Microbicides show promise as HIV Preventative
|Jul 3, 2012|
Researchers on sexually transmitted diseases are turning their attention to microbicides as an important new HIV prevention tool to expand the range of options. They are antimicrobial agents formulated as gels, creams, films, or suppositories for application to the vagina or rectum for the prevention of HIV transmission, and/or other sexually transmitted infections.
Although there has been some success in developing vaccines for two for sexually transmissible infections (Human Papilloma Virus and Hepatitis B), a vaccine for HIV appears to remain a distant dream. Thus researchers are turning to microbicides despite certain drawbacks Although funding for microbicides has climbed steadily upwards US$65 million in 2000 funding to US$217 million in 2011, it is still a far cry from the US$854 million spent annually on vaccines.
Some observers say the emphasis on vaccines is because they are more profitable to pharmaceutical companies, and that since microbicides would be targeted to very poor communities, they wouldn’t be big profit centers. Any pharmaceutical organization that develops an effective vaccine would be assured of profits as long as it continues to hold the patent. There is certainly much less income to be produced from a microbicide.
Also, at the moment, no proven dependable microbicides have been developed for sexually transmitted infections, despite the fact that some are being screened. Currently, around 60 products are at various stages of the research pipeline, from phase I to phase III trials. At least 11 have already been found to be safe and efficacious in animal studies, and have recently been started to be tested on humans.
Microbicides have various modes of action like killing/ inactivating the pathogen by disrupting the viral envelope, strengthening the vagina's defence system and maintaining acidic pH; strengthening the rectum's defence system, creating a physical barrier between the pathogen and target and preventing infection spread to other cells by blocking viral replication within cells.
Despite the availability of several prevention strategies, HIV continues to spread at an alarming rate, especially among women and men who don’t have access to existing prevention options. HIV prevention programs all over the world have promoted the use of male condoms and millions of at-risk women and men have to depend on their partner’s decision about their use. Microbicides can empower a receptive woman or man to protect both sexual partners from HIV and/or other STIs. They can have an additive effect if used in conjunction with barrier methods like male and female condoms.
An ideal microbicide needs to have certain properties. It must be safe and non-toxic, efficacious and well tolerated, inexpensive, easily applicable, widely acceptable, colorless and odorless, and available in both contraceptive and non-contraceptive forms.
“I think that the single biggest thing which safe and effective microbicides will do is to give women the power to protect themselves in a way that does not involve their partners, and now that the majority of new infections in the world are occurring among women, this is going to bring a dramatic change,” said Anna Forbes, the 2012 Omolulu Falobi Awardee and a noted women rights’ activist. “It is important that microbicides be produced in both contraceptive and non-contraceptive forms so that women who want to become pregnant still have the ability to protect themselves. Otherwise they are more likely to be used by women who do not want to become pregnant.”
If women need contraception, Forbes continued, they can buy one that protects them from HIV infection too, and not purchase two separate products. But for women who want to become pregnant, they would avoid something that includes a contraceptive.
“So it is important that we have non-contraceptive brands as well. Also right now most of the candidates being examined include anti-retroviral (ARV) drugs. A woman has to be sure that she is HIV negative before being able to use an ARV based microbicide. But women who are HIV positive will not be able to use ARV based microbicides because it would interfere with their treatment regimen and it could also cause HIV drug resistance. So non-ARV based microbicides will be very important for women living with HIV who need to protect a partner and also to protect themselves from a secondary infection of the virus.”
Badri Saxena, President of the Microbicides Society of India and Chairperson of Microbicides Expert Group of Indian Council of Medical Research (ICMR)/ Department of Health Research (DHR), pointed out that there is not a single preventive product for HIV.
“There have to be several tools available-- microbicides, vaccines and in some cases male circumcision. And there has to be better use of existing methods like male and female condoms,” Saxena said. “When there was a big epidemic of HIV-AIDS in the 1980s, America turned the tide by effective use of barrier preventive products like condoms and safe sex practices. For countries like India, Africa and China, our healthcare delivery system has to be energized. We have to improve the implementation/ effectiveness of existing technologies, and then work for newer technologies.”
That requires training of manpower, more public participation and safe sexual practices and behaviour. Indian studies have shown that in several marriages it is generally men who bring HIV to their wives. Circumcision in is not likely to work because it is restricted to the Muslim and Jewish communities. Thus microbicides can be an effective method.
“In India non-HIV STIs, like STV and cervical cancer are a big problem with an estimated 3 million people suffering from them every year. They are at-risk for HIV, so better control of such trans infections is more essential to prevent HIV in the country. New technologies are welcome because no one method suits all, and it is for men and women who are most at risk to choose,” Saxena continued.
“There is a product that is going into the phase III trial-- the vaginal ring. This is a small plastic hollow ring device that a woman can insert into her vagina and it slowly releases the contraceptive drug over a period of a month. At the end of the month she can take it out and insert a new one,” Forbes said. “It is not like something that has to be inserted in the uterus or has to be applied just before sex, thus making it more user friendly for women. There are other ARV and non ARV based microbicides too that are in the earlier pre clinical stages of development.”
For Manju Chatani Gada of AVAC: Global Advocacy for Prevention, “Microbicides add another tool for HIV prevention. Pre-exposure prophylaxis using ARVs in who are HIV negative people, voluntary male circumcision for HIV prevention, and treatment as prevention where an HIV+ individual uses treatment as a prevention of transmission to their partners are three interventions where we have seen fantastic results and the challenge is really to scale them up.
But, Gada says, “one thing we have learned is that one size does not fit all and one tool does not suit all. So in HIV too we need as many tools as possible, so that people can pick and choose what works for them to prevent HIV acquisition and transmission. Microbicides will give us what we have really been looking for, as additional tools to prevent HIV, along with existing interventions like male/ female condom use, limiting partners, loyalty relationships. They have the potential of becoming a major intervention for HIV control in the coming decades and may play a crucial role in turning the tide of the AIDS pandemic.”
(Somya Arora is a Special Correspondent to Citizen News Service (CNS) and a post-graduate in Microbiology from the University of Lucknow. Email: firstname.lastname@example.org, website: www.citizen-news.org)