Snake antivenom is a medication made up of
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
used to treat
snake bites
A snakebite is an injury caused by the bite of a snake, especially a venomous snake. A common sign of a bite from a venomous snake is the presence of two puncture wounds from the animal's fangs. Sometimes venom injection from the bite may occu ...
by venomous snakes.
It is a type of
antivenom
Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if th ...
.
It is a biological product that typically consists of venom neutralizing
antibodies
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
derived from a host animal, such as a horse or sheep. The host animal is hyperimmunized to one or more snake venoms, a process which creates an immunological response that produces large numbers of neutralizing antibodies against various components (toxins) of the venom. The antibodies are then collected from the host animal, and further processed into snake antivenom for the treatment of
envenomation
Envenomation is the process by which venom is injected by the bite or sting of a venomous animal.
Many kinds of animals, including mammals (e.g., the northern short-tailed shrew, ''Blarina brevicauda''), reptiles (e.g., the king cobra), spider ...
.
It is on the
World Health Organization's List of Essential Medicines
The WHO Model List of Essential Medicines (aka Essential Medicines List or EML), published by the World Health Organization (WHO), contains the medications considered to be most effective and safe to meet the most important needs in a health ...
.
Production
Antivenoms are typically produced using a donor animal, such as a horse or sheep. The donor animal is hyperimmunized with non-lethal doses of one or more venoms to produce a neutralizing antibody response. Then, at certain intervals, the blood from the donor animal is collected and neutralizing antibodies are purified from the blood to produce an antivenom.
Regulations
*Human Medicine: In the United States, antivenom production and distribution is regulated by the
Food and Drug Administration
The United States Food and Drug Administration (FDA or US FDA) is a List of United States federal agencies, federal agency of the United States Department of Health and Human Services, Department of Health and Human Services. The FDA is respon ...
.
*
Veterinary Medicine
Veterinary medicine is the branch of medicine that deals with the prevention, management, diagnosis, and treatment of disease, disorder, and injury in animals. Along with this, it deals with animal rearing, husbandry, breeding, research on nutri ...
: In the United States, antivenom production and distribution is regulated by the
United States Department of Agriculture
The United States Department of Agriculture (USDA) is the United States federal executive departments, federal executive department responsible for developing and executing federal laws related to farming, forestry, rural economic development, ...
's Center for Veterinary Biologics.
Classification
Monovalent vs. polyvalent
Snake
antivenom
Antivenom, also known as antivenin, venom antiserum, and antivenom immunoglobulin, is a specific treatment for envenomation. It is composed of antibodies and used to treat certain venomous bites and stings. Antivenoms are recommended only if th ...
can be classified by which antigens (venoms) were used in the production process. If the hyperimmunizing venom is obtained from a single species, then it is considered a monovalent antivenom. If the antivenom contains neutralizing antibodies raised against two or more species of snakes, then the composition is considered polyvalent.
Antibody composition
Compositions of the antivenom can be classified as whole IgG, or fragments of IgG. Whole antibody products consist of the entire antibody
molecule
A molecule is a group of two or more atoms held together by attractive forces known as chemical bonds; depending on context, the term may or may not include ions which satisfy this criterion. In quantum physics, organic chemistry, and bioch ...
, often
immunoglobulin G
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG a ...
(IgG), whereas antibody fragments are derived by digesting the whole
IgG
Immunoglobulin G (Ig G) is a type of antibody. Representing approximately 75% of serum antibodies in humans, IgG is the most common type of antibody found in blood circulation. IgG molecules are created and released by plasma B cells. Each IgG ...
into
Fab (monomeric binding) or F(ab')2 (dimeric binding). The
fragment antigen binding
The fragment antigen-binding region (Fab region) is a region on an antibody that binds to antigens. It is composed of one constant and one variable domain of each of the heavy and the light chain. The variable domain contains the paratope (the ant ...
, or Fab, is the selective antigen binding region. An antibody, such as IgG, can be digested by
papain
Papain, also known as papaya proteinase I, is a cysteine protease () enzyme present in papaya (''Carica papaya'') and mountain papaya (''Vasconcellea cundinamarcensis''). It is the namesake member of the papain-like protease family.
