Homologues of human macrophage migration inhibitory factor from a parasitic nematode. Gene cloning,protein activity,and crystal structure

Cytokines are the molecular messengers of the vertebrate immune system, coordinating the local and systemic immune responses to infective organisms. We report here functional and structural data on cytokine-like proteins from a eukaryotic pathogen. Two homologues of the human cytokine macrophage migration inhibitory factor (MIF) have been isolated from the parasitic nematode Brugia malayi. Both molecules (Bm-MIF-1 and Bm-MIF-2) show parallel functions to human MIF. They are chemotactic for human monocytes and activate them to produce IL-8, TNF-alpha, and endogenous MIF. The human and nematode MIF homologues share a tautomerase enzyme activity, which is in each case abolished by the mutation of the N-terminal proline residue. The crystal structure of Bm-MIF-2 at 1.8-A resolution has been determined, revealing a trimeric assembly with an inner pore created by beta-stranded sheets from each subunit. Both biological activity and crystal structure reveal remarkable conservation between a human cytokine and its parasite counterpart despite the considerable phylogenetic divide among these organisms. The strength of the similarity implies that MIF-mediated pathways play an important role in nematode immune evasion strategies.     

Protective role of purified cysteine proteinases against Fasciola gigantica infection in experimental animals

Fascioliasis is one of the public health problems in the world. Cysteine proteinases (CP) released by Fasciola gigantica play a key role in parasite feeding, migration through host tissues, and in immune evasion. There has been some evidence from several parasite systems that proteinases might have potential as protective antigens against parasitic infections. Cysteine proteinases were purified and tested in vaccine trials of sheep infected with the liver fluke. Multiple doses (2 mg of CP in Freund's adjuvant followed by 3 booster doses 1 mg each at 4 week intervals) were injected intramuscularly into sheep 1 week prior to infect orally with 300 F. gigantica metacercariae. All the sheep were humanely slaughtered 12 weeks after the first immunization. Changes in the worm burden, ova count, and humoral and cellular responses were evaluated. Significant reduction was observed in the worm burden (56.9%), bile egg count (70.7%), and fecel egg count (75.2%). Immunization with CP was also found to be associated with increases of total IgG, IgG(1), and IgG(2) (P<0.05). Data showed that the serum cytokine levels of pro-inflammatory cytokines, IL-12, IFN-γ, and TNF-α, revealed significant decreases (P<0.05). However, the anti-inflammatory cytokine levels, IL-10, TGF-β, and IL-6, showed significant increases (P<0.05). In conclusion, it has been found that CP released by F. gigantica are highly important candidates for a vaccine antigen because of their role in the fluke biology and host-parasite relationships.     

Brugia malayi: comparison of protective immune responses induced by Bm-alt-2 DNA, recombinant Bm-ALT-2 protein and prime-boost vaccine regimens in a jird model

Immunization of jirds with Bm-alt-2 elicited partial protection against challenge infection with the filarial parasite Brugia malayi. In this study, we initially compared the protective immune responses elicited following immunization with recombinant Bm-ALT-2 protein regimen and Bm-alt-2 DNA regimen. These studies showed that protein vaccination conferred approximately 75% protection compared to DNA vaccination that conferred only 57% protection. Analysis of the protective immune responses showed that the protein immunization promoted a Th2-biased response with an increase in IL-4, IL-5 and IgG1 responses, whereas, the DNA vaccine promoted a Th1-biased response with profound IFN-gamma and IgG2a responses. Since protein vaccination gave better results than DNA vaccination, we then wanted to evaluate whether a prime-boost vaccination that combined DNA prime and protein boost will significantly increase the protective responses induced by the protein vaccine. Our results suggest that prime-boost vaccination had no added advantage and was comparatively less effective (64% protection) than the Bm-ALT-2 protein alone vaccination. Prime boost vaccination generated mixed Th1/Th2 responses with a slightly diminished Th2 responses compared to protein vaccination. Thus, our results suggest that Bm-ALT-2 protein vaccination regimen may be slightly better than prime-boost vaccine regimen and the mechanism of protection appears to be largely mediated by a Th2-biased response.     

