Effect of respiratory syncytial virus infection on regulated on activation, normal T-cells expressed and secreted production in a murine model of asthma

Abstract

Purpose: Synthesis of regulated on activation, normal T-cells expressed and secreted (RANTES) in the airway has previously been shown to be elevated after respiratory syncytial virus (RSV) infection. However, since few studies have examined whether RSV-infected asthma patients express a higher level of RANTES than do normal individuals, we used a murine model of asthma to address this question.

Methods: We prepared Dermatophagoides farinae-sensitized mice as an asthma model, and then infected them with RSV and analyzed the changes in airway responsiveness and the cell populations and cytokine levels of bronchoalveolar lavage fluid.

Results: RANTES synthesis increased in response to RSV infection in both control mice and in asthma model (D. farinae) mice. However, there was no significant difference in the amount of RANTES produced following RSV infection between control and D. farinae mice. RSV infection affected neither interferon-γsynthesis nor airway responsiveness in either control or D. farinae mice.

Conclusion: RSV infection did not induce more RANTES in a murine model of asthma than in control mice.

Keywords: Animal models; Asthma; RANTES; Respiratory syncytial virus.

Fig. 1

Study design. Dermatophagoides farinae (Dermatophagoides farina, Df)-sensitized mice were immunized with Df plus alum by intraperitoneal injection (IP) once on days 1 and 14. Two weeks later, these mice were inoculated intranasally (IN) once daily with Df for 3 consecutive days (days 14 to 16). Df-sensitized mice were infected with respiratory syncytial virus (RSV) 24 hours after the final Df inoculation. Penh values and cytokine levels in bronchoalveolar lavage (BAL) fluid were measured 24 hours after RSV infection. IT, intratracheally.

Fig. 2

Confirmation of the murine model of asthma. (A) Penh values of the airway response to methacholine in the phosphate-buffered saline (PBS) and asthma (Dermatophagoides farina , Df) groups. (B) Differential cell counts in bronchoalveolar lavage (BAL) fluid collected from the murine model of asthma (Df) and control mice. (C) Cytokine levels in bronchoalveolar lavage (BAL) fluid collected from Df and PBS mice. The levels of interleukin (IL)-4, IL-5, and IL-13 were analyzed by enzyme-linked immunosorbent assay. Data shown represent the mean±SEM (n=6 per group). ^*P<0.05 vs. PBS.

Fig. 3

Respiratory syncytial virus (RSV)- and Dermatophagoides farinae-induced lung inflammation in a murine model of asthma. Lung tissue was removed at the time of the primary RSV inoculation or the final D. farinae injection and stained with hematoxylin and eosin (H&E). Representative photomicrographs from each group (n=6 per group) are shown as follows: (A) Phosphate-buffered saline (PBS) mice, (B) D. farinae mice, (C) PBS mice infected with RSV, (D) D. farinae mice infected with RSV (A-D, H&E, ×200).

Fig. 4

Confirmation of respiratory syncytial virus (RSV) infection in BALB/c mice. RSV N protein mRNA was amplified by reverse transcriptase polymerase chain reaction from the lung tissue of mice 1 day post-infection. PBS, phosphate-buffered saline; Df, Dermatophagoides farina.

Fig. 5

Regulated on activation, normal T-cells expressed and secreted (RANTES) expression in BALB/c mice. (A) RANTES mRNA was amplified by reverse transcriptase polymerase chain reaction (RT-PCR) of lung tissue harvested from uninfected and respiratory syncytial virus (RSV)-infected phosphate-buffered saline (PBS) mice and Dermatophagoides farina (Df) mice. (B) The concentration of RANTES in bronchoalveolar lavage fluid from uninfected and RSV-infected PBS and Df mice was analyzed by enzyme-linked immunosorbent assay. Data shown represent the mean±SEM (n=6 per group). ^*P<0.05 vs. PBS. ^†P<0.05 vs. Asthma.

Fig. 6

Interferon-γ (IFN-γ) expression, Penh values, and immune cell numbers. (A) IFN-γ levels in bronchoalveolar lavage (BAL) fluid from uninfected and respiratory syncytial virus (RSV)-infected phosphate-buffered saline (PBS) and Dermatophagoides farina (Df) mice. Levels of IFN-γ were analyzed by enzyme-linked immunosorbent assay. (B) Penh values of the airway response to methacholine in uninfected and RSV-infected PBS and Df mice. (C) Differential counts of eosinophils, neutrophils, lymphocytes, and macrophages in BAL from uninfected and RSV-infected PBS and Df mice. Data represent the mean±SEM of 5 independent experiments (n=6 per group). ^*P<0.05 vs. PBS mice. ^†P<0.05 vs. Df mice.