Dominant antibody responses to Fucα1-3GalNAc and Fucα1-2Fucα1-3GlcNAc containing carbohydrate epitopes in Pan troglodytes vaccinated and infected with Schistosoma mansoni

The development of the humoral anti-glycan immune response of chimpanzees, either or not vaccinated with radiation-attenuated Schistosoma mansoni cercariae, was followed during 1 year after infection with S. mansoni. During the acute phase of infection both the vaccinated and the control chimpanzees produce high levels of immunoglobulin G (IgG) antibodies against carbohydrate structures that are characteristic for schistosomes carrying the Fucalpha1-3GalNAc and Fucalpha1-2Fucalpha1-3GlcNAc motifs, but not to the more widespread occurring structures GalNAcbeta1-4GlcNAc, GalNAcbeta1-4(Fucalpha1-3)GlcNAc, and Galbeta1-4(Fucalpha1-3)GlcNAc (Lewis(x)). In addition, high levels of IgM antibodies were found against the trimeric Lewis(x) epitope. Apparently, the schistosome-characteristic carbohydrate structures are dominant epitopes in the anti-glycan humoral immune response of the chimpanzees. All chimpanzees showed an increase in the level of antibodies against most of the carbohydrate structures tested directly after vaccination, peaking at challenge time and during the acute phase of infection. With the exception of anti-F-LDN antibody responses, the anti-carbohydrate antibody responses upon schistosome infection of the vaccinated animals were muted in comparison to the control animals.

Divergent effect of bacillus Calmette-Guérin (BCG) vaccination on Mycobacterium tuberculosis infection in highly related macaque species: implications for primate models in tuberculosis vaccine research

Despite the widespread use of bacillus Calmette-Guérin vaccination, Mycobacterium tuberculosis infection remains globally the leading cause of death from a single infectious disease. The complicated and often protracted dynamics of infection and disease make clinical trials to test new tuberculosis vaccines extremely complex. Preclinical selection of only the most promising candidates is therefore essential. Because macaque monkeys develop a disease very similar to humans, they have potential to provide important information in addition to small animal models. To assess the relative merits of rhesus and cynomolgus monkeys as screens for tuberculosis vaccines, we compared the efficacy of bacillus Calmette-Guérin vaccination and the course of infection in both species. Unvaccinated rhesus and cynomolgus monkeys both developed progressive disease with high levels of C-reactive protein, M. tuberculosis-specific IgG, and extensive pathology including cavitation and caseous necrosis. Bacillus Calmette-Guérin vaccination protected cynomolgus almost completely toward the development of pathology, reflected in a striking 2-log reduction in viable bacteria in the lungs compared with nonvaccinated animals. Rhesus, on the other hand, were not protected efficiently by the bacillus Calmette-Guérin. The vaccinated animals developed substantial pathology and had negligible reductions of colony-forming units in the lungs. Comparative studies in these closely related species are likely to provide insight into mechanisms involved in protection against tuberculosis.

A prime-boost immunisation regimen using DNA followed by recombinant modified vaccinia virus Ankara induces strong cellular immune responses against the Plasmodium falciparum TRAP antigen in chimpanzees

Two chimpanzees were vaccinated intramuscularly against malaria using plasmid DNA expressing the pre-erythrocytic antigens thrombospondin related adhesion protein (PfTRAP) and liver stage specific antigen-1 (PfLSA-1) of Plasmodium falciparum together with GM-CSF protein. A recombinant modified vaccinia virus Ankara (MVA) expressing PfTRAP was injected intramuscularly 6 weeks later to boost the immune response. This sequence of antigen delivery induced a specific and long-lasting T cell and antibody response to PfTRAP as detected by ELISPOT assay and ELISA. Antibody responses were detected after four DNA injections, and were boosted by injection of recombinant MVA expressing PfTRAP. Interferon-gamma secreting antigen-specific T cells were detected in both animals, but only after boosting with recombinant MVA. By screening a panel of PfTRAP-derived peptides, an epitope was identified that was recognized by cytotoxic T lymphocytes in one of the chimpanzees studied. T cells specific for this epitope were present in PBMCs and liver-infiltrating lymphocytes at a frequency of between 1 in 200 and 1 in 500. The high immunogenicity of this prime-boost regimen in chimpanzees supports further assessment of this delivery strategy for the induction of protection against P. falciparum malaria in humans.

Cellular and humoral immune responses and protection against schistosomes induced by a radiation-attenuated vaccine in chimpanzees

The radiation-attenuated Schistosoma mansoni vaccine is highly effective in rodents and primates but has never been tested in humans, primarily for safety reasons. To strengthen its status as a paradigm for a human recombinant antigen vaccine, we have undertaken a small-scale vaccination and challenge experiment in chimpanzees (Pan troglodytes). Immunological, clinical, and parasitological parameters were measured in three animals after multiple vaccinations, together with three controls, during the acute and chronic stages of challenge infection up to chemotherapeutic cure. Vaccination induced a strong in vitro proliferative response and early gamma interferon production, but type 2 cytokines were dominant by the time of challenge. The controls showed little response to challenge infection before the acute stage of the disease, initiated by egg deposition. In contrast, the responses of vaccinated animals were muted throughout the challenge period. Vaccination also induced parasite-specific immunoglobulin M (IgM) and IgG, which reached high levels at the time of challenge, while in control animals levels did not rise markedly before egg deposition. The protective effects of vaccination were manifested as an amelioration of acute disease and overall morbidity, revealed by differences in gamma-glutamyl transferase level, leukocytosis, eosinophilia, and hematocrit. Moreover, vaccinated chimpanzees had a 46% lower level of circulating cathodic antigen and a 38% reduction in fecal egg output, compared to controls, during the chronic phase of infection.

Interleukin-10 regulates the tissue factor activity of monocytes in an in vitro model of bacterial endocarditis

Monocytes are important effector cells in the pathogenesis of bacterial endocarditis since they provide the tissue factor that activates the coagulation system and maintains established vegetations. Monocytes secrete cytokines that can modulate monocyte tissue factor activity (TFA), thereby affecting the formation and maintenance of vegetations. In this study, we show that monocytes cultured for 4 h on a Streptococcus sanguis-infected fibrin matrix mimicking the in vivo vegetational surface express high levels of TFA. This was accompanied by secretion of the proinflammatory cytokines tumor necrosis factor alpha (TNF-alpha), interleukin-1 alpha (IL-1 alpha), and IL-1 beta. After a 24-h incubation period the anti-inflammatory cytokine IL-10 could also be detected. Our data show that, whereas TNF-alpha and IL-1 have a minor role in the induction of TFA by monocytes cultured on a fibrin matrix, TNF-alpha but not IL-1 plays an important role in the induction of IL-10 by these cells. In turn, our data show that IL-10 is an important factor in the downregulation of monocyte TFA. In summary, we conclude that IL-10 is an important factor in the control of monocyte TFA in endocardial vegetations.

Antibodies to glycans dominate the host response to schistosome larvae and eggs: is their role protective or subversive?

Multiple exposures of chimpanzees to the radiation-attenuated schistosome vaccine provoked a strong parasite-specific cellular and humoral immune response. Specific IgM and IgG were directed mainly against glycans on antigens released by cercariae; these were also cross-reactive with soluble antigens from larvae, adult worms, and eggs. Egg deposition was the major antigenic stimulus after challenge of vaccinated and control chimpanzees with normal parasites, eliciting strong antiglycan responses to egg secretions. Glycan epitopes recognized included LacdiNAc, fucosylated LacdiNAc, Lewis(X) (weakly), and those on keyhole limpet hemocyanin. Antibodies to peptide epitopes became prominent only during the chronic phase of infection, as glycan-specific IgM and IgG decreased. Because of their intensity and cross-reactivity, the antiglycan responses resulting from infection could be a smoke screen to subvert the immune system away from more vulnerable larval peptide epitopes. Their occurrence in humans might explain the long time required for antischistosome immunity to build up after infection.

