Listeria infection during pregnancy can cause the death of both mother and fetus. Previous studies established that immunostimulatory CpG oligodeoxynucleotides (ODN) increase the resistance of healthy adult mice to many infectious pathogens, including Listeria monocytogenes. This study examines whether the innate immune response elicited by CpG ODN can reduce the susceptibility of pregnant mice to lethal listeria challenge. The results indicate that CpG ODN treatment significantly improves maternal survival and reduces pathogen transmission to offspring. CpG ODN administered during pregnancy did not induce abortion, birth defects, or reduce the size or health of litters. These findings suggest that CpG ODN may provide a safe and effective means of improving the health of mothers and fetuses during pregnancy.Pregnancy leads to a generalized suppression of the adaptive immune system, typified by significantly decreased cell-mediated immunity and reduced Th1 responsiveness (25,31,33,38,39). This immunosuppressed state prevents maternal rejection of the fetus (31, 33) but has the unfortunate consequence of increasing maternal susceptibility to certain infectious agents (24,35).Listeria monocytogenes is a gram-positive intracellular bacterium that is a common cause of maternal infection (37,40). This pathogen can be transmitted from mother to fetus, substantially increasing the risk of abortion, stillbirth, congenital malformations, and neonatal mortality and morbidity (2,26,40). In the absence of preexisting maternal vaccination, there is no widely accepted strategy for preventing infection, since immunomodulatory therapy runs the risk of adversely affecting the neonate.Rapid activation of the innate immune system can limit the early spread of listeriae, allowing the host to develop sterilizing adaptive immunity (17, 21). The innate immune system is activated when Toll-like receptors (TLR) expressed by immune cells recognize pathogen-associated molecular patterns (PAMPs) expressed by infectious microorganisms (1,28). CpG motifs present in bacterial DNA act as PAMPs (11,18,22,41), interacting with TLR-9 to trigger an innate immune response in which lymphocytes, dendritic cells, and macrophages are stimulated to produce immunoprotective cytokines and chemokines (3,9,11,14,18,22,34,36). Treatment with CpG oligodeoxynucleotides (ODN) can improve the resistance of normal adult mice to a variety of bacterial, viral and parasitic pathogens (6,7,15,23,30,32,42). This immunoprotective effect peaks several days after CpG ODN administration and persists for several weeks (6,19,23).The current study was undertaken to determine whether CpG ODN can be of benefit during pregnancy, improving survival after listeria infection. The results indicate that CpG ODN treatment effectively stimulates the innate immune system of pregnant mice, improves maternal survival, and prevents pathogen transmission to offspring.
MATERIALS AND METHODSReagents. CpG (GCTAGACGTTAGCGT) and control (GCTAGAGCTTA GGCT) phosphorothioate ODN were synthesized at...