Protective immunity against Leishmania major induced by Leishmania tropica infection of BALB/c mice

Leishmania (L.) tropica is a causative agent of human cutaneous and viscerotropic leishmaniasis. Immune response to L. tropica in humans and experimental animals are not well understood. We previously established that L. tropica infection induces partial protective immunity against subsequent challenge infection with Leishmania major in BALB/c mice. Aim of the present study was to study immunologic mechanisms of protective immunity induced by L. tropica infection, as a live parasite vaccine, in BALB/c mouse model. Mice were infected by L. tropica, and after establishment of the infection, they were challenged by L. major. Our findings shows that L. tropica infection resulted in protection against L. major challenge in BALB/c mice and this protective immunity is associated with: (1) a DTH response, (2) higher IFN-γ and lower IL-10 response at one week post-challenge, (3) lower percentage of CD4⁺ lymphocyte at one month post-challenge, and (4) the source of IFN-γ and IL-10 were mainly CD4⁻ lymphocyte up to one month post-challenge suggesting that CD4⁻ lymphocytes may be responsible for protection induced by L. tropica infection in the studied intervals.     

Induction of cellular and humoral responses by autoclaved and heat-killed antigen of Leishmania donovani in experimental visceral leishmaniasis

The potential of autoclaved and heat-killed antigen of Leishmania donovani to induce cell-mediated and humoral response has been evaluated in the present study. The vaccines were delivered thrice subcutaneously at an interval of 2 weeks. Two weeks after second booster, BALB/c mice were challenged with 10⁷ stationary phase promastigotes of L. donovani. Significant protection was achieved in immunized mice against L. donovani challenge with 69% to 76% and 59% to 64% reduction in parasite load in the liver and spleen respectively. Immunization induced significantly higher level of delayed type hypersensitivity (DTH) response in mice immunized with heat-killed antigen followed by autoclaved antigen. The immune response was assessed by quantifying Leishmania-specific antibodies and cytokine production. The antibody response was predominantly of IgG type with increased IgG2a production and lesser amount of IgM. The immunization preferentially stimulates the production of IFN-γ and IL-2 in splenocytes which suggests a Th1 type response with a concomitant down-regulation of IL-10 and IL-4. These results indicate a potential for the heat-killed and autoclaved antigen as a vaccine which could trigger cell-mediated immune response.     

In vitro antileishmanial activity and cytotoxicity of essential oil from Lippia sidoides Cham

Leishmaniasis is a widespread tropical infection caused by different species of Leishmania protozoa. There is no vaccine available for Leishmania infections and conventional treatments are very toxic to the patients. Therefore, antileishmanial drugs are urgently needed. In this study we have analyzed the effects of essential oils from Lippia sidoides (LSEO) and its major compound thymol on the growth, viability and ultrastructure of Leishmania amazonensis. The essential oil and thymol showed significant activity against promastigote forms of L. amazonensis, with IC₅₀/48 h of 44.38 and 19.47 μg/mL respectively. However, thymol showed toxicity against peritoneal macrophages and low selectivity against the promastigotes when compared with the crude LSEO. On the other hand, no cytotoxic effect was observed in macrophages treated with the crude essential oil. Incubation of L. amazonensis-infected macrophages with LSEO showed a marked reduction in amastigote survival within the macrophages. Significant morphological alterations as accumulation of large lipid droplets in the cytoplasm, disrupted membrane and wrinkled cells were usually seen in treated parasites. The LSEO's activity against both promastigote and the amstigote forms of L. amazonensis, together with its low toxicity to mammalian cells, point to LSEO as a promising agent for the treatment of cutaneous leishmaniasis.     

