A1 Refereed original research article in a scientific journal
Phosphorylcholine is located in Aggregatibacter actinomycetemcomitans fimbrial protein Flp 1
Authors: Riikka Ihalin, Deyu Zhong, Maribasappa Karched, Casey Chen, Sirkka Asikainen
Publisher: Springer Nature
Publication year: 2018
Journal: Medical Microbiology and Immunology
Journal name in source: Medical microbiology and immunology
Journal acronym: Med Microbiol Immunol
Volume: 207
Issue: 5-6
First page : 329
Last page: 338
Number of pages: 10
ISSN: 1432-1831
eISSN: 1432-1831
DOI: https://doi.org/10.1007/s00430-018-0554-1
Web address : https://link.springer.com/article/10.1007/s00430-018-0554-1
Self-archived copy’s web address: https://research.utu.fi/converis/portal/detail/Publication/32101794
Phosphorylcholine (ChoP) is covalently incorporated into bacterial surface structures, contributing to host mimicry and promoting adhesion to surfaces. Our aims were to determine the frequency of ChoP display among Aggregatibacter actinomycetemcomitans strains, to clarify which surface structures bear ChoP, and whether ChoP-positivity relates to serum killing. The tested oral (N = 67) and blood isolates (N = 27) represented 6 serotypes. Mab TEPC-15 was used for immunoblotting of cell lysates and fractions and for immunofluorescence microscopy of cell surface-bound ChoP. The lysates were denatured with urea for hidden ChoP or treated with proteinase K to test whether it binds to a protein. Three ChoP-positive and two ChoP-negative strains were subjected to serum killing in the presence/absence of CRP and using Ig-depleted serum as complement source. Cell lysates and the first soluble cellular fraction revealed a < 10 kDa band in immunoblots. Among 94 strains, 27 were ChoP positive. No difference was found in the prevalence of ChoP-positive oral (21/67) and blood (6/27) strains. Immunofluorescence microscopy corresponded to the immunoblot results. Proteinase K abolished ChoP reactivity, whereas urea did not change the negative result. The TEPC-15-reactive protein was undetectable in Δflp1 mutant strain. The survival rate of serotype-b strains in serum was 100% irrespective of ChoP, but that of serotype-a was higher in ChoP-positive (85%) than ChoP-negative (71%) strains. The results suggest that a third of rough-colony strains harbor ChoP and that ChoP is attached to fimbrial subunit protein Flp1. It further seems that ChoP-positivity does not enhance but may reduce A. actinomycetemcomitans susceptibility to serum killing.
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