Effects of common polymorphisms rs2910164 in miR-146a and rs3746444 in miR-499 on cancer susceptibility: a meta-analysis

MicroRNAs (miRNAs) are a class of new non-coding RNA, which may play a more important role in the pathogenesis of human cancers. Rs2910164 in miR-146a and rs3746444 in miR-499 are shown to be associated with increased/decreased cancer risk. We performed a meta-analysis to systematically summarize the possible association. We retrieved the relevant articles from PubMed databases. Studies were selected using specific inclusion and exclusion criteria. ORs and 95% CIs were calculated to access the strength of association between microRNA polymorphism and cancer risk. All analyses were performed using the Stata software. Twenty-nine studies were included in this meta-analysis. There were not significant associations between miR-146a rs2910164 and miR-499 rs3746444 polymorphisms with overall cancer risk. In the subgroup analysis by ethnicity, significantly affected cancer risks were found among Asians for both rs2910164 (GC vs. GG: OR = 0.89, 95% CI = 0.82–0.96; CC vs. GG: OR = 0.80, 95% CI = 0.66–0.97; GC + CC vs. GG: OR = 0.86, 95% CI = 0.76–0.97; C vs. G: OR = 0.91, 95% CI = 0.82–1.00) and rs3746444 (GG + AG vs. AA: OR = 1.21, 95% CI = 1.00–1.46). In the tumor type subgroup analysis, rs2910164 C allele decreased the risk of hepatocellular carcinoma (C vs. G: OR = 0.89, 95% CI = 0.80–1.00) and cervical squamous cell carcinoma (C vs. G: OR = 0.72, 95% CI = 0.62–0.84). The rs2910164 in miR-146a and the rs3746444 in miR-499 are likely to be associated with cancer risk.     

miR-499 rs3746444 polymorphism is associated with cancer development among Asians and related to breast cancer susceptibility

To derive a more precise estimation of the relationship between miR-499 rs3746444 polymorphism (A>G) and cancer risk, a meta-analysis was performed. A total of 9 studies including 6,077 cases and 7,199 controls were involved in this meta-analysis. Overall, no significantly elevated cancer risk was associated with miR-499 G allele when all studies were pooled into the meta-analysis (AG vs. AA: OR?=?1.14, 95?% CI?=?0.98–1.32; GG vs. AA: OR?=?1.12, 95?% CI?=?0.95–1.33; dominant model: OR?=?1.13, 95?% CI?=?0.99–1.29; recessive model: OR?=?1.05, 95?% CI?=?0.83–1.33). In the subgroup analysis by ethnicity, significantly increased risk was only found for Asians (dominant model: OR?=?1.22, 95?% CI?=?1.02–1.46). When stratified by study design, no statistically significantly elevated risks were found in hospital-based studies or population-based studies. In the subgroup analysis by cancer type, significant cancer risk change was only found for breast cancer when miR-499 G allele was included (dominant model: OR?=?1.13, 95?% CI?=?1.01–1.26). In conclusion, this meta-analysis suggests that the miR-499 rs3746444 polymorphism (A>G) is a low-penetrant risk factor for cancer development among Asians and may contribute to breast cancer susceptibility.     

Canine cutaneous leishmaniasis caused by neotropical Leishmania infantum despite of systemic disease: A case report

Visceral leishmaniasis is an anthropozoonosis caused by a protozoan Leishmania infantum (syn. Leishmania chagasi). Here, we report a typical case of canine cutaneous leishmaniasis due to L. infantum infection without any other systemic symptom in one dog in the city of Rio de Janeiro, Brazil. A mongrel female dog was admitted in a veterinary clinic with reports of chronic wounds in the body. Physical examination revealed erosive lesions in the limbs, nasal ulcers, presence of ectoparasites and seborrheic dermatitis. Blood samples and fragments of healthy and injured skin were collected. The complete hemogram revealed aregenerative normocytic normochromic anemia and erythrocyte rouleaux, and biochemical analysis revealed normal renal and hepatic functions. Cytology of the muzzle and skin lesions suggested pyogranulomatous inflammatory process. The histopathology of a skin fragment was performed and revealed suspicion of protozoa accompanied by necrotizing dermatitis. The diagnosis of leishmaniasis was accomplished by positive serology, isolation of Leishmania from the skin lesion, and also by molecular test (PCR targeting the conserved region of Leishmania kDNA). Culture was positive for damaged skin samples. PCR targeting a fragment of Leishmania hsp70 gene was performed employing DNA extracted from damaged skin. RFLP of the amplified hsp70 fragment identified the parasite as L. infantum, instead of Leishmania braziliensis, the main agent of cutaneous leishmaniasis in Rio de Janeiro. Characterization of isolated promastigotes by five different enzymatic systems confirmed the species identification of the etiological agent. Serology was positive by ELISA and rapid test. This case warns to the suspicion of viscerotropic Leishmania in cases of chronic skin lesions and brings the discussion of the mechanisms involved in the parasite tissue tropism.     