Influence of long-term treatment with pravastatin on the survival, evolution of cutaneous lesion and weight of animals infected by Leishmania amazonensis

The high toxicity of current drugs for treatment of leishmaniasis is a major hindrance for controlling the disease. Pravastatin is a well-known drug with anti-inflammatory and immunomodulatory properties that may modulate host defense mechanisms against Leishmania. We evaluated the influence of prolonged pravastatin treatment on the survival of Leishmania amazonensis-infected animals (BALB/c, C57BL6 mice and Syrian hamsters), including weekly measurement of cutaneous lesions (footpad thickness) and weight. Pravastatin improved survival of Leishmania-infected BALB/c mice but not of infected C57BL6 mice or hamsters. On the 50th week of follow-up, 71% of pravastatin-treated Leishmania-infected BALB/c mice were alive against 29% of control group (p < 0.01). Low footpad thickness was found on BALB/c pravastatin treated mice from the 14th week (p < 0.05), and 20th week onward for C57BL6 treated mice. Pravastatin treatment decreased weight loss in Leishmania-infected C57BL6 mice and Syrian hamsters, but not infected BALB/c mice. Our results points to beneficial effects of pravastatin on the evolution of the disease in the murine leishmaniasis model.     

Expression of a Leishmaniadonovani nucleotide sugar transporter in Leishmaniamajor enhances survival in visceral organs

Leishmania donovani and Leishmaniainfantum infections cause fatal visceral leishmaniasis, and Leishmaniamajor causes self healing cutaneous lesions. It is poorly understood what genetic differences between these Leishmania species are responsible for the different pathologies of infection. To investigate whether L.donovani species-specific genes are involved in visceral Leishmania infection, we have examined a L.donovani species-specific gene Ld1590 (ortholog of LinJ15_V3.0900) that is a pseudogene in L.major. We have previously shown that transgenic expression of L.donovani Ld1590 in L.major significantly increased the liver and spleen parasite burdens in infected BALB/c mice. In this study we report that Ld1590 potentially encodes a nucleotide sugar transporter (NST) which localizes in the L.donovani Golgi apparatus. Surprisingly, although transgenic expression of the Ld1590 NST increased L.major survival in visceral organs, deletion of Ld1590 NST in L.donovani had no significant effect on L.donovani survival in mice. These observations suggest that loss of the functional Ld1590 gene in L.major may have been associated with reduced virulence in visceral organs in its animal reservoir and could have contributed to L.major’s tropism for cutaneous infections.     

An In Vitro Model of Antibody-Enhanced Killing of the Intracellular Parasite Leishmania amazonensis

Footpad infection of C3HeB/FeJ mice with Leishmania amazonensis leads to chronic lesions accompanied by large parasite loads. Co-infecting these animals with L. major leads to induction of an effective Th1 immune response that can resolve these lesions. This cross-protection can be recapitulated in vitro by using immune cells from L. major-infected animals to effectively activate L. amazonensis-infected macrophages to kill the parasite. We have shown previously that the B cell population and their IgG2a antibodies are required for effective cross-protection. Here we demonstrate that, in contrast to L. major, killing L. amazonensis parasites is dependent upon FcRγ common-chain and NADPH oxidase-generated superoxide from infected macrophages. Superoxide production coincided with killing of L. amazonensis at five days post-activation, suggesting that opsonization of the parasites was not a likely mechanism of the antibody response. Therefore we tested the hypothesis that non-specific immune complexes could provide a mechanism of FcRγ common-chain/NADPH oxidase dependent parasite killing. Macrophage activation in response to soluble IgG2a immune complexes, IFN-γ and parasite antigen was effective in significantly reducing the percentage of macrophages infected with L. amazonensis. These results define a host protection mechanism effective during Leishmania infection and demonstrate for the first time a novel means by which IgG antibodies can enhance killing of an intracellular pathogen.     

