The pig-tailed macaque rectal model: microflora and chlamydial infection

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-1β (IL-1β), IL-8, and monocyte chemotactic protein 1 levels and a 10-fold decreased IL-1 receptor antagonist/IL-1β 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.

Development of a rectal sexually transmitted infection (STI) Model in Rhesus macaques using Chlamydia trachomatis serovars E and L2

BACKGROUND

Rectal STI coinfection models enhance the understanding of rectal HIV transmission risk factors.

MATERIALS AND METHODS

Rhesus macaques (n=9) were exposed to one of three rectal Chlamydia trachomatis (CT) challenges: C. trachomatis L₂ (CT-L₂ ); C. trachomatis serovar E (CT-E), followed by CT-L₂ ; or CT-E, treatment/clearance, then CT-L₂ . Infections were monitored by PCR. Weekly blood and rectal secretion/lavage samples were collected for cytokine analyzes and/or epithelial sloughing, occult, and overt blood determinations.

RESULTS

Chlamydial infections were successfully established in each animal, with varying degrees of persistence. Mucosal IL-1beta was upregulated in animals consecutively infected with CT-E then CT-L₂ (P=.05). Epithelial sloughing was also significantly increased post-infection in this group (P=.0003).

CONCLUSIONS

This study demonstrates successful rectal infection of rhesus macaques with CT-E and CT-L₂ and describes measures of assessing rectal inflammation and pathology. Different infection strategies yield varying inflammatory and pathologic outcomes, providing well-described models for future SIV/SHIV susceptibility studies.

Chlamydia caviae infection alters abundance but not composition of the guinea pig vaginal microbiota

In humans, the vaginal microbiota is thought to be the first line of defense again pathogens including Chlamydia trachomatis. The guinea pig has been extensively used as a model to study chlamydial infection because it shares anatomical and physiological similarities with humans, such as a squamous vaginal epithelium as well as some of the long-term outcomes caused by chlamydial infection. In this study, we aimed to evaluate the guinea pig-C. caviae model of genital infection as a surrogate for studying the role of the vaginal microbiota in the early steps of C. trachomatis infection in humans. We used culture-independent molecular methods to characterize the relative and absolute abundance of bacterial phylotypes in the guinea pig vaginal microbiota in animals non-infected, mock-infected or infected by C. caviae. We showed that the guinea pig and human vaginal microbiotas are of different bacterial composition and abundance. Chlamydia caviae infection had a profound effect on the absolute abundance of bacterial phylotypes but not on the composition of the guinea pig vaginal microbiota. Our findings compromise the validity of the guinea pig-C. caviae model to study the role of the vaginal microbiota during the early steps of sexually transmitted infection.

The vaginal microbiota of the guinea pig differs from that of humans and cannot prevent chlamydial infections efficiently.

Nonhuman primate models for cell-associated simian immunodeficiency virus transmission: the need to better understand the complexity of HIV mucosal transmission

Nonhuman primates are extensively used to assess strategies to prevent infection from sexual exposure to human immunodeficiency virus (HIV) and to study mechanisms of mucosal transmission. However, although semen represents one of the most important vehicles for the virus, the vast majority of preclinical challenge studies have used cell-free simian immunodeficiency virus (SIV) or simian/human immunodeficiency virus (SHIV) viral particles inoculated as diluted culture supernatants. Semen is a complex body fluid containing many factors that may facilitate or decrease HIV infectiousness. The virus in semen is present in different forms: as free virus particles or as cell-associated virus (ie, within infected leukocytes). Although cell-to-cell transmission of HIV is highly efficient, the role of cell-associated virus in semen has been surprisingly poorly investigated in nonhuman primate models. Mucosal exposure of macaques to cell-associated SIV by using infected peripheral blood mononuclear cells or spleen cells has been shown to be an efficient means of infection; however, it has yet to be shown that SIV- or SHIV-infected seminal leukocytes can transmit infection in vivo. Improvement of animal models to better recapitulate the complex microenvironment at portals of HIV entry is needed for testing candidate antiretrovirals, microbicides, and vaccines.

