For evaluation of virus neutralizing activity, the three HOCl-modified serum albumins were first tested in an MTT-assay (Figure 4a ). Using up to 200 μg/ml of HOClmodified protein, which is at least 10-times of the mHSA concentration necessary to neutralize NL4-3 >95%, we observed no anti-cellular activity in comparison to normal serum albumin. As shown in Figure 4b , virus infection was inhibited by mHSA, and mBSA in a dosedependent manner to >95% and >90% at a concentration of each 20 μg/ml. Virus inhibition by mMSA was slightly lower and inhibition >90% was observed using 50 μg/ml of mMSA. In addition to viral infection we also tested the inhibition of syncytium formation. As shown in Figure 5 , syncytium formation induced by virus strain NL4-3 (Figure 5b) was completely inhibited by mHSA at a concentration 50 μg/ml ( Figure 5c ). As demonstrated before (Figure 4a ) mHSA did not inhibit cell proliferation and, in agreement with this observation, cell morphology and staining of the nucleus proved vitality of the GHOST cells grown in the presence of 50 μg mHSA/ml (Figure 5a, c) .