The UspA1 Protein and a Second Type of UspA2 Protein Mediate Adherence of Moraxella catarrhalis to Human Epithelial Cells In Vitro

Abstract

The UspA1 and UspA2 proteins of Moraxella catarrhalis are structurally related, are exposed on the bacterial cell surface, and migrate as very high-molecular-weight complexes in sodium dodecyl sulfate-polyacrylamide gel electrophoresis. Previous analysis of uspA1 and uspA2 mutants of M. catarrhalis strain 035E indicated that UspA1 was involved in adherence of this organism to Chang conjunctival epithelial cells in vitro and that expression of UspA2 was essential for resistance of this strain to killing by normal human serum (C. Aebi, E. R. Lafontaine, L. D. Cope, J. L. Latimer, S. R. Lumbley, G. H. McCracken, Jr., and E. J. Hansen, Infect. Immun. 66:3113-3119, 1998). In the present study, isogenic uspA1, uspA2, and uspA1 uspA2 mutations were constructed in three additional M. catarrhalis strains: 012E, TTA37, and 046E. The uspA1 mutant of strain 012E had a decreased ability to attach to Chang cells. However, inactivation of the uspA1 gene in both strain TTA37 and strain 046E did not cause a significant decrease in attachment ability. Inactivation of the uspA2 gene of strain TTA37 did result in a loss of attachment ability. Nucleotide sequence analysis revealed that the predicted protein encoded by the uspA2 genes of both strains TTA37 and 046E had a N-terminal half that resembled the N-terminal half of UspA1 proteins, whereas the C-terminal half of this protein was nearly identical to those of previously characterized UspA2 proteins. The gene encoding this "hybrid" protein was designated uspA2H. PCR-based analysis revealed that approximately 20% of M. catarrhalis strains apparently possess a uspA2H gene instead of a uspA2 gene. The M. catarrhalis uspA1, uspA2, and uspA2H genes were cloned and expressed in Haemophilus influenzae cells, which were used to prove that both the UspA1 and UspA2H proteins can function as adhesins in vitro.Moraxella catarrhalis, an unencapsulated, gram-negative bacterium, can cause disease in both the upper and lower respiratory tracts (32). It has been estimated that approximately 20% of cases of acute bacterial otitis media in infants and young children are caused by this organism (6). M. catarrhalis is also associated with nearly one-third of infectious exacerbations of chronic obstructive pulmonary disease in adults (16). The ability of this organism to cause significant morbidity has resulted in increased efforts to develop an efficacious M. catarrhalis vaccine (35).Outer membrane proteins have received the most attention as possible M. catarrhalis vaccine candidates (9,19,20,31,33,43), and even M. catarrhalis lipooligosaccharide may contain potential vaccine components (15). A few of these outer membrane proteins, especially CopB (OMP B2) (4, 38), OMP CD (24), TbpA and TbpB (28), LbpA and LbpB (12), and UspA (ubiquitous surface protein A or HMW-OMP) (20, 26), which consists of two related proteins, UspA1 and UspA2 (2, 3), have been characterized in some detail. Furthermore, changes in expression of M. catarrhalis outer membrane proteins have been shown to affect the ability of thi...

Genome-wide analysis of DNA repeats in Burkholderia cenocepacia J2315 identifies a novel adhesin-like gene unique to epidemic-associated strains of the ET-12 lineage

“…Bioinformatic analysis of BCAM0224 predicts that this protein is an orthologue of the surface-attached collagen-binding protein YadA from Yersinia species, the best characterized member of the TAAs (Tamm et al, 1993;Koretke et al, 2006). Other members of this class, namely NadA from Neisseria meningitidis (Comanducci et al, 2002), UspA-1 and -2 from Moraxella catarrhalis (Lafontaine et al, 2000) and BadA from Bartonella henselae (Riess et al, 2004) are important pathogenicity factors, playing critical roles in processes such as bacterial adherence, biofilm formation, serum resistance and invasion of host cells (Linke et al, 2006). They represent one of the major families of surfaceexposed proteins in Gram-negative bacteria and are organized in a modular fashion, i.e.…”

Complete fiber structures of complex trimeric autotransporter adhesins conserved in enterobacteria

“…One distinct class of adhesins are the trimeric autotransporter adhesins (TAAs) (2,3), also referred to as type Vc secretion systems (4). TAAs are important virulence factors of many well-studied pathogens: Examples include YadA of Yersinia enterocolitica, a species causing enteritis, mesenteric lymphadenitis, and reactive arthritis (5); NadA of Neisseria meningitidis (6), an agent of meningitis and sepsis; BadA of Bartonella henselae (7), which is the agent of cat scratch disease; UspA1 and A2 of Moraxella catarrhalis (8), a prominent species in respiratory tract infections, and Hia of Haemophilus influenza (9), an organism causing meningitis and respiratory tract infections. Despite their role in the context of unrelated diseases, these TAAs always fulfill similar functions-adhesion to host cells, autoagglutination, and biofilm formation (3).…”

Immune Evasion ofMoraxella catarrhalisInvolves Ubiquitous Surface Protein A-Dependent C3d Binding

“…The hybrid UspA2H consists of UspA1 and UspA2 with its N-terminal (head region) and C-terminal (near-end stalk and membrane-anchored region) having shared sequence similarity with UspA1 and UspA2, respectively (17,19,20). The stalk region is highly conserved between UspA1, UspA2, and UspA2H of different strains (17,19,21). The UspAs bind the extracellular matrix proteins laminin and fibronectin and are essential for attachment of M. catarrhalis to epithelial cells (17,(22)(23)(24), and they play important roles in M. catarrhalis serum resistance by interacting with C3, C4b-binding protein (C4BP), and vitronectin (25)(26)(27)(28).…”

“…UspA1 and UspA2 are multifunctional proteins, have highly conserved epitopes, and thus are of considerable interest as potential vaccine candidates (9,18). The hybrid UspA2H consists of UspA1 and UspA2 with its N-terminal (head region) and C-terminal (near-end stalk and membrane-anchored region) having shared sequence similarity with UspA1 and UspA2, respectively (17,19,20). The stalk region is highly conserved between UspA1, UspA2, and UspA2H of different strains (17,19,21).…”

“…The UspA family consists of UspA1 (88 kDa), UspA2 (62 kDa), and the hybrid protein UspA2H (92 kDa) (16,17). All strains express UspA1 in combination with either UspA2 or UspA2H.…”