Role of prophylactic azithromycin to reduce airway inflammation and mortality in a RSV mouse infection model

Abstract Background Respiratory syncytial virus (RSV) infection is an important cause of morbidity and mortality in vulnerable populations. Macrolides have received considerable attention for their anti‐inflammatory actions beyond their antibacterial effect. We hypothesize that prophylactic azithromycin will be effective in reducing the severity of RSV infection in a mouse model. Methods Four groups of BALB/c mice were studied for 8 days: Control (C), RSV‐infected (R), early prophylaxis with daily azithromycin from days 1 to 8, (E), and late prophylaxis with daily azithromycin from days 4 to 8 (L). Mice were infected with RSV on day 4, except for the control group. All groups were followed for a total of 8 days when bronchoalveolar lavage cell count and cytokines levels were measured. Mouse weight, histopathology, and mortality data were obtained. Results Prophylactic azithromycin significantly attenuated post‐viral weight loss between group R and both groups E and L ( P = 0.0236, 0.0179, respectively). IL‐6, IL‐5, and Interferon‐Gamma were significantly lower in group L ( P = 0.0294, 0.0131, and 0.0056, respectively) compared with group R. The total cell count was significantly lower for group L as compared with group R ( P < 0.05). Mortality was only observed in group R (8%). Lung histology in the prophylactic groups showed diminished inflammatory infiltrates and cellularity when compared with group R. Conclusion Prophylactic azithromycin effectively reduced weight loss, airway inflammation, cytokine levels and mortality in RSV‐infected mice. These results support the rationale for future clinical trials to evaluate the effects of prophylactic azithromycin for RSV infection.