BOTTERON Philippe 3Sb

Biologie 5 décembre 1999

Résumé du rapport sur la mucoviscidose (anglais)

The cystic fibrosis is a genetic disease, therefore which transmits only parents to the children.

The disease is on chromosome 7, and as it is transmitted in a recessive way, it is necessarythat the two parents are carrying defective gene. To be carrying gene means of two genes tohave reached one. If the two parents are carrying, they have a chance on four to have a childreached. Moreover, the half of their succession will be carrying the disease, even if it does notappear.

In Europe, a newborn baby on 2000 is reached, and a person on 20 is carrying thedisease. Thanks to the progress already carried out in the field of the remedies against thecystic fibrosis, one arrives now at a life expectancy for the people reached which isexceptional. A patient reaches on two exceeds the 31 years. The cystic fibrosis is due to an anomaly in the cells producing mucus. It blocks the ways andcontrary to the mucus of a healthy person, it does not make it possible to evacuate dust andthe pathogenic agents. 

For more than sixty years, studies have been carried out on this disease, which condemns -almost - whoever in is suffering. Already, in 1938, at the university of Columbia, DorothyAndersen described with precision the symptoms of the cystic fibrosis and the anomalies ofthe bodies due to this disease. In 1946, one started to study the heredity of the cystic fibrosis.But they are only these ten last years that one made progress fulgurating by discovering amethod to identify genes. 

We studied the cure by genic therapy. This principle consists in introducing into the cells apiece of normal gene, which will replace that defective. Several means were tested tointroduce this gene, but none is really perfectly effective for the moment. One of the methods tested consists in transplanting a healthy gene in an adenovirus (which has a predilection forthe respiratory tracts), which was, of course, weakened in order to prevent that it starts thedisease, which it usually causes. Another virus, which one names adeno-associated virus,resembles the adenovirus much.It is not known to give diseases at the human one.

Its great characteristic is that it needs another virus (like the adenovirus) to grow normally. The potential advantages of this vector are its great security and its integration in the humangenome, which would appear by a gene expression transferred later on. The last vector is theliposome. One introduced a plasmid there (strand of ADN). This liposome will be stuck to thecellular wall, will amalgamate and pour its contents inside the cell. The influenza thus isavoided, even if the integration of the corrected genetic hardware is easier when the vector isviral. Another dimension studied is to know if one can modify a human gene. Within the frameworkof the cure of such a disease, yes. But how to differentiate a good cause from bad? In the caseor one would detect that the foetus of a woman is reached cystic fibrosis, it would be normalthat she can fall through. But what occur would if the parents wished to separate from a childonly carrying the gene, but which would not feel the effects of them, this in order to avoidproblems for the future generations?