Open AccessThe Hag Protein ofMoraxella catarrhalisStrain O35E Is Associated with Adherence to Human Lung and Middle Ear Cells
Author(s) -
Melissa M. Holm,
Serena L. Vanlerberg,
Darren D. Sledjeski,
Eric R. Lafontaine
Publication year - 2003
Publication title -
infection and immunity
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.508
H-Index - 220
eISSN - 1070-6313
pISSN - 0019-9567
DOI - 10.1128/iai.71.9.4977-4984.2003
Subject(s) - moraxella catarrhalis , moraxella (branhamella) catarrhalis , bacterial adhesin , biology , transposable element , a549 cell , mutant , microbiology and biotechnology , moraxella , cell culture , gene , virulence , bacteria , genetics , streptococcus pneumoniae , antibiotics
Previous studies have demonstrated that the Moraxella catarrhalis surface antigen UspA1 is an adhesin for Chang human conjunctival cells. The present report demonstrates that lack of UspA1 expression does not affect the adherence of strain O35E to A549 human lung cells or primary cultures of human middle ear epithelial (HMEE) cells. These results imply that another molecule mediates the adherence of M. catarrhalis to these two cell lines. To identify this adhesin, strain O35E was mutagenized with a transposon and 1,000 mutants were screened in a microcolony formation assay using A549 cells. Nine independent isolates exhibited an 8- to 19-fold reduction in adherence and contained a transposon in the same locus. Nucleotide sequence data and PCR analysis indicated that the transposons were inserted in different locations in the gene encoding the surface protein Hag. Quantitative assays using one representative transposon mutant, O35E.TN2, showed considerably decreased binding to A549 as well as HMEE cells. However, this mutant adhered at wild-type levels to Chang conjunctival cells. These findings suggest that the M. catarrhalis Hag protein is an adhesin for cell lines derived from human lung and middle ear tissues.