"The first step in the complex process of HIV (human immunodeficiency virus) infection in a woman is the virus spread from the seed to the vaginal tissue. We want to end this first step, "says Patrick Kiser, author of the study. "We created the first vaginal gel designed to prevent movement of the AIDS virus. It is a unique case. There's nothing like it."
"We have been to develop technologies that can enable women to protect themselves against HIV without the approval of their partner," he says. "This is important, especially in resource-poor areas of the world as Saharan Africa and South Asia where, in some age groups, up 60 per cent of women are already infected with HIV. In these places, women are often not empowered to force their partners to wear condoms. "
Scientists have developed a new type of "molecular condom" to protect women against AIDS in Africa and other impoverished areas. Before sex, women can insert a vaginal gel which becomes semi-solid presence semen, trapping particles of AIDS virus in a microscopic mesh, so if they can not infect vaginal cells.
Researchers have developed a vaginal gel that women can insert a few hours before intercourse and "could detect the presence of semen and to provide a protective barrier between the vaginal tissue and HIV," said Jay. "We wanted to build a gel that would prevent HIV from interacting with the vaginal tissue."
Kiser said that if everything goes well, human tests begin to freeze within three to five years, and the gel could reach the market in several years. He and Jay want to integrate an antiviral drug in the gel so that the two blocks of movement and prevents the HIV virus from replicating.
The effort to develop microbicides for intravaginal gels, rings and movies, to prevent transmission of the AIDS virus has been hesitant. The man who achieved some clinical trials in Africa failed to prevent HIV transmission, either because they were wearing anti-viral drugs that have not been long or loud enough, or because patients have not to use them. Some microbicides increased risk, possibly by irritating the vaginal lining and attract immune cells that are targeted by the virus.
In 2006, Kiser and colleagues published a study on development of a new condom "molecular" to apply vaginally in the form of liquid, turn into a layer of gel to body temperature, then in the presence of semen, liquid and turn to release an anti-HIV drugs.
Unfortunately, few antiviral drugs bind to the attack and HIV in semen. And in Africa, the air temperatures higher prevent freezing of liquid to turn it to coat the vagina equally, Kiser said.
The new "molecular condom" freeze in the current study works in the opposite direction. As the old version, it changes in response to changes in pH - acidity or alkalinity - in the vagina caused by the introduction of semen during sex. But unlike the old gel which becomes liquid at higher (less acidic) pH of semen, the new "molecular condom" is a semi-solid semen pH, forming a mesh of "reticulated" molecules.
The new gel is applied as a gel, and then becomes stronger and more impenetrable than the pH changes alter the bond strength between the freezing of two key components, which are both polymers, or long term, the chain - like molecules in many small units repeat: LRR, or acid phénylboronique, and CSA, or acid Salicylhydroxamic.
The chemical bonds between the two polymers to attach and detach continuously to the normal acid vaginal pH of about 4.8, which allows the gel to flow, Kiser said. But at a pH of 7.6 - the slightly alkaline condition when the sperm enters the vagina - the PBA and SHA polymers "crosslink" and stick close together, "he says.
Part of the new study characterizes the flow of the gel. "He runs a vaginal pH, and flow becomes slower and slower as the pH increases, and begins to act more solid on the pH of the seed," says Jay. HIV is moving slowly in the gel, even when the gel is at low pH (higher acidity) and still flows, but the virus is blocked at the higher pH caused by the entry of sperm into the vagina.
The crosslinked polymers form a mesh which is smaller than microscopic and nanoscopic the contrary - the scale of atoms and molecules - with a mesh of only 30 to 50 nanometers - or 30 to 50 billionths of a meter. (A meter is about 39 inches).
By comparison, an HIV particle is about 100 nanometers wide, measuring sperm from about 5 to 10 microns (5000 to 10,000 nanometers) in cross section, and the width of a human hair is about 100 microns (100,000 nanometers).
Kiser said that the freeze should stop viruses and other sperm, which could function as a contraceptive and can prevent infection by the herpes virus and human papillomavirus (HPV), a major cause of cervical cancer.
The gel may also help prevent HIV by blocking the movement of immune cells that seek to fight against infectious agents but are diverted by the AIDS virus.
During the study, co-authors at Northwestern University in Chicago used a sophisticated microscope to monitor the speed at which HIV particles marked by a fluorescent dye excited when they were caught in the freeze, and how the speed varies function of changes in pH.
The researchers compared the movement of HIV particles with latex particles, which revealed that, shortly acidic conditions, the HIV particles are slowed in part because their surfaces react chemically with the polymer.
By adding a drug to fight against AIDS, as tenofovir gel, the virus would have to overcome two obstacles: the barrier polymer, then the barrier of the drug, "Kiser said. Unlike an antiviral used with the old gel, tenofovir does not attack HIV directly, but also protect the immune cells in the vagina from infection.
Kiser said that after sex, vagina gradually becomes acid again, and all residual particles of HIV is inactivated by both acidity and an antiviral drug remaining in the gel, which further hinders HIV to some extent in the normal vaginal acidity.
Future work includes evaluating the potential of HIV prevention other polymers, testing of new security freeze on vaginal cells and studying how the new gel blocks the transport of
HIV in human tissue samples or vaginal hysterectomy penis and circumcision, respectively.