Elevated levels of maternal anti-tetanus toxin antibodies do not suppress the immune response to a Haemophilus influenzae type b polyribosylphosphate-tetanus toxoid conjugate vaccine

Reported are the effects of elevated levels of anti-tetanus antibodies on the safety and immune response to a Haemophilus influenzae type b polyribosylphosphate (PRP)-tetanus toxoid conjugate (PRP-T) vaccine. A group of Thai infants (n = 177) born to women immunized against tetanus during pregnancy were vaccinated with either a combined diphtheria-tetanus-pertussis (DTP) PRP-T vaccine or DTP and a PRP-conjugate vaccine using Neisseria meningitidis group B outer-membrane proteins as a carrier (PedVax HIB). Although most infants possessed high titres (> 1 IU/ml) of anti-tetanus antibodies, the DTP-PRP-T combined vaccine engendered an excellent antibody response to all vaccine components. In both vaccine groups > 98% of infants attained anti-PRP antibody titres > or = 0.15 microgram/ml. The geometric mean anti-PRP antibody titres were 5.41 micrograms/ml and 2.1 micrograms/ml for infants immunized with three doses of PRP-T versus two doses of PedVax HIB vaccines, respectively (P < 0.005). Similarly, the proportion of infants who achieved titres > or = 1 microgram/ml was higher in the PRP-T group (87.8%) than in the group immunized with PedVax HIB (74.2%) (P = 0.036). A subgroup analysis showed that there was no significant difference in the anti-PRP antibody response for infants exhibiting either < 1 IU of anti-tetanus antibody per millilitre or > or = 1 IU/ml at baseline. These finding indicate that pre-existing anti-carrier antibody does not diminish the immune response to the PRP moiety. All infants possessed protective levels of anti-D and anti-T antibody levels after immunization.     

Adjuvant activity of Mycobacterium bovis BCG expressing CRM197 on the immune response induced by BCG expressing tetanus toxin fragment C

In order to develop a combined recombinant Mycobacterium bovis BCG (rBCG) vaccine against diphtheria, pertussis and tetanus (DPT), we have constructed different strains of rBCG expressing tetanus toxin fragment C (FC), driven by the up-regulated M. fortuitum beta-lactamase promoter, pBlaF*. Tetanus toxin FC was expressed in comparable levels in native form or in fusion with the beta-lactamase exportation signal sequence; however, in both constructs it was localized to the cytosol. Immunization of mice with rBCG-FC or its combination with rBCG expressing CRM197, induced anti-tetanus toxin antibodies with a Th2 immunoglobulin profile. Administration of a subimmunizing dose of the diphtheria-tetanus toxoid vaccine showed that rBCG-FC primed mice for production of an intense humoral response. Interestingly, the combination of rBCG-FC and rBCG-CRM197 reduced the time required for maturation of the immune response and increased anti-tetanus toxin antibody levels, suggesting adjuvant properties for rBCG-CRM197; this combination induced 75% protection in mice challenged with 100 minimum lethal doses (MLD) of tetanus toxin. Antisera from guinea pigs immunized with this combination were shown to neutralize tetanus toxin and diphtheria toxin. Our results suggest reciprocal adjuvant effects of rBCG-FC and rBCG-CRM197, which may contribute to induction of a more effective immune response against both diseases.     

Performance and potency of tetanus toxoid: implications for eliminating neonatal tetanus.

Neonatal tetanus (NT) is a major cause of mortality in developing countries, with over 400,000 deaths estimated to occur annually. WHO has adopted the goal of eliminating NT worldwide, and a major strategy for its prevention is the administration of at least two properly spaced doses of tetanus toxoid (TT) to women of childbearing age in high-risk areas to protect passively their newborns at birth. In certain countries the locally produced TT vaccine has been shown to be subpotent, while other countries have reported NT among infants born to vaccinated women. An extensive review of production and quality control procedures was carried out between 1993 and 1995 in 8 of 22 TT-producing countries that also report NT cases, with a more superficial assessment being carried out in the remaining 14 countries. Only 4 of the 22 countries have a functioning national control authority to monitor TT production and vaccine quality. A total of 80 TT lots from 21 manufacturers in 14 of the 22 NT-reporting countries were tested for potency. Of these, 15 lots from eight manufacturers in seven countries had potency values below WHO requirements. TT potency can also be compromised by improper vaccine handling. To eliminate neonatal tetanus worldwide requires assurance that all doses of TT meet WHO production and quality requirements and that the field effectiveness of TT is monitored through systematic NT case investigations and assessment of coverage.     

