In vivo alterations in cytokine production following interleukin-12 (IL-12) and anti-IL-4 antibody treatment of CB6F1 mice with chronic cutaneous leishmaniasis

Antileishmanial and Immunomodulatory Activity of Allium sativum (Garlic): A Review

Leishmaniasis is caused by an obligate intracellular protozoa belonging to Leishmania genus. The current drugs for treatment of leishmaniasis possess many disadvantages; therefore, researchers are continuously looking for the more effective and safer drugs. The aim of this study is to review the effectiveness, toxicities, and possible mechanisms of pharmaceutical actions of different garlic extracts and organosulfur compounds isolated from garlic against Leishmania spp. in a variety of in vitro, in vivo and clinical trials reports. All relevant databases were searched using the terms "Allium sativum," "Garlic," "Allicin," "Ajoene," "Leishmania," "in vitro," "in vivo," and "clinical trial," alone or in combination from 5 English databases (Web of Science, PubMed, Science Direct, Scopus, Google Scholar) and 3 Persian databases (Scientific Information Database, Iran Medex, and Magiran) from 1990 to 2014. In summary, garlic with immunomodulatory effects and apoptosis induction contributes to the treatment of leishmaniasis.

Worms and allergy

Worms and asthma are associated with a type 2 immune response, but evidence has accumulated that helminth infection is negatively associated with atopy, prevalence of allergic diseases and severity of asthma. One important difference between these polarized type 2 responses is that in allergy modulation of the immunological response is not appropriate, whereas in infection with helminths, several host mechanisms down-regulate the host immune response. As a result, patients infected with worms have a decrease in both type 1 and type 2 responses. The main mechanism involved in this down-modulation is increased production of IL-10, but expansion of regulatory T cells and NKT cells may also participate. Regarding the interaction between worms and allergy, a few variables need to be taken in account: phase (acute or chronic) of helminth infection, parasite load and species of helminth. In animals and humans, acute helminth infection may increase manifestations of allergy, whereas chronic infection with parasites decreases atopy. The modulation of the immune response by helminths is dependent on having an adequate parasite load. Moreover, although several helminth species have been shown to modulate immune responses, most in vitro and in vivo studies have focused on the importance of Schistosoma mansoni in down-modulating allergic reactions.

Microbial considerations in genetically engineered mouse research

Microbial infections have long been of concern to scientists using laboratory rodents because of their potential to confound and invalidate research. With the explosion of genetically engineered mice (GEM), new concerns over the impact of microbial agents have emerged because these rodents in many cases are more susceptible to disease than their inbred or outbred counterparts. Moreover, interaction between microbe and host and the resulting manifestation of disease conceivably differ between GEM and their inbred and outbred counterparts. As a result, infections may alter the GEM phenotype and confound interpretation of results and conclusions about mutated gene function. In addition, because GEM are expensive to produce and maintain, contamination by pathogens or opportunists has severe economic consequences. This review addresses how microbial infections may influence phenotype, how immunomodulation of the host as the result of induced mutations may modify host susceptibility to microbial infections, how novel host:microbe interactions have led to the development of new animal models for disease, how phenotype changes have led to the discovery of new pathogens, and new challenges associated with prevention and control of microbial infections in GEM. Although the focus is on naturally occurring infections, extensive literature on the use of GEM in studies of microbial pathogenesis also exists, and the reader is referred to this literature if microbial infection is a suspected culprit in phenotype alteration.

TRANCE-RANK costimulation is required for IL-12 production and the initiation of a Th1-type response to Leishmania major infection in CD40L-deficient mice

Blockade of TNF-related activation-induced cytokine (TRANCE)-receptor activator of NF-kappaB (RANK) interaction reverses healing in CD40L(-/-) mice infected with Leishmania major. Although previous studies demonstrated a requirement for CD40-CD40L interaction in production of IL-12 and the development of resistance to Leishmania infection, we recently showed that CD40L(-/-) mice control infection when inoculated with low numbers of parasites and that cells from these mice produce IL-12. Here, we show that in vivo treatment with a TRANCE receptor fusion protein results in a decrease in numbers of IL-12 producing cells as well as a shift from a dominant Th1 to Th2 type response in infected mice. These results demonstrate that CD40L(-/-) mice use the TRANCE-RANK costimulatory pathway to promote IL-12 production and the activation of a protective Th1 type response.

