Mutations and transient conformational movements of receptor binding domain (RBD) that make neutralizing epitopes momentarily unavailable, present immune escape routes to SARS-CoV-2. To mitigate viral escape, we developed a cocktail of neutralizing antibodies (NAbs) targeting epitopes located on different domains of spike (S) protein. Screening of a library of monoclonal antibodies generated from peripheral blood mononuclear cells of COVID-19 convalescent patients yielded potent NAbs, targeting N-terminal domain (NTD) and RBD domain of S, effective at nM concentrations. Remarkably, combination of RBD-targeting NAbs and NTD-binding NAb, FC05, dramatically enhanced the neutralization potency in cell-based assays and animal model. Results of competitive SPR assays and cryo-EM structures of Fabs bound to S unveil determinants of immunogenicity. Combinations of immunogens, identified in NTD and RBD of S, when immunized in rabbits elicited potent protective immune responses against SARS-CoV-2. These results provide a proof-of-concept for neutralization-based immunogen design targeting SARS-CoV-2 NTD and RBD.

Mutations and transient conformational movements of receptor binding domain (RBD) that make neutralizing epitopes momentarily unavailable, present immune escape routes to SARS-CoV-2. To mitigate viral escape, we developed a cocktail of neutralizing antibodies (NAbs) targeting epitopes located on different domains of spike (S) protein. Screening of a library of monoclonal antibodies generated from peripheral blood mononuclear cells of COVID-19 convalescent patients yielded potent NAbs, targeting N-terminal domain (NTD) and RBD domain of S, effective at nM concentrations. Remarkably, combination of RBD-targeting NAbs and NTD-binding NAb, FC05, enhanced the neutralization potency in cell-based assays and animal model. Results of competitive SPR assays and cryo-EM structures of Fabs bound to S unveil determinants of immunogenicity. Combinations of immunogens, identified in NTD and RBD of S, when immunized in rabbits and macaques elicited potent protective immune responses against SARS-CoV-2. More importantly, two immunizations of this combination of NTD and RBD immunogens provided complete protection in macaques against SARS-CoV-2 challenge, without observable antibody-dependent enhancement of infection. These results provide a proof-of-concept for neutralization-based immunogen design targeting SARS-CoV-2 NTD and RBD.

Mercury (Hg) is a ubiquitous environmental toxicant with important public health implications. Hg causes neurotoxicity through astrocytes, Ca 2+ , neurotransmitters, mitochondrial damage, elevations of reactive oxygen species and post-translational modifications. However, the similarities and differences between the neurotoxic mechanisms caused by different chemical forms of Hg remain unclear. Zebrafish embryos were exposed to methylmercury (MeHgCl) or mercury chloride (HgCl 2 ) (0, 4, 40, 400 nM) up for 96 h. HgCl 2 exposure could significantly decrease survival rate, body length and eye size, delay the hatching period, induce tail bending and reduce the locomotor activity, and these effects were aggravated in the MeHgCl group. The compounds could increase the number of apoptotic cells in the brain and downregulate the expression of Shha, Ngn1 and Nrd, which contribute to early nervous development. The underlying mechanisms were investigated by metabolomics data. Galactose metabolism, tyrosine metabolism and starch and sucrose metabolism pathways were disturbed after HgCl 2 or MeHgCl exposure. In addition, the levels of three neurotransmitters including tyrosine, dopamine and tryptophan were reduced after HgCl 2 or MeHgCl exposure. Oxidative stress is related to metabolite changes, such as changes in the putrescine, niacinamide and uric acid contents in the HgCl 2 group, and squalene in the MeHgCl group. These data indicated that downregulation of these genes and abnormal metabolic profile and pathways contribute to the neurotoxicity of HgCl 2 and MeHgCl.

No abstract

Tributyltin (TBT), an environmental pollutant widely used in antifouling coatings, can cause multiple-organ toxicity and gut microbiome dysbiosis in organisms, and can even cause changes in the host metabolomic profiles.

No abstract

Severe Acute Respiratory Syndrome Coronavirus 2 (SARS-CoV-2) variants have been reported to be resistant to several neutralizing antibodies (NAbs) targeting Receptor Binding Domain (RBD) and N Terminal Domain (NTD) of spike (S) protein and thus inducing immune escape. However, fewer studies were carried out to investigate the neutralizing ability of S2-specific antibodies. In this research, 10 monoclonal antibodies (mAbs) targeting SARS-CoV-2 S2 subunit were generated from Coronavirus Disease 2019 (COVID-19) convalescent patients by phage display technology and molecular cloning technology. The binding activity of these S2-mAbs toward SARS-CoV-2 S, SARS-CoV-2 S2, SARS-CoV-2 RBD, SARS-CoV-2 NTD, severe acute respiratory syndrome coronavirus (SARS-CoV) S, SARS-CoV S2 and Middle East Respiratory Syndrome Coronavirus (MERS-CoV) S proteins were evaluated by enzyme-linked immunosorbent assay (ELISA). Their neutralizing potency toward SARS-CoV-2 wild-type (WT), B.1.1.7, B.1.351, P.1, B.1.617.2, B.1.1.1 and B.1.621 variants were determined by pseudo-virus-based neutralization assay. Results showed that S2E7-mAb had cross-activity to S or S2 proteins of SARS-CoV-2, SARS-CoV and MERS-CoV, while with limited neutralizing activity to pseudo-viruses of SARS-CoV-2 WT and variants. It is undeniable that the binding and neutralizing activities of the S2-targeting mAbs are significantly weaker than the previously reported antibodies targeting RBD and NTD, but our study may provide some evidences for understanding immune protection and identifying targets for vaccine design based on the conserved S2 subunit.

Mercury species have aroused wide concern in the past several decades due to their high toxicity. However, it is still difficult to detect ultra-trace mercury species due to their biochemical transformation in complex samples. To establish a simpler and more sensitive method for pre-concentration and determination of trace mercury species, molybdenum disulfide (MoS 2 ) nanosheets with sulfur-rich characteristics and enlarged interlayer spacing were prepared by a hydrothermal method coupled with a sonication-assisted liquid exfoliation method and acted as solid-phase extraction adsorbent. The nano-MoS 2 had high adsorption capacity, fast adsorption rate and excellent selectivity towards mercury ions (Hg 2+ ), methyl mercury (MeHg + ) and ethyl mercury (EtHg + ) in a wide pH range and complex matrices. And it could be easily regenerated by 4 mol L À1 HCl and reused several times. After optimizing HPLC-UV-HG-AFS conditions, a great linearity (1.0-10.0 mg L À1 , R 2 ¼ 0.999 for Hg 2+ , MeHg + and EtHg + ), lower detection limits (0.017, 0.037 and 0.021 ng mL À1 for Hg 2+ , MeHg + and EtHg + , respectively), relative standard deviations (<5%) and addition recoveries of the samples within 82.75-113.38% were observed. In summary, trace inorganic and organic mercury species in environmental and biological samples could be selectively enriched by the prepared nano-MoS 2 and efficiently seperated and detected by HPLC-UV-HG-AFS. The present study will help provide a better strategy for environmental monitoring and health assessment of mercury pollutants.