Isolation and detection of Leishmania species among naturally infected Rhombomis opimus, a reservoir host of zoonotic cutaneous leishmaniasis in Turkemen Sahara, North East of Iran

In Iran, three species of Leishmania have been incriminated as the causative agents of human leishmaniasis, Leishmania (L.) major, Leishmania tropica, and Leishmania infantum.Rhombomis opimus have been incriminated as a principal reservoirs of the parasitic protozoan Leishmania major, the causative agent of rural zoonotic cutaneous leishmaniasis (ZCL) in Iran. Rodents captured and examined to find Leishmania species using conventional methods including direct impression smear and microscopic observation inoculation samples to Balb/c and culture in NNN medium. Also molecular method was employed to detect Leishmania in rodents by amplifying a region of the ribosomal RNA amplicon of Leishmania (ITS1-5.8S rRNA–ITS2) using Nested PCR. Leshmania species were specified by DNA sequences. 36 (38.3%) of R. opimus were Leishmania positive using at least one conventional methods. Many more ITS-rDNA fragments were amplified from R. opimus but only 65 out of 74 PCR products contained enough DNA for direct sequencing or readable sequences. The PCR assays detected in Iranian R. opimus not only Leishmania major in 59 (79.7%) rodents but also Leishmania turanica in 6 (8.1%) rodents, another parasite of the great gerbil. These parasites were found in Turkemen Sahara, North East of Iran, in a focus of rural (ZCL). L. major and L. turanica in R. opimus firmly identified from Turkemen Sahara. Nine rodents with Leishmania infections unidentified which some were unreadable sequences, these could be mixed infections of L. major, L. turanica, Leishmania gerbillisensu lato and Leishmania close to L. gerbilli or a related species reported in sandflies previously from this location. The haplotypes of L. major and L. turanica were found to be identical to that of isolates of L. major and L. turanica from Iran and in GenBank elsewhere. R. opimus is probably the key reservoir in this ZCL focus because of its abundance and its infection rates with both L. major and L. turanica.     

T Cell-Derived IL-10 Determines Leishmaniasis Disease Outcome and Is Suppressed by a Dendritic Cell Based Vaccine

In the murine model of Leishmania major infection, resistance or susceptibility to the parasite has been associated with the development of a Th1 or Th2 type of immune response. Recently, however, the immunosuppressive effects of IL-10 have been ascribed a crucial role in the development of the different clinical correlates of Leishmania infection in humans. Since T cells and professional APC are important cellular sources of IL-10, we compared leishmaniasis disease progression in T cell-specific, macrophage/neutrophil-specific and complete IL-10-deficient C57BL/6 as well as T cell-specific and complete IL-10-deficient BALB/c mice. As early as two weeks after infection of these mice with L. major, T cell-specific and complete IL-10-deficient animals showed significantly increased lesion development accompanied by a markedly elevated secretion of IFN-γ or IFN-γ and IL-4 in the lymph nodes draining the lesions of the C57BL/6 or BALB/c mutants, respectively. In contrast, macrophage/neutrophil-specific IL-10-deficient C57BL/6 mice did not show any altered phenotype. During the further course of disease, the T cell-specific as well as the complete IL-10-deficient BALB/c mice were able to control the infection. Furthermore, a dendritic cell-based vaccination against leishmaniasis efficiently suppresses the early secretion of IL-10, thus contributing to the control of parasite spread. Taken together, IL-10 secretion by T cells has an influence on immune activation early after infection and is sufficient to render BALB/c mice susceptible to an uncontrolled Leishmania major infection.     

Redundancy of interleukin-6 in the differentiation of T cell and monocyte subsets during cutaneous leishmaniasis

