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Activated vitronectin is adsorbed preferentially from serum by capsulate and acapsulate Opc-expressing N. meningitidis.

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posted on 20.05.2010, 02:31 authored by Claudia Sa E Cunha, Natalie J. Griffiths, Mumtaz Virji

(A) To assess which serum protein is preferentially removed from serum by Opc+ Nm, a sample of normal human serum was adsorbed three times sequentially with Opc-expressing phenotype of acapsulate C751. At each stage, aliquots of the adsorbed serum samples were retained. Unadsorbed serum and adsorbed samples were analysed by immuno-dot blot assay (followed by densitometric analysis) for activated and total Vn/Fn levels using the mAb 8E6 and the polyclonal rabbit anti-Vn or anti-fibronectin antibodies. The levels of each of these components extracted from serum by Opc+ Nm as a percent of the total present at the start of extraction are shown. In control experiments, in which Opc Nm were used, 8E6 binding to 3 x adsorbed serum did not alter significantly and amounted to less than 10% loss of aVn (blank column). (B) In a similar experiment, a sample of NHS was adsorbed sequentially with capsulate MC58 Opc+ and Opc phenotypes. The Opc+ bacteria effectively removed a large portion of aVn as assessed by mAb 8E6 binding to serum samples before and after incubation with Nm (B, left). Specific removal of Vn from NHS by Opc+ but not Opc MC58 isolates is apparent from the analysis of serum-adsorbed bacterial pellets which show that bound Vn was only significantly detectable on Opc+ bacteria that were exposed to NHS (B, right).