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.     

Combined estimation of tetanus and diphtheria antitoxin in human sera by the in vitro Toxin-Binding Inhibition (ToBI) test

The use of the principle of inhibition of toxin binding to an antitoxin coated immunoassay plate as described in a previous paper for tetanus antitoxin titration, was adapted for the estimation of diphtheria antitoxin in human sera. With a few modifications, a Toxin-Binding Inhibition (ToBI) test was developed which could be used for a combined estimation of both tetanus and diphtheria antitoxin levels. The application of streptavidin-biotinylated peroxidase complex when using small serum samples (less than 50 microliters) is discussed. Antitoxin titres (both diphtheria and tetanus) of 0.002 IU ml-1 were detectable by the ToBI test, this being far below the level considered to be protective in man. Sera from 140 adults with different vaccination histories were titrated for both tetanus and diphtheria antitoxin. Good correlations were found between the estimates obtained by the ToBI test and those obtained by the toxin-neutralization (TN) test in mice (tetanus antitoxin) and those obtained in the in vitro neutralization test in VERO cells (diphtheria antitoxin). It is concluded that the ToBI test is a simple and reliable alternative to the functional models currently in use for the estimation of diphtheria and tetanus antitoxin levels. In addition, the ToBI test eliminates the need for laboratory-animal or cell-culture facilities and can be performed with small quantities of serum as required in field trials.     

Titration of tetanus antitoxin by passive hemagglutination. I. Titration of guinea-pig antitoxins at various periods of immunization.

An improved technique for passive hemagglutination (HA) for titration of tetanus antitoxin was described. The use of highly purified tetanus toxoid and of improved diluent increased the specificity and reproducibility of the test. Several hundreds of specimens of guinea-pig serum taken at various stages of immunization were titrated by HA and toxin neutralization (NT) in mice. The ratio of HA to NT titers varied significantly depending on the immunization stage; higher at early stages and lower at later stages. The high HA/NT ratio was not due to the IgM antitoxin, which is very rare in guinea pigs. The variation in discrepancy between HA and NT titers decreased considerably by grouping the serum specimens with respect to the stage of immunization. Thus, it is possible to predict the in vivo titer of a tetanus antitoxin accurately enough for clinical study. The HA test may be useful as an alternative method for titrating tetanus antitoxin in the field trials. Moreover, it can be used for the study of characteristics of antitoxins.     

Quantitation of commercial equine tetanus antitoxin by competitive enzyme-linked immunosorbent assay

In the USA, the potency of commercially prepared equine tetanus antitoxin is determined by the method outlined in the Code of Federal Regulations, Title 9, Part 113.451. In the current test, commercial equine tetanus antitoxin is tested by a toxin neutralization test in guinea pigs. The in vivo test measures antitoxin content through effectiveness of protection of guinea pigs injected with diluted mixtures of antitoxin and a standard toxin. A competitive enzyme-linked immunosorbent assay, designed as an in vitro alternative to the in vivo test, measures antitoxin content based on a competitive reaction between standard or unknown serum and murine monoclonal antibody specific for tetanus toxin. The monoclonal antibody used in the assay delayed death in mouse passive protection studies and reacted with the C fragment of tetanus toxin. No cross-reaction was observed when the antibody was tested with the toxins of Clostridium chauvoei, C. novyi, C. perfringens, or C. sordellii. The in vitro test will measure the antitoxin content of serum samples containing 100-1500 units of antitoxin. Tetanus antitoxin titers obtained by the competitive enzyme-linked immunosorbent assay compared favorably with the toxin neutralization test conducted in guinea pigs. The in vitro assay serves as a feasible alternative to the in vivo test because it can be completed in less time, is reproducible, and eliminates the use of test animals.     

