Gli scienziati scoprono 'barriera naturale' contro 
l'HIVSOURCES: 
- Teunis Geijtenbeek, Ph.D., department of molecular cell biology 
and immunology, Vrije University Medical Center, Amsterdam, The Netherlands; 
Jeffrey Laurence, M.D., professor, medicine and director, Laboratory for AIDS 
Virus Research, Weill Cornell Medical College, New York City; Nature Medicine 
online
- Foundation for AIDS Research.
(HealthDay) - I 
ricercatori hanno scoperto che le cellule della mucosa del prepuzio, 
facente parte degli organi genitali maschili, sono in grado di produrre una 
proteina che "mangia" e distrugge il virus dell’HIV - impedendone la diffusione 
nell’organismo e possibilmente tenendo la diffusione dell’AIDS nel partner più 
contenuta di quanto potrebbe essere altrimenti.
Ancora più 
importante, migliorando le funzioni e l’attività di difesa di questa proteina, 
chiamata ”Langerin“, si potrebbe creare un nuovo potente strumento per limitare 
la trasmissione del virus che causa l'AIDS, hanno aggiunto gli scienziati 
olandesi.
Langerin is produced by Langerhans cells, which form a web-like 
network in skin and mucosa. This network is one of the first structures HIV 
confronts as it attempts to infect its host.
Un ricercatore immunologo 
presso il Vrije University Medical Center di Amsterdam, Teunis Geijtenbeek, ha 
detto che tale proteina è in grado di eliminare ogni virus proveniente 
dall’esterno dell’organismo, in modo da prevenire eventuali 
infezioni.
"And since generally all tissues on the outside of our 
bodies have Langerhans cells, we think that the human body is equipped with an 
antiviral defense mechanism, destroying incoming viruses," Geijtenbeek 
said.
The finding, reported in the March 4 online issue of Nature 
Medicine, "is very interesting and unexpected," said Dr. Jeffrey Laurence, 
director of the Laboratory for AIDS Virus Research at the Weill Cornell Medical 
College, in New York City. "It may explain part of the relative inefficiency of 
HIV in being transmitted."
Even though HIV has killed an estimated 22 
million people since it was first recognized more than 25 years ago, it is 
actually not very good at infecting humans, relatively speaking.
For example, 
the human papillomavirus (HPV), which causes cervical cancer, is nearly 100 
percent infectious, Laurence noted. That means that every encounter with the 
sexually transmitted virus will end in infection.
"On the other hand, 
during one episode of penile-vaginal intercourse with an HIV-infected partner, 
the chance that you are going to get HIV is somewhere between one in 100 and one 
in 200," Laurence said.
Experts have long puzzled why HIV is relatively 
tough to contract, compared to other pathogens. The Dutch study, conducted in 
the laboratory using Langerhans cells from 13 human donors, may explain 
why.
When HIV comes in contact with genital mucosa, its ultimate target 
-- the cells it seeks to hijack and destroy -- are immune system T-cells. But 
T-cells are relatively far away (in lymph tissues), so HIV uses nearby 
Langerhans cells as "vehicles" to migrate to T-cells.
For decades, the 
common wisdom was that HIV easily enters and infects Langerhans cells. 
Geijtenbeek's team has now cast doubt on that notion.
Looking closely at the 
interaction of HIV and Langerhans cells, they found that the cells "do not 
become infected by HIV-1, because the cells have the protein Langerin on their 
cell surface," Geijtenbeek said. "Langerin captures HIV-1 very efficiently, and 
this Langerin-bound HIV-1 is taken up (a bit like eating) by the Langerhans 
cells and destroyed."
In essence, Geijtenbeek said, "Langerhans cells act 
more like a virus vacuum cleaner."
Only in certain circumstances -- such as 
when levels of invading HIV are very high, or if Langerin activity is 
particularly weak -- are Langerhans cells overwhelmed by the virus and 
infected.
The finding is exciting for many reasons, not the least of which is 
its potential for HIV prevention, Geijtenbeek said.
"We are currently 
investigating whether we can enhance Langerin function by increasing the amount 
of Langerin on the cell surface of Langerhans cells," he said. "This might be a 
real possibility, but it will take time. I am also confident that other 
researchers will now also start exploring this possibility."
The 
discovery might also help explain differences in vulnerability to HIV infection 
among people.
"It is known that the Langerin gene is different in some 
individuals," Geijtenbeek noted. "These differences could affect the function of 
Langerin. Thus, Langerhans cells with a less functional Langerin might be more 
susceptible to HIV-1, and these individuals are more prone to infection. We are 
currently investigating this."
The finding should also impact the race to 
find topical microbicides that might protect women against HIV infection. 
Choosing compounds that allow Langerin to continue to work its magic will 
enhance any candidate microbicide's effectiveness, the Dutch researcher 
said.
Laurence did offer one note of caution, however.
"In the test tube, 
this is a very important finding," he said. "But there are many things in the 
test tube that don't occur when you get into an animal or a human. Having said 
that, though, this is a very intriguing finding."
FONTE: http://news.healingwell.com/index.php?p=news1&id=602421