Recombinant murine gamma interferon induces enhanced resistance to Listeria monocytogenes infection in neonatal mice.

Neonatal mice within 24 h of birth were highly susceptible to intraperitoneal infection with Listeria monocytogenes. The 50% lethal dose of bacterial cells was 6.3 X 10(1) CFU for neonates and 3.2 X 10(6) CFU for adult mice. A single injection of recombinant murine gamma interferon (rMuIFN-gamma) protected neonatal mice from simultaneous challenge with a lethal dose of L. monocytogenes cells. The rMuIFN-gamma effect was dose dependent: protection was consistently observed in mice treated with rMuIFN-gamma at doses of more than 4 X 10(2) U (0.1 microgram of protein) per mouse. Bacterial growth in the spleens and livers of rMuIFN-gamma-treated neonates was significantly suppressed in comparison with that in the nontreated controls. The infected neonatal mice showed acquired antilisterial resistance against secondary intravenous infection after 4 weeks of age, and this resistance was significantly augmented in mice that had been treated with rMuIFN-gamma.     

Divergent role of gamma interferon in a murine model of pulmonary versus systemic Klebsiella pneumoniae infection

Klebsiella pneumoniae is a leading cause of both community-acquired and nosocomial gram-negative-bacterial pneumonia. A further clinical complication of pulmonary K. pneumoniae infection is dissemination of bacteria from the lung into the peripheral blood, resulting in bacteremia concurrent with the localized pulmonary infection. Here, we report studies detailing the divergent role of gamma interferon (IFN-gamma) in pulmonary versus systemic K. pneumoniae infection. Intratracheal inoculation of IFN-gamma knockout mice resulted in significantly increased mortality compared to that observed for wild-type infected animals. Increased mortality correlated with a 100-fold increase in pulmonary bacteria within 2 days postinfection and upregulation of lung-associated interleukin-10 (IL-10) mRNA. Interestingly, IFN-gamma knockout mice had a twofold reduction in plasma aminospartate transferase activity, indicating diminished liver injury following peripheral blood bacterial dissemination. To study the host response towards blood-borne bacteria in the absence of the ongoing pulmonary infection, intravenous inoculation studies were initiated. IFN-gamma knockout mice were no more susceptible to intravenous infection than their wild-type counterparts. The consistent observation in IFN-gamma knockout mice was for improved survival correlating with increased clearance of blood- and liver-associated bacteria. Intravenous inoculation resulted in a two- to threefold increase in hepatic IL-10 production 24 and 48 h postinfection. Liver injury was also significantly reduced in IFN-gamma knockout mice. These data indicate that IFN-gamma secretion is a critical mediator in the resolution of localized gram-negative pulmonary pneumonia. Surprisingly, host responses towards systemic infection with the same bacteria appear to be IFN-gamma independent.     

The glycoprotein nature of murine gamma interferon

Summary Synthesis of murine gamma interferon (MuIFN) by phytohemagglutinin (PHA)-stimulated spleen cells was inhibited in a dose-dependent manner by graded concentrations of tunicamycin or 2-deoxy-glucose, both of which inhibit glycosylation. The homologous (murine) and heterologous (rat) antiviral activities of the MuIFN preparations secreted in the presence of the various concentrations of either glycosylation inhibitor were reduced to similar degrees. MuIFN synthesized in the presence of tunicamycin (tunicamycin-MuIFN) exhibited a lower molecular weight (MW), a lack of binding to immobilized Concanavalin-A (Con A), and different charge properties when compared to MuIFN produced in absence of inhibitor (control-MuIFN). Potent rabbit and rat neutralizing antibodies raised against a control-MuIFN subcomponent, isolated by its specific binding to a Con A affinity column, neutralized the antiviral activity of tunicamycin-MuIFN to the same degree as the immunogen.With 4 Figures     

Roles of interleukin-12 and gamma interferon in murine Chlamydia pneumoniae infection

