Fusion proteins comprising an immunogenic polypeptide are disclosed. The immunogenic polypeptide consists of the amino acid sequence motif Xaa-Thr-Xaa-Val-Thr-Gly-Gly-Xaa-Ala-Ala-Arg-Thr-Thr-Xaa-Gly-Xaa-Xaa-Ser-L- eu-Phe-Xaa-Xaa-Gly-Xaa-Ser-Gln-Xaa-Ile-Gln-Leu-Ile (SEQ ID NO:8). Also disclosed are immunogenic compositions comprising a pharmaceutically acceptable carrier and the fusion protein.