The present invention relates to an Adeno-associated virus (AAV) library comprising a multitude of Adeno-associated virus (AAV) variants, wherein the viral particles of each AAV variant comprise a specific combination of (i) a strain-specific capsid polypeptide and (ii) a peptide inserted into said capsid polypeptide, and wherein said strain-specific capsid polypeptides are derived from at least two different AAV strains. The present invention further relates to a method for identifying an AAV variant infecting a target cell of interest comprising a)providing a library of AAV variants comprising each AAV variant in an isolated manner, wherein each AAV variant of said library of AAV variants comprises a specific combination of (i) a strain-specific capsid polypeptide and (ii) a peptide inserted into said capsid polypeptide and wherein said strain-specific capsid polypeptides are derived from at least two different AAV strains； b)contacting each of said AAV variants individually with said target cell of interest； c) determining AAV infection of said target cells of interest； and d) based on the result of step c), identifying a variant AAV infecting a target cell of interest； and to a library of polynucleotides,a library of cloning cells, and to uses related thereto.
