Targeted innovative design of Bt Cry toxin insecticidal mimics / 生物工程学报

Bt Cry toxin is the mostly studied and widely used biological insect resistance protein, which plays a leading role in the green control of agricultural pests worldwide. However, with the wide application of its preparations and transgenic insecticidal crops, the resistance to target pests and potential ecological risks induced by the drive are increasingly prominent and attracting much attention. The researchers seek to explore new insecticidal protein materials that can simulate the insecticidal function of Bt Cry toxin. This will help to escort the sustainable and healthy production of crops, and relieve the pressure of target pests' resistance to Bt Cry toxin to a certain extent. In recent years, the author's team has proposed that Ab2β anti-idiotype antibody has the property of mimicking antigen structure and function based on the "Immune network theory" of antibody. With the help of phage display antibody library and specific antibody high-throughput screening and identification technology, Bt Cry toxin antibody was designed as the coating target antigen, and a series of Ab2β anti-idiotype antibodies (namely Bt Cry toxin insecticidal mimics) were screened from the phage antibody library. Among them, the lethality of Bt Cry toxin insecticidal mimics with the strongest activity was close to 80% of the corresponding original Bt Cry toxin, showing great promise for the targeted design of Bt Cry toxin insecticidal mimics. This paper systematically summarized the theoretical basis, technical conditions, research status, and discussed the development trend of relevant technologies and how to promote the application of existing achievements, aiming to facilitate the research and development of green insect-resistant materials.

Screening and identification of single-chain fragment variable against the receptor-binding domain of spike protein of SARS-CoV-2 / 中国生物制品学杂志

@#Objective To construct a single-chain fragment variable(scFv)phage display library against receptor-binding domain(RBD)of severe acute respiratory syndrome coronavirus 2(SARS-CoV-2)spike protein(S)to screen specific scFv and identify the function.Methods m RNA was extracted from spleen cells of mice immunized with RBD protein and reversely transcribed into c DNA,with which as template,genes of the hight chain fragment of variable(VH)and light chain fragment of variable(VL)of scFv were amplified and then assembled into scFv gene fragment through splicing overlap extension PCR(SOE-PCR).The scFv gene fragment was inserted to phage vector to construct scFv phage display library.After four rounds of biopanning,the scFv gene with strong binding ability to RBD was screened and expressed recombinantly,purified and identified for biological activity.Results The constructed scFv phage library showed a titer of 6.0×10(11)pfu/m L.After four rounds of biopanning,four scFv strains with strong binding to RBD were selected,namely scFv11,scFv12,scFv25and scFv28.scFv was mainly expressed in the form of inclusion body with a relative molecular mass of about 27 000,a concentration of 2.4 mg/m L and a purity of about 90%,which bound specifically to mouse monoclonal antibody against His labeled by HRP after purification.All four scFv strains bound specifically to RBD recombinant protein,among which the other 3 scFv strains bound to the S protein of wild type and multiple mutant strains except scFv28.All four strains showed dose-dependent interaction with RBD,with affinity dynamic fitting dissociation constants(K_Ds)8.9,5.92,10.67and 2.36 nmol/L,and steady-state fitting dissociation constants(K_Ds)of 5.3,6.5,8.7 and 5.8 nmol/L,respectively.scFv11,scFv12 and scFv25 simultaneously identified three independent RBD polypeptides,including RBD2(S(11)pfu/m L.After four rounds of biopanning,four scFv strains with strong binding to RBD were selected,namely scFv11,scFv12,scFv25and scFv28.scFv was mainly expressed in the form of inclusion body with a relative molecular mass of about 27 000,a concentration of 2.4 mg/m L and a purity of about 90%,which bound specifically to mouse monoclonal antibody against His labeled by HRP after purification.All four scFv strains bound specifically to RBD recombinant protein,among which the other 3 scFv strains bound to the S protein of wild type and multiple mutant strains except scFv28.All four strains showed dose-dependent interaction with RBD,with affinity dynamic fitting dissociation constants(K_Ds)8.9,5.92,10.67and 2.36 nmol/L,and steady-state fitting dissociation constants(K_Ds)of 5.3,6.5,8.7 and 5.8 nmol/L,respectively.scFv11,scFv12 and scFv25 simultaneously identified three independent RBD polypeptides,including RBD2(S(334～353)),RBD9(S(334～353)),RBD9(S(439～458))and RBD13(S(439～458))and RBD13(S(499～518)).Homologous model of scFv constructed by online server SWISS-MODEL showed a good quality and was used for molecular docking.The interface at which scFv11 interacted with RBD only partially coincided with the interaction interface of human angiotensin converting enzyme 2(ACE2)and RBD,and the interaction interfaces of scFv12 and scFv25 with RBD were quite different from that of ACE2.Conclusion In this study,scFv specifically bound to SARS-Co V-2 RBD was screened and prepared through constructing scFv phage library against SARS-CoV-2 RBD,which provided experimental basis for further development of anti-SARS-CoV-2 drugs and detection reagents.

