haemolyticus isolates . The relationship of ChoP expression between NT H. influenzae and H. haemolyticus is unknown but differences
between the species may highlight important roles in NT H. influenzae virulence. In studies addressing NT H. influenzae virulence, ChoP-modified LOS has been shown to promote bacterial adherence and invasion Tanespimycin supplier of host cells through interaction with the platelet activating factor receptor, to increase bacterial resistance to host antimicrobial peptides such as cathelicidin (or LL-37/hCAP18), and to modulate the host inflammatory response directed toward bacteria present in biofilms [20–22]. Paradoxical to its role in enhancing colonization and virulence, ChoP can bind C-reactive protein (CRP) which initiates C1q binding that leads to activation Selleckchem Buparlisib of the classical complement pathway and bactericidal killing . The concentration of CRP (in both serum and respiratory tract secretions) dramatically increases during inflammation, and has been proposed to facilitate clearance of ChoP-expressing
bacteria in the respiratory tract [24, 25]. Human ChoP-specific antibodies capable of eliciting in vitro bactericidal activity against some H. influenzae strains have also been identified, suggesting a further liability of H. influenzae ChoP expression . H. influenzae may avoid CRP and anti-ChoP antibody binding, however, by phase varying ChoP expression and by strain-dependent localization of ChoP substitutions within LOS [27, 28]. In H. influenzae, ChoP expression is controlled by a contingency locus, lic1, that contains
the licA, licB, licC, and licD genes (encoding a choline kinase, a choline permease, a pyrophosphorylase, and a diphosphonucleoside choline transferase, respectively) . Contingency loci, such as lic1, contain simple sequence repeats (SSR) that RNA Synthesis inhibitor provide an organism with the ability to phase vary specific phenotypes in response to host challenges . In lic1, the SSR are tetranucleotide (5′-CAAT-3′) and are present at the 5′ end of licA, the first gene in the locus . During replication, intragenic SSR repeats undergo slipped-strand mispairing which results in translational phase variation, and the rate of these mutations is proportional to the length of the repeat region . De Bolle et al  found that mutation rates of a H. influenzae type III restriction modification gene (mod) engineered to contain 17-38 tetranucleotide (AGTC) intragenic repeats increased linearly with the number of repeats. In contrast, the same gene containing 5-11 repeats demonstrated rare, if any, phase-variation. Thus, higher numbers of repeats in a contingency locus may protect the bacteria by decreasing the response time to host challenges . Among H. influenzae strains, however, the number of licA gene 5′-CAAT-3′ repeats range from 3-56, and patterns pertaining to virulence have not been identified [32, 33]. Depending on the H.