BALB/c and strain 129 mice infected intranasally with Chlamydia pneumoniae displayed a moderate-to-severe inflammation in the lungs and produced interleukin-12 (IL-12), gamma interferon (IFN-gamma), tumor necrosis factor alpha (TNF-alpha), and IL-10, with peak levels on days 1 to 3 postinfection (p.i.), returning to basal levels by day 16 p.i. Anti-IL-12 treatment resulted in less-severe pathological changes but higher bacterial titers on days 3 and 7 p.i. By day 16 p.i., the inflammatory responses of control antibody-treated mice subsided. The bacterial titers of both anti-IL-12- and control antibody-treated mice decreased within 3 weeks to marginally detectable levels. Anti-IL-12 treatment significantly reduced lung IFN-gamma production and in vitro spleen cell IFN-gamma production in response to either C. pneumoniae or concanavalin A. In gamma-irradiated infected mice, cytokine production was delayed, and this delay correlated with high bacterial titers in the lungs. Following C. pneumoniae infection, 129 mice lacking the IFN-gamma receptor alpha chain gene (G129 mice) produced similar IL-12 levels and exhibited similarly severe pathological changes but had higher bacterial titers than 129 mice. However, by day 45 p.i., bacterial titers became undetectable in both wild-type 129 and G129 mice. Thus, during C. pneumoniae lung infection, IL-12, more than IFN-gamma, plays a role in pulmonary-cell infiltration. IFN-gamma and IL-12, acting mostly through its induction of IFN-gamma and Th1 responses, play an important role in controlling acute C. pneumoniae infection in the lungs, but eventually all mice control the infection to undetectable levels by IL-12- and IFN-gamma-independent mechanisms.     

Effect of gamma interferon on resolution of murine chlamydial genital infection.

Mice infected in the genital tract with the Chlamydia trachomatis agent of mouse pneumonitis were treated with monoclonal rat anti-gamma interferon (anti-IFN-gamma) antibody to determine whether IFN-gamma participated in the resolution of the infection. In two experiments, anti-IFN-gamma antibody treatment resulted in significantly prolonged infections. In support of these data, passive administration of recombinant IFN-gamma to chronically infected nu/nu mice was able to bring about resolution of the infection in some animals.     

Role of gamma interferon in cellular immune response against murine Encephalitozoon cuniculi infection

Microsporidia are obligate intracellular protozoan parasites that cause a wide variety of opportunistic infection in patients with AIDS. Because it is able to grow in vitro, Encephalitozoon cuniculi is currently the best-studied microsporidian. T cells mediate protective immunity against this parasite. Splenocytes obtained from infected mice proliferate in vitro in response to irradiated parasites. A transient state of hyporesponsiveness to parasite antigen and mitogen was observed at day 17 postinfection. This downregulatory response could be partially reversed by addition of nitric oxide (NO) antagonist to the culture. Mice infected with E. cuniculi secrete significant levels of gamma interferon (IFN-gamma). Treatment with antibody to IFN-gamma or interleukin-2 (IL-12) was able to neutralize the resistance to the parasite. Mutant animals lacking the IFN-gamma or IL-12 gene were highly susceptible to infection. However, mice unable to secrete NO withstood high doses of parasite challenge, similar to normal wild-type animals. These studies describe an IFN-gamma-mediated protection against E. cuniculi infection that is independent of NO production.     

The role of gamma interferon in immune resistance to vaginal infection by herpes simplex virus type 2 in mice.

We investigated the role of interferon gamma (IFN-gamma) in a mouse model of immunity to vaginal infection by herpes simplex virus type 2 (HSV-2). Within 8 h after immune mice were challenged intravaginally with HSV-2, IFN-gamma concentrations in vaginal secretions reached levels that can be antiviral in vitro. This rapid synthesis of IFN-gamma occurred in immune-challenged mice but not in nonimmune-challenged mice, indicating that it required memory T cells. Immunostaining and in situ hybridization revealed that the IFN-gamma was synthesized by cells whose morphological appearance suggested that they were lymphocytes and macrophage-like cells in the mucosa. The presence of IFN-gamma in vaginal secretions was correlated with upregulation of MHC class II antigens in the epithelium and with vigorous (30-fold) recruitment of T and B lymphocytes into the vagina. In vivo administration of anti-IFN-gamma to immune mice 17 h before virus challenge blocked the subsequent appearance of IFN-gamma in vaginal secretions, blocked upregulation of class II antigens, blocked adherence of T cells to endothelium and their recruitment into the vagina, and markedly reduced immunity against reinfection of the vaginal epithelium.     