T helper responses to Japanese encephalitis virus infection are dependent on the route of inoculation and the strain of mouse used

T helper cytokine and IgG subtype responses were studied in three strains of mice (C57BL/6J, Swiss albino, BALB/c; n=90 per strain) immunized with live Japanese encephalitis virus (JEV) by intraperitoneal (IP), subcutaneous (SC) and peroral (PO) routes. Lymphocytes obtained from the spleens of immunized and control mice were stimulated in vitro with JEV for 48 h and the supernatants were assayed for the presence of the cytokines IL-4 and IFN-gamma. JEV-specific IgG isotypes were also measured in the sera of immunized mice. T helper cytokine responses in mice immunized with JEV were found to be strain- and route-specific in the three species tested. Moreover, they were also dependent on the type of immunogen used (live vs killed virus), as well as the number of doses administered. C57BL/6J and BALB/c mice were more uniform in their T helper responses compared with the outbred Swiss albino mice and induced a good Th1 response (P<0.001). Among the three routes evaluated, the IP and SC routes consistently elicited a Th1 response compared with the PO route (P<0.001), where an initial Th2-type response reverted to a Th1 response after repeated immunization. Live JEV induced a Th1 response while the commercial killed vaccine induced a predominant Th2 profile.

Effect of a combination therapy between IL-12 and soluble IL-4 receptor (sIL-4R) on Candida albicans and herpes simplex virus type I infections in thermally injured mice

The effectiveness of a combination using IL-12 and soluble IL-4 receptor (sIL-4R) to treat severe infections of herpes simplex virus type 1 (HSV-1) and Candida albicans in thermally injured mice was investigated. Although sIL-4R decreased burn-associated type 2 T-cell responses, the effect of sIL-4R was minimal on the morbidity and mortality of thermally injured mice exposed to 250 times LD50 of HSV-1 or 10 times LD50 of C. albicans. Compared with 100% mortality in control mice, mortality for HSV-1 and C. albicans was 40 and 20%, respectively, in thermally injured mice that received IL-12 and sIL-4R in combination. After stimulation with anti-CD3 monoclonal antibody, splenic T cells from thermally injured mice exposed to large amounts of HSV-1 or C. albicans did not produce gamma interferon (IFN-gamma) into their culture fluids. However, IFN-gamma was produced by splenic T cells from thermally injured and infected mice treated with IL-12 and sIL-4R in combination. These results suggest that therapeutic treatment with a combination of IL-12 and sIL-4R may be effective by inducing type 1 T-cell responses in thermally injured mice exposed to large amounts of HSV-1 or C. albicans.

Mercury enhances susceptibility to murine leishmaniasis

The genetic background of mice infected with Leishmania major determines the response to infection, resulting in a resistant or susceptible phenotype. Susceptible mice develop a T-helper type 2 (Th2)-type immune response following infection distinguished by the development of interleukin (IL)-4 secreting T cells in the lymph node and spleen. In SJL mice, which normally heal L. major lesions, subtoxic doses of mercury induce an autoimmune syndrome characterized by an expansion of Th2 cells. In this study, we examined the effect of mercury administration on the outcome of L. major infection in SJL mice. We show that subtoxic doses of mercuric chloride (HgCl2) exacerbate disease outcome in SJL mice resulting in increased footpad swelling and increased parasite burdens. Furthermore, the effects of HgCl2 treatment on resistance to L. major are time-dependent. The nonhealing phenotype was observed only if mice had been treated with HgCl2 prior to L. major infection for at least 1 week, a timepoint at which mice treated with HgCl2 alone had increased splenocyte IL-4 production. HgCl2 treatment also increased production of serum immunoglobulin (Ig)E and IgG1, two IL-4 dependent isotypes. These results show that HgCl2 treatment enhances the susceptibility to L. major in SJL mice, consistent with the induction of host Th2 parameters. These findings have implications for the role of mercury contamination in areas of endemic leishmaniasis.

