In HIV Antibody detection, which one is better, recombinant antigen or synthetic peptide, why ?

recombinant antigen. because the DNA coding for the antigen is introduced, the antigen will surely be in its native conformation and the antibodies will surely be able to identify it. if you use synthetic peptide, there is a chance that the configuration of the antigen may be altered during the manufacturing process of the peptide, therefore, your antibodies will not notice it and will not be able to elicit an immune response. i'm not really sure about this though, so it's best to get a second opinion. hope this helps you still..! =]