The serological assessment of a tetanus toxoid field trial

To determine the effectiveness of a method for controlling tetanus neonatorum, a double-blind controlled trial involving 1 618 women was conducted between 1961 and 1966. Women in the study were given 1-3 injections (1 ml) of aluminium-phosphate-adsorbed tetanus toxoid or a placebo (influenza vaccine). At the conclusion of the trial, 5-ml samples of blood were obtained from 299 women. Sera were titrated for anti-tetanus antibodies by two methods.     

Co-expression of tetanus toxin fragment C in Escherichia coli with thioredoxin and its evaluation as an effective subunit vaccine candidate

The receptor-binding domain of tetanus toxin (THc), which mediates the binding of the toxin to the nerve cells, is a candidate subunit vaccine against tetanus. In this study one synthetic gene encoding the THc was constructed and highly expressed in Escherichia coli by co-expression with thioredoxin (Trx). The purified THc-vaccinated mice were completely protected against an active toxin challenge in mouse models of disease and the potency of two doses of THc was comparable to that of three doses of toxoid vaccine. And a solid-phase assay showed that the anti-THc sera inhibited the binding of THc or toxoid to the ganglioside GT1b as the anti-tetanus toxoid sera. Furthermore, mice were vaccinated once or twice at four different dosages of THc and a dose-response was observed in both the antibody titer and protective efficacy with increasing dosage of THc and number of vaccinations. The data presented in the report showed that the recombinant THc expressed in E. coli is efficacious in protecting mice against challenge with tetanus toxin suggesting that the THc protein may be developed into a human subunit vaccine candidate designed for the prevention of tetanus.     

Immune response to tetanus booster in infants aged 15 months born prematurely with very low birth weight

Objectives

To compare humoral and cellular immune responses to tetanus booster vaccination in infants born prematurely with those born at full term and identify factors associated with the humoral response.

Methods

A prospective study was carried out on children born prematurely and with a birth weight <1500 g and with infants born at full term. At 15 months (pre-vaccination) and 18 months (post-vaccination), anti-tetanus antibodies were measured by ELISA; the intracellular interferon-gamma percentages of CD4+ T and CD8+ T cells after in vitro stimulation with tetanus toxoid were determined by flow cytometry. Chi-squared or Fisher's exact test was used to compare categorical variables. Student's t-test or Mann–Whitney test was used to compare numerical variables. Regression analysis was performed to determine factors associated with humoral immunity. Statistical significance was considered if p < 0.05.

Results

Sixty-four premature and 54 full-term infants were studied. The proportion of children immune against tetanus at 15 and 18 months was similar in both groups. The geometric mean of the antibodies was lower among the premature children at 15 months (p = 0.025) and was similar in both groups at 18 months (p = 0.852). The percentages of CD4+ and CD8+ T cells expressing intracellular IFN-γ were similar in both groups at 15 and 18 months. Gestational age <32 weeks was associated with a reduction of −0.116 IU/mL in the level of antibodies at 15 months. Breastfeeding >6 months was associated with a 3.5-fold greater chance of optimal protective (≥0.1 IU/mL) antibody level against tetanus at 15 months and an increase of 0.956 IU/mL in the level of antibodies at 18 months.

Conclusions

Humoral and cellular response following a tetanus booster was similar in both groups. Premature infants exhibited lower levels of anti-tetanus antibodies at 15 months of age, with the lowest levels in those born at a gestational age of less than 32 weeks. Breastfeeding was associated with greater levels of antibody against tetanus.     