Screening and identification of CD44v9 specific peptide ligand for gastric cancer detection / 西安交通大学学报(医学版)

【Objective】 To screen and verify a peptide ligand specific for CD44v9. 【Methods】 A 12-mer phage peptide library was screened on CD44v9 coated on solid phase. Candidate sequences emerged after sequencing. Candidate phages were selected using enzyme-linked immunosorbent assay. The best sequence was chosen for further study. Binding of C9-3 to CD44v overexpressed HEK-293 cells was determined using immunofluorescence. Binding affinity and specificity were verified on gastric cancer tissues with immunohistochemistry. 【Results】 Phages significantly were enriched during panning process. After sequencing, nine individual sequences occurred in 30 selected clones. Among the 9 candidate sequences, C9-3 exhibited the highest frequency. Results of ELISA showed that C9-3 had the highest OD value and selectivity. Thus, C9-3 was chosen for peptide probe synthesis. C9-3 probe stained CD44v overexpressed HEK-293 cells, but not empty vector transfected HEK-293 cells. Immunohistochemistry scores of C9-3 were significantly different between gastric cancer and paracancer tissues (t=3.953, P<0.01). A linear positive correlation was observed between C9-3 binding and CD44v9 expression (r=0.823, P<0.01). 【Conclusion】 In this study, peptide ligand of CD44v9 was successfully screened. The peptide can bind to cells and cancer tissues via CD44v9. It has potential for gastric targeting probes.

Research progress of phage display vaccine / 中国生物制品学杂志

@#Bacteriophages are viruses that infect microorganisms such as bacteria,fungi,actinomycetes and spirochetes.Because of the inherent immunogenicity,genetic plasticity,stability,safety and many other advantages,it has unique potential in vaccine research and development. At present,there are countless researches using it to construct vaccine delivery platforms,mainly including three forms,phage display vaccine,phage DNA vaccine and hybrid phage DNA vaccine,of which the phage display vaccine is the most widely studied. Phage display technology is a novel vaccine preparation technology,which is a molecular biology technology using phage as carrier,integrating foreign polypeptide or protein genes into phage genes and displaying them on the surface of phage in the form of fusion protein. This review mainly elaborated the immunological basis of phage display vaccine,the display system and its application in disease prevention,so as to provide a reference for the development and application of phage display vaccine.

Preparation of anti-VirB12 nanoantibodies, a surface protein of type Ⅳ secretory system of Brucella / 国际生物医学工程杂志

Objective:To prepare camel-derived nanoantibodies that can bind to the recombinant protein VirB12 antigen with high affinity and lay the foundation for further research.Methods:Xinjiang Bactrian camels were immunized six times with VirB12 recombinant protein, total RNA was extracted from lymphocytes isolated from peripheral blood, and the VHH gene fragment was amplified by nested PCR to construct a phage VHH display library. ELISA solid-phase affinity and enrichment methods were used for screening. After three rounds of affinity screening, the clones enriched in the second and third rounds were randomly picked out, and the binding of a nanoantibody with soluble expression to VirB12 was analyzed by ELISA. After sequence determination and multiple alignment, repetitive sequences were removed, and finally five non-redundant sequences were obtained, which were named D1, E6, H8, H9, and H10. The five identified nanoantibody genes were transformed into the WK6 strain, and the soluble expression of an intercellular substance was carried out at 16 °C. After purified expression of Ni-NTA, the binding ability and thermal stability of nanoantibodies and the antigen VirB12 protein were detected by Western Blot and ELISA.Results:Five strains of nanoantibodies were expressed in WK6 bacteria in soluble form. SDS-PAGE showed that the purity of five anti-VirB12 nanoantibodies was close to 90%, and they had high antigen-binding activity and obvious antigen-antibody concentration dependence. All four strains of nanoantibodies showed high thermal stability, and after being treated at 90 ℃, they could still retain more than 60% binding activity.Conclusions:In the study, a VHH phage display library with a capacity of 2.8×10 8 cfu/ml was constructed from Xinjiang Bactrian camel lymphocytes immunized with VirB12 recombinant protein. Five anti-VirB12 nanoantibodies with high affinity and thermal stability were obtained through solid-phase screening and enrichment and soluble monoclonal ELISA detection. These results laid the foundation for further development of VirB12 nanoantibodies.

