Construction of scFv that bind both fibronectin-binding protein A and clumping factor A of Stapylococcus aureus

Relationship between Microflora Changes and Mammary Lipid Metabolism in Dairy Cows with Mastitis

Dairy mastitis is an inflammatory reaction caused by mechanical injury and stress within the mammary gland, during which microbial changes and abnormal lipid metabolism occur. However, the underlying mechanism is still unclear. The present study used a combination of 16S rDNA sequencing technology and lipidomics techniques to reveal the effects of mastitis on lactic microbiota and metabolites in the milk of dairy cows. Twenty multiparous Holstein dairy cows (2-3 parities) with an average body weight of 580 ± 30 kg were selected for this study. The dairy cows were allocated to control group (<5 × 104 cells /mL)) and mastitis group (>5 × 106 cells /mL) based on the somatic cell count. The results showed that mastitis caused a decrease trend in milk production (p = 0.058). The results of the 16 s sequencing indicated a significant decrease (p < 0.05) in the number of Proteobacteria, Tenericutes colonized in mastitis milk, and the number of Firmicutes, Bacteroidetes and Actinobacteria communities increased significantly (p < 0.05). The lipidomics results revealed that the changes in lipid content in mastitis milk were correlated with arachidonic acid metabolism, α -linolenic acid metabolism and glycerol phospholipid metabolism. The results showed that mastitis may cause abnormal lipid metabolism in milk by regulating the diversity of milk microflora, and ultimately affect the milk quality.

Structure-based engineering of an antiangiogenic scFv antibody for soluble production in E. coli without loss of activity

Development of monoclonal antibody therapeutics against vascular endothelial growth factor receptor 2 (VEGFR-2) protein, which is the main regulator in angiogenesis, has been a major challenge for years. In the current study, we engineer an inclusion body forming single-chain variable fragment (scFv) against VEGFR-2 by using complementarity determining regions (CDR) grafting technique to improve its solubility and investigate the activity of the engineered molecule. CDR sequences of the target scFv were grafted into the framework of another intrinsically soluble scFv molecule. Based on the computational results, CDR grafting has increased the solubility of the grafted scFv molecule. Results confirmed that the grafting approach increased in vivo folding properties of the target scFv molecule compared with the original scFv molecule. Similar binding affinities to the VEGFR-2 were observed for the original and the grafted scFv by surface plasmon resonance assays. Biological activity assays, including human umbilical vein endothelial cells proliferation and wound healing assays, showed that grafted scFv molecule has an antiangiogenic property. This study suggests that an antiangiogenic scFv fully expressed as an inclusion body can be rescued by grafting its CDR regions to a scFv expressed in a soluble form without any loss in its binding property and its activity.

Generation and Characterization of a Spike Glycoprotein Domain A-Specific Neutralizing Single-Chain Variable Fragment against Porcine Epidemic Diarrhea Virus

The emergence of the genotype (G) 2 and re-emergence of the G1 porcine epidemic diarrhea virus (PEDV) has caused severe economic impacts in the past decade. Developments of efficient vaccines against new variants of PEDV have been challenging, not least because of the difficulties in eliciting mucosal and lactogenic immunity. A single-chain fragment variable (scFv) capable of efficient antigen recognition is an alternative to vaccination and treatment of a viral infection. In the present study, the variable regions of the light chain and the heavy chain of a G2b PEDV spike domain A (S1^A)-specific neutralizing monoclonal antibody (mAb) were sequenced, constructed with a (G4S) x3 linker, and produced by a mammalian protein expression system. Our results demonstrated that the PEDV S1^A domain scFv was able to bind to S proteins of both G1 and G2b PEDVs. Nevertheless, the scFv was only capable of neutralizing the homologous G2b PEDV but not the G1 PEDV. The binding ability of the G2b-specific neutralizing scFv was not able to predict the neutralizing ability toward heterologous PEDV. The anti-PEDV S1^A scFv presented herein serves as a potential therapeutic candidate against the virulent G2b PEDV.

