Volume :
2
Issue :
4
Abstract :
Enzyme-linked immunosorbent assay (ELISA) and toxin neutralization (TN) test were comparatively evaluated for determination of antibodies to tetanus toxin in sera of immunized guinea pigs and mice at different intervals. Tetanus specific IgG antibodies by ELISA were found in sera of guinea pigs at ninth day after inoculation and in mice sera at seventh day after inoculation when there were no TN antibodies. Two weeks after injection of mice with aluminium phosphate adsorbed tetanus toxoid, anti-tetanus toxin IgG levels determined by ELISA were 35 to 40 times higher than the TN titers. At 4 weeks, ELISA IgG antibody levels of mice and guinea pig sera were still statistically significantly higher than TN titers but with a good correlation between ELISA and TN titers (correlation coefficient of mice sera 0.89). Therefore ELISA results on sera before 6 weeks of immunization determined against a hyper-immune reference serum do not give a true picture of TN levels. The quality control testing of biological especially potency test is a subject on its own. The biological standardizations of each procedure requires meticulous planning and execution. The potency test for tetanus toxoid as specified in Indian pharmacopoeia is biological assay of tetanus antitoxin in immunized guinea pigs. An in vitro serological assay system – ELISA to assess the potency of tetanus toxoid was standardized and results compared with the conventional biological assay.