Next we investigated whether binding of rCD4 or V2and V3-loop specific antibodies to gp120 was influenced by HOCl-modified serum albumin ( Figure 3 ). These binding studies showed that mHSA, mBSA and mMSA completely inhibited binding of rCD4 to LAV gp120 at concentrations above 10 μg/ml (Figure 3a) . In control experiments, neither binding of the anti-CD4-1F6 monoclonal antibody to CD4 nor binding of the secondary HRP-conjugated antibody was inhibited by HOCl-modified serum albumins (data not shown). In addition to rCD4, binding of V3 loop-specific monoclonal antibodies was reduced but not completely inhibited at 10 μg/ml (Figure 3b ). In contrast to binding of V3 loop antibody, binding of V2 loop antibody was not inhibited by mHSA, mBSA or mMSA.