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Infection and Immunity, August 2002, p. 4523-4533, Vol. 70, No. 8
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.8.4523-4533.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.

A hag Mutant of Moraxella catarrhalis Strain O35E Is Deficient in Hemagglutination, Autoagglutination, and Immunoglobulin D-Binding Activities

Melanie M. Pearson,1 Eric R. Lafontaine,1,{dagger} Nikki J. Wagner,1 Joseph W. St. Geme III,2 and Eric J. Hansen1*

Department of Microbiology, University of Texas Southwestern Medical Center, Dallas, Texas 75390,1 The Edward Mallinckrodt Department of Pediatrics and Department of Molecular Microbiology, Washington University School of Medicine, St. Louis, Missouri 631102

Received 20 February 2002/ Returned for modification 5 April 2002/ Accepted 6 May 2002

Previous studies correlated the presence of a 200-kDa protein on the surface of Moraxella catarrhalis with the ability of this organism to agglutinate human erythrocytes (M. Fitzgerald, R. Mulcahy, S. Murphy, C. Keane, D. Coakley, and T. Scott, FEMS Immunol. Med. Microbiol. 18:209-216, 1997). In the present study, the gene encoding the 200-kDa protein (designated Hag) of M. catarrhalis strain O35E was subjected to nucleotide sequence analysis and then was inactivated by insertional mutagenesis. The isogenic hag mutant was unable to agglutinate human erythrocytes and lost its ability to autoagglutinate but was still attached at wild-type levels to several human epithelial cell lines. The hag mutation also eliminated the ability of this mutant strain to bind human immunoglobulin D. The presence of the Hag protein on the M. catarrhalis cell surface, as well as that of the UspA1 and UspA2 proteins (C. Aebi, I. Maciver, J. L. Latimer, L. D. Cope, M. K. Stevens, S. E. Thomas, G. H. McCracken, Jr., and E. J. Hansen, Infect. Immun. 65:4367-4377, 1997), was investigated by transmission electron and cryoimmunoelectron microscopy. Wild-type M. catarrhalis strain O35E possessed a dense layer of surface projections, whereas an isogenic uspA1 uspA2 hag triple mutant version of this strain did not possess any detectable surface projections. Examination of a uspA1 uspA2 double mutant that expressed the Hag protein revealed the presence of a relatively sparse layer of surface projections, similar to those seen on a uspA2 hag mutant that expressed UspA1. In contrast, a uspA1 hag mutant that expressed UspA2 formed a very dense layer of relatively short surface projections. These results indicate that the surface-exposed Hag protein and UspA1 and UspA2 have the potential to interact both with each other and directly with host defense systems.


* Corresponding author. Mailing address: Department of Microbiology, University of Texas Southwestern Medical Center, 5323 Harry Hines Blvd., Dallas, TX 75390-9048. Phone: (214) 648-5974. Fax: (214) 648-5905. E-mail: eric.hansen{at}utsouthwestern.edu.

Editor: A. D. O'Brien

{dagger} Present address: Department of Microbiology and Immunology, Medical College of Ohio, Toledo, OH 43614-5806.


Infection and Immunity, August 2002, p. 4523-4533, Vol. 70, No. 8
0019-9567/02/$04.00+0     DOI: 10.1128/IAI.70.8.4523-4533.2002
Copyright © 2002, American Society for Microbiology. All Rights Reserved.




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