Monoclonal IgA class‐switch variants against bacterial surface antigens: molecular forms and transport into murine respiratory secretions

Abstract

The present study describes a new model for passive immunization of the respiratory tract with IgA in comparison to other isotypes. Monoclonal IgA-isotype-switch variants were isolated from different IgG-producing hybridoma clones specific for surface epitopes of bacterial respiratory tract pathogens. Analysis of the molecular form of the IgA variants revealed the simultaneous production of monomeric, dimeric and higher polymeric IgA by a single-cell line with predominance of the polymeric forms. The specificities of the IgA variants were identical to the parent IgG antibodies as demonstrated by inhibition experiments. The IgA variant antibodies were separated into monomers and polymers by gel filtration. Intravenous injection of the different molecular forms of IgA and of IgG into mice were used to investigate the transport characteristics of IgA into murine upper and lower respiratory tract secretions by the physiological route in comparison to IgG. Polymeric IgA variant, monomeric IgA variant and IgG were detected in immunologically active form in both nasal secretion and bronchoalveolar fluid as evidenced by binding to their antigens in an enzyme-linked immunosorbent assay. The relative contribution of the specific exogenous monoclonal IgA and monoclonal IgG to total IgA and IgG, respectively, was determined in secretions. Comparison of the secretion to serum transport ratios clearly indicates selective transport of polymeric IgA variant into nasal secretions relative to IgG parent antibody. Molecular and functional characteristics of the IgA variants make them ideal for passive mucosal immunization experiments and identification of protective epitopes in mucosal immunity.

Cutting Edge: Lung Mucosal Th17-Mediated Responses Induce Polymeric Ig Receptor Expression by the Airway Epithelium and Elevate Secretory IgA Levels

“…Consequently, the elevated pIgR expression by airway epithelium may promote the efficient transportation of serum IgA and IgM into the airways. The efficient delivery of polymeric Igs from blood vessels to airways has been reported in mice (21). To determine whether IL-17 produced during the Th17 inflammatory response was primarily responsible for the induction of pIgR expression, IL-17 or PBS was administered intranasally to mice and the level of pIgR expression was determined after 48 h. The administration of IL-17 (2 μg in 30 μl of PBS) alone proved effective at inducing pIgR expression by airway epithelial cells in lung tissue (Fig.…”

Transmission of IgA and IgG Monoclonal Antibodies to Mucosal Fluids following Intranasal or Parenteral Delivery

“…The same size and relative intensity of bands was also observed for MAbs TBA62, TBA83 and TBA84 (results not shown). These size characteristics correspond to those previously described for other murine IgA MAbs [13, 21]. …”

“…Nevertheless, direct quantitative comparison of the IgA and IgG concentrations is required to validate these observations. The poor transmission of IgA MAbs to the lungs was not due to a shortage of polymeric forms, which are most effective for the mucosal transport of IgA [13]. It may partly be attributed to clearance from the circulation by hepatic transport to the bile [27, 28], although the biliary clearance of IgG antibodies [29]did not impair their passage to the lungs.…”

“…Transmission of parenterally inoculated IgA to the respiratory system of rodents was reported with contradictory results: some studies suggested negligible transport from serum to either the upper or lower respiratory tract [10, 11, 12], whereas others reported selective transport of pIgA to both nasal and bronchoalveolar fluids [13]and effective protection against intranasal influenza virus challenge [14]. In this study, we prepared and characterised new IgA MAbs against two surface protein antigens of Mycobacterium tuberculosis and examined their transmission into several body fluids in comparison with the already available IgG MAbs.…”

Avoiding artifacts in the infant rat model for bacterial meningitis: use of Sangur test strips for the rapid quantification of blood contamination in cerebrospinal fluid

“…We have recently reported the use of hematuria test strips for the detection of blood contamination in respiratory tract secretions obtained from mice [10]. The procedure allowed the quantification of secretory immunoglobulins in nasal and bronchial washings by controlling for the amount of immunoglobulins in the sample that was due to contamination by blood.…”