Pertussis IgE and atopic disease

Allergic Reactions to Vaccines in Children: From Constituents to Specific Vaccines

Vaccination is an essential public health measure that helps to reduce the burden of infectious diseases in children. Although vaccines have an excellent safety record and the association of severe allergic reactions is rare, public concerns about vaccine safety can lead to incomplete vaccination coverage in children with or without allergies. Therefore, it is important to understand the mechanisms and implications of allergic reactions to vaccines and define strategies to manage them to provide the safest care for vaccine recipients. In this review, we provide an overview on the types of allergic reactions that can occur after vaccination, including those caused by various vaccine constituents. We also discuss the mechanisms underlying these allergic reactions and the recommended diagnosis and management strategies for children with a history of suspected allergic reactions to vaccines. An improved understanding of allergic reactions to vaccines can aid in the enhancement of the safety and effectiveness of vaccination.

Whole-cell pertussis vaccine in early infancy for the prevention of allergy in children

BACKGROUND

Atopic diseases are the most common chronic conditions of childhood. The apparent rise in food anaphylaxis in young children over the past three decades is of particular concern, owing to the lack of proven prevention strategies other than the timely introduction of peanut and egg. Due to reported in vitro differences in the immune response of young infants primed with whole-cell pertussis (wP) versus acellular pertussis (aP) vaccine, we systematically appraised and synthesised evidence on the safety and the potential allergy preventive benefits of wP, to inform recommendation for future practice and research.

OBJECTIVES

To assess the efficacy and safety of wP vaccinations in comparison to aP vaccinations in early infancy for the prevention of atopic diseases in children.

SEARCH METHODS

We searched the Cochrane Central Register of Controlled Trials, Ovid MEDLINE, Embase, and grey literature. The date of the search was 7 September 2020.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and non-randomised studies of interventions (NRSIs) that reported the occurrence of atopic diseases, and RCTs only to assess safety outcomes. To be included studies had to have at least six months follow-up, and involve children under 18 years old, who received a first dose of either wP (experimental intervention) or aP (comparator) before six months of age.

DATA COLLECTION AND ANALYSIS

Two review authors independently screened studies for eligibility, extracted the data, and assessed risk of bias using standard Cochrane methods. We assessed the certainty of the evidence using GRADE. Our primary outcomes were diagnosis of IgE-mediated food allergy and all-cause serious adverse events (SAEs). Secondary outcomes included: diagnosis of not vaccine-associated anaphylaxis or urticaria, diagnosis of asthma, diagnosis of allergic rhinitis, diagnosis of atopic dermatitis and diagnosis of encephalopathy. Due to paucity of RCTs reporting on the atopic outcomes of interest, we assessed a broader outcome domain (cumulative incidence of atopic disease) as specified in our protocol. We summarised effect estimates as risk ratios (RR) and 95% confidence intervals (CI). Where appropriate, we pooled safety data in meta-analyses using fixed-effect Mantel-Haenszel methods, without zero-cell corrections for dichotomous outcomes.

MAIN RESULTS

We identified four eligible studies reporting on atopic outcomes, representing 7333 children. Based on a single trial, there was uncertain evidence on whether wP vaccines affected the risk of overall atopic disease (RR 0.85, 95% CI 0.62 to 1.17) or asthma only (RR 1.04, 95% CI 0.59 to 1.82; 497 children) by 2.5 years old.Three NRSIs were judged to be at serious or critical risk of bias due to confounding, missing data, or both, and were ineligible for inclusion in a narrative synthesis.  We identified 21 eligible studies (137,281 children) that reported the safety outcomes of interest. We judged seven studies to be at high risk of bias and those remaining, at unclear risk.  The pooled RR was 0.94 for all-cause SAEs (95% CI 0.78 to 1.15; I² = 0%; 15 studies, 38,072 children). For every 1000 children primed with a first dose of wP, 11 had an SAE. The corresponding risk with aP was 12 children (95% CI 9 to 13). The 95% CI around the risk difference ranged from three fewer to two more events per 1000 children, and the certainty of the evidence was judged as moderate (downgraded one level for imprecision). No diagnoses of encephalopathy following vaccination were reported (95% CI around the risk difference - 5 to 12 per 100,000 children; seven primary series studies; 115,271 children). The certainty of the evidence was judged as low, since this is a serious condition, and we could not exclude a clinically meaningful difference.

