Designing of a bispecific antibody against SARS-CoV-2 spike glycoprotein targeting human entry receptors DPP4 and ACE2

Function and mechanism of bispecific antibodies targeting SARS-CoV-2

As the dynamic evolution of SARS-CoV-2 led to reduced efficacy in monoclonal neutralizing antibodies and emergence of immune escape, the role of bispecific antibodies becomes crucial in bolstering antiviral activity and suppressing immune evasion. This review extensively assesses a spectrum of representative bispecific antibodies targeting SARS-CoV-2, delving into their characteristics, design formats, mechanisms of action, and associated advantages and limitations. The analysis encompasses factors influencing the selection of parental antibodies and strategies for incorporating added benefits in bispecific antibody design. Furthermore, how different classes of parental antibodies contribute to augmenting the broad-spectrum neutralization capability within bispecific antibodies is discussed. In summary, this review presents analyses and discussions aimed at offering valuable insights for shaping future strategies in bispecific antibody design to effectively confront the challenges posed by SARS-CoV-2 and propel advancements in antiviral therapeutic development.

Unleashing the power of antibodies: Engineering for tomorrow's therapy

Antibodies play a crucial role in host defense against various diseases. Antibody engineering is a multidisciplinary field that seeks to improve the quality of life of humans. In the context of disease, antibodies are highly specialized proteins that form a critical line of defense against pathogens and the disease caused by them. These infections trigger the innate arm of immunity by presenting on antigen-presenting cells such as dendritic cells. This ultimately links to the adaptive arm, where antibody production and maturation occur against that particular antigen. Upon binding with their specific antigens, antibodies trigger various immune responses to eliminate pathogens in a process called complement-dependent cytotoxicity and phagocytosis of invading microorganisms by immune cells or induce antibody-dependent cellular cytotoxicity is done by antibodies. These engineered antibodies are being used for various purposes, such as therapeutics, diagnostics, and biotechnology research. Cutting-edge techniques that include hybridoma technology, transgenic mice, display techniques like phage, yeast and ribosome displays, and next-generation sequencing are ways to engineer antibodies and mass production for the use of humankind. Considering the importance of antibodies in protecting from a diverse array of pathogens, investing in research holds great promise to develop future therapeutic targets to combat various diseases.

Effect of DPP4/CD26 expression on SARS‑CoV‑2 susceptibility, immune response, adenosine (derivatives m62A and CD) regulations on patients with cancer and healthy individuals

The worldwide COVID‑19 pandemic was brought on by a new coronavirus (SARS Cov‑2). A marker/receptor called Dipeptidyl peptidase 4/CD26(DPP4/CD26) may be crucial in determining susceptibility to tumors and coronaviruses. However, the regulation of DPP4 in COVID‑invaded cancer patients and its role on small molecule compounds remain unclear. The present study used the Human Protein Atlas, Monaco, and Schmiedel databases to analyze the expression of DPP4 in human tissues and immune cells. The association between DPP4 expression and survival in various tumor tissues was compared using GEPIA 2. The DNMIVD database was used to analyze the correlation between DPP4 expression and promoter methylation in various tumors. On the cBioPortal network, the frequency of DPP4 DNA mutations in various cancers was analyzed. The correlation between DPP4 expression and immunomodulators was analyzed by TISIDB database. The inhibitory effects of cordycepin (CD), N6, N6‑dimethyladenosine (m⁶₂A) and adenosine (AD) on DPP4 in cancer cells were evaluated. DPP4 was mainly expressed in endocrine tissue, followed by gastrointestinal tract, female tissue (mainly in placenta), male tissue (mainly in prostate and seminal vesicle), proximal digestive tract, kidney, bladder, liver, gallbladder and respiratory system. In immune cells, DPP4 mRNA was mainly expressed in T cells, and its expression was upregulated in esophageal carcinoma, kidney renal papillary cell carcinoma (KIRP), liver hepatocellular carcinoma (LIHC), lung adenocarcinoma, pancreatic adenocarcinoma, prostate adenocarcinoma, stomach adenocarcinoma, thyroid carcinoma and thymoma. However, it was downregulated in breast invasive carcinoma, kidney chromophobe, lung squamous cell carcinoma and skin cutaneous melanoma. Thus, DPP4 is involved in viral invasion in most types of cancer. The expression of DPP4 could be inhibited by CD, m⁶₂A and AD in different tumor cells. Moreover, CD significantly inhibited the formation of GFP‑positive syncytial cells. In vivo experiments with AD injection further showed that AD significantly inhibited lymphocyte activating factor 3 expression. These drugs may have potential to treat COVID‑19 by targeting DPP4. Thus, DPP4 may be medically significant for SARS‑CoV‑2‑infected cancer patients, providing prospective novel targets and concepts for the creation of drugs against COVID‑19.

