Intracellularly expressed single-domain antibody against p15 matrix protein prevents the production of porcine retroviruses

Nanobodies in the fight against infectious diseases: repurposing nature's tiny weapons

Nanobodies are the smallest known antigen-binding molecules to date. Their small size, good tissue penetration, high stability and solubility, ease of expression, refolding ability, and negligible immunogenicity in the human body have granted them excellence over conventional antibodies. Those exceptional attributes of nanobodies make them promising candidates for various applications in biotechnology, medicine, protein engineering, structural biology, food, and agriculture. This review presents an overview of their structure, development methods, advantages, possible challenges, and applications with special emphasis on infectious diseases-related ones. A showcase of how nanobodies can be harnessed for applications including neutralization of viruses and combating antibiotic-resistant bacteria is detailed. Overall, the impact of nanobodies in vaccine design, rapid diagnostics, and targeted therapies, besides exploring their role in deciphering microbial structures and virulence mechanisms are highlighted. Indeed, nanobodies are reshaping the future of infectious disease prevention and treatment.

Nanobodies: The "Magic Bullets" in therapeutics, drug delivery and diagnostics

Antibodies represent a well-established class of clinical diagnostics for medical applications as well as essential research and biotechnological tools. Although both polyclonal and monoclonal antibodies are indispensable reagents in basic research and diagnostics but both of them have their limitations. Hence, there is urgent need to develop strategies aimed at production of alternative scaffolds and recombinant antibodies of smaller dimensions that could be easily produced, selected and manipulated. Unlike conventional antibodies, members of Camelidae and sharks produce antibodies composed only of heavy chains with small size, high solubility, thermal stability, refolding capacity and good tissue penetration in vivo. The discovery of these naturally occurring antibodies having only heavy-chain in Camelidae family and their further development into small recombinant nanobodies represents an attractive alternative in drug delivery, diagnostics and imaging. Nanobody derivatives are soluble, stable, versatile, have unique refolding capacities, reduced aggregation tendencies and high-target binding capabilities. They can be genetically customized to target enzymes, transmembrane proteins or molecular interactions. Their ability to recognize recessed antigenic sites has been attributed to their smaller size and the ability of the extended CDR3 loop to quickly penetrate into such epitopes. With the advent of molecular engineering and phage display technology, they can be of potential use in molecular imaging, drug delivery and therapeutics for several major diseases. In this review we present the recent advances in nanobodies for modulating immune functions, for targeting cancers, viruses, toxins and microbes as well as their utility as diagnostic and biosensor tools.

Applying Antibodies Inside Cells: Principles and Recent Advances in Neurobiology, Virology and Oncology

To interfere with cell function, many scientists rely on methods that target DNA or RNA due to the ease with which they can be applied. Proteins are usually the final executors of function but are targeted only indirectly by these methods. Recent advances in targeted degradation of proteins based on proteolysis-targeting chimaeras (PROTACs), ubiquibodies, deGradFP (degrade Green Fluorescent Protein) and other approaches have demonstrated the potential of interfering directly at the protein level for research and therapy. Proteins can be targeted directly and very specifically by antibodies, but using antibodies inside cells has so far been considered to be challenging. However, it is possible to deliver antibodies or other proteins into the cytosol using standard laboratory equipment. Physical methods such as electroporation have been demonstrated to be efficient and validated thoroughly over time. The expression of intracellular antibodies (intrabodies) inside cells is another way to interfere with intracellular targets at the protein level. Methodological strategies to target the inside of cells with antibodies, including delivered antibodies and expressed antibodies, as well as applications in the research areas of neurobiology, viral infections and oncology, are reviewed here. Antibodies have already been used to interfere with a wide range of intracellular targets. Disease-related targets included proteins associated with neurodegenerative diseases such as Parkinson's disease (α-synuclein), Alzheimer's disease (amyloid-β) or Huntington's disease (mutant huntingtin [mHtt]). The applications of intrabodies in the context of viral infections include targeting proteins associated with HIV (e.g. HIV1-TAT, Rev, Vif, gp41, gp120, gp160) and different oncoviruses such as human papillomavirus (HPV), hepatitis B virus (HBV), hepatitis C virus (HCV) and Epstein-Barr virus, and they have been used to interfere with various targets related to different processes in cancer, including oncogenic pathways, proliferation, cell cycle, apoptosis, metastasis, angiogenesis or neo-antigens (e.g. p53, human epidermal growth factor receptor-2 [HER2], signal transducer and activator of transcription 3 [STAT3], RAS-related RHO-GTPase B (RHOB), cortactin, vascular endothelial growth factor receptor 2 [VEGFR2], Ras, Bcr-Abl). Interfering at the protein level allows questions to be addressed that may remain unanswered using alternative methods. This review addresses why direct targeting of proteins allows unique insights, what is currently feasible in vitro, and how this relates to potential therapeutic applications.

