Tenofovir vaginal film as a potential MPT product against HIV-1 and HSV-2 acquisition: formulation development and preclinical assessment in non-human primates.

Tenofovir (TFV) is an adenosine nucleotide analog with activity against HIV and HSV-2. Secondary analyses of clinical trials evaluating TFV gel as pre-exposure prophylaxis (PrEP) for HIV have shown that gel formulations of TFV provide significant protection against both HIV and HSV-2 acquisition in women who had evidence of use. An alternate quick-dissolving polymeric thin film, to deliver TFV (20 and 40 mg) has been developed as a potential multipurpose technology (MPT) platform. Film formulation was developed based on excipient compatibility, stability, and ability to incorporate TFV doses. Placebo, low dose (20 mg), and high dose (40 mg) films were utilized in these studies. The developed film platform efficiently incorporated the high dose of TFV (40 mg/film), released more than 50% of drug in 15 min with no in vitro toxicity. Pharmacological activity was confirmed in an ex vivo HIV-1 challenge study, which showed a reduction in HIV-1 infection with TFV films. Films were stable at both doses for at least 2 years. These films were found to be safe in macaques with repeated exposure for 2 weeks as evidenced by minimal perturbation to tissues, microbiome, neutrophil influx, and pH. Macaque sized TFV film (11.2 mg) evaluated in a pigtail macaque model showed higher vaginal tissue concentrations of TFV and active TFV diphosphate compared to a 15 mg TFV loaded gel. These studies confirm that TFV films are stable, safe and efficiently deliver the drug in cervicovaginal compartments supporting their further clinical development.

Intracellular Islatravir-Triphosphate in Dried Blood Spots and Peripheral Blood Mononuclear Cells from Pig-Tailed Macaques.

The purpose of this study was to evaluate the relationship between intracellular islatravir-triphosphate (ISL-TP) in paired peripheral blood mononuclear cells (PBMCs) and dried blood spots (DBS). Three pig-tailed macaques (PMs) were dosed with a single intravaginal extended-release ISL-etonogestrel film for a period of 31 days. After extraction and quantification, repeated measures correlation (rrm) was assessed between log-transformed DBS and PBMC ISL-TP concentrations. Twenty-six paired PBMC/DBS samples were included. Peak ISL-TP concentrations in DBS ranged from 262 to 913 fmol/punches, PBMC Cmax ranged from 427 to 857 fmol/106 cells. Repeated measures correlation yielded an rrm value of 0.96 (95% confidence interval 0.92-0.98; p < .0001). Importantly, ISL-TP was quantifiable in DBS and its pharmacokinetics were similar to PBMC in PMs. Human studies should evaluate DBS applications in clinical pharmacokinetic studies to help define ISL's place in the antiretroviral drug armamentarium.

Development and Evaluation of Nanoparticles-in-Film Technology to Achieve Extended In Vivo Exposure of MK-2048 for HIV Prevention.

MK-2048 is a second-generation integrase inhibitor active against HIV, which has been applied vaginally using ring formulations. In this work, a nanoparticle-in-film technology was developed as a discrete pre-exposure prophylactic product option against HIV for an extended duration of use. A film platform loaded with poly (lactic-co-glycolic acid) nanoparticles (PNP) encapsulating MK-2048 was engineered. MK-2048 PNPs were loaded into films that were manufactured via the solvent casting method. Physicochemical and mechanical properties, in vitro efficacy, Lactobacillus compatibility, in vitro and ex vivo permeability, and in vivo pharmacokinetics in macaques were evaluated. PNPs with a mean diameter of 382.2 nm and −15.2 mV zeta potential were obtained with 95.2% drug encapsulation efficiency. PNP films showed comparable in vitro efficacy to free MK-2048 (IC50 0.46 vs. 0.54 nM) and were found to have no impact on Lactobacillus. MK-2048 encapsulated in PNPs showed an increase in permeability (>4-fold) compared to the free MK-2048 in MDCKII cell lines. Furthermore, PNPs had higher ectocervical tissue permeability (1.7-fold) compared to free MK-2048. PNP films showed sustained drug levels for at least 3 weeks in the macaque vaginal fluid. This work demonstrates the synergy of integrating nanomedicine and polymeric film technology to achieve sustained vaginal drug delivery.

Rational Design of a Multipurpose Bioadhesive Vaginal Film for Co-Delivery of Dapivirine and Levonorgestrel.

