Generation and selection of naïve Fab library for parasitic antigen: Anti‐ Bm SXP antibodies for lymphatic filariasis

A review of in vitro stochastic and non-stochastic affinity maturation strategies for phage display derived monoclonal antibodies

Monoclonal antibodies identified using display technologies like phage display occasionally suffers from a lack of affinity making it unsuitable for application. This drawback is circumvented with the application of affinity maturation. Affinity maturation is an essential step in the natural evolution of antibodies in the immune system. The evolution of molecular based methods has seen the development of various mutagenesis approaches. This allows for the natural evolutionary process during somatic hypermutation to be replicated in the laboratories for affinity maturation to fine-tune the affinity and selectivity of antibodies. In this review, we will discuss affinity maturation strategies for mAbs generated through phage display systems. The review will highlight various in vitro stochastic and non-stochastic affinity maturation approaches that includes but are not limited to random mutagenesis, site-directed mutagenesis, and gene synthesis.

Review of phage display: A jack-of-all-trades and master of most biomolecule display

Phage display was first described by George P. Smith when it was shown that virus particles were capable of presenting foreign proteins on their surface. The technology has paved the way for the evolution of various biomolecules presentation and diverse selection strategies. This unique feature has been applied as a versatile platform for numerous applications in drug discovery, protein engineering, diagnostics, and vaccine development. Over the decades, the limits of biomolecules displayed on phage particles have expanded from peptides to proteomes and even alternative scaffolds. This has allowed phage display to be viewed as a versatile display platform to accommodate various biomolecules ranging from small peptides to larger proteomes which has significantly impacted advancements in the biomedical industry. This review will explore the vast array of biomolecules that have been successfully employed in phage display technology in biomedical research.

Emergence of zoonotic Brugia pahangi parasite in Thailand

Zoonotic Brugia pahangi parasite infections in humans have emerged over two decades in Southeast Asia (SEA), including Malaysia and Thailand. The species is commonly found in domestic cats and dogs as the natural reservoir hosts. The sporadic transmission pattern of B. pahangi zoonosis causes childhood infections in Thailand and adulthood infections in Malaysia. It is crucial to understand the vulnerability in how zoonotic B. pahangi parasite is transmitted to susceptible persons in receptive settings and the exposure to the infection under impoverished environment to which the human-vector-animal interactions are related. This acquisition of knowledge will help multiple health science professions to apply One Health approach to strengthening the capacity in diagnosis and surveillance, and hence detecting and monitoring the "lingering" zoonotic B. pahangi infections present in vulnerable populations in Thailand and elsewhere in SEA. In this review article, the authors focused on articulating the concepts of plantation-related zoonotic B. pahangi filariasis by updating current knowledge of B. pahangi life cycle, vector's life cycle and current state of research on the epidemiology and ecology of B. pahangi zoonosis.

Construction of Naïve and Immune Human Fab Phage Display Library

Phage display has been applied successfully for the rapid isolation of monoclonal antibodies against various targets including infectious diseases, autoantigens, cancer markers, and even small molecules. The main component in any phage display experiment is the availability of an antibody library to carry out the selection process of target-specific antibodies through an iterative process termed as biopanning. To generate human antibody libraries, the antibody repertoire can be obtained from human peripheral blood mononuclear cell (PBMC) or directly from cell-sorted B-cell populations. The choice of antibody isotype is dictated by the nature of the library. Naïve libraries would utilize IgM repertoires, whereas the IgG repertoire is commonly used for immune libraries. Antibody genes are amplified through polymerase chain reaction (PCR) and paired in a combinatorial fashion to expand the diversity of the cloned library repertoire. The protocol here describes the use of a two-step cloning method that can be applied for the construction of either a naïve or immune human antibody library in Fab format followed by the subsequent panning.