A single intradermal administration of soluble leishmanial antigen and plasmid expressing interleukin-12 protects BALB/c mice from Leishmania major infection

In murine leishmaniasis, the induction of the T-helper type 1 (Th1) response contributes to infection resistance, whereas the establishment of the Th2 response makes the mice susceptible to infection. Interleukin-12 (IL-12) plays a pivotal role in the diversification of immune responses to the Th1 type. In this study, we tested whether the co-administration of IL-12 expression plasmid which compose p35 and p40 subunits and soluble leishmanial antigen (SLA) will skew the susceptible BALB/c mice to Th1 response and protect from leishmaniasis. When the mice were intradermally injected with the combination of IL-12 plasmid and SLA 7 days prior to the challenge with 1x10(6) promastigotes of Leishmania major, the local lesions completely healed and the parasite burden in the local lymph nodes significantly decreased. The cured mice attained long-term immunity, and were resistant to any subsequent rechallenge of the lethal dose of the parasite. The protective effect was associated with the development of a Th1 response, as demonstrated by the enhanced level of antigen-specific interferon-gamma (IFN-gamma) and dominant production of IgG2a in the serum. In contrast, the administration of empty plasmid plus SLA or IL-12 plasmid alone failed to protect the disease and shape the Th1 response. Furthermore, the protective efficiency induced by the vaccination was clearly prevented by the injection of either neutralizing anti-IL-12 mAb or anti-IFN-gamma mAb. The IL-12 expression plasmid is thus an effective adjuvant for the elicitation of a protective Th1 response against leishmaniasis and is therefore, considered to be appropriate for vaccinations that require the induction of Th1 type immunity.

Interleukin-4 receptor alpha-deficient BALB/c mice show an unimpaired T helper 2 polarization in response to Leishmania major infection

We recently generated interleukin-4 (IL-4) receptor alpha-deficient (IL-4Ralpha(-/-)) BALB/c mice and showed evidence for a protective role of IL-13-mediated functions in leishmaniasis. In this study, we investigated the IL-4 expression and T helper 2 (Th2) development in Leishmania major-infected IL-4Ralpha(-/-) mice. Here we show that the early burst of IL-4 expression observed in L. major-infected BALB/c mice is independent of IL-4Ralpha-mediated functions. Subsequently, we confirmed an impaired Th2 development in vitro. Unexpectedly, during L. major infection, isolated CD4(+) IL-4Ralpha(-/-) T cells expressed high IL-4- but low gamma interferon (IFN-gamma)-specific mRNA, comparable to Th2-polarized BALB/c CD4(+) cells and in contrast to Th1-polarized C57BL/6 CD4(+) cells. Since antigen-specific restimulated popliteal lymph node cells (PLN) of IL-4Ralpha(-/-) mice also responded with high IL-4 but low IFN-gamma production, comparable to Th2-polarized cells from wild-type BALB/c mice and in contrast to Th1-polarized C57BL/6 cells, these results suggested an unimpaired Th2 polarization during an established infection with L. major. To further define the observed IL-4 receptor-independent Th2 cell phenotype, we determined an independent Th2 marker, the IL-12 receptor beta-2 (IL-12Rbeta2)-specific transcript levels of CD4(+) T cells. Confirming Th2 polarization in L. major-infected IL-4Ralpha(-/-) mice, comparable IL-12Rbeta2 message levels between CD4(+) T cells from infected IL-4Ralpha(-/-) mice and Th2 cells from BALB/c mice were found, whereas Th1-polarized C57BL/6 cells showed strikingly increased IL-12Rbeta2 expression levels. These results indicate that signals mediated by the IL-4Ralpha are not necessary to induce and sustain an efficient IL-4 expression and Th2 polarization in L. major-infected BALB/c mice and suggest that IL-4Ralpha-independent mechanisms underlie the default Th2 development in L. major-infected BALB/c mice.

Divergent regulation of the murine CC chemokine C10 by Th(1) and Th(2) cytokines

Chemokines are typically found as products of acute stimulation of host defence cells. In contrast, the mouse CC chemokine C10 was previously shown to be a delayed, stably induced product of macrophages treated with interleukin 3 (IL-3), IL-4 or GM-CSF. We investigated the possibility that C10 is differentially regulated by cytokines associated with Th(1)and Th(2)cells. Northern blot analysis of bone marrow-derived macrophages showed that, in addition to IL-4, the Th(2)-specific cytokines IL-10 and IL-13 upregulated C10 over a 48-h period in a dose-dependent manner. In contrast, MIP-1alpha and MCP-1/JE were induced by IL-3 or GM-CSF at 48 h and this induction was inhibited by IL-4. Interferon gamma, a Th(1)-specific product, abolished the induction of C10 mRNA and protein by either IL-3 or granulocyte-macrophage colony-stimulating factor (GM-CSF) in either bone marrow-derived or peritoneal macrophages. The inhibition of C10 production by interferon gamma was not NO dependent. Finally the GM-CSF-mediated induction of C10 in peritoneal macrophages was eliminated when these cells presented antigen to established T cells of Th(1)phenotype. The findings are consistent with a potential role for C10 in the modulation of immune reactions of Th(2)type.