Transforming growth factor-beta suppresses interferon-gamma-induced toxoplasmastatic activity in murine macrophages by inhibition of tumour necrosis factor-alpha production

Activation of macrophages plays an important role in the host resistance against intracellular pathogens. Various mechanisms are employed to control the activation processes and limit tissue damage by factors produced by activated macrophages. One of these mechanisms is the production of macrophage-deactivating cytokines, such as tumour growth factor (TGF)-beta. The present study concerns the effects of TGF-beta on interferon (IFN)-gamma-induced activation of murine macrophages with respect to induction of toxoplasmastatic activity, and production of tumour necrosis factor (TNF)-alpha, prostaglandin E2 (PGE2) and reactive nitrogen intermediates (RNI). IFN-gamma activation of macrophages resulted in inhibition of T. gondii proliferation [mean fold increase (FI) = 1.8, control mean FI = 7.0]; polymyxin B had no effect on this activation. The IFN-gamma-induced toxoplasmastatic activity of macrophages was inhibited by TGF-beta (mean FI = 6.3), which was also found for the IFN-gamma-induced production of TNF-alpha, RNI and PGE2 by macrophages. We found that PGE2, which has macrophage deactivating properties, was not involved in the inhibition of macrophage activation by TGF-beta. The deactivating activities of TGF-beta on the IFN-gamma-induced toxoplasmastatic activity and production of RNI are mediated by inhibition of production of TNF-alpha. Addition of exogenous TNF-alpha during the incubation of macrophages with IFN-gamma and TGF-beta abrogated the deactivating activity of TGF-beta. In sum, the results demonstrate that inhibition of TNF-alpha production is a key factor in the TGF-beta-induced suppression of macrophage activation with respect to toxoplasmastatic activity and RNI production.

Reactivity of human T-lymphocyte-specific antibodies with peripheral blood mononuclear cells and spleen of Aotus azarae ssp. boliviensis (owl monkey)

Aotus monkeys offer one of the few models that can be used for the evaluation of the immunogenicity and efficacy of new vaccine candidates against the human malarias, Plasmodium falciparum and Plasmodium vivax. However, the tools available for evaluation of the immune responses in these New World primates are still limited. In the present study, a previously selected set of monoclonal antibodies that were raised against human T cell determinants and were reactive with at least one other primate species was investigated for its reactivity with Aotus lymphocytes using FACS analysis, indirect immunofluorescence (IFA) and immunohistochemistry. From a panel of 19 mAb, six were found to react consistently with Aotus lymphocytes using FACS analysis. Further evaluation of the mAb using IFA confirmed these findings. Analysis of the selected mAb on spleen sections of Aotus monkeys identified one anti-CD4 and one anti-CD8 mAb that can be used for immunohistochemical studies. The set of mAb identified in this study can be used for the detection of various T lymphocyte markers in peripheral blood and in tissues of Aotus monkeys. Together with data published by others, mAb are now identified for detection of six different markers of Aotus T lymphocytes. These mAb are very valuable for the characterisation of immune responses after vaccination and infection in the Aotus malaria models.

Protection against Plasmodium falciparum malaria in chimpanzees by immunization with the conserved pre-erythrocytic liver-stage antigen 3

In humans, sterile immunity against malaria can be consistently induced through exposure to the bites of thousands of irradiated infected mosquitoes. The same level of protection has yet to be achieved using subunit vaccines. Recent studies have indicated an essential function for intrahepatic parasites, the stage after the mosquito bite, and thus for antigens expressed during this stage. We report here the identification of liver-stage antigen 3, which is expressed both in the mosquito and liver-stage parasites. This Plasmodium falciparum 200-kilodalton protein is highly conserved, and showed promising antigenic and immunogenic properties. In chimpanzees (Pan troglodytes), the primates most closely related to humans and that share a similar susceptibility to P. falciparum liver-stage infection, immunization with LSA-3 induced protection against successive heterologous challenges with large numbers of P. falciparum sporozoites.

Infection of a canine macrophage cell line with leishmania infantum: determination of nitric oxide production and anti-leishmanial activity

We have previously shown that resistance to Leishmania infantum in dogs is associated with a Th1 type of immune response. In this study, we use a canine macrophage cell line (030-D) that can readily be infected with this protozoan parasite. Our aim is to further characterize the effector mechanisms involved in killing of Leishmania parasite in dogs. We observed that activation of 030-D cells by incubation with a supernatant derived from a Leishmania-specific T cell line containing IFN-gamma, TNF-alpha and interleukin-2 (IL-2) resulted in enhanced nitric oxide (NO) production by these cells. In addition, we observed enhanced anti-leishmanial activity of infected 030-cells after activation. Both, NO production and anti-leishmanial activity were abrogated by addition of L-N(G)-nitroargininemethyl ester (L-NAME), an analogue of L-arginine. Thus, NO play an important role in the anti-leishmanial activity of these canine macrophages. We propose the infection of the 030-D cell line as a good in vitro model to further investigate parasite-host cell interactions in dogs, a natural host of Leishmania parasites.

Expression of beta-defensin-1 in chimpanzee (Pan troglodytes) airways

In human airways, beta-defensins function in the elimination of various pathogens. They have been identified in a wide range of species. Here we report the identification and expression of chimpanzee beta-defensin-1 (cBD1), which is a homolog of human beta-defensin-1, in chimpanzee airways and skin. The cBD1 cDNA sequence differs by only one synonymous nucleotide substitution compared to the human cDNA sequence. In situ hybridization revealed that in lung tissue beside alveolar macrophages also airway epithelial cells, endothelial cells and type II pneumocytes express cBD1 mRNA. In skin, cBD1 mRNA was expressed in keratinocytes and endothelial cells. Together, these results show similarity in structure and expression pattern and perhaps in function.

Interleukin-10 has different effects on proliferation of Listeria monocytogenes in livers and spleens of mice

The aim of this study was to investigate the effect of interleukin-10 (IL-10) on the course of Listeria monocytogenes infection in naive and immune mice. Treatment with IL-10 during the course of a primary infection significantly decreased the number of bacteria in the spleen and did not affect the number in the liver. During a secondary infection in immune mice treated with IL-10, the number of bacteria was significantly lower in the spleen but significantly higher in the liver in comparison to mock-treated immune mice. IL-10 treatment during a primary Listeria infection decreased the concentration of gamma interferon (IFN-gamma) in plasma and the toxoplasmastatic activity of macrophages, whereas it increased the percentage of mildly CD3-positive T cells in the spleen. During a secondary infection, the concentration of IFN-gamma in plasma was decreased on day 1 but remained unaffected during later days of infection. From these results, we conclude that IL-10 has different effects on the proliferation of L. monocytogenes in the spleen and liver during primary and secondary Listeria infections.

Different effect of granulocyte colony-stimulating factor or bacterial infection on bone-marrow cells of cyclophosphamide-treated or irradiated mice

In the present study, the effect of treatment with granulocyte colony-stimulating factor (G-CSF) on cellular composition of the bone marrow and the number of circulating leucocytes of granulocytopenic mice, whether or not infected with Staphylococcus aureus, was assessed. With two monoclonal antibodies, six morphologically distinct cell populations in the bone marrow could be characterised and quantitated by two-dimensional flow cytometry. Granulocytopenia was induced by cyclophosphamide or sublethal irradiation. Cyclophosphamide predominantly affected the later stages of dividing cells in the bone marrow resulting in a decrease in number of granulocytic cells, monocytic cells, lymphoid cells and myeloid blasts. G-CSF administration to cyclophosphamide-treated mice increased the number of early blasts, myeloid blasts and granulocytic cells in the bone marrow, which indicates that this growth factor stimulates the proliferation of these cells in the bone marrow. During infection in cyclophosphamide-treated mice the number of myeloid blasts increased. However, when an infection was induced in cyclophosphamide and G-CSF-treated mice, the proliferation of bone-marrow cells was not changed compared to that in noninfected similarly treated mice. Sublethal irradiation affected all bone-marrow cell populations, including the early blasts. G-CSF-treatment of irradiated mice increased only the number of myeloid blasts slightly, whereas an infection in irradiated mice, whether or not treated with G-CSF, did not affect the number of bone-marrow cells. Together, these studies demonstrated that irradiation affects the early blasts and myeloid blasts in the bone marrow more severely than treatment with cyclophosphamide. Irradiation probably depletes the bone marrow from G-CSF-responsive cells, while cyclophosphamide spared G-CSF responsive cells, thus enabling the enhanced G-CSF-mediated recovery after cyclophosphamide treatment. Only in these mice, bone marrow recovery is followed by a strong mobilisation of mature granulocytes and their band forms from the bone marrow into the circulation during a bacterial infection.

