The invention relates to immunogenic polypeptides derived from epitopes in a Streptococcus agalactiae (“GBS”) protein GBS 80 and their use as prophylactic, diagnostic and therapeutic compositions. The invention also provides nucleic acids encoding the immunogenic polypeptides. Also provided are vectors useful for making such immunogenic polypeptides and host cells transformed with such vectors. In particular, the invention relates to a group immunogenic polypeptides derived from GBS 80. The compositions may include one or more of the immunogenic polypeptides either alone or with other antigenic components. For example, the immunogenic polypeptides may be combined with other GBS antigens to provide therapeutic compositions with broader range. In addition, the immunogenic polypeptides may also include flanking portions of the GBS 80 protein
