# RSV-induced type 2 immune responses are inhibited by dietary citrulline supplementation during gestation and early life

> **NIH NIH U19** · VANDERBILT UNIVERSITY MEDICAL CENTER · 2021 · $550,563

## Abstract

In the last funding cycle of this AADCRC, Project 1 (Dr. Hartert – Leader) found that increased blood levels of
L-citrulline (L-CIT) were significantly associated with decreased odds of infant bronchiolitis (odds ratio (OR)
0.68, 95% confidence interval (CI) 0.48-0.95). These data suggest that higher blood levels of L-CIT at time of
birth protected against infant bronchiolitis and may prevent development of asthma later in childhood. We
therefore hypothesize that compared to regular diet (RD), an L-CIT supplemented diet (L-CITsd) fed to
parents during gestation and their offspring prevents severe RSV bronchiolitis in the offspring. Our
preliminary data reveal that the L-CITsd decreased RSV-induced lung IL-13 expression, reduced the frequency
of lung IL-13 expression by ILC2, and restrained airways responsiveness. Further, L-CITsd significantly
decreased ILC2 expression of IL-13 when the cells were stimulated ex vivo with IL-33, and L-CIT added to
ILC2 culture inhibited IL-33-induced IL-13 production. Elevated levels of ILC2, IL-33, and IL-13 are associated
with severe RSV infection in infancy. These finding are important because males have a greater risk of severe
RSV-induced disease; therefore, L-CITsd provides a possible benefit to the sex most likely to have severe
RSV bronchiolitis. Importantly, these protective effects of L-CITsd did not come at a cost of worsening
adversely affecting lung anti-viral immunity to RSV. L-CIT is currently not present in prenatal vitamins and the
major sources of citrulline (watermelon) is not commonly introduced into the diets of infants until after six
months of life, a time after which children are at greatest risk for RSV bronchiolitis. Aim 1 is to determine the
mechanism by which L-citrulline dietary supplementation inhibits RSV-induced type 2 immunopathology. In
this aim, we will determine: a) the effect of L-CITsd on IL-33-driven ILC2 cytokine production and
immunopathology, b) the protective effect of L-CITsd on ILC2 epigenetic regulation, c) the durability of the
protection of L-CITsd during the first infection to subsequent infection, and d) the ability of L-CITsd to inhibit
human lung ILC2 function and proliferation. Aim 2 is to define the effect of L-CIT on airway epithelial function
in response to RSV infection. In this aim, we will determine: a) the ability of L-CITsd to inhibit RSV-induced
ROS generation in mice, and b) the effect of L-CIT on ROS generation, cytokine/chemokine production, and
membrane barrier function by primary nasal airway epithelial cells obtained from the INSPIRE cohort.
Project 2 is also highly innovative because it will be the first to: 1) determine the role of L-CITsd in decreasing
RSV-induced immunopathology, 2) define the effect of L-CITsd on ILC2 epigenetic regulation, 3) determine
how L-CITsd regulates epithelial cell function in vivo in the setting of respiratory viral infection, and 4) use
primary airway epithelial cells from infants to determine the effect of L-CIT o...

## Key facts

- **NIH application ID:** 10262871
- **Project number:** 2U19AI095227-12
- **Recipient organization:** VANDERBILT UNIVERSITY MEDICAL CENTER
- **Principal Investigator:** Ray Stokes Peebles
- **Activity code:** U19 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2021
- **Award amount:** $550,563
- **Award type:** 2
- **Project period:** 2011-08-04 → 2026-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/10262871

## Citation

> US National Institutes of Health, RePORTER application 10262871, RSV-induced type 2 immune responses are inhibited by dietary citrulline supplementation during gestation and early life (2U19AI095227-12). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/10262871. Licensed CC0.

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