libraries, and (3) a VL sub-library, each of which comprises a plurality of members. Preferably, each member of the sub-libraries comprises at least one random cassette that has a plurality of degenerate base positions. In an especially preferred embodiment, at least portions of at least two members of the VH-CDR1/2 sub-library, the plurality of VH-CDR3 sub-libraries, and the VL sub-library are recombined to form an expression library member in an expression library, where each member of the expression library encodes a distinct antibody or antibody fragment.