Analysis of age-dependent resistance to murine coronavirus JHM infection in mice.

Resistance to intraperitoneal murine coronavirus JHM infection in mice develops with age. C3H mice were found to be fully susceptible up to the age of 20 days and resistant after 23 days of age. Protection of susceptible animals from death due to infection could be achieved by maternal antibodies or by transfer of spleen cells from immunized, but not from nonimmunized, donor mice. Lack of protection by transfer of unprimed adult spleen cells was not related to immunosuppression by the host. Moreover, resistance of adult mice could not be abrogated by application of lymphocytes from suckling mice, although immune suppression by other means did affect the resistance of adult animals. On the other hand, spleen cells from nonimmunized mice could be primed with inactivated JHM virus in suckling mice and protected these mice from death due to a subsequent virus infection. Thus, the outcome of infection with JHM virus in suckling and adult mice can be influenced by immunological events, but is not exclusively due to the different stages of immune competence.     

Role of gamma interferon in Helicobacter pylori induction of inflammatory mediators during murine infection

Gamma interferon (IFN-gamma) has been proposed to play an important role in Helicobacter-related gastritis. Using the IFN-gamma gene knockout (IFN-gamma(-/-)) mouse model and a murine gastric epithelial cell line, GSM06, we demonstrated that Helicobacter pylori maximally induced macrophage inflammatory protein-2 (MIP-2) and inducible nitric oxide synthase (iNOS) mRNA only in wild-type mice. MIP-2 and iNOS mRNA were also induced by H. pylori in GSM06 cells. Induction of cyclooxygenase 2 mRNA through IFN-gamma was demonstrated in GSM06 cells. These data indicate that IFN-gamma mediates the induction of MIP-2 and iNOS mRNA expression by H. pylori in mice.     

Regulation of Trypanosoma cruzi infection in mice by gamma interferon and interleukin 10: role of NK cells.

Gamma interferon (IFN-gamma) plays an important role in experimental Trypanosoma cruzi infections, presumably by controlling the early replication of parasites in host macrophages. In this work, we show that NK cells represent an important cell type responsible for the production of most of the IFN-gamma in the early stage of T. cruzi infection and that the in vivo treatment of mice with anti-NK1.1 monoclonal antibody made resistant animals susceptible to the infection. Through in vitro experiments, we demonstrate that normal splenocytes from euthymic or athymic nude mice cultivated for 48 h with live T. cruzi trypomastigotes produced elevated levels of IFN-gamma. In addition, NK-depleted splenocytes show a drastic reduction of IFN-gamma production in response to live T. cruzi trypomastigotes. We also demonstrated that IFN-gamma production is dependent on a factor secreted by adherent cells. Supernatants of spleen cells from athymic nude mice are able to induce IFN-gamma production by normal splenocytes when cultured with trypomastigotes. The addition of anti-interleukin-10 to these cultures resulted in a marked increase in IFN-gamma production. On the other hand, the absence of NK cells led to an increased secretion of interleukin-10 upon in vitro stimulation with T. cruzi. Taken together, these results suggest that NK cells are the major source of IFN-gamma that could be involved in limiting the replication of T. cruzi in host macrophages during the early acute phase of the infection.     

