Immunoglobulins and immunogenicity of pneumococcal vaccination in preschool asthma

Why are people with asthma susceptible to pneumonia? A review of factors related to upper airway bacteria

Asthma and pneumonia are common respiratory conditions globally, affecting individuals of all ages. Streptococcus pneumoniae is the predominant bacterial cause of pneumonia, with nasopharyngeal carriage an important step towards invasive and pulmonary disease. Vaccines provide individual protection, and also prevent nasopharyngeal carriage, providing herd immunity. Asthma is associated with an increased risk of pneumonia, but there is limited information on the underlying mechanism of this predisposition. Both asthma and its treatment may conceivably alter propensity to, and density of, carriage through an altered epithelial microenvironment driven by disease-related inflammation or treatment-related immunomodulation, for example with inhaled corticosteroids. The relative importance of these factors could impact the efficacy of vaccines in this vulnerable patient population. In this review, we summarize the evidence for an increased risk of pneumonia in asthma, and discuss factors affecting nasopharyngeal carriage in the context of current guidelines for pneumococcal vaccination.

Response to pneumococcal polysaccharide vaccine in children with asthma, and children with recurrent respiratory infections, and healthy children

BACKGROUND

To analyse specific immune response to the 23-valent pneumococcal polysaccharide vaccine by measuring pneumococcal antibodies in children with asthma and with respiratory recurrent infection (RRI) as compared to healthy children.

METHODS

The study included 60 children, divided into three groups: 20 with asthma, 20 with RRI, and 20 healthy controls. Post-vaccination specific IgG antibodies against 10 pneumococcal serotypes (S1, S3, S4, S5, S6B, S9V, S14, S18C, S19F, and S23F) contained in the 23-valent pneumococcal polysaccharide vaccine (PPV) were measured. A specific IgG concentration ≥1.3μg/mL was considered a protective response to the vaccine. For statistical analysis, levels of specific IgG antibodies against each of the 10 pneumococcal serotypes were compared across the three groups of children using the x(2) test.

RESULTS

All of the children showed antipneumococcal antibody levels >1.3μg/mL for over 70% of the serotypes, considered within the normal range of response. Average IgG antibody levels and percentages of children protected were statistically comparable among the three groups studied.

CONCLUSION

The asthmatic children without RRI had pneumococcal antibody levels and percentages of serotype-specific protection to PPV comparable to those of healthy children. Asthmatic children with recurrent infections should be evaluated for specific antibody deficiency (SAD). Because asthma patients are at high risk for invasive pneumococcal infections, it would be worthwhile to explore systematic administration of PPV in children over the age of two years who have not received a pneumococcal conjugate vaccine, considering the positive response to PPV reported here.

Programming of the lung by early-life infection

Many important human diseases, such as asthma, have their developmental origins in early life. Respiratory infections in particular may alter the course of asthma and may either protect against or promote the development of this disease. It is likely that the nature of the effects depends on the type and age of infection and is determined by the impact of infection on the immune and respiratory systems. Immunity in early life is plastic and can be moulded by antigen encounter, which may enhance or reinforce the asthmatic phenotype of early life, or induce protective responses. Chlamydial respiratory infections have specific effects and may increase asthma severity in early life by promoting systemic interleukin 13 responses and causing permanent changes in lung structure. Respiratory viral infections, such as those of respiratory syncytial virus and rhinovirus, promote pro-asthmatic responses in early life that contribute to the induction of asthma. By contrast, probiotics or infection or exposure to certain bacteria, such as Streptococcus pneumoniae, may have protective effects in asthma by increasing the numbers and activity of regulatory T cells. Here, we review the impact of infections on the developmental origins of asthma. Understanding these effects may lead to new therapeutic approaches for asthma that either target deleterious infections or utilize beneficial ones.

Paediatric asthma and pneumococcal vaccination

Asthma is a clinical condition that has only recently been considered a risk factor for the development of pneumococcal infections. In the most recent guidelines concerning the use of pneumococcal vaccines, the Advisory Committee on Immunisation Practices recommends pneumococcal vaccination only when children with asthma aged <71 months are treated with high-dose corticosteroids, whereas the same Committee clearly indicates that asthma (without any definition of severity or treatment) is a reason for systematic pneumococcal vaccination in adults. It is also unclear which pneumococcal vaccine should be used and how to face the problem of booster doses. The main aim of this paper is to describe what is known about the real risk of pneumococcal infections in children with asthma, and discuss the unsolved problems regarding the paediatric use of pneumococcal vaccines. There are few published data regarding pneumococcal colonisation and the burden of pneumococcal disease in asthmatic children and adolescents, and none at all concerning the relationship between paediatric asthma and immune responses to pneumococcal vaccines. Further studies are therefore essential to assure that children and adolescents with asthma receive the best protection against pneumococcal diseases.

