Current methods for diagnosing transmissible spongiform encephalopathies rely on the degradation of the cellular prion protein (PrP C ) and the subsequent detection of the protease-resistant remnant of the pathological prion isoform PrP Sc by antibodies that react with all forms of PrP. We report on a monoclonal antibody, V5B2, raised against a peptide from the C-terminal part of PrP, which recognizes an epitope specific to PrP Sc . In cryostat sections from Creutzfeldt-Jacob's disease (CJD) patients' brains, V5B2 selectively labels various deposits of PrP Sc without any pretreatment for removal of PrP C . V5B2 does not bind to non-CJD brain samples or to recombinant PrP, either in its native or denatured form. Specificity for PrP is confirmed by a sandwich enzyme-linked immunosorbent assay utilizing V5B2, which discriminates between CJD and normal samples without proteinase K treatment, and by immunoprecipitation from CJD brain homogenate. The PrP Sc -specific epitope is disrupted by denaturation. We conclude that the C-terminal part of PrP in disease-associated PrP Sc aggregates forms a structural epitope whose conformation is distinct from that of PrP C .

Delivery of therapeutic proteins into tissues and across the blood-brain barrier (BBB) is limited by the size and biochemical properties of the proteins. Efficient delivery across BBB is generally restricted to small, highly lipophilic molecules. However, in the last decades, several peptides that can pass cell membranes have been identified. It has been shown that these peptides are also capable of delivering large hydrophilic cargoes into cells and are therefore a powerful biological tool for transporting drugs across cell membranes and even into the brain. We designed and prepared a single-chain antibody fragment (scFvs), specific for the pathological form of the prion protein (PrP(Sc)), where a cell-penetrating peptide (CPP) was used as a linker between the two variable domains of the scFv. The intravenously administered recombinant scFv-CPP was successfully targeted to and delivered into mouse brain cells. Our single-chain antibody fragments are of special interest in view of possible therapeutic reagents design not only for prion diseases but also for other neurodegenerative diseases.

Antibodies have been shown to be a potent therapeutic tool. However, their use for targeting brain diseases, including neurodegenerative diseases and brain cancers, has been limited, particularly because the blood–brain barrier (BBB) makes brain tissue hard to access by conventional antibody-targeting strategies. In this review, we summarize new antibody therapeutic approaches to target brain tumors, especially malignant gliomas, as well as their potential drawbacks. Many different brain delivery platforms for antibodies have been studied such as liposomes, nanoparticle-based systems, cell-penetrating peptides (CPPs), and cell-based approaches. We have already shown the successful delivery of single-chain fragment variable (scFv) with CPP as a linker between two variable domains in the brain. Antibodies normally face poor penetration through the BBB, with some variants sufficiently passing the barrier on their own. A “Trojan horse” method allows passage of biomolecules, such as antibodies, through the BBB by receptor-mediated transcytosis (RMT). Such examples of therapeutic antibodies are the bispecific antibodies where one binding specificity recognizes and binds a BBB receptor, enabling RMT and where a second binding specificity recognizes an antigen as a therapeutic target. On the other hand, cell-based systems such as stem cells (SCs) are a promising delivery system because of their tumor tropism and ability to cross the BBB. Genetically engineered SCs can be used in gene therapy, where they express anti-tumor drugs, including antibodies. Different types and sources of SCs have been studied for the delivery of therapeutics to the brain; both mesenchymal stem cells (MSCs) and neural stem cells (NSCs) show great potential. Following the success in treatment of leukemias and lymphomas, the adoptive T-cell therapies, especially the chimeric antigen receptor-T cells (CAR-Ts), are making their way into glioma treatment as another type of cell-based therapy using the antibody to bind to the specific target(s). Finally, the current clinical trials are reviewed, showing the most recent progress of attractive approaches to deliver therapeutic antibodies across the BBB aiming at the specific antigen.

Antibodies are widely exploited as research/diagnostic tools and therapeutics. Despite providing exciting research opportunities, the multitude of available antibodies also offers a bewildering array of choice. Importantly, not all companies comply with the highest standards, and thus many reagents fail basic validation tests. The responsibility for antibodies being fit for purpose rests, surprisingly, with their user. This paper condenses the extensive experience of the European Monoclonal Antibody Network to help researchers identify antibodies specific for their target antigen. A stepwise strategy is provided for prioritising antibodies and making informed decisions regarding further essential validation requirements. Web-based antibody validation guides provide practical approaches for testing antibody activity and specificity. We aim to enable researchers with little or no prior experience of antibody characterization to understand how to determine the suitability of their antibody for its intended purpose, enabling both time and cost effective generation of high quality antibody-based data fit for publication.