Titrage des anticorps antitétaniques

[Tetanus antitoxin levels in migrants in transit through São Paulo, Brazil]

De 3464 migrantes em trânsito por São Paulo, de dezembro de 1970 a dezembro de 1971, foram obtidas informações sobre dados demográficos e econômico-sociais, tendo sido titulados os níveis de antitoxina tetânica dos soros pela Reação de Hemaglutinação Indireta. Em 25 soros selecionados, com diferentes níveis de antitoxina tetânica pela reação de hemaglutinação indireta, foram dosados os títulos de antitoxina tetânica pela reação de neutralização "in vivo". A correlação entre os títulos dos soros por ambos os métodos, feita pela análise de regressão, mostrou que a reação de hemaglutinação indireta apresenta baixo poder preditivo (47%), mas corresponde a uma técnica adequada nos estudos de inquéritos populacionais, considerando-se sua alta sensibilidade, fácil execução e baixo custo. A ausência de antitoxina circulante em 55,5% do grupo em estudo, associada à pequena proporção de títulos considerados protetores em 1% da população total e em 0,3% da população 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 organização dos serviços de Saúde Pública.

Neutralization of tetanus toxin by distinct monoclonal antibodies binding to multiple epitopes on the toxin molecule

Fifty-seven hybridomas producing antibodies to tetanus toxoid or to the Ibc or B-IIb fragment of the toxin were isolated independently. Competitive inhibition studies demonstrated that monoclonal antibodies from mice immunized with the toxoid bound to at least 20 different epitopes on the toxoid molecule. Similar competitive binding studies revealed eight distinct epitopes on the B-IIb fragment and three to five epitopes on the Ibc fragment of the toxin. Neutralization of toxicity was effected by nine distinct monoclonal antibodies from hybridomas of toxoid-immunized mice and by one monoclonal antibody from B-IIb-immunized mice. Mixtures of two, three, and four different monoclonal antibodies in a variety of combinations exerted a synergistic effect of ca. 200-fold over that observed with individual monoclonal antibodies, indicating that efficient neutralization may involve the simultaneous binding of at least two antibody molecules to different specific regions of the toxin molecule. Only one toxoid-induced monoclonal antibody failed to bind to tetanus toxin. All neutralizing antibodies bound to epitopes on the heavy chain of tetanus toxin. Six of these were directed toward epitopes on the NH2-terminal half, whereas four bound to epitopes on the carboxy-terminal half of the heavy chain. Only one monoclonal antibody bound preferentially to the light chain, but two other monoclonal antibodies appeared to bind to both chains, indicating some homology between these two chains.

A new method for the large scale preparation of antitoxic antibodies exhibiting high specific protective activities

A method using polyethylene-glycol and immobilized pepsin for purifying heterologous antitoxic antibodies is described. Using horse antitetanus plasma or sera, F(ab')2 fragments exhibiting specific activities in the range of 150 IU per mg protein were repeatedly isolated with a yield around 80%. The procedure was scaled up from 200 ml up to 201.

Titration of antibodies to tetanus toxoid by agglutination of purified tetanus toxoid sensitized latex particles

The method of sensitized latex particle agglutination which we have devised allows the selection of samples of plasma for the preparation of immunoglobulins. The population of thus selected samples is the same as is selected by the in vivo test, having a titer greater than or equeal to 6 IU/ml. The test gives a clear-cut difference between the positive and negative results and does not give any prozone phenomenon. It can be used extensively, as the batches of sensitized latex particles may be stored for quite a long time.