B-cell epitope mapping of the entire SIVagm envelope glycoprotein including fine mapping of immunogenic regions

To allow the precise definition of the anti-lentiviral immune response in the natural host and to facilitate the development of an alternative animal model for vaccine development, we are identifying the immunogenic domains of SIVagm proteins. First, a total of 173 synthetic 15-mer peptides with an overlap of 10 amino acids were produced spanning the entire envelope glycoprotein of the molecular clone SIVagm3. These peptides were used as antigen in enzyme-linked immunosorbent assays for identifying regions recognized by antibodies from naturally infected African green monkeys and monkeys infected with a molecular clone. Regions corresponding to the HIV-1 V3, the transmembrane protein (TMP) "Gnann peptide", and the C-terminal area of the outer envelope protein were shown to be immunodominant. These regions were re-synthesized as 15-mer peptides with an overlap of 14 amino acids and used to precisely map the epitopes recognized. Sera from 93 captive and 61 wild animals were tested by SIVagm-specific Western blot (WB) and for ELISA reactivity against the immunodominant TMP peptide. One hundred percent (76/76) of the WB-positive captive animals and 98% (41/42) wild WB-positive animals also reacted against the peptide. In contrast, only 62% of the WB-positive sera reacted with the "V3" epitope and 46% with the gp130 C-terminal epitope.