3 research outputs found
Human neutralizing antibodies to cold linear epitopes and subdomain 1 of the SARS-CoV-2 spike glycoprotein
Emergence of SARS-CoV-2 variants diminishes the efficacy of vaccines and antiviral monoclonal antibodies. Continued development of immunotherapies and vaccine immunogens resilient to viral evolution is therefore necessary. Using coldspot-guided antibody discovery, a screening approach that focuses on portions of the virus spike glycoprotein that are both functionally relevant and averse to change, we identified human neutralizing antibodies to highly conserved viral epitopes. Antibody fp.006 binds the fusion peptide and cross-reacts against coronaviruses of the four genera, including the nine human coronaviruses, through recognition of a conserved motif that includes the S2´ site of proteolytic cleavage. Antibody hr2.016 targets the stem helix and neutralizes SARS-CoV-2 variants. Antibody sd1.040 binds to subdomain 1, synergizes with antibody rbd.042 for neutralization and, like fp.006 and hr2.016, protects mice expressing human ACE2 against infection when present as bispecific antibody. Thus, coldspot-guided antibody discovery reveals donor-derived neutralizing antibodies that are cross-reactive with Orthocoronavirinae, including SARS-CoV-2 variants
Developing Targeted Hybrid Imaging Probes by Chelator Scaffolding
Positron
emission tomography (PET) as well as optical imaging (OI)
with peptide receptor targeting probes have proven their value for
oncological applications but also show restrictions depending on the
clinical field of interest. Therefore, the combination of both methods,
particularly in a single molecule, could improve versatility in clinical
routine. This proof of principle study aims to show that a chelator,
Fusarinine C (FSC), can be utilized as scaffold for novel dimeric
dual-modality imaging agents. Two targeting vectors (a minigastrin
analogue (MG11) targeting cholecystokinin-2 receptor overexpression
(CCK2R) or integrin α<sub>V</sub>β<sub>3</sub> targeting
cyclic pentapeptides (RGD)) and a near-infrared fluorophore (Sulfo-Cyanine7)
were conjugated to FSC. The probes were efficiently labeled with gallium-68
and in vitro experiments including determination of logD, stability,
protein binding, cell binding, internalization, and biodistribution
studies as well as in vivo micro-PET/CT and optical imaging in U-87MG
α<sub>V</sub>β<sub>3</sub>- and A431-CCK2R expressing
tumor xenografted mice were carried out. Novel bioconjugates showed
high receptor affinity and highly specific targeting properties at
both receptors. Ex vivo biodistribution and micro-PET/CT imaging studies
revealed specific tumor uptake accompanied by slow blood clearance
and retention in nontargeted tissues (spleen, liver, and kidneys)
leading to visualization of tumors at early (30 to 120 min p.i.).
Excellent contrast in corresponding optical imaging studies was achieved
especially at delayed time points (24 to 72 h p.i.). Our findings
show the proof of principle of chelator scaffolding for hybrid imaging
agents and demonstrate FSC being a suitable bifunctional chelator
for this approach. Improvements to fine-tune pharmacokinetics are
needed to translate this into a clinical setting