Nanobodies in Human Infections: Prevention, Detection, and Treatment

Despite the existence of vaccination, antibiotic therapy, and antibody therapies, infectious diseases still remain as one of the biggest challenges to human health all over the world. Among the different methods for treatment and prevention of infectious diseases, antibodies are well known but poorly developed. There is a new subclass of antibodies calledheavy-chain antibodies that belong to the IgG isotype. However, they are low in molecular weight and lost the first constant domain (CH1). Their single-domain antigen-binding fragments, identified as nanobodies, have unique characteristics, which make them superior in comparison with the conventional antibodies. Low molecular weight and small size, high stability and solubility, ease of expression, good tissue penetration, and low-cost production make nanobodies an appropriate alternative to use against infectious disease. In this research, we review the properties of nanobodies and their potential applications in controlling human infections and inflammations.

Porcine Endogenous Retrovirus (PERV) - Molecular Structure and Replication Strategy in the Context of Retroviral Infection Risk of Human Cells

The xenotransplantation of porcine tissues may help overcome the shortage of human organs for transplantation. However, there are some concerns about recipient safety because the risk of porcine endogenous retrovirus (PERV) transmission to human cells remains unknown. Although, to date, no PERV infections have been noted in vivo, the possibility of such infections has been confirmed in vitro. Better understanding of the structure and replication cycle of PERVs is a prerequisite for determining the risk of infection and planning PERV-detection strategies. This review presents the current state of knowledge about the structure and replication cycle of PERVs in the context of retroviral infection risk.

Single domain antibodies for the knockdown of cytosolic and nuclear proteins

Single domain antibodies (sdAbs) from camels or sharks comprise only the variable heavy chain domain. Human sdAbs comprise the variable domain of the heavy chain (VH) or light chain (VL) and can be selected from human antibodies. SdAbs are stable, nonaggregating molecules in vitro and in vivo compared to complete antibodies and scFv fragments. They are excellent novel inhibitors of cytosolic/nuclear proteins because they are correctly folded inside the cytosol in contrast to scFv fragments. SdAbs are unique because of their excellent specificity and possibility to target posttranslational modifications such as phosphorylation sites, conformers or interaction regions of proteins that cannot be targeted with genetic knockout techniques and are impossible to knockdown with RNAi. The number of inhibiting cytosolic/nuclear sdAbs is increasing and usage of synthetic single pot single domain antibody libraries will boost the generation of these fascinating molecules without the need of immunization. The most frequently selected antigenic epitopes belong to viral and oncogenic proteins, followed by toxins, proteins of the nervous system as well as plant- and drosophila proteins. It is now possible to select functional sdAbs against virtually every cytosolic/nuclear protein and desired epitope. The development of new endosomal escape protein domains and cell-penetrating peptides for efficient transfection broaden the application of inhibiting sdAbs. Last but not least, the generation of relatively new cell-specific nanoparticles such as polymersomes and polyplexes carrying cytosolic/nuclear sdAb-DNA or -protein will pave the way to apply cytosolic/nuclear sdAbs for inhibition of viral infection and cancer in the clinic.

