Extremely potent human monoclonal antibodies from COVID-19 convalescent patients

Human monoclonal antibodies are safe, preventive, and therapeutic tools that can be rapidly developed to help restore the massive health and economic disruption caused by the coronavirus disease 2019 (COVID-19) pandemic. By single-cell sorting 4,277 SARS-CoV-2 spike protein-specific memory B cells from 14 COVID-19 survivors, 453 neutralizing antibodies were identified. The most potent neutralizing antibodies recognized the spike protein receptor-binding domain, followed in potency by antibodies that recognize the S1 domain, the spike protein trimer, and the S2 subunit. Only 1.4% of them neutralized the authentic virus with a potency of 1–10 ng/mL. The most potent monoclonal antibody, engineered to reduce the risk of antibody-dependent enhancement and prolong half-life, neutralized the authentic wild-type virus and emerging variants containing D614G, E484K, and N501Y substitutions. Prophylactic and therapeutic efficacy in the hamster model was observed at 0.25 and 4 mg/kg respectively in absence of Fc functions.

Heparan Sulfate Proteoglycans Can Promote Opposite Effects on Adhesion and Directional Migration of Different Cancer Cells

Heparan sulfate proteoglycans take part in crucial events of cancer progression, such as epithelial-mesenchymal transition, cell migration, and cell invasion. Through sulfated groups on their glycosaminoglycan chains, heparan sulfate proteoglycans interact with growth factors, morphogens, chemokines, and extracellular matrix (ECM) proteins. The amount and position of sulfated groups are highly variable, thus allowing differentiated ligand binding and activity of heparan sulfate proteoglycans. This variability and the lack of specific ligands have delayed comprehension of the molecular basis of heparan sulfate proteoglycan functions. Exploiting a tumor-targeting peptide tool that specifically recognizes sulfated glycosaminoglycans, we analyzed the role of membrane heparan sulfate proteoglycans in the adhesion and migration of cancer cell lines. Starting from the observation that the sulfated glycosaminoglycan-specific peptide exerts a different effect on adhesion, migration, and invasiveness of different cancer cell lines, we identified and characterized three cell migration phenotypes, where different syndecans are associated with alternative signaling for directional cell migration.

Unraveling Heparan Sulfate Proteoglycan Binding Motif for Cancer Cell Selectivity

Membrane heparan sulfate proteoglycans (HSPG) regulate cell proliferation, migration, and differentiation and are therefore considered key players in cancer cell development processes. Here, we used the NT4 peptide to investigate how the sulfation pattern of HSPG on cells drives binding specificity. NT4 is a branched peptide that binds the glycosaminoglycan (GAG) chains of HSPG. It has already been shown to inhibit growth factor-induced migration and invasiveness of cancer cells, implying antagonist binding of HSPG. The binding affinity of NT4 with recombinant HSPG showed that NT4 bound glypican-3 and -4 and, with lower affinity, syndecan-4. NT4 binding to the cancer cell membrane was inversely correlated with sulfatase expression. NT4 binding was higher in cell lines with lower expression of SULF-1 and SULF-2, which confirms the determinant role of sulfate groups for recognition by NT4. Using 8-mer and 9-mer heparan sulfate (HS) oligosaccharides with analog disaccharide composition and different sulfation sites, a possible recognition motif was identified that includes repeated 6-O-sulfates alternating with N- and/or 2-O-sulfates. Molecular modeling provided a fully descriptive picture of binding architecture, showing that sulfate groups on opposite sides of the oligosaccharide can interact with positive residues on two peptide sequences of the branched structure, thus favoring multivalent binding and explaining the high affinity and selectivity of NT4 for highly sulfated GAGs. NT4 and possibly newly selected branched peptides will be essential probes for reconstructing and unraveling binding sites for cancer-involved ligands on GAGs and will pave the way for new cancer detection and treatment options.

