Delivering toxin in nanoparticles stops virus in lab study

By Nathan Seppa

Web edition: March 15, 2013
Print edition: April 20, 2013; Vol.183 #8 (p. 12)

A component of bee venom packaged in super-tiny blobs can knock out HIV, a new study finds. Researchers testing the delivery system in lab dishes report that these nanoparticles attach to and destroy the virus without damaging cells, offering an early glimpse of a technology that might — with a lot more testing — prevent HIV infection in some people.

“This is definitely a novel approach,” says Antony Gomes, a physiologist at the University of Calcutta in India, who studies the medical use of venoms. “There are very few reports available on venom-based treatment against viruses. This type of research has the potential to proceed further for product development.”

Physician-researcher Joshua Hood of Washington University in St. Louis and his colleagues tested the toxin-carrying nanoparticles on HIV in the lab. The particles preferentially locked onto HIV and delivered their cargo: The venom component, a toxin called melittin, poked holes in HIV’s protective protein coat, leading to sharply reduced amounts of virus, the researchers report in the current issue of Antiviral Therapy.

They also tested it in healthy human cells obtained from vaginal walls. Although melittin is known to degrade cell membranes, these vaginal cells were largely unperturbed by the treatment because the nanoparticles holding the melittin come equipped with protective structures attached on their outsides. These act as bumpers to prevent the nanoparticles — and particularly the toxin they carry — from contacting the cell membrane. That allows the nanoparticle to bind to the much smaller virus using a specific lock-and-key structure that fits onto the virus’s protein shell.

The study authors tested cells from vaginal walls because the vagina is often where HIV enters the body in women. Hood suggests these early findings could prepare the way for further testing, with the long-term goal being a vaginal gel containing the nanoparticles. If such a product killed HIV on contact, the scientists note, it would be especially valuable in heterosexual couples in which one partner is infected with HIV and the other is not.

Much still needs to be mastered if this is to become a working drug, says Bruno Sarmento, a biotechnology researcher at the University of Porto, in Portugal. “Particular attention and care must be taken in order to reproduce nanoparticles in a robust and homogeneous way to guarantee uniformity of the drug,” he says. Also, a vaginal gel using this technology would need adhesive properties, Sarmento says, to guarantee that the nanoparticles remain in the right place to prevent the virus from entering the bloodstream.