Stratifin em Tumores de Cabeça e Pescoço: Um alvo molecular identificado por Phage Display / Stratifin in head and neck tumors: a molecular target identified by Phage Display

Nos últimos anos, houve um aumento na frequência dos casos de tumores de cabeça e pescoço apesar da diminuição do consumo do tabaco e álcool, e isso tem sido atribuído, em parte, à infecção pelo Papilomavírus Humano HPV. Por apresentar baixa sobrevida em 5 anos e ter alta morbidade, tem se buscado novos alvos moleculares para terapias combinadas. Nesse contexto nosso grupo identificou, através da tecnologia de Phage Display, uma sequência peptídica com interação preferencial por células tumorais com relação à células não transformadas, e ensaios adicionais identificaram seu alvo como sendo a proteína Stratifin. Stratifin tem sido reportado como um oncogene em diversos modelos tumorais, entretanto seu papel em carcinoma de células escamosas de cabeça e pescoço (CCECP) permanece desconhecido e poucos trabalhos na literatura reportam sua atividade em CCECP e/ou outro tumores relacionados ao HPV. Dessa forma, o objetivo desse trabalho foi explorar o potencial valor clínico e o papel biológico da Stratifin em CCECP. Dados do perfil de expressão e de metilação assim como dados clínicos foram extraídos em base de dados do The Cancer Genoma Atlas TCGA. Paralelamente, o perfil de expressão de Stratifin foi verificado através de ensaios de RT/qPCR e Western Blot em um painel de linhagens celulares de CCECP que contempla as principais características moleculares para esses tipos tumorais. A partir da observação de que todas as linhagens expressam Stratifin, utilizou-se a tecnologia de CRISPR/Cas9 para modular sua expressão (nocauteando ou superexpressando o gene) de modo a se observar parâmetros relacionados ao processo tumorigênico. Dessa forma, foi possivel verificar os efeitos da Stratifin em ensaios de proliferação, viabilidade após tratamentos com quimioterápicos, irradiação, crescimento livre de ancoragem e clonogenicidade. Como resultados, observamos que expressão aumentada de Stratifin no tecido tumoral quando comparado ao tecido normal, foi positivamente relacionada com o grau histológico, negatividade para HPV, mutação em TP53 e CDKN2A. Biologicamente, o nocaute de Stratifin foi relacionado com maior sensibilidade à quimioterápicos, menor capacidade de formação de colônias, e reduzida capacidade de crescimento livre de ancoragem. Esses resultados sugerem que Stratifin atue como um oncogene em CCECP, entretanto ensaios adicionais devem ser realizados para corroborar esse achados

Over recent years, there has been an increase of head and neck tumors frequency despite the decrease in tobacco and alcohol consumption, and this has been attributed, in part, to Human Papillomavirus infection. Due to its low 5-year survival and high morbidity, new molecular targets for combined therapies have been sought. In this context, our group identified, through Phage Display technology, a peptide sequence with preferential interaction by tumor cells in relation to non-transformed cells, and further assays identified its target as the Stratifin protein. Stratifin has been reported as an oncogene in several tumor models, however its role in head and neck squamous cell carcinoma (HNSCC) remains unknown and few works in the literature report its activity in HNSCC and/or other HPV-related tumors. Therefore, the aim of this study was to explore the potential clinical value and biological role of Stratifin in HNSCC. Expression profile data as well as clinical data were extracted from The Cancer Genome Atlas - TCGA database. In parallel, the expression profile of Stratifin was verified through RT/qPCR and Western Blot assays in a panel of HNSCC cell lines that address the main molecular characteristics for these tumor types. Since all cell lines express Stratifin, CRISPR/Cas9 technology was used to modulate its expression (gene knocking out or overexpressing) in order to check parameters related to the tumorigenic process. Thus, it was possible to verify the Stratifin effects in proliferation assays, viability after chemotherapy treatments, irradiation, anchorage-free growth and clonogenicity. As a result, we observed an increased expression of Stratifin in tumor tissue when compared to normal tissue, which was positively related to histological grade, HPV negativity, mutation in TP53 and CDKN2A. Biologically, knockout of Stratifin was associated with greater sensitivity to chemotherapy, less colony-forming capacity, and reduced anchorage-free growth capacity. These results suggest that Stratifin acts as an oncogene in HNSCC, however additional assays should be performed to corroborate these findings

Caracterização funcional de proteínas hipotéticas de Leptospira interrogans como adesinas e potenciais antígenos vacinais e para diagnóstico / Functional characterization of hypothetical proteins in Leptospira interrogans as adhesins and potential vaccine and diagnostic antigens