Acute hepatic failure in IFN-gamma-deficient BALB/c mice after murine coronavirus infection

We previously showed that an intraperitoneal infection with mouse hepatitis virus (MHV) persists in interferon-gamma (IFN-gamma)-deficient C57BL/6 (B6-GKO) mice and results in subacute fatal peritonitis, which bears a resemblance to feline infectious peritonitis. To examine the role of other host factors in MHV infection in mice, IFN-gamma-deficient mice with a BALB/c background (BALB-GKO) were infected intraperitoneally with MHV and compared with B6-GKO mice. In contrast to B6-GKO mice, BALB-GKO mice died within 1 week due to acute hepatic failure. The viral titer of the liver in BALB-GKO mice was significantly higher than that in B6-GKO mice. All hepatocytes in BALB-GKO mice were necrotic at 5 days post-infection, which was clearly distinct from large but limited lesion in the liver from infected B6-GKO mice. The serum alanine aminotransferase activity of infected BALB-GKO mice were higher than that of B6-GKO mice and was paralleled with the severity of the pathological changes and viral titers in infected mice. Administration of exogenous IFN-gamma to BALB-GKO partially inhibited the acute death. These results indicate that BALB-GKO and B6-GKO mice clearly show different diseases following MHV infection, although wild type counterparts of both mice apparently showed the same clinical course after MHV infection.     

Prevention by gamma interferon of fatal infection with Listeria monocytogenes in mice treated with cyclosporin A.

The significance of interferons (IFNs) induced by Listeria monocytogenes in the antilisterial defense mechanism was studied in mice. Cyclosporin A (CsA) had no effect on IFN-alpha production that was induced in the bloodstream after intravenous infection of mice with L. monocytogenes, whereas IFN-gamma that was induced in the bloodstreams of control mice 6 h after stimulation with specific antigen in the late phase of infection was suppressed in CsA-treated mice, depending on the dose of the drug injected. The decrease in IFN-gamma production caused an increase in bacterial growth in the spleens and livers of CsA-treated mice. Furthermore, administration of a daily dose of CsA at 80 or 100 mg/kg of body weight resulted in fatal listeriosis, even though the dose was nonlethal for normal mice. The administration of recombinant murine IFN-gamma on day 0 of L. monocytogenes infection prevented CsA-treated mice from developing fatal listeriosis and restored their ability to produce IFN-gamma in the bloodstream, in response to specific antigen in the late phase of infection.     

Suppression of interferon gamma production in mice treated with carrageenan

Effects of carrageenan (CAR) treatment on the response of interferon (IFN) production in vivo and in vitro after stimulation with an IFN-gamma inducer, staphylococcal enterotoxin A (SEA), was investigated. The IFN-gamma production in mice stimulated with SEA was impaired after i.v. administration of a 20 mg/kg dose of CAR. Spleen cells (SC) from CAR-treated mice had decreased ability to produce IFN in vitro after stimulation with the same inducer. SC obtained from mice during the suppressive state inhibited IFN-gamma production when they were co-cultured with mononuclear cells prepared from spleens of untreated control mice. This suppressor cell activity could be removed from SC by an adherence technique to plastic surface. The SC with suppressor activity were not inactivated by treatments with monoclonal anti-Thy-1.2 antibody, anti-asialo GM1 antisera and anti-mouse immunoglobulin antisera followed by complement. The suppressive activity was detected in cell-free culture fluids of macrophage fractions containing suppressor cell activity. These results suggest that the decrease in IFN-gamma production in mice pretreated with CAR may associate with the presence of suppressor cells characterized to the monocyte/macrophage lineage.     

Endogenous gamma interferon, tumor necrosis factor, and interleukin-6 in Staphylococcus aureus infection in mice.