The GAG-specific branched peptide NT4 reduces angiogenesis and invasiveness of tumor cells

Heparan sulfate proteoglycans, HSPGs, modulate major transformations of cancer cells, leading to tumor growth, invasion and metastasis. HSPGs also regulate neo-angiogenesis which prompts cancer progression and metastatic spread. A different aspect of heparin and analogs is their prominent role in the coagulation of blood. The interplay between coagulation and metastasis is being actively studied: anticoagulants such as heparin-derivatives have anticancer activity and procoagulants, such as thrombin, positively modulate proliferation, migration and invasion. The branched peptide NT4 binds to HSPGs and targets selectively cancer cells and tissues. For this, it had been extensively investigated in the last years and it proved to be efficient as chemotherapeutic and tumor tracer in in vivo models of cancer. We investigated the effects of the branched peptide in terms of modulation of angiogenesis and invasiveness of cancer cells. NT4 proved to have a major impact on endothelial cell proliferation, migration and tube formation, particularly when induced by FGF2 and thrombin. In addition, NT4 had important effects on aggressive tumor cells migration and invasion and it also had an anticoagulant profile.The peptide showed very interesting evidence of interference with tumor invasion pathways, offering a cue for its development as a tumor-targeting drug, and also for its use in the study of links between coagulation and tumor progression involving HSPGs.

Near-infrared quantum dots labelled with a tumor selective tetrabranched peptide for in vivo imaging

Background

Near-infrared quantum dots (NIR QDs) are a new class of fluorescent labels with excellent bioimaging features, such as high fluorescence intensity, good fluorescence stability, sufficient electron density, and strong tissue-penetrating ability. For all such features, NIR QDs have great potential for early cancer diagnosis, in vivo tumor imaging and high resolution electron microscopy studies on cancer cells.

Results

In the present study we constructed NIR QDs functionalized with the NT4 cancer-selective tetrabranched peptides (NT4-QDs). We observed specific uptake of NT4-QDs in human cancer cells in in vitro experiments and a much higher selective accumulation and retention of targeted QDs at the tumor site, compared to not targeted QDs, in a colon cancer mouse model.

Conclusions

NIR QDs labelled with the tetrabranched NT4 peptide have very promising performance for selective addressing of tumor cells in vitro and in vivo, proving rising features of NT4-QDs as theranostics.

Electronic supplementary material

The online version of this article (10.1186/s12951-018-0346-1) contains supplementary material, which is available to authorized users.

Hyaluronan-based graft copolymers bearing aggregation-induced emission fluorogens

In order to develop a technology platform based on two natural compounds from biorenewable resources, a short series of hyaluronan (HA) copolymers grafted with propargylated ferulic acid (HA–FA–Pg) were designed and synthesized to show different grafting degree values and their optical properties were characterized in comparison with reference compounds containing the same ferulate fluorophore. Interestingly, these studies revealed that the ferulate fluorophore was quite sensitive to the restriction of intramolecular motion and its introduction into the rigid HA backbone, as in HA–FA–Pg graft copolymers, led to higher photoluminescence quantum yield values than those obtained with the isolated fluorophore. Thus, the propargyl groups of HA–FA–Pg derivatives were exploited in the coupling with oleic acid through a biocompatible nona(ethylene glycol) spacer as an example of the possible applications of this technology platform. The resulting HA–FA–NEG–OA materials showed self-assembling capabilities in aqueous environment. Furthermore, HA–FA–NEG–OA derivatives have been shown to interact with phospholipid bilayers both in liposomes and living cells, retaining their fluorogenic properties and showing a high degree of cytocompatibility and for this reason they were proposed as potential biocompatible self-assembled aggregates forming new materials for biomedical applications.

A new technology platform has been developed with hyaluronan playing the role of the macromolecular carrier and ferulate the central role of natural small molecule fluorogenic clickable linker.

Abstract 1153: Heparan sulfate proteoglycans as novel target in cancer precise therapy

Heparan sulfate proteoglycans (HSPGs) have crucial regulatory roles in tumor onset and progression. HSPGs

are composed of a core protein and glycan chains characterized by repeated disaccharide units which can

be sulfated at different amount and position. HSPG have enormous structural diversity due to the different

possible modifications of the single saccharide units within the polysaccharide, such as position, sulphation

and acetylation. As a result HSPG can bind and modulate their binding to signaling molecules such as

growth factors, morphogens and chemokines1 .