Therapeutic Protective Effects of IL-12 Combined with Soluble IL-4 Receptor Against Established Infections of Herpes Simplex Virus Type 1 in Thermally Injured Mice

The effect of combination therapy between IL-12 and soluble IL-4R (sIL-4R) on the established infection of HSV-1 in thermally injured mice (TI mice) was investigated. All of the TI mice infected with lethal amounts of HSV-1 died when IL-12 was given therapeutically at a dose of 500 U/mouse. However, 80% of these mice treated prophylactically with IL-12 survived compared with 0% survival of the same mice treated with saline. The therapeutic administration of IL-12 to TI mice currently infected with HSV-1 caused an 80% survival of these mice when the treatment was combined with sIL-4R. Although IL-12 did not stimulate IFN-γ production in cultures of splenic T cells from TI mice, IFN-γ was produced by stimulation with IL-12 when the producer cells were prepared from TI mice that had been treated previously with sIL-4R. After stimulation with anti-CD3 mAb, splenic T cells from TI mice with the established infection of HSV-1 produced IL-4 into their culture fluids. However, IL-4 was not produced by splenic T cells that were prepared from the same infected mice treated with IL-12 and sIL-4R in combination. The results obtained herein indicate that the efficacies of the combination therapy against the established infection of HSV-1 may result from the IFN-γ production stimulated by IL-12 in TI mice that are treated with sIL-4R for reducing burn-associated type 2 T cell responses.

Phagocytosis of Leishmania mexicana amastigotes by macrophages leads to a sustained suppression of IL-12 production

Healing of leishmaniases is dependent on activation of parasitized macrophages (Mphi) by IFN-gamma, which is secreted by Leishmania-specific Th1 cells. IL-12 enhances IFN-gamma production by Th1 cells and is crucial for cure. The host cells of Leishmania sp., Mphi, are a main source of IL-12 in vivo. We report that infection of quiescent murine Mphi with L. mexicana or L. major amastigotes does not induce IL-12 production. Moreover, infection suppresses IL-12 secretion by Mphi activated by LPS, by CD40 cross-linking or cognate interaction with Th1 cells. IL-12 secretion is also suppressed in Mphi activated after phagocytosis of latex beads. Suppression is independent of engagement of CR3 or FcgammaR during phagocytosis, is not mediated by IL-10 and does not alter steady state IL-12p40 mRNA levels. In addition, suppression of IL-12 secretion does not depend on Mphi activation concurrent to infection. In contrast, NO production was not inhibited. Thus, Mphi effector functions are differentially affected and this may be a general effect of phagocytosis of non-activating particles. The possible implications of this effect on the infection are discussed.

Immunomodulation of Chiclero's ulcer. Role of eosinophils, T cells, tumour necrosis factor and interleukin-2

The progression of cutaneous leishmaniasis is controlled largely by cell-mediated immunity. Two subpopulations of CD4+ T cells exist that control healing or immunopathology of murine and, perhaps, human leishmaniasis. To better understand the immunological pathways controlling outcome of the human disease, we analysed the pattern of tumour necrosis factor (TNF) and interleukin-2 (IL-2), both of which were present in the sera of humans with active or healed chiclero's ulcer, in relation to the development of delayed-type hypersensitivity (DTH) responses and leucocyte counts in peripheral blood. Increased serum levels of IL-2 and TNF-alpha were apparent only in individuals with active lesions. All individuals with localized cutaneous leishmaniasis developed a strong DTH. The number of T cells was lower in the blood of diseased individuals and the CD4/CD8 ratio was reduced (from 1.5 to 1.0) when compared with the control group. However, diseased and recently cured individuals developed eosinophilia. We conclude that important alterations of the immune response exists in humans suffering from this normally self-healing infection.

