The ship of the desert's pharmaceutical cargo

The smaller antibodies of the camel could help fight human viral diseases and cancer.

By | December 21, 2001

LONDON — The camel, some people scathingly suggest, is nothing better than a horse designed by a committee. If that is true, one thing is for sure: the committee must have had an immunologist as a member.

A team from the United Arab Emirates (UAE), a desert country with a quarter of a million camels, has gathered together all the current research into the animal's unique immune system. It appears that camels — whether with one hump or two — are less susceptible to a whole host of diseases, including foot and mouth disease, Rift Valley fever, mad cow disease and African horse sickness. The reason behind this is the camel's antibody structure, which is less complex than that of humans. And it's thought that this simplified structure could be used to create antibodies that could eventually help humans as well.

Most people in the West will have only see a camel in the zoo or as a cartoon picture on a Christmas card. Those few with first hand experience will tell you what an uncomfortable, unfriendly and unforgiving animal the camel can be. They make a frightening, braying noise when angered, spit and slobber, and — worst of all — are notorious for 'passing wind'. Hard to imagine, then, that they could be hiding a secret which might help to revolutionize the understanding of infectious diseases — and could even help in treatment of malignant tumors.

Sabah Jassim, who is originally from Nottingham but now works in the UAE, at the Zayed Complex for Herbal Research and Traditional Medicine, is convinced that camels offer new hope for drug companies looking for treatments for hepatitis C and HIV. "There is something really marvelous in their immunoglobulin," he said. His center has carried out an overview of the existing research into the camel's immune system, going back to 1993, and published in the latest issue of the British Institute of Biology journal, Biologist. "The camel is unique, different from any animal in the world," he explained. "The only animal with anything like it is the shark."

But camels are pretty unique animals with an interesting past as well as a fascinating physiology. Maybe the three wise men knew a thing or two when they made their fabled journey 'from the East' to Jerusalem — presumably by camel, although the Bible does not specifically say so.

The camel family evolved in North America, migrated to other parts of the world, and eventually disappeared from their country of origin. They were domesticated on a small island off the coast near Abu Dhabi, more than 4000 years ago. The Romans used camels in many parts of their Empire, which is how they spread to Europe and Asia. Similarly, the spread of the Islamic empire led to wider use of these animals.

There are now an estimated 17 million one—hump camels, 15 million of them in Africa and the Middle East and two million in India and Pakistan. There are only two million two—hump camels, mainly in the Steppes of Central Asia.

Camels are renowned for their ability to withstand long, dry desert journeys, often going without water for days. They can, however, drink as much as 100 liters in 10 minutes, given the chance. This would kill most animals, but the camel's unique metabolism enables it to store the water in its bloodstream. Water and urea are continuously recycled from the blood into the stomach. Camels have a very low urine flow and their faeces contain very little water — their dung consists of round, solid pellets which are so dry that they can be picked up by hand. They also save water by reducing how much they sweat, altering their body temperature between 34°C and 41.7°C.

The camel's hump is not, as popular myth suggests, filled with water, but is where it stores most of its body fat. As a result, the meat from the rest of its body especially healthy, as it is low in fat and contains no cholesterol. Camel milk, which tastes slightly saltier than that of a cow, is far more nutritious. It contains lower fat and lactose, higher levels of potassium, iron and vitamin C, and large concentrations of insulin — camel milk is used traditionally to treat diabetes.

Jassim cites a reference from the Koran, which suggests man should look to the camel to see how God has made them, as they should also look closely at how he has made mankind. Some people might take this suggestion with a pinch of salt; Jassim takes it at face value. He is convinced that the camel helps give the Bedouin, who regularly drink the animal's milk, a long life. "They live until they are 90 years old and are sexually very active, even into their seventies. In fact camel milk could be the new Viagra!"

But it is the structure of the camel's immunoglobulin chain that most fascinates Jassim — together with other scientists working in the field. Unlike human immunoglobulin, which has a more complex structure, with two light chains bound to the heavier Y-shaped main chain, camel immunoglobulin has only the main Y-shaped heavy chain, without these additional parts. Hamers-Casterman et al. first reported this difference in 1993 (Nature 1993, 363:446-448).

The camel's antibodies find it easier to penetrate enzyme—active sites than human antibodies. This, and the relatively small size and weight of the immunoglobulin molecule, offer enormous potential, as it could be used to tackle diseases such as salmonella, TB, hepatitis C, skin disease and HIV, argued Jassim. Camel immunoglobulin could be used to neutralize a viral enzyme, he suggested. And it appears to be able to fight off various pathogens.

Camel antibodies are also being studied by Serge Muyldermans, Senior Scientist at the Flemish Institute for Biotechnology in Brussels. He explained that, because a camel immunoglobulin molecule is much smaller than that of a human, it is able to penetrate the dense layer of protein coat around a virus or parasite more easily. His department has been developing ways of cloning immunoglobulin fragments from immunized camels to produce high yields of recombinant protein. The camel antibodies, he argued, have several advantages over conventional antibody fragments, and could be used as enzyme inhibitors, for diagnostic purposes, or even in treating tumors. "The idea is to link the camel antibody to enzymes which will bind to the tumor," he concluded.

The fact that camel antibodies are so light, proposed Jassim, makes them ideal for new clinical compounds. The antibodies have a molecular weight of 100 KDa, much lower than human antibodies, at 150 KDa, while the recombinant version weighs just 15 KDa. "I think pharmaceutical companies are not really aware of this," he said. But he thinks that camel antibodies are set to become big business in the future.

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