Summary: Antibody labeling has been revolutionary for research into immune function and inflammation responses, and, while zebrafish are one of the prominent models for this type of research thanks to being innately suited for it, currently there is a lack of validated monoclonal antibodies for zebrafish targets. In this article we will discuss immune and inflammation research, monoclonal antibodies, and how generating validated antibodies for zebrafish research will be a driving force in better understanding and treating human diseases.
The zebrafish is a small tropical freshwater fish that has been increasingly adopted into labs across the world (~600 labs) as a model organism in inflammation, pharmacology, neurological, genetic, and toxicology research (Heath, 2020). Zebrafish are an attractive model because they are easily maintained in a lab thanks to their small size, low cost, and high reproduction rate, furthermore, their increased usage has led to technological advances such as genetically engineered strains and molecular tools.
This being said, zebrafish capabilities currently fall short in antibody labeling. Antibody labeling has been revolutionary for immune and inflammation research, as antibody labeling allows for the visualization and localization of a large and diverse set of immune cell markers in response to injury or infection. Antibodies are also used for fluorescence-assisted cell sorting (FACS) which allows access to cell-type specific transcriptional regulatory profiles, and other techniques. The lack of reliable antibodies validated in zebrafish is impeding zebrafish researchers’ ability to gain insight into inflammation and immune function — and, it is limiting new labs, who could benefit from the model’s inherent advantages, from adopting this model. So, where is the field at now, and how can this technological gap be overcome?
Zebrafish as a Model for Immune & Inflammation Research
The role of inflammation in human’s immune system, and overall health, is becoming increasingly apparent – for instance, recent microbiome research has shown that inflammation moderates everything from our risk of developing asthma and metabolic disorders, our mood and behavior, and our overall lifespan and healthspan.And, of course, a malfunctioning immune system itself drives the progression of many diseases such as atherosclerotic cardiovascular disease, Parkinson’s disease, COVID-19, multiple sclerosis, and cancer (Sattler, 2017; Netea et al., 2020).
As a vertebrate model, zebrafish have higher similarity to humans in many organs and cell types than many other simple model organisms such as C. elegans, and Drosophila. Zebrafish are particularly well-suited for immune and inflammation research as there is high conservation between zebrafish and human immune systems [Figure 1]. Furthermore, zebrafish possess unique advantages for this type of research, as zebrafish have transparent embryos that develop ex-utero which allows for easy and non-invasive observation of their development. Thus, researchers are able to study differences between innate and adaptive immune systems and inflammatory processes. Thus, utilizing zebrafish as an animal model could be game changing for some of the most prominent human diseases such as cancers, Diabetes, and IBS (irritable bowel syndrome).
Figure 1. Development of human and zebrafish immune systems (Miao et al., 2021).
What are monoclonal antibodies?
Monoclonal antibodies are one of the fastest growing products of the pharmaceutical industry, with widespread applications in biochemistry, biology, and medicine (Selişteanu et al., 2015). In biomedical research monoclonal antibodies allow researchers to label and capture protein targets. The technology to raise monoclonal antibodies against specific targets was developed in the 1970s and advancements in the field have led to this being a routine service that is offered by many providers. Many of these antibodies lack adequate validation, however, especially for assays besides western blots. Furthermore, most of these antibodies are only validated in one species (generally humans) and there is little information about cross-reactivity testing across multiple species.
The Current State of Zebrafish-validated Antibodies
The development of monoclonal antibodies against zebrafish has been attempted before, but with limited success. Currently, even antibodies that are marketed for zebrafish research are rarely tested or validated using zebrafish. Indeed, while antibodies have become a routine service provided by many companies, most are validated in humans with little to no information about cross-reactivity testing or immunohistochemistry imaging. As for the few polyclonal antibodies which have been validated with zebrafish, they suffer from batch-to-batch variability and inconsistency.
How reliable, validated antibodies could be game-changing
Currently, available antibodies for zebrafish are extremely limited and, when available, have little to no data on characterization as a reagent for zebrafish studies. Furthermore, assay and species-specific characterization is still often left to the end user, which means that researchers themselves must determine whether antibodies will react on the intended zebrafish targets (Bordeaux et al., 2010; Weller, 2018; Bandrowski, 2016). The development of zebrafish validated antibodies would be extremely beneficial for both academic and industry research applications [Figure 3].
Figure 3. How Academic and Industry sectors would benefit from antibodies validated for use in zebrafish.
With their high levels of conservation, and quick development, zebrafish provide an opportunity to accelerate our understanding of diseases, and the development of therapeutics to treat widespread, chronic diseases. Validated, reliable, zebrafish antibodies would provide the zebrafish research community with an innovative set of tools for the study and characterization of immunological targets that will allow for visualization and localization. All that’s needed now is the expansion of validated monoclonal antibodies for zebrafish targets.
Until the time when these validated monoclonal antibodies are readily available for zebrafish targets, the best option are genetic methods, such as genetically-encoded fluorescent markers to track cells or proteins.
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