scFv antibodies against infectious bursal disease virus isolated from a combinatorial antibody library by flow cytometry

Phage nanofibers in nanomedicine: Biopanning for early diagnosis, targeted therapy, and proteomics analysis

Display of a peptide or protein of interest on the filamentous phage (also known as bacteriophage), a biological nanofiber, has opened a new route for disease diagnosis and therapy as well as proteomics. Earlier phage display was widely used in protein-protein or antigen-antibody studies. In recent years, its application in nanomedicine is becoming increasingly popular and encouraging. We aim to review the current status in this research direction. For better understanding, we start with a brief introduction of basic biology and structure of the filamentous phage. We present the principle of phage display and library construction method on the basis of the filamentous phage. We summarize the use of the phage displayed peptide library for selecting peptides with high affinity against cells or tissues. We then review the recent applications of the selected cell or tissue targeting peptides in developing new targeting probes and therapeutics to advance the early diagnosis and targeted therapy of different diseases in nanomedicine. We also discuss the integration of antibody phage display and modern proteomics in discovering new biomarkers or target proteins for disease diagnosis and therapy. Finally, we propose an outlook for further advancing the potential impact of phage display on future nanomedicine. This article is categorized under: Biology-Inspired Nanomaterials > Protein and Virus-Based Structures.

Bivalent DNA vaccine induces significant immune responses against infectious hematopoietic necrosis virus and infectious pancreatic necrosis virus in rainbow trout

Infectious hematopoietic necrosis virus (IHNV) and infectious pancreatic necrosis virus (IPNV) are important pathogens of salmon and trout. An active bivalent DNA vaccine was constructed with the glycoprotein gene of Chinese IHNV isolate Sn1203 and VP2-VP3 gene of Chinese IPNV isolate ChRtm213. Rainbow trout (5 g) were vaccinated by intramuscular injection with 1.0 µg of the bivalent DNA vaccine and then challenged with an intraperitoneal injection of IHNV, IPNV, or both, at 30 and 60 days post-vaccination (d.p.v.). High protection rates against IHNV were observed, with 6% and 10% cumulative mortality, respectively, compared with 90-94% in the mock-vaccinated groups. IPNV loads (531-fold and 135-fold, respectively) were significantly reduced in the anterior kidneys of the vaccinated trout. Significant protection against co-infection with IHNV and IPNV was observed, with cumulative mortality rates of 6.67% and 3.33%, respectively, compared with 50.0% and 43.3%, respectively, in the mock-vaccinated groups. No detectable infective IHNV or IPNV was recovered from vaccinated trout co-infected with IHNV and IPNV. The bivalent DNA vaccine increased the expression of Mx-1 and IFN-γ at 4, 7, and 15 d.p.v, and IgM at 21 d.p.v., and induced high titres (≥160) of IHNV and IPNV neutralizing antibodies at 30 and 60 d.p.v.

Insights into the chicken IgY with emphasis on the generation and applications of chicken recombinant monoclonal antibodies

The advantages of chicken (Gallus gallus domesticus) antibodies as immunodiagnostic and immunotherapeutic biomolecules has only been recently recognized. Even so, chicken antibodies remain less-well characterized than their mammalian counterparts. This review aims at providing a current overview of the structure, function, development and generation of chicken antibodies. Additionally, brief but comprehensive insights into current knowledge pertaining to the immunogenetic framework and diversity-generation of the chicken immunoglobulin repertoire which have contributed to the establishment of recombinant chicken mAb-generating methods are discussed. Focus is provided on the current methods used to generate antibodies from chickens with added emphasis on the generation of recombinant chicken mAbs and its derivative formats. The advantages and limitations of established protocols for the generation of chicken mAbs are highlighted. The various applications of recombinant chicken mAbs and its derivative formats in immunodiagnostics and immunotherapy are further detailed.

A recombinant avian antibody against VP2 of infectious bursal disease virus protects chicken from viral infection

A stable cell-line was established that expressed the recombinant avian antibody (rAb) against the infectious bursal disease virus (IBDV). rAb exhibited neutralization activity to IBDV-B87 strain in DF1 cells. The minimum rAb concentration required for inhibition of the cytopathic effect (CPE) was 1.563μg/mL. To test the efficacy of rAb, a 168-h cohabitation challenge experiment was performed to transmit the disease from the chickens challenged with vvIBDV (HLJ0504 strain) to three test groups of chickens, i.e. (1) chickens treated with rAb, (2) chickens treated with yolk antibody, and (3) non-treatment chickens. The survival rates of chickens treated with rAb, yolk antibody and without treatment were 73%, 67% and 20%, respectively. Another batch of chickens was challenged with IBDV (BC6/85 strain) and then injected with rAb (1.0mg/kg) 6, 24 and 36h post-challenge. Non-treatment chickens had 100% morbidity, whereas those administered with rAb exhibited only 20% morbidity. Morbidity was evaluated using clinical indicators and bursal histopathological section. This study provides a new approach to treating IBDV and the rAb represents a promising candidate for this IBDV therapy.

