Increased anti-HIV-1 activity of CD4 CDR3-related synthetic peptides by scrambling and further structural modifications, including D-isomerization and dimerization

Efficient CD4 binding and immunosuppressive properties of the 13B8.2 monoclonal antibody are displayed by its CDR-H1-derived peptide CB1

A systematic exploration of the V(H)2/V(kappa)12-13 variable domains of the anti-CD4 monoclonal antibody (mAb) 13B8.2 was performed by the Spot method to screen for paratope-derived peptides (PDPs) demonstrating CD4 binding ability. Nine peptides, named CB1 to CB9, were identified, synthesized in a cyclic and soluble form and tested for binding to recombinant soluble CD4. Among them, CB1, CB2 and CB8 showed high anti-CD4 activity. Competition studies for CD4 binding indicated that PDPs CB1, CB8, and the parental mAb 13B8.2 recognized the same complementarity determining region (CDR)3-like loop region. PDP CB1 was shown to mimic the biological properties of 13B8.2 mAb in two independent cellular assays, demonstrating inhibitory activities in the micromolar range on antigen presentation and human immunodeficiency virus promoter activation. Our results indicate that the bioactive CDR-H1 PDP CB1 has retained a significant part of the parental 13B8.2 mAb properties and might be a lead for the design of anti-CD4 peptidomimetics of clinical interest.

A unique enzyme from Saccharothrix sp. catalyzing D-amino acid transfer

A newly isolated actinomycete belonging to Saccharothrix sp. was found to produce a unique enzyme catalyzing D-amino acid transfer. The enzyme, which was tentatively named D-amino acid transferase, was purified 2600-fold to electrophoretic homogeneity and the molecular mass was 41 kDa. The enzyme was D-configuration specific and recognized aromatic D-amino acid esters to form oligo D-amino acid esters. D-Phenylalanine ester was favored as substrate over other D-amino acid esters. The optimum conditions for oligo D-phenylalanine ester formation by D-amino acid transferase were pH 7.0 and 40 degrees C. The enzyme was inhibited by DAN, EPNP and DFP.