Polyclonal antibody libraries

A method of producing a polypeptide library having affinity for a target, comprising:

• a) providing a library of recombinant particles, wherein a member comprises a recombinant particle capable of displaying from its surface a fusion protein comprising a particle coat protein and a displayed polypeptide, the fusion protein encoded by a genome of the recombinant particle and the polypeptides varying between members, and wherein the library of recombinant particles has been selected by adsorbing the library of recombinant particles against a target;
• b) transferring a mixture of DNA molecules encoding at least ten different polypeptides from the library of recombinant particles into multiple copies of an expression vector to produce modified forms of the expression vector by insertion of one of the DNA molecules;
• and
• c) introducing the modified forms of the expression vector into a host and expressing the polypeptides in the host, generating a library of at least ten different polypeptides of which a majority have specific affinity for the same target molecule and no polypeptide is significantly over represented.

A method of producing a polypeptide library having affinity for a target, comprising:

• a) providing a library of viral particles from viral vectors, wherein an individual member comprises a viral particle capable of displaying on its surface a fusion protein comprising a viral coat protein and a displayed polypeptide, the fusion protein being encoded by a nucleic acid segment of the viral vector, and the polypeptides varying between members of the library, and wherein the library of viral particles has been selected by adsorbing the library of viral particles against a target;
• b) transferring a mixture of DNA molecules encoding at least ten different polypeptides from the library of viral vectors into multiple copies of an expression vector to produce modified forms of the expression vector by insertion of one of the DNA molecules;
• and
• c) introducing the modified forms of the expression vector into a host and expressing the polypeptides in the host, generating a library of at least ten different polypeptides of which a majority have specific affinity for the same target and no polypeptide is significantly overrepresented.

A method of producing an antibody or antibody fragment library having affinity for a target, comprising:

• a) providing a library of phage particles, wherein a member of the library comprises a phage particle capable of displaying from its surface an antibody or antibody fragment comprising an antibody heavy chain variable domain complexed with an antibody light chain variable domain, wherein either the heavy or light chain variable domain is expressed as a fusion protein with a coat protein of the phage particle and both the heavy and light chain variable domain are encoded by the genome of the phage, and the heavy and/or light chain varies between members;
• b) transferring a mixture of DNA molecules encoding the heavy and light chain variable domains from the phage display library members into multiple copies of an expression vector to produce modified forms of the expression vector by insertion of one of the DNA molecules;
• and
• c) introducing the modified forms of the expression vector into a host and expressing antibodies or antibody fragments formed by the heavy and light chain variable domains of the phage display library in the host, the antibodies or antibody fragments being released from the host to form an antibody library of at least ten different antibodies of which a majority have specific affinity for the same target molecule and no antibody or antibody fragment is significantly overrepresented.

A method for producing a polypeptide library having affinity for a target, comprising:

• a) providing a library of first expression vectors encoding polypeptides that vary between members and which facilitate screening and selection of polypeptides with the desired target-specificity;
• b) generating a sub-library of first expression vectors encoding polypeptides that vary between members and where a majority possess the desired target-specificity comprising selecting said library of first expression vectors against a target;
• c) transferring polypeptide encoding DNA fragments from said sub-library to multiple copies of a second expression vector providing a library of second expression vectors with at least 10 different fragments;
• and
• d) introducing said second library of expression vectors into a host and expressing said different polypeptides from said host.

A method of obtaining a library of polyclonal receptor proteins or fragments thereof comprising the steps of:

• a) providing a first library of vectors, wherein an individual vector contains a nucleic acid segment that encodes a pair of variable regions constituted in the binding domain of an individual receptor protein of the library, and wherein the totality of nucleic acid segments in said library of vectors is diverse forming a library of polyclonal nucleic acid segments containing at least 10 different segments;
• b) transferring said polyclonal nucleic acid segments in mass into an expression vector, forming a second library of expression vectors wherein the diversity of polyclonal nucleic acid segments is reduced by less than 10%;
• and
• c) introducing said library of expression vectors into host cells and expressing said library of polyclonal receptor proteins from said host cells.

A method of obtaining a library of polyclonal receptor proteins or fragments thereof, with a desired specificity, comprising the steps of:

• a) providing a library of selected vectors, wherein an individual vector contains a nucleic acid segment that encodes a pair of variable regions constituted in the binding domain of an individual receptor protein of the library, where the binding domain of said receptor protein possess a desired specificity, and wherein the totality of nucleic acid segments in said library of selected vectors is diverse forming a library of polyclonal nucleic acid segments containing at least 10 different segments;
• b) transferring said polyclonal nucleic acid segments in mass into an expression vector, forming a library of expression vectors wherein the diversity of polyclonal nucleic acid segments is reduced by less than 10%;
• and
• c) introducing said library of expression vectors into host cells and expressing said library of polyclonal receptor proteins from said host cells.