AUTHORS' CONCLUSIONS

There is very low-certainty evidence that a first dose of wP given early in infancy, compared to a first dose of aP, affects the risk of atopic diseases in children. The incidence of all-cause SAEs in wP and aP vaccinees was low, and no cases of encephalopathy were reported. The certainty of the evidence was judged as moderate for all-cause SAEs, and low for encephalopathy. Future studies should use sensitive and specific endpoints of clinical relevance, and should be conducted in settings with high prevalence of IgE-mediated food allergy. Safety endpoints should prioritise common vaccine reactions, parental acceptability, SAEs and their potential relatedness to the dose administered.

Further investigations of the IgE response to tetanus and diphtheria following covaccination with acellular rather than cellular Bordetella pertussis

BACKGROUND

It has previously been shown in an uncontrolled study that the IgE response to vaccine antigens is downregulated by co-vaccination with cellular Bordetella pertussis vaccine.

METHODS

In the present study, we compared in a controlled trial the humoral immune response to diphtheria toxoid (D) and tetanus toxoid (T) in relation to co-vaccinated cellular or acellular B pertussis vaccine. IgE, IgG4, and IgG to D and T were analyzed at 2, 7, and 12 months of age in sera of children vaccinated with D and T (DT, N = 68), cellular (DTPw, N = 68), 2- or 5-component acellular B pertussis vaccine (DTPa2, N = 64; DTPa5, N = 65).

RESULTS

One month after vaccination, D-IgE was detected in 10% sera of DTPw-vaccinated children, whereas vaccination in the absence of whole-cell pertussis resulted in 50%-60% IgE positivity. Six months after vaccination, the IgE antibody levels were found to be more persistent than the IgG antibodies. These diphtheria findings were mirrored by those for tetanus. Only minor differences between vaccine groups were found with regard to D-IgG and T-IgG. No immediate-type allergic reactions were observed.

CONCLUSION

Cellular (but not acellular) B pertussis vaccine downregulates IgE to co-vaccinated antigens in infants. We assume that the absence of immediate-type allergic reactions is due to the high levels of IgG antibodies competing with IgE antibodies.

Vaccination and allergy: EAACI position paper, practical aspects

Immunization is highly effective in preventing infectious diseases and therefore an indispensable public health measure. Allergic patients deserve access to the same publicly recommended immunizations as non-allergic patients unless risks associated with vaccination outweigh the gains. Whereas the number of reported possible allergic reactions to vaccines is high, confirmed vaccine-triggered allergic reactions are rare. Anaphylaxis following vaccination is rare, affecting <1/100 000, but can occur in any patient. Some patient groups, notably those with a previous allergic reaction to a vaccine or its components, are at heightened risk of allergic reaction and require special precautions. Allergic reactions, however, may occur in patients without known risk factors and cannot be predicted by currently available tools. Unwarranted fear and uncertainty can result in incomplete vaccination coverage for children and adults with or without allergy. In addition to concerns about an allergic reaction to the vaccine itself, there is fear that routine childhood immunization may promote the development of allergic sensitization and disease. Thus, although there is no evidence that routine childhood immunization increases the risk of allergy development, such risks need to be discussed.

Vaccine allergy

Overdiagnosis of vaccine allergy is considered a major public health problem. This article discusses the different types of allergic reactions after immunization based on the timing (immediate vs nonimmediate) and the extent of the reaction (local vs systemic). The vaccine components potentially responsible for an allergic reaction are discussed, as well as the management of patients with a history of reaction to a specific vaccine and those with a history of allergy to one of the vaccine components.

T-cell responses before and after the fifth consecutive acellular pertussis vaccination in 4-year-old Dutch children