Differentiation, regulation, and death of T helper cell subsets during infection with Leishmania major

The development and regulation of specific types of immune responses are dependent on understanding the biology of T helper cell (Th cells) subsets. We primarily use murine infections with the intracellular protozoan parasite, Leishmania major, as our model to investigate Th1/2 cell biology, where following infection, some inbred strains of mice develop a Th1 response and heal, but others develop a Th2 response and fail to control parasite replication. We focus on three major questions: 1. What factors are involved in Th cell development? 2. How can we switch an established immune response from one type to another? 3. How are immune responses downregulated once the parasites are eliminated? We demonstrated that interleukin (IL)12 promotes Th1 cell development and that IL12 is an effective adjuvant for cell-mediated immunity. We are now defining factors regulating the expression of the IL12 receptor and the importance of CD28-B7 interactions for the development of vaccine-induced immunity. We also found that IL12, in combination with chemotherapy, abrogates a Th2 response. These results have implications for treatment of infectious diseases, autoimmunity, and allergy. Currently, we are studying how such switching occurs. Finally, we found that TNFRp55-/- mice are unable to heal leishmanial lesions in spite of eliminating the parasites. This result suggests that the tumor necrosis factor receptor (TNFR) p55 plays a critical, and previously unrecognized, role in downregulating pathogen-induced inflammatory responses. Our current hypothesis is that the TNFRp55 is required for induction of cell death in these lesions, and that in its absence, lymphocytes accumulate at the site of inflammation.

Successful therapy of chronic, nonhealing murine cutaneous leishmaniasis with sodium stibogluconate and gamma interferon depends on continued interleukin-12 production

Treatment of nonhealing forms of human leishmaniasis with antimonial drugs in combination with gamma interferon (IFN-gamma) may promote healing more effectively than conventional drug therapy. Although the natures of immune responses in patients prior to treatment are often unclear, it is generally assumed that such therapy also promotes a switch from a Th2-type response to a dominant Th1-type response. We have examined the efficacy of IFN-gamma therapy, in combination with drug therapy, to promote healing and a Th2-to-Th1 switch in highly susceptible BALB/c mice infected with Leishmania major. Short-term treatment with the antileishmanial drug sodium stibogluconate failed to significantly alter the course of disease or the immune response when it was given during the third and fourth weeks of infection. IFN-gamma therapy, administered over the same time period, also failed to induce cure or a Th1 dominant response. In contrast, mice treated with a combination of drug and IFN-gamma therapy resolved their infections and developed Th1-type responses. However, administration of an antibody to interleukin 12 (IL-12) reversed the therapeutic effects of therapy with drug plus IFN-gamma, suggesting that IFN-gamma promotes cure through an IL-12-dependent mechanism. Analysis of mRNA levels within parasitized lesions suggests that drug treatment plus IFN-gamma treatment, in addition to reducing parasite numbers, results in reduced levels of IL-4, IL-10, and transforming growth factor beta transcripts but increased levels of transcripts of the p40 chain of IL-12 and inducible nitric oxide synthase, which catalyzes the production of nitric oxide. Together, these results suggest that such immunotherapy may promote the development of a protective Th1-type response in susceptible mice by a mechanism which involves both suppression of regulatory cytokines and enhancement of IL-12 and nitric oxide production.

Interleukin-12 and infectious diseases: a potential novel therapy

Interleukin-12 (IL-12) is emerging as a central component of both innate and acquired immunity. The multiplicity of biological activities associated with this cytokine, particularly the stimulation of cell-mediated immunity, suggests that it may be crucial in the control of extracellular and intracellular infections. In in vitro studies, IL-12 production is initiated rapidly after infection with a variety of viral, parasitic, fungal and bacterial agents. This induction correlates well with the reported resistance or susceptibility of animals to infection with these agents. Other factors may, however, influence responses in vivo, including host genetic make-up, microbial load and the induction of antagonistic cytokine pathways, notably IL-4 and IL-10. In some situations, IL-12 may direct immune responses to inappropriate pathways, and worsen disease, so that careful consideration of the type of required immune response is needed before IL-12 therapy is initiated. IL-12 treatment may also be useful in promoting protective immune responses to vaccines, allowing systemic immunisation with lower doses, or even normally non-immunogenic preparations, of antigen. Finally, IL-12 has been demonstrated to act in concert with standard antimicrobial chemotherapy in viral, parasitic, fungal and bacterial infections, allowing a reduction in the dose of the agent used and providing hope that such combination therapy may more effectively control drug-resistant strains of infectious agents.