Background: Until rubella is eradicated there will be a continuing need for rubella antibody surveillance. Antigen production using recombinant DNA technology may be a viable alternative to traditional techniques of producing antigens for enzyme immunoassays (EIAs).
Objectives: To investigate the potential of bacterial fusion proteins containing rubella E1 protein sequences for use in EIAs to detect rubella antibodies.
Study design: Purified bacterial fusion proteins containing rubella E1 sequences to be used as antigens in EIAs and compared to 'traditional' assays using virus derived antigens for rubella antibody screening.
Results: cDNA clones coding for the complete rubella E1 protein sequence and subfragments of E1 were modified for expression as carboxy terminal fusions with either beta-galactosidase or glutathione-S-transferase. beta-galactosidase fusions with the complete E1 coding sequence or amino acids 201 to 307, which contain known epitopes, resulted in the production of predominantly insoluble fusion proteins unsuitable for use in EIA. Nine glutathione-S-transferase-E1 fusion proteins were produced with individual fusion proteins exhibiting varying properties with regard to the levels of protein produced, apparent stability, solubility and the potential for affinity purification using glutathione agarose. Reduction of the E1 component to only 44 amino acids containing three B-cell epitopes (Terry et al., 1988) produced an abundant soluble GST-E1 fusion protein (3.5 mug/ml), which could be affinity purified using glutathione agarose. This fusion protein has been successfully used in EIA to detect rubella antibodies.
Conclusions: We have shown that GST-E1 fusions have potential as antigens in tests for rubella antibodies.