Introduction: Field isolates of bovine leukaemia virus (BLV) show the presence of a few amino acid substitutions in major conformational G and H epitopes on surface glycoprotein gp51. Potentially, these substitutions can affect the 3D structure of these epitopes leading to their diminished immunoreactivity. The aim of this study was to express three gp51 glycoproteins carrying mutated epitopes as recombinant baculovirus proteins in insect cells to test their immunoreactivity with bovine sera. Material and Methods: Env gene chimeras encoding mutated epitopes G and H in the env backbone of BLV FLK strain were constructed, cloned into pFastBac1 vector, and expressed in baculovirus. Results: The presence of recombinant gp51 protein in Sf9 insect cells was confirmed using monoclonal antibodies. ELISA tests were developed to check the immunoreactivity of recombinant protein with bovine sera. Conclusion: Recombinant gp51 proteins with altered G and H epitopes can be used for further studies to analyse the serological response of bovine sera towards BLV antigenic variants.