Specific antibody immune response against the parasitic portion of a glutathione-S-transferase fusion protein.

The humoral immune response against an Entamoeba histolytica recombinant protein has been investigated. The 628 bp Bam HI-Eco RI DNA fragment (L1b) from the M11 cDNA clone, partially coding for a 220 kDa (L220) protein, was ligated in-frame into the pGEX-3X plasmid vector to produce the fusion protein GST-L1b. BALB/c mice were immunized with different doses of the GST-L1b fusion protein (10-500 microg). GST-L1b doses of 100/50/50, 300, or 500 microg induced an antibody response (IgG1>IgG3, IgG2a>IgG2b) specific for the amoebic part of the fusion protein (L1b). These antibodies were able to recognize the native protein in amoebic total extract. Anti-GST antibodies were not detected. On the other hand, doses of 10/10/10 or 200/100/100 microg induced antibodies able to recognize both GST (IgG2a>IgG1>IgG2b) and L1b (IgG1, IgG2a>IgG3>IgG2b). When mice were immunized with GST alone (100/50/50, 300 or 500 microg), antibodies against GST-L1b or GST were not detected. However, GST doses of 10/10/10 or 200/100/100 microg induced an antibody response able to recognize both GST-L1b and GST. We propose that an immunization protocol similar to the one used in this work may allow induction of high antibody titers specific against the parasite segment of a GST-fusion protein.