The titration of tetanus antitoxin III. A comparative evaluation of indirect haemagglutination and toxin neutralization titres of human sera

The tetanus antitoxin titres of 174 serum samples from healthy adults were determined by a standardization indirect haemagglutination test (IHA) and the conventional toxin neutralization (TN) test. The serum samples were titrated by the IHA test using glutaraldehyde-fixed and toxoid sensitized sheep erythrocytes before and after the treatment of the sera with 2-mercaptoethanol (2-ME). The IHA method has been found to be very sensitive and specific for the estimation of tetanus antitoxin in human sera. The IHA titres before the treatment of the sera with 2-ME were generally about four times higher than the TN titres and the correlation coefficient between these titres was 0.94. The IHA titres after the treatment of the sera with 2-ME were in good agreement with the TN titres and there was no statistically significant differences between the titres by the two methods. The tetanus antitoxin titres of 50% of the sera were below the minimum protective titres of tetanus antitoxin (0.01 IU/ml). In 19.5% of the sera the antitoxin level (IU/ml) ranged from 0.01 to 0.1, in 20.1% from 0.1 to 1.0 and in 10.4% from 1.0 to 10.0.     

ELISA for the routine determination of antitoxic immunity to tetanus

Serum samples from 727 persons with different vaccination histories were assessed for tetanus antitoxin content in an enzyme linked immunosorbent assay (ELISA) and tested for tetanus toxin neutralization activity in mice in order to compare the results obtained by the two methods. Neutralizing antibody activities in sera from individuals previously completely vaccinated correlated well with results obtained by ELISA and the accuracy increased with increasing antitoxin concentration in serum. This correlation was observed in sera from persons vaccinated recently as well as in sera from persons vaccinated many years ago. In sera from persons with an incomplete vaccination history ELISA was found to be an unreliable tool for the prediction of in vivo results. Many of these sera had antitoxin levels by ELISA far above the in vivo values, probably due to the presence of non specific or low avidity antitoxin which is detected in ELISA. The lowest ELISA value reliably predictive of protective antibody activity in serum irrespective of vaccination history was found to be 0.16 IU/ml. It was concluded that ELISA is useful for larger population studies as an initial test, but sera with an antitoxin content below 0.16 IU/ml should also be assessed in a neutralization system.     

The use of the Toxin Binding Inhibition (ToBI) test for the estimation of the potency of the diphtheria component of vaccines

The Toxin Binding Inhibition (ToBI) test, previously developed for the estimation of diphtheria and tetanus antitoxin in human sera, was adapted for the estimation of the potency of diphtheria components in vaccines. Data are presented to show that antitoxin titres of individual sera of mice obtained by the ToBI test are in good agreement with those obtained in the Vero cell test. In addition, diphtheria potency and 95% confidence interval of twelve batches of vaccine in different compositions were estimated by the ToBI test and the results were compared with those obtained in Vero cells. A significant correlation could be demonstrated. It is concluded from this study that the ToBI test is a valuable model in the potency assay of diphtheria toxoids, based on antitoxin induction in mice.     

Immunogenicity test of tetanus component in adsorbed vaccines by toxin binding inhibition test

Samples from 20 lots of diphtheria-tetanus (adult use dT) vaccine and from 20 lots of diphtheria-tetanus-pertussis (DTP) vaccine were used to standardize and validate the in vitro toxin binding inhibition (ToBI) test for the immunogenicity test of the tetanus component. The levels of tetanus antitoxin obtained by ToBI test were compared to those obtained using the toxin neutralization (TN) test in mice routinely employed to perform the quality control of the tetanus component in adsorbed vaccines. The results ranged from 1.8 to 3.5 IU/ml for dT and 2 to 4 IU/ml for DTP by ToBI test and 1.4 to 3 IU/ml for dT and 1.8 to 3.5 IU/ml for DTP by TN in mice. These results were significantly correlated. From this study, it is concluded that the ToBI test is an alternative to the in vivo neutralization procedure in the immunogenicity test of the tetanus component in adsorbed vaccines. A substantial refinement and a reduction in use of animals can be achieved.     