Investigation of the baseline tetanus antibody level and its persistence in a military unit

ObjectivesTo determine tetanus antibody levels in army recruits and evaluate the persistence of immunity following tetanus booster immunization in adults.MethodsA total of 680 recruits were selected for observation of their tetanus antibody levels. From 2005 to 2015, 691 peacekeepers with tetanus vaccination were included in the questionnaire-based and serological survey based on cluster stratification. The tetanus antibody-positive rate, geometric mean concentration (GMC), and their respective changes over time were analyzed in different age groups, regions, and years after tetanus booster immunization.ResultsThe positivity rates of tetanus antibodies in the recruits and peacekeepers were 74.85% and 99.86%, respectively (χ² = 193.00, P < 0.05) and the antibody GMCs were 0.05 and 0.70 IU/mL (t = 15.73, P < 0.05). The antibody positivity rates of recruits from 12 provinces ranged from 47.62% (Hubei) to 100% (Inner Mongolia) (χ² = 37.24, P < 0.05) and the antibody GMCs ranged from 0.02 (Hubei) to 0.09 IU/mL (Heilongjiang) (F = 5.19, P < 0.01). Among the 691 peacekeepers, no statistically significant difference in antibody positivity rate was detected between men and women. After administration of one booster dose of the tetanus vaccine, a protective antibody level was calculated to persist up to 22 years; a significant difference in antibody levels was observed within 10 years between one and two or more booster doses.ConclusionThe rate at which recruits tested positive for tetanus antibodies was low. Thus, it is necessary to screen for tetanus antibodies during military recruitment and implement a precision-based booster immunization protocol for tetanus vaccine. Moreover, one dose of the tetanus vaccine booster has been calculated to maintain a protective antibody level up to 22 years, without the need for repeated reinforcements during this period.     

Validation of the combined toxin-binding inhibition test for determination of neutralizing antibodies against tetanus and diphtheria toxins in a vaccine field study in Viet Nam.

Determination of seroconversion and measurement of protective antibody levels in children against vaccine components are essential for gauging and monitoring the efficacy of paediatric vaccination programmes. For this purpose, we assessed the combined toxin-binding inhibition (ToBI) test for determining neutralizing antibodies to tetanus and diphtheria in a diphtheria-pertussis-tetanus (DPT) vaccine field trial in Viet Nam. A simple procedure involving collection of blood samples on filter-paper was found to be a suitable alternative to collection by venepuncture, despite a reduction in the sensitivity of the ToBI test as a result of the step necessary to elute the antibodies from the filter-paper. The results obtained demonstrate that the ToBI test can feasibly be carried out under field conditions. Preliminary results obtained with the ToBI test in DPT field trials indicate that a fourth dose of DPT vaccine one year after the third dose should be considered by developing countries.     

Sublingually administered Bacillus subtilis cells expressing tetanus toxin C fragment induce protective systemic and mucosal antibodies against tetanus toxin in mice

Sublingual (SL) immunization against infectious agents or bacterial toxins is not a common route for antigen delivery. However, in our continued search for a needle-free platform for vaccine administration, we evaluated the efficacy of SL immunization with Bacillus subtilis engineered to express tetanus toxin fragment C (TTFC). We compared the results obtained with those for intranasal (IN) immunization with the same vaccine, which we recently reported to induce complete protection in mice against a 2×LD100 challenge of tetanus toxin (Lee et al., Vaccine 28:6658-65). Groups of animals received 3-4 immunizations of 10(9)B. subtilis vegetative cells expressing TTFC given IN or SL. Other SL immunized groups received either purified recombinant TTFC (rTTFC) or B. subtilis placebo. A non-toxic mutant of Escherichia coli heat labile enterotoxin (mLT) was included as adjuvant in some of the studies. Mice inoculated by either IN or SL administration developed protective IgG antibodies against tetanus toxin challenge. Similar of higher IgA levels in saliva, vaginal wash and feces were detected in animals immunized SL with B. subtilis cells expressing TTFC compared with IN-immunized mice or mice immunized SL with rTTFC. SL immunization promoted a mixed Th1/Th2 response, based on cytokine analysis (IL-2, IL-4, IL-10 and INFγ). Antigen-stimulated tissues (lung, intestine, spleen and lymph nodes) revealed a dramatic increase in the density of MHC class II+ expressing cells compared to all other groups. The antibody response to TTFC was superior when the adjuvant mLT was excluded from IN and SL immunizations. However, SL administration of mLT induced strong systemic and mucosal antibody responses, indicating that successful use of this route of immunization is not specific to tetanus toxin. We conclude that SL immunization is a promising, effective, safe, non-invasive and convenient method for mucosal delivery of B. subtilis cells expressing tetanus vaccine and, potentially, other immunogens. SL immunization appears to induce both systemic and mucosal immune responses.     

