Soluble phage ELISA for the identification of anti-CD4-binding site (CD4bs) specific scFv clones. RSC3 core WT along with its mutant Δ371I/P363N and negative control antigens PP-unrelated peptide pool and BSA was used at 2 µg/ml. Here, anti-CD4bs bnAbs VRC01 and b12 were used as positive controls; anti-CD4bs non-neutralizing antibody (non-nAb) b6, anti-V3 mAb 447-52D and anti-parvovirus mAb 1418 were used as negative controls along with anti-Hepatitis HepB scFv clone. The scFv Clones showing binding with RSC3 core WT antigen at least two times more than its mutant and three times than the negative control were considered as positive. The ELISA was repeated twice and mean binding titers were compared with negative controls.