Maternal Vaginal Lactoferrin Ameliorates Vertical Escherichia coli Transmission Independent of Innate Immune Modulation

Abstract

Escherichia coli is a leading cause of neonatal early-onset sepsis. Maternal administration of bovine lactoferrin (BLF), an antimicrobial and immunomodulatory protein, may protect offspring from vertical E. coli transmission and influence innate immune responses. We investigated if maternal BLF vaginal administration reduces infection and alters CXCL2 (IL- 8 homologue) production in embryos following maternal vaginal E. coli inoculation. Pregnant C57BL/6 mice received BLF (75 mg/mL) or placebo vaginally in a novel bi-gel on embryonic (E) days 16 and 17, followed by vaginal inoculation with 105 colony forming units (CFU) of the neonatal E. coli strain RS218 on E17. Embryos were collected on E18, and liver–spleen tissue homogenates were plated to quantify E. coli CFU. CXCL2 concentrations in homogenates were measured by ELISA. Four separate experiments were conducted encompassing 35 embryos in the BLF group, and 31 in the placebo group. Bacterial load was analyzed applying a generalized linear mixed model with a negative binomial distribution with treatment and CXCL2 as predictors, including random mouse effects. Spearman analyses were done to assess correlation between CFU and CXCL2 levels. P <0.05 was considered significant. Placebo embryos had a 12.5-fold increase in bacterial load as compared to embryos from BLF-treated mothers (incidence rate ratio (IRR) = 12.5; 95% CI 3.9-39.7, p < 0.001), supporting a strong protective effect of BLF on infection severity (Fig. 1). In addition, bacterial load was associated with CXCL2 concentrations (IRR = 4.3; 95% CI 2.6– 7.2; p < 0.001), indicating a strong positive relationship between bacterial infection and CXCL2 production. This was further supported by Spearman analysis, which indicated positive correlations for both treatment groups (BLF: r = 0.49, p < 0.001; placebo: r = 0.61, p < 0.001) (Fig. 2). While increased bacterial loads correlated strongly with increased CXCL2 levels, we did not observe a significant difference in CXCL2 concentrations between treatment groups. Maternal vaginally administered BLF significantly reduced neonatal E. coli burden. CXCL2 levels positively correlated with bacterial loads but were not significantly altered by treatment. Further studies are needed to elucidate lactoferrin’s effects on innate host responses to neonatal E. coli infection.