The immunogenicity of pneumococcal polysaccharides in infants and children: a meta-regression

The immunogenicity of plain (not conjugated) pneumococcal polysaccharides in children and infants was reviewed using a systematic literature search. Immunogenicity was defined as the fold-increase in serotype specific antibody concentration after a single dose of plain polysaccharide vaccine in unprimed subjects. Meta-regression was used to calculate the influence of study treatments including subject age, sampling time, dosage, immunization route, vaccine composition and study location. Immunogenicity increased with age for all serotypes, and the increase was more rapid in the first 11 months of life. Study location was the next most significant study variable, with higher responses in countries with lower GDP. A flat dose-response curve was observed over a range from 5 to 50 μg polysaccharide. Serotypes 6A, 6B, 14, 19F and 23F were significantly less immunogenic than serotypes 2, 3, 4, 7F, 8, 9N, 9V and 18C in 11 month old children, but continued to increase in immunogenicity with age until reaching similar levels at 6 years. Some proposed T-independent immune mechanisms could explain the differences in serotype immunogenicity.

Safety and immunogenicity of sequential pneumococcal immunization in preschool asthmatics

OBJECTIVE

Respiratory infections are major triggers of exacerbations in preschool asthma. Many countries' guidelines recommend immunization against pneumococci for patients suffering from chronic airway disease. Beyond infancy, however, data on the immunogenicity and safety are scarce. Also, the interval between priming and booster is a matter of debate.

PATIENTS AND METHODS

Seventy preschool asthmatics (2-5-year-old; mild to moderate asthma) underwent sequential immunization: one dose of seven-valent pneumococcal conjugate vaccine (PCV-7) followed by a single dose of 23-valent pneumococcal polysaccharide vaccine (PPV-23). We randomly assigned half of the vaccinees to receive PPV-23 eight weeks after PCV-7 (group A), and the rest to a 10-month interval (group B). Pneumococcal antibody concentrations to serotype 4, 5, 6B, 7, 9V, 14, 18c, 19F and 23F were determined initially, after two and 12 months after PCV-7. Local and systemic reactions to each vaccine were recorded.

RESULTS

Initially, depending on the serotype, up to 79.4% (group A) or 80.4% (group B) individuals did not reach the protective antibody threshold of 0.35 microg/ml. Sequential pneumococcal immunization was immunogenic in preschool asthmatics, inducing protection in the majority of our children. Subjects boostered after eight weeks had significantly lower antibody levels than those boostered after 10 months. Local and systemic adverse events were mild in character and self-limiting.

CONCLUSIONS

Although both sequential pneumococcal vaccine regimens were safe and immunogenic among preschool asthmatics, immunogenicity was higher when the booster was given after 10 months.

[Prevention of respiratory tract diseases]

There are multiple possibilities for pulmonary or bronchial damage and their number exceeds that for the other organ systems dealt with in this issue. This multiplicity of diseases which are at least in part attributable to exogenous damage gives rise to manifold approaches to prevention. This overview does not claim to be complete. It is however intended to clarify the possibilities that exist for the prevention of pulmonary diseases. In addition, it intends to show that effective primary and occasionally secondary and tertiary prevention is inadequately utilized in pulmonology or not even used at all. Against the background that individual preventive measures in pulmonology are considerably more successful than curative measures, also from a health economics point of view, various options for successful prevention are described. The great need for studies on the effectiveness of preventive strategies is also addressed.

Inhibition of allergic airways disease by immunomodulatory therapy with whole killed Streptococcus pneumoniae

Asthma is a common inflammatory disease of the airways. Current therapies alleviate symptoms but do not treat the disease. We aim to develop effective immunomodulatory therapies (IMTs) for asthma that target the underlying causes of disease based on Streptococcus pneumoniae (Spn). The effect of Spn IMT on the development of asthma [allergic airways disease (AAD)] was determined in mice. Killed Spn was administered before, during or after ovalbumin sensitization, and the subsequent development of AAD was assessed. IMT attenuated T cell cytokine production, goblet cell hyperplasia, airways hyperresponsiveness (AHR), and eosinophil numbers in the blood, bronchoalveolar lavage fluid and peribronchial tissue. This indicates the potential of Spn as an IMT for asthma.