Leishmania (L.) major is a protozoan parasite that infects mammalian hosts and causes a spectrum of disease manifestations that is strongly associated with the genetic background of the host. Interleukin (IL)-6 is an acute phase proinflammatory cytokine, known in vitro to be involved in the inhibition of the generation of regulatory T cells. IL-6-deficient mice were infected with L. major, and T cell and monocyte subsets were analyzed with flow cytometry. Our data show that at the site of infection in the footpad and in the draining popliteal lymph node, numbers of regulatory T cells remain unchanged between WT and IL-6-deficient mice. However, the spleens of IL-6^−/− mice contained fewer regulatory T cells after infection with L. major. The development of cutaneous lesions is similar between WT and IL-6-deficient mice, while parasite burden in IL-6^−/− mice is reduced compared to WT. The development of IFN-γ or IL-10 producing T cells is similar in IL-6^−/− mice. Despite a comparable adaptive T cell response, IL-6-deficient mice develop an earlier peak of some inflammatory cytokines than WT mice. This data indicate that the role of IL-6 in the differentiation of regulatory T cells is complex in vivo, and the effect of an absence of this cytokine can be counter-intuitive.     

IL-2 limits IL-12 enhanced lymphocyte proliferation during Leishmania amazonensis infection

C3H mice infected with Leishmania amazonensis develop persistent, localized lesions with high parasite loads. During infection, memory/effector CD44^hiCD4⁺ T cells proliferate and produce IL-2, but do not polarize to a known effector phenotype. Previous studies have demonstrated IL-12 is insufficient to skew these antigen-responsive T cells to a functional Th1 response. To determine the mechanism of this IL-12 unresponsiveness, we used an in vitro assay of repeated antigen activation. Memory/effector CD44^hiCD4⁺ T cells did not increase proliferation in response to either IL-2 or IL-12, although these cytokines upregulated CD25 expression. Neutralization of IL-2 enhanced CD4⁺ T cell proliferation in response to IL-12. This cross-regulation of IL-12 responsiveness by IL-2 was confirmed in vivo by treatment with anti-IL-2 antibodies and IL-12 during antigen challenge of previously infected mice. These results suggest that during chronic infection with L. amazonensis, IL-2 plays a dominant, immunosuppressive role independent of identifiable conventional T_reg cells.     

Intralesional uridine-5′-triphosphate (UTP) treatment induced resistance to <Emphasis Type="Italic">Leishmania amazonensis</Emphasis> infection by boosting Th<Subscript>1</Subscript> immune responses and reactive oxygen species production

Leishmania amazonensis is the etiologic agent of cutaneous leishmaniasis, an immune-driven disease causing a range of clinical symptoms. Infections caused by L. amazonensis suppress the activation and function of immune cells, including macrophages, dendritic cells, and CD4⁺ T cells. In this study, we analyzed the course of infection as well as the leishmanicidal effect of intralesional UTP treatment in L. amazonensis-infected BALB/c mice. We found that UTP treatment reduced the parasitic load in both footpad and lymph node sites of infection. UTP also boosted Th1 immune responses, increasing CD4⁺ T cell recruitment and production of IFN-γ, IL-1β, IL-12, and TNF-α. In addition, the role of UTP during innate immune response against L. amazonensis was evaluated using the air pouch model. We observed that UTP augmented neutrophil chemoattraction and activated microbicidal mechanisms, including ROS production. In conclusion, our data suggested an important role for this physiological nucleotide in controlling L. amazonensis infection, and its possible use as a therapeutic agent for shifting immune responses to Th1 and increasing host resistance against L. amazonensis infection.     

Rapid early onset lymphocyte cell death in mice resistant, but not susceptible to Leishmania major infection

Leishmania major (Lm) infection in mice is a prototypical model for the role of immune deviation in disease resistance. Resistant strains of mice develop a Th1 response to Lm infection, distinguished by secretion of IL-12 and interferon . In contrast, susceptible strains display sustained IL-4 expression characteristic of a Th2 response. However, when mechanisms of cell death are blocked, mice display a susceptible phenotype even in the presence of a strong Th1 response, suggesting that cell death, and not cytokine bias, may be an importnt factor in disease resistance. Here, we investigated this hypothesis by comparing lymphocyte cellularity, cell death and Fas expression in resistant CBA and susceptible BALB/c mice during the course of Lm infection. We found that delayed onset of cell death and late Fas induction correlated with massive lymphocyte accumulation and susceptibility to leishmaniasis, while early cell death and rapid Fas induction occurred in resistant mice.     