The many facets of CD26/dipeptidyl peptidase 4 and its inhibitors in disorders of the CNS - a critical overview

Dipeptidyl peptidase 4 is a serine protease that cleaves X-proline or X-alanine in the penultimate position. Natural substrates of the enzyme are glucagon-like peptide-1, glucagon inhibiting peptide, glucagon, neuropeptide Y, secretin, substance P, pituitary adenylate cyclase-activating polypeptide, endorphins, endomorphins, brain natriuretic peptide, beta-melanocyte stimulating hormone and amyloid peptides as well as some cytokines and chemokines. The enzyme is involved in the maintenance of blood glucose homeostasis and regulation of the immune system. It is expressed in many organs including the brain. DPP4 activity may be effectively depressed by DPP4 inhibitors. Apart from enzyme activity, DPP4 acts as a cell surface (co)receptor, associates with adeosine deaminase, interacts with extracellular matrix, and controls cell migration and differentiation. This review aims at revealing the impact of DPP4 and DPP4 inhibitors for several brain diseases (virus infections affecting the brain, tumours of the CNS, neurological and psychiatric disorders). Special emphasis is given to a possible involvement of DPP4 expressed in the brain.While prominent contributions of extracerebral DPP4 are evident for a majority of diseases discussed herein; a possible role of "brain" DPP4 is restricted to brain cancers and Alzheimer disease. For a number of diseases (Covid-19 infection, type 2 diabetes, Alzheimer disease, vascular dementia, Parkinson disease, Huntington disease, multiple sclerosis, stroke, and epilepsy), use of DPP4 inhibitors has been shown to have a disease-mitigating effect. However, these beneficial effects should mostly be attributed to the depression of "peripheral" DPP4, since currently used DPP4 inhibitors are not able to pass through the intact blood-brain barrier.

Potential use of the S-protein-Angiotensin converting enzyme 2 binding pathway in the treatment of coronavirus disease 2019

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2), the pathogen that causes coronavirus disease 2019 (COVID-19), infects humans through a strong interaction between the viral spike protein (S-protein) and angiotensin converting enzyme 2 (ACE2) receptors on the cell surface. The infection of host lung cells by SARS-CoV-2 leads to clinical symptoms in patients. However, ACE2 expression is not restricted to the lungs; altered receptors have been found in the nasal and oral mucosa, vessel, brain, pancreas, gastrointestinal tract, kidney, and heart. The future of COVID-19 is uncertain, however, new viral variants are likely to emerge. The SARS-CoV-2 Omicron variant has a total of 50 gene mutations compared with the original virus; 15 of which occur in the receptor binding domain (RBD). The RBD of the viral S-protein binds to the human ACE2 receptor for viral entry. Mutations of the ACE2-RBD interface enhance tight binding by increasing hydrogen bond interactions and expanding the accessible surface area. Extracorporeal membrane oxygenation, hyperbaric oxygen, and aggressive dialysis for the treatment of COVID-19 have shown various degrees of clinical success. The use of decoy receptors based on the ACE2 receptor as a broadly potent neutralizer of SARS-CoV-2 variants has potential as a therapeutic mechanism. Drugs such as 3E8 could block binding of the S1-subunit to ACE2 and restrict the infection of ACE2-expressing cells by a variety of coronaviruses. Here, we discuss the development of ACE2-targeted strategies for the treatment and prevention of COVID-19.

Design, construction and in vivo functional assessment of a hinge truncated sFLT01

Gene therapy for the treatment of ocular neovascularization has reached clinical trial phases. The AAV2-sFLT01 construct was already evaluated in a phase 1 open-label trial administered intravitreally to patients with advanced neovascular age-related macular degeneration. SFLT01 protein functions by binding to VEGF and PlGF molecules and inhibiting their activities simultaneously. It consists of human VEGFR1/Flt-1 (hVEGFR1), a polyglycine linker, and the Fc region of human IgG1. The IgG1 upper hinge region of the sFLT01 molecule makes it vulnerable to radical attacks and prone to causing immune reactions. This study pursued two goals: (i) minimizing the immunogenicity and vulnerability of the molecule by designing a truncated molecule called htsFLT01 (hinge truncated sFLT01) that lacked the IgG1 upper hinge and lacked 2 amino acids from the core hinge region; and (ii) investigating the structural and functional properties of the aforesaid chimeric molecule at different levels (in silico, in vitro, and in vivo). Molecular dynamics simulations and molecular mechanics energies combined with Poisson-Boltzmann and surface area continuum solvation calculations revealed comparable free energy of binding and binding affinity for sFLT01 and htsFLT01 to their cognate ligands. Conditioned media from human retinal pigment epithelial (hRPE) cells that expressed htsFLT01 significantly reduced tube formation in HUVECs. The AAV2-htsFLT01 virus suppressed vascular development in the eyes of newborn mice. The htsFLT01 gene construct is a novel anti-angiogenic tool with promising improvements compared to existing treatments.

Role of Dipeptidyl Peptidase-4 (DPP4) on COVID-19 Physiopathology

DPP4/CD26 is a single-pass transmembrane protein with multiple functions on glycemic control, cell migration and proliferation, and the immune system, among others. It has recently acquired an especial relevance due to the possibility to act as a receptor or co-receptor for SARS-CoV-2, as it has been already demonstrated for other coronaviruses. In this review, we analyze the evidence for the role of DPP4 on COVID-19 risk and clinical outcome, and its contribution to COVID-19 physiopathology. Due to the pathogenetic links between COVID-19 and diabetes mellitus and the hyperinflammatory response, with the hallmark cytokine storm developed very often during the disease, we dive deep into the functions of DPP4 on carbohydrate metabolism and immune system regulation. We show that the broad spectrum of functions regulated by DPP4 is performed both as a protease enzyme, as well as an interacting partner of other molecules on the cell surface. In addition, we provide an update of the DPP4 inhibitors approved by the EMA and/or the FDA, together with the newfangled approval of generic drugs (in 2021 and 2022). This review will also cover the effects of DPP4 inhibitors (i.e., gliptins) on the progression of SARS-CoV-2 infection, showing the role of DPP4 in this disturbing disease.