Leptospira spp. constitui um grupo de bactérias espiroquetas gram-negativas englobando espécies saprofíticas, intermediárias e patogênicas, sendo as últimas agentes causadores da leptospirose, doença zoonótica de alcance mundial e endêmica em regiões tropicais em desenvolvimento. O crescente número de espécies identificadas de leptospiras destaca ainda mais sua diversidade genética e mecanismos de virulência únicos, muitos deles com função ainda desconhecida. Esforços para o desenvolvimento de novas vacinas com proteção cruzada e efeito duradouro revelaram possíveis candidatos vacinais que necessitam ser adequadamente validados, sendo assim, há ainda uma urgente necessidade de uma vacina universal contra a leptospirose capaz de controlar e reduzir os surtos cada vez mais frequentes da doença. Adesinas são importantes fatores de virulência em diversos patógenos, constituindo antígenos promissores para o desenvolvimento de vacinas contra a leptospirose, assim como para o desenvolvimento de métodos diagnósticos mais rápidos e precisos. Previamente, foram identificadas três proteínas hipotéticas conservadas em L. interrogans pela técnica de phage display, denominadas arbitrariamente como LepA069, LepA962 e LepA388. A expressão do gene codificador da proteína LepA069 apresentou aumento de aproximadamente 70 % em animais infectados por leptospiras virulentas, representando a primeira evidência funcional desta proteína ainda desconhecida. Porções recombinantes da lipoproteína hipotética LepA962 (LepA962_Nt e LepA962_Phg) foram obtidos, sendo demonstrada a forte interação da proteína LepA962_Phg, contendo a sequência identificada por phage display, com laminina, fibronectina plasmática, colágeno I e fibrinogênio de maneira dose-dependente. Adicionalmente, LepA962_Phg apresentou ligação às células VERO e à sua matriz extracelular secretada, e o soro obtido a partir desta proteína recombinante foi capaz de se ligar à superfície de leptospiras virulentas, indicando que LepA962_Phg pode representar um importante domínio de interação entre as leptospiras e seu hospedeiro. Finalmente, a proteína LepA388 pertencente a uma extensa família de proteínas modificadoras de virulência com função desconhecida (DUF_61), presente apenas nas leptospiras patogênicas mais virulentas, apresentou aumento na expressão de seu gene codificador em animais infectados por leptospiras virulentas de acordo com dados na literatura. Além disso, porções recombinantes da região Nterminal desta proteína apresentaram ligação a laminina, colágenos I e IV, vitronectina e fibronectinas plasmática e celular, principalmente considerando a sequência identificada por phage display. Estes dados reforçam as predições de modelos tridimensionais da proteína LepA388 e de outros membros da família DUF_61, as quais identificam domínios semelhantes a toxinas (como abrina e CARDS) responsáveis pela ligação e internalização celulares nos hospedeiros. Dados recentes sugerem um possível papel citotóxico desempenhado pelas proteínas desta família em leptospiras, as quais podem também ser consideradas potenciais candidatas vacinais e para diagnóstico da leptospirose, devido à sua distribuição restrita em espécies e cepas patogênicas de importância para saúde humana.

Leptospira spp. constitutes a group of gram-negative spirochete bacteria comprising saprophytic, intermediate and pathogenic species, the last being causative agents of leptospirosis, a zoonotic disease of worldwide extent and endemic in developing tropical regions. The growing number of identified leptospiral species further highlights their genetic diversity and unique virulence mechanisms, many of them with unknown function. Efforts to develop new vaccines with cross-protection and long-lasting effect have revealed possible vaccine candidates that need to be properly validated. Therefore, there is still an urgent need for a universal vaccine against leptospirosis capable of controlling and reducing the increasing outbreaks of the disease. Adhesins are important virulence factors in several pathogens, constituting promising antigens for the development of vaccines against leptospirosis, as well as for the development of faster and more accurate diagnostic methods. Previously, three conserved hypothetical proteins in L. interrogans were identified by phage display technique, arbitrarily named as LepA069, LepA962 and LepA388. Expression of the LepA069 encoding gene showed an increase of approximately 70 % in animals infected by virulent leptospires, representing the first functional evidence of this still unknown protein. Recombinant portions of the hypothetical lipoprotein LepA962 (LepA962_Nt and LepA962_Phg) were obtained, demonstrating the strong interaction of the LepA962_Phg protein, containing the sequence identified by phage display, with laminin, plasma fibronectin, collagen I and fibrinogen in a dose-dependent manner. Furthermore, LepA962_Phg showed binding to VERO cells and its secreted extracellular matrix, and the serum obtained from this recombinant protein was able to bind to the surface of virulent leptospires, indicating that LepA962_Phg may represent an important domain of interaction between leptospires and its host. Finally, LepA388 protein belonging to an extensive family of virulence modifying proteins with unknown function (DUF_61), present only in the most virulent pathogenic leptospires, showed an increase in the expression of its encoding gene in animals infected by virulent leptospires according to data in literature. Moreover, recombinant portions of the N-terminal region of this protein showed binding to laminin, collagens I and IV, vitronectin and plasma and cell fibronectins, especially considering the sequence identified by phage display. These data support the predictions of three-dimensional models of the LepA388 protein and other members of the DUF_61 family, which identify toxin-like domains (such as abrin and CARDS) responsible for cellular binding and internalization in hosts. Recent data suggest a possible cytotoxic role played by proteins of this family in leptospires, which can also be considered potential vaccine candidates and antigens for diagnosis, due to their restricted distribution in pathogenic species and strains of importance to human health

