Production of antibodies by modification of an autonomous heavy chain variable domain by gene conversion

A transgenic chicken, comprising B cells in which the endogenous immunoglobulin heavy chain locus comprises:

• (a) a functional immunoglobulin heavy chain gene comprising
• (i) a first nucleic acid encoding an autonomous heavy chain (AHC) variable domain, wherein the AHC variable domain is a camelized human heavy chain variable domain that includes at least a Val to Phe substitution at position 37, a Glu at position 44, an Arg at position 45 and a Gly at position 47 (Kabat numbering);
• and
• (ii) a second nucleic acid encoding IgM, IgY and IgA constant regions, wherein the second nucleic acid is endogenous to the chicken, operably linked to the first nucleic acid and not genetically engineered;
• and
• (b) a plurality of pseudogenes that are operably linked to said functional immunoglobulin heavy chain gene and that donate, by gene conversion, nucleotide sequence to the nucleic acid encoding the AHC variable domain of (a), wherein the pseudogenes are upstream or downstream of the functional immunoglobulin heavy chain gene, wherein the pseudogenes encode camelized heavy chain variable domains that include at least a Phe at position 37, a Glu at position 44, an Arg at position 45 and a Gly at position 47 (Kabat numbering);
• wherein:
• (i) the genome of the chicken comprises a light chain immunoglobulin gene that has been knocked out;
• or
• (ii) the genome of the chicken comprises a light chain immunoglobulin gene that encodes a truncated light chain that comprises a constant region but not a variable region;
• and wherein the chicken is immunized with an antigen and produces a diversified population of AHC antibodies that bind to the antigen.