Blocking immune evasion as a novel approach for prevention and treatment of herpes simplex virus infection

Many microorganisms encode immune evasion molecules to escape host defenses. Herpes simplex virus type 1 glycoprotein gC is an immunoevasin that inhibits complement activation by binding complement C3b. gC is expressed on the virus envelope and infected cell surface, which makes gC potentially accessible to blocking antibodies. Mice passively immunized with gC monoclonal antibodies prior to infection were protected against herpes simplex virus challenge only if the gC antibodies blocked C3b binding. Mice treated 1 or 2 days postinfection with gC monoclonal antibodies that block C3b binding had less severe disease than control mice treated with nonimmune immunoglobulin G (IgG). Mice immunized with gC protein produced antibodies that blocked C3b binding to gC. Immunized mice were significantly protected against challenge by wild-type virus, but not against a gC mutant virus lacking the C3b binding domain, suggesting that protection was mediated by antibodies that target the gC immune evasion domain. IgG and complement from subjects immunized with an experimental herpes simplex virus glycoprotein gD vaccine neutralized far more mutant virus defective in immune evasion than wild-type virus, supporting the importance of immune evasion molecules in reducing vaccine potency. These results suggest that it is possible to block immune evasion domains on herpes simplex virus and that this approach has therapeutic potential and may enhance vaccine efficacy.     

Pulmonary inflammation induced by a recombinant Brugia malayi gamma-glutamyl transpeptidase homolog: involvement of humoral autoimmune responses

BACKGROUND: A major allergen from the lymphatic filarial parasite Brugia malayi implicated in the pathogenesis of tropical pulmonary eosinophilia (TPE) has recently been cloned and identified as the homolog of the membrane-bound mammalian enzyme gamma-glutamyl transpeptidase (gamma-GT). Patients with acute TPE show autoreactive antibodies against endogenous gamma-GT from the pulmonary epithelium. MATERIALS AND METHODS: Recombinant B. malayi gamma-GT, alone or adsorbed to aluminium hydroxide (AL), was used in a BALB/c mouse model to analyze its antigenic/allergenic potential, its potential to induce pulmonary inflammation, and its capacity to induce autoreacting antibodies. RESULTS: Mice immunized with B. malayi gamma-GT showed significant levels of gamma-GT-specific IgG1, IgG2a, IgG3, IgA, IgE antibodies, and mild blood eosinophilia, even in the absence of adjuvant. Intranasal challenge with B. malayi gamma-GT induced peribronchial and perivascular inflammation characterized by a mixed infiltrate of lymphocytes, neutrophils, eosinophils, and macrophages. Both IL-4 and IFN-gamma were detected in the peripheral blood and in the bronchoalveolar lavage fluid of immunized and intranasally challenged mice. Histological analysis of murine lungs using affinity-purified antibodies from mice immunized with the parasite's gamma-GT revealed the presence of autoimmune antibodies against pulmonary epithelium. Western blot analysis identified the 55 kDa heavy chain subunit of the murine gamma-GT as the target of autoreactive/crossreacting antibodies. CONCLUSION: Our data from the in vivo mouse model demonstrate the potent allergenicity/antigenicity of B. malayi gamma-GT, and its capacity to induce pulmonary inflammation upon intranasal challenge. This leads to breakdown of tolerance against endogenous murine gamma-GT. Thus, humoral autoimmunity against the airways epithelium may contribute to the pathogenesis of TPE.     