HSPG proved to be important in mediating cancer development and progression by enhancing the binding

of growth factors, morphogens and cytokines to their cognate receptors, thus activating signaling pathways

that give rise to angiogensis, cell growth and proliferation, together with invasion and metastasis 2-3.

NT4 is a branched peptides that targets HSPGs. NT4 specifically binds to sulfated glycosaminoglycans on

cancer cells and tissues. NT4 can be conjugated to many different cytotoxic units and tracers. NT4

conjugated to paclitaxel produced tumor regression in a breast cancer orthotopic mouse model 4. NT4

conjugated to tracers can discriminate between tumor and healthy tissue in different human cancer

specimen5.

We will show the ability of NT4 to drive tracers onto tumor lesions by means of Qdots and in vivo imaging,

proving their promising features as theranostics. We will also show NT4 ability to interfere with HSPG-

modulated activities such as: tumor cell proliferation, migration and invasion of matrix; as well as

endothelial cells proliferation, migration and tube formation. NT4-HSPG interactions and consequent

modulation of signaling pathways will prove the importance of this versatile tool, NT4, in addressing tumor

cells and interfering in their cell-cell and cell-matrix communications.

Bibliography

1. Gharbaran R. et al. Tumour Biol. 2016; 37:11573-11588.

2. Purushothaman A et al. Blood. 2010; 115:2449-57.

3. Lee JH et al. J Biol Chem. 2009; 284:27167-75.

4. Brunetti, J. et al. Scientific Reports. DOI:10.1038/srep17736

5. Falciani C. et al. J Med Chem. 2013; 56:5009-18.

Citation Format: Chiara Falciani, Jlenia Brunetti, Lorenzo Depau, Alessandro Pini, Giulia Riolo, Elisabetta Mandarini, Luisa Bracci. Heparan sulfate proteoglycans as novel target in cancer precise therapy [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2017; 2017 Apr 1-5; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2017;77(13 Suppl):Abstract nr 1153. doi:10.1158/1538-7445.AM2017-1153

Abstract 3899: Preclinical development of tetra-branched NT4 peptide theranostics

The tetra-branched peptide NT4 is a potential cancer theranostic, which very selectively binds to human cancer tissues in different malignancies and can efficiently and selectively deliver drugs or liposomes for cancer cell imaging or therapy, in vitro and in vivo. By using NT4 conjugated to methotrexate or 5FdU we obtained significant reduction of tumor growth in xenografted nude mice. Very recently we reported that conjugation of paclitaxel to NT4 leads to increased therapeutic activity of the drug in an orthotopic model of breast cancer in mice and produces tumor regression which is not achieved with unconjugated paclitaxel in identical experimental conditions. We demonstrated that NT4 specifically binds to sulfated glycosaminoglycans and LRP receptors on cancer cells and tissues.

Considering the role of sulfated glycosaminoglycans in cancer cell interaction with the extracellular matrix, we have analyzed the effect of NT4 in cancer cell adhesion and migration on different supports. NT4 inhibits adhesion and migration of different human cancer cell lines, strongly affecting directionality of cell movement.

We have also constructed and validated a novel theranostics nanodevices, by conjugation of NT4 to quantum dots, for selective diagnosis and imaging of different human carcinomas.

Thanks to their high cancer selectivity and versatile chemical conformation, NT4 peptides can be exploited for constructing cancer theranostics, which may also reduce tumor aggressiveness and metastatic potential by inhibiting cancer cell migration.

References:

Falciani, C. et al. Cancer selectivity of tetrabranched neurotensin peptides is generated by simultaneous binding to sulfated glycosaminoglycans and protein receptors. J Med Chem. 2013, 56, 5009-18.

Brunetti, J. et al. Tumor-selective peptide-carrier delivery of Paclitaxel increases in vivo activity of the drug. Scientific Reports. DOI:10.1038/srep17736.

Citation Format: Jlenia Brunetti, Lorenzo Depau, Chiara Falciani, Giulia Riolo, Elisabetta Mandarini, Alessandro Pini, Luisa Bracci. Preclinical development of tetra-branched NT4 peptide theranostics. [abstract]. In: Proceedings of the 107th Annual Meeting of the American Association for Cancer Research; 2016 Apr 16-20; New Orleans, LA. Philadelphia (PA): AACR; Cancer Res 2016;76(14 Suppl):Abstract nr 3899.

