Human single chain Fv antibodies and a complementarity determining region-derived peptide binding to amyloid-beta 1–42

Application of engineered antibodies (scFvs and nanobodies) targeting pathological protein aggregates in Alzheimer's disease

INTRODUCTION

The misfolding and aggregation of proteins are associated with various neurodegenerative diseases, such as Alzheimer's disease (AD). The small-molecule engineered antibodies, such as single-chain fragment variable (scFv) antibodies and nanobodies (Nbs), have gained attention in recent years due to their strong conformational specificity, ability to cross the blood-brain barrier (BBB), low immunogenicity, and enhanced proximity to active sites within aggregates.

AREAS COVERED

We have reviewed recent advances in therapies involving scFvs and Nbs that efficiently and specifically target pathological protein aggregates. Relevant publications were searched for in MEDLINE, GOOGLE SCHOLAR, Elsevier ScienceDirect and Wiley Online Library.

EXPERT OPINION

We reviewed the recent and specific targeting of pathological protein aggregates by scFvs and Nbs. These engineered antibodies can inhibit the aggregation or promote the disassembly of misfolded proteins by recognizing antigenic epitopes or through conformational specificity. Additionally, we discuss strategies for improving the effective application of engineered antibodies in treating AD. These technological strategies will lay the foundation for the clinical application of small-molecule antibody drugs in developing effective treatments for neurological diseases. Through rational application strategies, small-molecule engineered antibodies are expected to have significant potential in targeted therapy for neurological disorders.

Identification of potential inhibitors against Alzheimer-related proteins in Cordyceps militaris ethanol extract: experimental evidence and computational analyses

Laboratory experiments were carried out to identify the chemical composition of Cordyceps militaris and reveal the first evidence of their Alzheimer-related potential. Liquid chromatography-mass spectrometry analysis identified 21 bioactive compounds in the ethanol extract (1-21). High-performance liquid chromatography quantified the content of cordycepin (0.32%). Bioassays revealed the overall anti-Alzheimer potential of the extract against acetylcholinesterase (IC50 = 115.9 ± 11.16 µg mL-1). Multi-platform computations were utilized to predict the biological inhibitory effects of its phytochemical components against Alzheimer-related protein structures: acetylcholinesterase (PDB-4EY7) and β-amyloid protein (PDB-2LMN). In particular, 7 is considered as a most effective inhibitor predicted by its chemical stability in dipole-based environments (ground state - 467.26302 a.u.; dipole moment 11.598 Debye), inhibitory effectiveness (DS ¯ - 13.6 kcal mol-1), polarized compatibility (polarizability 25.8 Å3; logP - 1.01), and brain penetrability (logBB - 0.244; logPS - 3.047). Besides, 3 is promising as a brain-penetrating agent (logBB - 0.257; logPS - 2.400). The results preliminarily suggest further experimental attempts to verify the pro-cognitive effects of l(-)-carnitine (7).

Supplementary Information

The online version contains supplementary material available at 10.1007/s13205-023-03714-9.

Downsizing antibodies: Towards complementarity-determining region (CDR)-based peptide mimetics

Monoclonal antibodies emerged as an important therapeutic drug class with remarkable specificity and binding affinity. Nonetheless, these heterotetrameric immunoglobulin proteins come with high manufacturing and therapeutic costs which can take extraordinary proportions, besides other limitations such as their limited in cellulo access imposed by their molecular size (ca. 150 kDa). These drawbacks stimulated the development of downsized functional antibody fragments (ca. 15-50 kDa), together with smaller synthetic peptides (ca. 1-3 kDa) derived from the antibodies' crucial complementarity-determining regions (CDR). Despite the general lack of success in the literal translation of CDR loops in peptide mimetics, rational structure-based and computational approaches have shown their potential for obtaining functional CDR-based peptide mimetics. In this review, we describe the efforts made in the development of antibody and nanobody paratope-derived peptide mimetics with particular focus on the used design strategies, in addition to highlighting the challenges associated with their development.

