MESSENGER RNA FOR INTERFERON PRODUCTION

Induction of interferon alpha from human lymphocytes by autologous, dengue virus-infected monocytes

Human monocytes actively replicate dengue virus. To dissect the primary immune responses to dengue virus-infected monocytes (DV-monocytes), we analyzed the interaction between autologous DV-monocytes and the peripheral blood lymphocytes (PBL) of dengue nonimmune donors. Interferon (IFN) activity was detected when PBL were cultured with DV-monocytes. Cell contact between PBL and DV-monocytes was required for IFN production; however, MHC compatibility between PBL and monocytes was not necessary. DV-monocytes fixed with paraformaldehyde or glutaraldehyde, which produced no infectious virus, also induced high levels of IFN from PBL. The ability of DV-monocytes to induce IFN correlated with the appearance of dengue antigens. The PBL that produce IFN were characterized by FACS sorting using monoclonal and polyclonal antibodies. HLA-DR+ and T3- cells produced high titers of IFN, while HLA-DR- and T3+ cells produced very low or undetectable levels of IFN. Moderate titers of IFN were produced by cells contained in B cell fractions (surface immunoglobulin-positive, B1+, and Leu-12+), and cells contained in natural killer cell fractions (Leu-11+ and OKM1+). Therefore, IFN-producing cells are heterogeneous, and the predominant producer cells are characterized as HLA-DR+ and non-T lymphocytes. The IFN produced was characterized by RIA using mAbs to IFN-alpha and IFN-gamma. The IFN-alpha was the predominant IFN produced; in addition, a low level of IFN-gamma was also detected in some experiments. The culture fluids obtained from PBL exposed to autologous DV-monocytes, which contained high IFN activity, completely inhibited dengue virus infection of monocytes. These results suggest that IFN-alpha produced by PBL exposed to DV-monocytes may play an important role in controlling primary dengue virus infection.

Natural cytotoxicity of murine cytomegalovirus-infected cells mediated by mouse lymphoid cells: role of interferon in the endogenous natural cytotoxicity reaction

Lymphoid cells from unstimulated normal C57BL/6J mice were shown to lyse murine cytomegalovirus (MCMV)-infected syngeneic mouse embryo fibroblasts but not uninfected mouse embryo fibroblasts. This cytotoxicity by mouse effector cells was not restricted to MCMV-infected syngeneic cells since MCMV-infected xenogeneic rat heart fibroblasts were also lysed. Characterization of the effector cells mediating this cytotoxicity against MCMV-infected cells indicated that the effector cells are similar to described natural killer (NK) cells mediating lysis of tumor cells and virus-infected cells. Because of the described augmentation of NK activity by interferon, we examined the role of interferon in the NK reaction. Although low levels of virus-induced interferon were detectable in supernatants of MCMV-infected mouse embryo fibroblasts, no interferon was detectable in supernatants of MCMV-infected rat heart fibroblasts, a target significantly more sensitive to NK cytolysis than infected mouse embryo fibroblasts. We were able to augment the NK reaction against MCMV-infected cells by in vitro treatments with interferon. However, the amounts of interferon required for augmentation were significantly greater than the amounts generated by infected target cells. In vitro interferon-stimulated NK cells retained selective cytotoxic activity since they continued to remain incapable of lysing uninfected target cells. MCMV-infected rat heart fibroblasts induced more interferon and were also more susceptible to NK activity than MCMV-infected mouse embryo fibroblasts. In spite of this difference in interferon-inducing capacity, there was no augmentation of cytotoxicity of MCMV-infected mouse embryo fibroblasts when mouse splenocytes were cocultivated with both target cells. Finally, when production of interferon in the NK reaction was inhibited by the addition of actinomycin D, no reduction of NK activity was seen. Our findings suggest that native mouse NK cells can discriminate between MCMV-infected cells and uninfected cells, this ability leading to the selective lysis of the virus-infected cells. Furthermore, although we could demonstrate augmentation of NK activity by interferon, interferon activation of NK cells may not be a necessary precondition for the development of endogenous NK activity.

Role of interferon in the propagation of MM virus in L cells

MM virus propagated in mouse brain replicates to low titers in L cells without production of cytopathic effect (CPE). After growing the virus in BHK-21 cells, however, the virus replicates to high titers in L cells with complete CPE. It was found that suspensions of MM virus propagated in L cells directly from the mouse brain contained much more interferon than did suspensions of virus which had first been grown in BHK-21 cells. Mouse brain suspensions of the virus were also found to contain high interferon titers. Treatment of L cells with actinomycin D before infection with mouse brain-grown virus resulted in full virus replication with CPE. BHK-21 cell-grown virus diluted in L cell interferon behaved like mouse brain-grown virus in L cells. It is concluded that the presence of interferon in the inoculum is largely responsible for the suppression of MM virus replication in L cells.

Leukocytes and interferon in the host response to viral infections. II. Enhanced interferon response of leukocytes from immune animals

Glasgow, Lowell A. (University of Rochester School of Medicine and Dentistry, Rochester, N.Y.). Leukocytes and interferon in the host response to viral infections. II. Enhanced interferon response of leukocytes from immune animals. J. Bacteriol. 91:2185-2191. 1966.-The production of interferon was studied under in vitro conditions in peritoneal leukocytes or macrophages from mice immunized with Chikungunya virus (CV). Cultures of leukocytes obtained from animals immune to CV produced 2- to 10-fold greater amounts of interferon when exposed to an inoculum of CV than similar cell preparations from nonimmune, control animals. The viral inhibitor produced in increased quantity by CV-immune leukocytes had the biological and biochemical properties of interferon. The enhanced interferon production was inhibited by actinomycin D. This response of immune leukocytes was specific, and was initiated only by CV; it was not observed in leukocytes from animals immunized against other viruses which were challenged with CV. The presence of neutralizing antibody could not be related to this response. The observed increase in interferon production was not dependent upon an enhanced virus uptake. The data are presented as a possible new dimension of the "immune response" and may suggest a mechanism for the phenomenon of "tissue immunity."

Effect of interferon on early interferon production

Chick embryo cells given prior treatment with interferon make new interferon earlier and in larger quantities upon stimulation with Chikungunya virus than cells not so treated. By the criterion of loss of sensitivity to actinomycin, the time needed for formation of messenger RNA for interferon was decreased in the primed cells. Thus interferon affects virus action within 1 hour after infection.