Identification of an ideal adjuvant for receptor-binding domain-based subunit vaccines against Middle East respiratory syndrome coronavirus

Middle East respiratory syndrome （MERS）, an emerging infectious disease caused by MERS coronavirus （MERS-CoV）, has garnered worldwide attention as a consequence of its continuous spread and pandemic potential, making the development of effective vaccines a high priority. We previously demonstrated that residues 377-588 of MERS-CoV spike （S） protein receptor-binding domain （RBD） is a very promising MERS subunit vaccine candidate, capable of inducing potent neutralization antibody responses. In this study, we sought to identify an adjuvant that optimally enhanced the immunogenicity of S377-588 protein fused with Fc of human IgG （S377-588-Fc）. Specifically, we compared several commercially available adjuvants, including Freund＇s adjuvant, aluminum, Monophosphoryl lipid A, Montanide ISA51 and MF59 with regard to their capacity to enhance the immunogenicity of this subunit vaccine. In the absence of adjuvant, S377-588-Fc alone induced readily detectable neutralizing antibody and T-cell responses in immunized mice. However, incorporating an adjuvant improved its immunogenicity. Particularly, among the aforementioned adjuvants evaluated, MF59 is the most potent as judged by its superior ability to induce the highest titers of IgG, IgG1 and IgG2a subtypes, and neutralizing antibodies. The addition of MF59 significantly augmented the immunogenicity of S377-588-Fcto induce strong IgG and neutralizing antibody responses as well as protection against MERS-CoV infection in mice, suggesting that MF59 is an optimal adjuvant for MERS-CoV RBD-based subunit vaccines.

Cardioprotection Afforded by Norepinephrine-mediated Postconditioning in Isolated Rat Hearts

Objectives Previous studies have demonstrated that endogenous norepinephrine （NE） plays an important role in the mediation of ischemic preconditioning. The present study is designed to determine whether NE is also involved in mediation of the protective effects of postconditioning. Methods The rat hearts were rapidly excised under anesthesia and attached to a Langendorff apparatus via the aorta for retrograde perfusion with Krebs-Henseleit buffer solution. All hearts were subjected to 30 min of left coronary artery occlusion followed by 60 min of reperfusion, except the control group. Animals were randomly divided into 5 groups as follows： （1） control group, the hearts were underwent same procedures without ischemic insult ; （2） ischemia reperfusion group, the left coronary artery was occluded for 30 rain and followed by 60 min of reperfusion ; （3） ischemic postconditioning （IPost） group, immediately at the onset of reperfusion, the heart was initiated with 1 min of full coronary flow, followed by 1 min of re-occlusion, repeated for a total of three cycles; （4） IPost plus prazosin group, the heart was perfused with prazosin for 10 min before ischemia; （5） IPost plus reserpine group, a single dose of reserpine was administered by i.m. injection, 24 hours before the experiment. Coronary flow was measured by timed collection of coronary effluent and sample of coronary effluent at 5 min of reperfusion were collected for the measurement of creatine kinase （CK）. Infarct size and risk area were determined at the end of experiments. Results 30 min of ischemia and followed by 60 rain of reperfusion caused a significant decrease in cardiac function and a significant increase in CK release and infarct size. Postconditioning with three cycles of 1-min ischemia and 1-min reperfusion markedly improved cardiac function and reduced CK release and infarct size. However, the cardioprotection afforded by postconditioning was abolished by prazosin （10^-6M） , a selective α adrenergic receptor antagonist, or by pretreatment with reserpine （0. 45 mg·kg^-1 ）, which significantly reduced NE level in both plasma and coronary effluent. Conclusions These results suggest that the protective effects of ischemic postconditioning are related to stimulation of endogenous NE release in rat hearts.