Anti-CD14 monoclonal antibodies inhibit the production of tumor necrosis factor alpha and interleukin-10 by human monocytes stimulated with killed and live Haemophilus influenzae or Streptococcus pneumoniae organisms

In previous studies, we have shown that intact, heat-killed, gram-negative bacteria (GNB) and gram-positive bacteria (GPB) can stimulate the production of various proinflammatory and anti-inflammatory cytokines. The objective of the present study was to investigate whether the production of tumor necrosis factor alpha (TNF) and interleukin-10 (IL-10) by human monocytes stimulated by intact heat-killed or live Haemophilus influenzae or Streptococcus pneumoniae is mediated by CD14. Two anti-CD14 monoclonal antibodies (MAbs) were used to study the interaction between human monocytes and bacteria; lipopolysaccharide (LPS) was used to validate the effect of anti-CD14 MAb. MAb 18E12 decreased significantly TNF and IL-10 production upon stimulation with LPS or heat-killed bacteria and TNF production during stimulation by live bacteria. MAb My-4 decreased production of TNF and IL-10 by monocytes stimulated with LPS, IL-10 but not TNF production upon stimulation with heat-killed H. influenzae, and production of neither TNF nor IL-10 upon stimulation with S. pneumoniae. Together, these results led to the conclusion that CD14 is involved in the recognition and stimulation of human monocytes by intact GNB and GPB. Consequentially, the option for adjunctive treatment of severe infections with anti-CD14 MAb is postulated.

High-level expression of Plasmodium vivax apical membrane antigen 1 (AMA-1) in Pichia pastoris: strong immunogenicity in Macaca mulatta immunized with P. vivax AMA-1 and adjuvant SBAS2

The apical membrane antigen 1 (AMA-1) family is a promising family of malaria blood-stage vaccine candidates that have induced protection in rodent and nonhuman primate models of malaria. Correct conformation of the protein appears to be essential for the induction of parasite-inhibitory responses, and these responses appear to be primarily antibody mediated. Here we describe for the first time high-level secreted expression (over 50 mg/liter) of the Plasmodium vivax AMA-1 (PV66/AMA-1) ectodomain by using the methylotrophic yeast Pichia pastoris. To prevent nonnative glycosylation, a conservatively mutagenized PV66/AMA-1 gene (PV66Deltaglyc) lacking N-glycosylation sites was also developed. Expression of the PV66Deltaglyc ectodomain yielded similar levels of a homogeneous product that was nonglycosylated and was readily purified by ion-exchange and gel filtration chromatographies. Recombinant PV66Deltaglyc43-487 was reactive with conformation-dependent monoclonal antibodies. With the SBAS2 adjuvant, Pichia-expressed PV66Deltaglyc43-487 was highly immunogenic in five rhesus monkeys, inducing immunoglobulin G enzyme-linked immunosorbent assay titers in excess of 1:200,000. This group of monkeys had a weak trend showing lower cumulative parasite loads following a Plasmodium cynomolgi infection than in the control group.

Endogenous interleukin-4 does not suppress the resistance against a primary or a secondary Listeria monocytogenes infection in mice

Interleukin-4 (IL-4), a cytokine produced by T-helper 2 (Th2) cells, can inhibit the development of T-helper 1 (Th1) cells, which results in a decreased release of cytokines by the latter. As interferon-gamma (IFN-gamma), produced by Th1 cells, is involved in the resistance against a Listeria monocytogenes infection, the role of endogenously formed IL-4 during a Listeria infection in mice was investigated. Neutralization of endogenously formed cytokines by subcutaneously injected alginate-encapsulated monoclonal antibody (MoAb)-forming cells results in high antibody titres in the circulation over a long time period. The aim of the present study was to reevaluate the effect of neutralization of IL-4 during a primary Listeria infection and to investigate the role of IL-4 during a secondary infection in mice using encapsulated MoAb-forming cells. During the course of a primary infection in mice given anti-IL-4 antibody-forming cells (anti-IL-4-FC), the number of Listeria found in the liver and spleen was comparable to that found in control mice given anti-beta-galactosidase antibody-forming cells (anti-beta-gal-FC). Activation of macrophages measured by inhibition of Toxoplasma gondii proliferation and the release of reactive nitrogen intermediates (RNI) was not affected by anti-IL-4-FC treatment during infection. Furthermore, during a secondary L. monocytogenes infection the number of bacteria in the liver and spleen of anti-IL-4-treated immune mice was comparable to anti-beta-gal-FC-treated, control, immune mice. The concentration of IFN-gamma in plasma of anti-IL-4-treated immune mice was similar to that of control immune mice. Taken together, these findings demonstrate that neutralization of endogenously formed IL-4 does not affect resistance to a primary or a secondary L. monocytogenes infection in mice.

Effect of granulocyte-macrophage colony-stimulating factor on the number of leucocytes and course of Listeria monocytogenes infection in naive and leucocytopenic mice

This study concerns the effect of recombinant murine granulocyte-macrophage colony-stimulating factor (GM-CSF) on the number of circulating leucocytes, activation of peritoneal macrophages and proliferation of Listeria monocytogenes in various organs of naive and leucocytopenic mice. Mice were rendered leucocytopenic by sublethal total body irradiation or cyclophosphamide treatment. GM-CSF treatment enhanced the number of granulocytes and monocytes in peripheral blood during L. monocytogenes infection in naive mice, but not in irradiated or cyclophosphamide-treated mice. In naive mice, irradiated and cyclophosphamide-treated mice, GM-CSF did not affect the course of L. monocytogenes infection in thigh muscle, spleen and liver. However, GM-CSF treatment significantly increased the number of macrophages in the peritoneal cavity of naive mice during infection; these macrophages were more enlarged and showed a higher frequency of binucleated and multinucleated cells relative to non-GM-CSF-treated mice. Together, these results demonstrated that GM-CSF increased the number of circulating granulocytes and monocytes, and the number of peritoneal macrophages during infection with L. monocytogenes in naive mice, but did not affect the course of the infection in thigh muscle, spleen or liver of these mice. In leucocytopenic mice, however, GM-CSF did not affect the number of circulating phagocytes, which explains that this factor had no effect on the proliferation of the bacteria in the various organs.

Difference in binding of killed and live Streptococcus pneumoniae serotypes by C-reactive protein

The binding and opsonic properties of C-reactive protein (CRP) for various species of bacteria were investigated. CRP bound more avidly to killed than to live Streptococcus pneumoniae, the binding varying among various serotypes; CRP hardly bound to a number of other bacterial species studied. CRP enhanced complement-dependent phagocytosis of live S. pneumoniae by granulocytes but did not enhance the phagocytosis of live Staphylococcus aureus or group B streptococci. We suppose that CRP may serve as an opsonin for killed bacteria and bacterial debris but is probably not an important opsonin for live bacteria other than S. pneumoniae.

Increased intracellular survival of Mycobacterium smegmatis containing the Mycobacterium leprae thioredoxin-thioredoxin reductase gene

The thioredoxin (Trx) system of Mycobacterium leprae is expressed as a single hybrid protein containing thioredoxin reductase (TR) at its N terminus and Trx at its C terminus. This hybrid Trx system is unique to M. leprae, since in all other organisms studied to date, including other mycobacteria, both TR and Trx are expressed as two separate proteins. Because Trx has been shown to scavenge reactive oxygen species, we have investigated whether the TR-Trx gene product can inhibit oxygen-dependent killing of mycobacteria by human mononuclear phagocytes and as such could contribute to mycobacterial virulence. The gene encoding M. leprae TR-Trx was cloned into the apathogenic, fast-growing bacterium Mycobacterium smegmatis. Recombinant M. smegmatis containing the gene encoding TR-Trx was killed to a significantly lesser extent than M. smegmatis containing the identical vector with either no insert or a control M. leprae construct unrelated to TR-Trx. Upon phagocytosis, M. smegmatis was shown to be killed predominantly by oxygen-dependent macrophage-killing mechanisms. Coinfection of M. smegmatis expressing the gene encoding TR-Trx together with Staphylococcus aureus, which is known to be killed via oxygen-dependent microbicidal mechanisms, revealed that the TR-Trx gene product interferes with the intracellular killing of this bacterium. A similar coinfection with Streptococcus pyogenes, known to be killed by oxygen-independent mechanisms, showed that the TR-Trx gene product did not influence the oxygen-independent killing pathway. The data obtained in this study suggest that the Trx system of M. leprae can inhibit oxygen-dependent killing of intracellular bacteria and thus may represent one of the mechanisms by which M. leprae can deal with oxidative stress within human mononuclear phagocytes.