Antibody Phage Display

The application of antibodies has transcended across many areas of work but mainly as a research tool, for diagnostic and for therapeutic applications. Antibodies are immunoproteins from vertebrates that have the unique property of specifically binding foreign molecules and distinguish target antigens. This property allows antibodies to effectively protect the host from infections. Apart from the hybridoma technology using transgenic animals, antibody phage display is commonly considered the gold standard technique for the isolation of human monoclonal antibodies. The concept of antibody phage display surrounds the ability to display antibody fragments on the surface of M13 bacteriophage particles with the corresponding gene packaged within the particle. A repetitive in vitro affinity based selection process permits the enrichment of target specific binders. This process of recombinant human monoclonal antibody generation also enables additional engineering for various applications. This makes phage display an indispensable technique for antibody development and engineering activities.

Recombinant antigens used as diagnostic tools for lymphatic filariasis

Lymphatic filariasis (LF) is a parasitic disease caused by the worms Wuchereria bancrofti, Brugia malayi, or Brugia timori. It is a tropical and subtropical illness that affects approximately 67 million people worldwide and that still requires better diagnostic tools to prevent its spread and enhance the effectiveness of control procedures. Traditional parasitological tests and diagnostic methods based on whole protein extracts from different worms are known for problems related to sample time collection, sensitivity, and specificity. More recently, new diagnostic tools based on immunological methods using recombinant antigens have been developed. The current review describes the several recombinant antigens used as tools for lymphatic filariasis diagnosis in antigen and antibody capture assays, highlighting their advantages and limitations as well as the main commercial tests developed based on them. The literature chronology is from 1991 to 2021. First, it describes the historical background related to the identification of relevant antigens and the generation of the recombinant polypeptides used for the LF diagnosis, also detailing features specific to each antigen. The subsequent section then discusses the use of those proteins to develop antigen and antibody capture tests to detect LF. So far, studies focusing on antibody capture assays are based on 13 different antigens with at least six commercially available tests, with five proteins further used for the development of antigen capture tests. Five antigens explored in this paper belong to the SXP/RAL-2 family (BmSXP, Bm14, WbSXP-1, Wb14, WbL), and the others are BmShp-1, Bm33, BmR1, BmVAH, WbVAH, BmALT-1, BmALT-2, and Wb123. It is expected that advances in research with these antigens will allow further development of tests combining both sensitivity and specificity with low costs, assisting the Global Program to Eliminate Lymphatic Filariasis (GPELF).

Antibody display technologies: selecting the cream of the crop

Antibody display technologies enable the successful isolation of antigen-specific antibodies with therapeutic potential. The key feature that facilitates the selection of an antibody with prescribed properties is the coupling of the protein variant to its genetic information and is referred to as genotype phenotype coupling. There are several different platform technologies based on prokaryotic organisms as well as strategies employing higher eukaryotes. Among those, phage display is the most established system with more than a dozen of therapeutic antibodies approved for therapy that have been discovered or engineered using this approach. In recent years several other technologies gained a certain level of maturity, most strikingly mammalian display. In this review, we delineate the most important selection systems with respect to antibody generation with an emphasis on recent developments.

Cognizance of Molecular Methods for the Generation of Mutagenic Phage Display Antibody Libraries for Affinity Maturation

Antibodies leverage on their unique architecture to bind with an array of antigens. The strength of interaction has a direct relation to the affinity of the antibodies towards the antigen. In vivo affinity maturation is performed through multiple rounds of somatic hypermutation and selection in the germinal centre. This unique process involves intricate sequence rearrangements at the gene level via molecular mechanisms. The emergence of in vitro display technologies, mainly phage display and recombinant DNA technology, has helped revolutionize the way antibody improvements are being carried out in the laboratory. The adaptation of molecular approaches in vitro to replicate the in vivo processes has allowed for improvements in the way recombinant antibodies are designed and tuned. Combinatorial libraries, consisting of a myriad of possible antibodies, are capable of replicating the diversity of the natural human antibody repertoire. The isolation of target-specific antibodies with specific affinity characteristics can also be accomplished through modification of stringent protocols. Despite the ability to screen and select for high-affinity binders, some 'fine tuning' may be required to enhance antibody binding in terms of its affinity. This review will provide a brief account of phage display technology used for antibody generation followed by a summary of different combinatorial library characteristics. The review will focus on available strategies, which include molecular approaches, next generation sequencing, and in silico approaches used for antibody affinity maturation in both therapeutic and diagnostic applications.