Development of an immunoglobulin A-specific anti-Haemophilus influenzae antibody assay for detection of antibody in human mucosal secretions

A possible role for lysozyme in determining acute exacerbation in chronic bronchitis

The aggregation of non-serotypable Haemophilus influenzae (NTHI) by whole saliva from patients with chronic obstructive lung disease (COLD) was investigated. Significant differences were observed between salivary aggregating activity of a control and COLD population (P < 0.001). Saliva from patients less prone to acute exacerbations had a greater capacity to aggregate bacteria compared with saliva from patients with a predilection to infection. The mechanism of saliva-mediated aggregation of NTHI was investigated and shown to be related to lysozyme content. Lysozyme activity in saliva was measured by the turbidimetric technique and results showed that patients with chronic bronchitis had increased levels of salivary lysozyme, with a subpopulation within the non-infection-prone group having greater amounts. A significant difference was observed in salivary lysozyme between controls and non-infection-prone (P < 0.005) and infection-prone (P < 0.05) patients, respectively: the non-infection-prone patients having significantly (P < 0.005) more than the infection-prone patients. There was significant correlation (r = 0.742, P < 0.001) between salivary aggregation of NTHI and lysozyme activity. Chromatographically purified human lysozyme had a similar aggregation profile to that of saliva. There was no difference in serum and saliva lactoferrin concentrations between groups, but there was a significant increase (P < 0.05) in serum lysozyme concentration in the non-infection-prone group. This study suggests that the level of salivary lysozyme derived from macrophages may play an important role in determining resistance or susceptibility to acute bronchitis.

Toxoplasma gondii: detection of antibodies in human saliva and serum

Saliva samples from 27 patients with a recent toxoplasma infection were tested for specific IgG, IgM and IgA antibodies to Toxoplasma gondii. Thirteen of the 27 saliva samples were positive for IgG anti-T. gondii by direct agglutination and 8 of the 27 were positive for IgM anti-T. gondii by an immunosorbent agglutination assay. Twenty of the 27 saliva samples were positive for IgG antibody on toxoplasma immunoblots with three major immunodominant antigens; 38, 30 and 35 kDa. IgA results on toxoplasma immunoblots were positive for all three groups tested, recently infected patients, chronically infected and seronegative adults without distinguishing between them. The 35 and 43 kDa antigens were the most frequently detected proteins. IgM in saliva gave negative or very weak reactions. None of the eight seronegative or the 17 chronically infected adults gave positive results in any of the tests performed to detect IgG or IgM in saliva. Serial saliva and serum samples from a laboratory-infected patient were collected and tested for toxoplasma-specific IgG, IgM and IgA. IgG in saliva was detected by 27 days post infection (p.i.) and was negative by 81 days p.i.; it detected mainly the 38 and 30 kDa antigens. IgM in saliva was detected by 11 days p.i. and was negative by 81 days p.i., with no reaction on immunoblots.

Inhibition of adhesion of Haemophilus influenzae to buccal cells by respiratory secretions

The ability of salivary secretions and sputum sol from patients with chronic bronchitis to inhibit the adhesion of non-serotypable Haemophilus influenzae to human buccal epithelial cells has been examined. Specific H. influenzae antibodies were measured by an enzyme-linked immunosorbent assay (ELISA). Saliva and sputum levels of anti-H. influenzae immunoglobulin A (IgA) antibody were related inversely to buccal cell adherence (r = -0.92). Absorption of saliva and sputum sol with H. influenzae removed antibody detected by ELISA but only partially removed inhibition of attachment of bacteria. In patients with a history of recurrent bronchitis significantly more inhibitory activity remained after absorption of the secretory IgA (sIgA) specific antibody compared with patients who were resistant to acute episodes of infection (P less than 0.05). These observations suggest that factors, other than sIgA, are present in respiratory secretions and are capable of modulating H. influenzae attachment to buccal epithelial cells.

An animal model demonstration of enhanced clearance of nontypable Haemophilus influenzae from the respiratory tract after antigen stimulation of gut-associated lymphoid tissue

An animal model of the clearance of nontypable Haemophilus influenzae has been developed to determine both optimal immunization strategies for controlling colonization of the respiratory tract in patients with damaged airways and mechanisms of action of immune clearance. It was demonstrated that stimulation of gut-associated lymphoid tissue (GALT) (either by direct injection or by ingestion of antigen) followed by local administration of antigen into the bronchus was required to enhance clearance in this model. The primary effect of GALT immunization persisted for at least 6 wk; it was specific and could not be replaced by systemic immunization. Failure to stimulate locally in the bronchus was associated with protracted clearance. No clear correlation between local or systemic antibody and bacterial clearance was demonstrated; however, immunized rats were shown to have faster recruitment of phagocytic cells to the bronchial spaces, and these phagocytes had a higher activity state than cells harvested from nonimmunized animals. It is probable that bacterial clearance is accelerated in immunized animals due in part to factors mediating a change in the behavior of luminal phagocytes.