IL-10 receptor blockade controls the in vitro infectivity of Leishmania infantum and promotes a Th1 activation in PBMC of dogs with visceral leishmaniasis.

An important strategy to reduce the risk of visceral leishmaniasis (VL) in humans is to control the infection and disease progression in dogs, the domestic reservoir of Leishmania infantum parasites. Certain therapeutic strategies that modulate the host immune response show great potential for the treatment of experimental VL, restoring the impaired effector functions or decreasing host excessive responses. It is known that the overproduction of interleukin-10 (IL-10) promotes parasite replication and disease progression in human VL as well as in canine visceral leishmaniasis (CVL). Thus, in the present study we investigated the potential of the anti-canine IL-10 receptor-blocking monoclonal antibody (Bloq IL-10R) to control and reduce in vitro infectivity of L. infantum and improve the ability of PBMC isolated from VL dogs to alter the lymphoproliferative response and intracytoplasmic cytokines. Overall, GFP+Leishmania showed lower capacity of in vitro infectivity in the presence of Bloq IL-10R. Moreover, addition of Bloq IL-10R in cultured PBMC enhanced T-CD4 and CD8 proliferative response and altered the intracytoplasmic cytokine synthesis, reducing CD4+IL-4+ cells and increasing CD8+IFN-γ+ cells after specific antigen stimulation in PBMC of dogs. Furthermore, we observed an increase of TNF-α levels in supernatant of cultured PBMC under IL-10R neutralizing conditions. Together, our findings are encouraging and reaffirm an important factor that could influence the effectiveness of immune modulation in dogs with VL and suggest that blocking IL-10R activity has the potential to be a useful approach to CVL treatment.

Systems Biology Analysis of the Radiation-Attenuated Schistosome Vaccine Reveals a Role for Growth Factors in Protection and Hemostasis Inhibition in Parasite Survival.

In spite of several decades of research, an effective vaccine against schistosomiasis remains elusive. The radiation-attenuated (RA) cercarial vaccine is still the best model eliciting high protection levels, although the immune mechanisms have not yet been fully characterized. In order to identify genes and pathways underlying protection we investigated patterns of gene expression in PBMC and skin draining Lymph Nodes (LN) from mice using two exposure comparisons: vaccination with 500 attenuated cercariae versus infection with 500 normal cercariae; one versus three doses. Vaccinated mice were challenged with 120 normal parasites. Integration of PBMC and LN data from the infected group revealed early up-regulation of pathways associated with Th2 skewing and polarization of IgG antibody profiles. Additionally, hemostasis pathways were downregulated in infected mice, correlating with platelet reduction, potentially a mechanism to assist parasite migration through capillary beds. Conversely, up regulation of such mechanisms after vaccination may explain parasite blockade in the lungs. In contrast, a single exposure to attenuated parasites revealed early establishment of a Th1 bias (signaling of IL-1, IFN-γ; and Leishmania infection). Genes encoding chemokines and their receptors were more prominent in vaccinated mice, indicating an enhanced capacity for inflammation, potentially augmenting the inhibition of intravascular migration. Increasing the vaccinations from one to three did not dramatically elevate protection, but there was a clear shift towards antibody-mediated effectors. However, elements of the Th1 bias were still evident. Notable features after three vaccinations were markers of cytotoxicity (including IL-6 and NK cells) together with growth factors and their receptors (FGFR/VEGF/EGF) and the apoptosis pathway. Indeed, there is evidence for the development of anergy after three vaccinations, borne out by the limited responses detected in samples after challenge. We infer that persistence of a Th1 response puts a limit on expression of antibody-mediated mechanisms. This feature may explain the failure of multiple doses to drive protection towards sterile immunity. We suggest that the secretions of lung stage parasites would make a novel cohort of antigens for testing in protection experiments.

The cytosolic tryparedoxin peroxidase from Trypanosoma cruzi induces a pro-inflammatory Th1 immune response in a peroxidatic cysteine-dependent manner.