Recombinant cholera toxin B subunit (rCTB) as a mucosal adjuvant enhances induction of diphtheria and tetanus antitoxin antibodies in mice by intranasal administration with diphtheria-pertussis-tetanus (DPT) combination vaccine

Recombinant cholera toxin B subunit (rCTB) which is produced by Bacillus brevis carrying pNU212-CTB acts as a mucosal adjuvant capable of enhancing host immune responses specific to unrelated, mucosally co-administered vaccine antigens. When mice were administered intranasally with diphtheria-pertussis-tetanus (DPT) combination vaccine consisting of diphtheria toxoid (DTd), tetanus toxoid (TTd), pertussis toxoid (PTd), and formalin-treated filamentous hemagglutinin (fFHA), the presence of rCTB elevated constantly high values of DTd- and TTd-specific serum ELISA IgG antibody titres, and protective levels of diphtheria and tetanus toxin-neutralizing antibodies but the absence of rCTB did not. Moreover, the addition of rCTB protected all mice against tetanic symptoms and deaths. DPT combination vaccine raised high levels of serum anti-PT IgG antibody titres regardless of rCTB and protected mice from Bordetella pertussis challenge. These results suggest that co-administration of rCTB as an adjuvant is necessary for induction of diphtheria and tetanus antitoxin antibodies on the occasion of intranasal administration of DPT combination vaccine.     

A randomised controlled trial with a diphtheria-tetanus-acellular pertussis (dTpa) vaccine in adults

The aim of this assessor-blinded trial was to compare the immunogenicity and reactogenicity of a candidate diphtheria, tetanus toxoids and acellular pertussis vaccine with reduced antigen content for diphtheria and pertussis (dTpa) with a licensed reduced adult-type diphtheria-tetanus vaccine Td (reduced diphtheria content) and with an experimental candidate monovalent acellular pertussis vaccine with reduced antigen content (pa). The dTpa and pa vaccines had identical pertussis antigen content. A total of 299 healthy adults (> or =18 years, mean age: 30.1 years+/-10.7) were randomised into 3 groups to receive a single dose of one of the study vaccines. In all groups, clinically significant reactions (severe) were infrequent (0-6%) and no serious adverse events were reported during the study. The incidence of local and systemic reactions following the administration of dTpa was comparable to the Td vaccine group. Of the total study group, prior to vaccination 52. 3 and 93.2% of the subjects had anti-diphtheria and anti-tetanus antibody levels > or = 0.1 IU/ml, respectively; and 73.1, 98.2 and 74.5% of the subjects were seropositive for pertussis toxin (PT), filamentous hemagglutinin (FHA) and pertactin (PRN) antibodies, respectively. One month after vaccination, a similar percentage of subjects in the dTpa and Td groups had anti-diphtheria (88.4% vs 90. 1%) and anti-tetanus (100% vs 98.9%) antibody levels > or =0.1 IU/ml. Similar anti-FHA (100%) and anti-PRN (98.9%) vaccine response rates were seen in the dTpa and pa groups, while the anti-PT vaccine response rates were 96.8 and 100.0%, respectively. The dTpa vaccine is as well tolerated and immunogenic as the licensed Td vaccine, and additionally, can also boost antibodies against pertussis.     

