Serological Studies of <i>Haemophilus influenzae</i>

Abstract

Rabbits were immunized with capsulated and non-capsulated H. influenzae bacteria in order to study the antibody response to capsular antigens and·antigens. The response was studied by means of immunodiffusion (ID), direct agglutination (DA), indirect hemagglutination (IHA), and complement fixation (CF) with whole bacteria. The ID analyses showed that anti-O precipitins were generally demonstrable after one week of immunization. Anti-capsular precipitins were demonstrable after two weeks for the hyperimmunized rabbits, but not until one week after the booster dose for the rabbit given a single primary injection. Anti-O agglutinins (DA) were revealed in all rabbits. Maximum levels were revealed early during the immunization and the antibody response for the rabbit given a single dose was as high as for the hyperimmunized rabbits. The titers then generally remained unchanged until the booster dose was given. The boostering did not cause a further titer increase. Anti-capsular agglutinins (DA and IHA) showed considerably lower titers for the rabbit given a single primary injection than for those given repeated injections. The anti-capsular titers decreased during the immunization interval and the booster injections caused a titer increase. For the anti-S sera, the CF test was found to measure the anti-O response, not only when S bacteria but also when M bacteria were used for the test. In addition, cross-reacting anti-O agglutinins and CF antibodies were demonstrated. These anti-O agglutinins, however, could be absorbed without diminishing the homologous anti-O titers. Finally, the suitability of the aforementioned serological method for different purposes is discussed.

Antibodies to nontypeable Haemophilus influenzae in blood donors. A comparison between different assay methods

“…CF was performed as described earlier [2]. In short, test sera were diluted by 1/15, 1/30, 1/60, 1/120 and 1/240.…”

“…Antibodies to nontypeable Haemophilus influenzae are determined by methods such as complement fixation (CF) [1,2], indirect haemagglutination (IHA) [3], or enzyme-linked immunosorbent assay (ELISA) [4]. With diagnostic techniques such as transtracheal aspiration (TTA) [5] it has been demonstrated that nontypeable H. influenzae cause approximately 11% of pneumonias in elderly patients [6], which is a much higher frequency than was thought before.…”