Effect of Corynebacterium acnes on interferon production in mice

Chikungunya virus pathogenesis: From bedside to bench

Chikungunya virus (CHIKV) is an arbovirus transmitted to humans by mosquito bite. A decade ago, the virus caused a major outbreak in the islands of the Indian Ocean, then reached India and Southeast Asia. More recently, CHIKV has emerged in the Americas, first reaching the Caribbean and now extending to Central, South and North America. It is therefore considered a major public health and economic threat. CHIKV causes febrile illness typically associated with debilitating joint pains. In rare cases, it may also cause central nervous system disease, notably in neonates. Joint symptoms may persist for months to years, and lead to arthritis. This review focuses on the spectrum of signs and symptoms associated with CHIKV infection in humans. It also illustrates how the analysis of clinical and biological data from human cohorts and the development of animal and cellular models of infection has helped to identify the tissue and cell tropisms of the virus and to decipher host responses in benign, severe or persistent disease. This article forms part of a symposium in Antiviral Research on "Chikungunya discovers the New World".

A mouse model for Chikungunya: young age and inefficient type-I interferon signaling are risk factors for severe disease

Chikungunya virus (CHIKV) is a re-emerging arbovirus responsible for a massive outbreak currently afflicting the Indian Ocean region and India. Infection from CHIKV typically induces a mild disease in humans, characterized by fever, myalgia, arthralgia, and rash. Cases of severe CHIKV infection involving the central nervous system (CNS) have recently been described in neonates as well as in adults with underlying conditions. The pathophysiology of CHIKV infection and the basis for disease severity are unknown. To address these critical issues, we have developed an animal model of CHIKV infection. We show here that whereas wild type (WT) adult mice are resistant to CHIKV infection, WT mouse neonates are susceptible and neonatal disease severity is age-dependent. Adult mice with a partially (IFN-alpha/betaR(+/-)) or totally (IFN-alpha/betaR(-/-)) abrogated type-I IFN pathway develop a mild or severe infection, respectively. In mice with a mild infection, after a burst of viral replication in the liver, CHIKV primarily targets muscle, joint, and skin fibroblasts, a cell and tissue tropism similar to that observed in biopsy samples of CHIKV-infected humans. In case of severe infections, CHIKV also disseminates to other tissues including the CNS, where it specifically targets the choroid plexuses and the leptomeninges. Together, these data indicate that CHIKV-associated symptoms match viral tissue and cell tropisms, and demonstrate that the fibroblast is a predominant target cell of CHIKV. These data also identify the neonatal phase and inefficient type-I IFN signaling as risk factors for severe CHIKV-associated disease. The development of a permissive small animal model will expedite the testing of future vaccines and therapeutic candidates.

Induction of murine gamma interferon production by lipopolysaccharide and interleukin-2 in Propionibacterium acnes-induced peritoneal exudate cells

Lipopolysaccharide (LPS) induces high levels of gamma interferon (IFN-gamma) in the circulation of mice pretreated with heat-killed Propionibacterium acnes. The following results were obtained in the present study. LPS, as well as interleukin-2 (IL-2), was also able to induce IFN-gamma in vitro in peritoneal exudate cells (PEC) from such mice. Splenocytes and lymph node cells from these mice or resident peritoneal cells from control mice produced trace or undetectable amount of IFN-gamma upon exposure to LPS. A synergistic effect on IFN-gamma induction was observed when LPS was added to a culture of PEC together with IL-2. Indomethacin augmented the induction of IFN-gamma by LPS or IL-2, and prostaglandin E2 reversed its effect. Deprivation of plastic-adherent or nylon wool-adherent cells abolished the induction by LPS or IL-2, whereas it did not affect that by concanavalin A. Culture supernatant of plastic-adherent cells incubated with LPS stimulated the nylon wool-nonadherent cells to produce IFN-gamma in the presence of IL-2, but interleukin-1 or phorbol myristic acetate did not replace the LPS-stimulated supernatant. The ability of PEC to produce IFN-gamma measured as a function of time after P. acnes injection increased in proportion to their natural killer (NK)-like activity against YAC-1 cells. Moreover, treatment of PEC with monoclonal anti-Thy-1 antibody or with anti-asialo GM1 antiserum plus complement eliminated the production of IFN-gamma and the NK-like activity simultaneously, whereas treatment with monoclonal anti-Lyt-2 antibody plus complement did not. These results suggest that IL-2 and some unidentified factor released from plastic-adherent cells by LPS stimulation cooperatively induce IFN-gamma production in activated, Thy-1- and asialo GM1-positive NK-like cells appearing in inflammatory reactions and that prostaglandin E2 regulates IFN-gamma production in these cells.