Flow cytometric analysis on reactivity of human T lymphocyte-specific and cytokine-receptor-specific antibodies with peripheral blood mononuclear cells of chimpanzee (Pan troglodytes), rhesus macaque (Macaca mulatta), and squirrel monkey (Saimiri sciureus)

There are relatively few monoclonal antibodies (mAb) that have been characterized for their applicability in studies on the immune system of various nonhuman primates. In the present study, we identified a large number of mAb that can be used in future immunological studies in three different nonhuman primates, i.e., chimpanzees, rhesus macaques, and squirrel monkeys. The reactivity of 161 anti-human mAb to T-cell antigens and cytokine receptors were tested on peripheral blood mononuclear cells (PBMC) from the three primate species by flow cytometric analysis. A total of 105 (65%), 73 (45%), and 68 (42%) antibodies reacted with PBMC from chimpanzees, rhesus macaques, and squirrel monkeys, respectively. Out of the 161 mAb, 38 reacted with all three species and 112 reacted with one or two of the species. No specific reaction was observed with mAb to receptors to GM-CSF, 4-1BB, FLT3, FLX2, common beta-chain, IL-1 (type I receptor), and IL-8.

Effect of lisofylline and pentoxifylline on the bacterial-stimulated production of TNF-alpha, IL-1 beta IL-10 by human leucocytes

The present study concerns the effect of the xanthine derivates lisofylline (LSF) and pentoxifylline (PTX) on the production of pro-inflammatory cytokines tumour-necrosis factor-alpha (TNF-alpha) and interleukin-1 beta (IL-1 beta) and the de-activating cytokine interleukin-10 (IL-10) by human leucocytes during stimulation with lipopolysaccharide (LPS), heat-killed Gram-negative bacteria (GNB) or Gram-positive bacteria (GPB). The production of TNF-alpha and IL-1 beta by leucocytes stimulated with LPS, Haemophilus influenzae type b (Hib) or Streptococcus pneumoniae was inhibited by both drugs. The production of IL-10 by leucocytes stimulated with LPS and Hib was inhibited by both xanthine derivates only at 48 hr. However, incubation of leucocytes with S. pneumoniae in the presence of LSF or PTX stimulated the production of IL-10 about four- and twofold at 24 hr and 48 hr, respectively. In all instances, the extent of inhibition or enhancement of cytokine production by LSF or PTX was equal. The divergent effects of xanthine derivates on the IL-10 production indicate the existence of distinct intracellular pathways depending on whether leucocytes are stimulated by GPB or GNB.

Elimination of resident macrophages from the livers and spleens of immune mice impairs acquired resistance against a secondary Listeria monocytogenes infection

During a secondary Listeria monocytogenes infection in mice, the bacteria are eliminated more rapidly from the liver and spleen than during a primary infection. This acquired resistance against a secondary infection is dependent on T lymphocytes, which induce enhanced elimination of bacteria via stimulation of effector cells such as neutrophils, resident macrophages, exudate macrophages, and hepatocytes. The aim of the present study was to determine the role of the resident macrophages in acquired resistance against a secondary L. monocytogenes infection in mice. Mice which had recovered from a sublethal primary infection with 0.1 50% lethal dose (LD50) of L. monocytogenes intravenously (i.v.), i.e., immune mice, received a challenge of 1 LD50 of L. monocytogenes i.v. to induce a secondary infection. At 2 days prior to challenge, immune mice were given an i.v. injection of liposomes containing dichloromethylene-diphosphonate (L-Cl2MDP) to selectively eliminate resident macrophages from the liver and spleen. Control immune mice received either phosphate-buffered saline (PBS) or liposomes containing PBS (L-PBS). Treatment of mice with L-Cl2MDP effectively eliminated resident macrophages from the liver and spleen but did not affect the number of granulocytes, monocytes, or lymphocytes in peripheral blood or their migration to a site of inflammation. Phagocytosis and killing of L. monocytogenes by peritoneal exudate cells elicited with heat-killed L. monocytogenes were similar in all groups of immune mice. On day 3 of a secondary infection, the number of L. monocytogenes organisms in the livers and spleens of L-Cl2MDP-treated immune mice was 4 log10 units higher than in immune mice treated with PBS or L-PBS. The concentration of reactive nitrogen intermediates in plasma, a measure of the severity of infection, was 70-fold higher for L-Cl2MDP-treated immune mice than for PBS- or L-PBS-treated immune mice. Treatment with L-Cl2MDP significantly increased the number of inflammatory foci in the liver and spleen, decreased their size, and affected their structure. From these results, we conclude that resident macrophages are required for the expression of acquired resistance against a secondary L. monocytogenes infection in mice.

TNF-alpha promoter polymorphisms, production and susceptibility to multiple sclerosis in different groups of patients

TNF-alpha production in whole blood cultures upon stimulation with LPS was determined in 179 individuals from 61 families in order to characterise the magnitude of inherited differences in TNF-alpha production. The three families characterised by highest TNF production showed 7.1 +/- 0.3 ng TNF/ml upon culture with 10 ng LPS and 10.2 +/- 0.2 ng TNF/ml upon culture with 1000 ng LPS. in contrast to the three families characterised by the lowest TNF production that showed a production of 1.6 +/- 0.1 ng TNF upon culture with 10 ng and 2.5 +/- 0.2 ng/ml upon culture with 1000 ng LPS/ml. This difference could not be attributed to the promoter polymorphisms -308 G to A. -238 G to A or -376 G to A, although the -238 GA donors produced 2.1 +/- 0.9 ng TNF upon culture with 10 ng endotoxin compared to 3.2 +/- 2.2 ng TNF for the -238 GG donors. In line with these results the frequency of the -238 GG genotype was increased in hospitalized MS patients in a nursing home (100% 238GG, n = 57) compared to MS patients in an outpatient's clinic (94% 238GG, n = 98) or Dutch controls (90% 238GG, n = 180). These results suggest that the -238 GG genotype is differently distributed in hospitalized MS patients in a nursing home.

Relation between pro- and anti-inflammatory cytokines and the production of nitric oxide (NO) in severe sepsis

The aim of the present study was to investigate the relationship between the levels of pro-inflammatory [interleukin 6 (IL-6), IL-8, tumour necrosis factor alpha (TNF-alpha)], anti-inflammatory cytokines [IL-10, soluble TNF receptor type I (TNFsrI), TNFsrII], and the production of nitric oxide (NO) during a 1-week period in 23 patients with severe sepsis. The highest levels of pro-inflammatory cytokines and nitrate, the stable metabolite of NO, were found during the first day after inclusion and gradually declined thereafter. Detectable levels of IL-10, TNFsrI and TNFsrII were present in all patients at study entry but did not significantly change during the study period [analysis of variance (MANOVA); P > 0.05]. Serum nitrate levels correlated significantly with both pro-inflammatory cytokines (IL-6, IL-8, TNF-alpha) as well as anti-inflammatory cytokines (IL-10, TNFsrI, TNFsrII). Serum nitrate levels over time were higher in patients with positive blood cultures (n = 4) (MANOVA; P < 0.005), as compared to patients without proven bacteraemia. These data support the concept of an acute phase of sepsis that is characterized by an excess of pro-inflammatory cytokines, while anti-inflammatory cytokines are predominantly present during the secondary phase. The present findings indicate that pro-inflammatory cytokines are related to the induction of excessive NO production during the first phase of sepsis and that reduction of NO production occurs during the secondary phase. This may suggest that anti-inflammatory cytokines are able to diminish the production of NO in patients with severe sepsis.

Genetic influence on cytokine production and fatal meningococcal disease

BACKGROUND

To assess the genetic influence on cytokine production and its contribution to fatal outcome, we determined the capacity to produce tumour necrosis factor-alpha (TNF alpha) and interleukin-10 (IL-10) in families of patients who had had meningococcal disease.

