Advances in the fields of gene therapy and human genetics have made it likely that "gene doping" will become a significant factor in competitive athletics. Implanted genes which code for IGF-1, defective myostatin, myostatin inhibitors, and erythropoietin (EPO) produce major upswings in muscular strength and endurance performance and will be extremely attractive to certain athletes. New world records - and devastating auto-immune disorders - are probable consequences. BELGIAN-BLUE

Question: When would a viral infection give your running a real boost?

Answer: When the viruses carried copies of at least one of the 90 newly discovered genes which have an effect on running performance. The viruses could insert the ergogenic genetic material into the nuclei of your muscle cells - and off you would go!

Sound farfetched? It shouldn't. In 1998, H. Lee Sweeney and his colleagues at the University of Pennsylvania, working together with Nadia Rosenthal and her co-workers at Harvard University, infected mice with adeno-associated viruses (AAVs) which carried the gene coding for insulin-like growth factor I (IGF-I), a protein which stimulates muscle growth and repair (1). When these AAVs were injected into young mice, the murids' muscular growth rates became 15-to 30-percent greater than normal, and as the mice matured their muscles were super-sized, even though the animals were totally sedentary. When the AAVs were injected into middle-aged mice, muscles did not lose their strength and function as the mice grew older.

In follow-up work, Sweeney's group and a team led by Roger P. Farrar of the University of Texas-Austin injected AAVs (carrying the gene coding for IGF-I) into just one leg of laboratory rats and then asked the rodents to complete an eight-week strength-training program (a request with which the rats complied) (2). The rats carried out rodent-specific training several times week, climbing up wire ladders while weights were attached to their bodies. After eight weeks, the AAV-IGF-I treated muscles were roughly twice as strong as the muscles in the non-infected legs in the same animal. When training stopped the AAV muscles lost their strength much more slowly, compared with muscle in other legs which had engaged in strength training but had not benefited from the gene-laced viral infection.

None of this should be surprising. After all, we know that genes can play a major role in determining athletic performance, not just in rodents but also humans. Take the case of Eero Mantyranta, for example, a Finnish cross-country skier who won two gold medals at the 1964 Olympics. Recently, it was discovered that Mantyranta and indeed his entire family possess a genetic mutation that leads to an over-response to erythropoietin (EPO), the chemical which stimulates bone marrow to produce red blood cells. The result is an incredibly high number of red cells moving around in the blood - and thus an enhanced oxygen-carrying capacity and an extremely lofty maximal aerobic capacity (VO2max). Not surprisingly , many of Eero's relatives have also been champion endurance athletes (within Finland). BELGIAN-BLUE

More recently, Australian researchers discovered a gene knwn as ACTN3 which seems to play an important role in fast-twitch muscle fibers. An unusually high percentage of elite sprinters possess a copy of this gene, and top-level female sprinters tend to have two copies of ACTN3.

Serious athletes are becoming increasingly aware of the fact that such "super- performance genes" exist, and some are beginning to look into the possibility of "gene doping" - having desirable genes added to their genetic constitutions. The technology for doing so is already here. While there are different ways to supplement a human being's natural DNA constitution with outside genetic material, viruses have become a favored transporter mechanism for coveted genes, because viruses are so adept at eluding the defense thrown up by an individual's immune system.

The way in which this is accomplished is pretty simplye theory. First, researchers select a type of virus which has a low probability of producing a serious infection. They then strip down the viruses' genetic material, leaving only the genes which code for the viruses' outer "coats" ( a virus basically consists of an inner core of genetic material with a protein outer wrapper, or coat). To these coat genes, researchers add the genetic material of interest, for example the gene coding for IGF-I. The resulting, highly unusual viruses can then be injected into muscle tissue, for example, where they actually enter muscle cells and may insert the special gene into the muscle-fibers' genetic packages within their nuclei. In the case of Sweeney's IGF-I, the muscles may then go on an IGF-I production spree, and muscular growth can be dramtically enhanced. BELGIAN-BLUE

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