Development of novel-nanobody-based lateral-flow immunochromatographic strip test for rapid detection of recombinant human interferon α2b / 药物分析学报

Recombinant human interferon α2b(rhIFNα2b)is widely used as an antiviral therapy agent for the treatment of hepatitis B and hepatitis C.The current identification test for rhIFNα2b is complex.In this study,an anti-rhIFNα2b nanobody was discovered and used for the development of a rapid lateral flow strip for the identification of rhIFNα2b.RhIFNα2b was used to immunize an alpaca,which established a phage nanobody library.After five steps of enrichment,the nanobody I22,which specifically bound rhIFNα2b,was isolated and inserted into the prokaryotic expression vector pET28a.After subsequent purification,the physicochemical properties of the nanobody were determined.A semiquantitative detection and rapid identification assay of rhIFNα2b was developed using this novel nanobody.To develop a rapid test,the nanobody I22 was coupled with a colloidal gold to produce lateral-flow test strips.The developed rhIFNα2b detection assay had a limit of detection of 1 μg/mL.The isolation of I22 and successful construction of a lateral-flow immunochromatographic test strip demonstrated the feasibility of performing ligand-binding assays on a lateral-flow test strip using recombinant protein products.The principle of this novel assay is generally applicable for the rapid testing of other com-mercial products,with a great potential for routine use in detecting counterfeit recombinant protein products.

Preliminary Study on Screening and Identification of Lewis a Antigen Mimic Epitope in Alpaca Phage Display Nanobody Library / 中国实验血液学杂志

OBJECTIVE@#To establish a new method for synthesizing Lewis blood group antigens, that is, the mimotopes of Lewis blood group antigens were screened by using an alpaca phage display nanobody library.@*METHODS@#We selected mimotopes of the Lewis a (lea) antigen by affinity panning of an alpaca phage display nanobody library using a monoclonal anti-lea antibody. Enzyme-linked immunosorbent assay (ELISA) was used to test the affinity of the positive clones for the monoclonal anti-lea antibody, and the high-affinity positive clones were selected for sequencing and synthesis. Finally, the sensitivity, specificity and reactivity of the synthesized lea mimotope in clinical samples were verified by ELISA.@*RESULTS@#A total of 96 phage clones were randomly selected, and 24 were positive. Fourteen positive clones with the highest affinity were selected for sequencing. The result showed that there were 5 different sequences, among which 3 sequences with the highest frequency, largest difference and highest affinity were selected for expression and synthesis. The sensitivity and specificity of lea mimic antigen by ELISA showed that, the minimum detection limit of gel microcolumn assay (GMA) and ELISA method were 25 times different, and the lea mimic antigen had no cross reacted with the other five unrelated monoclonal antibodies(P<0.001). Finally, 30 clinical plasma samples were analyzed. The mean absorbance of the 15 positive plasma samples was significantly higher than that of the 15 negative plasma samples (P=0.02). However, the positive signal values of the clinical samples were much lower than those of the monoclonal antibodies.@*CONCLUSION@#A new method of screening lea mimic antigen by using alpaca phage nanoantibody library has been established, which is expected to realize the screening of lea mimotopes, thus realizing the application of high-sensitivity detection methods such as ELISA and chemiluminescence in blood group antibody identification.