Trypanosoma cruzi cytosolic tryparedoxin peroxidase (c-TXNPx) is a 2-Cys peroxiredoxin (Prx) with an important role in detoxifying host cell oxidative molecules during parasite infection. c-TXNPx is a virulence factor, as its overexpression enhances parasite infectivity and resistance to exogenous oxidation. As Prxs from other organisms possess immunomodulatory properties, we studied the effects of c-TXNPx in the immune response and analysed whether the presence of the peroxidatic cysteine is necessary to mediate these properties. To this end, we used a recombinant c-TXNPx and a mutant version (c-TXNPxC52S) lacking the peroxidatic cysteine. We first analysed the oligomerization profile, oxidation state and peroxidase activity of both proteins by gel filtration, Western blot and enzymatic assay, respectively. To investigate their immunological properties, we analysed the phenotype and functional activity of macrophage and dendritic cells and the T-cell response by flow cytometry after injection into mice. Our results show that c-TXNPx, but not c-TXNPxC52S, induces the recruitment of IL-12/23p40-producing innate antigen-presenting cells and promotes a strong specific Th1 immune response. Finally, we studied the cellular and humoral immune response developed in the context of parasite natural infection and found that only wild-type c-TXNPx induces proliferation and high levels of IFN-γ secretion in PBMC from chronic patients without demonstrable cardiac manifestations. In conclusion, we demonstrate that c-TXNPx possesses pro-inflammatory properties that depend on the presence of peroxidatic cysteine that is essential for peroxidase activity and quaternary structure of the protein and could contribute to rational design of immune-based strategies against Chagas disease.

Leishmania infantum amastin protein incorporated in distinct adjuvant systems induces protection against visceral leishmaniasis.

The control measures against visceral leishmaniasis (VL) include a precise diagnosis of disease, the treatment of human cases, and reservoir and vector controls. However, these are insufficient to avoid the spread of the disease in specific countries worldwide. As a consequence, prophylactic vaccination could be interesting, although no effective candidate against human disease is available. In the present study, the Leishmania infantum amastin protein was evaluated regarding its immunogenicity and protective efficacy against experimental VL. BALB/c mice immunized with subcutaneous injections of the recombinant protein with or without liposome/saponin (Lip/Sap) as an adjuvant. After immunization, half of the animals per group were euthanized and immunological evaluations were performed, while the others were challenged with L. infantum promastigotes. Forty-five days after infection, the animals were euthanized and parasitological and immunological evaluations were performed. Results showed the development of a Th1-type immune response in rAmastin-Lip and rAmastin-Sap/vaccinated mice, before and after infection, which was based on the production of protein and parasite-specific IFN-γ, IL-12, GM-CSF, and nitrite, as well as the IgG2a isotype antibody. CD4+ T cells were mainly responsible for IFN-γ production in vaccinated mice, which also presented significant reductions in parasitism in their liver, spleen, draining lymph nodes, and bone marrow. In addition, PBMC cultures of treated VL patients and healthy subjects stimulated with rAmastin showed lymphoproliferation and higher IFN-γ production. In conclusion, the present study shows the first case of an L. infantum amastin protein associated with distinct delivery systems inducing protection against L. infantum infection and demonstrates an immunogenic effect of this protein in human cells.

Toll-Like Receptor 3-TRIF Pathway Activation by Neospora caninum RNA Enhances Infection Control in Mice.

