Problem purifying GST-fusion expressed in Baculovirus - (Jun/25/2008 )

I am trying to purify recombinant GST-fusion proteins for antibody elution from human plasma and rabbit immunization. I have cloned my genes into pAcG2T Baculovirus Expression Vector. I was able to purify ONLY a small amount (very low conc.) of one of my GST-fusions (recognized by anti-GST antibody but not seen by coomassie stain) using Glutathione Sepharose 4B, but for the rest of proteins no band was seen, instead I saw good bands in the collected flow through (before elution) for some of them! The Gluta Sepha 4B I used expires in 2009 and had been stored in at 4oC. Does anyone know what could be causing this? Anyone with a better protocol on purifying GST-fusion protein expressed in Baculovirus system?

I’ll sincerely appreciate your help.