Phage display technology and its application in antivirals discovery / 药学学报

The COVID-19 outbreak has drawn attention to viral infectious diseases once again, and the development of antiviral drugs for both known and potentially emerging viruses is of great significance. In recent years, peptides and protein drugs are becoming a hot spot in the field of antiviral drug research and development. Phage display technology, as a powerful tool for screening peptides and protein drugs, has been increasingly concerned in the academic and industrial fields. The present review introduced the basic principle of phage display technology, summarized phage display libraries often used in antiviral drug discovery and their applications, discussed the challenges and future direction of antiviral drug research and development based on phage display technology.

Selection and characterization of peptides mimetic to Campylobacter fetus subsp. venerealis using phage display / Seleção e caracterização de peptídeos miméticos a Campylobacter fetus subsp. venerealis usando phage display

ABSTRACT: Bovine genital campylobacteriosis (BGC) is a venereal and subclinical disease that affects the fertility of cattle herds, and it is caused by Campylobacter fetus subsp. venerealis . This study selected peptides mimetic to the BGC-causing agent from a phage library. Phage display is a technique that applies bacteriophage libraries that reveal peptides fused to the viral capsid in biological selections against target proteins. Biopannings were performed for biological selection in the phage library using rabbit hyperimmune serum and C. fetus subsp. venerealis protein extract. Five selected heptapeptides were considered mimetic to Cfv-NCTC 10354 based on the results of bioinformatics analysis and assays with hyperimmune serum and cervicovaginal mucus obtained from heifers. ALASLPL and LSYLFPP were the most reactive peptides and considered promising as possible mimetic immunogens for C. fetus subsp. venerealis.

RESUMO: Campilobacteriose Genital Bovina (CGB) é uma doença venérea e subclínica que causa problemas reprodutivos em rebanhos, causada por Campylobacter fetus subsp. venerealis. Este trabalho teve como objetivo selecionar peptídeos miméticos ao agente da CGB de uma biblioteca de fagos. Phage display é uma técnica que aplica bibliotecas de bacteriófagos que expõem peptídeos fusionados ao capsídeo viral em seleções biológicas contra proteínas alvo. Biopannings foram realizados para seleção biológica na biblioteca de fagos por meio de soro hiperimune de coelho e extrato proteico de C. fetus subsp. venerealis. Cinco heptapeptídeos selecionados foram considerados miméticos para Cfv-NCTC 10354 a partir de análises de bioinformática e ensaios com soro hiperimune e muco cérvico-vaginal de novilhas. ALASLPL e LSYLFPP foram os peptídeos mais reativos e considerados promissores como possíveis imunógenos miméticos para C. fetus subsp. venerealis.

Research progress of cyclic peptides derived from phage display technology / 药学学报

Cyclic peptide drugs have gradually become an emerging research direction due to their some favorable properties such as high-efficiency binding affinity, high selectivity, lower toxicity, and stable metabolism. In recent years, the number of cyclic peptide drugs under clinical research has continued to increase. Unlike the previous cyclic peptide drugs, which were mostly derived from natural products and their derivatives, these cyclic peptide drugs are designed by genetically encoded display technologies which are based on rational design and in vitro evolution (such as BT1718, PTG-300, POL6326, etc). Among them, phage display technology has some advantages such as mature research system, low cost, and simpler operation that make it well recognized and praised by the majority of researchers in this field. Here, we reviewed the recent progress of applying phage display technology to explore diverse cyclic peptide libraries, which, we believe, will contribute more valuable candidate cyclic peptide drugs in clinical research.

Chicken antibodies against venom proteins of Trimeresurus stejnegeri in Taiwan

The venom of bamboo vipers (Trimeresurus stejnegeri - TS), commonly found in Taiwan, contains deadly hemotoxins that cause severe envenomation. Equine-derived antivenom is a specific treatment against snakebites, but its production costs are high and there are some inevitable side effects. The aim of the present work is to help in the development of an affordable and more endurable therapeutic strategy for snakebites. Methods: T. stejnegeri venom proteins were inactivated by glutaraldehyde in order to immunize hens for polyclonal immunoglobulin (IgY) antibodies production. After IgY binding assays, two antibody libraries were constructed expressing single-chain variable fragment (scFv) antibodies joined by the short or long linker for use in phage display antibody technology. Four rounds of biopanning were carried out. The selected scFv antibodies were then further tested for their binding activities and neutralization assays to TS proteins. Results: Purified IgY from egg yolk showed the specific binding ability to TS proteins. The dimensions of these two libraries contain 2.4 × 107 and 6.8 × 107 antibody clones, respectively. An increase in the titers of eluted phage indicated anti-TS clones remarkably enriched after 2nd panning. The analysis based on the nucleotide sequences of selected scFv clones indicated that seven groups of short linkers and four groups of long linkers were identified. The recombinant scFvs showed significant reactivity to TS venom proteins and a cross-reaction to Trimeresurus mucrosquamatus venom proteins. In in vivo studies, the data demonstrated that anti-TS IgY provided 100% protective effects while combined scFvs augmented partial survival time of mice injected with a lethal amount of TS proteins. Conclusion: Chickens were excellent hosts for the production of neutralization antibodies at low cost. Phage display technology is available for generation of monoclonal antibodies against snake venom proteins. These antibodies could be applied in the development of diagnostic kits or as an alternative for snakebite envenomation treatment in the near future.(AU)