Developing Recombinant Antibodies by Phage Display Against Infectious Diseases and Toxins for Diagnostics and Therapy

Antibodies are essential molecules for diagnosis and treatment of diseases caused by pathogens and their toxins. Antibodies were integrated in our medical repertoire against infectious diseases more than hundred years ago by using animal sera to treat tetanus and diphtheria. In these days, most developed therapeutic antibodies target cancer or autoimmune diseases. The COVID-19 pandemic was a reminder about the importance of antibodies for therapy against infectious diseases. While monoclonal antibodies could be generated by hybridoma technology since the 70ies of the former century, nowadays antibody phage display, among other display technologies, is robustly established to discover new human monoclonal antibodies. Phage display is an in vitro technology which confers the potential for generating antibodies from universal libraries against any conceivable molecule of sufficient size and omits the limitations of the immune systems. If convalescent patients or immunized/infected animals are available, it is possible to construct immune phage display libraries to select in vivo affinity-matured antibodies. A further advantage is the availability of the DNA sequence encoding the phage displayed antibody fragment, which is packaged in the phage particles. Therefore, the selected antibody fragments can be rapidly further engineered in any needed antibody format according to the requirements of the final application. In this review, we present an overview of phage display derived recombinant antibodies against bacterial, viral and eukaryotic pathogens, as well as microbial toxins, intended for diagnostic and therapeutic applications.

Selected Biological Medicinal Products and Their Veterinary Use

Simple Summary

Biological drugs are a generation of drugs that have developed thanks to advances in genetic engineering and molecular biology. Biological drugs are proteins derived from living cells or obtained through the use of genetic engineering methods with a selective and specific mechanism of action. Currently, these drugs are widely used in the treatment of many human diseases, but an increasing number of drugs from this group are also being used in the treatment of animals, mainly in dermatology, rheumatology and oncology.

Abstract

Definitions of biological medicinal products (BMPs) vary depending on the source. BMPs are manufactured using complex biological/biotechnological processes involving living cell lines, tissues and organisms such as microorganisms, plants, humans and even animals. Advances in modern biotechnological methods and genetic engineering have made it possible to search for new drugs with a targeted effect and simultaneous reduction of adverse effects, which has resulted in BMPs dynamically increasing their share in the pharmaceutical market. Currently, these drugs are widely used in the treatment of many human diseases, but an increasing number of drugs of this group are also being used in the treatment of animals, mainly in dermatology, rheumatology and oncology. This article presents the current state of knowledge in the field of biological medicinal products used in animal therapy.

Construction and characterization of porcine single-chain fragment variable antibodies that neutralize transmissible gastroenteritis virus in vitro

Transmissible gastroenteritis virus (TGEV) infection causes severe diarrhea in piglets and imposes a significant economic burden on pig farms. Single-chain fragment variable (scFv) antibodies effectively inhibit virus infection and could be a potential therapeutic reagent for preventing disease. In this study, a recombinant scFv antibody phage display library was constructed from peripheral blood lymphocytes of piglets infected with TGEV. The library was screened with four rounds of biopanning using purified TGEV antigen, and scFv antibodies that bound to TGEV were obtained. The scFv gene was subcloned into the pET-28a(+), and the constituted plasmid was introduced into Escherichia coli BL21 (DE3) for protein expression. All three scFv clones identified had neutralizing activity against TGEV. An immunofluorescence assay and western blot analysis demonstrated that two scFv antibodies reacted with the spike protein of TGEV. These results indicate that scFv antibodies provide protection against viral infection in vitro and may be a therapeutic candidate for both prevention and treatment of TGEV infection in swine.

The preparation and therapeutic roles of scFv-Fc antibody against Staphylococcus aureus infection to control bovine mastitis

Staphylococcus aureus-induced bovine mastitis causes significant losses to the dairy industry and available vaccines do not confer adequate protection. As a more attractive alternative, we propose the use of antibody (Ab) therapy. In our previous study, we constructed a bovine single-chain variable fragment (scFv) Ab phage display and successfully obtained scFvs that bound to S. aureus antigens with high affinity. Here, we describe a novel Ab against S. aureus (scFv-Fc Ab). To construct the scFv-Fc Ab, the scFv Ab was genetically fused to the Fc fragment of a bovine IgG1 Ab. Western blot analysis showed that the bovine scFvs-Fc Abs were successfully expressed with horseradish peroxidase-conjugated goat-anti-bovine IgG (Fc) Ab in Escherichia coli cells. The purified bovine scFvs-Fc Abs had good binding activity to S. aureus and effectively inhibited the bacterial growth in culture medium and bovine scFvs-Fc Abs enhanced phagocytosis of S. aureus by neutrophils isolated from peripheral blood in a dose-dependent manner. In the experiment of bovine scFvs-Fc Abs for the treatment of S. aureus-induced bovine mastitis, the total effective percentage reached 82% (9/11). These novel bovine scFvs-Fc Abs may be useful as therapeutic candidates for the prevention and treatment of S. aureus-induced bovine mastitis.

