Nanobodies from camels and llamas may solve the lack of effective snakebite treatments

Imagine being bitten by a snake.

Luckily you manage to get to the hospital and they have antivenom available. But now you realize that although there is a drug, it is not known if it will be effective.

This is not a plot from a horror movie, but a real-world issue that many people, especially in rural and tropical areas, face regularly.

Snakebite envenomation remains a significant global health concern, affecting over 2.7 million people annually, leading to more than 100,000 deaths and three times as many amputations and other severe health consequences.

Although some antivenoms exist, they are not always very effective. Moreover, the existing antivenoms can cause severe side effects and are expensive to produce.

The need for better treatment against deadly snakebites is thus urgent, and in our research group we have just tested a new technology to produce antivenom by discovering tiny antibodies from camels and llamas that show promising results in mice.

Distinct snake species have different venoms with multiple toxins

One of the challenges in treating snakebites is the complexity of snake venom. You can read more about this in this Videnskab.dk-article written by our colleagues at DTU.

For example, coral snakes, a group particularly notorious in the Americas, possess venom that can vary significantly between the over 80 species that exist.

If left untreated, these envenomations potentially can lead to respiratory failure and death of the patient.

The complexity and variability between different snake venoms make it very difficult to develop effective treatments because a one-size-fits-all antivenom simply does not exist and would not make sense to make.

Fortunately, it can be done for specific groups of snakes with similar venoms.

In our recent study in Nature Communications, we delve deep into this issue, presenting the development of an "oligoclonal" mixture of nanobodies that can neutralize the venoms of at least two North American coral snakes effectively when tested in mice.

This finding shows promise for the development of a new kind of antivenom that could be used for treatment of different snakebites, and which can be produced using modern biotechnological processes, unlike traditional antivenoms

Nanobodies from camels and llamas

Traditionally, antivenoms are produced by immunizing horses or sheep with snake venom and then harvesting the generated antibodies, which can neutralize the venom.

However, this type of antivenoms have several drawbacks, including the risk of causing severe allergic reactions when given to patients, limited effectiveness against a range of venom toxins, and there is a high costs associated with producing sufficient quantities.

Therefore, researchers (including ourselves) have turned to the world of recombinant DNA technology.

The technology makes it possible to take the genes that encode tiny antibodies, also called ‘nanobodies’, from camels and llamas and produce these nanobodies using cells and bioreactors in a fermentation process similar to how beer is brewed.

Nanobodies are not only smaller and more stable than conventional antibodies, they can also be engineered in the lab to target specific toxins.

Their small size and ability to target toxins with high precision could potentially lead to the development of antivenoms that are more effective, less expensive to produce, and less likely to cause adverse reactions in patients compared to conventional animal-derived antivenoms.

Existing antivenoms contain unnecessary antibodies

The difficulty of creating antivenoms stems from the need to neutralize a diverse array of venom toxins effectively.

Traditional antivenoms often struggle with this because they are polyclonal, meaning they contain an unknown mix of antibodies that may not all be necessary for neutralizing the venom in question and may also lack antibodies against some toxins.

Oligoclonal mixtures, which is what we work with, can on the other hand be tailormade and consist of just a few deliberately chosen unique nanobodies that are mixed carefully together, so that the final product (the antivenom) has a defined composition.

These nanobodies only target the most medically relevant toxins, reducing the risk of including unnecessary components in the drug and at the same time increase the potency of the antivenom.

The process is described in the illustration below.

Defined mixtures of nanobodies can save envenomed mice

In our study, we employed ‘phage display technology’. This method allows millions of nanobodies to be tested in the lab for binding to the toxin of interest.

The methodology can be adopted to enable discovery of broadly-neutralizing nanobodies that are capable of binding to multiple similar toxins even from different snake species.

Once the nanobodies are shown to bind the individual medically relevant toxins, they can be combined in different defined mixtures and analyzed for neutralization of whole venoms.

This is done in mouse experiments where mice are injected with venom and an oligoclonal nanobody mixture and the survival of the mice is monitored.

In our recent study, we showed that by mixing two nanobodies that neutralize two different toxin families, we could save all mice that were injected with whole venom from two different coral snakes.

Recombinant antivenoms show promise for the development of better treatments

However, there are challenges ahead.

The complexity and diversity of snake venoms mean that researchers need to ensure that these or other nanobodies are effective across venoms from different snake species and across venoms from the same species from different geographical regions.

Moreover, the clinical efficacy of these antivenoms needs to be validated in humans, a process that can be lengthy and complicated by regulatory requirements and is associated with huge costs.

Despite these challenges, the development of recombinant nanobody-based antivenoms represents a significant technological step forward in the fight against snakebite envenomation.

It not only holds the potential to provide more effective and safer treatments, but also illustrates the power of modern biotechnology to address longstanding public health challenges.

As we continue to explore the capabilities of these remarkable molecules, the hope is that someday in the future, snakebite victims everywhere can receive an effective and safe treatment.

A treatment, that can neutralize medically important snake venoms and allow the victims to recover without severe consequences. The road is long, but the direction is promising.

Sources

• Melisa Benard-Valles profile (DTU)
• Anne Ljungars profile (DTU)
• Andreas H. Laustsen-Kiels profile (DTU)
  
• 'In vivo neutralization of coral snake venoms with an oligoclonal nanobody mixture in a murine challenge model'  Nat Commun, (2024), DOI: 10.1038/s41467-024-48539-z