Recombinant antibodies against Iranian cobra venom as a new emerging therapy by phage display technology

The production of antivenom from immunized animals is an established treatment for snakebites; however, antibody phage display technology may have the capacity to delivery results more quickly and with a better match to local need. Naja oxiana, the Iranian cobra, is a medically important species, responsible for a significant number of deaths annually. This study was designed as proof of principle to determine whether recombinant antibodies with the capacity to neutralize cobra venom could be isolated by phage display. Methods: Toxic fractions from cobra venom were prepared by chromatography and used as targets in phage display to isolate recombinant antibodies from a human scFv library. Candidate antibodies were expressed in E. coli HB2151 and purified by IMAC chromatography. The selected clones were analyzed in in vivo and in vitro experiments. Results: Venom toxicity was contained in two fractions. Around a hundred phage clones were isolated against each fraction, those showing the best promise were G12F3 and G1F4. While all chosen clones showed low but detectable neutralizing effect against Naja oxiana venom, clone G12F3 could inhibit PLA2 activity. Conclusion: Therefore, phage display is believed to have a good potential as an approach to the development of snake antivenom.(AU)

Screening specific binding peptides of Mycobacterium tuberculosis PPE17 protein by Phage display technique / 公共卫生与预防医学

Objective The specific binding peptide of Mycobacterium tuberculosis PPE17 protein was screened by phage display technique. Methods PPE17 gene was amplified from Mycobacterium tuberculosis genome, cloned into pET28a, expressed in E. coli BL21, purified by Ni2+ column, and identified by SDS-PAGE and Western blot. The purified PPE17 protein was coated into an ELISA plate and screened by phage 7 peptide library. After three rounds of panning, phage plaques were randomly selected for sequencing. DNAMAN was used to analyze and compare the amino acid sequences of the polypeptide encoded by the positive clones. Results PPE17 gene was successfully constructed and expressed, and soluble protein with molecular weight of about 37kD was obtained. From the third round of eluents, 20 plaque were randomly selected. The sequencing results could be translated into 8 polypeptide molecules, among which the polypeptide sequence repeated for 6 times was LKWGHVY. Conclusion The specific binding peptide of PPE17 protein is screened by phage display technology, which is expected to be a small molecular diagnostic reagent for the identification of this antigen.

The screening and identification of internalized nanobody against EpCAM / 药学学报

Epithelial cell adhesion molecule (EpCAM) is a popular target for cancer therapy. In this research, 3 nanobodies with high specificity and endocytosis activity against EpCAM were developed, which provides a basis for the study of immunotoxin based on EpCAM. In our preliminary experiments, we have immunized a camel with EpCAM-Fc antigen and constructed a high-quality phage display library. Seventeen nanobodies with different complementarity determining region (CDR) 3 sequences have been screened after 3 rounds of biopanning by phage display technology. The animal procedures were approved by the Institutional Animal Care and Use Committee (IACUC) of Fudan University School of Pharmacy. After purification, 7 nanobodies showed high cell binding activity by fluorescent activated cell sorting (FACS) identification. Furthermore, 3 nanobodies presented high endocytosis activity based on FACS and laser confocal microscopy, which also showed high affinity to EpCAM measured by ForteBio. According to this study, we aimed to provide a novel alternative approach to the EpCAM-targeted therapy and to provide guidance for the study of nanobody based immunotoxins for other targets.

Advances in effectively screening anti-tumor peptides / 药学学报

Malignant tumor is a disease that severely threaten human health. Common chemotherapeutical drugs currently used in clinical practice have some problems in severe side effects and chemoresistance. In contrast, natural venom peptides and artificially designed targeting peptides have excellent biological activities and potential druggability due to their small molecular weights and high affinity to tumor tissues. Thus, the methods for the discovery of anti-tumor peptides have attracted much attention. In this paper, we summarized the types of anti-tumor peptides from recent literatures. Then, we systematically reviewed screening theories, methods and applications based on traditional chromatographic separation, peptidomics, phage display, phenotypic screening, and artificial intelligence. These strategies and technologies will provide a methodological reference for accelerating anti-tumor peptides research.