Leishmania major: activity of tamoxifen against experimental cutaneous leishmaniasis

Leishmaniasis is a family of diseases caused by protozoan parasites of the genus Leishmania. Various Leishmania species can cause human infection, producing a spectrum of clinical manifestations. The current treatments are unsatisfactory, and in absence of a vaccine, there is an urgent need for effective drugs to replace/supplement those currently in use. Recent studies have shown that the antineoplastic drug, tamoxifen, had direct leishmanicidal effect on several Leishmania species in vitro. Moreover, in vivo testing was carried out on some of the species and showed promising results. The authors have carried out the present work to complement previous published studies by investigating in vivo activity of tamoxifen in an experimental model of cutaneous leishmaniasis (CL) caused by Leishmania major. Groups of infected mice were given tamoxifen, orally, at a dose of 20 mg/kg/day for 15 days. Efficacy was assessed clinically, parasitologically, histopathologically by light and transmission electron microscope (TEM). Results showed that untreated infected mice suffered from autoamputation of the inoculated foot pad. However, those which received tamoxifen showed marked improvement of the cutaneous lesions and reduction of parasite burden. TEM of the cutaneous lesions from infected mice revealed the fine structure of normal Leishmania amastigotes, whereas those from infected mice treated with tamoxifen showed considerable changes. All male mice that received tamoxifen showed scrotal swelling with evident histopathological changes in the testes that could seriously compromise fertility of male mice. In conclusion, although tamoxifen causes significant side effects to the male reproductive system in the mouse model, it could provide an alternative to current agents. Results of this study demonstrated in vivo activity of tamoxifen against Leishmania major, thus, suggesting that tamoxifen is a suitable lead for the synthesis of more effective and less toxic antileishmanial derivatives.     

Sphingolipid Degradation in Leishmania (Leishmania) amazonensis

Background

Human leishmaniasis is caused by more than 20 Leishmania species and has a wide range of symptoms. Our recent studies have demonstrated the essential role of sphingolipid degradation in the virulence of Leishmania (Leishmania) major, a species responsible for localized cutaneous leishmaniasis in the Old World. In this study, we investigated the function of sphingolipid degradation in Leishmania (Leishmania) amazonensis, an etiological agent of localized and diffuse cutaneous leishmaniasis in South America.

Methodology/Principal Findings

First, we identified the enzyme LaISCL which is responsible for sphingolipid degradation in L. amazonensis. Primarily localized in the mitochondrion, LaISCL shows increased expression as promastigotes progress from replicative log phase to non-replicative stationary phase. To study its function, null mutants of LaISCL (Laiscl⁻) were generated by targeted gene deletion and complemented through episomal gene add-back. In culture, loss of LaISCL leads to hypersensitivity to acidic pH and poor survival in murine macrophages. In animals, Laiscl⁻ mutants exhibit severely attenuated virulence towards C57BL6 mice but are fully infective towards BALB/c mice. This is drastically different from wild type L. amazonensis which cause severe pathology in both BALB/c and C57BL 6 mice.

Conclusions/Significance

A single enzyme LaISCL is responsible for the turnover of sphingolipids in L. amazonensis. LaISCL exhibits similar expression profile and biochemical property as its ortholog in L. major. Deletion of LaISCL reduces the virulence of L. amazonensis and the outcome of Laiscl⁻-infection is highly dependent on the host''s genetic background. Therefore, compared to L. major, the role of sphingolipid degradation in virulence is substantially different in L. amazonensis. Future studies may reveal whether sphingolipid degradation is required for L. amazonensis to cause diffuse cutaneous infections in humans.     

