Immunoblot analysis - This technique is composed of two steps: electrophoresis transfer blot and enzyme immunoassay (EIA). The components of the polypeptide bands of each antigen on SDS-PAGE gels were blot electrotransferred onto nitrocellulose membranes according to the method of Towbin et al. (1979), with some modification. The transfer blot sheet was cut into 0.4 x 5.5 cm strips for detection of specific antibodies in each serum sample