Design of peptide-based inhibitor agent against amyloid-β aggregation: Molecular docking, synthesis and in vitro evaluation

Formation of the amyloid beta (Aβ) peptide aggregations represents an indispensable role in appearing and progression of Alzheimer disease. β-sheet breaker peptides can be designed and modified with different amino acids in order to improve biological properties and binding affinity to the amyloid beta peptide. In the present study, three peptide sequences were designed based on the hopeful results of LIAIMA peptide and molecular docking studies were carried out onto the monomer and fibril structure of amyloid beta peptide using AutoDock Vina software. According to the obtained interactions and binding energy from docking, the best-designed peptide (d-GABA-FPLIAIMA) was chosen and synthesized in great yield (%96) via the Fmoc solid-phase peptide synthesis. The synthesis and purity of the resulting peptide were estimated and evaluated by Mass spectroscopy and Reversed-phase high-performance liquid chromatography (RP-HPLC) methods, respectively. Stability studies in plasma and Thioflavin T (ThT) assay were performed in order to measure the binding affinity and in vitro aggregation inhibition of Aβ peptide. The d-GABA-FPLIAIMA peptide showed good binding energy and affinity to Aβ fibrils, high stability (more than 90%) in human serum, and a reduction of 20% in inhibition of the Aβ aggregation growth. Finally, the favorable characteristics of our newly designed peptide make it a promising candidate β-sheet breaker agent for further in vivo studies.

Recombinant Antibody Fragments for Neurodegenerative Diseases

BACKGROUND

Recombinant antibody fragments are promising alternatives to full-length immunoglobulins and offer important advantages compared with conventional monoclonal antibodies: extreme specificity, higher affinity, superior stability and solubility, reduced immunogenicity as well as easy and inexpensive large-scale production.

OBJECTIVE

In this article we will review and discuss recombinant antibodies that are being evaluated for neurodegenerative diseases in pre-clinical models and in clinical studies and will summarize new strategies that are being developed to optimize their stability, specificity and potency for advancing their use.

METHODS

Articles describing recombinant antibody fragments used for neurological diseases were selected (PubMed) and evaluated for their significance.

RESULTS

Different antibody formats such as single-chain fragment variable (scFv), single-domain antibody fragments (VHHs or sdAbs), bispecific antibodies (bsAbs), intrabodies and nanobodies, are currently being studied in pre-clinical models of cancer as well as infectious and autoimmune diseases and many of them are being tested as therapeutics in clinical trials. Immunotherapy approaches have shown therapeutic efficacy in several animal models of Alzheimer´s disease (AD), Parkinson disease (PD), dementia with Lewy bodies (DLB), frontotemporal dementia (FTD), Huntington disease (HD), transmissible spongiform encephalopathies (TSEs) and multiple sclerosis (MS). It has been demonstrated that recombinant antibody fragments may neutralize toxic extra- and intracellular misfolded proteins involved in the pathogenesis of AD, PD, DLB, FTD, HD or TSEs and may target toxic immune cells participating in the pathogenesis of MS.

CONCLUSION

Recombinant antibody fragments represent a promising tool for the development of antibody-based immunotherapeutics for neurodegenerative diseases.

A novel antibody targeting sequence 31-35 in amyloid β protein attenuates Alzheimer's disease-related neuronal damage

Amyloid β protein (Aβ) plays a critical role in pathogenesis of Alzheimer's disease (AD). Our previous studies indicated that the sequence 31-35 in Aβ molecule is an effective active center responsible for Aβ neurotoxicity in vivo and in vitro. In the present study, we prepared a novel antibody specifically targeting the sequence 31-35 of amyloid β protein, and investigated the neuroprotection of the anti-Aβ_31-35 antibody against Aβ_1-42 -induced impairments in neuronal viability, spatial memory, and hippocampal synaptic plasticity in rats. The results showed that the anti-Aβ_31-35 antibody almost equally bound to both Aβ_31-35 and Aβ_1-42 , and pretreatment with the antibody dose-dependently prevented Aβ_1-42 -induced cytotoxicity on cultured primary cortical neurons. In behavioral study, intracerebroventricular (i.c.v.) injection of anti-Aβ_31-35 antibody efficiently attenuated Aβ_1-42 -induced impairments in spatial learning and memory of rats. In vivo electrophysiological experiments further indicated that Aβ_1-42 -induced suppression of hippocampal synaptic plasticity was effectively reversed by the antibody. These results demonstrated that the sequence 31-35 of Aβ may be a new therapeutic target, and the anti-Aβ_31-35 antibody could be a novel immunotheraputic approach for the treatment of AD. © 2016 Wiley Periodicals, Inc.

