During bacterial infection, the host produces numerous factors that limit metals at the site of infection in a process termed nutritional immunity. The goal of this proposal is to identify mechanisms utilized by Group B Streptococcus (GBS) to evade nutritional immunity in order to persist within the vaginal mucosa and cause intrauterine infection. GBS asymptomatically colonizes the vaginal tract of 25-30% of healthy women but can ascend and preterm labor or birth, miscarriage, or stillbirth. Intrauterine infection leads to massive neutrophil influx and inflammation, where 50% of the cytoplasm of infiltrating neutrophils is calprotectin, a protein complex that upon release sequesters metal ions. During infection, GBS encounters high concentrations of calprotectin and must be able to overcome this stress, but the interaction of GBS with host calprotectin remains unknown. Our preliminary data show that calprotectin can inhibit GBS growth and studies utilizing a newly constructed saturated GBS transposon (Tn) sequencing mutant library revealed significantly underrepresented mutants in zinc transport systems following calprotectin exposure. We hypothesize that zinc transport machinery is important for GBS survival during calprotectin stress, and further that calprotectin may serve as a pro-inflammatory effector molecule, acting to compromise barrier function during GBS infection. This proposal seeks to elucidate the molecular mechanisms by which GBS overcomes calprotectin-mediated nutritional immunity in the female reproductive tract, and the role of calprotectin in ascending infection. These questions will be addressed with both in vitro and in vivo models of GBS vaginal colonization and ascending infection in the following specific aims:
AIM 1 : Characterize and identify the molecular determinants utilized by GBS to combat nutritional immunity during vaginal colonization;
AIM 2 : Determine the role of calprotectin as a modulator of reproductive tract inflammation and barrier integrity during GBS infection. These studies are the first to examine GBS metal homeostasis and the pro-inflammatory effects of calprotectin during GBS vaginal colonization, which will provide fundamental insights toward our understanding of GBS mucosal persistence and transmission to the vulnerable newborn. from the vagina into the uterus and invade the amniotic cavity, leading to inflammation, tissue damage, adverse pregnancy outcomes, including
Group B Streptococcus (GBS) is an opportunistic pathogen that colonizes the female reproductive tract; however, during pregnancy GBS can ascend to cause intrauterine infection, increasing risk for adverse pregnancy outcomes like preterm labor/birth or stillbirth. Nutritional immunity is a host defense mechanism used to starve invading pathogens by limiting available metal ions. The mechanisms used by GBS to overcome metal limitation by the key mediator calprotectin remain unknown. This proposal seeks to investigate the effects of nutritional immunity and calprotectin on GBS colonization and infection.