Abstract 5625: Targeting different LRP receptors and sulfated proteoglycan by branched neurotensin provide high cancer selectivity

In previous paper we reported on the much higher selectivity toward cancer cells and tissues of tetra-branched neurotensin peptides (NT4) compared to monomeric NT peptide. We also demonstrated that NT4 can be coupled to many different functional units for cancer cell tracing and drug delivery and can induce tumor growth reduction in animal studies. We then proposed NT4 as promising cancer selective theranostics for different human cancers, including CRC, pancreas adenocarcinoma and urinary bladder cancer. Nonetheless, multimeric binding of tetrabranched peptides, together with the chemical modification produced by coupling to the branched core, might have modified receptor selectivity of NT4 with respect to native monomeric NT and actually we had no conclusive indication on which receptor our branched NT4 peptides were binding to.

Data reported in the present paper demonstrate that synthesis of neurotensin sequence in a tetra-branched form induce a switching of receptor selectivity, by decreasing affinity to the NT high affinity receptor NTR1 and contemporarily acquiring binding to additional receptors, which produces a much higher cancer cell selectivity of NT4 with respect to monomeric NT peptides. We demonstrate here that NT4 binds sortilin and SorLa and also acquire the ability to bind different receptors belonging to the Low Density Lipoprotein Receptor Related Protein (LRP) family as well as heparin and other Heparan Sulfate Proteoglycans (HSPG).

The much higher binding of NT4 in respect to native NT to either cancel cell lines or human cancer surgical samples, as well as the higher selectivity toward human cancer tissues of NT4 is due to binding to different membrane receptors, which are very selectively expressed by many different human cancers. Moreover, our results confirm that sulfated proteoglycan can mimic the ligand binding site of different LRP receptors and indicate that targeting of multiple LRP receptors together with sulfated proteoglycans produce an extremely high selectivity towards many different human cancers.

Citation Format: Luisa Bracci, Chiara Falciani, Jlenia Brunetti, Barbara Lelli, Niccolò Ravenni, Luisa Lozzi, Lorenzo Depau, Alessandro Pini. Targeting different LRP receptors and sulfated proteoglycan by branched neurotensin provide high cancer selectivity. [abstract]. In: Proceedings of the 104th Annual Meeting of the American Association for Cancer Research; 2013 Apr 6-10; Washington, DC. Philadelphia (PA): AACR; Cancer Res 2013;73(8 Suppl):Abstract nr 5625. doi:10.1158/1538-7445.AM2013-5625

Pulsatile Gn-Rh induced ovulatory cycles: echographic and endocrine aspects

Five patients with primary hypogonadotrophic amenorrhea were treated for the induction of ovulation with I.V. pulsatile Gn-Rh doses ranging from 2.5 to 12.5 micrograms/90 min) for 15 cycles. Ovulation occurred during Gn-Rh treatment in 7 cycles (A) or after i.m. HGC administration (5,000-10,000 IU) (B = 6) (ovulation rate = 86%). Four pregnancies (A = 2; B = 2) were obtained (in one case there was a twin pregnancy). Echographic and endocrine patterns were evaluated. Ovulatory follicular diameter was 18.3 +/- 6.0 mm, no difference between A and B (21.8 +/- 5.6 and 16.0 +/- 5.1 mm, respectively) was observed. In addition E2 preovulatary plasma levels were similar in the two groups examined (334 +/- 131 and 300 +/- 89 pg/ml, respectively). Also endocrine and echographic profiles of conceptive (C) and non conceptive (NC) cycles were similar. Furthermore all doses resulted effective in determining the ovarian response and no difference was found at different dosage used. It is concluded that pulsatile GnRh is a "physiological" way of inducing ovulation in PHA patients. By analysis of the present data we consider it advisable to induce ovulation by the enhancement of the endogenous LH peak which occurs during Gn-Rh administration (A group) and then periodic injections of HCG can be used for maintaining the luteal function.