In vivo targeted delivery of CD40 shRNA to mouse intestinal dendritic cells by oral administration of recombinant Sacchromyces cerevisiae

Genetically engineering of Saccharomyces cerevisiae for enhanced oral delivery vaccine vehicle

As a series of our previous studies reported, recombinant yeast can be the oral vaccines to deliver designed protein and DNA, as well as functional shRNA, into dendritic cells (DCs) in mice for specific immune regulation. Here, we report the further optimization of oral yeast-based vaccine from two aspects (yeast characteristics and recombinant DNA constitution) to improve the effect of immune regulation. After screening four genes in negative regulation of glucan synthesis in yeast (MNN9, GUP1, PBS2 and EXG1), this research combined HDR-based genome editing technology with Cre-loxP technology to acquire 15 gene-knockout strains without drug resistance-gene to exclude biosafety risks; afterward, oral feeding experiments were performed on the mice using 15 oral recombinant yeast-based vaccines constructed by the gene-knockout strains harboring pCMV-MSTN plasmid to screen the target strain with more effective inducing mstn-specific antibody which in turn increasing weight gain effect. And subsequently based on the selected gene-knockout strain, the recombinant DNA in the oral recombinant yeast-based vaccine is optimized via a combination of protein fusion expression (OVA-MSTN) and interfering RNA technology (shRNA-IL21), comparison in terms of both weight gain effect and antibody titer revealed that the selected gene-knockout strain (GUP1ΔEXG1Δ) combined with specific recombinant DNA (pCMV-OVA-MSTN-shIL2) had a better effect of the vaccine. This study provides a useful reference to the subsequent construction of a more efficient oral recombinant yeast-based vaccine in the food and pharmaceutical industry.

Oral delivery of RNAi for cancer therapy

Cancer is a major health concern worldwide and is still in a continuous surge of seeking for effective treatments. Since the discovery of RNAi and their mechanism of action, it has shown promises in targeted therapy for various diseases including cancer. The ability of RNAi to selectively silence the carcinogenic gene makes them ideal as cancer therapeutics. Oral delivery is the ideal route of administration of drug administration because of its patients' compliance and convenience. However, orally administered RNAi, for instance, siRNA, must cross various extracellular and intracellular biological barriers before it reaches the site of action. It is very challenging and important to keep the siRNA stable until they reach to the targeted site. Harsh pH, thick mucus layer, and nuclease enzyme prevent siRNA to diffuse through the intestinal wall and thereby induce a therapeutic effect. After entering the cell, siRNA is subjected to lysosomal degradation. Over the years, various approaches have been taken into consideration to overcome these challenges for oral RNAi delivery. Therefore, understanding the challenges and recent development is crucial to offer a novel and advanced approach for oral RNAi delivery. Herein, we have summarized the delivery strategies for oral delivery RNAi and recent advancement towards the preclinical stages.

RNA Vaccines: Yeast as a Novel Antigen Vehicle

In the last decades, technological advances for RNA manipulation enabled and expanded its application in vaccine development. This approach comprises synthetic single-stranded mRNA molecules that direct the translation of the antigen responsible for activating the desired immune response. The success of RNA vaccines depends on the delivery vehicle. Among the systems, yeasts emerge as a new approach, already employed to deliver protein antigens, with efficacy demonstrated through preclinical and clinical trials. β-glucans and mannans in their walls are responsible for the adjuvant property of this system. Yeast β-glucan capsules, microparticles, and nanoparticles can modulate immune responses and have a high capacity to carry nucleic acids, with bioavailability upon oral immunization and targeting to receptors present in antigen-presenting cells (APCs). In addition, yeasts are suitable vehicles for the protection and specific delivery of therapeutic vaccines based on RNAi. Compared to protein antigens, the use of yeast for DNA or RNA vaccine delivery is less established and has fewer studies, most of them in the preclinical phase. Here, we present an overview of the attributes of yeast or its derivatives for the delivery of RNA-based vaccines, discussing the current challenges and prospects of this promising strategy.

