ObjectiveTo evaluate the efficacy of on-line hemoperfusion for the removal of circulating superantigens in a rat model of streptococcal shock.DesignIn vitroand experimental animal studies.SettingUniversity research laboratories.InterventionsChemically modified polystyrene-based composite fiber reinforced with polypropylene was formulated in discs and used to evaluate the removal of superantigenic toxins from culture supernatantsin vitro, and from bloodin vivo.Measurements and Main ResultsIncubation of streptococcal supernatant with a single disc reduced the concentration of the superantigen streptococcal pyrogenic exotoxin A from 90.9 ± 12.7 ng/mL with the control fiber to 32.5 ± 3.6 ng/mL with active fiber (p< .001). The active discs also brought about a dose-dependent reduction in mitogenic activity that was highly significant (counts reduced from 82,133 ± 2747 using three control discs to 26,307 ± 3547 with three active discs [p< .001]). Beginning 6 hrs after infection, animals were hemoperfused for 3 hrs over columns containing control or active fiber. At the end of the treatment period, there was a significant decrease in the number of circulating bacteria in the active group (3.5 × 104vs. 3.1 × 103colony-forming units/mL,p< .05). However, bacterial counts subsequently increased and by 15 hrs and at all subsequent time points, the number of circulating bacteria was no different between the two groups. There was a highly significant and sustained difference in circulating streptococcal pyrogenic exotoxin A levels between the groups. Streptococcal pyrogenic exotoxin A levels at 9 hrs were 19.9 ng/mL in the controls vs. 2.1 ng/mL in the active group (p= .05). Animals perfused over active fibers had a highly significant survival advantage compared with control or nonperfused groups (p< .01).ConclusionsHemoperfusion and on-line removal of superantigens merits further study as a possible treatment strategy for streptococcal shock syndromes. The mechanism by which the fibers are operating requires further investigation.