Comparison of blocking agents for an ELISA for LPS

ELISA is a sensitive, specific, reproducible and fast method for detection of antigen-antibody reactions. In case of non-protein antigens as LPS, problems exist, such as poor proportion of coating to microplates, non-specific binding of antibodies to the plastic wells. These problems were resolved partially by Takahashi and co-workers using poly-L-lysine for coating of LPS antigens. To reduce non-specific binding, blocking agent, such as bovine serum albumin (BSA) or casein is commonly used. We have to choose the blocking agent carefully because LPS can bind proteins non-specifically. This process can inhibit binding of LPS-specific antibody to LPS and decrease the sensitivity of method. In this paper we describe an ELISA test for LPS in which normal goat serum is used for blocking. This modification increases the sensitivity of ELISA. This method is useful for detection of LPS (S, R form) and anti-LPS antibody reaction in serological cross-reaction studies.