Yuting Jiang

The pathogenesis of highly pathogenic Middle East respiratory syndrome coronavirus (MERS-CoV) remains poorly understood. In a previous study, we established an hDPP4-transgenic (hDPP4-Tg) mouse model in which MERS-CoV infection causes severe acute respiratory failure and high mortality accompanied by an elevated secretion of cytokines and chemokines. Since excessive complement activation is an important factor that contributes to acute lung injury after viral infection, in this study, we investigated the role of complement in MERS-CoV-induced lung damage. Our study showed that complement was excessively activated in MERS-CoV-infected hDPP4-Tg mice through observations of increased concentrations of the C5a and C5b-9 complement activation products in sera and lung tissues, respectively. Interestingly, blocking C5a production by targeting its receptor, C5aR, alleviated lung and spleen tissue damage and reduced inflammatory responses. More importantly, anti-C5aR antibody treatment led to decreased viral replication in lung tissues. Furthermore, compared with the sham treatment control, apoptosis of splenic cells was less pronounced in the splenic white pulp of treated mice, and greater number of proliferating splenic cells, particularly in the red pulp, was observed. These data indicate that (1) dysregulated host immune responses contribute to the severe outcome of MERS; (2) excessive complement activation, triggered by MERS-CoV infection, promote such dysregulation; and (3) blockade of the C5a-C5aR axis lead to the decreased tissue damage induced by MERS-CoV infection, as manifested by reduced apoptosis and T cell regeneration in the spleen. Therefore, the results of this study suggest a new strategy for clinical intervention and adjunctive treatment in MERS-CoV cases.

BACKGROUND: Melatonin is an amine hormone that plays an important role in regulating mammalian reproduction. This study aimed to investigate the expression pattern of melatonin synthesis enzymes AANAT and HIOMT and melatonin receptors MT1 and MT2 in sheep cumulus-oocyte complexes (COCs) as well as the change of melatonin level in follicular fluid (FF) during antral follicle development. In this research, we also study the effect of β-estradiol (E2) on MT1 and MT2 expression as well as melatonin synthesis in COCs so as to lay the foundation for further exploration of the regulation mechanism of melatonin synthesis in the ovary. METHODS: COCs and FF were collected from different size (large follicles (diameter ≥ 5 mm), medium follicles (diameter 2-5 mm), and small follicles (diameter ≤ 2 mm)) of antral follicles in sheep ovaries. To assess whether E2 regulates melatonin synthase and its receptors expression in sheep COCs and whether it is mediated through estrogen receptor (ER) pathway. The collected COCs were cultured in vitro for 24 h and then treat with 1 μM E2 and/or 1 μM ICI182780 (non-selective ER antagonist). The expression of AANAT, HIOMT, MT1 and MT2 mRNA and protein were determined by qRT-PCR and western blot. The melatonin level was determined by ELISA. RESULTS: The expression of AANAT, HIOMT, MT1 and MT2 were significantly higher expression in the COCs of small follicles than in those of large follicles (P < 0.05). However, the melatonin level was significantly higher in large follicle FF than in small follicle FF (P < 0.05). Further, the expression of AANAT, HIOMT, MT1, and MT2 and melatonin production were decreased by E2 treatment (P < 0.05), but when ICI182780 was added, the expression of AANAT, HIOMT, MT1, and MT2 and melatonin production recovered (P < 0.05). CONCLUSIONS: We suggest that sheep COCs can synthesize melatonin, but this ability is decreased with increasing follicle diameter. Furthermore, E2 play an important role in regulated the expression of MT1 and MT2 as well as melatonin synthesis in sheep COCs through the ER pathway.

The Middle East Respiratory Syndrome Coronavirus (MERS-CoV) causes severe acute respiratory failure and considerable extrapumonary organ dysfuction with substantial high mortality. For the limited number of autopsy reports, small animal models are urgently needed to study the mechanisms of MERS-CoV infection and pathogenesis of the disease and to evaluate the efficacy of therapeutics against MERS-CoV infection. In this study, we developed a transgenic mouse model globally expressing codon-optimized human dipeptidyl peptidase 4 (hDPP4), the receptor for MERS-CoV. After intranasal inoculation with MERS-CoV, the mice rapidly developed severe pneumonia and multi-organ damage, with viral replication being detected in the lungs on day 5 and in the lungs, kidneys and brains on day 9 post-infection. In addition, the mice exhibited systemic inflammation with mild to severe pneumonia accompanied by the injury of liver, kidney and spleen with neutrophil and macrophage infiltration. Importantly, the mice exhibited symptoms of paralysis with high viral burden and viral positive neurons on day 9. Taken together, this study characterizes the tropism of MERS-CoV upon infection. Importantly, this hDPP4-expressing transgenic mouse model will be applicable for studying the pathogenesis of MERS-CoV infection and investigating the efficacy of vaccines and antiviral agents designed to combat MERS-CoV infection.