Moraxella catarrhalisOuter Membrane Protein CD Elicits Antibodies That Inhibit CD Binding to Human Mucin and Enhance Pulmonary Clearance ofM. catarrhalisin a Mouse Model

Abstract

The outer membrane protein CD of Moraxella catarrhalis is considered to be a potential vaccine antigen against Moraxella infection. We purified the native CD from isolate O35E, administered it to mice, and detected considerable titers of anti-CD antibodies. Anti-CD sera were cross-reactive towards six different M. catarrhalis isolates and promoted bacterial clearance of O35E in a pulmonary challenge model. To circumvent the difficulty of generating large quantities of CD from M. catarrhalis for vaccine use, the CD gene from O35E was cloned into Escherichia coli, and the recombinant CD, expressed without a signal sequence or fusion tags, represented ϳ70% of the total E. coli proteins. The recombinant CD formed inclusion bodies that were solubilized with 6 M urea and then purified by ion-exchange chromatography, a procedure that produced soluble CD of high purity and yield. Mice immunized with the purified recombinant CD had significant titers of anti-CD antibodies that were cross-reactive towards 24 different M. catarrhalis isolates. Upon challenge, these mice showed enhanced bacterial clearance of both O35E and a heterologous M. catarrhalis isolate, TTA24. In an in vitro assay, antisera to either the native or the recombinant CD inhibited the binding activity of CD to human tracheobronchial mucin in a serum concentration-dependent manner, and the extent of inhibition appeared to correlate with the corresponding anti-CD antibody titer and whole-cell enzyme-linked immunosorbent assay titer. Our results demonstrate that the recombinant CD is a promising vaccine candidate for preventing Moraxella infection.Moraxella catarrhalis is an important human mucosal pathogen of the respiratory tract (20,29,44). It is the third most common cause of bacterial otitis media in infants and young children (3, 40), following Streptococcus pneumoniae and nontypeable Haemophilus influenzae. Among adults, M. catarrhalis is often associated with bronchitis, laryngitis, and other respiratory diseases (1, 5). Patients with chronic obstructive pulmonary disease (COPD) are particularly vulnerable to exacerbations caused by M. catarrhalis (1,6,35). Interest in the development of a Moraxella vaccine is further stimulated by the increasing prevalence of antibiotic resistance among M. catarrhalis strains (2,8,19).The CD outer membrane protein of M. catarrhalis has been identified as a potential vaccine against Moraxella infection (9, 26) and is a safe and effective carrier for M. catarrhalis detoxified lipooligosaccharide (LOS)-based conjugates (18). Serum immunoglobulin G (IgG) antibodies specific to CD are present in infants with otitis media (25) and in children with otitis media with effusion (11). Analysis of salivary immunoglobulin A (IgA) in children with acute respiratory tract infection indicates that CD may be one of the outer membrane antigens eliciting a mucosal immune response (27). IgA antibodies against CD as well as several other surface components of M. catarrhalis are also detected in the saliva of healthy adults (28). Furthe...

Molecular Aspects ofMoraxella catarrhalisPathogenesis

“…OMP CD is a heat-modifiable highly conserved porin-like protein (46 kDa) that also plays an important role in the process of adhesion (102). OMP CD functions as an adhesin for both middle ear mucin (84,120) and A549 cells (72). It is anchored in the outer membrane via a ␤-barrel domain, which connects to the C-terminal domain via a linker region.…”

Contribution of Moraxella catarrhalis Type IV Pili to Nasopharyngeal Colonization and Biofilm Formation

“…Research efforts focusing on the pathogenesis of M. catarrhalis have been hampered largely by the lack of an effective animal model. The system used most often is the mouse pulmonary model, and while this has provided some important data, it is strictly limited to assessing bacterial clearance over a short time frame (5,23,36,40). We have provided data to demonstrate that M. catarrhalis 7169 can colonize the chinchilla NP and persist in these animals for Ͼ2 weeks.…”

Colonization of healthy children by Moraxella catarrhalis is characterized by genotype heterogeneity, virulence gene diversity and co-colonization with Haemophilus influenzae

“…MID is an outer-membrane protein (OMP) with specific affinity for soluble and cell-bound human IgD and is the only IgDbinding protein in Moraxella (Forsgren et al, 2001). Several other virulence-associated genes have been identified that may be associated with colonization and infection of M. catarrhalis, including the OMPs CopB, OMPCD, McaP, MhaB, MhaC, Msp22, Msp75, Msp78 and lipooligosaccharide (LOS) Balder et al, 2007;Lipski et al, 2007;Liu et al, 2007;Riesbeck et al, 2006;Ruckdeschel et al, 2008Ruckdeschel et al, , 2009Tan et al, 2006a). Furthermore, several of these virulence genes have also been associated with the induction of the humoral immune response, making them potential vaccine candidate genes.…”

“…UspA1 and UspA2 acquire their adherence characteristics through multifunctional binding sites, which include domains that have the ability to attach to epithelial cells via cell-associated fibronectin, laminin and vitronectin (Tan et al, 2006b). Furthermore, UspA1 includes a critical binding site for carcinoembryonic antigen-related cell adhesion molecules, which are expressed in various human tissues including respiratory epithelia (Hill & Virji, 2003;Slevogt et al, 2008 Balder et al, 2007;Lipski et al, 2007;Liu et al, 2007;Riesbeck et al, 2006;Ruckdeschel et al, 2008Ruckdeschel et al, , 2009Tan et al, 2006a). Furthermore, several of these virulence genes have also been associated with the induction of the humoral immune response, making them potential vaccine candidate genes.…”