Durability of immunity to diphtheria, tetanus and poliomyelitis after a three dose immunization schedule completed in the first eight months of life.

Blood samples were obtained from school entrants whose primary immunization schedule had consisted of three doses of DT or DTP vaccine and three doses of OPV all given before the age of 8 months. The sera were separated and assayed for diphtheria antitoxin, tetanus antitoxin and antibodies to the three serotypes of poliovirus. The results of the assays showed that the abbreviated three dose schedule induced satisfactory immunity to all five infections until school entry and that a reinforcing dose at 18 months was unnecessary.

Estimation of Corynebacterium diphtheriae antitoxin in human sera: a comparison of an enzyme-linked immunosorbent assay with the toxin neutralisation test.

Serum samples from 101 individuals were titrated for Corynebacterium diphtheriae antitoxin by an IgG-specific enzyme-linked immunosorbent assay (ELISA) and a neutralisation test in tissue culture (TC). In some of the sera, the concentrations of antitoxin determined by the two assays were different; antitoxin values in these sera were titrated again by neutralisation tests in guinea pigs (GNT). Antitoxin concentrations of greater than 0.01 IU/ml by GNT partly corresponded to values obtained in both ELISA and TC. Only the values from TC agreed with lower GNT results. Heat inactivation of sera was investigated and rejected as a possible reason for the discrepancy in the results. ELISA can be used to detect levels of less than 0.1 IU/ml, although the accuracy below 0.01 IU/ml, often considered a protective level, is questionable. At higher levels ELISA was reproducible for the titration of diphtheria antitoxin in human sera and offers a useful alternative to both in-vivo assays and TC.

The activity of purified Bordetella pertussis components in murine encephalopathy.

A murine encephalopathic syndrome can be induced by the administration of BSA and whole-cell pertussis vaccine. The present paper reports studies of the capacity of purified individual pertussis components to induce this effect. Pertussis toxin and endotoxin together with a highly immunogenic sensitizer protein were required to induce the effect. The strength of the antibody response to the sensitizer appeared to be more important than the H-2 type of the recipient in determining the susceptibility of different mouse strains. The relevance of this syndrome to the study of possible vaccine-induced encephalopathy in man is uncertain and requires further investigation.

Diphtheria vaccine for adults.

A low dose (1.5 Lf) diphtheria vaccine for use in adults was given to 310 university student volunteers whose diphtheria antitoxin titres were less than 0.1 IU per ml. The incidence of adverse reactions was low. Postimmunisation blood samples taken from 134 of the students showed that in susceptible vaccinees the vaccine induced titres of antitoxin were consistent with protection and that it boosted the titres of those whose immunity was low.

Single radial immunodiffusion as a method for the identification and quantitation of diphtheria and tetanus toxoids in adsorbed vaccines.

The immunochemical techniques of double diffusion and single radial diffusion in agarose gels were compared and each considered as possible alternative methods to the methods stipulated by the European Pharmacopoeia for the identification of diphtheria and tetanus toxoids in adsorbed vaccines. Both methods identified the toxoids but single radial diffusion was found to be preferable as the precipitin bands formed were visible without staining. Single radial diffusion was further investigated for its suitability as a quantitative method and was found to give reproducible estimates of the amount of toxoid present in all vaccines tested. However, in the case of tetanus toxoids these estimates were lower than the amounts stated to have been incorporated in the vaccines by the manufacturers. It was concluded that single radial diffusion would be a suitable replacement in the European Pharmacopoeia as a method for the identification of the diphtheria and tetanus components of adsorbed vaccines provided that elution could also be achieved from vaccines containing calcium phosphate.

A comparison of enzyme-linked immunosorbent assay (ELISA) with the toxin neutralization test in mice as a method for the estimation of tetanus antitoxin in human sera.

An enzyme-linked immunosorbent assay (ELISA) has been developed for the measurement of tetanus antitoxin in human sera as an alternative to the toxin neutralization test in mice, the currently accepted method of assay. The ELISA was found to be simple and quick to perform and required only small amounts of materials. In addition, the assay was found to give reproducible estimates of antitoxin levels and to measure antitoxin at levels as low as 0.01 IU per ml, a sensitivity similar to that of the neutralization test. Furthermore, a comparison of the results of the ELISA and the neutralization test involving 80 human sera, including sera with both high and low antitoxin levels, showed close agreement in antitoxin levels obtained by the two methods. It was concluded that ELISA was an acceptable alternative to the toxin neutralization test in mice for the measurement of tetanus antitoxin levels in human sera.