Exposure of phosphatidylserine on Leishmania amazonensis isolates is associated with diffuse cutaneous leishmaniasis and parasite infectivity

Diffuse cutaneous leishmaniasis (DCL) is a rare clinical manifestation of leishmaniasis, characterized by an inefficient parasite-specific cellular response and heavily parasitized macrophages. In Brazil, Leishmania (Leishmania) amazonensis is the main species involved in DCL cases. In the experimental model, recognition of phosphatidylserine (PS) molecules exposed on the surface of amastigotes forms of L. amazonensis inhibits the inflammatory response of infected macrophages as a strategy to evade the host immune surveillance. In this study, we examined whether PS exposure on L. amazonensis isolates from DCL patients operated as a parasite pathogenic factor and as a putative suppression mechanism of immune response during the infection. Peritoneal macrophages from F1 mice (BALB/c×C57BL/6) were infected with different L. amazonensis isolates from patients with localized cutaneous leishmaniasis (LCL) or DCL. DCL isolates showed higher PS exposure than their counterparts from LCL patients. In addition, PS exposure was positively correlated with clinical parameters of the human infection (number of lesions and time of disease) and with characteristics of the experimental infection (macrophage infection and anti-inflammatory cytokine induction). Furthermore, parasites isolated from DCL patients displayed an increased area in parasitophorous vacuoles (PV) when compared to those isolated from LCL patients. Thus, this study shows for the first time that a parasite factor (exposed PS) might be associated with parasite survival/persistence in macrophages and lesion exacerbation during the course of DCL, providing new insights regarding pathogenic mechanism in this rare chronic disease.     

Miltefosine in the treatment of cutaneous leishmaniasis caused by Leishmania braziliensis in Brazil: a randomized and controlled trial

Background

Cutaneous leishmaniasis (CL) is treated with parenteral drugs for decades with decreasing rate cures. Miltefosine is an oral medication with anti-leishmania activity and may increase the cure rates and improve compliance.

Methodology/Principal Findings

This study is a randomized, open-label, controlled clinical trial aimed to evaluate the efficacy and safety of miltefosine versus pentavalent antimony (Sb^v) in the treatment of patients with CL caused by Leishmania braziliensis in Bahia, Brazil. A total of 90 patients were enrolled in the trial; 60 were assigned to receive miltefosine and 30 to receive Sb^v. Six months after treatment, in the intention-to-treat analyses, the definitive cure rate was 53.3% in the Sb^v group and 75% in the miltefosine group (difference of 21.7%, 95% CI 0.08% to 42.7%, p = 0.04). Miltefosine was more effective than Sb^v in the age group of 13–65 years-old compared to 2–12 years-old group (78.9% versus 45% p = 0.02; 68.2% versus 70% p = 1.0, respectively). The incidence of adverse events was similar in the Sb^v and miltefosine groups (76.7% vs. 78.3%). Vomiting (41.7%), nausea (40%), and abdominal pain (23.3%) were significantly more frequent in the miltefosine group while arthralgias (20.7%), mialgias (20.7%) and fever (23.3%) were significantly more frequent in the Sb^v group.

Conclusions

This study demonstrates that miltefosine therapy is more effective than standard Sb^v and safe for the treatment of CL caused by Leishmania braziliensis in Bahia, Brazil.

