Immunotherapy of murine visceral leishmaniasis with murine recombinant interferon-gamma and MTP-PE encapsulated in liposomes

Wnt5A Signaling Blocks Progression of Experimental Visceral Leishmaniasis

Visceral leishmaniasis, caused by L. donovani infection is fatal if left untreated. The intrinsic complexity of visceral leishmaniasis complicated further by the increasing emergence of drug resistant L. donovani strains warrants fresh investigations into host defense schemes that counter infections. Accordingly, in a mouse model of experimental visceral leishmaniasis we explored the utility of host Wnt5A in restraining L. donovani infection, using both antimony sensitive and antimony resistant L. donovani strains. We found that Wnt5A heterozygous (Wnt5A +/-) mice are more susceptible to L. donovani infection than their wild type (Wnt5A +/+) counterparts as depicted by the respective Leishman Donovan Units (LDU) enumerated from the liver and spleen harvested from infected mice. Higher LDU in Wnt5A +/- mice correlated with increased plasma gammaglobulin level, incidence of liver granuloma, and disorganization of splenic white pulp. Progression of infection in mice by both antimony sensitive and antimony resistant strains of L. donovani could be prevented by activation of Wnt5A signaling through intravenous administration of rWnt5A prior to L. donovani infection. Wnt5A mediated blockade of L. donovani infection correlated with the preservation of splenic macrophages and activated T cells, and a proinflammatory cytokine bias. Taken together our results indicate that while depletion of Wnt5A promotes susceptibility to visceral leishmaniasis, revamping Wnt5A signaling in the host is able to curb L. donovani infection irrespective of antimony sensitivity or resistance and mitigate the progression of disease.

Cytokines: Key Determinants of Resistance or Disease Progression in Visceral Leishmaniasis: Opportunities for Novel Diagnostics and Immunotherapy

Leishmaniasis is a parasitic disease of humans, highly prevalent in parts of the tropics, subtropics, and southern Europe. The disease mainly occurs in three different clinical forms namely cutaneous, mucocutaneous, and visceral leishmaniasis (VL). The VL affects several internal organs and is the deadliest form of the disease. Epidemiology and clinical manifestations of VL are variable based on the vector, parasite (e.g., species, strains, and antigen diversity), host (e.g., genetic background, nutrition, diversity in antigen presentation and immunity) and the environment (e.g., temperature, humidity, and hygiene). Chemotherapy of VL is limited to a few drugs which is expensive and associated with profound toxicity, and could become ineffective due to the parasites developing resistance. Till date, there are no licensed vaccines for humans against leishmaniasis. Recently, immunotherapy has become an attractive strategy as it is cost-effective, causes limited side-effects and do not suffer from the downside of pathogens developing resistance. Among various immunotherapeutic approaches, cytokines (produced by helper T-lymphocytes) based immunotherapy has received great attention especially for drug refractive cases of human VL. Therefore, a comprehensive knowledge on the molecular interactions of immune cells or components and on cytokines interplay in the host defense or pathogenesis is important to determine appropriate immunotherapies for leishmaniasis. Here, we summarized the current understanding of a wide-spectrum of cytokines and their interaction with immune cells that determine the clinical outcome of leishmaniasis. We have also highlighted opportunities for the development of novel diagnostics and intervention therapies for VL.

Leishmaniasis and various immunotherapeutic approaches

Leishmaniasis is a vector-borne infectious disease caused by multiple Leishmania (L.) species with diverse clinical manifestations. There is currently no vaccine against any form of the disease approved in humans, and chemotherapy is the sole approach for treatment. Unfortunately, treatment options are limited to a small number of drugs, partly due to high cost and significant adverse effects. The other obstacle in leishmaniasis treatment is the potential for drug resistance, which has been observed in multiple endemic countries. Immunotherapy maybe another important avenue for controlling leishmaniasis and could help patients control the disease. There are different approaches for immunotherapy in different infectious diseases, generally with low-cost, limited side-effects and no possibility to developing resistance. In this paper, different immunotherapy approaches as alternatives to routine drug treatment will be reviewed against leishmaniasis.

