Abstract: An expression library comprising a repertoire of nucleic acid sequences cloned from a non-immunised source, each nucleic acid sequence encoding at least part of a variable domain of a heavy chain derived from an immunoglobulin naturally devoid of light chains (VHH) wherein the extent of sequence variability in the library is enhanced compared to the corresponding naïve expression library by introducing mutations in one or more of the complementarity determining regions (CDRs) of the nucleic acid sequences or by generating alternative combinations of CDR and framework sequences not naturally present in the naïve library repertoire. Also disclosed is the use of such a library in preparing antibodies, more particularly antibody fragments.

Abstract: A multivalent antigen binding protein comprises a single polypeptide chain comprising, in series, two or more single domain binding units which are preferably heavy chain variable domains derived from an immunoglobulin naturally devoid of light chains. Methods for their production and uses thereof, in particular for diagnosis, immunoassay and purification methods are disclosed.

Abstract: An expression library comprising a repertoire of nucleic acid sequences cloned from a non-immunized source, each nucleic acid sequence encoding at least part of a variable domain of a heavy chain derived from an immunoglobulin naturally devoid of light chains (VHH) wherein the extent of sequence variability in said library is enhanced compared to the corresponding naive expression library by introducing mutations in one or more of the complementarity determining regions (CDRs) of said nucleic acid sequences or by generating alternative combinations of CDR and framework sequences not naturally present in the naive library repertoire. Also disclosed is the use of such a library in preparing antibodies, more particularly antibody fragments.

Abstract: An expression library comprising a repertoire of nucleic acid sequences cloned from a non-immunized source, each nucleic acid sequence encoding at least part of a variable domain of a heavy chain derived from an immunoglobulin naturally devoid of light chains (VHH) wherein the extent of sequence variability in the library is enhanced compared to the corresponding naive expression library by introducing mutations in one or more of the complementarity determining regions (CDRs) of the nucleic acid sequences or by generating alternative combinations of CDR and framework sequences not naturally present in the naive library repertoire. Also disclosed is the use of such a library in preparing antibodies, more particularly antibody fragments.