Abstract: The present invention relates to fusion proteins comprising a cell surface marker specific VHH. In particular, the invention relates to bispecific VHH adaptor proteins, i.e. fusion proteins comprising an adeno-associated virus (AAV) specific VHH linked to a cell surface marker specific VHH. Moreover, the invention relates to a recombinant AAV which comprises a fusion protein in which a cell surface marker specific VHH is integrated into a capsid protein of the AAV. Also nucleotide sequences encoding such fusion proteins, vectors are contemplated. The invention moreover refers to uses of the fusion proteins and nucleic sequences for gene therapy.