Natural antiviral activity of mouse macrophages against encephalomyocarditis virus

Resident mouse peritoneal cells (PC) express a significant antiviral activity against encephalomyocarditis virus (EMCV) in vitro, as judged by decreased virus yield from infected mouse embryo fibroblasts (MEF). This natural antiviral activity of PC was not due either to enhanced lysis of virus-infected cells, as these were protected from lysis rather than destructed by PC, or to interferon (IFN) production, as no direct correlation between IFN and anti-EMCV activity was found. Among PC, macrophages (M phi) appear to be responsible for the anti-EMCV activity, which was indeed attributable to a Thy 1.2-negative, adherent mononuclear cell. Moreover, M phi-defective C3H/HeJ mice showed a significant impairment of anti-EMCV activity, whereas M phi of mice defective for natural killer (NK) activity (bg/bg, SJL/J) or for mature T cells (nu/nu) possessed an intact antiviral capacity.

Interferon inducibility in mice treated with Corynebacterium parvum

Mice were given single intraperitoneal (i.p.) injections of Corynebacterium parvum, followed, after different time intervals, by i.p. injections of the interferon inducers polyinosinic-polycytidylic acid (poly-I:poly-C), 10-carboxymethyl-9-acridanone (CMA) or herpes simplex virus. With all three inducers production of interferon in the peritoneal cavity was enhanced in C. parvum-pretreated mice. Production of circulating interferon in C. parvum-pretreated mice was enhanced with CMA and depressed with poly-I:poly-C as inducers. This modulation of the interferon response was prominent for at least 10 weeks after C. parvum injection and then gradually reverted. The increased local interferon production seemed to be caused by macrophages still activated several weeks after treatment with C. parvum.

Protection of mice against mouse hepatitis virus by Corynebacterium parvum

C57BL/6 mice that are highly susceptible to infection with mouse hepatitis virus type 3 were protected against intraperitoneal viral infection by simultaneous intraperitoneal injection of Corynebacterium parvum. No protection was observed when C. parvum was given intravenously or when it was injected intraperitoneally 3 days before viral infection. Protective effects were, however, consistently found when C. parvum was given 2 h before or 2 h after viral infection. Activity was seen only against 10 50% lethal doses and not against 100 50% lethal doses. C. parvum also caused a significant decrease of virus type 3. These data suggest a direct effect of C. parvum on virus-susceptible cells. Injection of C. parvum in mice caused activation of natural killer (NK) cells and of interferon production. However, these two effects were equally demonstrable at high and low doses of C. parvum, whereas protection against mouse hepatitis virus type 3 was not demonstrable at low doses of C. parvum. Thus, antiviral protection may be dissociated from activation of NK cells and induction of interferon.

Enhancement of resistance to murine osteogenic sarcoma in vivo by an extract of Brucella abortus (Bru-Pel): association with activation of reticuloendothelial system macrophages

The administration of an aqueous-ether extracted residue of Brucella abortus (Bru-Pel) inhibits development of transplanted osteogenic sarcomas in mice as evidenced by a decrease in mortality. At least one mechanism through which Bru-Pel modulates host resistance is activation of macrophages of the reticuloendothelial system. Peritoneal macrophages harvested from mice receiving Bru-Pel were cytotoxic for osteogenic sarcoma cells in vitro, limited the replication of vaccinia virus in cell cultures, and demonstrated enhanced emittance of chemiluminescence during phagocytosis of zymosan particles of Candida albicans. The concept of reticuloendothelial system activation was further supported by the evidence that administration of Bru-Pel enhanced resistance of mice to challenge with a lethal inoculum of Listeria monocytogenes. These observation support the hypothesis that Bru-Pel shares a number of characteristics with recognized immunomodulating agents and that one mechanism by which it modulates host resistance to tumors, to virus infections, and to challenge with L. monocytogenes is through activation of macrophages.