METHODS

We studied 190 first-degree relatives of 61 patients with meningococcal disease; we also studied 26 monozygotic twins. Production of cytokines was determined during endotoxin stimulation of whole-blood samples ex-vivo. Heritability was estimated in a pedigree-based maximum-likelihood model. DNA was typed for the G to A transition polymorphisms at position -308 and -238 in the TNF gene promoter.

FINDINGS

Heritability in monozygotic twins was 0.60 for the production of TNF and 0.75 for the production of IL-10. Families with low TNF production had a tenfold increased risk for fatal outcome (OR 8.9, 95% CI 1.8-45), whereas high IL-10 production increased the risk 20-fold (19.5, 2.3-165). Families with both characteristics had the greatest risk. The transition polymorphisms in the TNF gene promoter were not associated with outcome.

INTERPRETATION

Genetic factors substantially influence production of cytokines. An innate anti-inflammatory cytokine profile may contribute to fatal meningococcal disease.

Nitric oxide (NO) production correlates with renal insufficiency and multiple organ dysfunction syndrome in severe sepsis

OBJECTIVE

To investigate whether the production of nitric oxide (NO) relates to the development of renal insufficiency and multiple organ dysfunction syndrome (MODS) in patients with severe sepsis.

DESIGN

Prospective study in 23 patients with severe sepsis.

SETTING

Medical and surgical intensive care units (ICU) of three hospitals.

MEASUREMENTS AND RESULTS

Serum nitrate levels, as an indirect parameter of the production of NO in vivo, and scores for renal insufficiency and MODS were determined in patients with severe sepsis during a 1-week period after admission to the ICU. The highest serum nitrate levels were found at 4 h (mean 52 +/- 16 mumol/l) after entry into the study and the levels gradually declined thereafter. Patients with renal insufficiency had considerably higher serum nitrate levels during the study period that patients who did not develop renal sufficiency (MANOVA, p < 0.05). Serum nitrate levels correlated with scores for renal insufficiency (r = 0.60, p < 0.001), and far exceeded the levels that can be explained solely by reduced renal clearance of nitrate. Further analysis showed that serum nitrate levels significantly and positively correlated with scores for MODS (r = 0.44, p < 0.001).

CONCLUSION

Our results indicate that the production of NO correlates with renal insufficiency and MODS in patients with severe sepsis and that this reactive nitrogen intermediate could be involved in the pathogenesis of organ failure in these critically ill patients.

Effect of granulocyte colony-stimulating factor on the course of infection with gram-positive bacteria in mice during granulocytopenia induced by sublethal irradiation or cyclophosphamide

This study assesses the effect of granulocyte colony-stimulating factor (G-CSF) on the outcome of infection with Listeria monocytogenes or Staphylococcus aureus in mice during leukocytopenia induced by sublethal total body irradiation or cyclophosphamide treatment. The role of granulocytes during infection was assessed in the thigh muscle, spleen, and liver. G-CSF treatment in naive mice increased the number of blood granulocytes; upon infection, these numbers increased further, but G-CSF did not affect the outgrowth of bacteria in the tissues. Cyclophosphamide treatment and sublethal irradiation decreased the number of blood granulocytes, which was not affected by G-CSF treatment. However, during infection in cyclophosphamide-treated mice, G-CSF increased the number of granulocytes in the circulation and at the site of infection and decreased the number of bacteria in the tissues. Treatment with G-CSF did not affect the number of granulocytes or the course of infection in irradiated mice.

Safety evaluation of a polymerized hemoglobin solution in a murine infection model

Several investigators have observed that free hemoglobin may increase the mortality rate in experimental Escherichia coli peritonitis in animals. This effect is probably mediated by the heme moiety of hemoglobin, but the mechanism remains controversial. Free hemoglobin might impair neutrophil function, and it might serve as a source of iron, which is necessary for bacterial replication. Several modified hemoglobin solutions, developed as blood substitutes, are currently being tested in clinical studies, but concern exists that these solutions may have the potential to exacerbate a bacterial infection. At the Central Laboratory of the Netherlands Red Cross Blood Transfusion Service, a blood substitute based on modified hemoglobin (PolyHbXl) has been developed that has improved oxygen affinity and prolonged vascular retention. In the present study the potential risk of this solution on the promotion of infections has been evaluated. PolyHbXl was intravenously injected into mice in a clinically relevant dose of 1.5 gm/kg body weight 1 hour before intravenous administration of a sublethal number of Listeria monocytogenes, Salmonella typhimurium, E. coli, or Candida albicans organisms. PolyHbXl did not promote the proliferation of any of these microorganisms in the liver and spleen, nor did it lead to an increased mortality rate in the mice. Also, the in vitro proliferation of L. monocytogenes, S. typhimurium, and E. coli was not increased by PolyHbXl. In conclusion, PolyHbXl does not affect the course of infection with various microorganisms in mice, and no indication was found that this new blood substitute compromises the host defense against infections.

Acquired resistance against a secondary infection with Listeria monocytogenes in mice is not dependent on reactive nitrogen intermediates

During an infection, inflammatory mediators can induce the production of nitric oxide, a reactive nitrogen intermediate (RNI) which plays a role in antimicrobial activity against a wide variety of pathogens. In vitro experiments have shown that release of RNI by macrophages is mediated by tumor necrosis factor alpha (TNF). Since TNF is essential for acquired resistance during a secondary Listeria monocytogenes infection in mice, the aim of the present study was to determine whether RNI are also involved in the course of such an infection. Mice which had recovered from a sublethal primary infection with 0.1 50% lethal dose of (LD50) L. monocytogenes were infected intravenously with 10LD50 of L. monocytogenes. During a primary infection, the number of bacteria in the liver and spleen, as well as the concentration of RNI in plasma, increased. During a secondary infection, the number of bacteria in the liver and spleen decreased whereas no significant increase in the concentration of RNI in plasma was observed. Neutralization of endogenously produced TNF and gamma interferon by subcutaneous injection of alginate-encapsulated monoclonal antibody-forming cells during a secondary infection resulted in an increase in the number of bacteria in the liver and spleen an increase in the concentration of RNI in plasma. When the production of RNI was inhibited by treatment of mice with competitive NO-synthase inhibitor N omega-nitro-L-arginine methyl ester hydrochloride (L-Name) and an iota-arginine-deficient diet during a secondary infection, the proliferation of L. monocytogenes in the liver and spleen was not affected whereas the concentration of RNI in plasma of these mice was significantly reduced. Our findings that inhibition of RNI formation during a secondary infection does not affect the proliferation of L. monocytogenes in the liver and spleen and that enhanced elimination of bacteria from these organs is not accompanied by an increase in the concentration of RNI in plasma led to the conclusion that resistance against a secondary infection with L. monocytogenes is not dependent on RNI.

Effect of xanthine derivates and dexamethasone on Streptococcus pneumoniae-stimulated production of tumor necrosis factor alpha, interleukin-1 beta (IL-1 beta), and IL-10 by human leukocytes

The present study concerns the release of the proinflammatory cytokines interleukin-1 beta (IL-1 beta) and tumor necrosis factor alpha and of the anti-inflammatory cytokine IL-10 by human leukocytes in whole blood during stimulation with Streptococcus pneumoniae and the effects of various xanthine derivates, i.e., pentoxifylline (PTX), caffeine, and theofylline, and of dexamethasone (DXM). All three xanthine derivates and DXM inhibited the release of tumor necrosis factor alpha, PTX being the most effective. PTX, theofylline, and DXM inhibited the release of IL-1 beta, but caffeine did not affect IL-1 beta release. The release of IL-10 was significantly reduced by PTX at 24 h and by caffeine at 48 h, but DXM increased the release of this cytokine. In sum, the results of this study demonstrate that DXM inhibits only the release of proinflammatory cytokines but not of the anti-inflammatory cytokine IL-10 by human leukocytes, while PTX is the most potent inhibitor of both proinflammatory and anti-inflammatory cytokines.