Mammalian TIMELESS is involved in period determination and DNA damage-dependent phase advancing of the circadian clock

The transcription/translation feedback loop-based molecular oscillator underlying the generation of circadian gene expression is preserved in almost all organisms. Interestingly, the animal circadian clock proteins CRYPTOCHROME (CRY), PERIOD (PER) and TIMELESS (TIM) are strongly conserved at the amino acid level through evolution. Within this evolutionary frame, TIM represents a fascinating puzzle. While Drosophila contains two paralogs, dTIM and dTIM2, acting in clock/photoreception and chromosome integrity/photoreception respectively, mammals contain only one TIM homolog. Whereas TIM has been shown to regulate replication termination and cell cycle progression, its functional link to the circadian clock is under debate. Here we show that RNAi-mediated knockdown of TIM in NIH3T3 and U2OS cells shortens the period by 1 hour and diminishes DNA damage-dependent phase advancing. Furthermore, we reveal that the N-terminus of TIM is sufficient for interaction with CRY1 and CHK1 as well for homodimerization, and the C-terminus is necessary for nuclear localization. Interestingly, the long TIM isoform (l-TIM), but not the short (s-TIM), interacts with CRY1 and both proteins can reciprocally regulate their nuclear translocation in transiently transfected COS7 cells. Finally, we demonstrate that co-expression of PER2 abolishes the formation of the TIM/CRY1 complex through affinity binding competition to the C-terminal tail of CRY1. Notably, the presence of the latter protein region evolutionarily and structurally distinguishes mammalian from insect CRYs. We propose that the dynamic interaction between these three proteins could represent a post-translational aspect of the mammalian circadian clock that is important for its pace and adaption to external stimuli, such as DNA damage and/or light.

Current development of bioreactors for extracorporeal bioartificial liver (Review)

The research and development of extracorporeal bioartificial liver is gaining pace in recent years with the introduction of a myriad of optimally designed bioreactors with the ability to maintain long-term viability and liver-specific functions of hepatocytes. The design considerations for bioartificial liver are not trivial; it needs to consider factors such as the types of cell to be cultured in the bioreactor, the bioreactor configuration, the magnitude of fluid-induced shear stress, nutrients' supply, and wastes' removal, and other relevant issues before the bioreactor is ready for testing. This review discusses the exciting development of bioartificial liver devices, particularly the various types of cell used in current reactor designs, the state-of-the-art culturing and cryopreservation techniques, and the comparison among many today's bioreactor configurations. This review will also discuss in depth the importance of maintaining optimal mass transfer of nutrients and oxygen partial pressure in the bioreactor system. Finally, this review will discuss the commercially available bioreactors that are currently undergoing preclinical and clinical trials.

Nanobody; an old concept and new vehicle for immunotargeting

The use of antibodies in cancer therapy has come a long way since the day Paul Ehrlich described the concept and Kohler and Milstein devised the hybridoma technology to bring this theory to reality. The synthesis of murine monoclonal antibodies (mAbs) was the first success in this field, leading to the invention of chimerization, the production of variable fragments (Fv) with the progression to domain antibodies (dAb) and later humanization technologies to maximize the clinical utility of murine mAbs. It was just by chance that dAbs were found to exist in ?heavy chain? immunoglobulins from Camelidae family and cartilaginous fish. These unique antibody fragments interact with antigen by virtue of only one single variable domain, referred to as VHH or nanobody. Several characteristics make nanobody use superior to the abovementioned antibodies. They are non-immunogenic and show high thermal and chemical stability. There are several reports of raising specific nanobodies against enzymes, haptens, pathogens, toxins and tumor markers, which are outlined in this paper. All these characteristics make them strong candidates as targeting agents for cancer therapy.

Regulation of porcine endogenous retrovirus release by porcine and human tetherins

The risk of transmission of porcine endogenous retrovirus (PERV) is one of the major safety issues in xenotransplantation. Human tetherin, recently described as an antiviral protein able to inhibit the release of enveloped viruses, and its porcine homologue were shown to inhibit PERV release from producer cells, establishing themselves as candidate molecules to suppress PERV production in porcine xenografts by animal engineering.

