Human immunoglobulin isotype and IgG subclass response to different antigens of Moraxella catarrhalis

Neisseria meningitidis, Neisseria lactamica and Moraxella catarrhalis share cross-reactive carbohydrate antigens

Carriage of commensal bacteria species is associated with the development of natural immunity to meningococcal disease, with lipo-oligosaccharides (LOS) of meningococci being one of the main virulence factors associated with severity of meningococcal disease. Meningococcal reference strains and isolates from the commensal species Neisseria lactamica and Moraxella catarrhalis were assessed for the presence of cross-reactive glycoconjugate antigens. Binding of human blood group antibodies of the P and Ii system to meningococcal immunotype reference strains were in accordance with the presence of known LOS carbohydrate structures. Binding studies with meningococcal immunotyping antibodies and blood group phenotyping antibodies to N. lactamica strains from different European countries showed, that a greater number of isolates obtained from native Greek and Scottish adults and children bound anti-meningococcal L(3, 7, 9) immunotyping (P < 0.001), pK (P = 0.035) and paragloboside (P < 0.001) blood group typing antibodies compared to isolates obtained from children of Russian immigrants in Greece. A greater number of M. catarrhalis strains isolated from children in Scotland bound anti-L(3, 7, 9) antibodies (38.2%) compared to strains isolated from adults (22.2%) (P = 0.017). These findings provide evidence that blood group like glycoconjugate antigens found on the commensal species N. lactamica and M. catarrhalis might be involved in the development of natural immunity to meningococcal endotoxins during childhood, and might be exploited as anti-meningococcal vaccine candidates.

New rapid enzyme-linked immunosorbent assay to detect antibodies against bacterial surface antigens using filtration plates

An easy and rapid ELISA system, Filtration ELISA, to detect antibodies against bacterial cell surface antigens was developed using a 96-well filtration plate fitted with a 0.22microm membrane (MultiScreen-GV, Millipore). Bacterial whole cells were used as antigens without fixing the cells with formalin etc. The whole cell antigens were washed by vacuum filtration through a filter and resuspended in washing buffer. Assay reactions could be done in the wells without losing the solution. The technique was established using antisera of mice immunized with Escherichia coli, and then evaluated by assaying antibodies to Shiga-toxin producing E. coli O157:H7 (STEC), Staphylococcus aureus and Lactobacillus acidophilus in fecal extracts of 157 children who had eaten school lunches contaminated with STEC in comparison with 25 age-matched control children. The lunch group showed significantly higher IgA antibody titers against STEC than the control group (p<0.0005), but not against L. acidphilus. The results indicate that Filtration ELISA is a quantitative and specific technique for measuring antibodies against antigens on the surface of bacteria without extracting antigens from the bacteria. This technique is widely applicable to the assay of antibodies in various samples including serum and fecal extract against various kinds of bacteria.

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.

Serum antibodies specific to CD outer membrane protein of Moraxella catarrhalis, P6 outer membrane protein of non-typeable Haemophilus influenzae and capsular polysaccharides of Streptococcus pneumoniae in children with otitis media with effusion

We measured the levels of serum IgG antibodies to CD outer membrane protein of Moraxella catarrhalis, P6 outer membrane protein of non-typeable Haemophilus influenzae and capsular polysaccharides of Streptococcus pneumoniae in 168 children with otitis media with effusion (OME) who were followed prospectively, using ELISA. Serum IgG antibodies to CD, P6 and pneumococcal capsular polysaccharides were detected in all samples. The anti-pneumococcal polysaccharides antibody level was highest, followed by the anti-P6 antibody level and anti-CD antibody was lowest (median:interquartile ranges were 45.9:19.1-100 microg/ml, 15.6:9.70-23.2 microg/ml and 1.06:0.73-1.87 microg/ml, respectively). In children aged 0-6 years, there were positive correlations among the antibody levels (anti-CD vs anti-P6, r=0.325, p <0.001; anti-CD vs anti-polysaccharide, r=0.397, p <0.0001; anti-P6 vs anti-polysaccharide, r=0.175, p=0.057). However, no relationship was seen in children aged 7-15 years. Children were classified according to severity of OME during the 1-year follow-up. In children aged 0-6 years, the severity of OME correlated inversely with the levels of anti-CD antibody (r=-.23, p=0.012), of anti-P6 antibody (r=-0.292, p=0.0015), and of anti-pneumococcal polysaccharides antibody (r=-0.25, p=0.0064). However, no correlation was found between antibody levels and severity of OME in children aged 7-15 years. These data suggest that persistence and/or recurrence of OME may be due to an insufficient serum antibody response to middle ear pathogens in young children.

Synthesis and characterization of lipooligosaccharide-based conjugates as vaccine candidates for Moraxella (Branhamella) catarrhalis

Moraxella (Branhamella) catarrhalis is an important cause of otitis media and sinusitis in children and of lower respiratory tract infections in adults. Lipooligosaccharide (LOS) is a major surface antigen of the bacterium and elicits bactericidal antibodies. Treatment of the LOS from strain ATCC 25238 with anhydrous hydrazine reduced its toxicity 20,000-fold, as assayed in the Limulus amebocyte lysate (LAL) test. The detoxified LOS (dLOS) was coupled to tetanus toxoid (TT) or high-molecular-weight proteins (HMP) from nontypeable Haemophilus influenzae through a linker of adipic acid dihydrazide to form dLOS-TT or dLOS-HMP. The molar ratios of dLOS to TT and HMP conjugates were 19:1 and 31:1, respectively. The antigenicity of the two conjugates was similar to that of the LOS, as determined by double immunodiffusion. Subcutaneous or intramuscular injection of both conjugates elicited a 50- to 100-fold rise in the geometric mean of immunoglobulin G (IgG) to the homologous LOS in mice after three injections and a 350- to 700-fold rise of anti-LOS IgG in rabbits after two injections. The immunogenicity of the conjugate was enhanced by formulation with monophosphoryl lipid A plus trehalose dimycolate. In rabbits, conjugate-induced antisera had complement-mediated bactericidal activity against the homologous strain and heterologous strains of M. catarrhalis. These results indicate that a detoxified LOS-protein conjugate is a candidate for immunization against M. catarrhalis diseases.