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.

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

BACKGROUND: A topical microbicide should protect against acquisition of sexually transmitted infection during both vaginal and rectal intercourse. The rectal microflora of the Macaca nemestrina (pig-tailed macaque) and humans were examined, as well as the histopathology of rectal tissues. In a subset of macaques, a human rectal isolate of Chlamydia trachomatis was inoculated into the rectum to establish rectal chlamydial infection. GOAL: To evaluate the comparability of the pig-tailed macaque rectal model with humans. STUDY DESIGN: Rectal swabs were collected for microbiologic analysis to characterize normal microflora in pig-tailed macaques and humans. Subsequently, 10 macaques received a rectal inoculation with C trachomatis, serovar D, prepared from a clinical rectal isolate. RESULTS: The rectal microflora of pig-tailed macaques (n = 80) were found to be comparable with the rectal flora of humans (n = 40). The prevalence of Lactobacillus in the rectum was higher in the macaques than in humans. Coliform and Enterococcus were decreased in the macaques, as compared with those of humans. In 9 of 10 macaques, rectal chlamydial infection was confirmed by culture or ligase chain reaction on days 2, 7, and 14 after inoculation. The test results were positive for rectal chlamydial infection by ligase chain reaction only for the remaining animal on day 14 after inoculation. CONCLUSIONS: The findings demonstrate that the rectal environment of the pig-tailed macaque is a useful model for further evaluation of newly developed topical microbicides for rectal use. Furthermore, such products can be evaluated for protection against rectal chlamydial infection in this model.

Antibody response to the chlamydial heat-shock protein 60 in an experimental model of chronic pelvic inflammatory disease in monkeys (Macaca nemestrina).

A primate model of chlamydial pelvic inflammatory disease was used to characterize serum antibody responses to the 60 kDa chlamydial heat shock protein (CHSP60). Forty monkeys were infected in the fallopian tubes with Chlamydia trachomatis and then were treated. Twenty-three (58%) monkeys developed antibodies against CHSP60, of whom 6 (15%) had CHSP60 responses that persisted throughout the study and 17 (42.5%) had a transient response. A persistent CHSP60 antibody response was correlated with being culture- or ligase chain reaction-positive in the fallopian tubes (P=.004), but not in the cervix pretreatment, and with being tubal-positive posttreatment (P=. 02). Compared with tubal-negative monkeys, tubal-positive monkeys had more intense CHSP60 responses (P=.006) that lasted longer (P=. 002). Among CHSP60 responders, an OD>0.5 was correlated with more severe salpingeal pathology before treatment (P=.04). CHSP60 antibody response may be useful as a marker of persistent chlamydial infection in the fallopian tubes.

Evidence of genetic susceptibility to Chlamydia trachomatis-induced pelvic inflammatory disease in the pig-tailed macaque.

The macaque model of chlamydial pelvic inflammatory disease (PID) demonstrates individual variability in the time of onset of intrapelvic adhesions. Some animals develop adhesions rapidly, within 2 weeks after a single tubal inoculation with Chlamydia trachomatis, while in others, adhesions are not observed until 2 weeks after a second tubal inoculation. To test whether this variability correlates with major histocompatibility complex (MHC) class I haplotype, we used macaque alloantisera and mouse anti-HLA monoclonal antibodies to determine the MHC class I haplotypes of 44 C. trachomatis-infected macaques (Macaca nemestrina). Macaques developing gross tubal adhesions after the first chlamydial inoculation were classified as susceptible (n = 29), while those not developing adhesions until after the second chlamydial inoculation were classified as relatively resistant (n = 15), to adhesion formation. Three antibody specificities correlated with susceptibility (odds ratio [OR] 5.2, P < 0.01; OR 6.1 and 4.3, P < 0.05), and two correlated with relative resistance to adhesions (OR 0.1, P < 0.05; OR 0.2, P < 0.01). Because several of these antibodies are cross-reactive, as many as five different MHC class I alleles (three increasing and two decreasing ORs) or as few as two different MHC class I alleles (one increasing and one decreasing OR) could be correlated with risk of adhesion formation. We conclude that in macaques, susceptibility or relative resistance to rapid formation of tubal adhesions is correlated with expression of MHC class I alleles, consistent with reports of MHC class I restriction of chlamydial immunopathology in humans.