Antichlamydial activity of vaginal secretion

Mechanisms of action of currently available woman-controlled, vaginally administered, non-hormonal contraceptive products

Woman-controlled, vaginally administered contraceptives offer women discreet, self-administered, and reversible options. This brief report summarizes the mechanisms of action (MOAs) of currently available, woman-controlled, vaginally administered, non-hormonal products, excluding those that need to be fitted by a healthcare provider. MOAs of three general types of contraceptives will be reviewed, including pH modulators, spermicides, and barrier methods. The recently approved vaginal pH modulator (lactic acid, citric acid, and potassium bitartrate) has a non-hormonal MOA, acting as a buffering agent in the presence of alkaline semen and resulting in sperm immobilization. In contrast, spermicides, such as nonoxynol-9, act by lysing sperm membranes, resulting in sperm death. Barrier methods, such as the diaphragm and female condom, prevent sperm from entering the uterus. In addition to their varying MOAs, each woman-controlled, vaginally administered method has different instructions for use, efficacy, side effects, and availability/insurance coverage, thus providing a range of characteristics to fit different needs and preferences.

EVO100 prevents chlamydia and gonorrhea in women at high risk of infection

BACKGROUND

According to the Centers for Disease Control and Prevention, rates of infection for Chlamydia trachomatis and Neisseria gonorrhoeae are increasing in the United States. EVO100 is an investigational antimicrobial, pH-modulating, vaginal gel with active ingredients L-lactic acid, citric acid, and potassium bitartrate that is being evaluated for the prevention of sexually transmitted infections.

OBJECTIVE

The objective of this phase 2B/3 study was to assess the efficacy and safety of EVO100 for the prevention of chlamydia and gonorrhea.

STUDY DESIGN

AMPREVENCE was a double-blinded, placebo-controlled, multicenter study based in the United States conducted over approximately 16 weeks in women at the age of 18 to 45 years who were at risk of urogenital chlamydia and gonorrhea infection. Enrolled women had been diagnosed as having and treated for chlamydia or gonorrhea ≤16 weeks before enrollment. Women received either EVO100 or placebo vaginal gel and were instructed to apply the study drug immediately before or up to 1 hour before each act of vaginal sexual intercourse. The primary and secondary endpoints were the prevention of urogenital chlamydia and gonorrhea, respectively. Exploratory outcomes include women's overall satisfaction with EVO100.

RESULTS

In total, 860 women were randomized 1:1 to receive EVO100 (n=426) or placebo (n=434), and 764 women (EVO100, n=376; placebo, n=388) were documented as using the study drug at least once. Baseline characteristics were similar between treatment arms. Overall, women had a mean age of 27.7 years (standard deviation, 6.9) and body mass index of 28.9 kg/m² (standard deviation, 8.0). Most women were of White (54.3% [467 of 860]) or African American (41.6% [358 of 860]) race and of non-Hispanic/Latina ethnicity (67.1% [577 of 860]). The chlamydia infection rate in EVO100 users was 4.8% (14 of 289) compared with 9.7% (28 of 290) among placebo users (P=.0256), representing a relative risk reduction of 50%. For gonorrhea, the infection rate was 0.7% (2 of 280) in the EVO100 arm compared with 3.2% (9 of 277) in the placebo arm (P=.0316), representing a relative risk reduction of 78%. Increased efficacy was observed with increased adherence, and chlamydia infection rates were significantly reduced with increased adherence in the EVO100 group compared with placebo. Across both arms, there were similar rates of all-cause adverse events (EVO100, 21.3% [80 of 376]; placebo, 20.4% [79 of 388]) and treatment-related adverse events (EVO100, 7.2% [27 of 376]; placebo, 7.5% [29 of 388]). The most common adverse events in the EVO100 arm were vulvovaginal candidiasis (5.1% [19 of 376]), vaginal discharge (3.2% [12 of 376]), and urinary tract infection (3.2% [12 of 376]) and, in the placebo arm, bacterial vaginosis (4.6% [18 of 388]), urinary tract infection (2.6% [10 of 388]), and vaginal discharge (2.6% [10 of 388]). Few women discontinued owing to adverse events in either arm (EVO100, 1.1% [4 of 376]; placebo, 1.5% [6 of 388]). No treatment-related serious adverse events were reported. Most EVO100 users (88%) were satisfied or very satisfied with EVO100 after 16 weeks of use.

