Group B Streptococcal Serine-Rich Repeat Proteins Promote Interaction with Fibrinogen and Vaginal Colonization

Group B streptococcus (GBS) can cause severe disease in susceptible hosts, including newborns, pregnant women, and the elderly. GBS serine-rich repeat (Srr) surface glycoproteins are important adhesins/invasins in multiple host tissues, including the vagina. However, exact molecular mechanisms contributing to their im-portance in colonization are unknown. We have recently determined that Srr proteins contain a fibrinogen-binding region (BR) and hypothesize that Srr-mediated fibrinogen binding may contribute to GBS cervicova-ginal colonization. In this study, we observed that fibrinogen enhanced wild-type GBS attachment to cervical and vaginal epithelium, and that this was dependent on Srr1. Moreover, purified Srr1-BR peptide bound di-rectly to host cells, and peptide administration in vivo reduced GBS recovery from the vaginal tract. Further-more, a GBS mutant strain lacking only the Srr1 “latching ” domain exhibited decreased adherence in vitro and decreased persistence in a mouse model of GBS vaginal colonization, suggesting the importance of Srr–fibrin-ogen interactions in the female reproductive tract