Missed opportunities for tetanus vaccination in pregnant women, and factors associated with seropositivity

The aim of this study was to identify the seroprevalance rate of tetanus and to determine missed opportunities for tetanus vaccination. Two hundred and twenty-seven female volunteers who were hospitalized following delivery participated in the study. Blood samples were analyzed using enzyme-linked immunoassay to measure tetanus antibody levels. In addition, a questionnaire was used to investigate the factors associated with vaccination status. Sixty-five percent of the study participants had safe protective levels of antibodies. Factors associated with antibody level were age, level of education and number of doses. Only 25.7% of women who received antenatal care (ANC) had received tetanus vaccinations. Women who received ANC from primary healthcare facilities were more likely to have been vaccinated than those who received ANC from hospitals or private practice (P < 0.05). Factors associated with both tetanus vaccination and immunizations in pregnant women should be further investigated by qualitative and quantitative studies. Knowledge, attitude and practice surveys of mothers and healthcare providers on provision of the tetanus vaccine to pregnant women need to be undertaken urgently.     

Immunoenhancement with combined rabies and aluminium-adjuvanted tetanus vaccines

The effect of combining tetanus toxoid in the same syringe with purified Vero cell rabies vaccine (PVRV) was investigated in the 2-1-1 regimen of PVRV. The 2-1-1 regimen alone was as immunogenic as the five-dose regimen, while saving one dose of vaccine and two clinic visits. When aluminium hydroxide-adsorbed tetanus toxoid was used to dissolve PVRV on days 0 (one of the two doses) and 21, the anti-rabies antibody was significantly increased. Aluminium-free tetanus toxoid was ineffective, suggesting that immunoenhancement was due to aluminium adjuvant. In addition, anti-tetanus antibody was unaffected and the side-effects were not increased by such mixing.     

A cytomegalovirus-based vaccine provides long-lasting protection against lethal Ebola virus challenge after a single dose

Ebola virus (Zaire ebolavirus; EBOV) is a highly lethal hemorrhagic disease virus that most recently was responsible for two independent 2014 outbreaks in multiple countries in Western Africa, and the Democratic Republic of the Congo, respectively. Herein, we show that a cytomegalovirus (CMV)-based vaccine provides durable protective immunity from Ebola virus following a single vaccine dose. This study has implications for human vaccination against ebolaviruses, as well as for development of a ‘disseminating’ vaccine to target these viruses in wild African great apes.     

Efficacy,heat stability and safety of intranasally administered Bacillus subtilis spore or vegetative cell vaccines expressing tetanus toxin fragment C

Bacillus subtilis strains expressing tetanus toxin fragment C (TTFC) were tested as vaccine candidates against tetanus in adult mice. Mice received three intranasal (IN) exposures to 10⁹ spores or 10⁸ vegetative cells of B. subtilis expressing recombinant TTFC. Immunized mice generated protective systemic and mucosal antibodies and survived challenge with 2× LD₁₀₀ of tetanus toxin. Isotype analysis of serum antibody indicated a balanced Th1/Th2 response. Lyophilized vaccines stored at 45 °C for ≥12 months, remained effective. Immunized conventional and SCID mice remained well, and no histological changes in brain or respiratory tract were detected. Lyophilized/reconstituted B. subtilis tetanus vaccines administered IN to mice appear safe, heat-stable, and protective against lethal tetanus challenge.     

Neonatal tetanus in the world today

Neonatal tetanus is an important cause of avoidable morbidity and mortality. In the past this disease was overlooked by the health services of many developing countries, but recently the extent and magnitude of neonatal tetanus has become clearer and shown that it is a very serious health problem in the developing countries. The results of community-based surveys show that neonatal tetanus mortality rates range from less than 5 to more than 60 per 1000 live births; these deaths represent between 23% and 72% of all neonatal deaths. The results so far suggest that this disease claims the lives of over half a million new-born children every year. All forms of tetanus, and especially neonatal tetanus, remain substantially under-reported in many countries, and routine reporting systems identify only about 2-5% of the estimated number of tetanus cases (based on the results of community surveys). More reliable and accurate estimates of the incidence and mortality from tetanus are therefore required.     

