Detection of toxoplasma IgM antibodies by ELISA method: a comparative study of different enzymes as markers.

Detection of toxoplasma IgM antibodies by employing enzyme linked immunosorbent assay (ELISA) technique was developed using different enzymes viz, horseradish peroxidase (HRP) (EC. 1.11.17), urease (EC. 3.5.15) and penicillinase (EC 3.5.2.6) as markers. Of these enzymes, HRP is light sensitive and needs dark chamber, also inactivated by preservative sodium azide. Similarly urease test system is extremely pH sensitive and demands special care during ELISA technique. Whereas penicillinase showed certain distinct advantages viz. stable at room temperature, high specific activity and economical. In the present studies it was observed that the sensitivity of penicillinase is similar to HRP and urease, marker enzymes used in commercially available diagnostic kit. The prominent feature of detection of toxoplasma IgM antibodies involving these three enzymes are: a) Shorter incubation time (About 2.5 hours) b) No false positive reaction. Moreover, these enzyme conjugates were prepared from F (ab')2 fragments of antitoxoplasma rabbit serum to elicit specific interaction with IgM antibodies only, avoiding cross interaction with other non-specific proteins like compliment systems and rheumatoid factor.