Secretory antibodies specific to Streptococcus pneumoniae, Haemophilus influenzae and Branhamella catarrhalis in middle ear effusion during acute otitis media

High pneumococcal serotype specific IgG, IgG1 and IgG2 levels in serum and the middle ear of children with recurrent acute otitis media receiving ventilation tubes

Recurrent acute otitis media (AOM), frequently caused by Streptococcus pneumoniae, is a major paediatric health problem. A reduced antibody response against pneumococcal polysaccharides may contribute to an increased susceptibility to AOM. Using a multiplex bead-based assay we measured IgG, IgG1 and IgG2 levels against 11 pneumococcal polysaccharides in serum samples from 166 children below 3 years of age with a history of at least 3 episodes of acute otitis media receiving ventilation tubes, and 61 healthy controls. Pneumococcal serotype specific IgG was also determined in 144 middle ear effusion samples. Pneumococcal serotype specific IgG, IgG1 and IgG2 levels were similar in children with or without AOM, except for IgG and IgG1 levels against serotype 5, which were significantly higher in children with a history of frequent AOM (IgG: 137.5 μg/ml vs. 84.0 μg/ml; p=0.02; IgG1: 24.5 μg/ml vs. 18.2 μg/ml; p=0.05). The age-related development of pneumococcal serotype-specific IgG, IgG1 and IgG2 levels was similar in children with or without a history of AOM. Pneumococcal serotype specific IgG was present in middle ear effusion and these levels correlated significantly with serum titres. Children with a history of frequent AOM receiving ventilation tubes do not have a deficient IgG, IgG1 or IgG2 response against pneumococcal polysaccharides, either induced by vaccination or due to natural exposure. The strong correlation between IgG levels in serum and the middle ear suggests parenteral pneumococcal conjugate vaccination induces antibodies in the middle ear which may therefore contribute to reducing the burden of AOM.

Human immune response to outer membrane protein CD of Moraxella catarrhalis in adults with chronic obstructive pulmonary disease

Moraxella catarrhalis is a common cause of lower respiratory tract infection in adults with chronic obstructive pulmonary disease (COPD). The antibody response to outer membrane protein (OMP) CD, a highly conserved surface protein of M. catarrhalis under consideration as a vaccine antigen, was studied in adults with COPD following 40 episodes of infection or colonization. Following infection or colonization, 9 of 40 patients developed new serum immunoglobulin G (IgG) to OMP CD, as measured by enzyme-linked immunosorbent assay. Adsorption assays revealed that a proportion of the serum IgG was directed toward surface-exposed epitopes on OMP CD in six of the nine patients who developed new IgG to OMP CD. Immunoblot assays with fusion peptide constructs indicated that the new antibodies that developed after infection or colonization recognized conformational epitopes, particularly in the carboxy region of the protein. Three of 28 patients developed new mucosal IgA to OMP CD in sputum supernatants. This study establishes that OMP CD is a target of a systemic and mucosal immune response following infection and colonization in some patients with COPD.

Deficient IgA and IgG2 anti-pneumococcal antibody levels and response to vaccination in otitis prone children

OBJECTIVE

To evaluate the isotype and IgG subclass distribution of anti-pneumococcal antibodies and response to polysaccharide vaccination in otitis prone children.

METHODS

IgG1, IgG2 and IgA antibodies to pneumococcal serotypes 3, 4, 6B, 9V, 14, 19F and 23F were determined in otitis prone children and in an age-matched healthy control population. Patients were immunized with a 23-valent pneumococcal polysaccharide vaccine. The antibody response was measured 4 weeks later.

RESULTS

Geometric mean IgA and IgG2 antibody levels for all seven pneumococcal serotypes tested were significantly lower in otitis prone children than in the control population. After immunization, there was no significant increase in geometric mean IgG2 anti-serotype 6B, 19F and 23F pneumococcal polysaccharide (weak immunogenic), but also no increase for IgG2 anti-serotype 4 and 14. Post immunization IgG2 antibody titers for serotypes 6B, 9V and 19F even remained below titers of non-vaccinated controls. Nine out of 29 otitis prone children were colonized nasopharyngeally with Streptococcus pneumoniae during the time of vaccination; these children had an even more severely impaired systemic antibody response.

CONCLUSIONS

Otitis prone children, while having normal IgG1 antibody levels, have low IgG2 and IgA anti-polysaccharide antibody levels and fail to respond in these subclasses upon vaccination with pneumococcal polysaccharide vaccine.