Isolation of an HIV-1 neutralizing peptide mimicking the CXCR4 and CCR5 surface from the heavy-chain complementary determining region 3 repertoire of a viremic controller

OBJECTIVES

The recent identification of neutralizing antibodies able to prevent viral rebound reemphasized the interest in humoral immune responses to control HIV-1 infection. In this study, we characterized HIV-1-inhibiting sequences from heavy-chain complementary determining region 3 (HCDR3) repertoires of a viremic controller.

DESIGN AND METHODS

IgM and IgG-derived HCDR3 repertoires of a viremic controller presenting plasma-neutralizing activity and characterized by over 20 years of infection with a stable CD4 T-cell count were displayed on filamentous phage to identify HCDR3 repertoire-derived peptides inhibiting HIV-1 entry.

RESULTS

Screening of phage libraries against recombinant gp120 led to the identification of an HCDR3-derived peptide sequence (LRTV-1) displaying antiviral properties against both X4 and R5 viruses. The interaction of LRTV-1 with gp120 was enhanced upon CD4 binding and sequence comparison revealed homology between LRTV-1 and the second extracellular loop of C-X-C chemokine receptor type 4 (CXCR4) (11/23) and the N-terminus of C-C chemokine receptor type 5 (CCR5) (7/23). Alanine scanning experiments identified different clusters of residues critical for interaction with the viral envelope protein.

CONCLUSIONS

LRTV-1 peptide is to date the smallest human HCDR3 repertoire-derived peptide identified by phage display inhibiting HIV entry of R5 and X4 viruses. This peptide recognizes a CD4-dependent gp120 epitope critical for coreceptor binding and mimics the surface of CXCR4 and CCR5. Our data emphasize the potential of human HCDR3 immune repertoires as sources of small biologically active peptides for HIV cure.

Novel amyloid-beta specific scFv and VH antibody fragments from human and mouse phage display antibody libraries

Anti-amyloid immunotherapy has been proposed as an appropriate therapeutic approach for Alzheimer's disease (AD). Significant efforts have been made towards the generation and assessment of antibody-based reagents capable of preventing and clearing amyloid aggregates as well as preventing their synaptotoxic effects. In this study, we selected a novel set of human anti-amyloid-beta peptide 1-42 (Abeta1-42) recombinant monoclonal antibodies in a single chain fragment variable (scFv) and a single-domain (VH) format. We demonstrated that these antibody fragments recognize in a specific manner amyloid-beta deposits in APP/Tg mouse brains, inhibit toxicity of oligomeric Abeta1-42 in neuroblastoma cell cultures in a concentration-dependent manner and reduced amyloid deposits in APP/Tg2576 mice after intracranial administration. These antibody fragments recognize epitopes in the middle/C-terminus region of Abeta, which makes them strong therapeutic candidates due to the fact that most of the Abeta species found in the brains of AD patients display extensive N-terminus truncations/modifications.

Epitope mapping and neuroprotective properties of a human single chain FV antibody that binds an internal epitope of amyloid-beta 1-42

Active and passive immunotherapy targeted at the amyloid-beta (Abeta) peptide has been proposed as therapeutic approach against Alzheimer's disease (AD), and efforts towards the generation and application of antibody-based reagents that are capable of preventing and clearing amyloid aggregates are currently under active investigation. Previously, we selected and characterized a new anti-Abeta1-42 phage-displayed scFv antibody, designated clone b4.4, using a non-immune human scFv antibody library and demonstrated that a peptide based on the sequence of the Ig heavy chain (VH) complementarity-determining region (HCDR3) of this antibody fragment bound to Abeta1-42)and had neuroprotective potential against Abeta1-42 mediated neurotoxicity in rat hippocampal cultured neurons. In the present study, using novel computational methods and in vitro experiments we demonstrated that b4.4 binds to the central region of Abeta1-42. We also demonstrated that this scFv antibody binds to Abeta-derived diffusible ligands (ADDLs) and neutralizes the toxicity of both fibrillar and oligomeric forms of Abeta1-42 tested in vitro in SH-SY5Y cell cultures.

