# Bacterial CRISPR interference to define macrophage responses to group B Streptococcus proteins

> **NIH NIH R21** · UNIVERSITY OF PITTSBURGH AT PITTSBURGH · 2024 · $198,413

## Abstract

Project Summary
Group B Streptococcus (GBS) is a major cause of intrauterine infections in the United States and around the
world. These infections commonly lead to serious adverse pregnancy outcomes including stillbirth, preterm
labor, neonatal sepsis, and systemic maternal disease, which can be life-threatening. One reason that GBS is
such a common etiology of serious intrauterine infection is that—among bacterial vaginal colonizers—it has
exceptional abilities to suppress and evade fetal and maternal innate immune surveillance that is highly
effective at clearing other microbes from the intrauterine cavity. Macrophages are key effectors of maternofetal
innate immunity, and serve important roles in maintaining gestational health, yet can fail to eliminate GBS from
pregnancy tissues, setting the stage for serious complications. The goal of this proposal is to examine, in
detail, molecular interactions between macrophages and GBS cells to discover basic mechanisms of
GBS evasion and suppression of gestational macrophage signaling and bacterial killing. We will use
novel CRISPR/Cas-based bacterial gene suppression techniques to systematically test GBS strains from
knockdown libraries that are deficient in specific, highly conserved, surface trafficked proteins. These strains
with specific externalized protein defects will be coincubated with ex vivo human placental macrophages, both
maternal and fetal-derived, to examine their effects on macrophage cytokine expression, phagocytosis, and
microbial killing. We will use these screens to identify novel GBS surface trafficked proteins with significant
effects on placental macrophage immunophenotypes. Discoveries from these screens, including several
already made in preliminary experiments, will inform generation of targeted gene deletion GBS mutants. These
mutants and appropriate complemented controls will then be used to characterize effects on placental
macrophages in detail, through multiplex cytokine profiling, single-cell transcriptomics, immunofluorescent
confocal microscopy, and examination of in vivo outcomes from a clinically relevant mouse model of GBS
intrauterine infection. Our two proposed aims will use innovative, multimodal approaches to identify GBS
externalized protein targets for new vaccines or therapeutics for prevention and early treatment of dangerous
intrauterine infections.

## Key facts

- **NIH application ID:** 10841635
- **Project number:** 5R21AI178067-02
- **Recipient organization:** UNIVERSITY OF PITTSBURGH AT PITTSBURGH
- **Principal Investigator:** David M Aronoff
- **Activity code:** R21 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $198,413
- **Award type:** 5
- **Project period:** 2023-05-15 → 2025-04-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10841635

## Citation

> US National Institutes of Health, RePORTER application 10841635, Bacterial CRISPR interference to define macrophage responses to group B Streptococcus proteins (5R21AI178067-02). Retrieved via AI Analytics 2026-05-28 from https://api.ai-analytics.org/grant/nih/10841635. Licensed CC0.

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