# The Characterization of Streptococcus agalactiae Novel Protein, Sak_1753, in the Colonization of the Vaginal Tract

> **NIH NIH F31** · STATE UNIVERSITY OF NY,BINGHAMTON · 2020 · $30,720

## Abstract

PROJECT SUMMARY
Streptococcus agalactiae (Group B Strep, GBS) infections in neonates are often fatal and are strongly associated with
maternal GBS vaginal colonization. The use of preventive intrapartum antibiotics, while effective against early onset disease,
have their own pitfalls and have no effect on late onset neonatal GBS diseases. As such, a more long-term strategy is
required to control infections by GBS. This proposal focuses on a novel GBS protein, Sak_1753, and we aim to determine
its role in GBS vaginal colonization and its eligibility as a protein-based vaccine candidate. sak_1753 was previously
identified as the most highly upregulated gene (~3000 fold) in the GBS A909 transcriptome when comparing vaginal
colonization to growth in liquid culture. Sak_1753 is regulated directly by a two-component system SaeRS and has no
known homologs outside streptococci or predicted protein domains, leaving its function a mystery. The protein is conserved
among all sequenced strains of GBS and is made up of multiple repeat domains with the number of repeats differing between
strains. We will characterize Sak_1753 regulation and localization and determine its role in vaginal colonization. We have
created knockout (KO; Δsak_1753::Spec) and over-expression (OE; PrecA-sak_1753) strains in a wildtype (WT) GBS A909
background. Preliminary adherence assays with human vaginal epithelial cells (VK2) demonstrated that the OE strains were
able to bind to epithelial cells significantly more than WT and the KO bound significantly less. Sak_1753 also showed binding
specificity to collagen 1 and fibrinogen. In addition, the sak_1753 KO strain exhibited significant decreased vaginal
colonization in a murine model. Initial immunofluorescence microscopy indicates that Sak_1753 is found on the cell surface,
indicating a possible adhesive role of this protein. In this proposal we will further characterize the role of Sak_1753. GBS
strains will be created to contain truncations of Sak_1753 in an effort to identify the role of the repeated domains in host
attachment. Strains expressing truncated proteins will be tested in adhesion assays with VK2 cells and in vivo murine
colonization. To further ascertain the cellular localization of Sak_1753 western blot techniques and immunofluorescence
microscopy will be used. The success of this research will contribute to the strategies for reduction of GBS adhesion to
vaginal tissue and hence a reduction in GBS-related neonatal diseases and deaths.

## Key facts

- **NIH application ID:** 10067977
- **Project number:** 1F31AI154817-01
- **Recipient organization:** STATE UNIVERSITY OF NY,BINGHAMTON
- **Principal Investigator:** Lamar S Thomas
- **Activity code:** F31 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $30,720
- **Award type:** 1
- **Project period:** 2020-07-01 → 2024-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10067977

## Citation

> US National Institutes of Health, RePORTER application 10067977, The Characterization of Streptococcus agalactiae Novel Protein, Sak_1753, in the Colonization of the Vaginal Tract (1F31AI154817-01). Retrieved via AI Analytics 2026-05-23 from https://api.ai-analytics.org/grant/nih/10067977. Licensed CC0.

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