Peritoneal macrophage activation indicated by enhanced chemiluminescence

A number of studies have demonstrated the ability of various bacterial preparations, protozoa, and chemicals to activate macrophages and concomitantly to enhance host resistance to both tumors and infections. Recently, viral infections have been shown to have a similar effect upon macrophage function. To better define the metabolic state of activated macrophages, we have evaluated the ability of peritoneal cells (PC) from vaccinia virus- or murine cytomegalovirus-infected or Corynebacterium parvum-treated mice to emit chemiluminescence (CL) during phagocytosis of zymosan particles or yeasts. PC from C. parvum-treated mice (1,400 microgram intraperitoneally) emitted enhanced CL over controls on days 3, 6, 14, and 21 after treatment, thereby establishing the emission of CL as a correlate of metabolic activation. Previous evidence for activation of PC from vaccinia virus-infected mice (10(8) plaque-forming units) was confirmed by demonstration of enhanced levels of CL on days 3, 6, and 13 after murine infection. Likewise, PC from mice infected with murine cytomegalovirus (10(5) plaque-forming units) 3, 6, or 13 days previously demonstrated augmented levels of CL over controls. Opsonized virus particles (vaccinia virus or murine cytomegalovirus) failed to induce the emission of CL with PC from mice infected with the isologous virus. Our data further demonstrate the immunomodulationinduced by virus infections and suggest that the detection of CL is an easily quantitated correlate of macrophage activation which may be helpful in defining metabolic alterations induced during activation.

Nonsporing, anaerobic, gram-positive rods in saliva and the gingival crevice of humans

Quantitative and qualitative examination of anaerobically isolated flora of the gingival crevice and saliva was carried out. It was found that half the organisms were anaerobes and that there were twice as many gram-positive organisms as there were gram-negative ones. Rods were predominant in the gingival crevice (60.5%) and cocci in saliva (69.1%). Of the total organisms, nonsporing, gram-positive anaerobic rods accounted for 24% in the gingival crevice and 9.7% in saliva. These organisms were characterized on the basis of the type of fatty acids produced from glucose and various biochemical reactions. They belonged to the following genera: Actinomyces, Propionibacterium, Arachnia, Lactobacillus, Eubacterium, and Bifidobacterium. Bifidobacteria were present only in saliva. Although members of the other genera were present both in the gingival crevice and saliva, there were considerable differences in the proportion of any particular organism (in relation to the total anaerobic viable count) between the two sites. The result of this study also indicates a greater than previously appreciated level of Propionibacterium and Arachnia in the human mouth.

Effect of Corynebacterium acnes on interferon production in mouse peritoneal exudate cells

Corynebacterium acnes, an organism closely related to C. parvum, has been recognized to have a striking effect on the reticuloendothelial system, as well as on both humoral and cellular immunity. In mice previously exposed to C. acnes, serum interferon levels induced by injection of Newcastle disease virus (NDV), Chikungunya virus (CV), and polyinosinic-polycytidylic acid are suppressed. When peritoneal macrophages and lymphocytes from animals exposed to C. acnes were cultivated in vitro, their capacity to produce interferon in response to NDV and CV was reduced. Furthermore, the interferon-producing capacity of these cells in tissue culture was inhibited after exposure to C. acnes to vitro. Exposure of separated populations of peritoneal macrophages and lymphocytes to C. acnes in vitro demonstrated that the interferon response to NDV by both cell types is inhibited. Peritoneal macrophages appear to be the major contributor to the interferon response in this system. Finally, this inhibitory effect was shown to occur after exposure to a purified cell wall preparation of C. acnes organisms, as well as a lipid extract of this preparation.

Enhanced effect of repeated administration of bacterial vaccine against viral respiratory infection

Administration of a standard bacterial vaccine (SBV) affords some protection against influenza infection in mice if given 4 to 5 h before inoculation of the virus. This effect was enhanced by repeated injections of SBV 7 and 14 days earlier, as measured by the length of survival, mortality rate, development of gross pneumonia, and virus multiplication in the lungs. Serum interferon levels were likewise enhanced by immunization with SBV, which may, at least in part, explain the increased preventive effect.