Respiratory virus-induced regulation of asthma-like responses in mice depends upon CD8 T cells and interferon-gamma production

Abstract

Respiratory virus infections can significantly influence the development of airway disease by both predisposing and exacerbating the developing lung immune environment. In contrast, the initiation of a more desirable anti-viral response may better prepare the local environment and protect it from developing an adverse long-term disease phenotype. BALB/c or C57BL/6 mice exposed to respiratory syncytial virus (RSV) infection at the same time as allergen sensitization were assessed for airway function, cytokine responses, and inflammatory parameters. Depending on the genetic strain of mouse used, BALB/c versus C57BL/6, RSV could differentially protect against the development of airway allergen responses. Although RSV was able to block allergen sensitization and induction of airway hyperresponsiveness and eosinophilic inflammation in C57BL/6 mice, the infection did not reduce the allergic responses in BALB/c mice. The alteration of airway responsiveness did not depend on the timing of RSV infection in C57BL/6 mice in conjunction to the allergen sensitization protocol. Neutralization experiments demonstrated that interferon-gamma contributed significantly to the RSV-induced airway attenuation of the allergic responses, whereas transfer of CD8 T cells from RSV-infected animals suggested that they were partially responsible for the altered environment. These data suggest that a respiratory viral infection impacts on the local lung environment and may reflect specific aspects of the hygiene hypothesis. However, the outcome of this interaction depends on the immunological response of the host.

Figure 1

RSV infection and allergen sensitization and challenge in C57BL/6 and BALB/c mice. C57BL/6 and BALB/c mice were RSV infected (RSV), allergen sensitized (CRA), or RSV infected and allergen sensitized (CRA + RSV). A: Airway responses were measured after one dose of methacholine and compared to basal measurements. B: Lung lavage was performed, and eosinophils were counted in stained cytospin slides. C: Lung lymph node cells were restimulated with allergen, and cytokines were measured in culture supernatants 24 hours after challenge. Data are represented as mean airway resistance in cmH₂O/ml/second, number of cells, or ng/ml ± SEM, respectively. *P < 0.01 compared to RSV-infected control mice, ^#P < 0.05 compared to CRA-sensitized mice, n = 5 mice.

Figure 2

Timing of RSV infection and CRA sensitization and challenge. A: C57BL/6 mice were RSV infected (RSV), allergen sensitized (CRA), or RSV infected and allergen sensitized (CRA + RSV) at different time intervals. B: Airway responses were measured after one dose of methacholine and compared to basal measurements. Data are represented as mean airway resistance in cmH₂O/ml/second, number of cells, or ng/ml ± SEM, respectively. *P < 0.01 compared to RSV-infected control mice, ^#P < 0.05 compared to CRA-sensitized mice, n = 5 mice.

Figure 3

Influence of IFN-γ on RSV-mediated changes on allergen sensitization and challenge. C57BL/6 mice were RSV infected (RSV); allergen sensitized (CRA); allergen sensitized and anti-IFN-γ treated (CRA + anti-IFN-γ); RSV infected and allergen sensitized (CRA + RSV); or RSV infected, allergen sensitized, and anti-IFN-γ treated (CRA + RSV + anti-IFN-γ). A: Airway responses were measured after one dose of methacholine and compared to basal measurements. B: Lung lavage was performed, and eosinophils were counted in stained cytospin slides. C: Lung lymph node cells were restimulated with allergen, and cytokines were measured in culture supernatants after 24 hours. Data are represented as mean airway resistance in cmH₂O/ml/second, number of cells, or ng/ml ± SEM, respectively. *P < 0.01 compared to RSV-infected control mice, ^#P < 0.05 compared to CRA-sensitized mice, ^αP < 0.05 compared to CRA + RSV-sensitized mice, n = 5 mice.

Figure 4

Influence of IFN-γ on RSV-mediated changes on allergen-induced airway inflammation. C57BL/6 mice were RSV infected (RSV); CRA sensitized (CRA); CRA sensitized and anti-IFN-γ treated (CRA + anti-IFN-γ); RSV infected and CRA sensitized (CRA + RSV); or RSV infected, CRA sensitized, and anti-IFN-γ treated (CRA + RSV + anti-IFN-γ). Lungs were isolated and processed, and sections were stained with H&E. Shown are representative lung sections. Arrows indicate eosinophils. Original magnifications: ×200 (A); ×400 (B).

Figure 5

CD4 and CD8 T cells from RSV-infected mice mediate changes on allergen sensitization and challenge. C57BL/6 mice were RSV infected, and CD4 or CD8 T cells were isolated from lung lymph nodes. A: CRA-sensitized mice were injected by tail vein intravenously with vehicle alone (CRA), CD4 T cells (CRA + CD4⁺), or CD8 T cells (CRA + CD8+). B: Airway responses were measured after one dose of methacholine and compared to basal measurements. C: Lung lymph node cells were restimulated with CRA, and cytokines were measured in culture supernatants after 24 hours. Data are represented as mean airway resistance in cmH₂O/ml/second or ng/ml ± SEM, respectively. *P < 0.01 compared to RSV-infected control mice, ^#P < 0.05 compared to CRA-sensitized mice, n = 5 mice.