Immunogenicity and protective potential of a bacterially expressed recombinant dihydrolipoamide succinyltransferase (rE2o) of Brucella abortus in BALB/c mice

Brucellosis is one of the world's major zoonoses. No vaccine is available for the prevention of brucellosis in human. Efforts are needed to develop an effective, safe, stable, vaccine with long lasting immunity against human brucellosis. Here, we cloned and expressed recombinant dihydrolipoamide succinyltransferase (rE2o) of Brucella abortus in Escherichia coli and purified up to homogeneity by metal affinity chromatography. The purified rE2o is immunoreactive with brucellosis positive cattle sera. The immunogenicity and the protective potential of recombinant dihydrolipoamide succinyltransferase (rE2o) were evaluated in BALB/c mice with two different adjuvants i.e., Freund's and aluminium hydroxide gel. Mice were tested for humoral immune response by ELISA. Cell mediated immune response was tested by lymphocyte proliferation assay and cytokine profiling. The recombinant E2o (rE2o) generated high IgG antibody and its isotypes IgG1, and induced significant production of INF-γ, IL-10 and IL-4 cytokines. The rE2o protein induced significant lymphoproliferation of splenocytes. Altogether, these results suggest that rE2o induces a mixed but a predominant Th2 type of immune response in BALB/c mice and provides partial protection against challenge with pathogenic Brucella abortus.     

A novel combination immunotherapy for cancer by IL-13Rα2-targeted DNA vaccine and immunotoxin in murine tumor models

Optimum efficacy of therapeutic cancer vaccines may require combinations that generate effective antitumor immune responses, as well as overcome immune evasion and tolerance mechanisms mediated by progressing tumor. Previous studies showed that IL-13Rα2, a unique tumor-associated Ag, is a promising target for cancer immunotherapy. A targeted cytotoxin composed of IL-13 and mutated Pseudomonas exotoxin induced specific killing of IL-13Rα2(+) tumor cells. When combined with IL-13Rα2 DNA cancer vaccine, surprisingly, it mediated synergistic antitumor effects on tumor growth and metastasis in established murine breast carcinoma and sarcoma tumor models. The mechanism of synergistic activity involved direct killing of tumor cells and cell-mediated immune responses, as well as elimination of myeloid-derived suppressor cells and, consequently, regulatory T cells. These novel results provide a strong rationale for combining immunotoxins with cancer vaccines for the treatment of patients with advanced cancer.     

Antibodies to the envelope glycoprotein of human T cell leukemia virus type 1 robustly activate cell-mediated cytotoxic responses and directly neutralize viral infectivity at multiple steps of the entry process

Infection of human cells by human T cell leukemia virus type 1 (HTLV-1) is mediated by the viral envelope glycoproteins. The gp46 surface glycoprotein binds to cell surface receptors, including heparan sulfate proteoglycans, neuropilin 1, and glucose transporter 1, allowing the transmembrane glycoprotein to initiate fusion of the viral and cellular membranes. The envelope glycoproteins are recognized by neutralizing Abs and CTL following a protective immune response, and therefore, represent attractive components for a HTLV-1 vaccine. To begin to explore the immunological properties of potential envelope-based subunit vaccine candidates, we have used a soluble recombinant surface glycoprotein (gp46, SU) fused to the Fc region of human IgG (sRgp46-Fc) as an immunogen to vaccinate mice. The recombinant SU protein is highly immunogenic and induces high titer Ab responses, facilitating selection of hybridomas that secrete mAbs targeting SU. Many of these mAbs recognize envelope displayed on the surface of HTLV-1-infected cells and virions and several of the mAbs robustly antagonize envelope-mediated membrane fusion and neutralize pseudovirus infectivity. The most potently neutralizing mAbs recognize the N-terminal receptor-binding domain of SU, though there is considerable variation in neutralizing proficiency of the receptor-binding domain-targeted mAbs. By contrast, Abs targeting the C-terminal domain of SU tend to lack robust neutralizing activity. Importantly, we find that both neutralizing and poorly neutralizing Abs strongly stimulate neutrophil-mediated cytotoxic responses to HTLV-1-infected cells. Our data demonstrate that recombinant forms of SU possess immunological features that are of significant utility to subunit vaccine design.     

