The effect of mouse infection with lactate dehydrogenase-elevating virus (LDV), a usually non-pathogenic virus, on concomitant bacterial endotoxin shock was analyzed, in terms of lethality and cytokine production. A strong enhancement of susceptibility to the shock was observed in mice acutely infected with this virus. It correlated with a sharp increase of tumor necrosis factor and leukemia inhibitory factor production and was controlled by the mouse genetic background. The viral infection led to an imbalance in the cytokine response to LPS, with an enhancement of pro-inflammatory cytokines, including IL-18 and IFN-gamma and a delayed secretion of anti-inflammatory IL-10 that could result in exacerbated macrophage activation. Enhanced IFN-gamma production was involved in the virus-induced susceptibility to shock. In sharp contrast with other viral infections, IFN-alpha/beta diminished IFN-gamma production and the resulting increased response to LPS in LDV-infected animals.
Two distinct pathways of gamma interferon (IFN-γ) production have been found in mice infected with lactate dehydrogenase-elevating virus. Both pathways involve natural killer cells. The first is mostly interleukin-12-independent and is not controlled by type I interferons. The second, which is suppressed by type I interferons, leads to increased levels of IFN-γ production and requires the secretion of interleukin-12. This regulation of IFN-γ production by type I interferons may help to control indirect pathogenesis induced by this cytokine.
Lactate dehydrogenase-elevating virus (LDV) exacerbates mouse susceptibility to endotoxin shock through enhanced tumour necrosis factor (TNF) production by macrophages exposed to lipopolysaccharide (LPS). However, the in vivo enhancement of TNF production in response to LPS induced by the virus largely exceeds that found in vitro with cells derived from infected animals. Infection was followed by a moderate increase of Toll-like receptor (TLR)-4/MD2, but not of membrane CD14 expression on peritoneal macrophages. Peritoneal macrophages from LDVinfected mice unresponsive to type I interferons (IFNs) did not show enhanced expression of TLR-4/MD2 nor of CD14, and did not produce more TNF in response to LPS than cells from infected normal counterparts, although the in vivo response of these animals to LPS was strongly enhanced. In contrast, the virus triggered a sharp increase of soluble CD14 and of LPS-binding protein serum levels in normal mice. However, production of these LPS soluble receptors was similar in LDV-infected type I IFN-receptor deficient mice and in their normal counterparts. Moreover, serum of LDV-infected mice that contained these soluble receptors had little effect if any on cell response to LPS. These results suggest that enhanced response of LDV-infected mice to LPS results mostly from mechanisms independent of LPS receptor expression.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.