Tumour necrosis factor, but not interferon-gamma, is essential for acquired resistance to Listeria monocytogenes during a secondary infection in mice

Mice with a secondary Listeria monocytogenes infection eliminate the bacteria much faster and more efficiently from their organs than mice with a primary infection. During the course of a secondary infection, serum concentrations of interferon-gamma (IFN-gamma) and tumour necrosis factor-alpha (TNF) are higher than during a primary infection. The aim of the present study was to determine whether these cytokines are involved in the acquired resistance to L. monocytogenes during a secondary infection in mice. In order to neutralize cytokines, alginate-encapsulated cells, which form anti-cytokine monoclonal antibodies, were injected into the nuchal region of mice during a Listeria infection. Mice recovered from a sublethal primary Listeria infection, which acquired cell-mediated immunity, received a subcutaneous injection of anti-IFN-gamma-forming cells, or anti-TNF-forming cells, and 4 days later received an intravenous injection with 10 50% lethal dose (LD50) L. monocytogenes. The number of bacteria recovered from the liver and spleen of immune mice treated with anti-IFN-gamma-forming cells was slightly larger (approximately 1 log10) than that found for immune mice treated with anti-beta-galactosidase-forming cells, called immune control mice. The organs of immune mice treated with anti-TNF-forming cells yielded significantly more (approximately 4 log10) bacteria than those of immune control mice, more than those of immune mice treated with anti-IFN-gamma-forming cells, and comparable numbers to those of non-immune mice. Taken together, these results demonstrate that TNF is essential in acquired resistance to L. monocytogenes during a secondary infection in mice, while IFN-gamma plays a minor role.

Mycobacterial 65-kilodalton heat shock protein induces tumor necrosis factor alpha and interleukin 6, reactive nitrogen intermediates, and toxoplasmastatic activity in murine peritoneal macrophages

The 65-kDa heat shock protein (Hsp65) is supposed to play a role in host defense against infections with various microbial pathogens and in autoimmune inflammatory disorders. These effects are thought to result mainly from an Hsp65-specific T-lymphocyte-mediated immune response that recognizes conserved epitopes. The aim of the present study was to assess whether mycobacterial Hsp65 has a direct effect on resident murine peritoneal macrophages, independent of Hsp65-sensitized T lymphocytes. Exposure of peritoneal macrophages from naive C57BL/6 mice to the mycobacterial Hsp65 in vitro induced an enhanced release of tumor necrosis factor alpha (TNF-alpha) and interleukin 6. These cells also produced large amounts of reactive nitrogen intermediates (RNI) and inhibited the intracellular proliferation of Toxoplasma gondii. Small amounts of gamma interferon acted synergistically with Hsp65. Thus, exposure of murine macrophages to Hsp65 results in activation of these cells. The acquisition of these characteristics by peritoneal macrophages occurred in the absence of sensitized T lymphocytes. Addition of anti-TNF-alpha antiserum resulted in an attenuation of the Hsp65-induced release of RNI and toxoplasmastatic activity, indicating that endogenous TNF-alpha is involved in the Hsp65-induced macrophage activation. The conclusion of this study is that in vitro exposure of peritoneal macrophages to the mycobacterial Hsp65 induces the release of proinflammatory cytokines and RNI and results in inhibition of the intracellular proliferation of T. gondii. These effects on murine macrophages occur independently of Hsp65-specific T lymphocytes. The proinflammatory effect of Hsp65 demonstrated in this study suggests that this heat shock protein may play a role in the initiation of inflammation that adds to a non-species-specific resistance in the early stages of infections.

High levels of interleukin 10 and tumor necrosis factor alpha in cerebrospinal fluid during the onset of bacterial meningitis

Since interleukin-10 (IL-10) controls the production of tumor necrosis factor alpha (TNF-alpha) and this latter cytokine has a deleterious effect on neuronal cells, we determined the levels of both cytokines in cerebrospinal fluid (CSF) from children with bacterial meningitis. High levels of IL-10 (1,164 pg/mL) and TNF-alpha (3,158 pg/mL) were detected in CSF from 10 children with meningitis, but these cytokines were not detectable in CSF from 12 controls. In vitro neutralization of IL-10 demonstrated that endogenously formed IL-10 is important for limiting the production of TNF-alpha by leukocytes. We assume that IL-10 in CSF will decrease the inflammatory reaction associated with meningitis and will result in the development of fewer sequelae because of its inhibitory effect on the production of TNF-alpha.

Release of tumor necrosis factor: an innate host characteristic that may contribute to the outcome of meningococcal disease

Tumor necrosis factor (TNF) plays a pivotal role in meningococcal disease. The TNF response to endotoxin, however, differs between individuals and can be determined in whole blood samples ex vivo. The release of TNF in whole blood samples from 50 survivors of meningococcal disease 6-58 months after hospital discharge was studied. The TNF response was higher in patients who had experienced a moderately severe disease course compared with patients with a mild course. The TNF response was low again in the survivors of fulminant disease, who on original hospital admission presented with risk factors exposing them to a high chance of mortality (50% overall). On admission, the patients who did not survive had initial TNF levels three times higher than those in survivors with a clinical disease presentation of similar severity. Overall interpretation of these findings is that the innate TNF response may contribute to the outcome of meningococcal disease.

Antimicrobial functions of mononuclear phagocytes

One of the major functions of mononuclear phagocytes, i.e., monocytes and macrophages, is the phagocytosis and killing of microorganisms. To obtain more insight into the pathogenesis of infectious diseases and to develop new therapies against these diseases, a better understanding of the antimicrobial mechanisms employed by mononuclear phagocytes is essential. The present review gives a short description of the mononuclear phagocyte system and summarizes various methods that are used to study the antimicrobial mechanisms of mononuclear phagocytes.

In vitro effect of dexamethasone, pentoxifylline, and anti-endotoxin monoclonal antibody on the release of proinflammatory mediators by human leukocytes stimulated with Haemophilus influenzae type B

The effects of dexamethasone, pentoxifylline, and MAb against endotoxin (HA-1A) on the release of various proinflammatory mediators, i.e. tumor necrosis factor-alpha (TNF), IL-1 beta, IL-8, and prostaglandin 2, by human leukocytes during stimulation with Haemophilus influenzae type B were studied. The results show that only monocytes, and thus neither lymphocytes nor granulocytes, release these mediators in response to H. influenzae. Dexamethasone inhibited the release of all of these mediators, whereas pentoxifylline only inhibited the release of TNF. HA-1A only reduced the release of IL-8 from adherent monocytes significantly and had no significant effect on the release of TNF, IL-1 beta, and prostaglandin E2. In whole blood, no significant effect of HA-1A on the release of TNF, IL-1 beta, IL-8, and prostaglandin E2 was found. In summary, the results of this study demonstrate that dexamethasone is the most potent inhibitor of the release of proinflammatory mediators by monocytes induced by H. influenzae type B.

Mycobacterial heat-shock protein 65 induces proinflammatory cytokines but does not activate human mononuclear phagocytes

The 65 kDa heat-shock protein (Hsp65), a well-conserved and immunodominant antigen which elicits a cellular and humoral immune response, may play a role in host defence against invading microorganisms and autoimmune disorders. The aim of the present study was to assess the effects of Hsp65 on the functional activities of human mononuclear phagocytes in the absence of lymphocytes. Incubation with Hsp65 resulted in an enhanced release of TNF-alpha and IL-1 beta by human monocytes and monocyte-derived macrophages (MDM). The amount of cytokines released by these cells in response to Hsp65 was similar to that released in response to IFN-gamma together with LPS. Incubation with ovalbumin did not stimulate the release of these cytokines. In vitro stimulation of monocytes with Hsp65 enhanced the membrane expression of complement receptor III but did not influence either the expression of Fc gamma-receptor I and HLA class-II antigens or the release of reactive oxygen intermediates. Therefore, Hsp65-stimulated monocytes cannot be considered to be activated according to classical criteria. The release of the proinflammatory cytokines TNF-alpha and IL-1 beta by human mononuclear phagocytes in response to Hsp65 indicates that this protein can contribute to both host defence and tissue damage in inflammatory lesions characterized by an abundant expression of Hsp65.

