Immunoaffinity columns in general can be reused so long as there is enough native, free antibody remaining to capture all your analyte. Acidic elution conditions CAN damage the antibody bound to the solid phase, but I think you'll find that antibodies are tough little proteins. What pH do you elute with? I've used IA columns for many (50+) loading and elution cycles with no problem. However, the columns were designed to do just that, in that they have very high antibody loads. If the columns you're using were designed as single use columns they may not have that much antibody on them. I'd recommend trying to re-use one with a non-critical sample. You may want to try washing the column with a very low pH buffer (around pH 1) after your elution, the re-equilibrating it in your loading buffer. While this is pretty harsh (do it quickly), it will ensure that a minimal amount of un-eluted analyte from your previous sample is remaining on the column and occupying binding sites that could be used for the next sample. If you're going to throw the column away anyway it's worth a shot, even if just to satisfy your curiosity.
I have a question as well. How much do the columns you use cost?