Screening and identification of human anti-C3d single chain antibodies / 国际药学研究杂志

Objective: To screen human single chain antibodies against human C3d from phage-displayed single-chain variable fragment(scFv)library, and analyze their binding activities. Methods: The phage display library was exposed to 3-round selections in immunotubes coated with recombinant C3d at a decreasing concentration range and progressively stringent washing conditions. The positive clones were identified by ELISA, followed with sequencing to determine the specific genes which were then cloned intoex-pression vectors. The single chain antibodies were expressed in the FreeStyleTM 293-F system and harvested by affinity purification. The binding activities with recombinant C3d were determined by using Bio-Layer Interferometry technology. Results: These experiments resulted in three novel single chain antibodies(that is, A1, A3 and B6)against C3d with high affinity ranging from 22.7 to 171 pmol/ L. Conclusion: The high affinity human single chain antibodies against human C3d were obtained.

Screening and Identification of the Peptides Specifically Binding to Human Non-small Cell Lung Cancer NCI-H1299 Cells / 中国肺癌杂志

BACKGROUND@#Non-small cell lung cancer (NSCLC) is the most common histological type of lung cancer, and one of the malignant tumor with the highest mortality. As the main part of the optical molecular imaging probe, peptide can realize the early screening and diagnosis of tumor and improve the survival rate of patients. The aim of this study was to screen the small-molecule peptide that highly binds to NSCLC NCI-H1299 cells using in vivo phage display technology and to identify their binding specificity by in vitro experiment.@*METHODS@#To prepare a tumor-bearing nude mouse model of NCI-H1299 cells, after 3 rounds of in vivo screening with Ph.D.-C7CTM Peptide Library, phage clones were randomly picked, using immunohistochemistry and enzyme-linked immunosorbent assay (ELISA) to identify the affinity of phage clones to NCI-H1299 cells. The positive monoclonal phages DNA was extracted and sequenced to obtain the amino acid sequence of the peptides. The peptides with the highest repetition rate was chemically synthesized and labeled with fluorescein (FITC) to prepare optical molecular probe. We preliminary identified the specificity of the probe binding to lung cancer cells by in vitro experiment.@*RESULTS@#After three rounds of in vivo screening, the phages enrichment rate was 341.3 times compared with the first round. Immunohistochemical staining showed that with the increase of screening times, the phages binding to tumor tissues continued to increase, and the binding amount was significantly higher than normal tissues; ELISA results showed that 20 clones among the 30 randomly selected phage clones were positive. After sequencing, the peptide with the highest repetition rate was synthesized and named NSP1; Methyl thiazolyl tetrazolium assay (MTT) and would healing assay showed that NSP1 will not affect cell proliferation and migration. Flow cytometry and immunofluorescence showed specific binding of NSP1 to NCI-H1299 cells.@*CONCLUSIONS@#We successfully obtained the peptide NSP1 that specifically binds to lung cancer NCI-H1299 cells by in vivo phage display, which provide a theoretical basis for NSCLC early diagnosis and targeted therapy.

Quality control of serum antibodies through the combination of phage display and next generation sequencing / 上海交通大学学报（医学版）

Objective • To establish a quality control system for serum antibodies and provide a quantitative standard for the quality control of serum autoantibody-based biomarker study. Methods • Sera from 50 healthy people were taken to prepare the samples and aliquoted. The aliquoted sera were stored at-80 ℃, -20 ℃, 4 ℃, 37 ℃, and 95 ℃ for a period of time. Samples were collected at different time points. The samples were incubated with Ph.D.-12, a phage display random peptide library. The phage-IgG complex was enriched through immunoprecipitation with protein G-coated magnetic beads. By sequencing the coding sequences of the displayed peptides, the sequence and frequency of the serum antibody-enriched peptides were determined. Using the frequencies of each enriched peptide, Shannon entropies were calculated for each sample. Shannon entropy was applied as an indicator to evaluate the quality of the serum autoantibodies. Results • With the increase of the treating temperature, the Shannon entropies of the sera gradually decreased, while there was no significant difference between the Shannon entropies of-20 ℃ and-80 ℃. The Shannon entropy reached the lowest value after being treated at 95 ℃ for 10 min. At the same temperature, the Shannon entropies of the sera were inversely proportional to the length of the treating periods. Conclusion • It is practically applicable to decipher the profile of the serum antibody binding peptides, through the combination of a phage display random peptide library and next-generation sequencing. Shannon entropy can be calculated using the frequencies of each enriched peptide, and applied as an indicator to judge the overall quality of the serum antibodies.