CONCLUSION

EVO100 significantly reduced the risk of chlamydia and gonorrhea infections in women at high risk of Chlamydia trachomatis and Neisseria gonorrhoeae infection and was well tolerated, with observed adverse events consistent with its known safety profile.

Coxiella burnetii-Infected NK Cells Release Infectious Bacteria by Degranulation

Natural killer (NK) cells are critically involved in the early immune response against various intracellular pathogens, including Coxiella burnetii and Chlamydia psittaci Chlamydia-infected NK cells functionally mature, induce cellular immunity, and protect themselves by killing the bacteria in secreted granules. Here, we report that infected NK cells do not allow intracellular multiday growth of Coxiella, as is usually observed in other host cell types. C. burnetii-infected NK cells display maturation and gamma interferon (IFN-γ) secretion, as well as the release of Coxiella-containing lytic granules. Thus, NK cells possess a potent program to restrain and expel different types of invading bacteria via degranulation. Strikingly, though, in contrast to Chlamydia, expulsed Coxiella organisms largely retain their infectivity and, hence, escape the cell-autonomous self-defense mechanism in NK cells.

HPTN 035 phase II/IIb randomised safety and effectiveness study of the vaginal microbicides BufferGel and 0.5% PRO 2000 for the prevention of sexually transmitted infections in women

OBJECTIVES

To estimate the effectiveness of candidate microbicides BufferGel and 0.5% PRO 2000 Gel (P) (PRO 2000) for prevention of non-ulcerative sexually transmitted infections (STIs).

METHODS

Between 2005 and 2007, 3099 women were enrolled in HIV Prevention Trials Network (HPTN) protocol 035, a phase II/IIb evaluation of the safety and effectiveness of BufferGel and PRO 2000 for prevention of STIs, including Neisseria gonorrhoeae (NG), Chlamydia trachomatis (CT) and Trichomonas vaginalis (TV). Incidences of STIs were determined by study arm, and HRs of BufferGel and PRO 2000 versus placebo gel or no gel control groups were computed using discrete time Andersen-Gill proportional hazards model.

RESULTS

The overall incidence rates were 1.6/100 person-years at risk (PYAR) for NG, 3.9/100 PYAR for CT and 15.3/100 PYAR for TV. For BufferGel versus placebo gel, HRs were 0.99 (95% CI 0.49 to 2.00), 1.00 (95% CI 0.64 to 1.57) and 0.95 (95% CI 0.71 to 1.25) for prevention of NG, CT and TV, respectively. For PRO 2000, HRs were 1.66 (95% CI 0.90 to 3.06), 1.16 (95% CI 0.76 to 1.79) and 1.18 (95% CI 0.90 to 1.53) for prevention of NG, CT and TV, respectively.

CONCLUSIONS

The incidence of STIs was high during HIV Prevention Trials Network 035 despite provision of free condoms and comprehensive risk-reduction counselling, highlighting the need for effective STI prevention programmes in this population. Unfortunately, candidate microbicides BufferGel and PRO2000 had no protective effect against gonorrhoea, chlamydia or trichomoniasis.

TRIAL REGISTRATION NUMBER

NCT00074425.

ACIDFORM: a review of the evidence

OBJECTIVE

ACIDFORM is a candidate microbicide with spermicidal properties. A large Phase 3 trial is underway, and it is anticipated that this product will be approved for contraceptive use and marketed soon in the United States. The goal of this article is to critically review the evidence supporting the properties, safety profile and different uses of ACIDFORM gel.