Neospora caninum is a protozoan parasite closely related to Toxoplasma gondii and has been studied for causing neuromuscular disease in dogs and abortions in cattle. It is recognized as one of the main transmissible causes of reproductive failure in cattle and consequent economic losses to the sector. In that sense, this study aimed to evaluate the role of Toll-like receptor 3 (TLR3)-TRIF-dependent resistance against N. caninum infection in mice. We observed that TLR3-/- and TRIF-/- mice presented higher parasite burdens, increased inflammatory lesions, and reduced production of interleukin 12p40 (IL-12p40), tumor necrosis factor (TNF), gamma interferon (IFN-γ), and nitric oxide (NO). Unlike those of T. gondii, N. caninum tachyzoites and RNA recruited TLR3 to the parasitophorous vacuole (PV) and translocated interferon response factor 3 (IRF3) to the nucleus. We also observed that N. caninum upregulated the expression of TRIF in murine macrophages, which in turn upregulated IFN-α and IFN-ß in the presence of the parasite. Furthermore, TRIF-/- infected macrophages produced lower levels of IL-12p40, while exogenous IFN-α replacement was able to completely restore the production of this key cytokine. Our results show that the TLR3-TRIF signaling pathway enhances resistance against N. caninum infection in mice, since it improves Th1 immune responses that result in controlled parasitism and reduced tissue inflammation, which are hallmarks of the disease.

Intestinal parasites infection: protective effect in rheumatoid arthritis?

Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease, with a progressive course, characterized by chronic synovitis that may evolve with deformities and functional disability, and whose early treatment minimizes joint damage. Its etiopathogenesis is not fully elucidated but comprises immunologic responses mediated by T helper cells (Th1). An apparent minor severity of RA in patients from regions with lower income could be associated with a higher prevalence of gut parasites, especially helminths. Strictly, a shift in the immune response toward the predominance of T helper cells (Th2), due to the chronic exposure to helminths, could modulate negatively the inflammation in RA patients, resulting in lower severity/joint injury. The interaction between the immunological responses of parasitic helminths in rheumatoid arthritis patients is the purpose of this paper.

Intestinal parasites infection: protective effect in rheumatoid arthritis? / Parasitoses intestinais: efeito protetor na artrite reumatoide?

Abstract Rheumatoid arthritis (RA) is a systemic autoimmune inflammatory disease, with a progressive course, characterized by chronic synovitis that may evolve with deformities and functional disability, and whose early treatment minimizes joint damage. Its etiopathogenesis is not fully elucidated but comprises immunologic responses mediated by T helper cells (Th1). An apparent minor severity of RA in patients from regions with lower income could be associated with a higher prevalence of gut parasites, especially helminths. Strictly, a shift in the immune response toward the predominance of T helper cells (Th2), due to the chronic exposure to helminths, could modulate negatively the inflammation in RA patients, resulting in lower severity/joint injury. The interaction between the immunological responses of parasitic helminths in rheumatoid arthritis patients is the purpose of this paper.

Resumo A artrite reumatoide (AR) é uma doença inflamatória autoimune, sistêmica, de curso progressivo, caracterizada por exuberante sinovite crônica, que pode gerar deformidades e incapacidade funcional, cujo tratamento precoce minimiza o dano às juntas. Sua etiopatogenia ainda não está completamente elucidada, mas compreende respostas imunológicas com a participação de células T auxiliares (Th1). Uma aparente menor gravidade da AR em pacientes de regiões com menor renda poderia estar associada a maior prevalência de parasitoses intestinais, especialmente as helmintíases. A rigor, um desvio na resposta imune para o predomínio de células T auxiliares (Th2), decorrente da exposição crônica a helmintos, modularia negativamente a inflamação em doentes com AR, e levaria a menor gravidade e dano articular. A revisão de aspectos da influência da reposta imunológica nas parasitoses intestinais, especialmente as helmintíases, em pacientes com artrite reumatoide é o objetivo desse trabalho.

Crucial role for T cell-intrinsic IL-18R-MyD88 signaling in cognate immune response to intracellular parasite infection.

MyD88 is the main adaptor molecule for TLR and IL-1R family members. Here, we demonstrated that T-cell intrinsic MyD88 signaling is required for proliferation, protection from apoptosis and expression of activation/memory genes during infection with the intracellular parasite Trypanosoma cruzi, as evidenced by transcriptome and cytometry analyses in mixed bone-marrow (BM) chimeras. The lack of direct IL-18R signaling in T cells, but not of IL-1R, phenocopied the absence of the MyD88 pathway, indicating that IL-18R is a critical MyD88-upstream pathway involved in the establishment of the Th1 response against an in vivo infection, a presently controvert subject. Accordingly, Il18r1-/- mice display lower levels of Th1 cells and are highly susceptible to infection, but can be rescued from mortality by the adoptive transfer of WT CD4+ T cells. Our findings establish the T-cell intrinsic IL-18R/MyD88 pathway as a crucial element for induction of cognate Th1 responses against an important human pathogen.

