Capping motifs in antimicrobial peptides and their relevance for improved biological activities.

N-capping (N-cap) and C-capping (C-cap) in biologically active peptides, including specific amino acids or unconventional group motifs, have been shown to modulate activity against pharmacological targets by interfering with the peptide's secondary structure, thus generating unusual scaffolds. The insertion of capping motifs in linear peptides has been shown to prevent peptide degradation by reducing its susceptibility to proteolytic cleavage, and the replacement of some functional groups by unusual groups in N- or C-capping regions in linear peptides has led to optimized peptide variants with improved secondary structure and enhanced activity. Furthermore, some essential amino acid residues that, when placed in antimicrobial peptide (AMP) capping regions, are capable of complexing metals such as Cu2+, Ni2+, and Zn2+, give rise to the family known as metallo-AMPs, which are capable of boosting antimicrobial efficacy, as well as other activities. Therefore, this review presents and discusses the different strategies for creating N- and C-cap motifs in AMPs, aiming at fine-tuning this class of antimicrobials.

Epigenome-Driven Strategies for Personalized Cancer Immunotherapy.

Fighting cancer remains one of the greatest challenges for science in the 21st century. Advances in immunotherapy against different types of cancer have greatly contributed to the treatment, remission, and cure of patients. In this context, knowledge of epigenetic phenomena, their relationship with tumor cells and how the immune system can be epigenetically modulated represent some of the greatest advances in the development of anticancer therapies. Epigenetics is a rapidly growing field that studies how environmental factors can affect gene expression without altering DNA sequence. Epigenomic changes include DNA methylation, histone modifications, and non-coding RNA regulation, which impact cellular function. Epigenetics has shown promise in developing cancer therapies, such as immunotherapy, which aims to stimulate the immune system to attack cancer cells. For example, PD-1 and PD-L1 are biomarkers that regulate the immune response to cancer cells and recent studies have shown that epigenetic modifications can affect their expression, potentially influencing the efficacy of immunotherapy. New therapies targeting epigenetic modifications, such as histone deacetylases and DNA methyltransferases, are being developed for cancer treatment, and some have shown promise in preclinical studies and clinical trials. With growing understanding of epigenetic regulation, we can expect more personalized and effective cancer immunotherapies in the future. This review highlights key advances in the use of epigenetic and epigenomic tools and modern immuno-oncology strategies to treat several types of tumors.

From exploring cancer and virus targets to discovering active peptides through mRNA display.

During carcinogenesis, neoplastic cells accumulate mutations in genes important for cellular homeostasis, producing defective proteins. Viral infections occur when viral capsid proteins bind to the host cell receptor, allowing the virus to enter the cells. In both cases, proteins play important roles in cancer development and viral infection, so these targets can be exploited to develop alternative treatments. mRNA display technology is a very powerful tool for the development of peptides capable of acting on specific targets in neoplastic cells or on viral capsid proteins. mRNA display technology allows the selection and evolution of peptides with desired functional properties from libraries of many nucleic acid variants. Among other advantages of this technology, the use of flexizymes allows the production of peptides with unnatural amino acid residues, which can enhance the activity of these molecules. From target immobilization, peptides with greater specificity for the targets of interest are generated during the selection rounds. Herein, we will explore the use of mRNA display technology for the development of active peptides after successive rounds of selection, using proteins present in neoplastic cells and viral particles as targets.

The LL-37 domain: A clue to cathelicidin immunomodulatory response?

Host defense peptides (HDPs) are naturally occurring polypeptide sequences that, in addition to being active against bacteria, fungi, viruses, and other parasites, may stimulate immunomodulatory responses. Cathelicidins, a family of HDPs, are produced by diverse animal species, such as mammals, fish, birds, amphibians, and reptiles, to protect them against pathogen infections. These peptides have variable C-terminal domains responsible for their antimicrobial and immunomodulatory activities and a highly conserved N-terminal pre-pro region homologous to cathelin. Although cathelicidins are the major components of innate immunity, the molecular basis by which they induce an immune response is still unclear. In this review, we will address the role of the LL-37 domain and its SK-24, IV-20, FK-13 and LL-37 fragments in the immunity response. Other cathelicidins also share structural and functional characteristics with the LL-37 domain, suggesting that these fragments may be responsible for interaction between these peptides and receptors in humans. Fragments of the LL-37 domain can give us clues about how homologous cathelicidins, in general, induce an immune response.

Evaluation of the biotechnological potential of peptide Cupiennin 1a and analogs.