Granulocyte-macrophage colony-stimulating factor is not involved in production of reactive nitrogen intermediates by or toxoplasmastatic activity of gamma interferon-activated murine macrophages

The induction of reactive nitrogen intermediates (RNI) and toxoplasmastatic activity of murine macrophages by recombinant gamma interferon (rIFN-gamma) is mediated by an autocrine pathway involving tumor necrosis factor alpha (TNF-alpha). To investigate whether cytokines other than TNF-alpha play a role in the activation of these effector functions, granulocyte-macrophage colony-stimulating factor (GM-CSF) was studied. Recombinant GM-CSF (rGM-CSF) could stimulate peritoneal macrophages, since this cytokine stimulated the production of prostaglandin E2 by these cells. However, rGM-CSF did not induce either the release of RNI by or the toxoplasmastatic activity of macrophages. rGM-CSF in combination with various concentrations of rIFN-gamma did not enhance these effector functions more than rIFN-gamma alone. Furthermore, neutralization of endogenously produced GM-CSF by monoclonal antibodies did not affect the release of RNI by or the toxoplasmastatic activity of rIFN-gamma-activated macrophages. Together these results indicate that GM-CSF is not involved in RNI production by and toxoplasmastatic activity of IFN-gamma-activated murine macrophages.

Effect of IFN-gamma and endogenous TNF on the histopathological changes in the liver of Listeria monocytogenes-infected mice

During primary infection of mice with Listeria monocytogenes, the bacteria proliferate extensively in the liver resulting in the development of inflammatory lesions in this organ. In the present study, the effect of interferon-gamma (IFN-gamma) on the development of these lesions, and the involvement of endogenous tumour necrosis factor-alpha (TNF-alpha) in the IFN-gamma-induced effects were evaluated. During an infection of naive mice with L. monocytogenes, two types of inflammatory lesions in the liver could be distinguished: large necrotic lesions consisting of granulocytes and/or exudate macrophages and small lesions containing mainly mature macrophages, i.e. BM8-expressing cells. Necrotic lesions were characterized by the presence of CD11b-expressing cells and consisted mainly of granulocytes during days 1 and 2 of infection and thereafter of exudate macrophages. The lesions consisting of mature macrophages and lymphocytes were not associated with necrosis and were called granulomatous lesions. Some of the granulomatous lesions contained many cells that expressed Ia antigen, i.e. activated cells. Treatment of mice with recombinant (r)IFN-gamma before injection of L. monocytogenes resulted in a decrease in the number of necrotic lesions and an increase in the number of granulomatous lesions in the liver, which was accompanied by a reduced bacterial proliferation in the liver. The effect of rIFN-gamma on the development of the various types of inflammatory lesions in the liver during infection with L. monocytogenes was abrogated by anti-TNF-alpha antibody and this antibody abrogated the rIFN-gamma-induced reduction of bacterial proliferation in the liver as well. Together, the results demonstrate that endogenous TNF-alpha plays a key role in the effects of rIFN-gamma on the inflammatory response in the liver during an infection with L. monocytogenes.

Murine peritoneal macrophages activated by the mycobacterial 65-kilodalton heat shock protein express enhanced microbicidal activity in vitro

After an intraperitoneal (i.p.) injection of purified protein derivative, peritoneal macrophages from mice infected with Mycobacterium bovis bacillus Calmette-Guérin (BCG) show an enhanced respiratory burst, inhibit the intracellular proliferation of Toxoplasma gondii, and kill Listeria monocytogenes more efficiently than peritoneal macrophages from normal mice. One of the immunodominant antigens of Mycobacterium spp. is the 65-kDa heat shock protein (Hsp 65), and in the present study, we determined whether injection of this protein into mice leads to activation of their peritoneal macrophages. After an i.p. injection of Hsp 65, peritoneal macrophages from BCG-infected CBA/J mice also released more H2O2, inhibited the proliferation of T. gondii, and killed L. monocytogenes faster than peritoneal macrophages from normal mice, although Hsp 65 was less effective than purified protein derivative. When normal mice were injected with Hsp 65 suspended in saline after a booster injection with Hsp 65, their macrophages did not display enhanced antimicrobial activity, indicating that an adjuvant was required for a cellular immune response against Hsp 65. In the present study, the adjuvant dimethyl dioctadecylammonium bromide (DDA) was preferred because it contains no endotoxin or mycobacterial antigens and because it has been reported that DDA does not induce the production of gamma interferon. Peritoneal macrophages from C57BL/6 and CBA/J mice that had received a subcutaneous injection of Hsp 65 suspended in DDA followed by an i.p. booster injection of Hsp 65 suspended in saline were activated, as indicated by the enhanced production of H2O2, inhibition of the intracellular proliferation of T. gondii, and increased rate of intracellular killing of L. monocytogenes in vitro relative to that by resident peritoneal macrophages and peritoneal macrophages obtained from mice that had received ovalbumin instead of Hsp 65. The rate of phagocytosis of L. monocytogenes was not affected by Hsp 65 treatment. Despite the in vitro expression of enhanced microbicidal activity of peritoneal macrophages, no difference in the growth of L. monocytogenes in the liver and spleen between Hsp 65-treated and control mice was found.

Endogenous tumor necrosis factor alpha is required for enhanced antimicrobial activity against Toxoplasma gondii and Listeria monocytogenes in recombinant gamma interferon-treated mice

In vitro studies have shown that macrophages stimulated with recombinant gamma interferon (rIFN-gamma) produce tumor necrosis factor alpha (TNF-alpha), which in an autocrine fashion activates these cells. The aim of the present study was to determine whether endogenously formed TNF-alpha also is required for rIFN-gamma-induced macrophage activation and enhanced antimicrobial activity in vivo. After an intraperitoneal injection of rIFN-gamma into CBA/J mice, their peritoneal macrophages released enhanced amounts of NO2- and inhibited the intracellular proliferation of Toxoplasma gondii. Injection of neutralizing antibodies against TNF-alpha simultaneously with the rIFN-gamma completely inhibited both the release of NO2- by macrophages and their toxoplasmastatic activity. Similar results were observed after intraperitoneal injection of a competitive inhibitor of L-arginine, NG-monomethyl-L-arginine, together with rIFN-gamma, demonstrating that in vivo L-arginine-derived reactive nitrogen intermediates are essential for the induction of toxoplasmastatic activity. Intravenous injection of rIFN-gamma inhibited the growth of Listeria monocytogenes in the livers and spleens of mice; this effect was abrogated by antibodies against TNF-alpha. Intravenous injection of a large dose of rTNF-alpha resulted in a decrease in the number of bacteria in the liver and spleen, but an injection of rIFN-gamma and rTNF-alpha did not result in enhanced inhibition of the proliferation of L. monocytogenes. Together, the results of the present study are the first to demonstrate that endogenous TNF-alpha is required in vivo for the expression of macrophage activation with respect to the release of reactive nitrogen intermediates and toxoplasmastatic activity and for enhanced listericidal activity in the livers and spleens of mice stimulated with rIFN-gamma.

Intravenous injection of interferon-gamma inhibits the proliferation of Listeria monocytogenes in the liver but not in the spleen and peritoneal cavity

In the present study the effects of intravenous administration of recombinant interferon-gamma (IFN-gamma) on both the proliferation of Listeria monocytogenes in the liver and spleen of mice and the listericidal activity of their peritoneal macrophages were investigated. A single intravenous injection of 1 x 10(6) U or three injections of 2 x 10(5) U recombinant IFN-gamma (rIFN-gamma) induced optimal activation of resident and exudate peritoneal macrophages, as judged by their ability to inhibit the intracellular proliferation of Toxoplasma gondii and their enhanced release of H2O2 and NO2-. The rate of intracellular killing of L. monocytogenes by the rIFN-gamma-activated resident and exudate macrophages was not higher than that by resident macrophages. Addition of 10 ng lipopolysaccharides (LPS) to the rIFN-gamma also did not enhance the bactericidal activity of the activated peritoneal macrophages. The decrease in the number of L. monocytogenes in the peritoneal cavity of mice that had received an i.p. injection of 1 x 10(4) U rIFN-gamma was similar to that in control mice. Intravenous administration of 1 x 10(5) rIFN-gamma activated cells in the liver, as indicated by the increased expression of Ia antigen, and reduced the rate of proliferation of L. monocytogenes in the liver relative to that in control mice when 0.1 LD50 or 1 LD50 L. monocytogenes were injected. However, when 10 LD50 L. monocytogenes were administered there was no effect on their proliferation. The number of L. monocytogenes found initially in the spleen of rIFN-gamma-treated mice was 20-30% of that in the spleen of control mice, but the rate of proliferation of L. monocytogenes was not reduced. These divergent results for the proliferation of L. monocytogenes in the liver, spleen and peritoneal cavity indicate that cells other than macrophages and/or as yet unknown local factors play an important role in the listericidal activity.