Particle-mediated delivery of cytokines for immunotherapy

The ability of cytokines to direct the immune response to vaccination, infection and tumors has motivated their use in therapy to augment or shape immunity. To avoid toxic side effects associated with systemic cytokine administration, several approaches have been developed using particle-encapsulated cytokines to deliver this cargo to specific cell types and tissues. Initial work used cytokine-loaded particles to deliver proinflammatory cytokines to phagocytes to enhance antimicrobial and antitumor responses. These particles have also been used to create a cytokine depot at a local site to supplement prophylactic or antitumor vaccines or injected directly into solid tumors to activate immune cells to eliminate established tumors. Finally, recent advances have revealed that paracrine delivery of cytokines directly to T cells has the potential to enhance T-cell mediated therapies. The studies reviewed here highlight the progress in the last 30 years that has established the potential of particle-mediated cytokine immunotherapy.

Stimulation of innate immunity in newborn kids againstCryptosporidium parvuminfection-challenge by intranasal/per-oral administration of liposomal formulation of N-L18-norAbu-GMDP adjuvant

The effects of a liposomal preparation of lipophilic immunomodulator β-D-GlcNstearoyl-(1-4)-norMurNAc-L-Abu-D-isoGln (N-L18-norAbu-GMDP) were investigated on resistance toCryptosporidium parvuminfection in neonatal kids. The liposomal preparation was administered subcutaneously or intranasally/orally (i.n./p.o.) twice at doses of 100 μg, 200 μg, or 1000 μg per kid pre-infection challenge. The treatment schemes were (i) 72 and 24 h pre-infection challenge, (ii) 24 h pre-infection challenge and 24 h post-infection challenge (oral inoculation with 1×107oocysts ofC. parvumin 5 ml of PBS). Administration of liposomal N-L18-norAbu-GMDP by i.n./p.o. route at the cumulative dose of 2000 μg per kid 72 and 24 h pre-infection challenge, lead to substantially increased clearance of coccidian parasites from various parts of the intestine. On the basis of histological examination, the distribution of cryptosporidia in the intestine and the severity of the infection, treated kids were classified on day 5 as having a strong reduction in infection in comparison to the control group (P<0·05). No cryptosporidia were found on the mucosal surface of treated kids by day 10, while the intestines of the control kids were still infected. All doses and routes of administration were judged effective with respect to suppression of cryptosporidia infections.

Liposomal Cytokines in the Treatment of Infectious Diseases and Cancer

Despite of the demonstrated activity of cytokines in vitro, their use in the clinical setting is often disappointing. Cytokine-related toxicity seriously limits optimal use in vivo. In addition, rapid degradation and excretion, neutralization and binding to receptors, or metabolization of the molecule results in a short half-life in serum when injected intravenously. As the dose-response curve of cytokines is relatively steep, outcome greatly benefits from improved delivery and bioavailability. One way to improve the pharmacokinetics of cytokines after systemic application is encapsulation in liposomes. An advantage of liposomes is that the encapsulated drug is protected from (rapid) degradation and excretion, and it eliminates the binding to neutralizing antibodies or (soluble) receptors. Moreover, liposomes can be tailored in such a way that they exhibit favorable pharmacokinetics, i.e., increased serum half-life and improved targeting to tissues or cells of interest. In this chapter, the use of liposomal cytokines in the treatment of cancer and infectious disease is discussed.

