Abstract: A method of generating and isolating a recombinant high affinity anti-sialic acid antibody molecule comprises the steps of immunising a host with an immunogen comprising a conjugate of sialic acid and a carrier protein to generate an anti-sialic acid polyclonal serum, isolating a sample of RNA from the immunised avian host, and generating and screening of a library of recombinant antibody molecules from the RNA sample, and isolating a recombinant high affinity anti-sialic acid antibody molecule. The antibody molecule is selected from the group consisting of: whole antibodies; scFv fragments; and Fab fragments, and the host is Gallus domesticus. A recombinant avian antibody fragment having high binding affinity to sialic acid and obtainable by the method of the invention, and an anti-sialic acid polyclonal serum obtainable by immunising an avian host with a conjugate of sialic acid and carrier protein, are also described.