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Thinking Outside the Box (of Condoms)

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Imagine a product for women that is discrete, convenient, and provides long-lasting protection against genital herpes infection. Recently published research in Cell Host & Microbe indicates that such a product may one day no longer be left to the imagination.  Researchers from Albert Einstein College of Medicine of Yeshiva University and Harvard Medical School discovered that a topical microbicide, administered vaginally, protected female mice against HSV-2 for up to a week.  Sustained and immediate protection occurred as a result of the cream targeting the herpes virus receptor Nectin-1 and UL29 gene.  Additionally, researchers used siRNAs to thwart genital irritation and reported the cream did not induce inflammatory response. The results from this study are promising but successful animal studies do not always equate to success in humans.  However, this encouraging news does draw attention to the growing body of research on microbicides.

So, what are microbicides?  Microbicides as defined by the World Health Organization are “compounds that can be applied inside the vagina or rectum to protect against STIs [sexually transmitted infections] including HIV.” While much research and media attention had focused on microbicides and the prevention of HIV, microbicides have the potential to prevent other STIs as well, including genital herpes. Currently, there are no microbicides commercially available, but there are numerous ones under study.

Providing options
So why the microbicide research, when we have condoms?  Well, this question could be answered several ways depending on the microbicide advocate you’re speaking with at the moment.

But one of the recurring answers involves the issue of compliance.  Though condoms are helpful in the prevention of STIs and HIV, they are most helpful when used consistently.  Reasons given for inconsistent use may range from less sexual sensation, latex allergy (though polyurethane condoms are available as an alternative), difficulty maintaining erections to inconvenience, just to name a few. Being able to apply a microbicide that offers protection for a week may eliminate the inconvenience some mention with having to put a condom on immediately before sexual intercourse.

One question frequently posed to the ASHA STI Resource Center by those with genital herpes is “how do I get pregnant without infecting my partner?”  Microbicides may be an option for those in this dilemma.  Unlike condoms, which are contraceptives, there are some microbicides under development that prevent pregnancy in addition to STIs and there are some that do not prevent pregnancy, only STIs.  So what happens once a women becomes pregnant-are they to discontinue the use of microbicides?  Since the safety of using microbicides during pregnancy is unknown, researchers usually ask women participating in microbicide trials to be contracepted to prevent pregnancy during the trial.  However, in some instances women have become pregnant during trials and this has prompted research into this area.  Hopefully, this research will not only answer questions related to the safety of use during pregnancy but also whether or not microbicides are a viable option for reducing mother to child transmission of HIV, genital herpes and other STIs.

Does this mean if microbicides are successful they will replace condoms?  For some advocates that answer is a resounding no.  Instead of replacing condoms, some see microbicides as being a product to use in conjunction with condoms.   For others the “something is better than nothing” slogan comes into play, i.e. if a person is not willing to use a condom for whatever reason but willing to use a microbicide at least they are attaining some protection which is better than none at all.  Additionally, according to researchers Wu et al., in respect to HSV-2-which has the possibility of transmission when symptoms aren’t present, “topically applied siRNAs [like those used in their microbicide] might be useful to treat and prevent reactivation and sexual transmission of clinically latent HSV-2 infection.”  For some the possibility of this additional component gives microbicides a leg up on condoms.

One frequently noted option that microbicides seem to provide is that of female empowerment.  Condoms have long been thought of as male controlled.  Female empowerment is one reason why some believe microbicides will have an appeal worldwide especially in areas with high prevalence of gender inequalities where some may not be as comfortable asking their partners to wear condoms.  Researchers Keller et al, agree that microbicides provide female empowerment and recognize the prevention option of prophylactic STI vaccines may take many years to become commercially available and that microbicides provide a realistic prevention option with worldwide appeal.

Potential problems
Genital irritation continues to be a concern with microbicides and in some cases a stumbling block in their development. Many may recall the spermicide, nonoxynol-9 was once a microbicide candidate.  However, it is no longer advocated because it causes microscopic genital skin breaks that increase a person’s risk of STI infection.  Researchers from Alnylam found the use of cholesterol siRNAs thwarts this stumbling block for their microbicide (for more information see “Alnylam Pharmaceuticals Makes New Strides with HSV Microbicide”article in this issue).  Cholesterol siRNAs were proven helpful for this particular microbicide, but not all microbicides are alike.  There are different types.  Some of the types in development include those  based on naturally occurring defenses in the body, those that block the virus from attacking cells or replicating, and those that enhance natural female defense mechanisms in the vagina.

Part of the appeal for some is the possibility of clandestine use.  Yet studies have found mixed opinions regarding clandestine use. Issues raised were whether covert use was even possible.  For example, participants in one microbicide focus group concluded clandestine use would be unsuccessful due to the microbicide’s “wetness” or “messiness.”  This view is, of course, in relation to the particular microbicide used in that study.   The lubricating qualities of various microbicides will vary.  However, the results do raise the question of whether researchers should address whether clandestine use will be of importance and if so reflect that in the product’s design.  Additionally, another focus group Smith mentions, found that male partners mostly preferred if their female partners informed them if they were using a microbicide.

What about men?
Unfortunately there is nothing in the works for a male microbicide.  However, the Global Campaign for Microbicide cautions everyone to not view microbicides as only a female issue. Reasons mentioned why men should care about microbicides also include the protection they could possibly offer the insertive partner with either vaginal or anal intercourse, and  the need for MSM to have alternatives to condoms.  Male participation in clinical trials is key because testing the safety and efficacy of a microbicide vaginally only would not be helpful if it is later found to irritate the male partner.

References
Keller, M, Tuyama A, Carlucci M, Herold BC: Topical microbicides for the prevention of genital herpes infection. J Antimicrob Chemother 2005, 55(4): 420-3.
Smith, E: Will Vaginal Microbicides Be Acceptable?  Qualitative research explores opinions and preferences of women and men. Network 2002, 22(2).
Wu Y, Navarro F, Lal A, Basar E, Pandev R, Manoharan M, et al: Durable protection from Herpes Simplex Virus-2 transmission following intravaginal application of siRNAs targeting both a viral and host gene. Cell Host Microbe 2009, 5(1):84-94.

 

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