Intranasal immunization with tetanus toxoid and CNF1 as a new mucosal adjuvant protects BALB/c mice against lethal challenge

Although often requiring the development of efficient adjuvants, needle-free mucosal delivery of vaccine is of major interest as a strategy of mass immunization against infectious diseases. We report that mucosal immunization against tetanus toxoid through nasal route, together with active cytotoxic necrotizing factor 1 (CNF1), elicits a specific and long lasting anti-tetanus toxin response, comprising seric IgG and IgA, as well as mucosal IgA. Immunized mice were protected against a challenge with lethal doses of tetanus toxin (10 × LD₅₀). The Rho GTPase activating toxin CNF1 is thus an attractive mucosal adjuvant candidate for nasal vaccines.     

Humoral immunity 5 years after booster immunization with an adolescent and adult formulation combined tetanus, diphtheria, and 5-component acellular pertussis vaccine

Persistence of antibodies following a single dose of Tdap vaccine (tetanus, diphtheria, and five-component acellular pertussis vaccine for use in individuals past childhood) was evaluated in a follow-up of adolescents (N=324) and adults (N=644) who had received Tdap in earlier clinical trials. Outcome measures were seroprotection (tetanus and diphtheria) or seropositivity (pertussis) and geometric mean titers. Humoral immune responses to all antigens were robust 1 month after initial immunization; antibodies exceeded pre-immunization levels 1, 3, and 5 years later. These data will contribute to selecting the optimal interval for booster doses of Tdap.     

A possible explanation for the discrepancy between ELISA and neutralising antibodies to tetanus toxin

The structure and protective activity of tetanus antibodies elicited in rabbits after whole-cell pertussis diphtheria-tetanus vaccine (DTPw) vaccination was studied. ELISA antibody levels and toxin neutralisation activity (TNT) were measured in individual serum samples. The ratio of symmetric and asymmetric (functionally monovalent) IgG molecules was determined by concanavalin A (Con A) chromatography. This test is based on the fact that the carbohydrate group responsible for the molecular asymmetry has high affinity for the lectin Con A. Asymmetric molecule ratio was observed to increase with immunisation time, as well as differences between TNT and ELISA levels. All serum samples were overestimated by ELISA as compared to TNT assay, in line with the markedly higher proportion of asymmetric molecules which have lower toxin neutralising activity. Protective levels could not be predicted reasonably from ELISA results below 0. 222 IU/ml, because this methodology fails to discriminate between both types of antibodies and only an in vivo serum neutralisation procedure (TNT) reflects the true neutralising serum activity.     

Seroprotection against tetanus in southern Vietnam

BackgroundOngoing tetanus cases and sporadic outbreaks of vaccine-preventable diseases associated with routine vaccination programmes remain problems in many low and middle-income countries, including Vietnam. With no human-to-human transmission or natural immunity, tetanus antibody levels indicate both individual risk of tetanus and gaps in vaccination programmes.MethodsTo investigate gaps in immunity to tetanus in Vietnam, a country with a historically high level of tetanus vaccination coverage, tetanus antibodies were measure by ELISA from samples selected from a long-term serum bank, established for the purposes of general-population seroepidemiological investigations in southern Vietnam. Samples were selected from 10 provinces, focussing on age-groups targeted by national vaccination programmes for infants and pregnant women (Expanded Programme on Immunization, EPI, and Maternal and Neonatal Tetanus, MNT).ResultsAntibodies were measured from a total of 3864 samples. Highest tetanus antibody concentrations occurred in children under 4 years old, over 90 % of whom had protective levels. Approximately 70 % of children aged 7–12 years had protective antibody concentrations although there was variation among provinces. For infants and children, there were no significant differences in tetanus protection between males and females, but for adults aged 20–35 years, in five of the ten provinces surveyed, protection against tetanus was higher in females (p < 0.05) who are eligible for booster doses under the MNT programme. In seven of ten provinces, antibody concentrations were inversely related to age (p < 0.01) and protection of older individuals was generally low.ConclusionWidespread immunity to tetanus toxoid is seen in infants and young children consistent with the high coverage rates reported for diptheria tetanus toxoid and pertussis (DTP) in Vietnam. However, the lower antibody concentrations seen in older children and men suggest reduced immunity to tetanus in populations not targeted by EPI and MNT programmes.