Antivenom for snake bite developed in Brazil proves three times more effective than current therapy

Researchers from the Federal University of São Paulo and the Butantan Institute are working to improve antibothropic serum, with more neutralising antibodies and fewer side effects

A research group from the medical school at the Federal University of São Paulo (EPM-UNIFESP) and the Butantan Institute, in Brazil, has developed a more effective version of the antibothropic serum – or antivenom – used to treat snakebites by the genus Bothrops of which the jararaca (B. jararaca) ‘pit viper’ is the most common and is an endemic species in South America. The team’s antivenom has proved to be three times better than the currently available treatment options. 

“We combined classical techniques with the most modern ones to quantify and increase the proteins that neutralise the venom, as well as reducing other molecules that can cause side effects. 

“As a result, we obtained a serum with increased action even in smaller quantities,” said Professor Alexandre Tashima, from EPM-UNIFESP and coordinator of the study.

Serums to combat snake poisoning have been available for more than a hundred years. They are made by injecting a sublethal dose of the source venom into large animal – such as a horses – the immune system of the animal then produces antibodies against the venom’s toxins. 

Doses of the now antibody-enriched blood can then be taken from the animal – after a few days – to be processed and purified. This is called a heterologous serum and is the only proven treatment for snake poisoning. Not all of the components of the serum, however, are antibodies for use against the venom. Studies have suggested that between only 10% and 40% of the composition of these serums correspond to the proteins needed to target snake toxins.

The first steps taken by the research team were to quantify these constituents of standard antibothropic serum, by use of techniques such as affinity chromatography, surface plasmon resonance and mass spectrometry. 

The researchers found that only around 27% of the serum components interact with the toxins in jararaca venom. Other non-specific antibodies made up a large portion of the remaining 72% plus of the serum. The second most abundant protein was found to be horse albumin at around 8%.

However, horse albumin – like other mammalian albumins – can trigger an allergic response when it comes into contact with the human immune system.

“Although advances in purification have significantly reduced the incidence of adverse effects, they are still reported in 5% to 57% of cases. Most of these are due to the immune response to horse proteins such as albumin,” said Tashima.

Using affinity chromatography, the antibodies from the standard antibothropic serum – those that bind to the venom – were retained, as part of a purification phase.

The resulting serum was further analysed using the same techniques as the traditional serum with the new version showing 87% less albumin. Other unwanted proteins were further reduced by between 37% and 83%.

Functional analysis showed that the new serum had a 2.9 times greater affinity for the toxins in the venom. In addition, poisoned mice treated with the new serum required a 2.8-fold lower dose to contain the toxins.

“This suggests that the improved serum has increased potency, requiring less serum to combat the same dose of poison. 

“This together with the fact that it has fewer horse proteins is a factor that could reduce the chances of adverse effects,” said Tassia Chiarelli, first author of the study, carried out during her master’s degree at EPM-UNIFESP.

The technologies used in the purification stage are already widely used in the manufacture of other biopharmaceuticals but both clinical and regulatory stages would need to be completed before these research results can be translated into a new product.

“Innovations [such as monoclonal antibodies] will probably lead to new treatments in the future. However, we’re aware of the time and cost of these innovations, which should mean that the heterologous serum will be used for a long time to come,” the researcher concluded.

More than 5 million cases per year of snakebite poisonings occur globally, resulting in greater than 100,000 deaths and around 400,000 people becoming disabled. 

For further reading please visit: 10.1021/acs.jproteome.4c01028