Designing of 'intelligent' liposomes for efficient delivery of drugs

The liposome- vesicles made by a double phospholipid layers which may encapsulate aqueous solutions- have been introduced as drug delivery vehicles due to their structural flexibility in size, composition and bilayer fluidity as well as their ability to incorporate a large variety of both hydrophilic and hydrophobic compounds. With time the liposome formulations have been perfected so as to serve certain purposes and this lead to the design of "intelligent" liposomes which can stand specifically induced modifications of the bilayers or can be surfaced with different ligands that guide them to the specific target sites. We present here a brief overview of the current strategies in the design of liposomes as drug delivery carriers and the medical applications of liposomes in humans.

Selective regulation of human immunodeficiency virus-infected CD4(+) lymphocytes by a synthetic immunomodulator leads to potent virus suppression in vitro and in hu-PBL-SCID mice

We have previously observed that the synthetic immunomodulator Murabutide inhibits human immunodeficiency virus type 1 (HIV-1) replication at multiple levels in macrophages and dendritic cells. The present study was designed to profile the activity of Murabutide on CD8-depleted phytohemagglutinin-activated lymphocytes from HIV-1-infected subjects and on the outcome of HIV-1 infection in severe combined immunodeficiency mice reconstituted with human peripheral blood leukocytes (hu-PBL-SCID mice). Maintaining cultures of CD8-depleted blasts from 36 patients in the presence of Murabutide produced dramatically reduced levels of viral p24 protein in the supernatants. This activity correlated with reduced viral transcripts and proviral DNA, was evident in cultures harboring R5, X4-R5, or X4 HIV-1 isolates, was not linked to inhibition of cellular DNA synthesis, and did not correlate with beta-chemokine release. Moreover, c-myc mRNA expression was down-regulated in Murabutide-treated cells, suggesting potential interference of the immunomodulator with the nuclear transport of viral preintegration complexes. On the other hand, daily treatment of HIV-1-infected hu-PBL-SCID mice with Murabutide significantly reduced the viral loads in plasma and the proviral DNA content in human peritoneal cells. These results are the first to demonstrate that a clinically acceptable synthetic immunomodulator with an ability to enhance the host's nonspecific immune defense mechanisms against infections can directly regulate cellular factors in infected lymphocytes, leading to controlled HIV-1 replication.

Liposomes containing interferon-gamma as adjuvant in tumor cell vaccines

PURPOSE

Liposomal systems may be useful as a cytokine supplement in tumor cell vaccines by providing a cytokine reservoir at the antigen presentation site. Here, we examined the effect of liposome incorporation of mIFNgamma on its potency as adjuvant in an established tumor cell vaccination protocol in the murine B16 melanoma model. Adjuvanticity of the mIFNgamma-liposomes was compared to that achieved by mIFNgamma-gene transfection of the B16 tumor cells. Furthermore, we studied whether liposomal incorporation of mIFNgamma indeed increases the residence time of the cytokine at the vaccination site.

METHODS

C57B1/6 mice were immunized with i) irradiated IFNgamma-gene transfected B16 melanoma cells or ii) irradiated wild type B16 cells supplemented with (liposomal) mIFNgamma, followed by a challenge with viable B16 cells. The residence time of the (liposomal) cytokine at the subcutaneous (s.c.) vaccination site was monitored using radiolabeled mIFNgamma and liposomes.

RESULTS

Immunization with irradiated tumor cells admixed with liposomal mIFNgamma generated comparable protection against B16 challenge as immunization with mIFNgamma-gene modified tumor cells. Irradiated tumor cells admixed with soluble mIFNgamma did not generate any protective responses. Radiolabeling studies indicated that free mIFNgamma rapidly cleared from the s.c. injection site. Association of [125I]-mIFNgamma with liposomes increased the local residence time substantially: liposomal association of mIFNgamma resulted in a prolonged local residence time of the cytokine as reflected by a 4-fold increase of the area under the curve. The amount of released cytokine in the optimal dose range corresponds to the amount released by the gene-transfected cells. Moderate but significant CTL-activity against B16 cells was found for mice immunized with irradiated cells supplemented with mIFNgamma-liposomes compared to untreated control animals.