Hydrocortisone treatment of BCG-infected mice impairs the activation and enhancement of antimicrobial activity of peritoneal macrophages

The present study concerns the effect of hydrocortisone (HC) on the effector functions of Bacillus Calmette Guerin-purified protein derivative (BCG-PPD)-activated macrophages. Such activated macrophages release greater amounts of H2O2 and NO2-, inhibit the intracellular proliferation of T. gondii and kill L. monocytogenes more efficiently than resident macrophages. This activation was not fully expressed by macrophages from BCG-activated mice that had received a subcutaneous injection of HC 2 days before intraperitoneal injection of PPD, since the inhibition of the intracellular proliferation of T. gondii, the release of NO2- and the rate of intracellular killing of L. monocytogenes were lower than in macrophages from BCG-PPD-activated mice. However, treatment with HC did not impair the release of H2O2 by BCG-PPD-activated macrophages. The results show that the treatment of infected mice with HC inhibits their ability to develop adequate intracellular microbicidal mechanisms.

IFN-gamma-induced L-arginine-dependent toxoplasmastatic activity in murine peritoneal macrophages is mediated by endogenous tumor necrosis factor-alpha

Activated murine peritoneal macrophages inhibit the intracellular proliferation of Toxoplasma gondii and produce a number of cytokines, such as TNF-alpha and IL-1. Both TNF-alpha and IL-1 have been reported to be involved in the immune response against various microorganisms, but the mechanisms responsible for these effects are not known. In the present study it was investigated whether endogenously produced TNF-alpha and IL-1 are involved in the activation of peritoneal macrophages by rIFN-gamma leading to toxoplasmastatic activity and the production of reactive nitrogen intermediates. The rIFN-gamma-induced toxoplasmastatic activity was inhibited by neutralizing antibodies against mouse TNF-alpha in a dose-dependent and time-dependent way, but neutralizing antibodies against mouse IL-1 alpha and IL-1 beta did not affect this activity. Involvement of TNF-alpha in the induction of toxoplasmastatic activity was confirmed by our finding that rTNF-alpha in combination with a nonactivating concentration of rIFN-gamma inhibited the intracellular proliferation of T. gondii. No synergistic activity of rIL-1 and rIFN-gamma on the inhibition of T. gondii proliferation was found. Both rTNF-alpha and rIL-1 alpha alone inhibited the intracellular proliferation of T. gondii only slightly. Because it has been reported recently that activated macrophages produce reactive nitrogen intermediates that are essential in the induction of toxoplasmastatic activity, we investigated whether these intermediates are involved in the TNF-dependent induction of toxoplasmastatic activity. Neutralizing antibodies against mouse TNF-alpha inhibited also the release of NO2- by rIFN-gamma-activated macrophages almost completely. Macrophages incubated with rTNF-alpha in combination with a nonactivating concentration of rIFN-gamma released substantial amounts of NO2-, but rTNF-alpha and rIL-1 alpha alone, and the combination of rIL-1 alpha and a nonactivating concentration of rIFN-gamma induced only little NO2(-)-release by macrophages. To assess whether reactive nitrogen intermediates act directly or indirectly on the intracellular proliferation of T. gondii, macrophages were incubated with the L-arginine analog NG-monomethyl-L-arginine or the NADPH-inhibitor diphenylene iodonium, both inhibitors of the generation of reactive nitrogen intermediates. Good correlation was found between toxoplasmastatic activity and the release of NO2- during the 24-h activation period before infection of the macrophages with T. gondii, but no correlation was found between toxoplasmastatic activity and the release of NO2- during infection of the macrophages.(ABSTRACT TRUNCATED AT 400 WORDS)

IFN-gamma-induced L-arginine-dependent toxoplasmastatic activity in murine peritoneal macrophages is mediated by endogenous tumor necrosis factor-alpha

Activated murine peritoneal macrophages inhibit the intracellular proliferation of Toxoplasma gondii and produce a number of cytokines, such as TNF-alpha and IL-1. Both TNF-alpha and IL-1 have been reported to be involved in the immune response against various microorganisms, but the mechanisms responsible for these effects are not known. In the present study it was investigated whether endogenously produced TNF-alpha and IL-1 are involved in the activation of peritoneal macrophages by rIFN-gamma leading to toxoplasmastatic activity and the production of reactive nitrogen intermediates. The rIFN-gamma-induced toxoplasmastatic activity was inhibited by neutralizing antibodies against mouse TNF-alpha in a dose-dependent and time-dependent way, but neutralizing antibodies against mouse IL-1 alpha and IL-1 beta did not affect this activity. Involvement of TNF-alpha in the induction of toxoplasmastatic activity was confirmed by our finding that rTNF-alpha in combination with a nonactivating concentration of rIFN-gamma inhibited the intracellular proliferation of T. gondii. No synergistic activity of rIL-1 and rIFN-gamma on the inhibition of T. gondii proliferation was found. Both rTNF-alpha and rIL-1 alpha alone inhibited the intracellular proliferation of T. gondii only slightly. Because it has been reported recently that activated macrophages produce reactive nitrogen intermediates that are essential in the induction of toxoplasmastatic activity, we investigated whether these intermediates are involved in the TNF-dependent induction of toxoplasmastatic activity. Neutralizing antibodies against mouse TNF-alpha inhibited also the release of NO2- by rIFN-gamma-activated macrophages almost completely. Macrophages incubated with rTNF-alpha in combination with a nonactivating concentration of rIFN-gamma released substantial amounts of NO2-, but rTNF-alpha and rIL-1 alpha alone, and the combination of rIL-1 alpha and a nonactivating concentration of rIFN-gamma induced only little NO2(-)-release by macrophages. To assess whether reactive nitrogen intermediates act directly or indirectly on the intracellular proliferation of T. gondii, macrophages were incubated with the L-arginine analog NG-monomethyl-L-arginine or the NADPH-inhibitor diphenylene iodonium, both inhibitors of the generation of reactive nitrogen intermediates. Good correlation was found between toxoplasmastatic activity and the release of NO2- during the 24-h activation period before infection of the macrophages with T. gondii, but no correlation was found between toxoplasmastatic activity and the release of NO2- during infection of the macrophages.(ABSTRACT TRUNCATED AT 400 WORDS)

Nitrite production by activated murine macrophages correlates with their toxoplasmastatic activity, Ia antigen expression, and production of H2O2

Activated macrophages have various characteristics in common with exudate and resident macrophages, but the ability to inhibit intracellular proliferation of the protozoa Toxoplasma gondii, the expression of Ia antigen and the capacity to produce H2O2 varies among these cells. Assessment of these features of macrophages, which are generally used as criteria for macrophage activation, has certain drawbacks. Since activated murine macrophages, but not exudate or resident macrophages, produce considerable amounts of NO2-, assessment of NO2- production by these cells might serve as a measure of macrophage activation. The aim of the present study was to find out whether NO2- production by murine peritoneal macrophages correlates with the three generally accepted criteria for macrophage activation. Quantitative data on resident, exudate and activated macrophages revealed that the production of NO2- stimulated by a calcium-ionophore correlates best with the ability to inhibit the proliferation of T. gondii, Ia antigen expression, and capacity to produce H2O2. Because it is rapid and easy to perform, measurement of the amount of NO2- produced by murine macrophages stimulated with a calcium-ionophore offers the most practical criterion for distinction between activated macrophages and exudate and resident macrophages.

Effect of probenecid on phagocytosis and intracellular killing of Staphylococcus aureus and Escherichia coli by human monocytes and granulocytes

The present study concerns the effects of probenecid on the phagocytosis and intracellular killing of Staphylococcus aureus and Escherichia coli by human monocytes and granulocytes. In both monocytes and granulocytes the inhibitory effect on phagocytosis was very small. Inhibition of intracellular killing of S. aureus by monocytes and granulocytes by probenecid was concentration dependent, being half-maximal at about 2 mM probenecid, and near-maximal at about 5 mM probenecid. The intracellular killing could also be inhibited when probenecid was added when this process was already started. Probenecid also inhibited the intracellular killing of E. coli by granulocytes, but not by monocytes. In the concentration range used, probenecid had no toxic effect on phagocytes or bacteria during the 2 hr of the experiments.