IgG1 is pathogenic in Leishmania mexicana infection

There are >2 million new cases of leishmaniasis annually, and no effective vaccine has been developed to prevent infection. In murine infection, Leishmania mexicana, which lives intracellularly in host macrophages, has developed pathways to hijack host IgG to induce a suppressive IL-10 response through FcγRs, the cell-surface receptors for IgG. To guide vaccine development away from detrimental Ab responses, which can accompany attempts to induce cell-mediated immunity, it is crucial to know which isotypes of IgG are pathogenic in this infection. We found that IgG1 and IgG2a/c induce IL-10 from macrophages in vitro equally well but through different FcγR subtypes: IgG1 through FcγRIII and IgG2a/c through FcγRI primarily, but also through FcγRIII. In sharp contrast, mice lacking IgG1 develop earlier and stronger IgG2a/c, IgG3, and IgM responses to L. mexicana infection and yet are more resistant to the infection. Thus, IgG1, but not IgG2a/c or IgG3, is pathogenic in vivo, in agreement with prior studies indicating that FcγRIII is required for chronic disease. This calls into question the assumption that macrophages, which should secrete IL-10 in response to IgG1 and IgG2a/c immune complexes, are the most important source of IL-10 generated by IgG-FcγR engagement in L. mexicana infection. Further investigations are required to better determine the cell type responsible for this immunosuppressive FcγRIII-induced IL-10 pathway and whether IgG2a/c is protective.     

Proinflammatory cytokines dominate the early immune response to filarial parasites

Although the early human immune response to the infective-stage larvae (L3) of Brugia malayi has not been well-characterized in vivo (because of the inability to determine the precise time of infection), the consensus has been that it must involve a predominant Th2 environment. We have set up an in vitro system to study this early immune response by culturing PBMC from unexposed individuals with live L3 of B. malayi. After 24 h of culture, T cell responses were examined by flow cytometry and by quantitative real-time RT-PCR for multiple cytokines. T cells were activated early following exposure to L3 as indicated by up-regulation of surface markers CD69 and CD71. The frequency of T cells expressing proinflammatory Th1 cytokines (IFN-gamma, TNF-alpha, GM-CSF, IL-1alpha, and IL-8) but not Th2 cytokines (IL-4, IL-5, IL-6, IL-10, and IL-13) was significantly increased in response to L3. This T cell response occurred in both the CD4 and CD8 T cell compartment and was restricted to the effector/memory pool (CD45RO(+)). This T cell response was not due to LPS activity from the parasite or from its endosymbiont, Wolbachia; moreover, it required the presence of APC as well as direct contact with live L3. Real-time RT-PCR analysis of multiple cytokines in the T cells confirmed the increased expression of proinflammatory Th1 cytokines. Up-regulation of these cytokines suggests that the primary immune response to the live infective stage of the parasite is not predominantly Th2 in nature but rather dominated by a proinflammatory response.     

Reciprocal regulation of protein kinase C isoforms results in differential cellular responsiveness

Immunological homeostasis is often maintained by counteractive functions of two different cell types or two different receptors signaling through different intermediates in the same cell. One of these signaling intermediates is protein kinase C (PKC). Ten differentially regulated PKC isoforms are integral to receptor-triggered responses in different cells. So far, eight PKC isoforms are reported to be expressed in macrophages. Whether a single receptor differentially uses PKC isoforms to regulate counteractive effector functions has never been addressed. As CD40 is the only receptor characterized to trigger counteractive functions, we examined the relative role of PKC isoforms in the CD40-induced macrophage functions. We report that in BALB/c mouse macrophages, higher doses of CD40 stimulation induce optimum phosphorylation and translocation of PKCα, βI, βII, and ε whereas lower doses of CD40 stimulation activates PKCδ, ζ, and λ. Infection of macrophages with the protozoan parasite Leishmania major impairs PKCα, βI, βII, and ε isoforms but enhances PKCδ, ζ, and λ isoforms, suggesting a reciprocity among these PKC isoforms. Indeed, PKCα, βI, βII, and ε isoforms mediate CD40-induced p38MAPK phosphorylation, IL-12 expression, and Leishmania killing; PKCδ and ζ/λ mediate ERK1/2 phosphorylation, IL-10 production, and parasite growth. Treatment of the susceptible BALB/c mice with the lentivirally expressed PKCδ- or ζ-specific short hairpin RNA significantly reduces the infection and reinstates host-protective IFN-γ-dominated T cell response, defining the differential roles for PKC isoforms in immune homeostasis and novel PKC-targeted immunotherapeutic and parasite-derived immune evasion strategies.     