Immunization with acellular pertussis vaccine (aP) induces higher specific antibody levels and fewer adverse reactions than does immunization with the whole-cell vaccine (wP). However, antibody levels in infants induced by both types of pertussis vaccines wane already after 1 year. Therefore, long-term T-cell responses upon vaccination might play a role in protection against pertussis. In a cross-sectional study (ISRCTN65428640), we investigated T-helper (Th) cell immune responses in wP- or aP-vaccinated children before and after an aP low-dose or high-dose preschool booster at 4 years of age in The Netherlands. T cells were stimulated with pertussis vaccine antigens. The numbers of gamma interferon-producing cells and Th1, Th2, Th17, and interleukin-10 (IL-10) cytokine concentrations were determined. In addition, pertussis-specific IgE levels were measured in plasma. Children being vaccinated with aP vaccinations at 2, 3, 4, and 11 months of age still showed higher pertussis-specific T-cell responses at 4 years of age than did wP-vaccinated children. These T-cell responses failed to show a typical increase in cytokine production after a fifth aP vaccination but remained high after a low-dose booster and seemed to decline even after a high-dose booster. Importantly, elevated IgE levels were induced after this booster vaccination. In contrast, wP-vaccinated children had only low prebooster T-cell responses, and these children showed a clear postbooster T-cell memory response even after a low-dose booster vaccine. Four high-dose aP vaccinations in infancy induce high T-cell responses still present even 3 years after vaccination and enhanced IgE responses after preschool booster vaccination. Therefore, studies of changes in vaccine dosage, timing of pertussis (booster) vaccinations, and the possible association with local side effects are necessary.

Attenuated Bordetella pertussis vaccine strain BPZE1 modulates allergen-induced immunity and prevents allergic pulmonary pathology in a murine model

BACKGROUND

Virulent Bordetella pertussis, the causative agent of whooping cough, exacerbates allergic airway inflammation in a murine model of ovalbumin (OVA) sensitization. A live genetically attenuated B. pertussis mucosal vaccine, BPZE1, has been developed that evokes full protection against virulent challenge in mice but the effect of this attenuated strain on the development of allergic responses is unknown.

OBJECTIVE

To assess the influence of attenuated B. pertussis BPZE1 on OVA priming in a murine model of allergic airway inflammation.

METHODS

Mice were challenged with virulent or attenuated strains of B. pertussis, and sensitized to allergen (OVA) at the peak of bacterial carriage. Subsequently, airway pathology, local inflammation and OVA-specific immunity were examined.

RESULTS

In contrast to virulent B. pertussis, live BPZE1 did not exacerbate but reduced the airway pathology associated with allergen sensitization. BPZE1 immunization before allergen sensitization did not have an adjuvant effect on allergen specific IgE but resulted in a statistically significant decrease in airway inflammation in tissue and bronchoalveolar lavage fluid. BPZE1 significantly reduced the levels of OVA-driven IL-4, IL-5 and IL-13 but induced a significant increase in IFN-gamma in response to OVA re-stimulation.

CONCLUSIONS

These data demonstrate that, unlike virulent strains, the candidate attenuated B. pertussis vaccine BPZE1 does not exacerbate allergen-driven airway pathology. BPZE1 may represent an attractive T-helper type 1 promoting vaccine candidate for eradication of whooping cough that is unlikely to promote atopic disease.

Early atopic disease and early childhood immunization--is there a link?

BACKGROUND

There are frequent concerns about early immunizations among the parents of children at heightened risk for atopy. The study assessed the effect of vaccine immunization before the first birthday on eczema severity and allergic sensitization in the second year of life.

METHODS

A total of 2184 infants, aged 1-2 years, with established atopic dermatitis and a family history of allergy, from 97 study centres in 10 European countries, South Africa and Australia were included. Exposure to vaccines (diphtheria, tetanus, pertussis, polio, Haemophilus influenzae Type B, hepatitis B, mumps, measles, rubella, varicella, BCG, meningococci and pneumococci) and immunization dates were recorded from immunization cards. Immunoglobulin E (IgE) was determined by RAST and eczema severity was assessed by scoring atopic dermatitis (SCORAD).

RESULTS

Immunization against any target was not associated with an increased risk of allergic sensitization to food or inhalant allergens. Varicella immunization (only 0.7% immunized) was inversely associated with total IgE > 30 kU/l (OR 0.27; 95% CI 0.08-0.87) and eczema severity (OR 0.34; 95% CI 0.12-0.93). Pertussis immunization (only 1.7% nonimmunized) was inversely associated with eczema severity (OR 0.30; 95% CI 0.10-0.89). Cumulative received vaccine doses were inversely associated with eczema severity (P = 0.0107). The immunization coverage of infants before and after the onset of atopic dermatitis was similar.

CONCLUSION

In children at heightened risk for atopy, common childhood immunization in the first year is not associated with an increased risk of more severe eczema or allergic sensitization. Parents of atopic children should be encouraged to fully immunize their children.

Delay in diphtheria, pertussis, tetanus vaccination is associated with a reduced risk of childhood asthma

BACKGROUND

Early childhood immunizations have been viewed as promoters of asthma development by stimulating a T(H)2-type immune response or decreasing microbial pressure, which shifts the balance between T(H)1 and T(H)2 immunity.

