July / August 2011
The Anal Dialogues
by Trenton Straube
Can lubes increase the risk of HIV during anal sex?
A slew of recent studies suggest that using lubes for unprotected anal sex may increase the risk of HIV, and that some lubes may harm the rectum’s thin protective layer of cells (the epithelium). It’s premature to know which brands to avoid, says Marc-André LeBlanc, a lube advocate with the International Rectal Microbicide Advocates (IRMA). Most research has been done in laboratories, and it isn’t certain whether the findings translate to humans—or whether the products’ lubricating benefits outweigh their potential harm. But one fact is certain: “The best way to prevent acquiring HIV and STIs [sexually transmitted infections] during anal sex is still using male or female condoms,” LeBlanc says. “And we know that using lubes with condoms decreases the risk of the condom slipping or breaking—a big bonus.”
In the meantime, here’s a highlight of what scientists are investigating and how lube qualities might affect the success of microbicides:
Charlene Dezzutti, PhD, with the Microbicide Trials Network and the University of Pittsburgh, looked at these qualities in six popular lubes. Some findings: Pré and Wet Platinum appear safest. Pré is the only water-based lube that is iso-osmolar and doesn’t damage the epithelium. KY Jelly wiped out entire colonies of good bacteria. Astroglide is the most hyperosmolar and most toxic to cells and tissue (Elbow Grease, ID Glide and KY Jelly have similar toxicity profiles). But Dezzutti also warns that more studies are needed before any official warning or suggestions can be issued.
- Polyquaterniums, a class of chemicals common in cosmetics, seem to increase HIV replication by almost four times in lab tests. A Population Council study found this ingredient in three of four HIV-enhancing Astroglide brand lubes: Astroglide Liquid, Astroglide Warming Liquid, Astroglide Glyercin & Paraben Free liquid and Astroglide Silken Secret.
- Osmolality refers to the concentration of salts, sugars and other substances (solutes) present in a lube. Hypo-osmolar lubes have a lower concentration of solutes than human cells and cause the cells to swell with water and burst. Hyperosmolar lubes cause cells to shrink and become brittle. Iso-osmolar lubes don’t affect cells because their concentrations are identical. Most water-based lubes are hyperosmolar and damaging.
- pH balance is acidic in the vagina and neutral in the rectum. Many lubes are designed for the vagina—does the difference in pH mean they affect the rectum differently?
- Good and bad bacteria live in a delicate balance in the vagina and gut. Will disrupting this balance make the rectum more susceptible to HIV?
- Viscosity is the slippery quality that gives lube its feel and texture. Glycerin, in water-based lubes, adds to viscosity. It also makes lubes hyperosmolar—and destructive to epithelium. When a rectal microbicide now in trials proved harmful to the epithelium, researchers solved the problem by lowering the glycerin content.
Starting to Gel
Microbicides: Where they are now and where they are going
VAGINAL GEL: After two decades of disappointing results, a breakthrough arrived last summer with results of the CAPRISA 004 trial: Women using a gel containing 1 percent tenofovir (an HIV med found in Atripla, Viread and Truvada) had 39 percent fewer infections than those using a placebo. Women with 80 percent adherence to the two necessary applications per sex act (12 hours before, then immediately after) had even fewer infections. The gel also offered protection against herpes.
What’s Next: Studies are under-way to confirm CAPRISA 004 results and determine the most effective concentrations and doses, but the global economic crisis has depleted funding, slowing progress. On the bright side, the drug from the vaginal gel is showing up in rectal tissue, so one product might offer women protection in both areas.
RECTAL GEL: Microbicide Trials Network study MTN-006 looked at using the vaginal tenofovir gel rectally, with promising results announced in February. Although the vaginal formulation harmed the rectal lining and caused gastrointestinal distress, Charlene Dezzutti’s team developed a better version with less glycerin. And, says Ian McGowan, PhD, a co-principal study investigator, “We found that when you give the drug topically, you get very high concentrations in the rectal tissue—a hundred times the amount from a single Viread tablet.” A few caveats: Tenofovir works not by directly attacking and disarming HIV, but by accumulating in the tissue and CD4 cells HIV will attack, preventing HIV from replicating once it invades the cell. Unfortunately, this accumulation demands repeated doses. “I think MTN-006 suggests,” McGowan says, “that if you just take one dose, orally or rectally, half an hour before exposure, I would doubt you’d be protected.”
What’s Next: A Phase I study (MTN-007) on the safety and acceptability of the rectal tenofovir gel; and Project Gel, investigating the use of rectal microbicides among African-American and Latino men who have sex with men (MSM). “It’s critical,” McGowan says, “because these are the people who are getting infected and need the product.”
FUTURE IDEAS AND EXPERIMENTS:
Other HIV meds or combos—or completely new compounds—may offer better protection than tenofovir as microbicides (hint: HIV drugs that are too toxic as pills may work as topical solutions).
Different modes of delivery: How about a slowly dissolving ring instead of a vaginal gel? Or combining a microbicide with a vaccine, to help prepare the immune system for an encounter with HIV? And vaginal probiotics—living microbicides—could be created by genetically altering bacterial cultures such as the common lactobacilli.
Research is showing that HIV might lower the electrical barrier of epithelial cells, enabling infection even without surface damage. Such new knowledge could produce future strategies and modes of protection.
Pages: 1 | 2
Search: Anna Forbes, rectal microbicides, anal sex, vaginal microbicides, Global Campaign for Microbicides, LGBT, IRMA, Canadian AIDS Society, CHAMP International Rectal Microbicide Advocates, Julie Davids, Jim Pickett, Johns Hopkins University, AIDS Foundation Chicago, AFC, CAPRISA
Scroll down to comment on this story.
Show comments (6 total)