It has wide ...
to produce three fragments: two Fab fragments and one Fc fragment. An antibody can also be digested by
pepsin
Pepsin is an endopeptidase that breaks down proteins into smaller peptides. It is produced in the gastric chief cells of the stomach lining and is one of the main digestive enzymes in the digestive systems of humans and many other animals, w ...
to produce two fragments: a F(ab')
2 fragment and a pFc' fragment.
The fragment antigen-binding (Fab fragment) is a region on an
antibody
An antibody (Ab), also known as an immunoglobulin (Ig), is a large, Y-shaped protein used by the immune system to identify and neutralize foreign objects such as pathogenic bacteria and viruses. The antibody recognizes a unique molecule of the ...
that binds to
antigens
In immunology, an antigen (Ag) is a molecule or molecular structure or any foreign particulate matter or a pollen grain that can bind to a specific antibody or T-cell receptor. The presence of antigens in the body may trigger an immune response. ...
, such as venoms. The molecular size of Fab is approximately 50kDa, making it smaller than F(ab')
2 which is approximately 110kDa. These size differences greatly affect the tissue distribution and rates of elimination.
Cross neutralization properties
Antivenoms may also have some cross protection against a variety of
venom
Venom or zootoxin is a type of toxin produced by an animal that is actively delivered through a wound by means of a bite, sting, or similar action. The toxin is delivered through a specially evolved ''venom apparatus'', such as fangs or a sti ...
s from
snakes
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more joi ...
within the same family or
genera
Genus ( plural genera ) is a taxonomic rank used in the biological classification of living and fossil organisms as well as viruses. In the hierarchy of biological classification, genus comes above species and below family. In binomial nomenclat ...
. For instance, Antivipmyn (Instituto Bioclon) is made from the venoms of
Crotalus durissus
''Crotalus durissus'', known as the South American rattlesnake, tropical rattlesnake,Mehrtens JM. 1987. Living Snakes of the World in Color. New York: Sterling Publishers. 480 pp. and by other names, is a highly venomous pit viper species foun ...
and
Bothrops asper
Terciopelo (''Bothrops asper'') is a species of pit vipers occurring at low to moderate elevations in northeast Mexico and Central America, and into South America where it is known from elevations up to 2600 meters in the Colombian and Ecuado ...
. Antivipmyn has been shown to cross neutralize the venoms from all North American pit vipers.
Cross neutralization affords antivenom manufacturers the ability to hyperimmunize with fewer venom types to produce geographically suitable antivenoms.
Availability
Snake antivenom is complicated for manufacturers to produce. When weighed against profitability (especially for sale in poorer regions), the result is that many snake antivenoms, world-wide, are very expensive. Availability, from region to region, also varies.
Antivenom shortage for New World coral snake
, the relative rarity of coral snake bites, combined with the high costs of producing and maintaining an antivenom supply, means that antivenom (also called "antivenin") production in the United States has ceased. According to Pfizer, the owner of the company that used to make the antivenom
Coralmyn, it would take between $5–$10 million for researching a new synthetic antivenom. The cost was too high in comparison to the small number of cases presented each year. The existing American coral snake antivenom stock technically expired in 2008, but the U.S. Food and Drug Administration has extended the expiration date every year through to at least 30 April 2017.
Foreign pharmaceutical manufacturers have produced other coral snake antivenoms, but the costs of licensing them in the United States have stalled availability. Instituto Bioclon is developing a coral snake antivenom. In 2013, Pfizer was reportedly working on a new batch of antivenom but had not announced when it would become available.
[ , the Venom Immunochemistry, Pharmacology and Emergency Response (VIPER) institute of the ]University of Arizona College of Medicine
A university () is an institution of higher (or tertiary) education and research which awards academic degrees in several academic disciplines. Universities typically offer both undergraduate and postgraduate programs. In the United States, the ...
was enrolling participants in a clinical trial of INA2013, a "novel antivenom," according to the Florida Poison Information Center.
Families of venomous snakes
Over 600 species are known to be venomous—about a quarter of all snake species. The following table lists some major species.
Types
References
Further reading
*
*
{{DEFAULTSORT:Snake Antivenom
Antitoxins
Toxicology treatments