# The natural history of C. trachomatis urethral infections in men who have sex with women

> **NIH NIH R01** · INDIANA UNIVERSITY INDIANAPOLIS · 2024 · $792,498

## Abstract

ABSTRACT
Chlamydia trachomatis (CT) is the most common bacterial sexually transmitted infection (STI) worldwide and
causes irreversible reproductive tract damage in women. As most CT-infected women have no symptoms and
are unaware that they are infected, the CDC recommends annual CT screening in women aged <25 and high
risk women to detect and treat asymptomatic infections and prevent complications; in men, routine screening is
not recommended. Despite 3 decades of screening programs, CT rates in the U.S. have dramatically increased,
driven primarily by increasing CT reinfections. As most CT-infected women are heterosexual and routine
screening in men is not recommended, undetected CT infections in men are the reservoir that propels
reinfections in women. To curb the CT epidemic, it is critical that we understand whether men can develop
immunity to CT and identify factors that promote CT reinfections (e.g., asymptomatic men who shed significant
CT organisms). Approximately 1/3 of men who present for treatment as a CT contact (i.e., their sex partner was
confirmed to be CT-infected) are uninfected, suggesting that these men either cleared CT infection by immune-
mediated mechanisms or have a urethral microbiome that resists CT acquisition. To prevent CT reinfections in
women, this proposal focuses on male contacts to CT-infected women and will study if CT infection is associated
with specific microbiome compositions, comorbid STIs, or adaptive T-cell and antibody immunity. To do this, we
will enroll up to 400 male CT-contacts, collect blood and urine specimens, treat them with the CDC-recommend
first-line antibiotic, and ask them to return for a 1-month test of cure (TOC) visit (Aim 1). To study if CT uninfected
contacts to CT have long-lasting immunity and how the urethral microbiome and immune system change over
time, we will re-enroll 100 men for a 6-month longitudinal study to collect weekly urine specimens and
symptom/sexual behavior diaries and blood and urine specimens at 3-month and 6-month screening visits.
Weekly urine specimens will be stored and tested at study completion to create a natural history study. By
studying the rates of incident CT infection over time, we will be able to elucidate if resistance to CT infection,
defined in Aim 1, correlates with (1) increased rate of natural clearance between visits; (2) decrease in incident
CT infection at 3- or 6-months; (3) decrease in incident CT infection organism load; and (4) decrease in the rate
of homologous CT genovars. Study findings will inform novel approaches to preventing transmission from men
to women and help curb rising CT rates and complications.

## Key facts

- **NIH application ID:** 10880559
- **Project number:** 5R01AI177002-02
- **Recipient organization:** INDIANA UNIVERSITY INDIANAPOLIS
- **Principal Investigator:** Stephen J. Jordan
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2024
- **Award amount:** $792,498
- **Award type:** 5
- **Project period:** 2023-07-05 → 2028-06-30

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10880559

## Citation

> US National Institutes of Health, RePORTER application 10880559, The natural history of C. trachomatis urethral infections in men who have sex with women (5R01AI177002-02). Retrieved via AI Analytics 2026-05-26 from https://api.ai-analytics.org/grant/nih/10880559. Licensed CC0.

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