CONCLUSIONS

Prolonged presence of mIFNgamma at the site of antigen presentation is crucial for the generation of systemic immune responses in the B16 melanoma model. These studies show that liposomal encapsulation of cytokines is an attractive strategy for paracrine cytokine delivery in tumor vaccine development.

The capacity to produce IFN-gamma rather than the presence of interleukin-4 determines the resistance and the degree of susceptibility to Leishmania donovani infection in mice

The immune response against Leishmania donovani infection has been investigated in one resistant mouse strain (C3H/HeJ) and three susceptible mouse strains (C57BL/6, BALB/c, and B10D2/n). In order to correlate the strain-specific course of infection with the individual T cell response phenotype, the ex vivo cytokine secretion patterns of splenic lymphocytes were assessed by ELISA (interferon-y [IFN-gamma], interleukin-4 [IL-4], IL-10) or by bioassay (IL-2). The strain-dependent differences in the course of infection correlated closely with the potency of T cells to produce IFN-gamma. C3H/HeJ mice produced high amounts of IFN-gamma before and during infection, whereas susceptible mice produced low amounts of IFN-gamma early during L. donovani infection. However, C57BL/6 mice, which recovered from the infection rapidly after the acute stage, developed marked IFN-gamma response within the first 30 days of infection. In contrast, in BALB/c and B10D2/n mice, the IFN-gamma production diminished during the acute stage, and this was associated with a delay in recovery and with subsequent switching into the chronic stage. Interestingly, CD8+ T cells contributed significantly to IFN-gamma production during this phase. In contrast to IFN-y, the levels of IL-4 in response to antigen or mitogen ex vivo were always very low. Moreover, neutralization of endogenous IL-4 in vivo by treatment with soluble murine IL-4 receptor did not result in significant decreases in the parasite burdens in spleen and liver but did cause a decrease in the serum IgE level of L. donovani-infected BALB/c mice. These results confirm that in visceral leishmaniasis a Thl-dominated immune response is protective against the L. donovani parasites and, furthermore, that the capacity to produce IFN-gamma rather than the presence of IL-4 determines the efficacy of the immune response in susceptible mice. The data show that CD8+ T cells represent an important source of IFN-gamma during L. donovani infection in susceptible mice, implying a role for this cell type in healing and development of protective immunity.

Evaluation of microspheres containing cytokine neutralizing antibodies in endotoxemia

Albumin microspheres are efficient carriers for delivering therapeutic agents to macrophages. In response to endotoxin, macrophages release tumor necrosis factor alpha (TNF alpha) and interleukin-1-beta (IL-1 beta). Blocking the effects of TNF alpha and IL-1 beta decreased lethality due to endotoxin-induced shock. In this study, we compared the efficacy of the microsphere form of TNF alpha and/or IL-1 beta neutralizing antibodies (NAs) with the free form of TNF alpha and/or IL-1 beta NA in preventing lethality due to endotoxemia and evaluated the duration of blockade by the microsphere form of TNF alpha and/or IL-1 beta NA on endotoxin-induced cytokine release. The results indicate that the microsphere form of TNF alpha and/or IL-1 beta NA protected 80% of the rats from lethal endotoxemia, while none of the rats that received the free from of TNF beta and/or IL-1 beta NA survived longer than 48 hr. The microsphere form of TNF alpha and/or IL-1 beta NA attenuated endotoxin-induced cytokine release more potently than the free form of TNF alpha and/or IL-1 beta NA in vivo. In vitro, the microsphere form of TNF alpha and/or IL-1 beta NA blocked endotoxin-induced cytokine release for at least 24 hr. Higher efficacy of the microsphere form of NA in reducing mortality and blocking cytokine release makes it more therapeutically advantageous than the free form of NA in the treatment of lethal endotoxemia.