Human immunodeficiency virus (HIV) infection and unintended pregnancy, which can lead to life-threatening complications, are two major burdens for female reproductive health. To address these pressing health issues, multipurpose prevention technologies (MPTs) are proposed to deliver two or more drugs simultaneously. MPTs could offer several benefits for users such as improved convenience, increased effectiveness, reduced cost, and decreased environmental burden. Here, we report the development, and in vitro and in vivo assessment of a bioadhesive vaginal film as a coitally-independent MPT dosage form for delivering dapivirine (DPV) and levonorgestrel (LNG) to prevent HIV infection and unintended pregnancy, respectively. After confirming the feasibility of bioadhesive film use for weekly drug delivery in vivo through colpophotography and MRI evaluation, the pharmacokinetics (PK) of DPV/LNG single entity and combination bioadhesive films was investigated in pigtailed macaques (n = 5). Both drugs from single entity or combination films were able to provide sustained drug release in vivo. The combination film showed lower local tissue clearance for DPV and exhibited significantly increased plasma concentration for LNG as compared to the single entity film. This proof-of-concept study demonstrates the ability of this novel bioadhesive film platform to deliver LNG and DPV simultaneously as an MPT product for the prevention of HIV infection and unintended pregnancy.

Evaluation of the Pig-Tailed Macaque (Macaca nemestrina) as a Model of Human Staphylococcus aureus Nasal Carriage.

Staphylococcus aureus nasal carriage is a common condition affecting both healthy and immunocompromised populations and provides a reservoir for dissemination of potentially infectious strains by casual contact. The factors regulating the onset and duration of nasal S. aureus colonization are mostly unknown, and a human-relevant animal model is needed. Here, we screened 17 pig-tailed macaques (Macaca nemestrina) for S. aureus carriage, and 14 of 17 animals tested positive in the nose at one or both screening sessions (8 weeks apart), while the other 3 animals were negative in the nose but positive in the pharynx at least once. As in humans, S. aureus colonization was densest in the nose, and treatment of the nostrils with mupirocin ointment effectively cleared the nostrils and 6 extranasal body sites. Experimental nasal S. aureus colonization was established with 104 CFU/nostril, and both autologous and nonautologous strains survived over 40 days without any apparent adverse effects. A human nasal S. aureus isolate (strain D579, sequence type 398) was carried in 4 of 6 animals for over 3 weeks. Nostrils that did eradicate experimentally applied S. aureus exhibited neutrophilic innate immunity marked by elevated nasal interleukin-1ß (IL-1ß), IL-8, and monocyte chemotactic protein 1 levels and a 10-fold decreased IL-1 receptor antagonist/IL-1ß ratio within 7 days postinoculation, analogous to the human condition. Taken together, pig-tailed macaques represent a physiological model of human S. aureus nasal carriage that may be utilized for testing natural colonization and decolonization mechanisms as well as novel classes of anti-S. aureus therapeutics.

The Chlamydia trachomatis Plasmid and CT135 Virulence Factors Are Not Essential for Genital Tract Infection or Pathology in Female Pig-Tailed Macaques.

The Chlamydia trachomatis plasmid and inclusion membrane protein CT135 are virulence factors in the pathogenesis of murine female genital tract infection. To determine if these virulence factors play a similar role in female nonhuman primates, we infected pig-tailed macaques with the same C. trachomatis strains shown to be important in the murine model. Wild-type C. trachomatis and its isogenic mutant strain deficient in both plasmid and CT135 were used to infect macaques. Macaques were given primary and repeated cervicovaginal challenges with the wild-type and mutant strains. The infection rate, infection duration, and antibody response were similar among macaques infected with both strains. Unexpectedly, colposcopy, laparoscopy, and histologic analysis revealed no substantial genital tract pathology following either primary or repeated cervicovaginal challenges. Cytokine analysis of cervicovaginal secretions from both challenged groups revealed low concentrations of interleukin 1ß (IL-1ß) and elevated levels of the interleukin 1 receptor agonist (IL-1RA). We propose that an imbalance of IL-1ß and IL-1RA in macaques is the reason for the mild inflammatory responses observed in infected urogenital tissues. Thus, understanding the pathobiology of chlamydial infection requires a better understanding of host epigenetic and chlamydial genetic factors. Our findings also have implications for understanding the high frequency of asymptomatic infections in humans.

Persistence, immune response, and antigenic variation of Mycoplasma genitalium in an experimentally infected pig-tailed macaque (Macaca nemestrina).