Antimicrobial peptides (AMPs) are components in the innate immune system of various organisms, and many AMPs can be found in poisons from animals such as spiders, scorpions, and snakes. The peptide Cupiennin-1a is present in the venom of the spider Cupiennius salei and belongs to a group of peptides called cupiennins. The peptide demonstrated high cytotoxic activity against mammalian cells; thus, aiming to solve this problem, seven analogs were designed (R1a, R1b, R2b, R3b, R6b, R8b, and R10b) based on the primary structure of the peptide Cupiennin 1a, reducing its size and substituting some amino acid residues. The antimicrobial results showed that all Cupiennin 1a analogs displayed antimicrobial activity against the tested bacterial and fungal strains. Cytotoxicity tests demonstrated a decrease in the cytotoxic effect of the analogs when compared to the peptide Cupiennin-1a. The antitumor activity against breast adenocarcinoma lines was observed for all the peptides, displaying a better effect against the MCF-7 and MDAMB-231 cell lines. The eight peptides have insecticidal potential, and the original peptide and analogs R6b, R8b, and R10b showed better efficiency even at low concentrations. The rational design of the analogs led to new molecules displaying activities against different cell types and reduced cytotoxicity toward healthy mammalian cells when compared to the original peptide, demonstrating that this was an interesting approach for the development of molecules with biotechnological potential.

Screening for cysteine-stabilized scaffolds for developing proteolytic-resistant AMPs.

Antimicrobial peptides (AMP) are present in all organisms and can present several activities and potential applications in human and animal health. Screening these molecules scaffolds represents a key point for discovering and developing novel biotechnological products, including antimicrobial, antiviral and anticancer drugs candidates and insecticidal molecules with potential applications in agriculture. Therefore, considering the amount of biological data currently deposited on public databases, computational approaches have been commonly used to predicted and identify novel cysteine-rich peptides scaffolds with known or unknown biological properties. Here, we describe a step-by-step in silico screening for cysteine-rich peptides employing molecular modeling (with a core focus on comparative modeling) and atomistic molecular dynamics simulations. Moreover, we also present the concept of additional tools aiming at the computer-aided screening of new Cs-AMPs based drug candidates. After the computational screening and peptide chemical synthesis, we also provide the reader with a step-by-step in vitro activity evaluation of these candidates, including antibacterial, antifungal, and antiviral assays.

Co-occurrence of linear and cyclic pelgipeptins in broth cultures of Paenibacillus elgii AC13.

Paenibacillus elgii AC13 produces antimicrobial lipopeptides of agricultural and pharmaceutical importance. It secretes four cyclic lipopeptides named pelgipeptins, previously characterized in P. elgii B69. These lipopeptides result from the expression of a nonribosomal peptide gene cluster. P. elgii AC13 also produced two linear lipopeptides with ratios of [M + H] + 1105 and 1119 m/z. These compounds were previously observed in Paenibacillus sp. strain OSY-N, but due to purification difficulties, their characterization was executed using synthetically produced linear pelgipeptins. In the present study, purification was achieved from the supernatants of cultures from three complex media by high-performance liquid chromatography. The partial characterization of linear pelgipeptins revealed the similar antimicrobial activity and cytotoxicity of their synthetically produced counterparts, known as paenipeptins. Cyclic forms were highly stable to changes in pH, temperature, and organic extraction with n-butanol as shown by mass spectrometry (MALDI-TOF); therefore, these steps did not cause the hydrolysis of pelgipeptins. A low-activity thioesterase could also generate the linear isoforms observed; this enzyme catalyzes the cyclization process and is coded in the same gene cluster. Alternatively, the cyclic forms were hydrolyzed by an unknown protease produced during growth in the complex medium used in the present study. Although culture conditions are known to produce pelgipeptins with different yields and amino acid compositions, the occurrence of linear and cyclic forms simultaneously has not yet been reported. A mixture of cyclic and linear pelgipeptins presents a potential advantage of the higher antimicrobial activity of cyclic forms combined with the lower cytotoxicity of linear isoforms.

Strategies for recombinant production of antimicrobial peptides with pharmacological potential.

INTRODUCTION: The need to develop new drugs for the control of pathogenic microorganisms has redoubled efforts to prospect for antimicrobial peptides (AMPs) from natural sources and to characterize its structure and function. These molecules present a broad spectrum of action against different microorganisms and frequently present promiscuous action, with anticancer and immunomodulatory activities. Furthermore, AMPs can be used as biopharmaceuticals in the treatment of hospital-acquired infections and other serious diseases with relevant social and economic impacts.Areas covered: The low yield and the therefore difficult extraction and purification process in AMPs are problems that limit their industrial application and scientific research. Thus, optimized heterologous expression systems were developed to significantly boost AMP yields, allow high efficiency in purification and structural optimization for the increase of therapeutic activity.Expert opinion: This review provides an update on recent developments in the recombinant production of ribosomal and non-ribosomal synthesis of AMPs and on strategies to increase the expression of genes encoding AMPs at the transcriptional and translational levels and regulation of the post-translational modifications. Moreover, there are detailed reports of AMPs that have already reached marketable status or are in the pipeline under advanced stages of preclinical testing.