Hi Scientists,

I am looking to purify HIV neutralizing antibodies from human plasma using a protein A spin column kit (cosmo bio). The kit can only purify up to 0.4 mg of IgG. Other relevant information such as the binding and elution pH is not provided by the manufacturer.

To avoid overloading my column, I use 100 uL of plasma for IgG purification. However, the neutralizing ability of the subsequent IgG is very low relative to that of unfractionated plasma. I have checked the plasma flowthrough for any neutralization activity but there's none. I have also tried dialysis against PBS to no avail. So far I have been stuck at this stage for almost 4 weeks now.

I was wondering if the problem could be the binding capacity of the kit. Do you think a binding capacity of 0.4 mg is too low to elute a meaningful titer of my antibody of interest?

Have you experienced a similar problem with the kit (or another manufacturer's kit)? How did you go about?

Best Regards.