Quantitative estimation of diphtheria and tetanus toxoids. 4. Toxoids as international reference materials defining Lf-units for diphtheria and tetanus toxoids

WHO International Laboratory for Biological Standards, State Serum Institute, Copenhagen S, Denmark.
Biologicals (Impact Factor: 1.21). 02/1990; 18(1):11-7. DOI: 10.1016/1045-1056(90)90063-6
Source: PubMed


The Lf-unit, which is used in the control of diphtheria and tetanus toxoid production and in some countries also to follow immunization of horses for production of antitoxins, has hitherto been defined by means of antitoxin preparations. A diphtheria toxoid and a tetanus toxoid preparation, both freeze-dried, were examined in an international collaborative study for their suitability to serve as reference reagents in the flocculation tests and for defining the Lf-units. It was shown that flocculation tests using the reference toxoids are very reproducible and reliable and the WHO Expert Committee on Biological Standardization established: the toxoid called DIFT as the International Reference Reagent of Diphtheria Toxoid for Flocculation Test with a defined content of 900 Lf-units of diphtheria toxoid per ampoule; and the toxoid called TEFT as the International Reference Reagent of Tetanus Toxoid for Flocculation Test with a defined content of 1000 Lf-units of diphtheria toxoid per ampoule.

64 Reads
  • Source
    • "TEFT was assigned a value of 1000 Lf/ampoule in WHO BS/07.2061 P a g e | 10 the previous collaborative study [5] where a geometric mean value of 1000 Lf/ampoule (95% confidence limits: 963-1039; GCV 6.5%; n=13) was reported for Ramon test [4] using a different antitoxin. The results obtained in this study are in agreement with those reported previously. "

  • [Show abstract] [Hide abstract]
    ABSTRACT: Diphtheria toxoid, which is an important vaccine in the expanded program of immunization (EPI) in the developing countries, was microencapsulated using poly(D,L,-lactide) of 49,000 molecular weight and the in-water drying technique. The microcapsules were subjected to an in vitro antigen release study using a sensitive enzyme-linked immunosorbent assay (ELISA) developed in the laboratory. Antibody titers in immunized Balb/C mice were also determined using direct ELISA. The antibody units in the immunized group till day 75 were quite comparable to those in the group receiving conventional three-dose injection of diphtheria toxoid with calcium phosphate as an adjuvant. SEM photographs of the microcapsules during in vitro degradation demonstrated the erosion kinetics of the polymer, leading to controlled release of the antigen.
    Pharmaceutical Research 08/1991; 8(7):958-61. DOI:10.1023/A:1015832302605 · 3.42 Impact Factor
  • [Show abstract] [Hide abstract]
    ABSTRACT: Two freeze-dried international reference diphtheria toxoids of different origin were compared in biological assays in guinea-pigs and mice under different adjuvant conditions. When the antigenic content in the two toxoids was used as denominator for determination of relative potency, that is to say quantitation of immunogenic power per unit amount of antigen, the design of the animal assay proved to have a major influence. Similar observations have been made previously also for tetanus vaccines. It is concluded that diphtheria vaccines as well as tetanus vaccines can hardly be quantitated unambiguously using the currently recommended potency assays in animals. A new scheme for control of toxoid vaccine production is suggested, with more emphasis on the control of the bulk purified toxoid, which would make the release of final products more simple and rapid.
    Biologicals 11/1991; 19(4):327-34. DOI:10.1016/S1045-1056(05)80022-3 · 1.21 Impact Factor
Show more

Preview (2 Sources)

64 Reads
Available from