Tehran University of Medical Sciences Iranian Journal of Allergy, Asthma and Immunology 1735-1502 19 2 2020 04 16 149 158 Mahnaz Bezhgi Department of Biochemistry, Payame Noor University, Tehran, Iran Mohammad Fazilati Department of Biochemistry, Payame Noor University, Tehran, Iran 2019 01 02 2019 12 02 Purification and preparation of three diagnostic antigens used for the detection of human T-lymphotropic virus (HTLV)-I/-II infection in E.coli are different parts of a multi-step method. In this study, our aim was to design a chimeric protein for the simultaneous detection of HTLV-I and HTLV-II antibodies. Immunodominant B cell linear epitopes of envelope and capsid proteins of HTLV-I/-II were selected and linked together; using a suitable amino acid linker and a chimeric antigen (CA). The codon-optimized synthetic DNA encoding the CA was subcloned into the pGS21aexpression vector and CA expressed as His-GST fused protein in E. coli BL21 (DE3) cells. Then the recombinant CA was purified, using the Ni-NTA (Nickle Nitrilotriacetic acid) affinity chromatography under native conditions. The Sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE) and densitometric scanning results showed that CA accounted for 15% of the total cellular proteins and approximately 50% of the expressed histidine-glutathione s-transferase-chimeric antigen (His-GST-CA) proteins were soluble. The CA was successfully purified in one step with a purity of greater than 90%, which is suitable for antigenicity evaluations. Enzyme-linked immunosorbent assay (ELISA) results showed that the GST fused CA reacted in a concentration-dependent manner with HTLV-I/-II infected sera and was able to distinguish normal serum from HTLV-I/-II infected one with a proper sensitivity. With further validation, CA, as described in the present study could be introduced as a novel reliable, cost-effective and easy alternative for the three separate HTLV-I/-II diagnostic peptide antigens, which is prepared as a fusion with GST.  https://ijaai.tums.ac.ir/index.php/ijaai/article/view/2260