Next generation immunotherapeutics--honing the magic bullet

Most therapeutic antibodies in the clinic today are based on fully humanised immunoglobulins. They have proven to be outstandingly effective, especially for the treatment of cancer, autoimmune and inflammatory diseases where the target is a single, well-defined and accessible molecule. Many diseases however are complex, involving multiple mediators or signalling pathways that could be targeted simultaneously to maximise clinical benefit. There is also a wealth of validated intracellular and CNS-based targets which are currently inaccessible to monoclonal antibody therapy. A spectrum of next generation immunotherapeutics is in development to address these issues and a number of them have also entered clinical trials.

Single domain antibodies: promising experimental and therapeutic tools in infection and immunity

Antibodies are important tools for experimental research and medical applications. Most antibodies are composed of two heavy and two light chains. Both chains contribute to the antigen-binding site which is usually flat or concave. In addition to these conventional antibodies, llamas, other camelids, and sharks also produce antibodies composed only of heavy chains. The antigen-binding site of these unusual heavy chain antibodies (hcAbs) is formed only by a single domain, designated VHH in camelid hcAbs and VNAR in shark hcAbs. VHH and VNAR are easily produced as recombinant proteins, designated single domain antibodies (sdAbs) or nanobodies. The CDR3 region of these sdAbs possesses the extraordinary capacity to form long fingerlike extensions that can extend into cavities on antigens, e.g., the active site crevice of enzymes. Other advantageous features of nanobodies include their small size, high solubility, thermal stability, refolding capacity, and good tissue penetration in vivo. Here we review the results of several recent proof-of-principle studies that open the exciting perspective of using sdAbs for modulating immune functions and for targeting toxins and microbes.

Reverse proteomic antibody screening identifies anti adhesive VHH targeting VLA-3

Therapeutic approaches aimed at targeting tumor surface markers using monoclonal antibodies provide a powerful strategy in cancer treatment. Here we report selection of single variable domains (VHH) of llama heavy chain antibodies, using a VHH-phage-display library. A reverse proteomic approach was used to identify the cognate proteins recognized by enriched VHH on HeLa cells. One of these VHH bound the integrin alpha 3 beta 1 (VLA-3) and was further characterized. Most interestingly, this VHH could inhibit VLA-3 mediated cell-matrix adhesion. Our approach provides a fast and efficient method to screen for novel cell surface markers on normal and tumor cells that may find diagnostic or therapeutic application in disease management or treatment.

Ricin detection using phage displayed single domain antibodies

Phage-displayed single domain antibodies (sdAb) were compared to monomeric solubly expressed sdAb and llama polyclonal antibodies for the detection of ricin. SdAb are comprised of the variable domain derived from camelid heavy chain only antibodies (HcAb). Although HcAb lack variable light chains, they as well as their derivative sdAb are able to bind antigens with high affinity. The small size of sdAb (∼16 kDa), while advantageous in many respects, limits the number of labels that can be incorporated. The ability to incorporate multiple labels is a beneficial attribute for reporter elements. Opportunely, sdAb are often selected using phage display methodology. Using sdAb displayed on bacteriophage M13 as the reporter element gives the potential for incorporating a very high number of labels. We have demonstrated the use of both sdAb and phage- displayed sdAb for the detection of ricin using both enzyme linked immunosorbent assays (ELISAs) and Luminex fluid array assays. The phage-displayed sdAb led to five to ten fold better detection of ricin in both the ELISA and Luminex assays, resulting in limits of detection of 1 ng/mL and 64 pg/mL respectively. The phage-displayed sdAb were also dramatically more effective for the visualization of binding to target in nitrocellulose dot blot assays, a method frequently used for epitope mapping.

