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An indirect enzyme-linked immunosorbent assay (ELISA) was developed to quantify tetanus antitoxin activity in guinea pig sera based on a previously calibrated standard. This test is proposed as an alternative to the traditional in vivo neutralization assay used for potency evaluation of tetanus vaccines. The accuracy, precision and linearity of our ELISA were determined. Both methods were used to evaluate 75 guinea pig sera and the results were compared by linear regression analysis. The individual immunological responses against different lots of tetanus vaccine were also studied. The ELISA showed an excellent accuracy, with recovery values between 90-110%; intra, inter and total-assay imprecision ranging around 10% and parallelism deviations below 10%. A high correlation was found between our ELISA and the in vivo neutralization assay (R²= 0,989). The seroprotection levels of the tetanus vaccines tested were over 83%. All those results indicate our ELISA is an excellent alternative procedure for potency testing of tetanus toxoid vaccines. [ABSTRACT FROM AUTHOR]

Potency of pertussis component, present in DPT-vax, is evaluated by Kendrick assay. Strain Bordetella pertussis 18323 is recommended by WHO, which should be stored in a way that ensures its viability, purity and virulence. As part of the assay, the concentration of a strain suspension should be calculated, which opacity is compared at first sight with the Fifth Reference International Preparation of Opacity. This method is very inexact and frequently leads to errors. A seed lot from Bordetella. pertussis 18323 was elaborated and characterized in this study and the concentration of the strain using a calibration curve was calculated. The lot was used in eight potency assays and they complied with established validity criterion. [ABSTRACT FROM AUTHOR]