Development of a rectal sexually transmitted infection--HIV coinfection model utilizing Chlamydia trachomatis and SHIVSF162p3

BACKGROUND

Rectal sexually transmitted infections (STIs) may increase HIV susceptibility in men who have sex with men (MSM), and Chlamydia trachomatis is prevalent among HIV-positive MSM. To study STIs and HIV infection in MSM, we first evaluated whether cynomolgus macaques can sustain both C. trachomatis and SHIVSF162p3 infections.

METHODS

Four SHIVSF162p3 -positive male cynomolgus macaques were used (n = 3 rectally inoculated with 10(6) IFU; n = 1 control). Systemic and rectal SHIV RNA levels and cytokines were measured by real-time PCR and Luminex assays, respectively.

RESULTS

Macaques were successfully Chlamydia infected. Rectal SHIV shedding (P = 0.02 χ(2) ) and levels of G-CSF, IL-1ra, IL-6, IL-8, IFN-γ, and TNF-α (P ≤ 0.01, Mann-Whitney) in rectal secretions increased following infection.

CONCLUSIONS

These pilot data successfully demonstrate rectal C. trachomatis-SHIV coinfection in cynomolgus macaques and suggest the feasibility of a rectal C. trachomatis model for SHIV susceptibility and biomedical prevention studies in the context of rectal STIs.

Development of a liposome microbicide formulation for vaginal delivery of octylglycerol for HIV prevention

The feasibility of using a liposome drug delivery system to formulate octylglycerol (OG) as a vaginal microbicide product was explored. A liposome formulation was developed containing 1% OG and phosphatidyl choline in a ratio that demonstrated in vitro activity against Neisseria gonorrhoeae, HSV-1, HSV-2 and HIV-1 while sparing the innate vaginal flora, Lactobacillus. Two conventional gel formulations were prepared for comparison. The OG liposome formulation with the appropriate OG/lipid ratio and dosing level had greater efficacy than either conventional gel formulation and maintained this efficacy for at least 2 months. No toxicity was observed for the liposome formulation in ex vivo testing in a human ectocervical tissue model or in vivo testing in the macaque safety model. Furthermore, minimal toxicity was observed to lactobacilli in vitro or in vivo safety testing. The OG liposome formulation offers a promising microbicide product with efficacy against HSV, HIV and N. gonorrhoeae.

Lactobacilli at the front line of defense against vaginally acquired infections

Probiotics are microorganisms that provide a health benefit to the host and are promoted as alternatives for the treatment and prevention of infectious diseases and other conditions. One of the most rapidly developing areas of probiotic research is in the management of vaginally acquired infections. Several Lactobacillus species produce compounds that kill or inhibit the growth of vaginally acquired pathogens. Other lactobacilli reduce the adherence of pathogens to urogenital epithelial cells in culture. This article discusses the mechanisms by which vaginal lactobacilli prevent pathogen colonization of the urogenital tract, and potential mechanisms that warrant investigation. Animal models and clinical studies, while limited, are discussed with the idea that these are the next critical steps to advance the study of probiotics for the treatment and prevention of vaginally acquired infections.

[Application studies of animal models in evaluating safety and efficacy of HIV-1 microbicides]

As the HIV/AIDS pandemic continues unabated, novel prophylactic strategy for the spread of HIV are urgently needed. Topical microbicides are designed to prevent transmission of HIV when applied vaginally or rectally. Although there are many microbicide candidates in the pipeline, animal models for evaluating their safety and efficacy are urgently needed. On the basis of comparing the non-primate small animal models and the non-human primate animal models in evaluating safety and efficacy of HIV microbicides, this review summarizes the major advantages and disadvantages of the relevant animal models. The suggested direction of research that would benefit the development of microbicides is also reviewed.