Immunomodulatory effect and safety of TNF-α RNAi mediated by oral yeast microcapsules in rheumatoid arthritis therapy

Rheumatoid arthritis (RA) is a chronic autoimmune disease that requires long-term treatment and monitoring. Inhibition of inflammatory gene expression by gene therapy is a significant breakthrough in RA treatment, but the lack of a safe and effective gene delivery system hinders its application. Since oral administration can significantly reduce wound infection caused by parenteral administration, it also has the advantages of high patient compliance and convenience. Therefore, oral administration may be the best option for the treatment of this chronic disease. In this study, we developed a novel oral drug system by delivering tumor necrosis factor-α (TNF-α) short hairpin RNA (shRNA) mediated by non-pathogenic yeast to evaluate its regulation of systemic immune inflammation and safety in RA. Non-pathogenic yeast can resist the destruction of the gastrointestinal acid-base environment and can be recognized by the intestinal macrophages and act on systemic inflammatory lesions. Oral administration of yeast-mediated TNF-α shRNA significantly reduced the expression of TNF-α predominant pro-inflammatory factors in intestinal macrophages and joint synovium, and up-regulated the expression of anti-inflammatory cytokine IL-10 and M2 macrophages, systematically regulating the inflammatory response. This yeast-mediated oral gene delivery system can not only significantly inhibit knee joint synovial inflammation, but also has no toxic effects on peripheral blood and major organs. Therefore, yeast-mediated oral delivery of TNF-α shRNA may be used as a novel gene therapy strategy to treat RA through immunomodulating the mononuclear phagocyte system from the intestine to the joint synovium, and ultimately regulating systemic and local immune inflammation, providing new ideas for the clinical treatment of RA.

In vivo Protein Interference: Oral Administration of Recombinant Yeast-Mediated Partial Leptin Reduction for Obesity Control

Obesity-related diseases are always the major health problems that concern the whole world. Serial studies have reported that obesity development is closely related to the out-of-control leptin encoded by the obesity gene (ob). The latest report declaimed “Less Is More,” a model explaining that partial leptin reduction triggers leptin sensitization and contributes to obesity control. Here, we came up with a novel concept, in vivo protein interference (iPRTi), an interesting protein knock-down strategy for in vivo partial leptin reduction. First, the specific immune response against leptin induced by the oral administration of ob recombinant yeast was confirmed. Subsequentally, leptin resistance was observed in diet-induced obese mice, and oral administration with ob recombinant yeast declined the circulating leptin and reduced significantly the body weight gain. To further investigate whether the iPRTi strategy is capable of obesity management, the diet-induced obese mice were administrated with ob recombinant yeast. All the indexes examined including the circulating leptin, triglyceride, and total cholesterol, as well as food intake and weight gain, demonstrated a positive effect of the iPRTi strategy on obesity control. In short, this study provides a novel strategy for the potential application of recombinant yeast for the therapy of obese individuals with leptin resistance.

Yeast as carrier for drug delivery and vaccine construction

Yeast has been employed as an effective derived drug carrier as a unicellular microorganism. Many research works have been devoted to the encapsulation of nucleic acid compounds, insoluble small molecule drugs, small molecules, liposomes, polymers, and various nanoparticles in yeast for the treatment of disease. Recombinant yeast-based vaccine carriers (WYV) have played a major role in the development of vaccines. Herein, the latest reports on the application of yeast carriers and the development of related research are summarized, a conceptual description of gastrointestinal absorption of yeast carriers, as well as the various package forms of different drug molecules and nanoparticles in yeast carriers are introduced. In addition, the advantages and development of recombinant yeast vaccine carriers for the disease, veterinary and aquaculture applications are discussed. Moreover, the current challenges and future directions of yeast carriers are proposed.