Leishmania donovani Infection of a Susceptible Host Results in Apoptosis of Th1-Like Cells: Rescue of Anti-Leishmanial CMI by Providing Th1-Specific Bystander Costimulation

A protective immune response against Leishmania donovani infection is mediated by T-helper type 1 (Th1) cells. Th1 induced cell-mediated immunity (CMI), as assessed by anti-leishmanial DTH response, is lost in a susceptible host such as BALB/c mice. Although the impaired Th1 function eventuates in unhindered parasite growth and in manifestation of the susceptible phenotype, the mechanism of down-regulation of the Th1 function is yet to be elucidated. Here, we provide evidence that the parasite downregulates the expression of a Th1-specific costimulatory molecule, M150, on the surface of infected BALB/c mice-derived macrophages. Th cells are rendered unresponsive to anti-CD3 Ab-mediated stimulation after interaction with infected macrophages. The anergized T cells produce much less IL-2, IL-4 and IFN-γ compared to those T cells which were costimulated using normal macrophages. The defect in proliferation, anti-CD3 Ab induced unresponsiveness and IFN-γ but not IL-4 production can be restored by providing bystander costimulation through M150. These results not only unfold a novel immune evasion strategy used by the parasite but also clarify the mechanism of Th1 cell debilitation during the disease. Recovery of Th1 cytokine production by bystander costimulation through M150 may help in formulating a new strategy for the elimination of intracellular parasites.     

Vaccination with the Leishmania major ribosomal proteins plus CpG oligodeoxynucleotides induces protection against experimental cutaneous leishmaniasis in mice

In the present work we analyze the antigenicity of Leishmania major ribosomal proteins (LRP) in infected BALB/c mice. We show that BALB/c mice vaccinated with LRP in the presence of CpG oligodeoxynucleotides (CpG-ODN) were protected against the development of dermal pathology and showed a reduction in the parasite load after challenge with L. major. This protection was associated with the induction of an IL-12 dependent specific-IFN-gamma response mediated mainly by CD4(+) T cell, albeit a minor contribution of CD8(+) T cells cannot be ruled out. Induction of Th1 responses against LRP also resulted in a reversion of the Th2 responses associated with susceptibility. A marked reduction of IgG1 antibody titer against parasite antigens besides an impaired IL-4 and IL-10 cytokine production by parasite specific T cells was observed. In addition, we show that the administration of the LRP plus CpG-ODN preparation also conferred protection in the naturally resistant C57BL/6 mice. In this strain protection was associated with a LRP specific IFN-gamma production in lymph nodes draining the challenge site. We believe that these evolutionary conserved proteins, combined with adjuvants that favor Th1 responses, may be relevant components of a pan-Leishmania vaccine.     

Identification of a highly immunoreactive epitope of Brugia malayi TPx recognized by the endemic sera

Filarial thiordoxin peroxidase is a major antioxidant that plays a crucial role in parasite survival. Although Brugia malayi TPx has been shown to be a potential vaccine candidate, it shares 63% homology with its mammalian counterpart, limiting its use as a vaccine or drug target. In silico analysis of TPx sequence revealed a linear B epitope in the host's nonhomologous region. The peptide sequence (TPx peptide(27-48)) was synthesized, and its reactivity with clinical sera from an endemic region was analyzed. The peptide showed significantly high reactivity (P < 0.05) against the sera of putatively immune individuals compared to the nonendemic control sera. It also showed high reactivity against the sera of patients with chronic pathology and patent infection. The high reactivity of the peptide with endemic immune sera equivalent to that of whole protein shows that it forms a dominant B epitope of TPx protein and thus could be utilized for incorporation into a multiepitope vaccine construct for filariasis.     

