AIDS August 2001;15:1595-1602
Brief Review: the authors think that the cervix is the key entry point for HIV. And that by combining the use of a cap by the women which protects the cervix with a microbicide HIV can be prevented. This sort of a contraceptive approach would give the woman control in sexual situations as opposed to negotiating condom use. However, the authors are merely proposing such a concept. They support their thinking with preliminary research on STD transmission, animal research, and theories which may be well based. But, in the end the authors themselves conclude that we need research studies to explore and confirm whether these approaches are effective. The authors conclude: "To our knowledge, no studies of the HIV preventive capabilities of internal barrier devices have been published, are ongoing, or are planned and funded. Clinical, epidemiological and biological evidence strongly support the hypothesis that combining a microbicide with such a barrier will enhance protection. Direct tests of this hypothesis with controlled trials are well justified and should be a high priority".
authors- Thomas R. Moench; Tsungai Chipatoa; Nancy S. Padianb >From ReProtect, LLC, Baltimore, Maryland, USA, the aDepartment of Obstetrics and Gynaecology University of Zimbabwe, Harare, Zimbabwe and bAIDS Research Unit, Department of Obstetric Gynecology & Reproductive Sciences, University of California San Francisco, California, USA.
The need for woman-controlled barrier contraceptives that protect against both bacterial and viral sexually transmitted pathogens is widely recognized. In the absence of an effective vaccine or treatment, contraceptive methods capable of preventing sexual transmission of HIV as well as other sexually transmitted diseases (STD) are vital for protecting the health of women. Moreover, widespread violence against women, double standards of sexual behavior, and the imbalance of power in many sexual partnerships make methods initiated and controlled by women critically important. These issues may severely limit existing options for protection among women who cannot negotiate sex with their male partners without being accused of cheating, of being ‘loose’ women, or of accusing their partners of infidelity.
Vaginal microbicides (topical chemical barriers that protect against acquisition of a variety of STD pathogens, including HIV) may provide such alternative woman-controlled methods. Compared to male and female condoms, microbicides are expected to interfere less with intimacy and sexual pleasure, and be more discrete. Because detergents like nonoxynol-9 (N9) are microbicidal as well as spermicidal, several existing N9 contraceptives have been tested in observational and controlled trials as microbicides for HIV/STD prevention. Modest protection against Chlamydia and gonorrhea has been shown, but HIV prevention studies have yielded mixed results and overall, the protective effect for HIV appears doubtful. In fact, the most recently completed trial reported greater HIV transmission in the women using N9 compared to those using a placebo gel, possibly due to detergent-induced compromise of the epithelial barrier after intensive use. New microbicides (only some of which are spermicidal) are being developed for vaginal protection, in an effort to improve efficacy, safety, and acceptability compared to existing detergent-based products such as N9.
Although many of these new microbicides show robust activity against HIV and other STD pathogens, and some also appear to be less toxic than N9, achieving reliable protection with microbicides remains a significant challenge. We contend that the likelihood of success of such products could be greatly increased by an alternative prevention approach, namely the combination of a microbicide and an internal barrier device that protects the cervix. Like condoms, these devices (diaphragms, caps, and other novel designs) create a physical barrier that covers the cervix. Yet because they are worn completely inside the vagina, they avoid the obtrusiveness that limits the acceptability of male and female condoms. With microbicide applied on both the cervical and vaginal sides of these devices (as is commonly recommended for contraception in the UK, but not in the USA or other countries), they should offer all the benefits of the microbicide, with additional benefits provided by physical protection of the cervix.
Although internal barrier devices cover the cervix, they do not provide a barrier for most of the vaginal epithelium. Thus, if transmission susceptibility were distributed equally across all epithelial surfaces, internal barrier devices might add only modestly to the protection given by the microbicides with which they were used. However, substantial epidemiological and biological evidence suggests that susceptibility is not evenly distributed, but that the cervix is a site of particularly high susceptibility to HIV and STD transmission. Thus, internal barrier devices that cover the cervix may enhance significantly the protection against HIV and STD that may be provided by microbicides alone. In addition, applying the microbicide to the vaginal side of the barrier may confer vaginal protection as well.
Currently the traditional diaphragm and cervical cap are the only tested and approved internal devices that provide physical protection of the cervix. However, several new barrier methods are under development or at various stages of testing. These method include the Leah's shield (similar to a loose fitting cervical cap made of rubber with a loop for easy removal), the Femcap (also similar to the cervical cap but with a brim designed to fit into the vaginal fornices), the SILCS diaphragm [a new single-size design (SILCS Inc., Tinton Falls, New Jersey, USA) expected to be easier to insert and remove], and disposable diaphragms (some of which may be provided with microbicide preapplied).
Evidence for the importance of the cervix in acquisition of STD and HIV
Cervical infection with bacterial STD
Although to date, there have been no experimental studies (i.e., controlled trials) to evaluate the effect of diaphragm use and STD acquisition, there have been several observational studies (case–control or cross-sectional designs) that report a protective effect of diaphragms in decreasing susceptibility to STD and associated long-term sequelae. All of the studies compared diaphragm users to non-users, and all used some type of multivariate analysis to control for known co-factors or confounders such as socioeconomic status or age. Although not always specified, in most studies women who used diaphragms used them together with spermicides. Thus, although we cannot separate the protective effect of diaphragms from that conferred by spermicides used alone, this limitation does not affect our fundamental argument that diaphragms used together with microbicides may offer significant protection. Table 1 summarizes these results. Because the majority of these studies were not designed to test the efficacy of the diaphragm as their primary objective, and (as stated above), because they are all observational studies and thus subject to biases inherent in that design, results in the table must be seen as suggestive rather than definitive.
The susceptibility of the cervix to HIV
To date, no studies have examined the protective effect of physical coverage of the cervix and HIV acquisition. However, because of its fragility, frequent compromise by classical STD, and the presence of HIV receptor sites (all of which are discussed below), the cervix is probably more susceptible to HIV than is the vaginal tissue. The importance of the cervix in acquisition of HIV infection is suggested by a recent experiment in which rhesus macaques were infected vaginally with SIV . Using in situ hybridization to detect SIV-infected cells, the first cellular targets were found to be located in the lamina propria of the columnar endocervical epithelium. These cervical cells were detectably infected by day 3, whereas the vaginal mucosa was not infected until day 12, a time when virus was systemically disseminated. Thus, the cervix appeared to be the site of initial infectious entry. The cervix may also serve as a portal allowing pathogen access to the upper genital tract. Human cervical tissue section explants are easily infectable with HIV, as are uterine and fallopian tube sections . This suggests that upper tract access may be followed by infectious entry of HIV.
As is apparent from these results and those reported for STD above, overall, there is a consistent indication that the cervix is an important infection site for STD and HIV. Below we review biological mechanisms that may account for these observations.
The articles goes on to explore the authors research in animals and with STDs in supporting why the cervix appears to be a place where if protected from HIV infection can be prevented. They contend the cervix is a likely site of entry for STDs and HIV. Their is some conflicting research both supporting and not supporting that the cervix is a key site for transmission of HIV and the articles discusses both sides of the research but obviously the study authors think the cervix is the key site.