By Sola Ogundipe
AN important step toward developing a vaginal gel that may prevent the spread of human immunodeficiency virus, HIV, may have been achieved following the discovery that nanoparticles carrying a toxin found in bee venom can destroy HIV while leaving surrounding cells unharmed.
Researchers at Washington University School of Medicine in St. Louis who made discovery which is published the current issue of Antiviral Therapy, hope that in places where HIV is running rampant, people could use this gel as a preventive measure to stop the initial infection.
Bee venom contains a potent toxin called melittin that can poke holes in the protective envelope that surrounds HIV, and other viruses. Large amounts of free melittin can cause a lot of damage. Indeed, in addition to anti-viral therapy..
The new study shows that melittin loaded onto these nanoparticles does not harm normal cells. That’s because Hood added protective bumpers to the nanoparticle surface. When the nanoparticles come into contact with normal cells, which are much larger in size, the particles simply bounce off. HIV, on the other hand, is even smaller than the nanoparticle, so HIV fits between the bumpers and makes contact with the surface of the nanoparticle, where the bee toxin awaits.
Melittin on the nanoparticles fuses with the viral envelope. The melittin forms little pore-like attack complexes and ruptures the envelope, stripping it off the virus.
An advantage of this approach is that the nanoparticle attacks an essential part of the virus’ structure. In contrast, most anti-HIV drugs inhibit the virus’s ability to replicate. But this anti-replication strategy does nothing to stop initial infection, and some strains of the virus have found ways around these drugs and reproduce anyway.
The scientists, who say they are attacking an inherent physical property of HIV, note that, theoretically, there isn’t any way for the virus to adapt to that. The virus has to have a protective coat, a double-layered membrane that covers the virus.
Beyond prevention in the form of a vaginal gel, there is potential for using nanoparticles with melittin as therapy for existing HIV infections, especially those that are drug-resistant. The nanoparticles could be injected intravenously and, in theory, would be able to clear HIV from the blood stream.
The basic particle that we are using in these experiments was developed many years ago as an artificial blood product. Although it didn’t work very well for delivering oxygen, but it circulates safely in the body and gives nice platform that can be adapted to fight different kinds of infections.
Since melittin attacks double-layered membranes indiscriminately, this concept is not limited to HIV. Many viruses, including hepatitis B and C, rely on the same kind of protective envelope and would be vulnerable to melittin-loaded nanoparticles.