Figure 1: (a) Alignment of the amino acid sequences of the MPER of p15E of FeLV, PERV and KoRV and gp41 of HIV-1, identical amino acids are bold. (b) Schematic presentation of the antigens used in this study. Amino acid sequences derived from p15E of KoRV (DQ174772) are shown in white boxes and amino acid sequences derived from gp41 of HIV-1 (AF324493) are shown in grey boxes. Numbering below the drawings refers only to the amino acid sequence of gp41. The drawings are not in scale. FP–fusion peptide, FPPR–fusion peptide proximal region, MPER– membrane proximal external region, MSD–membrane spanning domain.