Non-immunized natural human heavy chain CDR3 repertoires allow the isolation of high affinity peptides mimicking a human influenza hemagglutinin epitope

In this study we constructed two phage libraries displaying non-immunized natural human IgM derived HCDR3 repertoires. One library was structurally constrained by a Gly to Cys substitution at position 104 enabling the formation of a disulfide bridge with the Cys at position 92. Panning of these libraries on an anti-human influenza hemagglutinin (HA) antibody resulted in the selection of 16 different HCDR3 loops displaying different degrees of sequence homology with the HA epitope. The specificity of the HCDR3 loops recovered from the structurally constrained library was confirmed by competition assays using the HA epitope. Only one of these HCDR3 peptides contained Cys104. Structural analysis of these sequences revealed that the loss of Cys104 was associated with an increased preference for the formation of the type I beta-turn required for high affinity binding to the antibody. Affinity studies confirmed that the HCDR3 peptides containing the sequence YDVPDY and Gly104 had affinities in the nanomolar range (K(d)=7.6 nM) comparable to the HA epitope. These findings provided evidence that the recovered HCDR3 sequences may bind to their target in a conformation that is unreachable by the parental antibody from which the HCDR3 was derived. Furthermore, the isolation of target-specific and high affinity binders demonstrates the value of HCDR3 libraries as a source of 'biologically randomized' sequences of human origin for the identification of peptidic lead molecules.

Anti-Abeta single-chain antibody delivery via adeno-associated virus for treatment of Alzheimer's disease

Immunization of mouse models of Alzheimer disease (AD) with amyloid-peptide (Abeta) reduces Abeta deposits and attenuates their memory and learning deficits. Recent clinical trials were halted due to meningoencephalitis, presumably induced by T cell mediated and/or Fc-mediated immune responses. Because injection of anti-Abeta F(ab')(2) antibodies also induces clearance of amyloid plaques in AD mouse models, we have tested a novel gene therapy modality where an adeno-associated virus (AAV) encoding anti-Abeta single-chain antibody (scFv) is injected into the corticohippocampal regions of AD mouse models. One year after injection, expression of scFv was readily detectable in the neurons of the hippocampus without discernible neurotoxicity. AD mouse models subjected to AAV injection had much less amyloid deposits at the injection sites than the mouse models subjected to PBS injection. Because the scFv lacks the Fc portion of the immunoglobulin molecule, this modality may be a feasible solution for AD without eliciting inflammation.

Clearance of amyloid-beta in Alzheimer's disease: progress, problems and perspectives

Alzheimer's disease (AD) is the most common form of senile dementia and the fourth highest cause of disability and death in the elderly. Amyloid-beta (Abeta) has been widely implicated in the etiology of AD. Several mechanisms have been proposed for Abeta clearance, including receptor-mediated Abeta transport across the blood-brain barrier and enzyme-mediated Abeta degradation. Moreover, pre-existing immune responses to Abeta might also be involved in Abeta clearance. In AD, such mechanisms appear to have become impaired. Recently, therapeutic approaches for Abeta clearance, targeting immunotherapy and molecules binding Abeta, have been developed. In this review, we discuss recent progress and problems with respect to Abeta clearance mechanisms and propose strategies for the development of therapeutics targeting Abeta clearance.

The antibody repertoire in evolution: chance, selection, and continuity

All jawed vertebrates contain the genetic elements essential for the function of the adaptive/combinatorial immune response, have diverse sets of natural antibodies resulting from segmental gene recombination, express comparable functional repertoires and can produce specific antibodies following appropriate immunization. Profound variability occurs in the third hypervariable (CDR3) segments of light and heavy chains even within antibodies of the same ostensible specificity. Germline VH and VL elements, as well as the joining (J) segments are highly conserved among the distinct vertebrate species. Conservation is particularly noted among the VH3-like sequences of all jawed vertebrates in the FR2 and FR3 segments, as well as in the FGXGT(R or K)L J-segment characteristic of light chains and TCRs and the WGXGT(uncharged)VT JH segments. Human VH3-53 and Vlambda6 family orthologs may be present over the entire range of vertebrates. Models of the three-dimensional structures of shark VH/VL combining sites indicate similarity in framework structure and comparable CDR usage to those of man. Although carcharhine shark VH regions show greater than 50% identity to the human VH germline prototype, searches of lower deuterostome and invertebrate databases fail to detect molecules with significant relatedness. Overall, antibodies of jawed vertebrates show tremendous individual diversity, but are constructed incorporating design features that arose with the evolutionary emergence of the jawed vertebrates and have been conserved through at least 450 million years of evolutionary time.