Mycoplasma genitalium is a sexually transmitted pathogen associated with several acute and chronic reproductive tract disease syndromes in men and women. To evaluate the suitability of a pig-tailed macaque model of M. genitalium infection, we inoculated a pilot animal with M. genitalium strain G37 in the uterine cervix and in salpingeal pockets generated by transplanting autologous Fallopian tube tissue subcutaneously. Viable organisms were recovered throughout the 8-week experiment in cervicovaginal specimens and up to 2 weeks postinfection in salpingeal pockets. Humoral and cervicovaginal antibodies reacting to MgpB were induced postinoculation and persisted throughout the infection. The immunodominance of the MgpB adhesin and the accumulation of mgpB sequence diversity previously observed in persistent human infections prompted us to evaluate sequence variation in this animal model. We found that after 8 weeks of infection, sequences within mgpB variable region B were replaced by novel sequences generated by reciprocal recombination with an archived variant sequence located elsewhere on the chromosome. In contrast, mgpB region B of the same inoculum propagated for 8 weeks in vitro remained unchanged. Notably, serum IgG reacted strongly with a recombinant protein spanning MgpB region B of the inoculum, while reactivity to a recombinant protein representing the week 8 variant was reduced, suggesting that antibodies were involved in the clearance of bacteria expressing the original infecting sequence. Together these results suggest that the pig-tailed macaque is a suitable model to study M. genitalium pathogenesis, antibody-mediated selection of antigenic variants in vivo, and immune escape.

Incorporation of the HIV-1 microbicide cyanovirin-N in a food product.

An urgent need exists for HIV-1 microbicides. Here, we describe the in vivo testing of lactic acid bacteria bioengineered to secrete cyanovirin-N. We fed pigtail macaques a yogurt formulation that used bioengineered strains as a starter culture. Cyanovirin-N expression could be detected in the rectal vault during and immediately after feeding. Ex vivo viral challenge of rectal tissue biopsies revealed that peak viral burden was significantly lower in tissue obtained from experimental animals compared with control animals. Formulation of candidate compounds in lactic acid bacteria and their oral administration seems to be a feasible strategy for mucosal delivery of microbicides.

Pigtailed macaque model refinement: topical microbicide safety in the presence of coitus.

BACKGROUND: Inclusion of sexual activity in the macaque model for topical microbicide safety evaluation would more closely mimic human use of topical microbicides and provide a more rigorous safety assessment. METHODS: Initially, male-female partners were monitored in cohousing arrangements to determine whether macaques would copulate ad libitum. The logistics of performing vaginal examinations before and after coital visits were analyzed and optimized. Findings from cervicovaginal examinations conducted before and after sexual activity were compared. RESULTS: Coital activity was reliably observed in the majority of cohousing sessions, representing all phases of the menstrual cycle. Female macaques were trained to be restrained while fully alert for pre-coital vaginal sampling. Post-coital examinations occur under general sedation. Post-coital examinations reveal alterations to tissues, microbiology, and pH compared with pre-coital visits. CONCLUSIONS: This work clearly demonstrates that it is feasible to incorporate sexual activity in the macaque model for topical microbicide safety assessment.

The formulated microbicide RC-101 was safe and antivirally active following intravaginal application in pigtailed macaques.

BACKGROUND: RC-101 is a congener of the antiretroviral peptide retrocyclin, which we and others have reported is active against clinical HIV-1 isolates from all major clades, does not hemagglutinate, and is non-toxic and non-inflammatory in cervicovaginal cell culture. Herein, film-formulated RC-101 was assessed for its antiviral activity in vitro, safety in vivo, retention in the cervix and vagina, and ability to remain active against HIV-1 and SHIV after intravaginal application in macaques. METHODOLOGY/PRINCIPAL FINDINGS: RC-101 was formulated as a quick-dissolving film (2000 µg/film), retained complete activity in vitro as compared to unformulated peptide, and was applied intravaginally in six pigtailed macaques daily for four days. At one and four days following the final application, the presence of RC-101 was assessed in peripheral blood, cervicovaginal lavage, cytobrushed cervicovaginal cells, and biopsied cervical and vaginal tissues by quantitative western blots. One day following the last film application, cervical biopsies from RC-101-exposed and placebo-controlled macaques were collected and were subjected to challenge with RT-SHIV in an ex vivo organ culture model. RC-101 peptide was detected primarily in the cytobrush and biopsied cervical and vaginal tissues, with little to no peptide detected in lavage samples, suggesting that the peptide was associated with the cervicovaginal epithelia. RC-101 remained in the tissues and cytobrush samples up to four days post-application, yet was not detected in any sera or plasma samples. RC-101, extracted from cytobrushes obtained one day post-application, remained active against HIV-1 BaL. Importantly, cervical biopsies from RC-101-treated animals reduced RT-SHIV replication in ex vivo organ culture as compared to placebo-treated animals. CONCLUSIONS/SIGNIFICANCE: Formulated RC-101 was stable in vivo and was retained in the mucosa. The presence of antivirally active RC-101 after five days in vivo suggests that RC-101 would be an important molecule to develop further as a topical microbicide to prevent HIV-1 transmission.