OBJECTIVE

Differing time schedules for childhood immunizations may explain the discrepant findings of an association with asthma reported in observational studies. This research was undertaken to determine whether timing of diphtheria, pertussis, tetanus (DPT) immunization has an effect on the development of childhood asthma by age 7 years.

METHODS

This was a retrospective longitudinal study of a cohort of children born in Manitoba in 1995. The complete immunization and health care records of cohort children from birth until age 7 years were available for analysis. The adjusted odds ratio for asthma at age 7 years according to timing of DPT immunization was computed from multivariable logistic regression.

RESULTS

Among 11, 531 children who received at least 4 doses of DPT, the risk of asthma was reduced to (1/2) in children whose first dose of DPT was delayed by more than 2 months. The likelihood of asthma in children with delays in all 3 doses was 0.39 (95% CI, 0.18-0.86).

CONCLUSION

We found a negative association between delay in administration of the first dose of whole-cell DPT immunization in childhood and the development of asthma; the association was greater with delays in all of the first 3 doses. The mechanism for this phenomenon requires further research.

Do vaccines modify the prevalence of asthma and allergies?

Epidemiological studies suggest the hypothesis that the increase in asthma and allergies in the industrialized world can be explained by a decline in the number of infectious diseases occurring during childhood. In the context of this 'hygiene hypothesis', is immunization in early life a risk factor for promoting allergic diseases? The majority of studies, especially those conducted with more extensive populations, have not found an increased risk, and although 'not finding an increased risk' is not the same as 'the non-existence of any risk at all', it seems that the evidence is tipped in favor of the absence of risk. Conversely, although some surveys have described a protective effect of vaccination, the majority refuted this result. If there is any effect, it is probably a weak one.

Effects of a diphtheria-tetanus-acellular pertussis vaccine on immune responses in murine local lymph node and lung allergy models

We have previously shown that in mice, diphtheria-tetanus-acellular pertussis (DTaP) vaccination before Bordetella pertussis infection resulted in, besides effective clearance, immediate hypersensitivity (lung eosinophilia, increased total serum immunoglobulin E [IgE], and increased ex vivo Th2 cytokine production by cells from the bronchial lymph nodes). To better appreciate the extent of these findings, we measured DTaP vaccination effects in the local lymph node assay (LLNA) and an ovalbumin (OVA) lung allergy model. In the LLNA, mice were vaccinated or adjuvant treated before being sensitized with trimellitic anhydride (TMA; inducing a Th2-directed response) and dinitrochlorobenzene (DNCB; inducing a Th1-directed response). Compared to the adjuvant-treated controls, the vaccinated mice showed a decreased response to TMA and (to a much lesser extent) an increased response to DNCB. The decreased response to TMA coincided with increased transforming growth factor beta levels. With the exception of filamentous hemagglutinin, all vaccine constituents contributed to the decreased response to TMA. In the lung allergy model, sensitization induced OVA-specific IgE, lung pathology (peribronchiolitis, perivasculitis, and hypertrophy of the bronchiolar mucus cells) and increased the number of eosinophils, lymphocytes, and neutrophils in the bronchoalveolar lavage fluid. Vaccination failed to modulate these parameters. In conclusion, although DTaP vaccination may affect the LLNA response, we found no evidence of an effect on lung allergy.

The natural course of atopy determined by skin prick tests in patients with bronchial asthma and/or rhinitis

BACKGROUND

The skin prick test (SPT) is the cheapest, most widely used and practical method for the diagnosis of allergic diseases. The results of repeat test might show variations due to aging.

OBJECTIVE

To perform repeat SPTs to determine possible changes in the atopy rate in general as well as changes in the allergen spectrum of atopic patients occurring over time and to identify the factors that could affect this change.

METHODS

A total of 222 patients who received a diagnosis of bronchial asthma and/or persistent rhinitis in our Adult Allergy Unit and who attended follow-up visits in the outpatient unit over a 2-year period were enrolled. SPT with 10 visit common aeroallergens were performed at the first and the second test was performed after an interval of at least 2 years.