STUDY DESIGN

We searched PubMed and Medline for any published literature on ACIDFORM.

RESULTS

ACIDFORM is an acidifying agent that works by lowering the vaginal pH to enhance the normal vaginal defenses. In addition to strong acid-buffering properties, ACIDFORM has high bioadhesive and viscosity-retaining properties. Several Phase 1 clinical trials have demonstrated the vaginal safety of ACIDFORM used alone or in combination with a diaphragm, although dose-dependent side effects appear to be present. Studies investigating the efficacy of ACIDFORM against sexually transmitted infections (STIs) are promising, but further trials are needed.

CONCLUSIONS

The properties of ACIDFORM offer many advantages for use, either alone or in combination with another active ingredient, such as Tenofovir. Potential applications for ACIDFORM include use as a personal lubricant, a vaginal contraceptive (alone or with a barrier method) and a microbicidal product or as a formulation vehicle for an active ingredient.

IMPLICATIONS

ACIDFORM is a candidate female-controlled vaginal preparation with microbicidal and spermicidal properties. A dual protection method could prevent unwanted pregnancies and reduce the risk of STI acquisition.

A large, population-based study of age-related associations between vaginal pH and human papillomavirus infection

Background

Vaginal pH is related to genital tract inflammation and changes in the bacterial flora, both suggested cofactors for persistence of human papillomavirus (HPV) infection. To evaluate the relationship between vaginal pH and HPV, we analyzed data from our large population-based study in Guanacaste, Costa Rica. We examined vaginal pH and the risk of HPV infection, cytological abnormalities, and C. trachomatis infection.

Methods

Our study included 9,165 women aged 18-97 at enrollment with a total of 28,915 visits (mean length of follow-up = 3.4 years). Generalized estimating equations were used to evaluate the relationship between vaginal pH and HPV infection (both overall and single versus multiple types) and low-grade squamous intraepithelial lesions (LSIL), the cytomorphic manifestation of HPV infection. The relationship between enrollment vaginal pH and C. trachomatis infection was assessed by logistic regression. Results were stratified by age at visit.

Results

Detection of HPV was positively associated with vaginal pH, mainly in women < 35 years (p-trend = 0.009 and 0.007 for women aged < 25 and 25-34 years, respectively). Elevated vaginal pH was associated with 30% greater risk of infection with multiple HPV types and with LSIL, predominantly in women younger than 35 and 65+ years of age. Detection of C. trachomatis DNA was associated with increased vaginal pH in women < 25 years (OR 2.2 95% CI 1.0-5.0).

Conclusions

Our findings suggest a possible association of the cervical microenvironment as a modifier of HPV natural history in the development of cervical precancer and cancer. Future research should include studies of vaginal pH in a more complex assessment of hormonal changes and the cervicovaginal microbiome as they relate to the natural history of cervical neoplasia.

Phase I safety trial of two vaginal microbicide gels (Acidform or BufferGel) used with a diaphragm compared to KY jelly used with a diaphragm

OBJECTIVES

To assess the safety and acceptability of 2 vaginal microbicide gels (Acidform and BufferGel) used with a diaphragm compared to KY Jelly used with a diaphragm among low-risk, sexually abstinent women.

STUDY DESIGN

Eighty-one women enrolled in a randomized, masked, phase I safety study using a diaphragm with Acidform, BufferGel, or KY Jelly for 6 to 10 hours nightly for 14 nights. Physical examination, colposcopy, and lab studies were performed after 1 and 2 weeks of use. Diaries and questionnaires were used to assess user acceptability.

RESULTS

Sixty-nine participants (85%) completed the study. Safety and acceptability appeared similar among the 3 study groups and no serious adverse events related to the study products were reported. Adverse events were mild and anticipated.

