Highly pathogenic coronavirus N protein aggravates lung injury by MASP-2-mediated complement over-activation

Ting Gao; Mingdong Hu; Xiaopeng Zhang; Hongzhen Li; Lin Zhu; Hainan Liu; Qincai Dong; Zhang Zhang; Zhongyi Wang; Yong Hu; Yangbo Fu; Yanwen Jin; Kaitong Li; Songtao Zhao; Yongjiu Xiao; Shuping Luo; Lufeng Li; Lingfang Zhao; Junli Liu; Huailong Zhao; Yue Liu; Weihong Yang; Jing Peng; Xiaoyu Chen; Ping Li; Yaoning Liu; Yonghong Xie; Jibo Song; Lu Zhang; Qingjun Ma; Xiuwu Bian; Wei Chen; Xuan Liu; Qing Mao; Cheng Cao

Persistent activation of complement leads to uncontrolled inflammation. To investigate the effect of N protein-potentiated MASP-2 activation on inflammation, mice were pre-infected with adenovirus (1×10 9 PFU) expressing SARS-CoV N (Ad-SARS N) or its mutant or adenovirus vehicle only (Ad-null). The mice were then challenged with LPS, which contains 20 MBL-binding motifs, to activate LP and induce inflammation (30) . 8 of 10 mice pre-exposed to adenovirus vehicle survived when challenged with 5 mg/kg LPS (Fig. 3A) , while all 10 mice pre-exposed to Ad-SARS N died within 12 hr after LPS administration at the same dosage (Fig. 3A ). Severe lung damage and massive inflammatory cell infiltration were also observed in dead mice (Fig. 3B ). In concert with previous findings, the pre-infection of Ad-229E N and Ad-SARS 25 N bearing the 116-124 or 321-323 deletion in the N protein, respectively, had significantly reduced effects on mouse mortality. Importantly, when anti-N, anti-MASP-2 antibody or C1INH was administered simultaneously with LPS administration in the Ad-SARS N pre-infected mice, both death rate and lung tissue inflammation induced by LPS were significantly reduced ( Fig. 3A and 3B). These results collectively demonstrate that the SARS-CoV N protein greatly potentiated 30 LPS-induced inflammation via MASP-2 activation, which thereby initiates LP-involved complement cascade activation.