Receptor Antagonist of IL-13 Exerts a Potential Negative Regulation During Early Infection of Human Schistosomiasis.

The pathology of schistosomiasis is associated with the formation of granulomas, and this process is associated with liver fibrosis. Studies indicate that Th1 cytokines reduce fibrosis in schistosomiasis, while Th2 cytokines play a part in the progression of fibrosis, and IL-13 has a critical role in this process. The IL-13Rα2 receptor, known as a 'receptor antagonist' binds with high affinity to IL-13, and studies have identified that this plays a part in reducing fibrosis and the size of granulomas. The objective of this study was to evaluate the function of IL-13Rα2 and cellular immune response in hepatic fibrosis. A negative correlation between IL-13Rα2 and IL-13 was found, suggesting an increase in cytokine in early fibrosis. Initially, a negative correlation between IFN-γ and IL-13 was found in patients without fibrosis, and subsequently, this correlation was found to be positive in patients with severe fibrosis, thereby highlighting a new mechanism for regulating the progress of periportal fibrosis. There was a positive correlation between the profiles of Th1 and Th2 cytokines, suggesting the presence of both responses, thus regulating the disease. The results contribute to a better understanding of the immune mechanisms that control the process of hepatic fibrogenesis in schistosomiasis in humans.

Toll-like receptor 9 signaling in dendritic cells regulates neutrophil recruitment to inflammatory foci following Leishmania infantum infection.

Leishmania infantum is a protozoan parasite that causes visceral leishmaniasis (VL). This infection triggers dendritic cell (DC) activation through the recognition of microbial products by Toll-like receptors (TLRs). Among the TLRs, TLR9 is required for DC activation by different Leishmania species. We demonstrated that TLR9 is upregulated in vitro and in vivo during infection. We show that C57BL/6 mice deficient in TLR9 expression (TLR9(-/-) mice) are more susceptible to infection and display higher parasite numbers in the spleen and liver. The increased susceptibility of TLR9(-/-) mice was due to the impaired recruitment of neutrophils to the infection foci associated with reduced levels of neutrophil chemoattractants released by DCs in the target organs. Moreover, both Th1 and Th17 cells were also committed in TLR9(-/-) mice. TLR9-dependent neutrophil recruitment is mediated via the MyD88 signaling pathway but is TIR domain-containing adapter-inducing interferon beta (TRIF) independent. Furthermore, L. infantum failed to activate both plasmacytoid and myeloid DCs from TLR9(-/-) mice, which presented reduced surface costimulatory molecule expression and chemokine release. Interestingly, neutrophil chemotaxis was affected both in vitro and in vivo when DCs were derived from TLR9(-/-) mice. Our results suggest that TLR9 plays a critical role in neutrophil recruitment during the protective response against L. infantum infection that could be associated with DC activation.

Plasmodium chabaudi limits early Nippostrongylus brasiliensis-induced pulmonary immune activation and Th2 polarization in co-infected mice.