CONCLUSIONS

Acidform and BufferGel compared to KY Jelly, when used with diaphragm daily for 14 days, appeared to be safe and acceptable in a small study of low-risk abstinent women.

Vaginal safety after use of a bioadhesive, acid-buffering, microbicidal contraceptive gel (ACIDFORM) and a 2% nonoxynol-9 product

BACKGROUND

ACIDFORM is a microbicidal and contraceptive candidate with strong buffering capacity.

METHODS

This was a Phase I blinded, randomized and crossover clinical study on two products, ACIDFORM and a commercial nonoxynol-9 (N-9) product (2%), evaluating their vaginal safety in 20 couples aged between 19 and 45 years. The women had regular menses, underwent previous tubal ligation, were not breast-feeding, had no vaginal sign and symptom and were in a stable partnership; both partners had no previous STI. Colposcopy, vaginal microbiology, inflammation markers and subject complaints were studied after coitus. Women were randomly assigned sequentially to receive ACIDFORM 0-30 min (0-30 min before intercourse), ACIDFORM 8-10 h (8-10 h before intercourse) or N-9 0-30 min after a control cycle.

RESULTS

Mild/moderate vulvar irritation was observed in five postcoital test colposcopies, burning and pruritus were reported in six treated cycles and non-irritation-related symptoms were found in five cycles with different treatments. No difference in vaginal pH, Nugent scores, H2O2-producing lactobacillus or leukocytes and interleukin 6 in the cervicovaginal lavage was found between the treatment and control cycles.

CONCLUSIONS

ACIDFORM appears to be safe for clinical use once a day. There is a potential spermicidal-microbicidal role for ACIDFORM as a vaginal flora helper or as a vehicle for products, except N-9.

Prioritizing prevention of HIV and sexually transmitted infections: first-generation vaginal microbicides

PURPOSE OF REVIEW

As the HIV/AIDS pandemic continues unabated, novel control measures for the spread of HIV and other sexually transmitted infections are urgently needed. Topical microbicides are designed to prevent transmission of sexually transmitted infections when applied vaginally. The microbicides discussed in this review may provide a new opportunity for decreasing the spread of HIV and other sexually transmitted infections.

RECENT FINDINGS

Epidemiological studies suggest a synergistic relationship between HIV and sexually transmitted infections, particularly between HIV and genital herpes infection. Compounds have been developed to block transmission of HIV-1 and herpes simplex virus, as well as Neisseria gonorrhoea and Chlamydia trachomatis. Several of these compounds have advanced to clinical trials as candidate microbicides. Candidate compounds fall into the following categories: detergents or surfactants that inactivate viral particles, anionic polymers that block attachment of virus to target cells, vaginal acid-buffering agents that maintain a protective vaginal pH, and antiretroviral drugs specific for HIV. Evaluation of the safety of topical microbicides remains problematic. Clinical experiences indicate that current models to assess safety in vitro and in vivo may be insufficient to assess the safety of vaginal microbicides. A critical direction of future studies is to identify which assay(s) provide surrogate laboratory markers of safety that correlate with clinical outcomes.

SUMMARY

The spread of HIV, and its increasing burden of disease in women, necessitates the development of novel prophylactic strategies. Topical microbicides offer women an empowering preventative option but require vigorous testing for safety and effectiveness.

Discovery of substituted isoxazolecarbaldehydes as potent spermicides, acrosin inhibitors and mild anti-fungal agents

BACKGROUND

The continued endeavour to design novel, non-detergent molecules that can be useful as topical, prophylactic contraceptives has led to the discovery of substituted isoxazolecarbaldehydes as a new class of compounds exhibiting both spermicidal and acrosin inhibitory activities simultaneously.