CD8+ T lymphocytes are not required for murine resistance to human filarial parasites.

Mice are resistant to the establishment of infection with the nematode parasite Brugia malayi, an etiologic agent of human lymphatic filariasis. We have recently shown that T and B lymphocyte-deficient C.B.-17 scid/scid mice are permissive for infection with this parasite, whereas coisogenic C.B.-17+/+ mice are resistant. This observation suggests that T and B lymphocytes that comprise the antigen-specific immune system orchestrate murine resistance to B. malayi. In order to define the component of the antigen-specific immune response that is responsible for this resistance, we have tested the susceptibility of beta 2M-/- mice to infection with B. malayi L3 larvae. These mice are homozygous for insertional disruption of their B2m genes, which encode beta 2-microglobulin, the small subunit of the major histocompatibility (MHC) antigens. They do not express beta 2-microglobulin and, as a consequence, fail to express the class I major histocompatibility antigens, and they do not develop the CD8+ class I MHC-restricted cytotoxic T cell subset. We find that these mice are completely resistant to B. malayi, indicating that the CD8+ T lymphocyte subset is not an obligate requirement for murine resistance to human filarial parasites.     

Setaria cervi: immunoprophylactic potential of glutathione-S-transferase against filarial parasite Brugia malayi

Glutathione-S-transferase (GST) has been detected in the adult female Setaria cervi, a bovine filarial parasite. The role of S. cervi GST antigen in inducing immunity in the host against Brugia malayi microfilariae and infective larvae was studied by in vitro antibody dependent cell mediated reaction as well as in situ inoculation of filarial parasites within a microchamber in Mastomys. The immune sera from glutathione-S-transferase immunized Mastomys promoted the adherence of peritoneal exudate cells to B. malayi microfilariae and infective larvae in vitro inducing 80.7 and 77.6% cytotoxicity, respectively in 72 h. In the microchambers implanted in the immunized Mastomys host cells could migrate and adhere to the microfilariae and infective larvae and induced 77.8 and 75% cytotoxicity to B. malayi microfilariae and infective larvae in 72 h, respectively. These results suggest that native GST from S. cervi is effective in inducing protection against heterologous B. malayi filarial parasite and thus has potential in immunoprophylaxis.     

Harbouring in the brain: A focus on immune evasion mechanisms and their deleterious effects in malaria and human African trypanosomiasis

Malaria and human African trypanosomiasis represent the two major tropical vector-transmitted protozoan infections, displaying different prevalence and epidemiological patterns. Death occurs mainly due to neurological complications which are initiated at the blood-brain barrier level. Adapted host-immune responses present differences but also similarities in blood-brain barrier/parasite interactions for these diseases: these are the focus of this review. We describe and compare parasite evasion mechanisms, the initiating mechanisms of central nervous system pathology and major clinical and neuropathological features. Finally, we highlight the common immune mediated mechanisms leading to brain involvement. In both diseases neurological damage is caused mainly by cytokines (interferon-gamma, tumour necrosis factor-alpha and IL-10), nitric oxide and endothelial cell apoptosis. Such a comparative analysis is expected to be useful in the comprehension of disease mechanisms, which may in turn have implications for treatment strategies.     

Suppression of lethal Plasmodium yoelii malaria following protective immunization requires antibody-, IL-4-, and IFN-gamma-dependent responses induced by vaccination and/or challenge infection