Llama-derived single-domain intrabodies inhibit secretion of hepatitis B virions in mice

Hepatitis B virus (HBV) infections cause 500,000 to 700,000 deaths per year as a consequence of chronic hepatitis, cirrhosis, and hepatocellular carcinoma. Efficient and safe antivirals to treat chronically infected patients and consequently to prevent development of hepatocellular carcinoma are still awaited. We isolated five single-domain antibodies (VHHs) that recognize the most abundant envelope protein (S) of HBV. VHHs, when expressed and retained in the endoplasmic reticulum as intrabodies, reduced levels of secreted hepatitis B surface antigen (HBsAg) particles in a cellular HBV model. In a hydrodynamics-based HBV mouse model, these intrabodies caused a marked reduction in HBsAg concentrations and a 10- to >100-fold reduction in the concentration of HBV virions in plasma.

CONCLUSION

VHHs potently inhibited secretion of HBV virions in vivo, showing that this approach might be useful in the treatment of HBV. To our knowledge, this is the first report of intrabody-mediated inhibition of viral secretion in mammals.

Isolation of Novel EGFR-Specific VHH Domains

Epidermal growth factor receptor (EGFR) is overexpressed or mutated in a high percentage of tumors. EGFR has long been considered a promising target for cancer diagnostic and therapeutic applications. However, monoclonal antibodies and other large antibody constructs diffuse into tumors slowly, limiting their efficacy. To develop lower molecular weight probes for EGFR and other tumor cell receptors, the authors immunized a llama with the extracellular domains (ECDs) of EGFR and an oncogenic mutant receptor, EGFRvIII, and with extracts of tumor cell lines. From the immune repertoire of the llama, the authors constructed a heavy chain variable domain (VHH domain)—phage library. At ~16 kDa, the VHH domain is a tenth of the size of a monoclonal antibody and is the smallest antibody fragment that retains specificity. By affinity selection from this library, the authors isolated many VHH domains with specificity for EGFR. The VHH domains bind to whole cells expressing the receptor but not to control cells lacking the receptor and can immunoprecipitate EGFR from cell lysates. Some VHH domains have cross-specificity with existing anti-EGFR monoclonal antibodies and have reasonably high (nM) affinities. The llama-VHH domain library is also potentially a rich source of targeting agents directed toward other tumor cell receptors. ( Journal of Biomolecular Screening 2009:77-85)

Strategies to enhance the safety profile of xenotransplantation: minimizing the risk of viral zoonoses

PURPOSE OF REVIEW

Pig-to-human xenotransplantation has taken steps closer to reality through advances in animal engineering to address immunological as well as microbial problems. The most highlighted problem in xenotransplantation safety has been the potential risk for zoonotic infection mediated by porcine endogenous retroviruses. Safety issues regarding viral zoonosis, particularly porcine endogenous retroviruses, are summarized and commented upon.

RECENT FINDINGS

Several molecular, transgenic strategies to provide safer transplant source animals with less porcine endogenous retrovirus infectivity have been developed. A genomics approach by selective breeding and porcine endogenous retrovirus loci knockout is at least theoretically possible. For other viruses, advances have been made in technologies for virus discovery and identification.

SUMMARY

The consequences of possible zoonoses in xenotransplantation are largely unknown. Further work to identify and control potential zoonotic agents based on recent progress will improve the safety profile of xenotransplantation. Advances made should be subjected to cautious testing in well controlled, preclinical and clinical experiments.

Identification of single‐domain, Bax‐specific intrabodies that confer resistance to mammalian cells against oxidative‐stress‐induced apoptosis

Bax is a proapoptotic protein implicated in cell death involved in several neurodegenerative diseases. Intracellularly expressed antibody (Ab) fragments (intrabodies) inhibiting Bax function would have potential for developing therapeutics for the aforementioned diseases and can serve as research tools. We report identification, cloning, and functional characterization of several Bax-specific single-domain antibodies (sdAbs). These minimal size Ab fragments, which were isolated from a llama V(H)H phage display library by panning, inhibited Bax function in in vitro assays. Importantly, as intrabodies, these sdAbs, which were stably expressed in mammalian cells, were nontoxic to their host cells and rendered them highly resistant to oxidative-stress-induced apoptosis. The intrabodies prevented mitochondrial membrane potential collapse and apoptosis after oxidative stress in the host cells. These anti-Bax V(H)Hs could be used as tools for studying the role of Bax in oxidative-stress-induced apoptosis and for developing novel therapeutics for the degenerative diseases involving oxidative stress.