METHODS

Normal human semen samples were used to detect the spermicidal and acrosin inhibitory activities of the new compounds. Lactobacillus, HeLa and Candida cultures were used to determine the safety of compounds towards normal vaginal flora, their cytotoxicity and anti-fungal activity. Supravital staining and the hypo-osmotic swelling test (HOST) were used to detect the effect on sperm membrane integrity. Nonoxynol-9 (N-9) was used as a reference standard.

RESULTS

The 5- and 3-substituted isoxazolecarbaldehydes showed significant spermicidal [minimum effective concentration (MEC)=0.005-2.5%] and acrosin inhibitory (IC50=3.9-58 x 10(-4) mol/l) activities in several molecules along with weak fungicidal activity against Candida albicans. Lineweaver-Burk and Dixon plot analysis of a representative structure showed non-competitive inhibition of human acrosin enzyme, and the most potent acrosin inhibitors also considerably diminished the induction of the acrosome reaction by Ca2+ ionophore. Some compounds were found to be significantly safer than N-9 towards Lactobacillus acidophilus in vitro at their respective spermicidal MECs. In the cytotoxicity assay, the IC50 of these compounds towards the HeLa cell line was of the same order as N-9 (0.9-0.1 mmol/l); however, in contrast, the compounds exhibited only a moderate effect on sperm membrane integrity.

CONCLUSIONS

This study indicates that 5- and 3-substituted isoxazolecarbaldehydes are 'first generation' multifunctional, spermicidal molecules that hold promise for development as topical contraceptives with useful associated activities that can add considerably to their effectiveness, safety and prophylaxis.

Postcoital testing after the use of a bio-adhesive acid buffering gel (ACIDFORM) and a 2% nonoxynol-9 product

ACIDFORM is a gel already shown to be safe in vaginal use during six consecutive days through colposcopic observation. A randomized, blinded, crossover study was carried out to compare the spermicidal effect of ACIDFORM to that of a commercial 2% nonoxynol-9 (N-9) product. Twenty sexually active, sterilized women, aged 19-45 years, with regular cycles, normal gynecological exam, no previous sexually transmitted infection (STI) and stable partner willing to undergo four postcoital tests (PCTs) at midcycle during four different menstrual cycles, were enrolled in the study. Known allergy to N-9 or ACIDFORM, oligospermic partner, chronic diseases, use of hormones, previous treatment for STI or presence of STI at screening tests were criteria for exclusion. ACIDFORM or N-9 product administered 0-30 min precoitus or ACIDFORM given 8-10 h precoitus significantly reduced the mean number of progressively motile sperm compared to control cycles (0.19, 0.07, 0.75 vs. 17.94, respectively, p<.05, Wilcoxon test). All treated cycles had five or fewer progressively motile sperm in midcycle cervical mucus, confirming in vivo the spermicidal effect of ACIDFORM previously observed in vitro and in animal models.

Effect of spermicides on Lactobacillus acidophilus in vitro-nonoxynol-9 vs. Sapindus saponins

Saponins extracted from the fruit pericarp of Sapindus mukorosii were tested for their bactericidal/bacteriostatic property against Lactobacillus acidophilus. Nonoxynol-9 was used as a reference compound for the comparison of activity. Lactobacillus colonies were grown on specific medium (Rogosa SL agar) containing different concentrations of saponins and nonoxynol-9 in an atmosphere of 5% CO2/95% air at 37 degrees C for 72 h. The number and size of colonies were recorded at the end of the experiment and compared with controls. Results indicated that nearly 90% of Lactobacillus colonies with minor reduction in size thrived at 0.05% concentration of saponins whereas only 18% of colonies with approximately 75% reduction in size grew in dishes containing 0.05% nonoxynol-9. At higher concentrations of saponins, there was a gradual, dose-dependent reduction in the number and size of colonies and at 2.5% concentration there was an approximately 55% reduction in the number and 60% reduction in the size of surviving colonies. No lactobacillus colonies, however, grew in dishes containing 0.1% and higher concentrations of nonoxynol-9. The studies indicate that Sapindus saponins as compared to nonoxynol-9 are far less toxic to lactobacillus species and therefore saponins containing spermicidal preparations are likely to be more vaginal-friendly than equivalent nonoxynol-9 preparations.