Effect of liposome-encapsulation on immunomodulating and antiviral activities of interferon-gamma 1

The effect of liposome-encapsulation on the immunomodulating and antiviral activities of interferon-gamma (IFN-gamma) was evaluated in this study. The immunomodulating activity was measured by increases in phagocytic activity and in nitric oxide production by peritoneal macrophages from mice treated with both free and LIP-IFN-gamma (4000 U/mouse, intraperitoneal injection). Resident peritoneal macrophages harvested from mice treated with free unencapsulated IFN-gamma or muramyl dipeptide showed significant increases in macrophage yield, and enhanced ability to phagocytize zymosan particles. In mice treated with liposome-encapsulated IFN-gamma (LIP-IFN-gamma), both macrophage yield and phagocytic activity further increased by 2-fold over unencapsulated IFN-Y. In addition, the activation of peritoneal macrophages with LIP-IFN-gamma showed enhanced production of NO when the cells were cultured ex vivo. Using a murine respiratory influenza infection model, intranasally administered LIP-IFN-gamma conferred protection to 70% in mice challenged intranasally with 10 LD50 doses of influenza A/PR/8 virus compared with a 20% survival rate using free IFN-gamma. Together these results suggest that liposome-encapsulation increases the immunomodulating and antiviral activities of IFN-gamma. Liposome-encapsulation of IFN-gamma may provide additional therapeutic advantages by reducing IFN-gamma toxicity while prolonging its body retention.

Immunopharmacological activities and clinical development of muramyl peptides with particular emphasis on murabutide

Certain immunopharmacological activities of muramyl peptides have been associated with inflammatory and undesirable side-effects typically observed following the administration of the prototype molecule muramyl dipeptide. This activity is now demonstrated not to be linked to a direct activation of inflammatory processes in endothelial cells. Neither MDP nor other structural derivatives were able to induce inflammatory cytokines release or E-selectin gene expression in cultured human umbilical vein endothelial cells. However, oral administration of muramyl peptides has been reported to induce certain biological effects, including the downregulation of anamnestic, antigen-specific IgE responses, which are not observed following parenteral administration. We elaborate on these findings and extend them to show the efficacy of a new muramyl peptide in suppressing polyclonally induced serum IgE levels in anti-IgD-treated mice. The comparative effects of muramyl peptides, selected for clinical development, on the induction of cytokines in human whole blood are then presented at the level of mRNA accumulation and protein secretion. Moreover, the cytokine profile induced in vitro and in vivo by the combination of the safe immunostimulant, Murabutide, with interferon-alpha is examined. This combination reveals a selective and beneficial synergistic activity and induces anti-inflammatory cytokines in the absence of synergistic toxicity. The potential and the implications for the use of a therapeutic combination of an immunostimulant with a cytokine are discussed.

Liposomes as delivery systems in the prevention and treatment of infectious diseases

Research on the potential application of liposomes in the prevention and treatment of infectious diseases has focussed on improvement of the therapeutic index of antimicrobial drugs and immunomodulators and on stimulation of the immune response to otherwise weak antigens in vaccines composed of purified micro-organism subunits. In this review current approaches in this field are outlined. The improved therapeutic index of antimicrobial drugs after encapsulation in liposomes is a result of enhanced drug delivery to infected tissue or infected cells and/or a reduction of drug toxicity of potentially toxic antibiotics. Liposomal encapsulation of immunomodulators that activate macrophages aims at reducing the toxicity of these agents and targeting them to the cells of the mononuclear phagocyte system in order to increase the nonspecific resistance of the host against infections. Studies on the immunogenicity of liposomal antigens have demonstrated that liposomes can potentiate the humoral and cell mediated immunity to a variety of antigens.