The role of the P2X7 receptor in murine cutaneous leishmaniasis: aspects of inflammation and parasite control

Leishmania amazonensis is the etiological agent of diffuse cutaneous leishmaniasis. The immunopathology of leishmaniasis caused by L. amazonensis infection is dependent on the pathogenic role of effector CD4⁺ T cells. Purinergic signalling has been implicated in resistance to infection by different intracellular parasites. In this study, we evaluated the role of the P2X7 receptor in modulating the immune response and susceptibility to infection by L. amazonensis. We found that P2X7-deficient mice are more susceptible to L. amazonensis infection than wild-type (WT) mice. P2X7 deletion resulted in increased lesion size and parasite load. Our histological analysis showed an increase in cell infiltration in infected footpads of P2X7-deficient mice. Analysis of the cytokine profile in footpad homogenates showed increased levels of IFN-γ and decreased TGF-β production in P2X7-deficient mice, suggesting an exaggerated pro-inflammatory response. In addition, we observed that CD4⁺ and CD8⁺ T cells from infected P2X7-deficient mice exhibit a higher proliferative capacity than infected WT mice. These data suggest that P2X7 receptor plays a key role in parasite control by regulating T effector cells and inflammation during L. amazonensis infection.     

Leishmania amazonensis: participation of regulatory T and B cells in the in vitro priming (PIV) of CBA/J spleen cells susceptible response

CBA/J mice are resistant to Leishmania major and susceptible to Leishmania amazonensis. Early events determine infection outcome. Until now, PIV (in vitro priming) immune response to L. amazonensis has not been assessed. Herein, we have shown that compared to L. major, L. amazonensis induced higher parasite burden associated to similar IL-4, IFN-gamma, and TNF-alpha mRNA expressions and IFN-gamma and IL-10 levels. Although similar amounts of IL-10 were detected, the frequency of intracellular IL-10 positive B cells was enhanced in spleen cells stimulated with anti-CD3/anti-CD28, or anti-CD3/anti-CD28 and L. amazonensis, compared to L. major-stimulation. Interestingly, IL-10- producing B cells were reduced in response to anti-CD3/anti-CD28 stimulation combined with L. major compared to the other groups. L. amazonensis may favor T regulatory cell development, since 40% of all the CD4+CD25+ were CD25(high) cells. These data suggest that in PIV, susceptibility to L. amazonensis is not related to Th cell polarization, but to the presence and activity of regulatory T and B cells.     

The Route of Leishmania tropica Infection Determines Disease Outcome and Protection against Leishmania major in BALB/c Mice

Leishmania tropica is one of the causative agents of leishmaniasis in humans. Routes of infection have been reported to be an important variable for some species of Leishmania parasites. The role of this variable is not clear for L. tropica infection. The aim of this study was to explore the effects of route of L. tropica infection on the disease outcome and immunologic parameters in BALB/c mice. Two routes were used; subcutaneous in the footpad and intradermal in the ear. Mice were challenged by Leishmani major, after establishment of the L. tropica infection, to evaluate the level of protective immunity. Immune responses were assayed at week 1 and week 4 after challenge. The subcutaneous route in the footpad in comparison to the intradermal route in the ear induced significantly more protective immunity against L. major challenge, including higher delayed-type hypersensitivity responses, more rapid lesion resolution, lower parasite loads, and lower levels of IL-10. Our data showed that the route of infection in BALB/c model of L. tropica infection is an important variable and should be considered in developing an appropriate experimental model for L. tropica infections.     

The Leishmania promastigote surface antigen-2 (PSA-2) is specifically recognised by Th1 cells in humans with naturally acquired immunity to L. major