Thermoreversible gel formulation containing sodium lauryl sulfate as a potential contraceptive device

The contraceptive properties of a gel formulation containing sodium lauryl sulfate were investigated in both in vitro and in vivo models. Results showed that sodium lauryl sulfate inhibited, in a concentration-dependent manner, the activity of sheep testicular hyaluronidase. Sodium lauryl sulfate also completely inhibited human sperm motility as evaluated by the 30-sec Sander-Cramer test. The acid-buffering capacity of gel formulations containing sodium lauryl sulfate increased with the molarity of the citrate buffers used for their preparations. Furthermore, experiments in which semen was mixed with undiluted gel formulations in different proportions confirmed their physiologically relevant buffering capacity. Intravaginal application of the gel formulation containing sodium lauryl sulfate to rabbits before their artificial insemination with freshly ejaculated semen completely prevented egg fertilization. The gel formulation containing sodium lauryl sulfate was fully compatible with nonlubricated latex condoms. Taken together, these results suggest that the gel formulation containing sodium lauryl sulfate could represent a potential candidate for use as a topical vaginal spermicidal formulation to provide fertility control in women.

Use of mandelic acid condensation polymer (SAMMA), a new antimicrobial contraceptive agent, for vaginal prophylaxis

OBJECTIVE

To assess the contraceptive properties, antimicrobial activity, and safety of mandelic acid condensation polymer (SAMMA).

DESIGN

Experimental study of SAMMA's in vitro and in vivo properties.

SETTING

Academic research laboratories.

PATIENT(S)

Healthy volunteers for semen donation in an academic research environment.

INTERVENTION(S)

Inhibition of sperm function indicators, conception, sexually transmitted infection-causing pathogens (including HIV), and lactobacilli was evaluated. Safety indicators were studied.

MAIN OUTCOME MEASURE(S)

Quantitation of SAMMA's effect on microbial infectivity or multiplication and on sperm function in vitro; evaluation of contraceptive efficacy in vivo; assessment of safety in vitro and in vivo.

RESULT(S)

Mandelic acid condensation polymer is not cytotoxic toward lactobacilli, microbial host cells, and spermatozoa. The compound inhibits hyaluronidase and acrosin, induces sperm acrosomal loss, and is contraceptive in the rabbit model. Mandelic acid condensation polymer prevents infectivity of HIV and herpesviruses 1 and 2 and, to a lesser extent, of Chlamydia trachomatis. It inhibits the multiplication of Neisseria gonorrhoeae. Mandelic acid condensation polymer is not mutagenic, has low acute oral toxicity, and is safe in the rabbit vaginal irritation assay.

CONCLUSION(S)

Mandelic acid condensation polymer inhibits sperm function, is contraceptive, has broad-spectrum antimicrobial activity, and is highly safe. Further development as a microbicide is warranted.

The innate and early immune response to pathogen challenge in the female genital tract and the pivotal role of epithelial cells

The female reproductive tract is immunologically unique in its requirement for tolerance to allogeneic sperm and, in the upper tract, to the conceptus. However, it must also be appropriately protected from, and respond to, a diverse array of sexually transmitted pathogens. Some of these infections can be lethal (e.g. Human Immunodeficiency Virus (HIV), Human Papilloma Virus (HPV)), and others (e.g. Chlamydia trachomatis and Neisseria gonorrhoeae) can have potentially devastating reproductive sequelae. Interactions between a host and a pathogen are complex, diverse and regulated, and are a function of the individual pathogen, and host immunity. Although there is undoubtedly commonality in the mucosal immune response, there is also evidence of a degree of site-specificity in immune mechanisms, dependent upon the function and anatomical location of an organ. In this article, we review the evidence on the pivotal role of epithelial cells in the innate and early immune response to pathogen challenge in female genital tract tissues, and examine the evidence that the 'sterile' upper and the 'non-sterile' lower female genital tract may maintain a different immunological surveillance milieu, and may also respond differentially to pathogen challenge. We also review the unique characteristics, and subsequent ramifications of the acute cervical immune response to C. trachomatis, and discuss how natural antimicrobial mediators of immunity may be utilized to decrease the spread of sexually transmitted infections.