Microbicide safety/efficacy studies in animals: macaques and small animal models

PURPOSE OF REVIEW

A number of microbicide candidates have failed to prevent HIV transmission in human clinical trials, and there is uncertainty as to how many additional trials can be supported by the field. Regardless, there are far too many microbicide candidates in development, and a logical and consistent method for screening and selecting candidates for human clinical trials is desperately needed. The unique host and cell specificity of HIV, however, provides challenges for microbicide safety and efficacy screening, that can only be addressed by rigorous testing in relevant laboratory animal models.

RECENT FINDINGS

A number of laboratory animal model systems ranging from rodents to nonhuman primates, and single versus multiple dose challenges have recently been developed to test microbicide candidates. These models have shed light on both the safety and efficacy of candidate microbicides as well as the early mechanisms involved in transmission. This article summarizes the major advantages and disadvantages of the relevant animal models for microbicide safety and efficacy testing.

SUMMARY

Currently, nonhuman primates are the only relevant and effective laboratory model for screening microbicide candidates. Given the consistent failures of prior strategies, it is now clear that rigorous safety and efficacy testing in nonhuman primates should be a prerequisite for advancing additional microbicide candidates to human clinical trials.

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.

Preclinical safety assessments of UC781 anti-human immunodeficiency virus topical microbicide formulations

The nonnucleoside reverse transcriptase inhibitor UC781 is under development as a potential microbicide to prevent sexual transmission of human immunodeficiency virus type 1 (HIV-1). Two gel formulations of UC781 (0.1% and 1.0%) were evaluated in a range of preclinical safety assessments, including systemic absorption analysis following topical application in the pig-tailed macaque models for vaginally and rectally applied topical microbicides. High-sensitivity high-performance liquid chromatography analysis of serum samples showed that no systemic absorption of UC781 was detected after repeated vaginal or rectal application of either product. However, high levels of UC781 were detectable in the cervicovaginal lavage samples up to 6 h after product exposure. Both formulations were safe to the vaginal microenvironment, even with repeated daily use, as evidenced by colposcopy, cytokine analysis, and lack of impact on vaginal microflora. By contrast, rectal application of the 1.0% UC781 formulation caused an increased expression of numerous cytokines not observed after rectal application of the 0.1% UC781 formulation. These results provide additional support for the continued development of UC781 formulations as anti-HIV microbicides.

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.

Phenotypic and cytolytic activity of Macaca nemestrina natural killer cells isolated from blood and expanded in vitro

Natural killer (NK) cells from nonhuman primates have not been completely characterized, and methods for expanding nonhuman primates NK cells in vitro have been described only in rhesus species. The purpose of this report was to characterize NK cells in pigtail macaques (Macaca nemestrina), a species that is frequently used in studies of transplantation biology/immunology, virology, vaccine development, and reproductive biology. NK cells from Macaca nemestrina peripheral blood were best defined by the expression of CD16 and CD8alpha, and the absence of CD3. Subsets of these cells express CD56, NKp30, and NKp46. An enhanced ability to kill K562 cells was not present in fluorescence activated cell sorted (FACS)-purified CD16-/CD3+ and CD16-/CD56+ cells isolated from fresh peripheral blood. However, FACS-purified CD16+/CD3- and CD16+/CD56- cells were highly efficient killers of K562 cells. Macaca nemestrina NK cells can be expanded by in vitro culturing of FACS-purified CD16+/CD2-/CD3-/CD56- cells, or from peripheral blood cells depleted of cells expressing CD3, CD4, and HLA-DR. Cells in these cultures expand 70-fold after 21 days of culturing. After culturing, these cells express high levels of natural cytotoxicity receptors (NCRs) NKp30 and NKp46. NK cell populations obtained from FACS-purified CD16+/CD3-, CD16+/CD56- cells and CD3/CD4/HLA-DR-depleted cells were highly efficient killers of K562 cells. These data suggest that a population of highly enriched cytolytic NK cells can be obtained from purified CD16+/CD3- and CD16+/CD56- cells obtained from peripheral blood, as well as from cells that have been cultured and expanded from peripheral blood that is depleted of CD3/CD4/HLA-DR-expressing cells.