Immunization with Plasmodium yoelii merozoite surface protein (PyMSP)-8 protects mice from lethal malaria but does not prevent infection. Using this merozoite surface protein-based vaccine model, we investigated vaccine- and infection-induced immune responses that contribute to protection. Analysis of prechallenge sera from rPyMSP-8-immunized C57BL/6 and BALB/c mice revealed high and comparable levels of Ag-specific IgG, but differences in isotype profile and specificity for conformational epitopes were noted. As both strains of mice were similarly protected against P. yoelii, we could not correlate vaccine-induced responses with protection. However, passive immunization studies suggested that protection resulted from differing immune responses. Studies with cytokine-deficient mice showed that protection was induced by immunization of C57BL/6 mice only when IL-4 and IFN-gamma were both present. In BALB/c mice, the absence of either IL-4 or IFN-gamma led to predictable shifts in the IgG isotype profile but did not reduce the magnitude of the Ab response induced by rPyMSP-8 immunization. Immunized IL-4-/- BALB/c mice were solidly protected against P. yoelii. To our surprise, immunized IFN-gamma-/- BALB/c mice initially controlled parasite growth but eventually succumbed to infection. Analysis of cytokine production revealed that P. yoelii infection induced two distinct peaks of IFN-gamma that correlated with periods of controlled parasite growth in intact, rPyMSP-8-immunized BALB/c mice. Maximal parasite growth occurred during a period of sustained TGF-beta production. Combined, the data indicate that induction of protective responses by merozoite surface protein-based vaccines depends on IL-4 and IFN-gamma-dependent pathways and that vaccine efficacy is significantly influenced by host responses elicited upon infection.     

A combination of two Brugia malayi filarial vaccine candidate antigens (BmALT-2 and BmVAH) enhances immune responses and protection in jirds

In this study filarial recombinant protein or DNA vaccine constructs encoding BmALT-2 and BmVAH as single or as cocktail antigens were evaluated. Male jirds were immunized intramuscularly with DNA vaccine constructs or were immunized intraperitoneally with protein vaccine. The single and bicistronic DNA constructs induced substantial interferon-γ responses in spleen cells; antigen-specific responses were higher following immunization with the bicistronic cocktail construct and evoked a significant protective response of 57% in jirds challenged with Brugia malayi that was similar in the antibody-dependent cellular cytotoxicity (ADCC) assay and micropore chamber experiment. The cocktail protein vaccines induced a mixture of IgG2a (Th1) and IgG1 (Th2) responses with 80% protective response when challenged with B. malayi infective larvae. However, the single protein vaccine rALT-2 induced Th2 (IgG1/IgG3) with a 70% protective response and rVAH induced Th1 (IgG2a) with a lower proliferative response with 60% protection following challenge with B. malayi infective larvae. These results suggest that filarial cocktail protein vaccines are able to elicit substantial immune and protective responses when compared with single antigen vaccination in suitably vaccinated jirds.     

Protective immunity using recombinant human IL-12 and alum as adjuvants in a primate model of cutaneous leishmaniasis.

Protection from cutaneous leishmaniasis, a chronic ulcerating skin lesion affecting millions, has been achieved historically using live virulent preparations of the parasite. Killed or recombinant Ags that could be safer as vaccines generally require an adjuvant for induction of a strong Th1 response in murine models. Murine rIL-12 as an adjuvant with soluble Leishmania Ag has been shown to protect susceptible mice. We used 48 rhesus macaques to assess the safety, immunogenicity, and efficacy of a vaccine combining heat-killed Leishmania amazonensis with human rIL-12 (rhIL-12) and alum (aluminum hydroxide gel) as adjuvants. The single s.c. vaccination was found to be safe and immunogenic, although a small transient s.c. nodule developed at the site. Groups receiving rhIL-12 had an augmented in vitro Ag-specific IFN-gamma response after vaccination, as well as increased production of IgG. No increase in IL-4 or IL-10 was found in cell culture supernatants from either control or experimental groups. Delayed hypersensitivity reactions were not predictive of protection. Intradermal forehead challenge infection with 107 metacyclic L. amazonensis promastigotes at 4 wk demonstrated protective immunity in all 12 monkeys receiving 2 microgram rhIL-12 with alum and Ag. Partial efficacy was seen with lower doses of rhIL-12 and in groups lacking either adjuvant. Thus, a single dose vaccine with killed Ag using rhIL-12 and alum as adjuvants was safe and fully effective in this primate model of cutaneous leishmaniasis. This study extends the murine data to primates, and provides a basis for further human trials.