Perinatal antibiotic treatment affects murine microbiota, immune responses and allergic asthma

Abstract

There is convincing evidence from recent human and animal studies that suggests the intestinal microbiota plays an important role in regulating immune responses associated with the development of allergic asthma, particularly during early infancy. Although identifying the mechanistic link between host-microbe interactions in the gut and lung mucosal tissues has proved challenging, several very recent studies are now providing significant insights. We have shown that administering vancomycin to mice early in life shifts resident gut flora and enhances future susceptibility to allergic asthma. This effect was not observed in mice given another antibiotic, streptomycin, nor when either antibiotic was administered to adult mice. In this addendum, we further analyze the link between early life administration of vancomycin and future susceptibility to asthma and describe how specific immune cell populations, which have been implicated in other asthma-related microbiota studies, are affected. We propose that shifts in gut microbiota exacerbate asthma-related immune responses when they occur shortly after birth and before weaning (perinatal period), and suggest that these effects may be mediated, at least in the case of vancomycin, by elevated serum IgE and reduced regulatory T cell populations.

Keywords: antibiotics; asthma; early life; gut; immune mechanisms; microbiota; perinatal programming.

Figure 1. Vancomycin treatment in early life but not exclusively in utero exacerbates allergic asthma. (A) Total cellular infiltrates from bronchoalveolar lavage (BAL) of control or vancomycin-treated mice challenged with ovalbumin (OVA) or PBS. (B) Eosinophil and (C) neutrophil numbers in the BAL quantified by cytospin. (D) Total pathological scores and representative hematoxylin and eosin stained lung sections. Scale bar, 300 μm. All assessments were made on day 26. The data are shown as means of 4−6 mice per group ± SEM. Statistics shown are based on comparisons to OVA-challenged controls. IU, in utero; PN, perinatal; LL, lifelong; Vanc, vancomycin; BALF, bronchoalveolar lavage fluid. *p < 0.05, **p < 0.01, n.d. = none detected.

Figure 2. Vancomycin treatment elevates steady-state serum IgE levels and enhances expression of surface-bound IgE on circulating basophils. (A) Serum IgE from naïve control or vancomycin-treated mice, as measured by ELISA. (B) Flow cytometric analysis of blood basophils from naïve control or vancomycin-treated mice. Basophils identified as CD3^-CD4^-CD8^-B220^-CD117^-FcεRIα⁺CD49b⁺ cells. (C) Surface-bound IgE levels on blood basophils from untreated control or vancomycin-treated mice, as determined by flow cytometry. (D) Representative histogram of surface-bound IgE on basophils from control and vancomycin-treated mice, as determined by flow cytometry. The data are shown as means of 4–5 mice per group ± SEM. Statistics shown are based on comparisons to untreated controls. PN, perinatal; LL, lifelong; Vanc, vancomycin. *p < 0.05, **p < 0.01.

Figure 3. Vancomycin treatment has no effect on Cxcl16 transcript levels. (A) Cxcl16 expression in colon and (B) lung tissue samples harvested from age matched naïve control and vancomycin-treated mice. The data are shown as means of 4−5 mice per group ± SEM. Statistics shown are based on comparisons to untreated controls. PN, perinatal; LL, lifelong; Vanc, vancomycin.

Figure 4. Perinatal vancomycin treatment reduces Treg accumulation in the colon. At 7 weeks of age, the percentage of CD25⁺Foxp3⁺ cells within the CD45⁺CD4⁺ cell population in the colon of naïve mice left untreated or treated with vancomycin was analyzed. The data shown are means of four mice per group ± SEM. Statistics shown are based on comparisons to untreated controls. PN, perinatal; LL, lifelong; Vanc, vancomycin. *p < 0.05.