Trial Registration

Clinicaltrials.gov Identifier {"type":"clinical-trial","attrs":{"text":"NCT00600548","term_id":"NCT00600548"}}NCT00600548     

Further observations on clinical, histopathological, and immunological features of borderline disseminated cutaneous leishmaniasis caused by Leishmania (Leishmania) amazonensis

Leishmania (Leishmania) amazonensis has for some time been considered as the causative agent of two distinct forms of American cutaneous leishmaniasis (ACL): localized cutaneous leishmaniasis (LCL), and anergic diffuse cutaneous leishmaniasis (ADCL). Recently, a new intermediate form of disease, borderline disseminated cutaneous leishmaniasis (BDCL), was introduced into the clinical spectrum of ACL caused by this parasite, and in this paper we record the clinical, histopathological, and immunological features of eight more BDCL patients from Brazilian Amazonia, who acquired the disease in the Pará state, North Brazil. Seven of them had infections of one to two years' evolution and presented with primary skin lesions and the occurrence of metastases at periods varying from six to 12 months following appearance of the first lesion. Primary skin lesions ranged from 1-3 in number, and all had the aspect of an erythematous, infiltrated plaque, variously located on the head, arms or legs. There was lymphatic dissemination of infection, with lymph node enlargement in seven of the cases, and the delayed hypersensitivity skin-test (DTH) was negative in all eight patients prior to their treatment. After that, there was a conversion of DTH to positive in five cases re-examined. The major histopathological feature was a dermal mononuclear infiltration, with a predominance of heavily parasitized and vacuolated macrophages, together with lymphocytes and plasma cells. In one case, with similar histopathology, the patient had acquired his infection seven years previously and he presented with the largest number of disseminated cutaneous lesions. BDCL shows clinical and histopathological features which are different from those of both LCL and ADCL, and there is a good prognosis of cure which is generally not so in the case of frank ADCL.     

PVT1 (rs13281615) and miR-146a (rs2910164) polymorphisms affect the prognosis of colon cancer by regulating COX2 expression and cell apoptosis

In this study, we aimed to investigate the potential correlation between rs13281615/rs2910164 polymorphisms and the prognosis of colon cancer (CC). Taqman was utilized to genotype the rs13281615/rs2910164 polymorphisms in recruited subjects. Kaplan–Meier survival curves were calculated to study the prognostic values of different genotypes of rs13281615/rs2910164 polymorphisms. Real-time polymerase chain reaction, enzyme-linked immunosorbent assay, immunohistochemistry, and terminal deoxynucleotidyl transferase dUTP nick-end labeling assays were conducted to establish a potential signaling pathway underlying the role of rs13281615/rs2910164 polymorphisms, whereas bioinformatics analysis and luciferase reporter assays were performed to identify plasmacytoma variant translocation 1 (PVT1) and cyclooxygenase-2 (COX2) as targets of microRNA-146a (miR-146a). No significant difference was observed in respect to clinical characteristics among subjects with different genotypes. However, patients genotyped as GG/CC + GC showed the lowest chance of survival, whereas patients of GA + AA/GG genotype showed the highest chance of survival. Moreover, the relative expressions of PVT1, prostaglandin E2 (PGE2), and COX2 were the lowest and the relative expression of miR-146a was the highest in GA + AA/GG subjects, validating the roles of PVT1, miR-146a, and COX2 in CC. In addition, both PVT1 and COX2 were identified as virtual targets of miR-146a, and the luciferase activities of cells cotransfected with wild-type PVT1/COX2 and miR-146a mimics were significantly reduced. Moreover, the presence of PVT1 decreased the level of miR-146a whereas increasing the messenger RNA and protein levels of COX2, thus establishing a PVT1/miR-146a/COX2 signaling pathway underlying the pathogenesis of CC. The presence of rs13281615 G > A polymorphism on PVT1 and the rs2910164 C > G polymorphism on miR-146a contributes to a favorable prognosis in CC patients via modulating the activity of the PVT1/miR-146a/COX2 signaling pathway.     

A promoter SNP rs4073T>A in the common allele of the interleukin 8 gene is associated with the development of idiopathic pulmonary fibrosis via the IL-8 protein enhancing mode

Background

Interleukin-8 (IL-8) is a potent chemo-attractant cytokine responsible for neutrophil infiltration in lungs with idiopathic pulmonary fibrosis (IPF). The IL-8 protein and mRNA expression are increased in the lung with IPF. We evaluated the effect of single nucleotide polymorphisms (SNPs) of the IL-8 gene on the risk of IPF.

