When a virus encounters a susceptible cell, the virus enters and initiates cytocidal, persistent, latent or abortive infection. We recently reported that influenza virus (IV) induces persistent infection accompanied by cell survival and virus production in cultured amnion cells. In addition, cytocidal infection accompanied by apoptotic cell death and virus production occurred in cultured chorion cells. Both cell cultures were prepared from human fetal membranes.
1)IV induces cytocidal infection in a variety of cultures, such as HeLa and Madin-Darby canine kidney (MDCK) cell lines and human peripheral blood monocytes in vitro, all of which die through the mechanism of apoptosis.2-5) Furthermore, IV infection induces gene expression of inflammatory cytokines such as interleukin (IL)-1, IL-6, tumor necrosis factor (TNF)-a and interferon (IFN)-a/b, and C-C and C-X-C chemokines such as monocyte chemoattractant protein (MCP)-1, macrophage inflammatory protein (MIP)-1a, RANTES (regulated on activation, normal T cell expressed and secreted) and IFN-inducible protein (IP)-10, 6,7) and proapoptotic factors such as Fas and Fas ligand,8) which occur in infected host cells undergoing apoptosis. Apoptosis and inducible gene expression of inflammatory mediators therefore seem to be correlated. However, whether IV induces gene expression of inflammatory mediators during persistent infection remains unknown.We therefore extensively examined expression of mRNAs for inflammatory cytokines such as IL-1b, IL-6, TNF-a, IFN-a, IFN-b, IFN-g, macrophage colony-stimulating factor (M-CSF) and granulocyte macrophage colony-stimulating factor (GM-CSF), and Fas during cytocidal and persistent infections by reverse transcriptase-polymerase chain reaction (RT-PCR) analysis. Of note is the fact that IV infection induced the gene expression of a set of inflammatory cytokines during cytocidal infection accompanied by apoptotic cell death, but this induction was not present during persistent infection in the absence of apoptosis. In this paper we report a noticeable difference in gene expression of a set of inflammatory cytokines between cytocidal and persistent infections.
MATERIALS AND METHODSMaterials PCR primers for IFN-a, IFN-b, IFN-g, M-CSF and GM-CSF were originally designed according to published cDNA sequences. 9-13) PCR primers for Fas were based on the published DNA sequences for the primers.
14)PCR primers for IL-1b, IL-6, TNF-a and glycerol-3-phosphate dehydrogenase (G3PDH) were purchased from CLON-TECH Labs. Inc. (CA, U.S.A.). DNA sequences for the PCR primers are shown in Table 1. Neutralizing antibodies against Fas (Medical & Biological Labs. Co., Ltd., Nagoya, Japan), IFN-b (Yamasa Shoyu Co., Ltd., Tokyo, Japan), TNF-a and IFN-g (Genzyme Diagnostic, MA, U.S.A.) were purchased from the listed suppliers.Cell Culture and Virus Infection Primary cultured chorion and amnion cells were prepared from human fetal membranes obtained by cesarean section during the month of normal parturition as described.15) HeLa cell line was obtained from...