RESULTS

The mean age was 36.4 +/- 11.4 years and 77.5 % of the patients were women. The mean interval between the two tests was 43.4 +/- 20.0 (minimum = 24-maximum = 105) months. Repeat tests showed that the atopy rate decreased from 58.6 % to 47.7 %; sensitivity rates to 10 allergens also decreased. These differences were statistically significant (p <0.05).

CONCLUSION

The atopy rate determined by SPTs tends to decrease over time. The most important factor affecting this decrease is time itself.

Common vaccine antigens inhibit allergen-induced sensitization and airway hyperresponsiveness in a murine model

BACKGROUND

Co-vaccination with cellular pertussis vaccine down-regulates allergic sensitization to diphtheria and tetanus antigens. Using a murine model, we investigated whether vaccination with diphtheria/tetanus toxoids, administered separately or simultaneously with the whole cell vaccine of Bordetella pertussis, inhibits subsequent allergen-induced immune and inflammatory responses.

METHODS

BALB/c-mice were vaccinated intracutaneously with a combination of diphtheria and tetanus toxoids or a combination of diphtheria and tetanus toxoids with a whole cell vaccine of B. pertussis (three times, days -21 to -7) prior to systemic sensitization (days 1-14) and repeated airway challenges (days 28-30) with ovalbumin.

RESULTS

Compared with negative controls, systemic sensitization and airway allergen challenges induced high serum levels of allergen-specific IgE, predominant Th2-type cytokine production, airway inflammation and development of in vivo airway hyperreactivity. Vaccination with diphtheria and tetanus toxoids prior to sensitization suppressed IgE formation and development of eosinophilic airway inflammation. Co-vaccination with a whole cell pertussis vaccine inhibited allergen sensitization, airway inflammation and development of in vivo airway hyperreactivity. Prevention was due to an allergen-specific and general shift from a predominant Th2 towards a predominant Th1 immune response.

CONCLUSION

Vaccination with diphtheria and tetanus toxoids alone or in combination with whole cell pertussis vaccine prior to allergen sensitization prevented allergen-induced Th2 immune responses. Vaccine antigens may down-regulate allergic responses to a range of common allergens.

Antibody levels to Bordetella pertussis in 10-yr-old children with atopy and atopic asthma

Suboptimal immune responses to vaccination have been suggested among atopic infants. The aim of this study was to assess the influence of atopy and atopic asthma on the humoral response to Bordetella pertussis vaccination. Immunoglobulin (Ig)G and IgA specific antibodies were measured by enzyme linked-immunosorbent assay in 102, 10-yr-old atopic children (66 of them also being asthmatics) and compared with 76 non-atopic and 53 non-atopic non-asthmatic controls of similar age. The levels of antibodies and the percentage of positives to B. pertussis were comparable in all groups. Children with a very high total serum immunoglobulin (Ig)E (Percentile (Pct) > 90th) showed higher (p = 0.01) IgG pertussis antibodies than children with very low serum IgE (Pct < 10th). In conclusion, we found normal pertussis antibody levels in atopic and in atopic asthmatic children in late childhood, thus overriding any possible suboptimal response during infancy.

Acellular pertussis vaccine protects against exacerbation of allergic asthma due to Bordetella pertussis in a murine model

The prevalence of asthma and allergic disease has increased in many countries, and there has been speculation that immunization promotes allergic sensitization. Bordetella pertussis infection exacerbates allergic asthmatic responses. We investigated whether acellular pertussis vaccine (Pa) enhanced or prevented B. pertussis-induced exacerbation of allergic asthma. Groups of mice were immunized with Pa, infected with B. pertussis, and/or sensitized to ovalbumin. Immunological, pathological, and physiological changes were measured to assess the impact of immunization on immune deviation and airway function. We demonstrate that immunization did not enhance ovalbumin-specific serum immunoglobulin E production. Histopathological examination revealed that immunization reduced the severity of airway pathology associated with sensitization in the context of infection and decreased bronchial hyperreactivity upon methacholine exposure of infected and sensitized mice. These data demonstrate unequivocally the benefit of Pa immunization to health and justify selection of Pa in mass vaccination protocols. In the absence of infection, the Pa used in this study enhanced the interleukin-10 (IL-10) and IL-13 responses and influenced airway hyperresponsiveness to sensitizing antigen; however, these data do not suggest that Pa contributes to childhood asthma overall. On the contrary, wild-type virulent B. pertussis is still circulating in most countries, and our data suggest that the major influence of Pa is to protect against the powerful exacerbation of asthma-like pathology induced by B. pertussis.