Advances in the Development of Microbial Double-Stranded RNA Production Systems for Application of RNA Interference in Agricultural Pest Control

RNA interference (RNAi) is a valuable and revolutionary technology that has been widely applied in medicine and agriculture. The application of RNAi in various industries requires large amounts of low-cost double-stranded RNA (dsRNA). Chemical synthesis can only produce short dsRNAs; long dsRNAs need to be synthesized biologically. Several microbial chassis cells, such as Escherichia coli, Saccharomyces cerevisiae, and Bacillus species, have been used for dsRNA synthesis. However, the titer, rate of production, and yield of dsRNA obtained by these microorganism-based strategies is still low. In this review, we summarize advances in microbial dsRNA production, and analyze the merits and faults of different microbial dsRNA production systems. This review provides a guide for dsRNA production system selection. Future development of efficient microbial dsRNA production systems is also discussed.

Oral Gene Therapy of HFD-Obesity via Nonpathogenic Yeast Microcapsules Mediated shRNA Delivery

Obesity is a chronic systemic inflammatory disease, which occurs when energy intake exceeds the energy consumption. Therefore, controlling energy intake or increasing physical consumption can effectively control obesity. However, in reality, it is very difficult for the majority of obese patients to lose weight by autonomously controlling diet. In this study, oral shRNA/yeast microcapsules were constructed with non-virus-mediated IL-1β shRNA interference vectors and non-pathogenic Saccharomyces cerevisiae. Moreover, high-fat diet induced obese mice were established to assess the weight loss effect of IL-1β shRNA/yeast microcapsules via the oral route. After IL-1β shRNA/yeast treatment, body weight and fat weight was reduced. Compared with the control group, higher average food intake but lower energy conversion rate was observed in IL-1β shRNA/yeast group. In addition, lipid metabolism related cytokines and blood glucose concentration in the circulating blood was improved after IL-1β shRNA/yeast treatment. Yeast microcapsules mediated IL-1β shRNA delivery can effectively improve obesity. Noteworthy, this kind of non-diet-controlled weight loss strategy does not need diet control, and shows good biocompatibility. It is good news to obese patients who need to lose weight but cannot control their diet.

Yeasts as a promising delivery platform for DNA and RNA vaccines

Yeasts are considered a useful system for the development of vaccines for human and veterinary health. Species such as Saccharomyces cerevisiae and Pichia pastoris have been used successfully as host organisms for the production of subunit vaccines. These organisms have been also explored as vaccine vehicles enabling the delivery of antigens such as proteins and nucleic acids. The employed species possess a GRAS status (Generally Recognized as Safe) for the production of therapeutic proteins, besides promoting immunostimulation due to the properties of their wall cell composition. This strategy allows the administration of nucleic acids orally and a specific delivery to professional antigen-presenting cells (APCs). In this review, we seek to outline the development of whole yeast vaccines (WYV) carrying nucleic acids in different approaches in the medical field, as well as the immunological aspects of this vaccine strategy. The data presented here reveal the application of this platform in promoting effective immune responses in the context of prophylactic and therapeutic approaches.

Yeast microcapsule-mediated oral delivery of IL-1β shRNA for post-traumatic osteoarthritis therapy

Post-traumatic osteoarthritis is a prevalent debilitating joint disease. However, there is no FDA-approved disease-modifying osteoarthritis drug currently. Gene therapy can improve disease progression but lacks an effective delivery system. Here, we constructed an oral drug delivery system by non-virus-mediated interleukin-1β (IL-1β) short hairpin RNA (shRNA) and non-pathogenic yeast to evaluate its effect on osteoarthritis therapy. After recombinant IL-1β shRNA/yeast therapy, yeast microcapsule-mediated oral delivery of IL-1β shRNA greatly reduced the IL-1β expression in intestine macrophage, bone marrow macrophage, and articular cartilage, systematically regulate the inflammatory response. The degeneration of articular cartilage was significantly inhibited in the medial femoral condyle and medial tibial plateau of the knee joint. And the expression of osteoarthritis markers Col X and MMP13 was reduced in the knee joint. Thus, yeast microcapsule-mediated oral delivery of IL-1β shRNA may serve as a novel gene therapy strategy for treating joint degeneration through immunomodulation of the mononuclear phagocyte system from the intestine to subchondral bone marrow and ultimately preserving the articular cartilage joint.