BACKGROUND: Larvae of several common species of parasitic nematodes obligately migrate through, and often damage, host lungs. The larvae induce strong pulmonary Type 2 immune responses, including T-helper (Th)2 cells as well as alternatively activated macrophages (AAMphi) and associated chitinase and Fizz/resistin family members (ChaFFs), which are thought to promote tissue repair processes. Given the prevalence of systemic or lung-resident Type 1-inducing pathogens in geographical areas in which nematodes are endemic, we wished to investigate the impact of concurrent Type 1 responses on the development of these Type 2 responses to nematode larval migration. We therefore infected BALB/c mice with the nematode Nippostrongylus brasiliensis, in the presence or absence of Plasmodium chabaudi chabaudi malaria parasites. Co-infected animals received both infections on the same day, and disease was assessed daily before immunological measurements were taken at 3, 5, 7 or 20 days post-infection. RESULTS: We observed that the nematodes themselves caused transient loss of body mass and red blood cell density, but co-infection then slightly ameliorated the severity of malarial anaemia. We also tracked the development of immune responses in the lung and thoracic lymph node. By the time of onset of the adaptive immune response around 7 days post-infection, malaria co-infection had reduced pulmonary expression of ChaFFs. Assessment of the T cell response demonstrated that the Th2 response to the nematode was also significantly impaired by malaria co-infection. CONCLUSION: P. c. chabaudi co-infection altered both local and lymph node Type 2 immune activation due to migration of N. brasiliensis larvae. Given recent work from other laboratories showing that N. brasiliensis-induced ChaFFs correlate to the extent of long-term lung damage, our results raise the possibility that co-infection with malaria might alter pulmonary repair processes following nematode migration. Further experimentation in the co-infection model developed here will reveal the longer-term consequences of the presence of both malaria and helminths in the lung.

Schistosoma mansoni infection modulates the immune response against allergic and auto-immune diseases.

Chronic Schistosoma mansoni infection leads to a type 2-immune response with increased production of interleukin (IL-10). Evidence indicates chronic exposure to S. mansoni down regulates the type 1 immune response and prevents the onset of Th1-mediated diseases such as multiple sclerosis, diabetes mellitus and Crohn's disease. Furthermore, our own studies have revealed that chronic exposure to S. mansoni also down regulates atopic disease, Th2-mediated diseases. Our studies show an inverse association between the skin prick test reactivity and infection with S. mansoni and show the severity of asthma is reduced in subjects living in an endemic area of S. mansoni. Moreover, we hypothesize the mechanisms involved in the modulation of inflammatory response in atopic individuals, is likely dependent on IL-10 production, an anti-inflammatory cytokine elevated during helminth infections. Patients with asthma and helminth infections produced less IL-5 than patients with asthma without helminth infections, and this down regulation could, in part, be mediated by IL-10. In conclusion, helminthic infections, through induction of regulatory mechanisms, such as IL-10 production, are able to modulate the inflammatory immune response involved in the pathology of auto-immune and allergic disease.

Cysteine protease B of Leishmania mexicana inhibits host Th1 responses and protective immunity.

C3H mice infected with Leishmania mexicana fail to develop a protective Th1 response, and are unable to cure. In this study, we show that L. mexicana cysteine proteases suppress the antileishmanial immune response. Previous studies demonstrated that deletion of the entire multicopy cysteine protease B (CPB) gene array in L. mexicana is associated with decreased parasite virulence, potentially attributable to factors related to parasite fitness rather than to direct effects on the host immune response. We now show that C3H mice infected with the L. mexicana deletion mutant (Deltacpb) initially develop lesions that grow at rates comparable to those of wild-type L. mexicana-infected mice. However, in contrast to controls, Deltacpb-induced lesions heal with an accompanying Th1 immune response. Lesion resolution was Th1 dependent, as Deltacpb-infected IL-12p40(-/-) and STAT4(-/-) mice developed high parasite burdens and progressive disease. Moreover, when L. major was transfected with a cosmid expressing multiple L. mexicana CPB genes, this parasite induced a significantly lower IFN-gamma response compared with wild-type L. major. These data indicate that cysteine proteases of L. mexicana are critical in suppressing protective immune responses and that inhibition of CPB may prove to be a valuable immunomodulatory strategy for chronic forms of leishmaniasis.

The Leishmania mexicana cysteine protease, CPB2.8, induces potent Th2 responses.