Methods

One promoter (rs4073T>A) and two intronic SNPs (rs2227307T>G and rs2227306C>T) of the IL-8 genes were genotyped in 237 subjects with IPF and 456 normal controls. Logistic regression analysis was applied to evaluate the association of these SNPs with IPF. IL-8 in BAL fluids was measured using a quantitative sandwich enzyme immunoassay, and promoter activity was assessed using the luciferase reporter assay.

Results

The minor allele frequencies of rs4073T>A and rs2227307T>G were significantly lower in the 162 subjects with surgical biopsy-proven IPF and 75 subjects with clinical IPF compared with normal controls in the recessive model (OR = 0.46 and 0.48, p = 0.006 and 0.007, respectively). The IL-8 protein concentration in BAL fluids significantly increased in 24 subjects with IPF compared with 14 controls (p = 0.009). Nine IPF subjects homozygous for the rs4073 T>A common allele exhibited higher levels of the IL-8 protein compared with six subjects homozygous for the minor allele (p = 0.024). The luciferase activity of the rs4073T>A common allele was significantly higher than that of the rs4073T>A minor allele (p = 0.002).

Conclusion

The common allele of a promoter SNP, rs4073T>A, may increase susceptibility to the development of IPF via up-regulation of IL-8.     

Increased levels of cortisol are associated with the severity of experimental visceral leishmaniasis in a Leishmania (L.) infantum-hamster model

BackgroundSeveral infectious diseases are associated with hypothalamic-pituitary-adrenal (HPA) axis disorders by elevating circulating glucocorticoids (GCs), which are known to have an immunosuppressive potential. We conducted this study in golden hamsters, a suitable model for human visceral leishmaniasis (VL), to investigate the relationship of Leishmania (L.) infantum infection on cortisol production and VL severity.MethodsL. infantum-infected (n = 42) and uninfected hamsters (n = 30) were followed-up at 30, 120, and 180 days post-infection (dpi). Plasma cortisol was analyzed by radioimmunoassay and cytokines, inducible nitric oxide synthase (iNOS), and arginase by RT-qPCR.ResultsAll hamsters showed splenomegaly at 180 dpi. Increased parasite burden was associated with higher arginase expression and lower iNOS induction. Cortisol levels were elevated in infected animals in all-time points evaluated. Except for monocytes, all other leucocytes showed a strong negative correlation with cortisol, while transaminases were positively correlated. Immunological markers as interleukin (IL)-6, IL-1β, IL-10, and transforming growth-factor-β (TGF-β) were positively correlated to cortisol production, while interferon-γ (IFN-γ) presented a negative correlation. A network analysis showed cortisol as an important knot linking clinical status and immunological parameters.ConclusionsThese results suggest that L. infantum increases the systemic levels of cortisol, which showed to be associated with hematological, biochemical, and immunological parameters associated to VL severity.     

Antigenic extracts of Leishmania braziliensis and Leishmania amazonensis associated with saponin partially protects BALB/c mice against Leishmania chagasi infection by suppressing IL-10 and IL-4 production

This study evaluated two vaccine candidates for their effectiveness in protecting BALB/c mice against Leishmania chagasi infection. These immunogenic preparations were composed of Leishmania amazonensis or Leishmania braziliensis antigenic extracts in association with saponin adjuvant. Mice were given three subcutaneous doses of one of these vaccine candidates weekly for three weeks and four weeks later challenged with promastigotes of L. chagasi by intravenous injection. We observed that both vaccine candidates induced a significant reduction in the parasite load of the liver, while the L. amazonensis antigenic extract also stimulated a reduction in spleen parasite load. This protection was associated with a suppression of both interleukin (IL)-10 and IL-4 cytokines by spleen cells in response to L. chagasi antigen. No change was detected in the production of IFN-γ. Our data show that these immunogenic preparations reduce the type 2 immune response leading to the control of parasite replication.     

Variants of the microsomal triglyceride transfer protein gene are associated with plasma cholesterol levels and body mass index.