Ontogeny of the Allergic Inflammatory Response

The ability to produce allergic responses begins early in fetal life along with the development of other elements of the immune system. Among the most interesting questions related to the development of allergic disease are whether the fetus in utero commonly is exposed to sufficient allergen to induce IgE production and how much the mother's immune responses affect the developing fetal immune system. After birth, it seems that many factors, including the frequency and severity of infections and the timing and intensity of allergen and animal exposures, continue to influence immune development.

Immunization and atopy: possible implications of ethnicity

The possible effects of immunization on subsequent development of asthma and atopy remains a matter of controversy. Although some studies have suggested that immunization might increase the risk for atopic disease, a number of studies have found no association or have even reported a protective effect for immunization against atopy. Recent studies have provided evidence that ethnicity might affect the susceptibility to the immunomodulatory effects of vaccination. In this review the association between immunization and atopy and the effect of ethnicity on this association are briefly outlined. The focus will be particularly on BCG vaccination.

Transient suppression of atopy in early childhood is associated with high vaccination coverage

OBJECTIVE

To analyze prevalences of allergic sensitization and atopic disease in relation to vaccination coverage.

METHODS

A German atopy risk-enhanced birth cohort of 1314 neonates who were born in 1990 in 5 German cities was studied. A total of 943 children participated in the follow-up visit at 5 years of age. Atopic symptoms and diagnoses (derived from structured interviews), total serum immunoglobulin E, and specific immunoglobulin E against 9 common allergens (CAP Radio-Allergo-Sorbent Test Fluoro-Enzyme Immunoassay) were evaluated. Children were grouped into dose percentiles according to cumulative doses of any vaccine given up to 5 years of age (<10%, 0-11 doses; 10%-50%, 12-14 doses; 51%-90%, 15-20 doses; >90%, 21-27 doses).

RESULTS

The cumulative vaccine dose was inversely related to atopic dermatitis prevalences at 6 months (13.8%, 5.2%, 5.1%, and 4.5%), 2 years (16.9%, 10.9%, 7.4%, and 3.7%), 3 years (27.6%, 16.4%, 13.5%, and 4.5%), and 5 years (28.3%, 16.0%, 9.3%, and 11.9%). Asthma followed a similar pattern at age 3 (22.4%, 8.6%, 6.7%, and 6.3%), age 4 (20.0%, 8.6%, 8.9%, and 8.1%), and age 5 (20.8%, 12.6%, 10.3%, and 5.5%). Allergic sensitization rates were inversely related to the cumulative vaccine dose at age 2 (37.5%, 29.1%, 23.8%, and 12.9%).

CONCLUSION

Children with a higher vaccination coverage seemed to be transiently better protected against development of atopy in the first years of life.

Do early childhood immunizations influence the development of atopy and do they cause allergic reactions?

Concerns about allergic side-effects of vaccines and about a possible promotion of allergic diseases contribute to incomplete vaccination rates in childhood. This article reviews the current understanding of these issues. There is evidence that pertussis and diphtheria/tetanus antigens elicit immunoglobulin E (IgE) antibody formation as part of the immune response. In murine models, pertussis toxin is an effective adjuvant for IgE formation against simultaneously administered antigens. In children, however, sensitization to unrelated antigens or development of allergic diseases do not seem to be augmented. In contrast, bacille Calmette-Guérin (BCG) and measles vaccination have been proposed as suppressors of allergy because of their T helper 1 (Th1)-fostering properties. In the murine system, BCG inhibits allergic sensitization and airway hyper-reactivity. Some epidemiological studies in humans suggest an inhibitory effect of tuberculosis on allergy. BCG vaccination in children, however, has no or merely a marginal suppressive effect on atopy. Other vaccine components such as egg proteins, gelatin, and antibiotics are a potential hazard to children with severe clinical reactions to these allergens. These rare children should be vaccinated under special precautions. In conclusion, vaccination programs do not explain the increasing prevalence of allergic diseases, but individual children may uncommonly develop an allergic reaction to a vaccine. The risks of not vaccinating children, however, far outweigh the risk for allergy. Therefore, childhood vaccination remains an essential part of child health programs and should not be withheld, even from children predisposed for allergy.