The production and roles of endogenous gamma interferon (IFN-gamma), tumor necrosis factor (TNF), and interleukin-6 (IL-6) in both lethal and nonlethal infections of Staphylococcus aureus were investigated in mice. In the case of nonlethal infection, although no bacteria were detected in the bloodstreams, bacteria that colonized and proliferated persistently for 3 weeks were found in the kidneys. All mice given lethal injections died within 7 days, and large numbers of bacteria were detected in the bloodstreams, spleens, and kidneys. The first peaks of IFN-gamma, TNF, and IL-6 were observed in the bloodstreams and spleens of the mice with nonlethal and lethal infections within 24 h. Thereafter, in the nonlethal cases, IFN-gamma, TNF, and IL-6 peaked again in the spleens and kidneys during the period of maximum growth of bacteria in the kidneys, although only IL-6 was detected in the sera. In contrast, in the case of lethal infection, the titers of IFN-gamma and IL-6 in the sera and TNF in the kidneys peaked before death. Effects of in vivo administration of monoclonal antibodies (MAbs) against IFN-gamma and TNF on the fates of S. aureus-infected mice were studied. In the nonlethal infections, anti-TNF alpha (anti-TNF-alpha) MAb-treated mice, but not anti-IFN-gamma MAb-treated mice, died as a result of worsening infection, suggesting that endogenous TNF plays a protective role in host resistance to S. aureus infection. In the mice that received lethal doses, injection of anti-TNF-alpha MAb accelerated death. However, although injection of anti-IFN-gamma MAb inhibited host resistance of the infected mice early in infection, most of the animals survived the lethal infection by injection of anti-IFN-gamma MAb, suggesting that endogenous IFN-gamma plays a detrimental role in S. aureus infection. Thus, this study demonstrated that IFN-gamma and TNF play different roles in S. aureus infection.     

Inhibition of Ehrlichia risticii infection in murine peritoneal macrophages by gamma interferon, a calcium ionophore, and concanavalin A

Ehrlichia risticii incubated with mouse peritoneal macrophages elicited with thioglycolate broth survived and replicated, thereby allowing examination of the effects of several immunopotentiating agents. Treatment of the macrophages with recombinant murine gamma interferon (rMuIFN-gamma) in vitro at 1 day before or 3 h after infection made the macrophages resistant to infection with E. risticii, and macrophages treated with rMuIFN-gamma at 1 to 3 days after infection developed the capacity to eradicate intracellular E. risticii. Similar effects were seen with macrophages treated with the Ca2+ ionophore A23187 before or after E. risticii infection in vitro. Concanavalin A treatment before or 3 h after infection caused the macrophages to become resistant to infection with E. risticii but could confer neither ehrlichiacidal nor ehrlichiastic activity to them once infection had been established for more than 1 day. Bacterial products such as lipopolysaccharide and muramyl dipeptide were less or not at all effective, respectively, in conferring antiehrlichial activity to macrophages. Finally, protein kinase C activator, phorbol myristate acetate, and recombinant tumor necrosis factor did not induce any antiehrlichial activity in macrophages when the macrophages were treated either before or after infection.     

Responses of mice to murine coronavirus immunization

Summary Oral and/or intranasal inoculation of susceptible mouse genotypes with the JHM strain of mouse hepatitis virus (MHV-JHM) consistently results in T cell dysfunction as reflected by in vitro proliferative responses to mitogens or allogeneic cells. One approach to examining the mechanism responsible for the observed functional T cell suppression is to determine whether virus replication is required for its induction. To this end, mice were inoculated oronasally with MHV-JHM that was inactivated with short-wave ultraviolet light, betapropiolactone or psoralen. Mice were also inoculated with live MHV-JHM after recovery from homotypic or heterotypic MHV infection. Spleen cells from BALB mice inoculated oronasally with inactivated MHV-JHM yielded extremely variable in vitro proliferative responses after concanavalin A stimulation. MHV-susceptible mice exposed oronasally or intraperitoneally to virus inactivated by any of the minimum effective treatments failed to seroconvert. Immunization with psoralen-treated virus intraperitoneally in Freund's complete adjuvant or oronasally failed to protect from live virus challenge, but survivors had elevated virus-specific serum IgG antibody titers compared to mock-immunized controls at two weeks post-challenge. Spleen cells from mice that were challenged after recovery from homotypic live virus infection did not exhibit the profound in vitro T cell suppression normally observed during the acute stage of primary infection. In contrast, MHV-JHM challenge of mice vaccinated with heterotypic live MHV-S resulted in significantly depressed in vitro T cell function. The combined data suggest that either virus replication or exposure to more concentrated antigen may be required for induction of the dramatic T cell dysfunction that occurs as a consequence of MHV-JHM infection as well as for a detectable MHV-specific humoral response.     

Effect of murine cytomegalovirus infection on mitogen responses in genetically resistant and susceptible mice.