The promastigote surface antigen-2 (PSA-2) is a Leishmania parasite antigen, which can induce Th1-mediated protection against murine leishmaniasis when used as a vaccine. To evaluate PSA-2 as a human vaccine candidate the specific T-cell response to PSA-2 was characterised in individuals immune to cutaneous leishmaniasis. Peripheral blood mononuclear cells from Sudanese individuals with a past history of self-healing cutaneous leishmaniasis proliferated vigorously in response to PSA-2 isolated from Leishmania major, whereas the antigen did not activate cells from presumably unexposed Danes. Peripheral blood mononuclear cells from individuals with previous L. major infection had varying proliferative responses to PSA-2 derived from L. donovani promastigotes. Peripheral blood mononuclear cells activated by PSA-2 from L. major produced high amounts of interferon-γ and tumour necrosis factor-β, and little interleukin-4, thereby showing a Th1 cytokine pattern. Parallel cultures showed clear Th1 and Th2 response patterns to purified protein derivative of tuberculin or tetanus toxoid, respectively. Flow cytometric analysis revealed that PSA-2 induced blastogenesis in the CD3 positive population and that these cells were the major source of interferon-γ. The results show that Th1-like cells recognising PSA-2 are expanded during infection by L. major and that they maintain their Th1-like cytokine profile upon reactivation in vitro. Since immunity to cutaneous leishmaniasis is mediated by antigen-specific Th1-like cells, PSA-2 might be considered a vaccine candidate for human leishmaniasis.     

Saliva of laboratory-reared Lutzomyia longipalpis exacerbates Leishmania (Leishmania) amazonensis infection more potently than saliva of wild-caught Lutzomyia longipalpis

In order to compare the saliva effect from wild-caught and lab-reared L. longipalpis on the development of experimental cutaneous leishmaniasis, C57BL/6 mice were inoculated subcutaneously into the hind footpads with promastigotes of L. (L.) amazonensis plus salivary gland lysate from wild-caught (SGL-W) and lab-colonized (SGL-C) vectors. Lesion sizes were significantly larger in the mice infected with both saliva compared to mice infected with parasites alone; moreover, the lesions caused by parasite + SGL-C were significantly larger than the lesions caused by parasite + SGL-W. Histopathological morphometric studies regarding the acute phase of infections showed lower numbers of polymorphonuclear cells, greater numbers of mononuclear cells and parasites in SGL-C infected mice compared to SGL-W infected mice. In the chronic phase of infection, the number of mononuclear cells was lower and the number of parasites was greater in SGL-C infected mice than SGL-W infected mice. In vitro studies showed increased infection index of macrophages infected with parasites plus saliva compared to infection with parasites alone, with no difference between the saliva infection indices. SDS-PAGE gel for SGL-C and SGL-W showed differences in the composition and quantity of protein bands, determined by densitometry. These results call attention to the experimental saliva model, which shows exacerbation of infection caused by sandfly saliva.     

The Genome Sequence of Leishmania (Leishmania) amazonensis: Functional Annotation and Extended Analysis of Gene Models

We present the sequencing and annotation of the Leishmania (Leishmania) amazonensis genome, an etiological agent of human cutaneous leishmaniasis in the Amazon region of Brazil. L. (L.) amazonensis shares features with Leishmania (L.) mexicana but also exhibits unique characteristics regarding geographical distribution and clinical manifestations of cutaneous lesions (e.g. borderline disseminated cutaneous leishmaniasis). Predicted genes were scored for orthologous gene families and conserved domains in comparison with other human pathogenic Leishmania spp. Carboxypeptidase, aminotransferase, and 3′-nucleotidase genes and ATPase, thioredoxin, and chaperone-related domains were represented more abundantly in L. (L.) amazonensis and L. (L.) mexicana species. Phylogenetic analysis revealed that these two species share groups of amastin surface proteins unique to the genus that could be related to specific features of disease outcomes and host cell interactions. Additionally, we describe a hypothetical hybrid interactome of potentially secreted L. (L.) amazonensis proteins and host proteins under the assumption that parasite factors mimic their mammalian counterparts. The model predicts an interaction between an L. (L.) amazonensis heat-shock protein and mammalian Toll-like receptor 9, which is implicated in important immune responses such as cytokine and nitric oxide production. The analysis presented here represents valuable information for future studies of leishmaniasis pathogenicity and treatment.