Pit Viper

VIPER scientists are working to improve the way we take care of pit viper bites.

The UA has a legacy of antivenom development, from before VIPER began.

When a viper bites, it injects venom containing many different chemicals that can injure the body or stop the blood from clotting normally. It's complicated. Fortunately, the immune system of vertebrate animals is also complicated, and there is a way to use the immune system to make antidotes to complicated venoms. Such an antidote is called antivenom.

Antivenom to counteract snakebite is an old-fashioned idea, going back over 100 years. We make antivenom by giving immunizations, consisting of tiny amounts of venom, to animals, in a way similar to giving a tetanus shot to a person. Then, the animal's immune system produces antibodies, molecules that can neutralize venom in the bloodstream. In decades past, antivenoms for pit viper bite (the group that includes rattlesnakes and copperheads) neutralized venom, but they also caused a lot of allergic reactions.

These older antivenoms were either of the "first generation" type (also known as "serotherapy," because it involved use of relatively unprocessed animal or human serum) or the "second generation" type (also known as "immunoglobulin therapy," because it involved use of the purified antibodies from immune animals). In both cases, allergic reactions were common, because antibody molecules -- the way they occur naturally -- send very strong signals to the body's immune system. A summary of the types of antivenom was published by Alejandro Alagón, now a VIPER-affiliated scientist at the Instituto de Biotecnología in Cuernavaca (Alagón A: Anticuerpos seguros y eficaces: la revolución de los nuevos antivenenos. Revista de la Universidad Nacional Autónoma de México 617, noviembre, 2002).

In the 1990s, faculty at the University of Arizona designed a new approach to making pit viper antivenom, one that would have fewer side effects. This new approach brought the US into the modern era of "third generation antivenoms," which are produced by altering the antibodies of immune animals to get rid of the part that causes so many allergic reactions. The story was summarized in Toxicon by John Sullivan, later a founding member of VIPER (Sullivan J.: In search of a better snake trap. Wilderness and Environmental Medicine 10: 140-41, 1999). 

Our patients and our community doctors teach us a lot.

When the time came to test the new antivenom, UA doctors were involved from the very beginning. Patients in Tucson were among the first to receive it, for treatment of rattlesnake bite. Studies at that time, and in the years that followed, confirmed that it had fewer side effects than in the past. Results of the clinical trials were published by a team including several who later helped to establish the VIPER Institute (Dart RC, et al.: A randomized multicenter trial of crotalinae polyvalent immune Fab (ovine) antivenom for the treatment of crotaline snakebite in the United States. Arch Int Med 161(16):2030-6;2001).

During these studies, observations by doctors at the UA and elsewhere raised new questions about what happens when snake venom gets into the bloodstream, and what else might be needed to improve patient care. (Boyer LV, et al.: Recurrent and persistent coagulopathy following pit viper envenomation. Arch Intern Med. 1999;12;159(7):706-10.) Preliminary data from individual patients allowed us to shape theories about how the newer generation of antivenoms was interacting with venom (Seifert SA, et al.: Relationship of venom effects to venom antigen and antivenom serum concentrations in a patient with Crotalus atrox envenomation treated with a Fab antivenom. Ann Emerg Med. 1997;30(1):49-53). Years of interesting research followed, some involving lab work and some involving patient care.

So we work toward even better treatments for the future.

Recently, VIPER scientists and doctors have tested another third generation antivenom, one that addresses the questions raised by the previous work. VIPER scientists are also working on new ways to examine the injury caused by snakebite, so that people in the US and abroad may some day have better treatments for the damaged hand or foot. VIPER is also developing new diagnostic tests, that may some day help doctors with complicated cases to decide how much treatment to give, how fast. And VIPER is expanding its membership across the United States, so that doctors in other states where pit viper bite is a problem can benefit from being part of the study team.