Recombinant scFv antibodies against infectious pancreatic necrosis virus isolated by flow cytometry

Infectious pancreatic necrosis is a significant disease of farmed salmonids in China. In this study, a single chain variable fragment (scFv) antibody library derived from rainbow trout (Oncorhynchus mykiss) and viral protein VP2 of a Chinese infectious pancreatic necrosis virus (IPNV) isolate ChRtm213 were co-expressed by a bacterial display technology. The library was subjected to three rounds of screening by flow cytometry (FCM) to select IPNV specific antibodies. Six antibody clones with different mean fluorescence intensities (MFI) were obtained by picking colonies at random. The antibody clones were expressed and purified. The purified IPNV-specific scFv antibodies were used successfully in Western blotting, enzyme linked immunosorbent assay (ELISA) and an immunofluorescence antibody test (IFAT). This method provides a high throughput means to screen an antibody library by flow cytometry, and isolate a panel of antibody that can be used as potential reagents for the detection and study of IPNV that are prevalent in China.

Screening scFv antibodies against infectious bursal disease virus by co-expression of antigen and antibody in the bacteria display system

We have previously reported an antigen and antibody co-expression (AAC) technology to demonstrate the interaction between a known antigen and antibody. To validate the co-expression system for screening antibody libraries, a single chain fragment variable(scFv)antibody library was constructed from chickens immunized with the VP2 protein of infectious bursal disease virus (IBDV). The genes of both VP2 and scFv antibodies were inserted into the pBFD-Ab-Ag vector. The co-expression library was subjected to three rounds of screening by flow cytometry (FCM) using a polyclonal antibody against VP2 through a bacteria display system. We achieved enrichment of scFv specific for IBDV. 110 individual clones were initially selected and sequenced. Twenty clones were selected based on fluorescence intensity by FCM. The scFv antibodies were expressed by pET-27b in E.coli and purified. The specificity and affinity of the selected scFv antibodies were confirmed by western blotting assay and ELISA analysis. What's more, the neutralizing capacity was measured with IBDV-B87(100 TCID₅₀) in vitro. Four scFvs (clone 8(1), Y8, L10 and L7) showed significant neutralizing capacity. Two of the four scFvs (clone 8(1) and Y8) demonstrated a higher neutralizing activity to IBDV-B87 and the titers were 16,384 and 8,192, respectively. The two scFvs had higher neutralizing capacity than those obtained in previous studies. We demonstrated that the AAC technology could be applied to screen antibody libraries without baiting antigen to make antibody screening process easier and obtain scFvs with higher neutralizing capacity.

Selection of affinity-improved neutralizing human scFv against HBV PreS1 from CDR3 VH/VL mutant library

A CDR3 mutant library was constructed from a previously isolated anti-HBV neutralizing Homo sapiens scFv-31 template by random mutant primers PCR. Then the library was displayed on the inner membrane surface in Escherichia coli periplasmic space. Seven scFv clones were isolated from the mutant library through three rounds of screening by flow cytometry. Competition ELISA assay indicates that isolated scFv fragments show more efficient binding ability to HBV PreS1 compared with parental scFv-31. HBV neutralization assay indicated that two clones (scFv-3 and 59) show higher neutralizing activity by blocking the HBV infection to Chang liver cells. Our method provides a new strategy for rapid screening of mutant antibody library for affinity-enhanced scFv clones and the neutralizing scFvs obtained from this study provide a potential alternative of Hepatitis B immune globulin.

Infectious bursal disease virus in poultry: current status and future prospects

Infectious bursal disease virus (IBDV) affects immature B lymphocytes of the bursa of Fabricius and may cause significant immunosuppression. It continues to be a leading cause of economic losses in the poultry industry. IBDV, having a segmented double-stranded RNA genome, is prone to genetic variation. Therefore, IBDV isolates with different genotypic and phenotypic diversity exist. Understanding these features of the virus and the mechanisms of protective immunity elicited thereof is necessary for developing vaccines with improved efficacy. In this review, we highlighted the pattern of virus evolution and new developments in prophylactic strategies, mainly the development of new generation vaccines, which will continue to be of interest for research as well as field application in the future.

A neutralizing scFv antibody against infectious bursal disease virus screened by flow cytometry

Infectious bursal disease (IBD) is considered a vital viral disease that threatens the poultry industry worldwide. In this study, a recombinant single chain variable fragment (scFv) antibody library derived from chickens immunized with VP2 protein of infectious bursal disease virus (IBDV) was constructed. The library was subjected to three rounds of screening by flow cytometry (FCM) against VP2/IBDV through a bacteria display technology, resulting in the enrichment of scFvs. Three scFv clones with different fluorescence intensity were obtained by colony pick up at random. The obtained scFv antibodies were expressed and purified. Relative affinity assay showed the three clones had different sensitivity to VP2, in accordance with fluorescence activity cell sorting analysis (FACS). The potential use of the isolated IBDV-specific scFv antibodies was demonstrated by the successful application of these antibodies in Western blotting and ELISA assay. What's more, in vitro neutralization measurement showed that one of the three isolated antibodies possessed the neutralization function against IBDV. This study provides new strategies for screening of antibody library, and scFv antibodies isolated in this study may be utilized as lead candidates for further development of diagnostic or therapeutic antibodies for detection and treatment of IBDV infection.