Bispecific monoclonal antibodies against a viral and an enzyme: utilities in ultrasensitive virus ELISA and phage display technology.

A quadroma (hybrid-hybridoma) secreting bispecific antibodies with one paratope specific for M13 bacteriophage coat protein and another paratope specific for alkaline phosphatase (AP) was developed by electro-fusion of the two parental hybridomas and selected by a fluorescence activated cell sorter (FACS). The anti-phage M13/anti-AP bsMAbs were purified from anti-phage M13 monospecific MAb by a novel affinity method using Mimetic Blue A6XL as immune complexes with AP. The purified bsMAbs with potentially every molecule uniformly bound with AP generated an immuno-probe with the theoretical highest specificity. An ultrasensitive sandwich ELISA for detecting viruses was developed by using this bsMAb coupled with an amplified ELISA procedure. The sensitivity of the assay was increased 1000 times compared with conventional ELISA to achieve detection of 100 phage particles which is approximately 2.3 fg of phage coat protein. This type of bsMAb probe and ELISA format can be used to design new body fluid assays for viral load of HIV, hepatitis and other human pathogens as rapid and inexpensive alternatives to the PCR based method. This unique bispecific probe also allowed rapid and sensitive detection of bound M13/fd phage clones while panning for specific phages displaying peptide mimics against an antigen from a phage display peptide library. Furthermore, we demonstrate the principle virus purification using bsMAb as affinity ligand with a mild phosphate buffer elution. The results indicate that bsMAb could be used to develop affinity chromatography for purifying highly contagious and pathogenic viruses avoiding procedures employing prolonged high-speed centrifugation.