Interferon-γ Detection in Cultures of Newborn Cells Exposed toListeria monocytogenes

Abstract

Clearance of Listeria monocytogenes in experimental models of infection has underscored the importance of interferon-gamma (IFN-gamma) in host resistance to intracellular pathogens. Because L. monocytogenes infections are more severe in newborns than adults, we compared IFN-gamma accumulation in the supernatants of mononuclear cells infected in vitro from newborns with those from adults. Supernatants were assayed for IFN-gamma using an enzyme-linked immunosorbent assay. Uninfected newborn and adult mononuclear cells had less than 50 pg/ml of IFN-gamma at all times tested. IFN-gamma levels in supernatants from infected adult mononuclear cells at 24 h of culture (1.15 x 10(3) +/- 0.92 pg/ml) were greater than supernatants from infected newborn mononuclear cells (0.19 x 10(3) +/- 0.33 pg/ml). IFN-gamma concentrations in newborn cell cultures plateaued on day 3 of culture (1.6 x 10(3) +/- 1.1 pg/ml) and were not significantly less than concentrations from adult cells. However, adult cell IFN-gamma was further increased by day 5 (18.7 x 10(3) +/- 21.8 pg/ml). Because IFN-gamma plays a critical role in the host defense against L. monocytogenes, this delay in the release of IFN-gamma may be a factor in the increased susceptibility and severity of infection in the neonate.

CpG Oligodeoxynucleotides Enhance Neonatal Resistance to Listeria Infection

“…Neonates are at increased risk from many pathogens due to the immaturity of their immune system (22). In particular, previous studies showed that Ag-specific Th1 and cell-mediated immune responses are reduced in newborns (22)(23)(24), while the likelihood of developing tolerance is increased (34,35).…”

“…Neonates are at increased risk from many pathogens due to the immaturity of their immune system (22). In particular, previous studies showed that Ag-specific Th1 and cell-mediated immune responses are reduced in newborns (22)(23)(24), while the likelihood of developing tolerance is increased (34,35). Current results indicate that 1) immune cells from newborn mice respond to CpG ODN by secreting IFN-␥, IL-12, and TNF-␣; 2) CpG ODN "prime" immune cells to produce NO when subsequently exposed to bacterial products; and 3) newborn mice treated with CpG ODN resist infection by L. monocytogenes.…”

“…Neonates have a reduced capacity to mount Ag-specific Th1 immune responses (22)(23)(24). To evaluate whether TLR9-mediated activation of the innate immune system is similarly compromised, spleen cells from newborn and adult BALB/c mice were stimulated in vitro with CpG or control ODN.…”

“…Immaturity of the immune system may limit the ability of newborns to recognize PAMPs and mount a protective Th1 response (22)(23)(24). It is well established that neonates are at increased risk from a variety of pathogens, including Listeria (22).…”

“…It is well established that neonates are at increased risk from a variety of pathogens, including Listeria (22). This study examines the effect of CpG ODN in newborn mice using Listeria infection as a relevant model for monitoring the induction of protective immunity.…”