A summary of preclinical topical microbicide rectal safety and efficacy evaluations in a pigtailed macaque model.

BACKGROUND: There is widespread recognition of the potential promise of vaginal microbicides as a tool to combat global human immunodeficiency virus/acquired immunodeficiency syndrome and sexually transmitted infections epidemics, and candidate product development has maintained a rapid pace in recent years; however, rectal microbicide development has received less attention. As it is likely that commercial products developed for vaginal use will also be used rectally, there is a clear need to assess the safety and efficacy of candidate microbicide products specifically in the rectal compartment. METHODS: We have developed a standardized protocol for preclinical rectal safety and (chlamydial) efficacy assessment of topical microbicide candidates in a nonhuman primate model. We evaluated a total of 12 test compounds for rectal safety (via rectal pH, microflora, and rectal lavage) and 1 compound for efficacy against rectal chlamydial infection. RESULTS: In this article, we describe our methods in detail and summarize our results, particularly noting the ability of our model to distinguish products with deleterious effects on the rectal environment. We also outline the specific criteria used to recommend products move into preclinical rectal efficacy trials or be recommended for reformulation to the product developer. In summary, we observed significant adverse effects in 2 products. The single product that underwent efficacy evaluation was not observed to be protective against rectal chlamydial infection. CONCLUSIONS: A preclinical safety and efficacy model is critical to promoting rectal microbicide development, which will ultimately offer a significant opportunity for intervention in the global HIV/AIDS epidemic.

A summary of preclinical topical microbicide vaginal safety and chlamydial efficacy evaluations in a pigtailed macaque model.

BACKGROUND: The development of topical microbicides represents a new and exciting field in the prevention of sexually transmitted diseases, and it is especially important that candidate products undergo rigorous preclinical safety and efficacy testing before advancing to clinical trials. METHODS: We have developed a standardized protocol for preclinical vaginal safety and efficacy assessment of topical microbicide candidates in a nonhuman primate model. Over 7 years of funding under an NIH contract, we evaluated a total of 28 test compounds for vaginal safety (via colposcopy, vaginal pH, and microflora) and 9 compounds for efficacy against cervical chlamydial infection. In this article, we describe our methods in detail and summarize our results, particularly noting the ability of our model to distinguish products with deleterious effects on the cervicovaginal environment. We also outline the specific criteria used to determine which products should move into efficacy trials and which should be recommended for reformulation to the manufacturer. RESULTS: Overall, we noted acceptable safety profiles for 24 of 28 candidate products. Common findings included a transient decrease in vaginal pH, petechiae, and mild erythema. Four products were associated with significant adverse colposcopic findings including blisters, epithelial abrasions, and friability; all 4 products were successfully reformulated and showed acceptable safety profiles at lower concentrations. No products showed complete protection against cervical chlamydial infection. CONCLUSIONS: The macaque preclinical safety and efficacy model is critical to maintaining the pace of topical microbicide development, which could ultimately offer a significant opportunity for intervention in the global HIV/AIDS epidemic.

Application of optical coherence tomography for monitoring changes in cervicovaginal epithelial morphology in macaques: potential for assessment of microbicide safety.

OBJECTIVES: Safety is a primary concern in the development of topical microbicides. Optical coherence tomography (OCT), a high-resolution, in-depth cross-sectional imaging modality, was utilized in conjunction with colposcopy to assess induced cervicovaginal epithelial changes that may predict product safety. STUDY DESIGN: OCT and colposcopic images of macaque vaginal and cervical tissues were obtained in excised tissue and in vivo under various conditions, including mechanical injury and nonoxynol-9 treatment. RESULTS: A scoring system was developed to categorize and quantify the OCT images based on morphologic features that indicate the presence or absence of an intact epithelial layer and inflammation. Using 3 categories (normal, mild to moderately abnormal, and severely abnormal), differences between healthy and injured tissue were apparent on OCT images. Normal images (category 1) had a bilayered structure representative of the epithelium and submucosa. Mild to moderately abnormal images (category 2) had areas of normal and abnormal epithelium. Severely abnormal images (category 3) had complete loss of the epithelium and/or inflammation, with loss of the bilayered structure on OCT. CONCLUSIONS: OCT is a noninvasive imaging modality complementary to colposcopy. It distinguished between normal and abnormal (or injured) tissue and thus holds promise for safety evaluations of candidate microbicides and other vaginal products.

