Antibody response to unconjugated Haemophilus influenzae b and pneumococcal polysaccharide vaccines in children with recurrent infections

Disorders of Humoral Immunity in Children with IgG Subclass Deficiency and Recurrent Respiratory Infections

Respiratory tract infections in children are one of the most common causes for medical consultations. When the infections are of recurring nature, they are a major reason for the diagnostics for primary immunodeficiency that is in about 65% of cases underlain by disorders of humoral immunity. This study seeks to retrospectively evaluate the history of recurrent respiratory tract infections in children with humoral disorders and the associations among deficiencies in the immune system components. We evaluated 394 children aged 3 months to 18 years. We found 49.5% (195 cases) of children with IgG deficiencies, all of whom had normal IgE levels. There were 8.4% (33 cases) of IgA deficiency, 7.4% (29 cases) of IgM insufficiency, and 4.1% (16 cases) of CD19+ cells deficiency. The elevated level of CD19+ cells was found in 27.7% (109 out of the 394 children). Immunoglobulin deficiencies often coexisted with a deficiency in another immunoglobulin class above outlined. There was an interdependence between IgA abnormality and IgG, IgG3, and IgG4 abnormalities as well as between IgM abnormality and IgG and IgG1 abnormalities. We conclude that respiratory tract infections in children are often underlain by a convergence of IgG with both IgA and IgM abnormal states. The physiopathological meaning of this convergence for the infection course and resulting functional respiratory changes remains elusive.

Measurement of antibodies to pneumococcal, meningococcal and haemophilus polysaccharides, and tetanus and diphtheria toxoids using a 19-plexed assay

The measurement of antibody responses to vaccination is useful in the assessment of immune status in suspected immune deficiency. Previous reliance on enzyme-linked immunoabsorbent assays (ELISA) has been cumbersome, time-consuming and expensive. The availability of flow cytometry systems has led to the development of multiplexed assays enabling simultaneous measurement of antibodies to several antigens. We optimized a flow cytometric bead-based assay to measure IgG and IgM concentrations in serum to 19 antigens contained in groups of bacterial subunit vaccines: pneumococcal vaccines, meningococcal vaccines, Haemophilus influenzae b (Hib), and tetanus and diphtheria toxoid vaccines. 89-SF was employed as the standard serum. The assay was used to determine specific antibody levels in serum from 193 healthy adult donors. IgG and pneumococcal IgM antibody concentrations were measurable across 3 log10 ranges encompassing the threshold protective IgG antibody levels for each antigen. There was little interference between antibody measurements by the 19-plexed assay compared with monoplexed assays, and a lack of cross-reactive IgG antibody, but evidence for cross-reacting IgM antibody for 3/19 pneumococcal antigens. 90th centile values for 15/19 IgG concentrations and 12/12 IgM concentrations of the 193 adult sera were within these ranges and percentages of sera containing protective IgG antibody levels varied from 4% to 95% depending on antigen. This multiplexed assay can simultaneously measure antibody levels to 19 bacterial vaccine antigens. It is suitable for use in standard clinical practice to assess the in vivo immune response to test vaccinations and measure absolute antibody levels to these antigens.

Pneumococcal conjugate vaccines for preventing vaccine-type invasive pneumococcal disease and pneumonia with consolidation on x-ray in children under two years of age

BACKGROUND

Pneumonia, most commonly caused by Streptococcus pneumoniae (Pnc), is a major cause of morbidity and mortality among young children especially in developing countries. Recently, the prevalence of antibiotic-resistant Pnc has increased worldwide such that the effectiveness of preventive strategies, like the new pneumococcal conjugate vaccines (PCV) on rates of invasive pneumococcal disease (IPD) and pneumonia, needs to be evaluated.

OBJECTIVES

To determine the efficacy of PCV in reducing the incidence of IPD due to vaccine serotypes (VT) and x-ray confirmed pneumonia with consolidation of unspecified etiology in children who received PCV before 12 months of age.

SEARCH STRATEGY

We searched the following databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, Issue 1 2004), MEDLINE (1990 to March 2004) and EMBASE (1990 to December 2003). Reference list of articles, and books of abstracts of relevant symposia, were hand searched. Researchers in the field were also contacted.

SELECTION CRITERIA

Randomised controlled trials (RCTs) comparing PCV with placebo, or another vaccine, among children below two years with IPD and clinical/radiographic pneumonia as outcomes.

DATA COLLECTION AND ANALYSIS

Two reviewers independently identified eligible studies, assessed trial quality, and extracted data. Differences were resolved by discussion. The inverse variance method was used to pool effect sizes.