Paving the Road for RNA Therapeutics

Therapeutic RNA molecules possess high potential for treating medical conditions if they can successfully reach the target cell upon administration. However, unmodified RNA molecules are rapidly degraded and cleared from the circulation. In addition, their large size and negative charge complicates their passing through the cell membrane. The difficulty of RNA therapy, therefore, lies in the efficient intracellular delivery of intact RNA molecules to the tissue of interest without inducing adverse effects. Here, we outline the recent developments in therapeutic RNA delivery and discuss the wide potential in manipulating the function of cells with RNAs. The focus is not only on the variety of delivery strategies but also on the versatile nature of RNA and its wide applicability. This wide applicability is especially interesting when considering the modular nature of nucleic acids. An optimal delivery vehicle, therefore, can facilitate numerous clinical applications of RNA.

Saccharomyces cerevisiae (Baker's Yeast) as an Interfering RNA Expression and Delivery System

The broad application of RNA interference for disease prevention is dependent upon the production of dsRNA in an economically feasible, scalable, and sustainable fashion, as well as the identification of safe and effective methods for RNA delivery. Current research has sparked interest in the use of Saccharomyces cerevisiae for these applications. This review examines the potential for commercial development of yeast interfering RNA expression and delivery systems. S. cerevisiae is a genetic model organism that lacks a functional RNA interference system, which may make it an ideal system for expression and accumulation of high levels of recombinant interfering RNA. Moreover, recent studies in a variety of eukaryotic species suggest that this microbe may be an excellent and safe system for interfering RNA delivery. Key areas for further research and development include optimization of interfering RNA expression in S. cerevisiae, industrial-sized scaling of recombinant yeast cultures in which interfering RNA molecules are expressed, the development of methods for large-scale drying of yeast that preserve interfering RNA integrity, and identification of encapsulating agents that promote yeast stability in various environmental conditions. The genetic tractability of S. cerevisiae and a long history of using this microbe in both the food and pharmaceutical industry will facilitate further development of this promising new technology, which has many potential applications of medical importance.

Yeast Cell wall Particle mediated Nanotube-RNA delivery system loaded with miR365 Antagomir for Post-traumatic Osteoarthritis Therapy via Oral Route

Post-traumatic osteoarthritis (PTOA) is an acute injury-induced joint inflammation followed by a gradual degradation of articular cartilage. However, there is no FDA-approved Disease-Modifying Osteoarthritis Drug currently. Although gene therapy with microRNA can improve PTOA progression, there is no effective gene delivery vehicle for orally deliver therapeutics due to the harsh environment of the gastrointestinal tract. In this study, we investigated the effect of yeast cell wall particle (YCWP) mediated nanotube-RNA delivery system on PTOA therapy via oral route. Methods: Nontoxic and degradable AAT and miRNA365 antagomir was self-assembled into miR365 antagomir/AAT (NPs). Then NPs-YCWP oral drug delivery system was constructed by using NPs and non-pathogenic YCWP which can be specifically recognized by macrophages. Moreover, surgical destabilization of the medial meniscus induced PTOA mice model was established to evaluate the therapeutic effect of NPs-YCWP via oral route. Results: Compared with control group, NPs showed higher gene inhibition efficiency both in chondrogenic cell line and primary chondrocytes in vitro. Treatment of macrophages with fluorescently labeled NPs-YCWP, the results showed that NPs-YCWP was successfully engulfed by macrophages and participated in the regulation of gene expression in vitro. Under the protection of YCWP, miR365 antagomir/AAT passes through the gastrointestinal tract without degradation after oral administration. After NPs-YCWP therapy, the results of histological staining, gene and protein expression showed that miR365 antagomir/NPs-YCWP improved the symptom of PTOA. Conclusion: Here, we constructed a biodegradable drug delivery system based on non-pathogenic YCWP and nanotubes, which can be used for PTOA therapy via the oral route. It suggests a new gene therapy strategy with YCWP mediated oral nano drug delivery system may serve as a platform for joint degeneration treatment.