We have previously identified that Leishmania mexicana cysteine proteases (CPs) are virulence factors. We have now produced a recombinant L. mexicana CP, CPB2.8, which has similar enzymatic activity to native enzyme. Inoculation of CPB2.8 (< or =5 microg) into the footpads of BALB/c mice not only up-regulated mRNA transcripts for IL-4 and IL-4 production in the draining popliteal lymph nodes, but also polarized splenocyte anti-CD3 stimulated responses toward a Th2 bias as measured by increased IL-5 production compared with controls. In agreement with promoting a Th2 response, CPB2.8 also induced strong specific IgE responses in treated mice as well as increasing whole IgE levels. Inhibition of the enzyme activity of CPB2.8 by treatment with E-64 ablated the enzyme's ability to induce IgE. Significantly, infection of mice with CPB-deficient parasites failed to stimulate production of IgE, unlike infection with wild-type parasites. Furthermore, enzymatically active (<0.1 U/ml) but not E-64-inactivated CPB2.8 was able to proteolytically cleave CD23 and CD25, although not B220 or CD4 from murine lymphocytes. These properties are similar to those demonstrated by the house dust mite allergen Der p I and provide an explanation for the immunomodulatory activity of the CPB2.8 virulence factor. Vaccination with CPB2.8 enhanced L. mexicana lesion growth compared with control animals. Nevertheless, vaccination with IL-12 and CPB2.8 resulted in a degree of protection associated with inhibition of lesion growth and a Th1 response. Thus, CPB2.8 is a potent Th2-inducing molecule capable of significant vaccine potential if administered with a suitable adjuvant.

Identification of a 30 kDa antigen from leishmania (L.) chagasi amastigotes implicated in protective cellular reponses in a murine model.

An antigen of apparent molecular mass of 30 kDa, termed p30, was purified from Leishmania (L.) chagasi amastigotes after separation of parasite extracts by sodium dodecyl sulfate-polyacrylamide gel eletroctrophoresis followed by electroelution. The use of the purified antigen in lymphocyte cultures from BALB/c mice previously immunised with L. (L.) chagasi amastigotes led to high levels of proliferation. Animal immunisation with p30 plus complete Freund's adjuvant either by subcutaneous or intraperitoneal route led to comparable antigenic stimulation. Similar stimulation indices induced by p30 were also obtained when animals were immunised with Corynebacterium parvum as adjuvant by the intraperitoneal route. Detection of IL-2 and IFN-gamma in the supernatants from lymphocytes stimulated by p30 and inhibition of the production of these lymphokines in the presence of anti-CD4 strongly indicated the involvement of the Th1 subset in the responses elicited by p30 antigen. Immunisation of BALB/c mice with p30 provided partial protection against challenge with L. (L.) chagasi amastigotes, indicating a protective role for p30 and that Th1 can be related to accquired resistance to visceral leishmaniasis in a murine model. Further characterisation studies were performed by the use of a monoclonal antibody directed to a cysteine proteinase of 30 kDa from L. (L.) amazonensis amastigotes. Despite the cross-reactivity presented by p30 from both Leishmania species, the p30 from L. (L.) chagasi amastigotes lacks proteolytic activity.

Virulent or avirulent (dhfr-ts-) Leishmania major elicit predominantly a type-1 cytokine response by human cells in vitro.

In this study we have compared the immune response of normal human cells cultured in vitro to two virulent strains of Leishmania major (CC1 and LV39), and to an avirulent vaccine strain (dhfr-ts-) made by targeted deletion of the essential gene DHFR-TS. We utilized an in vitro system in which naive T cells from normal human donors were primed with autologous Leishmania-infected macrophages. All three parasites infected macrophages and transformed into amastigotes within the cells. However, whereas LV39 and CC1 replicated in macrophages, dhfr-ts- did not. When peripheral blood lymphocytes (PBL) were stimulated with autologous macrophages infected with any of the three parasites, the lymphocytes produced a type-1-biased cytokine response. Finally, addition of IL-12 during the first stimulation period increased the production of interferon-gamma but decreased IL-5 secretion. On the other hand, anti-IL-12 resulted in the opposite effect.