The use of the in vitro toxin binding inhibition (ToBI) test for the estimation of the potency of tetanus toxoid

The in vitro toxin binding inhibition (ToBI) test was used to determine antitoxin responses in mice immunized with tetanus toxoid. The ToBI test showed good correlation with the in vivo toxin neutralization (TN) test in titration of sera of mice immunized with various doses of DPT-Polio, DT-Polio and a tetanus reference preparation. Estimates of potency of tetanus toxoid obtained in mice by ToBI test correlated significantly with those obtained in mice by the lethal challenge test. In addition, potency values of the European reference preparation, succeedingly estimated by ToBI test and lethal challenge test in a single group of guinea-pigs, showed good correlation. From the study it is concluded that the ToBI test is a promising alternative to the toxic challenge procedure in the potency assay of tetanus toxoid vaccines. A substantial refinement and reduction in the use of animals can be achieved. Additional savings can be made by combining diphtheria and tetanus potency testing.     

TETANUS PROPHYLAXIS IN THE UNIMMUNIZED—Administration of Oxytetracycline and Intradermal Toxoid,with Restricted Use of Tetanus Antitoxin

Prophylactic tetanus antitoxin is ineffective in the prevention of experimental tetanus. That this may be true clinically is indicated by the fact that there are increasing numbers of cases of tetanus in humans after prophylactic tetanus antitoxin. Despite this known ineffectiveness and the high rate of reaction to antitoxin (5 per cent), many physicians continue to use it prophylactically, apparently for medical legal reasons. Since tetanus in civilian wounds is so rare, occurring approximately once in every million wounds, the routine use of tetanus antitoxin will probably cause more harm than good.It has been demonstrated experimentally that oxytetracycline is the most effective antimicrobial in the prevention of tetanus. It is, therefore, believed that adequate tetanus prophylaxis may be obtained by meticulous debridement and cleansing of the wound, by the administration of 1 gm. oxytetracycline daily for five days, and by intradermal administration of tetanus toxoid on the first, fourth and seventh days. Tetanus antitoxin is not given unless contaminated wounds have ben neglected for eight hours or more. In these instances, 15,000 units or more of tetanus antitoxin is given.Tetanus toxoid remains the best wound prophylaxis and greater emphasis should be placed on immunizing entire populations.     

Studies on adjuvants for human prophylactics. III. Comparison of adjuvanticity in different animal species.

Activities of common adjuvants were compared in mice, rabbits and monkeys with tetanus toxoid as an antigen. Aluminium gel showed consistently high adjuvanticity for antitoxin production in all animal species examined when administered subcutaneously. Water-in-oil in water (w/o/w) showed high activity comparable to that of aluminium in mice and rabbits but no activity in monkeys. Endotoxin was considerably effective in rabbits and monkeys but not so in mice. Production of both IgM and IgG antitoxin was promoted by the effective adjuvants in rabbits and monkeys. In mice, however, the effects of adjuvants on the production of IgM antitoxin was less significant and inconsistent. Contrary to the case of guinea pigs, tetanus antitoxin was produced in mice by ip injection to a level comparable to that induced by sc injection. The effects of adjuvants in mice administered by ip and sc injection were not significantly different from each other.     

The use of an immunoenzymatic assay for the estimation of tetanus antitoxin in human sera: a comparison with seroneutralization and indirect haemagglutination

The ability of an enzyme-linked immunosorbent assay (ELISA) to detect tetanus antitoxin in human sera has been evaluated in comparison with the in vivo seroneutralization test. The results of this study, carried out on 171 serum samples, show that ELISA is a sensitive and specific in vitro test for immunity to tetanus in man; it reveals the minimum protective level of 0.01 IU/ml and is well correlated with seroneutralization. A comparison has also been made with indirect haemagglutination. Differences in specificity in low titered sera, although not statistically significant, have been observed. Reported data suggest that the ELISA may be used for the estimation of tetanus antitoxin in sero-epidemiological surveys and for clinical purposes with reliability equal--and perhaps superior--to that of IHA.     