Significant body mass increase by oral administration of a cascade of shIL21-MSTN yeast-based DNA vaccine in mice

Base on the practical of MSTN-specific yeast-based protein vaccine in mice as described previously, this research was designed for developing a better DNA vaccine (a cascade of shIL21-MSTN yeast-based DNA vaccine) than solely MSTN yeast-based DNA vaccine to block the endogenous MSTN in the murine model. We first constructed the target vectors, including CMV-driven MSTN expression vector and a combined shIL21-MSTN vector which containing MSTN expression cassette and shIL21 (short hairpin RNA-IL21) expression cassette. After necessary validation, recombinant yeast vaccines harboring different vectors were well prepared. Subsequently, after 2-month administration, the MSTN-specific immune response was detected with western blots. The commercial ELISA assays indicated that the production of IL21 and IL6 were decreased compared with control groups. More importantly, the MSTN-specific antibody titer was much higher in the shIL21-MSTN group than MSTN group, which was consistent with the western blots result. The most important finding was significant body mass increased after oral administration of these yeast-based DNA vaccines, in which the shIL21-MSTN vaccine is slightly higher than the sole MSTN vaccine in mice. In this study, we confirmed the role of different MSTN-specific yeast-based DNA vaccines on increasing body mass in mice, to provide a good inspiration for livestock breeding through the new type of immunoregulatory method. On the other hand, we also detected the possible modulating role of shIL21 on the dendritic cell-mediated immune function which needs more practical application and deeper exploration.

Oral yeast-based DNA vaccine confers effective protection from Aeromonas hydrophila infection on Carassius auratus

Our previous study has demonstrated that recombinant yeast can induce specific immune responses in Carassius auratus and may serve as a potential carrier for oral DNA vaccines in aquaculture. In this study, we further developed an effective yeast-based oral DNA vaccine against the bacteria Aeromonas hydrophila, which was expected to provide protection from the motile aeromonad septicemia (MAS). First, two candidate antigen genes, ompG and omp48, were cloned from the Aeromonas hydrophila genome DNA. Then, relative yeast-eukaryote shuttle vectors were constructed and their expression in eukaryotes was validated. Next, crucian carps were orally administered with ompG or omp48 recombinant yeast, and the expression of the genes in the intestinal mucosa was confirmed by immunohistochemistry (IHC). The specific immune responses were further detected by Western blot and enzyme-linked immunosorbent assay (ELISA). The ELISA results showed that the production of the OVA-specific antibody in the OVA-ompG group was significantly higher than that of the OVA-omp48 group, indicating that the OVA-ompG group elicited obviously stronger immune response than OVA-omp48. Finally, the challenge experiment against Aeromonas hydrophila infection demonstrated decreased fish mortality rate after the oral administration of the OVA-ompG yeast vaccine. In conclusion, our work provided a framework for the further development of oral yeast-based fishery vaccines.

Biomedical applications of yeast- a patent view, part one: yeasts as workhorses for the production of therapeutics and vaccines