Development of a nonhuman primate model for Trichomonas vaginalis infection.

OBJECTIVE: Trichomoniasis, caused by Trichomonas vaginalis, is a prevalent sexually transmitted infection associated with increased risk of HIV infection. An animal model of T. vaginalis infection would enable scientists to further investigate trichomoniasis. STUDY DESIGN: Seven macaques (4 test vs. 3 control) were enrolled in a 2-week pilot study. Eight additional animals participated in a 2-arm (T. vaginalis vs. sham inoculated) crossover study lasting 5 weeks before treatment. In all, 12 Macaca nemestrina monkeys were challenged with a single intravaginal inoculation of 6.6 to 7.1 x 10(5) trichomonads (ATCC 50148). Vaginal culture (InPouch TV), colposcopy, microbiology, pH, and cervical cytokines were assessed at baseline, day 2, and weekly thereafter. RESULTS: Ten of 12 challenged animals tested positive for trichomoniasis for 2 weeks or longer. One animal tested positive on days 2 and 7 but negative thereafter. Only one animal was not infected. Oral metronidazole treatment (35 mg/kg per day for 3 days) resolved infection in all animals. Trichomoniasis infection did not lead to shifts in vaginal microbiology or pH. CONCLUSIONS: A single T. vaginalis inoculation results in persistent infection in the pigtailed macaque.

Vaginal and rectal topical microbicide development: safety and efficacy of 1.0% Savvy (C31G) in the pigtailed macaque.

BACKGROUND: A 1.0% gel formulation of C31G, a surfactant, has been shown to have in vitro antiviral and antibacterial activity. GOAL: The goal of this study was to evaluate the safety and efficacy of vaginal and rectal applications of 1.0% Savvy (C31G) in the nonhuman primate model. STUDY DESIGN: The safety of repeated 1.0% C31G application was evaluated by microflora, pH, vaginal biopsy, colposcopy, and rectal lavage. Efficacy in preventing chlamydial infection was documented by culture, nucleic acid amplification tests, and serology. RESULTS: Repeated applications of Savvy (1.0% C31G) were not associated with significant changes in pH, microflora, or inflammatory infiltrates on tissues. No significant differences in epithelial desquamation were noted after rectal product use compared with placebo. Four of 6 animals were protected from chlamydial infection after pretreatment with Savvy. C31G was shown to be safe to both vaginal and rectal mucosal tissues and to the microflora with repeated daily use. CONCLUSION: Savvy has an acceptable safety profile after repeated vaginal and rectal use. A single intravaginal application of 1.0% C31G provided partial protection from acquiring cervical chlamydial infection.

Significant reduction in inflammatory response in the macaque model of chlamydial pelvic inflammatory disease with azithromycin treatment.

We inoculated 45 female macaques in the cervix with Chlamydia trachomatis once weekly for 5 weeks and randomly assigned them to treatment with doxycycline (n=12), azithromycin (n=12), or placebo (n=21). At hysterectomy, cervical cultures remained positive in 12 of 21 placebo-treated monkeys, versus 0 of 12 doxycycline- or azithromycin-treated monkeys (P<.01); cervical ligase chain reaction remained positive in 15 placebo-, 1 doxycycline-, and 0 azithromycin-treated monkeys. Tubal swabs remained positive in 3 placebo-, 1 doxycycline-, and 0 azithromycin-treated monkeys. Immunopathologic damage was moderate to widespread in upper and lower reproductive-tract tissues from placebo- and doxycycline-treated monkeys but were significantly reduced in azithromycin-treated monkeys. Transforming growth factor- beta was also significantly less prevalent in azithromycin-treated monkeys. Azithromycin treatment dramatically reduced the inflammatory response and was highly effective in eradicating C. trachomatis from the lower and upper reproductive tract (12/12), compared with doxycycline (7/12) and placebo (3/21).

