Foal enteral immunization with live bacteria reprograms innate immune cells

This is an amazing piece of research where exposing newborn foals with oral (via stomach tube) rhodococcus organisms results in immunity to the nasal exposure to the same organism, the cause of Foal Pneumonia. An interesting thought occurs to me about the propensity of foals to eat adult horse feces, a form of “pica”. Herbivore stoola are the common source of ground contamination with rhodococcus organisms. Perhaps the pica contributes to foal’s immunity to rhodococcus.
DrO

Enteral immunization with live bacteria reprograms innate immune cells and protects neonatal foals from pneumonia
Sci Rep. 2025 May 25;15(1):18156. doi: 10.1038/s41598-025-02060-5.
Authors
Bibiana Petri da Silveira 1 , Susanne K Kahn 1 , Rebecca M Legere 1 , Jocelyne M Bray 1 , Hannah M Cole-Pfeiffer 1 , Michael C Golding 2 , Noah D Cohen 1 , Angela I Bordin 3
Affiliations

1 Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, USA.
2 Department of Veterinary Physiology and Pharmacology, Texas A&M University, College Station, TX, 77843, USA.
3 Equine Infectious Disease Laboratory, Department of Large Animal Clinical Sciences, Texas A&M University, College Station, TX, USA. abordin@tamu.edu.

PMID: 40415003
DOI: 10.1038/s41598-025-02060-5

Abstract

Using a horse foal model, we show that enteral immunization of newborn foals with Rhodococcus equi overcomes neonatal vaccination challenges by reprogramming innate immune responses, inducing R. equi-specific adaptive humoral and cell-mediated immune responses and protecting foals against experimental pneumonia challenge. Foals were immunized twice via gavage of R. equi (immunized group) or saline (control group) at ages 1 and 3 days. At age 28 days, all foals were challenged intrabronchially with R. equi. Post-challenge, all 5 immunized foals remained healthy, whereas 67% (4/6) of control foals developed clinical pneumonia. Immunized foals exhibit changes in the epigenetic profile of blood monocytes, > 1,000 differentially-expressed genes in neutrophils, higher concentrations of R. equi-specific IgG1 and IgG4/7, and a higher number of IFN-γ producing lymphocytes in response to R. equi stimulation indicating T helper type 1 response compared to control foals. Together, our data indicate that early life exposure to R. equi in the gastrointestinal tract can modulate innate immune responses, generate specific antibodies and cell-mediated immunity, and protect against pneumonia.

Keywords: Rhodococcus equi; Horse; Infection; Trained Immunity; Vaccine.

© 2025. The Author(s).