Therapeutic effects of anti-B7-H3 monoclonal antibody in a murine model of neutrophilic asthma

Abstract

Objective To investigate the therapeutic effects of anti-B7-H3 blocking monoclonal antibody (McAb) in a murine model of neutrophilic asthma. Methods Twenty-four female BALB/c mice were randomly divided into four groups: PBS control group (group A), neutrophilic asthma group (group B), anti-B7-H3 McAb group (group C) and IgG isotype control group (group D). Those in group A were sensitized by injection of PBS and challenged with PBS through inhalation, while the other mice were sensitized by injection of ovalbumin (OVA) plus airway instillation of lipopolysaccharide (LPS), and then challenged with OVA. Moreover, mice in group C and group D were respectively injected with anti-B7-H3 McAb and IgG isotype control in the induction period. Each mouse′s performance was observed. Samples of bronchoalveolar lavage fluid (BALF) and lung tissues were collected. Total and differential cell counts in BALF were determined by using microscope. Levels of cytokines including IFN-γ, IL-4, IL-6, IL-17, tumor necrosis factor-α (TNF-α) and granulocyte colony stimulating factor (G-CSF) in BALF were measured by ELISA. Lung sections were stained with hematoxylin and eosin (HE) and periodic acid-Schiff (PAS) to identify tissue inflammation and mucus production, respectively. Immunohistochemistry was used to measure the expression of B7-H3 in frozen mouse lung sections. Results Mice in group B and group D showed asthmatic symptoms such as breathlessness, dysphoria and incontinence after nebulization, while these symptoms in group C were alleviated due to anti-B7-H3 McAb treatment. No abnormalities were observed in group A. Compared with group A, the other three groups showed increased total cell count in BALF and higher percentages of neutrophil and eosinophil (P<0.05). These three indicators in group C were lower than those in group B and group D (P<0.05). With regard to lung infiltration by Th1, Th2 and Th17 cells, the levels of IFN-γ, IL-4, IL-6, IL-17, TNF-α and G-CSF in BALF were increased in group B, group C and group D as compared with those in group A. Compared with group C, group B and group D showed higher levels of IL-6, TNF-α, IL-17 and G-CSF (P<0.05), but lower level of IL-4 (P<0.05). No statistical difference in the level of IFN-γ was observed among group B, group C and group D. Histological staining of lung sections showed that no obvious inflammatory cells and mucus secretion was observed in group A. Massive infiltration of inflammatory cells and neutrophils and mucus hypersecretion were detected in group B and group D. Treatment with anti-B7-H3 McAb inhibited the accumulation of neutrophils and mucus hypersecretion in lung tissues of group C. Compared with group A, levels of B7-H3-positive cells were significantly increased in group B and group D. Anti-B7-H3-treated mice showed reduced levels of B7-H3-positive cells in lung tissues as compared with those in group B and group D (P<0.05). Conclusion Treatment with anti-B7-H3 blocking McAb in an early stage can relieve the asthmatic syndrome, reduce airway inflammatory cells, inhibit mucus production and down-regulate Th17 cell-related cytokine secretion, which helps to alleviate airway and systematic inflammation in mice with NA, and partially inhibit the development of NA. Key words: Anti-B7-H3 McAb; Neutrophilic asthma; Murine model