Macaca fascicularis vs. Macaca nemestrina as a model for topical microbicide safety studies.

Preclinical studies of topical microbicide products, using appropriate animal models for assessing the safety of repeated use are essential. The pig-tailed macaque (Macaca nemestrina) model has been used to assess the safety of vaginally and rectally applied topical microbicide products. The availability of sexually mature female pig-tailed macaques has become extremely restricted. Currently, M. fascicularis is more readily available, and was therefore evaluated as an alternative model for topical microbicide pre-clinical evaluation. Twenty sexually mature M. fascicularis were assessed for feasibility to mimic the established models. The rectal and cervicovaginal microenvironments of the M. fascicularis were determined to be similar to those of M. nemestrina and humans. The gross anatomy was significantly smaller than that of the pig-tailed macaque, such that colposcopic examinations and multiple biopsies would not be possible. Thus, the M. fascicularis may not be useful for vaginally applied topical microbicide safety studies yet adequate for assessing safety of rectally applied topical microbicide products.

Heat shock protein 60 is the major antigen which stimulates delayed-type hypersensitivity reaction in the macaque model of Chlamydia trachomatis salpingitis.

Chlamydial delayed-type hypersensitivity antigens were analyzed by using the subcutaneous salpingeal autotransplant model of Macaca nemestrina infected with Chlamydia trachomatis serovar E. Heat shock protein 60 was the only antigen shown to induce delayed-type hypersensitivity among other antigens tested, including UV-inactivated organisms, recombinant major outer membrane protein, purified outer membrane proteins, and heat shock protein 10.

Lactobacillus crispatus capsules: single-use safety study in the Macaca nemestrina model.

BACKGROUND: Lactobacillus crispatus is a part of the normal vaginal microflora of humans. GOAL: The goal of this study was to assess whether a capsule containing an H2O2-producing strain of L crispatus (CTV-05) would alter the vaginal microflora and/or epithelial tissues when applied intravaginally in the pig-tailed macaque model. STUDY DESIGN: Ten sexually mature female Macaca nemestrina were assessed at baseline for quantitative vaginal microbiology and vaginal pH and with colposcopy. One capsule containing 108 colony forming units of desiccated L crispatus CTV-05 was inserted into the vaginal fornix of each animal. Vaginal assessments were repeated on days 1 and 2 after capsule insertion. The L crispatus CTV-05 strain was identified with use of a DNA fingerprinting method. RESULTS: Before product use, four of 10 animals had detectable levels of H2O2-producing lactobacilli. L crispatus CTV-05 was detected in 1 of 10 animals on day 1 and in 3 of 10 animals on day 2 following insertion of the capsule. There were no tissue changes observed by colposcopy. Vaginal pH decreased in two animals colonized by CTV-05, from 7.0 at baseline to 4.5+/-0.5 on days 1 and 2 after product use. CONCLUSIONS: A single intravaginal application of capsules containing 108 L crispatus CTV-05 resulted in vaginal colonization in three of 10 animals 2 days after use. The absence of colposcopic changes in the vagina/cervical tissues indicates that L crispatus capsules are well tolerated.

Rectal applications of nonoxynol-9 cause tissue disruption in a monkey model.

BACKGROUND: Efforts to develop topical microbicide products have all but ignored evaluation for rectal use. GOAL: The goal of this study was to assess the effects of multiple rectal applications of Conceptrol (containing 4% nonoxynol-9) on flora and mucosal tissues in the pig-tailed macaque model. STUDY DESIGN: Monkeys (8 per group) received daily rectal applications of Conceptrol, placebo gel, or no product, for 3 days. At each visit, a preapplication rectal lavage specimen and swab specimen for microbiology and pH determination were collected. Conceptrol or placebo gel (2.5 ml) was then administered intrarectally. Fifteen minutes after application, samples were again collected. RESULTS: Gross observation of rectal lavage indicated sheets of epithelium 15 minutes after application of the nonoxynol-9 product. Histopathology of these samples revealed epithelial sheets with stroma attached. The presence of H(2)O(2)-producing lactobacilli remained relatively constant, whereas that of H(2)O(2)-producing viridans streptococci diminished in all nonoxynol-9-exposed animals in which these organisms were detected at baseline. CONCLUSIONS: Repeated applications of nonoxynol-9 disrupts the rectal mucosa of the pig-tailed macaque. The disruption of these tissues could have serious implications for an increase in likelihood of acquisition of sexually transmitted infection/HIV in humans.