INTRODUCTION

Yeasts, as Eukaryotes, offer unique features for ease of growth and genetic manipulation possibilities, making it an exceptional microbial host. Areas covered: This review provides general and patent-oriented insights into production of biopharmaceuticals by yeasts. Patents, wherever possible, were correlated to the original or review articles. The review describes applications of major GRAS (generally regarded as safe) yeasts for the production of therapeutic proteins and subunit vaccines; additionally, immunomodulatory properties of yeast cell wall components were reviewed for use of whole yeast cells as a new vaccine platform. The second part of the review will discuss yeast- humanization strategies and innovative applications. Expert opinion: Biomedical applications of yeasts were initiated by utilization of Saccharomyces cerevisiae, for production of leavened (fermented) products, and advanced to serve to produce biopharmaceuticals. Higher biomass production and expression/secretion yields, more similarity of glycosylation patterns to mammals and possibility of host-improvement strategies through application of synthetic biology might enhance selection of Pichia pastoris (instead of S. cerevisiae) as a host for production of biopharmaceutical in future. Immunomodulatory properties of yeast cell wall β-glucans and possibility of intracellular expression of heterologous pathogen/tumor antigens in yeast cells have expanded their application as a new platform, 'Whole Yeast Vaccines'.

Multiplex CRISPR/Cas9-based genome engineering enhanced by Drosha-mediated sgRNA-shRNA structure

The clustered regularly interspaced short palindromic repeats (CRISPR) system has recently been developed into a powerful genome-editing technology, as it requires only two key components (Cas9 protein and sgRNA) to function and further enables multiplex genome targeting and homology-directed repair (HDR) based precise genome editing in a wide variety of organisms. Here, we report a novel and interesting strategy by using the Drosha-mediated sgRNA-shRNA structure to direct Cas9 for multiplex genome targeting and precise genome editing. For multiplex genome targeting assay, we achieved more than 9% simultaneous mutant efficiency for 3 genomic loci among the puromycin-selected cell clones. By introducing the shRNA against DNA ligase IV gene (LIG4) into the sgRNA-shRNA construct, the HDR-based precise genome editing efficiency was improved as more than 2-fold. Our works provide a useful tool for multiplex and precise genome modifying in mammalian cells.

SiRNA In Vivo-Targeted Delivery to Murine Dendritic Cells by Oral Administration of Recombinant Yeast

SiRNA therapeutics promise a future where any target in the transcriptome could be potentially addressed. However, the delivery of SiRNAs and targeting of particular cell types or organs are major challenges. A novel, efficient, and safe delivery system for promising the introduction of SiRNAs into particular cell types within living organisms is of great significance. Our previous studies have proved that recombinant protein (MSTN) and exogenous gene (EGFP) as vaccines, and furthermore functional CD40 shRNA expression can be delivered into dendritic cells (DCs) in mouse by oral administration of recombinant yeast (Saccharomyces cerevisiae). Here, we describe the details of the promising and innovative approach based on oral administration of recombinant yeast that allows in vivo-targeted delivery of functional SiRNA to murine intestinal DCs.

Multiscale analysis of the murine intestine for modeling human diseases

When functioning properly, the intestine is one of the key interfaces between the human body and its environment. It is responsible for extracting nutrients from our food and excreting our waste products. It provides an environment for a host of healthful microbes and serves as a first defense against pathogenic ones. These processes require tight homeostatic controls, which are provided by the interactions of a complex mix of epithelial, stromal, neural and immune cells, as well as the resident microflora. This homeostasis can be disrupted by invasive microbes, genetic lesions, and carcinogens, resulting in diseases such Clostridium difficile infection, inflammatory bowel disease (IBD) and cancer. Enormous strides have been made in understanding how this important organ functions in health and disease using everything from cell culture systems to animal models to human tissue samples. This has resulted in better therapies for all of these diseases, but there is still significant room for improvement. In the United States alone, 14,000 people per year die of C. difficile, up to 1.6 million people suffer from IBD, and more than 50,000 people die every year from colon cancer. Because these and other intestinal diseases arise from complex interactions between the different components of the gut ecosystem, we propose that systems approaches that address this complexity in an integrative manner may eventually lead to improved therapeutics that deliver lasting cures. This review will discuss the use of systems biology for studying intestinal diseases in vivo with particular emphasis on mouse models. Additionally, it will focus on established experimental techniques that have been used to drive this systems-level analysis, and emerging techniques that will push this field forward in the future.