Efficacy and safety of a new vaginal contraceptive antimicrobial formulation containing high molecular weight poly(sodium 4-styrenesulfonate)

Host cell infection by sexually transmitted disease (STD)-causing microbes and fertilization by spermatozoa may have some mechanisms in common. If so, certain noncytotoxic agents could inhibit the functional activity of both organisms. High molecular mass poly(sodium 4-styrenesulfonate) (T-PSS) may be one of these compounds. T-PSS alone (1 mg/ml) or in a gel (2% or 5% T-PSS) completely prevented conception in the rabbit. Contraception was not due to sperm cytotoxicity or to an effect on sperm migration. However, T-PSS inhibited sperm hyaluronidase (IC(50) = 5.3 microg/ml) and acrosin (IC(50) = 0.3 microg/ml) and caused the loss of acrosomes from spermatozoa (85% maximal loss by 0.5 microg/ml). T-PSS (5% in gel) also reduced sperm penetration into bovine cervical mucus (73% inhibition by 1 mg gel/ml). T-PSS (5% in gel) inhibited human immunodeficiency virus (HIV; IC(50)= 16 microg gel/ml) and herpes simplex viruses (HSV-1 and HSV-2; IC(50) = 1.3 and 1.0 microg gel/ml, respectively). The drug showed high efficacy against a number of clinical isolates and laboratory strains. T-PSS (5% in gel) also inhibited Neisseria gonorrhea (IC(50) < 1.0 gel/ml) and Chlamydia trachomatis (IC(50) = 1.2 microg gel/ml) but had no effect on lactobacilli. These results imply that T-PSS is an effective functional inhibitor of both spermatozoa and certain STD-causing microbes. The noncytotoxic nature should make T-PSS safe for vaginal use. T-PSS was nonmutagenic in vitro and possessed an acute oral toxicity of >5 g/kg (rat). Gel with 10% T-PSS did not irritate the skin or penile mucosa (rabbit) and caused no dermal sensitization (guinea pig). Vaginal administration of the 5% T-PSS gel to the rabbit for 14 consecutive days caused no systemic toxicity and only mild (acceptable) vaginal irritation. T-PSS in gel form is worthy of clinical evaluation as a vaginal contraceptive HIV/STD preventative.

An Update on Vaginal Microbicides

In response to an increasing prevalence of sexually transmitted diseases, especially AIDS, efforts to prevent further infections have been heightened. One of those approaches has been the development of topical microbicidal agents or microbicides. These are compounds designed to protect the body's mucosal surfaces from infection by sexually transmitted disease-causing pathogens. Numerous candidates are currently in preclinical stages; however, only a handful have been tested for safety, and even fewer are ready for clinical efficacy trials. In this update, we describe some of the specific features of microbicide research and development, including preclinical screening algorithms, candidate's ideal properties, examples of compounds presently in the pipeline, and future prospects.