MAIN RESULTS

We identified four trials assessing the efficacy of PCV in reducing the incidence of IPD, two on x-ray confirmed pneumonia as outcome, and one on clinical pneumonia, with or without x-ray confirmation. Results from pooling HIV-1 negative children from the South African study with the other studies were as follows: the pooled vaccine efficacy (VE) for vaccine-type IPD was 88% (95% confidence interval (CI) 73% to 94%; fixed effect and random effects models), the effect measure was statistically significant (p <0.00001) and there was no heterogeneity (p = 0.77I2 0%); the pooled VE for all-serotype IPD was 66% (95% CI 46% to 79%; fixed effect model), the effect measure was statistically significant (p <0.00001) and there was no statistical heterogeneity (p = 0.09, I2 51%); the pooled VE for x-ray confirmed pneumonia was 22% (95% CI 11% to 31%; both fixed effect and random effects models) and there was no statistical heterogeneity (p = 0.80, I2 0%). Analyses that included all the children in the South African study (HIV-1 negative and HIV-1 positive children) and pooled with data from the other studies gave very similar results.

REVIEWERS' CONCLUSIONS

PCV is effective in reducing the incidence of IPD from all serotypes but exerts a greater effect in reducing VT IPD. Although PCV is also effective in reducing the incidence of x-ray confirmed pneumonia, there are still uncertainties about the definition of this outcome. Additional randomised controlled trials are currently in progress.

Preimmunization anti-pneumococcal antibody levels are protective in a majority of patients with cystic fibrosis

OBJECTIVE

Although invasive pneumococcal disease is infrequent in cystic fibrosis (CF), it is recommended that all patients with CF receive pneumococcal immunization. As part of a comprehensive program to immunize our clinic population, we obtained preimmunization anti-pneumococcal antibody levels. We hypothesized that the percentage of CF patients without protective levels of anti-pneumococcal antibody levels would be high, as they are exposed to frequent antibiotic therapy that may eradicate organisms before generation of an antibody response.

METHODS

An observational study of 100 patients with CF, aged 1 to 39 years, was conducted in a regional CF center. Preimmunization anti-pneumococcal antibody levels against 6 serotypes were measured by enzyme-linked immunosorbent assay. Protective antibody levels were defined as >200 ng/mL.

RESULTS

A majority of CF patients-61% to 100%, depending on age and serotype-had protective levels of pneumococcal antibody. There was a significant positive correlation between antibody level and age for 5 of the 6 serotypes tested.

CONCLUSIONS

In contradistinction to our hypothesis, the majority of CF patients have protective preimmunization anti-pneumococcal antibody levels. However, a significant proportion-between 17% and 39%, depending on the serotype-did not exhibit adequate levels. Therefore, we concur with current recommendations for pneumococcal immunization in CF.

Serum antibody response to polysaccharides in children with recurrent respiratory tract infections

We evaluated children (15-months old and older) with recurrent upper respiratory tract infections and normal levels of immunoglobulins in serum for specific polysaccharide immunodeficiency using an enzyme-linked immunosorbent assay method. Results showed that of 12 patients vaccinated with Act-HIB vaccine, one did not develop specific antibodies to Haemophilus influenzae type b, demonstrating that such immunodeficiency is present in Costa Rican children.

Impaired IgG antibody production to pneumococcal polysaccharides in patients with ataxia-telangiectasia

Various factors seem to be etiologic in the susceptibility to sinopulmonary infections in ataxia-telangiectasia (A-T) patients, i.e., low serum and salivary IgA, low serum IgG2, and even aspiration of saliva. S. pneumoniae is a common pathogen responsible from pulmonary infections and impaired antibody response to polysaccharide antigens is seen in patients with IgG2 and IgA deficiency as well as patients with CVID and WAS. We studied IgG-type antibody production to six pneumococcal serotypes in 29 A-T patients by ELISA before and 3-4 weeks after pneumococcal vaccine. The response was considered positive when the antibody titer was >10 U/ml but weak when the titer was 10-20 U/ml. Twenty-two of 29 (76%) patients did not respond to any of the serotypes, 5 (17%) showed a positive response to one serotype, 1 (3.4%) to two serotypes, and 1 (3.4%) to four serotypes. With conversion to gravimetric units (ng IgG/ml) and >1800 ng/ml (300 ng Ab N/ml) considered a positive response, 5 of 29 (17.2%) patients showed a positive response (300 ng ab N/ml) to two or fewer serotypes. All patients tested produced IgG antibody to tetanus toxoid. Sixteen of 27 (59.3%) patients had low IgG2 and four (14.8%) had low IgG3 levels, while 18 (62.1%) of 29 patients had low serum IgA. No correlation was found either between serum Ig isotype levels and antipolysaccharide antibody response or between susceptibility to infection and antibody production. The mechanism responsible for disturbed antipolysaccharide (TI-2 antigen) antibody production in patients with A-T needs to be investigated. It may provide additional information on the function of the ATM gene product and be helpful in clarifying the role of B cells and contribution of T cells in TI-2 responses.

Conjugated polysaccharide vaccines

The joining of polysaccharide antigens to various proteins can result in increased immunogenicity of vaccines composed of such antigens. This article discusses conjugated polysaccharide vaccines for Haemophilus influenzae, Streptococcus pneumoniae, and Neisseria meningitis. Increased availability and use of such vaccines may result in the ability to give more effective vaccines earlier in life, further reducing the incidence of diseases caused by these organisms.