Temperature-sensitive (ts) reassortant vaccine strains derived from the A/Udorn/72 ts-1A2 donor virus were not sufficiently stable genetically in humans. We therefore sought to produce a new, more stable donor virus. We had previously identified a stable ts virus with a ts P3 gene and in the current study identified another relatively stable single-lesion ts virus with a ts mutation in the NP gene. A new ts reassortant virus was constructed by mating these two single mutants and by isolating three reassortant progeny, clones 20, 53, and 55, that contained both a ts P3 and a ts NP gene. These reassortant progeny possessed a 37 to 38°C shutoff temperature and were as restricted in their replication in hamster lungs as the A/Udorn/72 ts-1A2 virus. All isolates from the lungs and nasal turbinates of hamsters were temperature sensitive. An in vitro stress test was used to determine whether the new ts P3 ts NP reassortant virus would undergo loss of its ts phenotype after replication at semipermissive temperature. Clone 20 and 55 reassortants underwent progressive loss of their ts phenotype in vitro, although at a rate slightly less than that of the A/Udorn/72 ts-1A2 virus. The level of genetic stability after replication in vivo was assessed in cyclophosphamide-treated hamsters in which virus replication continued for up to 15 days. Again, both the A/Udorn/72 ts-1A2 and the new ts P3 ts NP reassortant clone 55 manifested a progressive loss of temperature sensitivity after 7 days of replication. Clone 55 virus lost temperature sensitivity significantly less rapidly than the A/Udorn/72 ts-1A2 virus. These results indicated that, although the new ts P3 ts NP reassortant virus was more stable than the A/Udorn/72 ts-1A2 virus, it nevertheless underwent progressive loss of temperature sensitivity after replication in vitro and in vivo. Therefore, it does not appear to be a satisfactory donor virus. This experience plus that gained earlier with other ts mutants of influenza A virus suggest that influenza A virus mutants that rely solely upon their ts phenotype for attenuation are unlikely to exhibit the phenotypic stability required of a vaccine virus. Other genetic techniques are needed to produce more stable influenza A virus strains.     

The inflammatory macrophage response to murine cytomegalovirus in genetically susceptible mice

Summary Adherent suppressor cells have often been implicated in the depression of immunocompetence following CMV infections. We have reported that high levels of cytostatic macrophages in the peritoneal cavities of infected mice correlate with genetically-based sensitivity to CMV disease, suggesting they may modulate protective immune responses. This study investigates the properties and kinetics of such cells.Genetically-susceptible BALB/c mice infected with MCMV accumulated activated peritoneal macrophages, 7 days post-infection. These cells suppressed³H-thymidine-incorporation and lymphokine production in syngeneic lymphocyte cultures and hence appeared to have depressed accessory cell function, although interleukin-1 production and the capacity to take up colloidal gold were enhanced. The cytostatic activity was located in a low density fraction (1.05 g/ml), which was expanded by MCMV infection. The lowest density cells had higher frequencies of infection but the proportion of cells releasing virus (<0.2%) was below the proportion activated, as shown by the shift in the density profile or enhanced colloidal gold uptake.A comparable accumulation of cytostatic activated peritoneal macrophages occurred in mice treated with cyclosporine A, but nude mice showed macrophage activation without cytostasis, so the role of T cells is not resolved.The spleens of infected mice maintaining high level of virus in this organ atrophied, and the remaining cells were unable to proliferate in culture. In contrast, mice clearing the virus developed splenomegaly and restricted responsiveness, which may be governed by cytostatic cells equivalent to those in the peritoneal cavity. The spread of virus to the lymph nodes was limited and MCMV-primed cells were readily demonstrable.     

Role of gamma interferon inToxoplasma gondii infection

Toxoplasma gondii has emerged as an important pathogen in the ever increasing numbers of patients with disorders of the immune system. Better understanding of the mechanisms of resistance of the host against this protozoan is important for development of safe, effective alternative treatment regimens for toxoplasmosis. Gamma interferon is the cytokine that plays a central role in protection againstToxoplasma gondii. The purpose of this review is to highlight the current knowledge of the role of gamma interferon inToxoplasma gondii infection.