Properties of a new acid-buffering bioadhesive vaginal formulation (ACIDFORM)

Vaginal prophylactic methodology may prevent heterosexual transmission of the HIV and other sexually transmitted disease-causing organisms as well as unplanned pregnancies. A new delivery system (ACIDFORM) was designed with acid-buffering, bioadhesive, and viscosity-retaining properties to (1) maintain the acidic vaginal milieu (the low pH inactivates many pathogens and spermatozoa), (2) form a protective layer over the vaginal/cervical epithelium (minimizing contact with pathogenic organisms), and (3) provide long-term vaginal retention. A Phase I clinical study with ACIDFORM provided initial information about its safety and showed the formation of a layer over the vaginal/cervical epithelium [1; Amaral et al., Contraception 1999;60:361-6]. To study the properties of the gel (without active ingredient) in more detail, ACIDFORM's acid-buffering, bioadhesive, viscosity-retaining, and spermicidal properties were compared in vitro to marketed formulations, and its long-term stability was assessed. ACIDFORM, either when titrated with NaOH or when mixed directly with semen, is highly acid buffering and much more effective than Aci-Jel, a commercial acid-buffering vaginal product. ACIDFORM adheres well to two model membranes (excised sheep vagina and cellophane) and is more bioadhesive than Conceptrol, Advantage S, Replens, Aci-Jel, and K-Y jelly. On dilution, ACIDFORM also retains its viscosity better than these marketed products. ACIDFORM is spermicidal and is stable for at least 2 years. These results suggest that ACIDFORM has advantages over presently marketed vaginal delivery systems. The gel may either be useful by itself as an antimicrobial contraceptive product or as a formulation vehicle for an active ingredient with antimicrobial and/or contraceptive properties.

Study of the vaginal tolerance to Acidform, an acid-buffering, bioadhesive gel

Vaginal tolerance tests were performed with a new potential microbicidal and spermicidal product, an acid-buffering vaginal gel (Acidform) without or with nonoxynol-9 (N-9). The potential advantages over other vaginal products include keeping a low pH, decrease of the irritating effect of N-9 on the cervix or vaginal mucosa associated with greater retention of the product after application, and decreasing "messiness" as compared to other vaginal products. Three groups of six women were admitted and randomly assigned to use Acidform with 0%, 2.5%, and 5% N-9. Colposcopic evaluation for vulvar, vaginal, and cervical signs of irritation was performed and photographs were taken, following a specific World Health Organization protocol, at time 0, and after 24 h and 6 days of application of the gel. No irritation or symptom was reported by users of Acidform without N-9. A generalized and intense erythema in cervix was observed in 10 of 12 Acidform/N-9 users and abrasion occurred in nine of them. Vulvar irritation was seen in seven of these 10 volunteers. N-9 concentration in the gel (2.5% or 5.0%) was not related to the findings. No ulcer, exulceration, or de-epithelialization was observed. Acidform without N-9 was well tolerated by volunteers, but it was unable to protect the cervix, vagina, and vulva from the N-9 effects.

Effects of pH and salinity on the antimicrobial properties of clavanins

Clavanins are histidine-rich, amidated alpha-helical antimicrobial peptides that were originally isolated from the leukocytes (hemocytes) of a tunicate, Styela clava. The activities of clavanin A amide and clavanin A acid against Escherichia coli, Listeria monocytogenes, and Candida albicans were substantially greater at pH 5.5 than at pH 7.4. In contrast, clavanin AK, a synthetic variant of clavanin A acid containing 4 histidine-->lysine substitutions exerted substantial activity at both pH 7.4 and pH 5.5. Each of these three clavanins permeabilized the outer and inner membranes of E. coli very effectively at pH 5.5, but only clavanin AK did so at pH 7.4. Unlike magainin 1 and cecropin P1, alpha-helical antimicrobial peptides from frog skin and porcine intestine, respectively, clavanins were broadly effective against gram-positive bacteria, including methicillin-resistant Staphylococcus aureus, as well as gram-negative organisms. Because clavanins exert substantial antimicrobial activity in 0.1 to 0.3 M NaCl, they provide templates for designing broad-spectrum peptide antibiotics intended to function in extracellular environments containing normal or elevated NaCl concentrations. The pH-dependent properties of histidine-rich antimicrobial peptides may allow the design of agents that would function selectively in acidic compartments, such as the gastric lumen, or within phagolysosomes.