Determination of low tetanus or diphtheria antitoxin titers in sera by a toxin neutralization assay and a modified toxin-binding inhibition test

A method for the screening of tetanus and diphtheria antibodies in serum using anatoxin (inactivated toxin) instead of toxin was developed as an alternative to the in vivo toxin neutralization assay based on the toxin-binding inhibition test (TOBI test). In this study, the serum titers (values between 1.0 and 19.5 IU) measured by a modified TOBI test (Modi-TOBI test) and toxin neutralization assays were correlated (P < 0.0001). Titers of tetanus or diphtheria antibodies were evaluated in serum samples from guinea pigs immunized with tetanus toxoid, diphtheria-tetanus or triple vaccine. For the Modi-TOBI test, after blocking the microtiter plates, standard tetanus or diphtheria antitoxin and different concentrations of guinea pig sera were incubated with the respective anatoxin. Twelve hours later, these samples were transferred to a plate previously coated with tetanus or diphtheria antitoxin to bind the remaining anatoxin. The anatoxin was then detected using a peroxidase-labeled tetanus or diphtheria antitoxin. Serum titers were calculated using a linear regression plot of the results for the corresponding standard antitoxin. For the toxin neutralization assay, L+/10/50 doses of either toxin combined with different concentrations of serum samples were inoculated into mice for anti-tetanus detection, or in guinea pigs for anti-diphtheria detection. Both assays were suitable for determining wide ranges of antitoxin levels. The linear regression plots showed high correlation coefficients for tetanus (r² = 0.95, P < 0.0001) and for diphtheria (r² = 0.93, P < 0.0001) between the in vitro and the in vivo assays. The standardized method is appropriate for evaluating titers of neutralizing antibodies, thus permitting the in vitro control of serum antitoxin levels.

Determination du niveau d'anticorps antitetaniques en denneurs de sang au moyen du test ELISA-tétanos (Säo Paulo, SP, Brésil) / Determination of tetanus antibodies levels in blood donors by ELISA-tetanos test (Säo Paulo, SP, Brazil)

O teste ELISA-TETANOS (Biosys, France) foi utilizado para a titulaçäo de antitoxina tetânica (sensibilidade = 0,0025UI/ml) em soros humanos de doadres de sangue, 566 homens e 108 mulheres, idade entre 18 e 58 anos, média de 29 anos, residentes em Säo Paulo, Brasil. A Organizaçäo Mundial de Saúde aceita apenas o teste de soroneutralizaçäo em animais, método de referência, para os estudos de proteçäo cdontra o tétano, e preconisa o titutlo mínimo protetor de 0,01 UI/ml.BOURLEAUD & HUET, propuseram o limite de 0,06 UI/ml quando se emprega o teste imunoenxzimático ELISA, devido a discrepâncias inevitáveis entre os dois métodos. Dos 674 soros estudados, 178 (26,41%) näo apresentaram anticorpos detectáveis (<0,0025) UI/ml); 413 (61,28%) apresentaram resultados iguais ou superiores a 0,06UI/ml. A porcentagem proporcional à idade: cerca de 50% do grupo mais jovem (homens de 18 a 23 anos) contra 10% do grupo de mais de 42 anos apresentarom títulos seguramente protetores (> ou = 0,06UI/ml)

Effect of priming with carrier on response to conjugate vaccine.

To examine whether prior immunity against a carrier protein modulates the serological response to injected peptide haptens attached to the same carrier in man, baseline tetanus antitoxin levels in volunteers who received a malaria sporozoite peptide-tetanus toxoid conjugate vaccine were compared with post-vaccination IgM and IgG antibody titres against the sporozoite antigen. In tetanus-vaccinated North American recipients of low doses of conjugate vaccine there were significant dose-dependent negative correlations between these variables, which suggests that epitopic suppression may occur in man. In contrast, Venezuelans living in non-malarious areas and mostly naive to tetanus toxoid showed a notable IgM response to the sporozoite antigen. The findings indicate that epitopic suppression and immune enhancement occur in man, and that the specific immunological responses to conjugate peptide vaccines may be difficult to predict.

Níveis de antitoxina tetânica em migrantes internos em Säo Paulo, Brasil / Tetanus antitoxin levels in internal migrants in Säo Paulo, Brazil

De 3464 migrantes em trânsito por Säo Paulo, de dezembro de 1970 a dezembro de 1971, foram obtidas informaçöes sobre dados demográficos e econômico-sociais, tendo sido titulados os níveis de antitoxina tetânica dos soros pela Reaçäo de Hemaglutinaçäo Indireta. Em 25 soros selecionados, com diferentes níveis de antitoxina tetânica pela reaçäo de hemaglutinaçäo indireta, foram dosados os títulos de antitoxina tetânica pela reaçäo de neutralizaçäo "in vivo". A correlaçäo entre os títulos dos soros por ambos os métodos, feita pela análise de regressäo, mostrou que a reaçäo de hamaglutinaçäo indireta apresenta baixo poder preditivo (47%), mas corresponde a uma técnica adequada nos estudos de inquéritos populacionais, considerando-se sua alta sensibilidade, fácil execuçäo e baixo custo. A ausência de antitoxina circulante em 55,5% do grupo em estudo, associada à pequena proporçäo de títulos considerados protetores em 1% da populaçäo total e em 0,3% da populaçäo de mulheres de 15 a 44 anos - "grupo de risco especial" - explicam os altos índices de morbidade e mortalidade devidos ao tétano em nosso meio, revelando a precariedade da organizaçäo dos serviços de Saúde Pública

Tetanus antitoxin titers in women of childbearing age from nine diverse populations.

The proportion of women with tetanus antitoxin titers adequate to provide protection for themselves and for their newborn infants varied from 96% in New Haven, Connecticut to 19% in Santiago, Chile. Women of childbearing age in five of the nine areas (São Paulo, Recife, and Pôrto Alegre, Brazil; Ecuador; and Gazankulu, South Africa) had an average of 40% immunity to tetanus and did not differ significantly from one another. By comparison with Chile, where vaccination during pregnancy is not current policy, we estimate that 21%-34% of the women in these five areas had received toxoid recently. In general about half the women with inadequate titer had undetectable levels of antibody and may require more than one dose of vaccine to attain immunity.

Current status of passive immunity to diphtheria and tetanus in the newborn.

The extent of transplacentally derived immunity to the toxins of Corynebacterium diphtheriae and Clostridium tetani was assessed by a hemagglutination technique using the cord sera of a group of infants recently born in Bronx, New York. Protective levels of antitoxin to C. diphtheriae were found in 64% of the infants. Tetanus antitoxin was present in sufficient quantity for protection in 38% of the cord sera. While this degree of immunity reepresents an improvement over that achieved 20 years ago and probably reflects the effects of immunization procedures, further attention to the maintenance of immunizations in women of childbearing age would improve these statistics.