Recombinant Saccharomyces cerevisiae serves as novel carrier for oral DNA vaccines in Carassius auratus

Oral delivery of DNA vaccines represents a promising vaccinating method for fish. Recombinant yeast has been proved to be a safe carrier for delivering antigen proteins and DNAs to some species in vivo. However, whether recombinant yeast can be used to deliver functional DNAs for vaccination to fish is still unknown. In this study, red crucian carp (Carassius auratus) was orally administrated with recombinant Saccharomyces cerevisiae harboring CMV-EGFP expression cassette. On day 5 post the first vaccination, EGFP expression in the hindgut was detected under fluorescence microscope. To further study whether the delivered gene could induce specific immune responses, the model antigen ovalbumin (OVA) was used as immunogen, and oral administrations were conducted with recombinant S. cerevisiae harboring pCMV-OVA mammalian gene expression cassette as gene delivery or pADH1-OVA yeast gene expression cassette as protein delivery. Each administration was performed with three different doses, and the OVA-specific serum antibody was detected in all the experimental groups by western blotting and enzyme-linked immunosorbent assay (ELISA). ELISA assay also revealed that pCMV-OVA group with lower dose (pCMV-OVA-L) and pADH1-OVA group with moderate dose (pADH1-OVA-M) triggered relatively stronger antibody response than the other two doses. Moreover, the antibody level induced by pCMV-OVA-L group was significantly higher than pADH1-OVA-M group at the same serum dilutions. All the results suggested that recombinant yeast can be used as a potential carrier for oral DNA vaccines and would help to develop more practical strategies to control infectious diseases in aquaculture.

An Animal Model of Trichloroethylene-Induced Skin Sensitization in BALB/c Mice

Trichloroethylene (TCE) is a major occupational hazard and environmental contaminant that can cause multisystem disorders in the form of occupational medicamentosa-like dermatitis. Development of dermatitis involves several proinflammatory cytokines, but their role in TCE-mediated dermatitis has not been examined in a well-defined experimental model. In addition, few animal models of TCE sensitization are available, and the current guinea pig model has apparent limitations. This study aimed to establish a model of TCE-induced skin sensitization in BALB/c mice and to examine the role of several key inflammatory cytokines on TCE sensitization. The sensitization rate of dorsal painted group was 38.3%. Skin edema and erythema occurred in TCE-sensitized groups, as seen in 2,4-dinitrochlorobenzene (DNCB) positive control. Trichloroethylene sensitization-positive (dermatitis [+]) group exhibited increased thickness of epidermis, inflammatory cell infiltration, swelling, and necrosis in dermis and around hair follicle, but ear painted group did not show these histological changes. The concentrations of serum proinflammatory cytokines including tumor necrosis factor (TNF)-α, interferon (IFN)-γ, and interleukin (IL)-2 were significantly increased in 24, 48, and 72 hours dermatitis [+] groups treated with TCE and peaked at 72 hours. Deposition of TNF-α, IFN-γ, and IL-2 into the skin tissue was also revealed by immunohistochemistry. We have established a new animal model of skin sensitization induced by repeated TCE stimulations, and we provide the first evidence that key proinflammatory cytokines including TNF-α, IFN-γ, and IL-2 play an important role in the process of TCE sensitization.

Alternative methods for the efficient construction of short hairpin RNA expression vectors

Short hairpin RNA (shRNA)-mediated RNA interference has become a basic technique in modern molecular biology and biochemistry for studying gene function and biological pathways. Here, we report two alternative and efficient methods to construct shRNA expression vectors based respectively on multiple-step sequential PCR and primer extension-homologous recombination (PE-HR). Neither method requires synthesizing long oligonucleotides containing hairpin sequences as used in traditional approaches. The hairpin sequences may produce mutations during oligo synthesis, pose problems in annealing, and lead to inefficient cloning. The PE-HR method further provides rapid and economical construction of shRNA expression vectors without needing the ligation procedure.