Down-regulation of IgE and IgG4 antibodies to tetanus toxoid and diphtheria toxoid by covaccination with cellular Bordetella pertussis vaccine

Pertussis (P) toxin acts as adjuvant for IgE formation against simultaneously administered Ags in animal models. P vaccination may also have an adjuvant impact on IgE formation against coadministered diphtheria (D) and tetanus (T) Ags in humans. Sera of 103 D-T-P-immunized and 319 D-T-immunized children aged 2 years were analyzed for IgE, IgG4, and IgG to D and T (radioallergosorbent test), total IgE and IgE against common inhalant allergens (CAP radioallergosorbent test fluoroenzyme immunoassay). Fewer D-T-P- than D-T-immunized children had sera positive for T-IgE (12.6 vs 53.6%, p < 0.001), T-IgG4 (71.6 vs 89.2%, p < 0.001), D-IgE (31.0 vs 70.5%, p < 0.001), and D-IgG4 (85.2 vs 93.4%, p = 0.039). Suppression of T-IgE was not dependent on the cutoff chosen for a positive test result, but was dependent on the proportion of D-T immunizations given with P. The risk for sensitization to common environmental allergens did not differ (odds ratio 0.953, 95% confidence interval 0.815-1.114). No significant differences between D-T- and D-T-P-immunized children were found with regard to T-IgG or D-IgG. In summary, IgE and IgG4 (but not IgG) serum levels to coadministered D- and T-Ags are suppressed among P-immunized children as compared with nonimmunized children. These results suggest that the presence of a microbial product during Ag exposure can down-regulate an IgE/IgG4 response in humans.

Modulation of inhaled antigen-induced IgE tolerance by ongoing Th2 responses in the lung

The normal response to inhaled Ag is the absence of Ag-specific IgE and cytokine production to later Ag challenges. Although the mechanism of this aerosol-induced IgE tolerance is not completely understood, it may prevent sensitization to inhaled Ags, which could otherwise lead to allergy and asthma. We examined the consequences of ongoing Th1 and Th2 responses in the lungs of mice during OVA inhalation to mimic conditions that may subvert tolerance and lead to sensitization. We found that concurrent, secondary Th2 lung responses to keyhole limpet hemocyanin or primary responses to Nippostrongylus larvae or Asperigillus fumagatus extract prevented establishment of IgE tolerance to aerosolized OVA. Intranasal rIL-4 given before OVA aerosolization also prevented establishment of tolerance, whereas concurrent Th1 responses to influenza virus or Mycobacterium bovis bacillus Calmette-Guérin had no effect. However, once established, aerosol tolerance to OVA could not be completely broken by OVA rechallenge concurrent with a secondary Th2 response to keyhole limpet hemocyanin or A. fumagatus extract, or by intranasal rIL-4. These data suggest that the immune status of the lung of an individual may profoundly influence the initial response to inhaled Ag, and that aerosol-induced IgE tolerance may not be appropriately established in individuals undergoing concurrent, Th2-mediated responses to Ags or pathogens.

Booster immunization of children with an acellular pertussis vaccine enhances Th2 cytokine production and serum IgE responses against pertussis toxin but not against common allergens

Acellular pertussis vaccines (Pa) protect against severe pertussis in children. However, serum antibody responses decline quickly after immunization. Studies in animal models suggest that cell-mediated immunity also contributes to protection against Bordetella pertussis, and it has already been demonstrated that Pa induce T cells that secrete type-1 and type-2 cytokines in children. In this study we examined the persistence of the T cell response and the effect of booster immunization in 4-6-year-old children. Cell-mediated immunity to B. pertussis antigens was detected in a high proportion of children more than 42 months after their last immunization. Peripheral blood mononuclear cells (PBMC) from the majority of children secreted interferon-gamma (IFN-gamma) and a smaller proportion IL-5, in response to specific antigen stimulation in vitro. However, following booster immunization, significantly higher concentrations of IL-5, but not IFN-gamma, were produced by PBMC in response to B. pertussis antigens. Furthermore, plasma IL-4 and IL-5 concentrations were increased, whereas IFN-gamma concentrations were reduced following booster immunization. It has been suggested that childhood immunization with Th2-inducing vaccines may predispose some children to atopic disease. Although we found that pertussis toxin (PT)-specific IgE was significantly increased after booster immunization in both atopic and non-atopic children, the levels of IgE to common allergens and the prevalence of positive skin prick test were unaffected by the booster vaccination. Thus, despite the enhancement of type-2 responses to B. pertussis antigens, booster vaccination with Pa does not appear to be a risk factor for allergy.