Preclinical safety and efficacy assessments of dendrimer-based (SPL7013) microbicide gel formulations in a nonhuman primate model

Three gel formulations (1%, 3%, and 5% [wt/wt]) of SPL7013, a dendrimer known to have antiviral (anti-human immunodeficiency virus and anti-herpes simplex virus) activities, completed a range of preclinical tests in the pigtailed macaque models for vaginally and rectally applied topical microbicide safety assessments. The vaginal safety profile of the 3% SPL7013 gel formulation was equal to that of the 1% formulation but was superior to that of the 5% formulation. The 3% SPL7013 gel was further evaluated for rectal safety and for antichlamydial efficacy with cervical challenge with Chlamydia trachomatis. This first-generation dendrimer-based product was shown to be safe to the vaginal and rectal microenvironments with repeated daily use. However, a single intravaginal application of the 3% (wt/wt) SPL7013 gel did not provide protection from the acquisition of cervical chlamydial infection.

Recommendations for the Nonclinical Development of Topical Microbicides for Prevention of HIV Transmission: An Update

The development of methods to prevent HIV infection is critical to curbing the rising epidemic. Topical microbicides represent a potential new strategy for reduction of HIV transmission. The purpose of this article is to update and expand upon the nonclinical recommendations of a previously published document on the development of microbicides prepared by the International Working Group on Microbicides. The nonclinical studies discussed here represent general concepts and regulatory considerations that are pertinent to the development of topical microbicides for prevention or reduction of HIV transmission. Essential early steps in product development include the determination of antiviral activity, cytotoxicity, mechanism of action, pathways to resistance, and cross-resistance to approved drugs. Other parameters to consider include activity against vaginal microflora and pathogens that cause sexually transmitted diseases. Before and during clinical trials, nonclinical data on toxicology and pharmacokinetics should be obtained. Finally, product quality issues, including microbicide formulation characteristics, interaction with other products, and stability, should be addressed.

Safety and Efficacy Evaluations for Vaginal and Rectal Use of BufferGel in the Macaque Model

BACKGROUND

The nonhuman primate model allows for safety and efficacy testing of topical microbicide products.

GOAL

The goal of this study was to evaluate the safety and efficacy of vaginal and rectal applications of BufferGel (ReProtect, Inc.).

STUDY DESIGN

The safety of repeated product applications was evaluated by microflora, pH, vaginal colposcopy, and rectal lavage. To test efficacy in preventing chlamydia, infection was documented by culture and nucleic acid amplification tests.

RESULTS

Repeated vaginal or rectal applications of BufferGel were not associated with significant changes in microflora. BufferGel use had a transient acidifying effect on vaginal and rectal pH. Colposcopic observations remained relatively normal in all test animals. A slightly increased incidence of epithelial desquamation was noted after rectal product use compared with the control group. BufferGel did not prevent cervical or rectal chlamydial infection.

CONCLUSION

BufferGel has an acceptable safety profile after repeated vaginal and rectal use, but does not prevent chlamydial infection in the macaque models.

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.

Vaginal microbicides and teenagers

PURPOSE OF REVIEW

Sexually active teens are at significant risk from sexually transmitted infections and girls and women bear the greatest burden of these infections. New methods, such as vaginal microbicides, would provide female controlled options. Microbicides are currently in development and thus it is timely to discuss the progress made and factors that may influence acceptability for teens.

RECENT FINDINGS

Microbicide development presents many challenges, and several different potential mechanisms of action are being explored. There is interest in these products from women and men, and specific preferences are being investigated. Adolescents, due to reproductive system immaturity, developing cognitive abilities and the psychosocial context of their relationships, present a special set of challenges in efforts to foster microbicide use.

SUMMARY

Vaginal microbicides are on the horizon. Further study into teen issues is required to develop successful strategies for marketing and encouraging adolescent use of microbicides.

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.