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September 17th, 2007

A needle today keeps disease away

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Children, I have observed (and recall, for my own childhood has not yet faded into the misty depths of time) do not enjoy getting stuck with needles.

And yet, getting stuck with needles is a part of growing up, because vaccinations, unpleasant as they momentarily are, are far less unpleasant than the diseases they help prevent.

There are vaccines for diphtheria, tetanus, whooping cough and polio; for Haemophilus influenzae type b (which causes meningitis); for measles, mumps and rubella (German measles); for varicella (chicken pox) and hepatitis B. There are puneumococcal and meningococcal vaccines, and, of course, the annual influenza vaccine.

Many of us of a certain age still bear (or at least remember) the round white scar on our upper arm that marks us as recipients of smallpox vaccine. Smallpox was the first disease anyone attempted to vaccinate against: back in 600 B.C., the Chinese attempted to immunize people against smallpox by putting smallpox material in their nostrils (shudder).

Modern immunization, however, began in 1796 when British physician Edward Jenner realized that people who had had cowpox, a similar but much milder disease that carries little risk of death or disfigurement, did not catch smallpox. He inserted material from cowpox sores into cuts he made on the arm of a healthy eight-year-old boy, who caught cowpox. When the boy was exposed to smallpox eight weeks later, he did not contract smallpox.

Vaccines trick the body's immune system into treating them as a full-fledged infection. When the immune system detects foreign substances, called antigens, it creates antibodies or special white blood cells to attack them.

Traditional vaccines consist of disease-causing organisms that have been either inactivated or killed. They trigger the immune system to produce antibodies, without causing disease. If full-strength bacteria or viruses of the same type enter the body in the future, the immune system has antibodies available to attack them immediately, destroying them before they can cause infection or disease.

However, recently researchers have figured out how to generate an immune response with a single protein from a virus or bacterium. They've also discovered that the best way to get sustained immunity is to deliver an antigen directly to the specialized immune cells known as dendritic cells (DCs).

The trouble is, DCs aren't all that common in skin or muscle, where injections are usually made, and in order to use them to activate the whole immune system, you also have to deliver a kind of "danger signal"--which there hasn't been a good way to do, until now.

Researchers at the Ecole Polytechnique Fédérale de Lausanne in Switzerland have developed (and patented) a nanoparticle (“nano” means “very very small”) that, they believe, can deliver vaccines more cheaply, safely and effectively than current methods.

The nanoparticles are so tiny they slip right through the skin and into the lymph nodes, where there are lots of DCs, and they carry a chemical coating that mimics the surface chemistry of bacterial cell walls. The result: a strong immune response without nasty side effects.

The researchers believe these nanoparticles could make it possible to vaccinate against diseases like hepatitis and malaria with a single injection, and at a cost of only a dollar a dose, far cheaper than currently. They also plan to try using the technique to target cancer cells. And best of all, they say, the new technique could be in use within five years.

Many diseases that were once major killers we seldom give a second thought to in the developed, thanks to vaccinations. But measles, all but stamped out in North America, still kills hundreds of thousands a year in central Africa.

Stop vaccinating here, and those diseases could return--as was proved in Great Britain in the 1970s. After a drop in whooping cough vaccinations in 1974, an epidemic of more than 100,000 cases, resulting in 36 deaths, occurred in 1978.

If this new technology can make for cheaper vaccines, more people around the world will be vaccinated--and global public health will take a giant step forward.

That probably won’t stop children from crying as they get stuck, but it ought to at least make their parents feel better.


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