Isolation of specific antibody: Pooled human serum was diluted five times with PBS (1x) containing 0.5 M sodium chloride and mixed with antigen-sepharose conjugate. This mixture was then stirred gently on a wheel O/N at 4uC. After centrifugation the supernatant was collected and stored at 220uC for further use. The antigen-sepharose beads were then washed with 5 mL of trizma base TRIS (20 mM containing 0.5 M NaCl, pH 8.0) then with 5 mL of TRIS (20 mM, pH 8.0). The elution of bound antibody was achieved with glycine (0.1 M, pH 2.5). The fractions obtained were instantly neutralized with TRIS (1 M, pH 8.0), dialyzed against phosphate buffer (0.1M, pH 7.0) and the antibody concentration was determined by the absorbance of the solution at 280 nm.