Ligand-guided-selection method for screening antigen-specific ligands

A Ligand-guided-Selection method for screening ligands that are specific to a predetermined antigen, the method comprising sequential steps of:

• constructing a library of ligands that is at least partially enriched by:
• exposing a target cell line to an aptamer library and permitting at least some aptamers to bind to the target cell line, thereby forming bound aptamers;
• removing aptamers that do not bind to the target cell line;
• eluting the bound aptamers, thereby forming eluted aptamers;
• amplifying the eluted aptamers that are specific to the cell line, thereby forming the library of ligands;
• forming a ligand-cell complex by exposing a culture of target cells to the library of ligands, wherein cells in the culture of target cells each have the predetermined antigen;
• treating the ligand-cell complex with an antibody that is specific to the predetermined antigen, the antibody displacing ligands that are bound to the predetermined antigen to form displace ligands, the step of treating leaving non-displaced ligands bound to the ligand-cell complex;
• eluting the displaced ligands;
• amplifying the displaced ligands using polymerase chain reaction (PCR).

A method for selecting aptamers using an antibody-capped cell Systematic Evolution of Ligands by EXponential enrichment process, the method comprising steps of:

• exposing an antibody-capped cell to a plurality of different aptamers and permitting at least some aptamers to bind to the antibody-capped cell to form bound aptamers, wherein the antibody-capped cell has been pretreated with a predetermined antibody that caps an antigen;
• eluting unbound aptamers;
• and
• amplifying the unbound aptamers.