Interaction of alveolar macrophages and respiratory syncytial virus

Respiratory syncytial virus (RSV) is a major cause of acute lower respiratory tract illness in infants. However, the mechanisms leading to resolution of RSV infections are poorly understood. Since alveolar macrophages play an important role in defending the respiratory tract against infectious agents we investigated the interactions of RSV with these cells. Murine alveolar macrophages were challenged in vitro with RSV at different multiplicities of infection. The percentage of macrophages expressing viral antigen was determined by staining with monoclonal anti-RSV antibodies and evaluation by fluorescence microscopy or FACS analysis. The ability of macrophages to support virus replication was measured by a plaque forming assay on HEp-2 cells. Cell lysates of macrophages contained only small amounts of viable RSV in comparison to disrupted HEp-2 cells. The amount of viable RSV as well as the percentage of macrophages expressing viral antigen decreased rapidly over time. Activated macrophages had a reduced virus load in comparison to resting macrophages. RSV infected macrophages released biologically active tumor necrosis factor (TNF) in a virus dose dependent manner. In contrast, a high virus inoculum resulted in reduced microbicidal activity and oxygen radical production. Our results suggest that RSV infection influences different functions of alveolar macrophages in various ways. Since TNF is thought to restrict viral replication in several cell types it may play a role in limiting virus replication.

Liposomes in the treatment of infections

The use of liposomes in the treatment of severe infections is under investigation. Classical liposomes which localize in cells of the mononuclear phagocyte system (MPS) can be exploited in two ways. First for targeting of macrophage modulators such as muramyl peptides or IFN-gamma, to stimulate the cells of the MPS to maximal blood clearance capacity. This enhanced nonspecific anti-infectious resistance is important as in immunocompromised patients micro-organisms frequently appear in the blood from a local infection. Secondly, classical liposomes are successfully used as carriers of antibiotics in experimental intracellular parasitic-, viral-, fungal- or bacterial infections in MPS tissues. Based on these data extensive studies in patients with severe fungal infections have demonstrated successful treatment with liposomal or lipid-complexed amphotericin B. More recently, liposomal amphotericin B appeared to be effective in patients with drug-resistant visceral leishmaniasis. For the treatment of Mycobacterium avium complex infection in AIDS patients the efficacy of liposomal gentamicin is under investigation. With respect to infections in non-MPS tissues the applicability of Stealth liposomes characterized by long circulation half-lives is under investigation. Substantial localization of these liposomes in infected lung tissue of rats was demonstrated. Preliminary data in experimental bacterial lung infection showed superior efficacy of antibiotic encapsulated in Stealth liposomes.

Liposomes as carriers of cancer chemotherapy. Current status and future prospects

Chemotherapy is a modality of cancer therapy that needs much improvement. Development of a new chemical entity is very costly and time consuming, but improvements in delivery of existing agents may yield more rapid clinical results. Liposomes and other lipid-based drug delivery systems have the advantage, in this context, of utilising no new chemical entities. In terms of mechanism of action, tumour targeting has been the focus of much work in liposomal drug delivery. The recent development of liposomes with longer circulation times has led to improved tumour targeting in animal studies. Other mechanisms of action, such as release from drug depot formulations, heat-triggered local drug release, and transfection of genetic materials, may prove to be useful in humans. Liposomal formulations of more than a dozen antineoplastic agents have shown promise in vitro and in animal models. Somewhat mundane, but nevertheless crucial, issues of medical rationale and formulation engineering, and commercial considerations, have slowed testing in patients with cancer. However, 3 antineoplastic agents, doxorubicin, daunorubicin and cytarabine, are in advanced stages of clinical testing in humans. One or more of these should prove to be a medically useful and commercially viable product within the next few years.

Influence of acetylsalicylic acid on a Listeria monocytogenes infection

The influence of acetylsalicylic acid (ASA, CAS 50-78-2) on the Listeria monocytogenes infection in balb/c mice was investigated. One day prior to lethal or sublethal infection, balb/c mice were treated intravenously with therapeutic concentrations of ASA alone or ASA in combination with murine recombinant interferon gamma, a lymphokine produced by T-helper cells. Three days post-infection, parasite burdens of spleen and liver were determined by the colony-forming unit assay. It was shown that the prophylactic application of ASA in a concentration of 5 mg/kg body weight resulted in a more than 10-fold reduction of viable Listeria monocytogenes in spleen and liver of balb/c mice. In addition, the combination of a suboptimal dosage of interferon gamma with ASA resulted in a significantly higher survival rate compared to the untreated controls.