Generation of heavy-chain-only antibodies in mice

We have generated transgenic mice containing hybrid llama/human antibody loci that contain two llama variable regions and the human D, J, and Cmu and/or Cgamma constant regions. Such loci rearrange productively and rescue B cell development efficiently without LC rearrangement. Heavy-chain-only antibodies (HCAb) are expressed at high levels, provided that the CH1 domain is deleted from the constant regions. HCAb production does not require an IgM stage for effective pre-B cell signaling. Antigen-specific heavy-chain-only IgM or IgGs are produced upon immunization. The IgG is dimeric, whereas IgM is multimeric. The chimeric HCAb loci are subject to allelic exclusion, but several copies of the transgenic locus can be rearranged and expressed successfully on the same allele in the same cell. Such cells are not subject to negative selection. The mice produce a full antibody repertoire and provide a previously undescribed avenue to produce specific human HCAb in the future.

Nanobodies as novel agents for cancer therapy

Nanobodies are the smallest fragments of naturally occurring heavy-chain antibodies that have evolved to be fully functional in the absence of a light chain. As such, the cloning and selection of antigen-specific nanobodies obviate the need for construction and screening of large libraries, and for lengthy and unpredictable in vitro affinity maturation steps. The unique and well-characterised properties enable nanobodies to excel conventional therapeutic antibodies in terms of recognising uncommon or hidden epitopes, binding into cavities or active sites of protein targets, tailoring of half-life, drug format flexibility, low immunogenic potential and ease of manufacture. Moreover, the favourable biophysical and pharmacological properties of nanobodies, together with the ease of formatting them into multifunctional protein therapeutics, leaves them ideally placed as a new generation of antibody-based therapeutics. This review describes the state of the art on nanobodies and illustrates their potential as cancer therapeutic agents.

Identification by phage display of single-domain antibody fragments specific for the ODD domain in hypoxia-inducible factor 1alpha

Hypoxia triggers the transcription of genes responsible for cell survival via the key player transcription factor hypoxia-inducible factor 1alpha (HIF-1alpha). Overexpression of this protein has been implicated in cardiovascular disorders, carcinogenesis and cancer progression. For functional and diagnostic studies on the HIF-1alpha protein, we have identified single-domain antibody fragments directed against this protein by using a llama-derived nonimmune phage display library. This library displays the variable domains of the heavy-chain antibody subclass, found in these animals. Phage display selection with six recombinant HIF-1alpha proteins yielded five different antibody fragments. By epitope-mapping, we show that all five antibody fragments bind within the functionally important oxygen-dependent degradation domain of the HIF-1alpha protein. Two of these antibody fragments were engineered into bivalent antibodies that were able to detect human HIF-1alpha by immunohistochemistry, Western blotting and immunoprecipitation, and mouse HIF-1alpha by immunofluorescence and immunoprecipitation. These are the first single-domain antibody fragments that may be used in exploration of HIF-1alpha as a possible therapeutic target through molecular applications.

Prevention of oculopharyngeal muscular dystrophy-associated aggregation of nuclear poly(A)-binding protein with a single-domain intracellular antibody

Oculopharyngeal muscular dystrophy (OPMD) belongs to the group of protein aggregation disorders and is caused by extensions of the N-terminal polyalanine stretch of the nuclear polyA-binding protein 1 (PABPN1). The presence of PABPN1-containing intranuclear aggregates in skeletal muscle is unique for OPMD and is also observed in transgenic mouse and cell models for OPMD. These models consistently support a direct role for the protein aggregation in OPMD pathogenesis. We have isolated and characterized a diverse panel of single-domain antibody reagents (VHH), recognizing different epitopes in PABPN1. The antibody reagents specifically detect endogenous PABPN1 in cell lysates on western blot and label PABPN1 in cultured cells and muscle sections. When expressed intracellularly as intrabodies in a cellular model for OPMD, aggregation of PABPN1 was prevented in a dose-dependent manner. More importantly yet, these intrabodies could also reduce the presence of already existing aggregates. Given the domain specificity of VHH-mediated aggregation interference, this approach at least allows the definition of the nucleation kernel in aggregation-prone proteins, thus facilitating etiological insight into this and other protein aggregation disorders, and ultimately, it may well provide useful therapeutic agents.