Sex-determined resistance against Leishmania mexicana is associated with the preferential induction of a Th1-like response and IFN-gamma production by female but not male DBA/2 mice.

Female DBA/2 mice are relatively resistant to infection with Leishmania mexicana compared with male mice. Following subcutaneous infection with 5 x 10(6) L. mexicana, amastigotes lesion growth in male and female DBA/2 mice was measured and the developing immune responses were monitored both in vitro and in vivo. Over the 10 week duration of the experiment all male DBA/2 mice developed rapidly growing non-healing lesions while female mice either developed no lesions whatsoever or developed smaller slower growing lesions than males. Both male and female mice produced parasite specific IgG2a during the course of the disease. However, significant titres of parasite specific IgG1 antibodies could be detected only in male mice indicating a Th2-influenced response in this sex. Furthermore, female mice, unlike male mice, developed significant parasite induced cutaneous delayed-type hypersensitivity footpad responses, indicating a Th1-influenced response in female mice. Although both male and female DBA/2 mice infected with L. mexicana displayed a significant increase in the number of cells in their draining lymph nodes at week 10 post-infection, no significant differences could be observed in the numbers of CD4+, CD8 + T cells as well as B cells between male and female DBA/2 mice. However. following in vitro stimulation, the lymph node cells from female mice displayed significantly higher antigen specific proliferative responses than the males and produced significant amounts of IFN-gamma which could not be detected in the equivalent culture supernatants from male mice. There were no significant differences in the levels of Th2-associated cytokines IL-4 and IL-5, produced by the lymph node cells of both sexes. Treatment of female DBA/2 mice with IFN-gamma neutralizing antibody following L. mexicana infection resulted in lesion growth equivalent to male mice. Conversely, intralesional injections of murine recombinant IFN-gamma significantly inhibited lesion growth in male mice.

The debate over the effector function of eosinophils in helminth infection: new evidence from studies on the regulation of vaccine immunity by IL-12

The production of Th1-type cytokines is associated with strong cell-mediated immunity while Th2-type cytokines are typically involved in the generation of humoral immune responses. In mice vaccinated a single time (1x) with attenuated cercariae of Schistosoma mansoni, the immunity induced is highly dependent on CD4+ T cells and IFN-gamma. In contrast, mice vaccinated multiple times (3x) have decreased IFN-gamma expression, develop a more dominant Th2-type cytokine response as well as protective antibodies which can passively transfer immunity to naive recipients. Previously, we demonstrated the ability of IL-12, a potent IFN-gamma-inducing cytokine to enhance (1x) schistosome cell-mediated immunity when administered during the period of immunization. More recently, we asked what effects IL-12 would have on the development humoral-based immunity. While multiply-immunized/saline-treated mice demonstrated a 70-80 per cent reduction in parasite burden, 3x/IL-12-vaccinated animals displayed an even more striking >90 per cent reduction in challenge infection, which many mice in the later group demonstrating complete protection. Analysis of pulmonary cytokine mRNA responses demonstrated that control challenged mice elicited a dominant Th2-type response, 3x/saline-vaccinated produced a mixed Th1/Th2-type cytokine response, while 3x/saline-vaccinated produced a mixed Th1/Th2-type cytokine response, while 3x/IL-12 immunized animals displayed a dominant Th1-type response. The IL-12-treated group also showed a marked reduction in total serum IgE and tissue eosinophilia while SWAP-specific IgG2a and IgG2b Abs elevated. Interestingly, animals vaccinated with IL-12 also showed a highly significant increase in total Ig titers specific for IrV-5, a known protective antigen. More importantly, 3x/IL-12 serum alone, when transferred to naive mice reduced worm burdens by over 60 per cent while 3x/saline serum transferred significantly less protection. Nevertheless, animals vaccinated in the presence of IL-12 also develop macrophages with enhanced nitric oxide dependent killing activity against the parasites. Together, these observations suggest that IL-12, initially described as an adjuvant for cell-mediated immunity, may also be used as an adjuvant for promoting both humoral and cell-mediated protective responses.