Recombinant Antibodies in Veterinary Medicine: An Update

The production of recombinant antibodies has had a tremendous impact on several research fields, most prominently in biotechnology, immunology and medicine, enabling enormous advances in each. Thus far, a broad diversity of recombinant antibody (rAb) forms have been designed and expressed using different expression systems. Even though the majority of rAbs approved for clinical use are targeted to humans, advances in veterinary medicine seem promising. The aim of this mini-review is to present an update regarding the rAbs in veterinary medicine reported to date, as well as their potential use in diagnostics, prophylaxis and therapeutics. Full- and single-chain fragment variables are the most common forms of rAbs developed for the detection, prevention and control of parasitic, bacterial and viral diseases, as well as pain and cancer treatment. Nonetheless, advances in research seem to be skewed toward economically important animals, such as pigs, cows, poultry and dogs. Although significant results have been obtained from the rAbs reported here, most have not been developed enough to be approved. Further research and clinical trials should be encouraged to enable important findings to fulfill their intended potential to improve animal well-being.

Trends in recombinant protein use in animal production

Recombinant technologies have made possible the production of a broad catalogue of proteins of interest, including those used for animal production. The most widely studied proteins for the animal sector are those with an important role in reproduction, feed efficiency, and health. Nowadays, mammalian cells and fungi are the preferred choice for recombinant production of hormones for reproductive purposes and fibrolytic enzymes to enhance animal performance, respectively. However, the development of low-cost products is a priority, particularly in livestock. The study of cell factories such as yeast and bacteria has notably increased in the last decades to make the new developed reproductive hormones and fibrolytic enzymes a real alternative to the marketed ones. Important efforts have also been invested to developing new recombinant strategies for prevention and therapy, including passive immunization and modulation of the immune system. This offers the possibility to reduce the use of antibiotics by controlling physiological processes and improve the efficacy of preventing infections. Thus, nowadays different recombinant fibrolytic enzymes, hormones, and therapeutic molecules with optimized properties have been successfully produced through cost-effective processes using microbial cell factories. However, despite the important achievements for reducing protein production expenses, alternative strategies to further reduce these costs are still required. In this context, it is necessary to make a giant leap towards the use of novel strategies, such as nanotechnology, that combined with recombinant technology would make recombinant molecules affordable for animal industry.

Anti-Staphylococcus aureus single-chain variable region fragments provide protection against mastitis in mice

Staphylococcus aureus is a leading causative agent of bovine mastitis, which can result in significant economic losses to the dairy industry. However, available vaccines against bovine mastitis do not confer adequate protection, although passive immunization with antibodies may be useful to prevent disease. Hence, we constructed a bovine single-chain variable region fragment (scFv) phage display library using cDNAs from peripheral blood lymphocytes of cows with S. aureus-induced mastitis. After four rounds of selection, eight scFvs that bound S. aureus antigens with high affinity were obtained. The framework regions of the variable domains (VH and VL) of the eight scFvs were highly conserved, and the complementarity-determining regions (CDRs) displayed significant diversity, especially CDR3 of the VH domain. All eight scFvs inhibited S. aureus growth in culture medium. Lactating mice were challenged by injecting S. aureus into the fourth mammary gland. Histopathological analysis showed that treatment with these scFvs prior to bacterial challenge maintained the structure of the mammary acini, decreased infiltration of polymorphonuclear neutrophils, increased levels of interferon-gamma and interleukin-4, and reduced tumor necrosis factor-alpha levels in mammary tissues, as compared with mice treatment with physiological saline (P < 0.05). These novel bovine scFvs may be suitable candidates for therapeutic agents for the prevention of S. aureus-induced bovine mastitis.