Antigen Binding and Solubility Effects upon the Veneering of a Camel VHH in Framework-2 to Mimic a VH

Heavy chain only antibodies of camelids bind their antigens with a single domain, the VHH, which acquired adaptations relative to classical VHs to function in the absence of a VL partner. Additional CDR loop conformations, outside the canonical loop structures of VHs, broaden the repertoire of the antigen-binding site. The combined effects of part of the CDR3 that folds over the "former" VL binding site and framework-2 mutations to more hydrophilic amino acids, enhance the solubility of VHH domains and prevent VL pairing. cAbAn33, a VHH domain specific for the carbohydrate moiety of the variant surface glycoprotein of trypanosomes, has a short CDR3 loop that does not cover the former VL binding site as well as a VH-specific Trp47 instead of the VHH-specific Gly47. Resurfacing its framework-2 region (mutations Tyr37Val, Glu44Gly and Arg45Leu) to mimic that of a human VH restores the VL binding capacity. In solution, the humanised VHH behaves as a soluble, monomeric entity, albeit with reduced thermodynamic stability and affinity for its antigen. Comparison of the crystal structures of cAbAn33 and its humanised derivative reveals steric hindrance exerted by VHH-specific residues Tyr37 and Arg45 that prevent the VL domain pairing, whereas Glu44 and Arg45 are key elements to avoid insolubility of the domain.

Isolation of llama antibody fragments for prevention of dandruff by phage display in shampoo

As part of research exploring the feasibility of using antibody fragments to inhibit the growth of organisms implicated in dandruff, we isolated antibody fragments that bind to a cell surface protein of Malassezia furfur in the presence of shampoo. We found that phage display of llama single-domain antibody fragments (VHHs) can be extended to very harsh conditions, such as the presence of shampoo containing nonionic and anionic surfactants. We selected several VHHs that bind to the cell wall protein Malf1 of M. furfur, a fungus implicated in causing dandruff. In addition to high stability in the presence of shampoo, these VHHs are also stable under other denaturing conditions, such as high urea concentrations. Many of the stable VHHs were found to contain arginine at position 44. Replacement of the native amino acid at position 44 with arginine in the most stable VHH that lacked this arginine resulted in a dramatic further increase in the stability. The combination of the unique properties of VHHs together with applied phage display and protein engineering is a powerful method for obtaining highly stable VHHs that can be used in a wide range of applications.

Survey of the year 2003 commercial optical biosensor literature

In the year 2003 there was a 17% increase in the number of publications citing work performed using optical biosensor technology compared with the previous year. We collated the 962 total papers for 2003, identified the geographical regions where the work was performed, highlighted the instrument types on which it was carried out, and segregated the papers by biological system. In this overview, we spotlight 13 papers that should be on everyone's 'must read' list for 2003 and provide examples of how to identify and interpret high-quality biosensor data. Although we still find that the literature is replete with poorly performed experiments, over-interpreted results and a general lack of understanding of data analysis, we are optimistic that these shortcomings will be addressed as biosensor technology continues to mature.

Intrabodies: production and promise

Antibodies are among the most powerful tools in biological research and are presently the fastest growing category of new drug entities. It has long been a dream to harness their power to probe and modulate activities inside living cells. The binding of an antibody to an intracellular molecule has the potential to block, suppress, alter or even enhance the process mediated by that molecule. In particular, intracellular use of antibody fragments can offer an effective alternative to gene-based knockout technologies, potentially with more control and subtlety of outcome. This article outlines progress in the development of intracellular antibodies or intrabodies and highlights their potential, both as drug-discovery tools and as drug entities in their own right.