Immune Response to other Agents of Calves Persistently Infected with Bovine Virus Diarrhoea Virus (BVDV)

The ability of calves persistently infected (PI) with bovine virus diarrhoea virus BVDV to respond immunologically to defined antigens other than BVDV was studied. Five clinically healthy PI calves were studied together with 5 non-PI calves serving as controls. The humoral immune response was tested by measuring the serum antitoxin titre following immunization against tetanus. The cellular immune response was tested by the ability to develop a positive reaction in a cutaneous tuberculin test performed 1 month after immunization against Johne’s disease (paratuberculosis). Finally, a skin-sensitizing agent, dinitrochlorobenzene (DNCB), was employed to study whether PI calves would react by hypersensitization following skin exposure to DNCB for 7 consecutive days followed by application of DNCB to a new skin area remote from the area that had first been exposed. The response of PI calves to the various types of antigenic stimuli applied was not significantly different from that of the control calves. Thus, PI calves developed a potent antitoxin response after tetanus immunization, they showed a positive reaction to tuberculin skin test after immunization against paratuberculosis, and were skin sentitized with DNCB.     

Significance of circulating toxin and antitoxin in unimmunized tetanus cases of neonates and infants

The level of circulating tetanus toxin, antitoxin and their individual influence on the outcome of tetanus cases were determined in unimmunized 125 neonatal and 39 infant cases of tetanus. PHA (passive haemagglutination) test showed 40% positive cases for toxin while its absence in the remaining cases indicated of either toxin fixation to the central nervous system (CNS) or it got neutralized by antitoxin. TN (toxin neutralization) and PHA test carried out in 46 sera samples revealed a strong positive correlation (r = 0.9) showing that 35/46 (76%) and 38/46 (82.6%) samples were positive for antitoxin, respectively. 25.4% of the neonate and infant cases and 34% of the control group had a protective serum tetanus antitoxin level. 42.5% of the paired sera from unimmunized mothers and their neonates showing nonprotective antitoxin levels suggested that a high level of antitoxin is needed for transplacental transfer, although transfer may not play a decisive role in the resistance against the disease. The presence of toxin or antitoxin in the clinical cases did not affect the outcome of the disease, although in neonates, presence of toxin was found to be a bad prognostic sign. This study explicitly advocates for the need to improve the vaccination coverage strategy.     

Possibility of peroral revaccination against tetanus]

The authors present the results of oral revaccination of volunteers by purified tetanus toxoid. It appeared that in a dose of 500 BU tetanus toxoid covered with no special coat, produced no immunological effect. As to the coated toxoid-the same dose produced and increase in the antitoxin titre to the protective level, and greater.     

Transplacental antibodies. Part II: Maternal antibodies against the toxins of C. diphtheriae and C. tetani

Examinations of 297 sera for diphtheria antitoxin and 160 sera for tetanus antitoxin were carried out in 1981. All sera were obtained from the cord blood of mothers between 15 and 34 years of age. The mothers were divided into four age groups each of which was further subdivided into the primipara and multipara subgroups. The aim was to assess the age-specific variations in response to active immunization against diphtheria and tetanus. The protective level of diphtheria antitoxin (at least 0.01 I.U./ml) was recorded in the serum of 96.3% of examinees and the rates of seropositivity were found to fall with increasing age. The protective level of tetanus antitoxin (at least 0.1 I.U./ml) was found in the serum of 95.2% of mothers. The serologic response encountered in groups of older mothers was a clear-cut demonstration that the country-wide mass immunization against tetanus carried out between 1974 and 1975 was highly effective and fully justified. The variations in the diphtheria and tetanus antitoxin levels found in the primipara and multipara subgroups were not statistically significant.     

Evaluation of a guinea pig model to assess interference in the immunogenicity of different components of a combination vaccine comprising diphtheria, tetanus and acellular pertussis (DTaP) vaccine and haemophilus influenzae type b capsular polysaccharide conjugate vaccine.

