New antivenom invented for black widow spider bites

When European black widows (Latrodectus tredecimguttatus) bite, they inject into their victims a powerful toxin called alpha-latrotoxin. Alpha-latrotoxin attacks the nervous system and can trigger a condition called latrodectism, in which patients experience symptoms such as severe pain, headaches and nausea. If left untreated, these debilitating symptoms can last for several days, but the condition is rarely fatal. 

People who have been bitten by a European black widow are typically prescribed pain relief medications, such as opioids and benzodiazepines, to treat their symptoms. They may also be given an antivenom containing antibodies drawn from horses that have been injected with alpha-latrotoxin and thus developed immunity against it.  

Once injected into the human body, these horse antibodies help strengthen a person's immune response to the venom, countering its effects on the nervous system. However, because the antivenom comes from horses, it may be recognized as "foreign" by the immune system. In a small number of cases, the immune system can consequently go into overdrive, sparking potentially life-threatening allergic reactions and what's known as "serum sickness." 

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The effectiveness of this horse-derived treatment can also vary considerably from one batch of antibodies to the next. 

To avoid these potential problems, researchers behind a new study, published Wednesday (June 12) in the journal Frontiers in Immunology looked to use human antibodies that are generated in the lab. The antibodies they generated target alpha-latrotoxin and could theoretically be "made to order" as and when needed, rather than having to wait for horses to make antibodies. As the new antibodies contain constituent parts that are uniquely human, they wouldn't trigger dangerous immune responses. 

So far this new antivenom has only been tested in lab dishes. But with further testing, the antibodies could eventually provide patients with a safer and more effective antivenom, Michael Hust, co-senior study author and a professor of medical biotechnology at the Technical University Braunschweig in Germany, told Live Science. 

In the new study, the team tested more than 10 billion different antibodies in the lab to determine if any were capable of binding and neutralizing alpha-latrotoxin. In all, the team identified 45 human antibodies that could do this, including one in particular, called MRU44-4-A1, which showed "outstandingly" high levels of neutralization, the team wrote in the paper. When an antivenom neutralizes a toxin, it prevents it from binding to cells and thus wreaking havoc in the body. 

L. tredecimguttatus, which is predominantly found in the Mediterranean region, is one of more than 30 types of black widow worldwide, including the southern black widows (Latrodectus mactans) that are native to North America. 

Although the newly made antibodies seem to work for L. tredecimguttatus toxin, in a separate experiment, the team discovered that only two of the antibodies were effective against the venom of L. mactans. This was "unexpected" as alpha-latrotoxin was not thought to differ between widow spiders, the team wrote in the paper. 

It could be years before the new antivenom for European black widow bites ends up in the clinic, the team said. At the very least, a couple of years of research would be needed to test the safety and effectiveness of the new antivenom in cells and animals. These results would then need to be replicated in clinical trials with humans, which could potentially take another 10 years, Maximilian Ruschig, lead study author and a doctoral candidate at the Technical University Braunschweig, told Live Science. 

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