Antibodies specific to outer membrane antigens of Moraxella catarrhalis in sera and middle ear effusions from children with otitis media with effusion

OBJECTIVE

Recent studies have shown that bacterial DNA is present in a significant percentage of middle ear effusions, suggesting that persistent bacterial infection may be more important in pathogenesis and recurrence of otitis media with effusion (OME) than previously considered. Although Moraxella (M.) catarrhalis is one of the most common pathogens of otitis media, relatively little is known about immune response to the organism. The objective of the present study is to investigate how systemic and local immune activities against M. catarrhalis may be associated with severity of OME.

METHODS

The antibody levels specific to outer membrane antigens of M. catarrhalis in sera and middle ear effusions (MEEs) from 59 children with OME were measured by enzyme-linked immunosorbent assay. Their ages ranged from 1 to 12 years with a median 5.0 years. The children were followed 1 year prospectively and classified into two groups with or without recurrent/persistent OME according to severity of OME during the follow-up 1 year.

RESULTS

Serum IgG, IgM, and IgA antibodies specific to outer membrane antigens of M. catarrhalis were detected in all samples and the median levels were 35, 0.93, and 1.2 microg/ml respectively. The MEE IgG, IgM, IgA, and secretory IgA antibodies were detected in over 95% samples tested and the median levels were 371, 158, 20, and 50 ng/mg total protein respectively. A comparison between acute and subacute/chronic phases revealed that the median levels of MEE IgG and IgM antibodies were higher at the acute phase (692 vs. 340, P = 0.06; 35 vs. 10, P = 0.02, respectively); while the MEE secretory IgA antibody level was increased at the subacute/chronic phase (74 vs. 35, P = 0.02). Either serum or MEE IgG antibody level was significantly lower in recurrent/persistent OME group than that in nonrecurrent/non-persistent OME group (13 vs. 43 ,microg/ml, P = 0.009; 238 vs. 577 ng/mg protein, P = 0.006, respectively).

CONCLUSIONS

These data provide additional information on the immunologic aspects of children with OME. Decreased serum and MEE IgG antibody levels specific to outer membrane antigens of M. catarrhalis may lead to failure to eliminate this organism, resulting in persistent and/or recurrent appearance of MEE.

Distribution and heritability of recurrent ear infections

The distribution of recurrent ear infections was obtained from a population-based sample of 2,750 pairs of Norwegian twins born between 1967 and 1974. The lifetime prevalence of self-reported recurrent ear infections was 8.9%, with a significant predominance of female cases. The mean age of onset was 4.2 years, with a gradual decrease in occurrence from 2 to 7 years of age. Among monozygotic pairs, the rate of tetrachoric correlation between co-twins was almost identical in males (0.73, SE 0.08) and females (0.74, SE 0.06), but among the dizygotic pairs the correlation was clearly higher in males (0.53, SE 0.12) than in females (0.20, SE 0.12). The value in the unlike-sexed dizygotic twins (0.25, SE 0.05) was intermediate to that of the like-sexed male and female dizygotic pairs. The relative contribution of genes and environment to variability in the predisposition to develop otitis media was estimated by means of structural equation modeling. Variation in liability to ear infections was mainly explained by additive genetic and dominance factors in females, for whom heritability was estimated at 74%. The remaining 26% of the variation in liability was explained by individual environmental factors. In males, 45% of the variation could be accounted for by genetic factors, 29% by common familial environment, and the remaining 26% by individual environmental effects.

Branhamella catarrhalis: epidemiology, surface antigenic structure, and immune response

Over the past decade, Branhamella catarrhalis has emerged as an important human pathogen. The bacterium is a common cause of otitis media in children and of lower respiratory tract infections in adults with chronic obstructive pulmonary disease. B. catarrhalis is exclusively a human pathogen. It colonizes the respiratory tract of a small proportion of adults and a larger proportion of children. Studies involving restriction enzyme analysis of genomic DNA show that colonization is a dynamic process, with the human host eliminating and acquiring new strains frequently. The surface of B. catarrhalis contains outer membrane proteins, lipooligosaccharide, and pili. The genes which encode several outer membrane proteins have been cloned, and some of these proteins are being studied as potential vaccine antigens. Analysis of the immune response has been limited by the lack of an adequate animal model of B. catarrhalis infection. New information regarding outer membrane structure should guide studies of the human immune response to B. catarrhalis. Immunoassays which specifically detect antibodies to determinants exposed on the bacterial surface will elucidate the most relevant immune response. The recognition of B. catarrhalis as an important human pathogen has stimulated research on the epidemiology and surface structures of the bacterium. Future studies to understand the mechanisms of infection and to elucidate the human immune response to infection hold promise of developing new methods to treat and prevent infections caused by B. catarrhalis.