A new threat

Imagine this: at the Olympic games in London in 2012, a little known athlete surprises everyone in the men’s 100 metres, thrashing the established favourite by almost a whole second. “Is he on drugs?” everyone asks. Tests find nothing, and he is labelled a freak of nature. But are his achievements thanks to natural ability or are they down to genetic modification?

In our darkest memories, we can all recall having lied, cheated, or stretched the rules, often to gain a personal advantage. For elite athletes the pressures that drive cheating are vastly increased. Sport requires that participants train hard over long periods, often from a young age, linking achievement to self esteem, emotional state, and lifestyle. The temptations of money and fame and pressure from parents, coaches, and fans drive athletes to accept extreme risk to gain even small advantages.

Perhaps it is unsurprising that some athletes turn to science and drugs to improve their chances. In 1967 the British cyclist Tom Simpson collapsed and died on the slopes of Mont Ventoux, in France, largely because of misuse of amphetamines. As tests were developed a number of high profile cases brought doping into the public eye: Ben Johnson was stripped of his gold medal in the 1988 Olympic games, and the whole Festina team was ejected from the Tour de France in 1998 after doping equipment was found in the car of a team official.

An independent international body was established to fight doping on a global scale—the World Anti-Doping Agency. It updates the world antidoping code, which contains a list of prohibited substances and practices; coordinates the testing and education of athletes and their coaches; and funds research into testing to remain one step ahead of potential cheats.

In 2002 the agency recognised a new threat—“gene doping”—by including it in the list of prohibited practices, defined as “the non-therapeutic use of cells, genes, genetic elements, or of the modulation of gene expression, having the capacity to enhance athletic performance.

The techniques involved in gene doping are spawned from the techniques of gene therapy, in particular gene transfer with viral vectors (fig 1). The aim of gene manipulation in these two settings can be clearly distinguished. In gene therapy the goal is treatment and requires the replacement of a defective gene or expression of a therapeutic gene. Gene doping, however, aims to improve athletic performance by increasing or decreasing production of endogenous molecules.