Early-Life Respiratory Syncytial Virus (RSV) Infection Triggers Immunological Changes in Gut-Associated Lymphoid Tissues in a Sex-Dependent Manner in Adulthood

Abstract

Severe respiratory syncytial virus (RSV) infection during early life has been linked to gut dysbiosis, which correlates with increased disease severity and a higher risk of developing asthma later in life. However, the impact of such early-life RSV infections on intestinal immunity in adulthood remains unclear. Herein, we show that RSV infection in 3-week-old mice induced persistent differential natural killer (NK) and T cell profiles within the lungs and gastrointestinal (GI) lymphoid tissues (GALT) in adulthood. Notably, male mice exhibited more pronounced RSV-induced changes in immune cell populations in both the lungs and GALT, while female mice displayed greater resilience. Importantly, early-life RSV infection was associated with the chronic downregulation of CD69-expressing T lymphocytes, particularly T regulatory cells in Peyer's patches, which could have a significant impact on T cell functionality and immune tolerance. We propose that RSV infection in early life is a trigger for the breakdown in immune tolerance at mucosal surfaces, with potential implications for airways allergic disease, food allergies, and other GI inflammatory diseases.

Keywords: Peyer’s patch; T cells; cecal patch; inflammation; respiratory syncytial virus.

Figure 1

Early-life RSV infection causes chronic immunological changes in the lungs of adult male mice. We employed flow cytometry to measure the absolute numbers of the following cell types in the lungs of 9-week-old mice: (A) CD4+ T cells, (B) CD69⁺ activated CD4⁺ T cells, (C) CD4⁺ regulatory T cells (Tregs), (D) CD8⁺ T cells, (E) CD69⁺ activated CD8⁺ T cells, (F) NK cells, (G) CD69⁺ activated NK cells, (H) NKT cells, and (I) CD69⁺ activated NKT cells. The analysis compared RSV-infected mice (n = 8 females, n = 7 males) with uninfected mice (n = 10 females, n = 8 males) using Student’s t-test, with statistical significance set at * p < 0.05 and ** p < 0.01.

Figure 2

Body weights and gastrointestinal tract analysis. (A) Changes in body weight from the day of RSV inoculation (3 weeks old) to the end of the experiment (9 weeks old). (B) Body weights measured at 9 weeks of age just before culling. Gastrointestinal (GI) anatomical analyses included: (C) lengths of the small intestine (SI), (D) lengths of the colon, (E) weights of the caecum, (F) number of Peyer’s patches, and (G) number of formed fecal pellets in the colon at the time of culling. Data were compared between RSV-infected (n = 8 females/group; n = 6 males/group) and uninfected (PBS) mice (n = 11 females/group; n = 8 males/group). Statistical significance was determined using Student’s t-test. ** p < 0.01.

Figure 3

Early-life RSV infection induces persistent differential immune profiles in the caecal patch of adult male mice. We employed flow cytometry to measure the absolute numbers of (A) CD4⁺ T cells, (B) CD69⁺ activated CD4⁺ T cells, (C) CD4⁺ regulatory T cells (Tregs), (D) CD8⁺ T cells, (E) CD69⁺ activated CD8⁺ T cells, (F) NK cells, (G) CD69⁺ activated NK cells, (H) NKT cells, and (I) CD69⁺ activated NKT cells in the cecal patch of 9 week old mice. We compared RSV-infected mice (n = 8 females; n = 7 males) to uninfected mice (n = 10 females; n = 8 males) using Student’s t-test. Statistical significance was indicated as * p < 0.05 and ** p < 0.01.

Figure 4

Early-life RSV infection induces persistent differential immune profiles in the Peyer’s patch of adult male mice. Flow cytometry was used to determine the absolute numbers of (A) CD4⁺ T cells, (B) CD69⁺ activated CD4⁺ T cells, (C) CD4⁺ regulatory T cells (Tregs), (D) CD8⁺ T cells, (E) CD69⁺ activated CD8⁺ T cells, (F) NK cells, (G) CD69⁺ activated NK cells, (H) NKT cells, and (I) CD69⁺ activated NKT cells in Peyer’s patches of 9-week-old RSV-infected (n = 8 females; n = 7 males) and uninfected mice (n = 10 females; n = 8 males). Student’s t-test analysis. * p < 0.05; ** p < 0.01.