Prevalence of genetic differences in phosphorylcholine expression between nontypeable Haemophilus influenzae and Haemophilus haemolyticus |
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Authors: | Kirk W McCrea Jingping Xie Carl F Marrs Janet R Gilsdorf |
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Affiliation: | 1.Department of Pediatrics and Communicable Diseases,University of Michigan,Ann Arbor,USA;2.Department of Epidemiology,University of Michigan,Ann Arbor,USA;3.Beacon Analytical Systems Inc.,Saco,USA |
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Abstract: | Background Although non-typeable (NT) Haemophilus influenzae and Haemophilus haemolyticus are closely related human commensals, H. haemolyticus is non-pathogenic while NT H. influenzae is an important cause of respiratory tract infections. Phase-variable phosphorylcholine (ChoP) modification of lipooligosaccharide (LOS) is a NT H. influenzae virulence factor that, paradoxically, may also promote complement activation by binding C-reactive protein (CRP). CRP is known to bind more to ChoP positioned distally than proximally in LOS, and the position of ChoP within LOS is dictated by specific licD alleles (designated here as licD I , licD III , and licD IV ) that are present in a lic1 locus. The lic1 locus contains the licA-licD genes, and ChoP-host interactions may also be influenced by a second lic1 locus that allows for dual ChoP substitutions in the same strain, or by the number of licA gene tetranucleotide repeats (5'-CAAT-3') that reflect phase-variation mutation rates. |
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