Interferon-gamma in starch microparticles: nitric oxide-generating activity in vitro and antileishmanial effect in mice

Recombinant mouse interferon-gamma (mu IFN-gamma) was covalently coupled to polyacryl starch microparticles, a lysosomotropic drug carrier. The microparticle-bound mu IFN-gamma was found to activate cultured macrophages for nitrite production and had an anti-leishmanial effect in mice. Low doses of mu IFN-gamma, which had no effect in the free form, when bound to microparticles significantly reduced the load of Leishmania donovani in infected mice. Further, inducement of nitrite production in cultured macrophages by microparticle-bound mu IFN-gamma required intact cell membrane receptors.

Free versus liposome-encapsulated muramyl tripeptide phosphatidylethanolamide (MTPPE) and interferon-y (IFN-y) in experimental infection with Listeria monocytogenes

The effect of free and liposome-encapsulated muramyl tripeptide phosphatidylethanolamide (MTPPE) and interferon-y (IFN-y) on the resistance against Listeria monocytogenes infection in mice was investigated. It was shown that administration of MTPPE or IFN-y at 24 h before bacterial inoculation led to increased resistance against L. monocytogenes infection in terms of a decrease in bacterial numbers in liver and spleen. Encapsulation of MTPPE and IFN-y in liposomes increased their efficacy 33- or 66-fold, respectively. In addition, liposomal encapsulation led to a more rapid decrease in bacterial numbers. The immunomodulator to lipid ratio appeared to be very important in the antibacterial effect of LE-MTPPE and LE-IFN-y. When nontherapeutic doses of liposome-encapsulated MTPPE or IFN-y were administered in a larger amount of lipid (so at higher lipid: immunomodulator ratio), these doses became effective. Exposure of macrophages in monolayer infected with L. monocytogenes in vitro to MTPPE had no effect, whereas exposure to IFN-y only led to growth inhibition of the intracellular bacteria. However, incubation of macrophages with a combination of MTPPE and IFN-y resulted in killing of the intracellular bacteria. Exposure of macrophages in vivo to both immunomodulators in combination can be effected by using liposomes as carriers. It was observed that administration of MTPPE and IFN-y co-encapsulated in liposomes resulted in a synergistic enhanced antibacterial resistance against L. monocytogenes. Both reactive oxygen and nitrogen intermediates seemed to play a role in the killing of L. monocytogenes by macrophages activated with a combination of MTPPE and IFN-y.

"Discordant" influence of equine recombinant interferon-beta 1 on the cytotoxic capacity of equine polymorphonuclear neutrophils and peripheral blood mononuclear cells in vitro and in vivo

The influence of recombinant equine interferon-beta 1 (rEqIFN-beta 1) on mononuclear cells of peripheral blood (PBMC) and polymorphonuclear neutrophilic granulocytes (PMN) was tested under in vitro and ex vivo conditions. Treatment of equine PBMC with IFN in vitro enhanced the antibody-independent cytotoxicity (AICC) and antibody-dependent cytotoxicity (ADCC) while there was no significant effect on the cytotoxic capacity of PMN treated with rEqIFN-beta 1 in vitro. Ex vivo there was an increased capacity of AICC and ADCC upon single or multiple application of rEqIFN-beta 1 in PMN, only. Treatment with rEqIFN-beta 1 thus induced an increased cellular cytotoxicity in vitro and in vivo but in different populations of peripheral blood cells. In vivo rEqIFN-beta 1 causes a pronounced activation of PMN but not of PBMC as cytotoxic effector cells. This might be achieved indirectly, e.g., by cytokines produced by IFN-sensitive cells.