A guinea pig model to assess the immunogenicity of a combination vaccine containing diphtheria, tetanus and acellular pertussis (DTaP) vaccine and Haemophilus influenzae type b (Hib) capsular polysaccharide conjugated to tetanus toxoid (HibT) was evaluated comparatively with the mouse immunogenicity test to study the effect of combining these antigens on the immunogenicity of various components. The immunogenicity test in mice was performed by subcutaneous injection of groups of 10 animals twice at an interval of four weeks with 1/10 of a single human dose of various formulations of combination vaccines, DTaP or HibT vaccine. The animals were bled at 4 and 6 weeks and IgG or total antibodies to various components were determined by ELISA or RIA. The guinea pig immunogenicity model included groups of animals injected subcutaneously twice at an interval of six weeks with 1.5 times the single human dose of various formulations. The animals were bled at 4, 6 and 8 weeks and serum samples were tested for antibodies to various components by ELISA, RIA and/or neutralization tests. Additionally, potency of tetanus and diphtheria components was assessed as per the US Food and Drug Administration's regulations. Aluminium phosphate (AIPO(4)) adsorbed HibT vaccine or HibT as a combination with AIPO(4)adsorbed DTaP vaccine showed significant increases in IgG antibodies to tetanus toxin in mice as well increased tetanus antitoxin levels in guinea pigs as compared to soluble HibT vaccine. In general, combining DTaP and HibT vaccines did not affect the antibody levels to tetanus and diphtheria toxoids whereas DTaP-HibT combination vaccine elicited significantly lower IgG antibodies to pertussis toxin and filamentous haemagglutinin than DTaP vaccine alone, particularly after first injection. Mice showed similar Hib antibody responses for the combination and HibT alone whereas guinea pigs consistently showed lower anamnestic responses to Hib for combination formulations than for HibT alone. Reducing the amount of HibT and/or tetanus toxoid in the combination formulations reduced this suppression of Hib antibody response in guinea pigs. Suppression of Hib antibody response in combination vaccines has also been reported from recent clinical trials. Based on the results from this study, it appears that the guinea pig model may be able to predict the human response to various components of combination vaccines.     

Immunity to tetanus: tetanus antitoxin and anti-BIIb in human sera

Immunity to tetanus was investigated in 157 individuals aged between 1 and 77 years using, for the evaluation of both tetanus antitoxin and antibody to fragment BIIb (anti-BIIb), an easily performed ELISA that gave reproducible results. Among these people 72% were protected against tetanus (tetanus antitoxin titres greater than 0.06 IU ml-1). Anti-BIIb titres greater than 0.15 U ml-1 were found in 75% of the males vs 57% of the females (P less than 0.02) with marked variations according to age. Furthermore, 13 out of 41 individuals with antitoxin titres less than 0.06 IU ml-1 (not protected against tetanus) were found to have anti-BIIb titres greater than 0.15 U ml-1. These data raise questions as to the significance and protective effect of anti-BIIb against tetanus.     

应用双抗原ELISA夹心法检测破伤风抗毒素效力的试验

作者建立了一套适用于破伤风抗毒素效力检测的双抗原夹心ELISA法,对破伤风类毒素免疫后的豚鼠和马匹分别进行了血清效价测定,并和传统的小鼠攻毒法的效力检测进行了比较,结果表明：该检测方法与小鼠攻毒法对不同水平的破伤风抗毒素效力检测,结果是一致的,有很好的相关性;此法省时、特异、灵敏,可成为另一种检测破伤风抗毒素的有效方法。     

Absence of Naturally Acquired Tetanus Antitoxin in the Free-Ranging Cayo Santiago Rhesus Monkeys (Macaca mulatta)

Tetanus is enzootic in the free-ranging rhesus monkey colony on Cayo Santiago. The disease accounts for 25% of all mortalities in the population. The high prevalence of tetanus provided a unique opportunity to study the potential roles of geophagia, wounding, and clinical tetanus infections on the development of naturally acquired tetanus antitoxin in rhesus macaques. Eighty-six unvaccinated monkeys, including six that recovered from tetanus, were serosurveyed using a mouse toxin neutralization test. None of the animals had detectable antitoxin titers (<0.001 AU/ml), suggesting that natural immunity to tetanus is either rare or nonexistent in the Cayo Santiago colony.