A Broad Spectrum Chemokine Inhibitor Prevents Preterm Labor but Not Microbial Invasion of the Amniotic Cavity or Neonatal Morbidity in a Non-human Primate Model

Abstract

Leukocyte activation within the chorioamniotic membranes is strongly associated with inflammation and preterm labor (PTL). We hypothesized that prophylaxis with a broad-spectrum chemokine inhibitor (BSCI) would downregulate the inflammatory microenvironment induced by Group B Streptococcus (GBS, Streptococcus agalactiae) to suppress PTL and microbial invasion of the amniotic cavity (MIAC). To correlate BSCI administration with PTL and MIAC, we used a unique chronically catheterized non-human primate model of Group B Streptococcus (GBS)-induced PTL. In the early third trimester (128-138 days gestation; ∼29-32 weeks human pregnancy), animals received choriodecidual inoculations of either: (1) saline (N = 6), (2) GBS, 1-5 × 10 8 colony forming units (CFU)/ml; N = 5), or (3) pre-treatment and daily infusions of a BSCI (10 mg/kg intravenous and intra-amniotic) with GBS (1-5 × 10 8 CFU/ml; N = 4). We measured amniotic cavity pressure (uterine contraction strength) and sampled amniotic fluid (AF) and maternal blood serially and cord blood at delivery. Cesarean section was performed 3 days post-inoculation or earlier for PTL. Data analysis used Fisher's exact test, Wilcoxon rank sum and one-way ANOVA with Bonferroni correction. Saline inoculation did not induce PTL or infectious sequelae. In contrast, GBS inoculation typically induced PTL (4/5, 80%), MIAC and fetal bacteremia (3/5; 60%). Remarkably, PTL did not occur in the BSCI+GBS group (0/4, 0%; p = 0.02 vs. GBS), despite MIAC and fetal bacteremia in all cases (4/4; 100%). Compared to the GBS group, BSCI prophylaxis was associated with significantly lower cytokine levels including lower IL-8 in amniotic fluid (p = 0.03), TNF-α in fetal plasma (p < 0.05), IFN-α and IL-7 in the fetal lung (p = 0.02) and IL-18, 30 April 2020 Coleman et al. Chemokine Inhibition Prevents Preterm Labor IL-2, and IL-7 in the fetal brain (p = 0.03). Neutrophilic chorioamnionitis was common in the BSCI and GBS groups, but was more severe in the BSCI+GBS group with greater myeloperoxidase staining (granulocyte marker) in the amnion and chorion (p < 0.05 vs. GBS). Collectively, these observations indicate that blocking the chemokine response to infection powerfully suppressed uterine contractility, PTL and the cytokine response, but did not prevent MIAC and fetal pneumonia. Development of PTL immunotherapies should occur in tandem with evaluation for AF microbes and consideration for antibiotic therapy.

Landscape of Preterm Birth Therapeutics and a Path Forward

“…1) In vivo administration of BSCI (FX125L) using a nonhuman primate model of preterm labor induced by Group B Streptococcus (GBS) led to the powerful suppression of uterine activity and a complete blockade of PTB. BSCI treatment led to reduced maternal plasma IL-8 and IL-1β inhibited myometrial gap junction protein connexin 43 mRNA levels and reduced pro-inflammatory cytokines in amniotic fluid, chorioamniotic membrane, fetal plasma, lungs, and brain compared to GBS alone [210]. (2) Prophylactic in vivo administration of BSCI (BN83470) decreased LPS-induced PTB in pregnant mice, significantly inhibited neutrophil infiltration in the mouse myometrium, and significantly attenuated multiple cytokine/chemokine expression in maternal tissues (myometrium, decidua, plasma, and liver) [211].…”

“…Numerous studies over the past decade have focused on developing anti-inflammatory agents that target specific chemokines and chemokine receptors underlying pathologic inflammation in certain human diseases. Successes in the development of BSCIs for human immunodeficiency virus (HIV) treatment and prevention of cancer metastasis have spurred recent interest in studying the use of BSCIs in preventing or delaying PTB in high-risk pregnant women [208][209][210]. The exploration of BSCIs for use in addressing PTB is currently limited to animal models [210,211].…”

“…The first in vivo studies demonstrated that prophylactic administration of the BSCI compound 'BN83470 was able to prevent infection (LPS)-induced PTB in pregnant mice by blocking multiple inflammatory pathways in the uterus and leukocyte infiltration into uterine myometrium (Figure 2) [211]. As a proof of principle in a nonhuman primate model of Group B Streptococcus (GBS)-induced preterm labor, a novel BSCI compound 'FX125L' inhibited preterm labor and suppressed the cytokine response (Figure 2) [210]. Antibiotics were not administered in these experiments, and the GBS infection progressed and invaded the amniotic cavity and the fetus.…”

“…Current studies in animal models have suggested that BSCI compounds do not exhibit any significant fetal toxicity. Further study, particularly in human clinical trials, is required to elucidate the effect of BSCI on the fetal immune response and fetal development [210,211]. 1) In vivo administration of BSCI (FX125L) using a nonhuman primate model of preterm labor induced by Group B Streptococcus (GBS) led to the powerful suppression of uterine activity and a complete blockade of PTB.…”

Non-human Primate Models to Investigate Mechanisms of Infection-Associated Fetal and Pediatric Injury, Teratogenesis and Stillbirth

“…To overcome these challenges, a chronically catheterized pregnant NHP model was developed to monitor GBS-induced disease progression, immune response, and pregnancy outcomes following an experimental GBS inoculation ( Gravett et al, 1994 ; Adams Waldorf et al, 2011a ; Boldenow et al, 2016 ; Coleman et al, 2020 , 2021 ). This model is highly translational based on several characteristics: (1) inoculation of GBS in the choriodecidual space where GBS is hypothesized to first invade the placenta, (2) serial sampling of maternal and fetal blood and amniotic fluid, (3) monitoring of uterine contractions and fetal heart rate over time, and (4) administration of antibiotics or immunotherapeutics to prevent preterm birth or fetal injury ( Figure 5 ).…”