Purification and characterization of superantigenic factors produced by viridans streptococci isolated from acute phase Kawasaki disease (KD) patients

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Viridans group streptococci (VGS) are often found predominantly in oral throat swab cultures from acute phase RD patients. If these bacteria produce mitogenic factors, they will be assumed to be a candidate as the pathogen in view of the superantigen hypothesis on the etiology of KD. Here report the production of potent mitogenic factors by four strains, tentatively named SS4, M15, K-9 and R2-6, isolated from four patients among eight acute phase KD patients studied. SS4 and M15 were identified as S.mitis, K-9 and R2-6 were as S.sanguis by use of API Strep20 and some other tests. Rabbit and human peripheral blood lymphocyte cultures were used to detect mitogenic activity. These mitogenic strains were cultured in a tryptic peptone (Mikuni peptone) -yeast extract dialysate medium, and then the culture supernatants were concentrated with a Diaflo YM10 or YM05 membrane filter, precipitated at 75% saturation of ammonium sulfate, and purified by gel permeation and ion-exchange high performance column chromatography. The mitogenic activity was found in the range of molecular size, approx. 10 to 17 kDa. Then, these factors are a basic protein because they don't adhere to an anion-exchange gel (such as DEAE-Sephacel). However, the taking declined that to do this activated was unstable and for the process of the purification to move ahead. It did the experiment used the protease inhibitors from the possibility of the existence of the proteases but there was not an affect in the activated decline. These results may suggest the difficulty on the etiology of KD. Further purification and characterization of the VGS mitogens are important in addition to know whether they are really superantigens and whether play pathogenic role in KD.