The microsomal triglyceride transfer protein (MTP) is required for the assembly and secretion of apolipoprotein B (apoB)-containing lipoproteins from liver and intestine. We set out to study the phenotypic modulation of all common genetic variants in the MTP gene. In addition, we aimed at characterizing the association between the various polymorphisms. A total of 564 healthy men were genotyped for the MTP -493 G/T, -400 A/T, and -164 T/C promoter polymorphisms, as well as the Q/H 95, I/T 128, Q/E 244, and H/Q 297 missense polymorphisms. The -493 G/T, -164 T/C, and I/T 128 polymorphisms showed to be in almost complete linkage disequilibrium. Subjects homozygous for the less common -493 T, -164 C, and T 128 alleles showed significantly lower plasma total and LDL cholesterol levels and plasma LDL apoB levels, and also significantly higher body mass index (BMI) and plasma insulin levels compared with carriers of the common alleles. The associations between plasma total cholesterol and MTP -493 genotype was verified in a cohort consisting of 1,117 disease-free control subjects of the West of Scotland Coronary Prevention Study (WOSCOPS). None of the other polymorphisms showed any significant change in either lipid and lipoprotein levels or anthropometric variables.In summary, two promoter polymorphisms and one missense polymorphism in the MTP gene alter plasma total and LDL cholesterol levels, plasma LDL apoB levels, BMI, and insulin levels. This may, in turn, have implications for genetic regulation of cardiovascular risk factors.     

Atypical mucocutaneous leishmaniasis caused by Leishmania braziliensis in an acquired immunodeficiency syndrome patient: T-cell responses and remission of lesions associated with antigen immunotherapy.

An atypical case of acquired immunodeficiency syndrome-associated mucocutaneous lesions due to Leishmania braziliensis is described. Many vacuolated macrophages laden with amastigote forms of the parasite were found in the lesions. Leishmanin skin test and serology for leishmaniasis were both negative. The patient was resistant to therapy with conventional drugs (antimonial and amphotericin B). Interestingly, remission of lesions was achieved after an alternative combined therapy of antimonial associated with immunotherapy (whole promastigote antigens). Peripheral blood mononuclear cells were separated and stimulated in vitro with Leishmania antigens to test the lymphoproliferative responses (LPR). Before the combined immunochemotherapy, the LPR to leishmanial antigens was negligible (stimulation index - SI=1.4). After the first course of combined therapy it became positive (SI=4.17). The antigen responding cells were predominantly T-cells (47.5%) most of them with CD8+ phenotype (33%). Very low CD4+ cells (2.2%) percentages were detected. The increased T-cell responsiveness to leishmanial antigens after combined therapy was accompanied by interferon-g (IFN-g) production as observed in the cell culture supernatants. In this patient, healing of the leishmaniasis lesions was associated with the induction of a specific T-cell immune response, characterized by the production of IFN-g and the predominance of the CD8+ phenotype among the Leishmania-reactive T-cells.     

Differential recognition of Leishmania aethiopica antigens by lymphocytes from patients with local and diffuse cutaneous leishmaniasis. Evidence for antigen-induced immune suppression

Data are presented to suggest that differential Ag expression by parasites derived from diffuse (DCL) vs local (LCL) cutaneous leishmaniasis patients may be responsible for the Ag-specific anergy seen in DCL patients. The evidence suggests that promastigotes derived from DCL patients express epitopes which preferentially stimulate suppressor activities in DCL patients. These determinants appear to be expressed less, if at all by promastigotes derived from LCL patients. The Ag-specific suppression or nonresponsiveness which dominates the immune response in DCL patients during an active infection can be abrogated by drug treatment or removal of live DCL parasites, which suggests that Ag-induced regulatory cells, probably of T cell lineage, are most likely responsible for the nonresponsiveness seen in untreated DCL patients. Thus the mechanisms of immune regulation operating in this disease differ from that of lepromatous leprosy where the specific unresponsiveness (anergy) is irreversible even after successful treatment.     

Protective immune response against cutaneous leishmaniasis by prime/booster immunization regimens with vaccinia virus recombinants expressing Leishmania infantum p36/LACK and IL-12 in combination with purified p36

In susceptible mice Leishmania infection triggers a CD4(+) Th2 response that has been correlated with evasion of the host immune system. To develop approaches that might trigger a Th1 response leading to protection against Leishmania we generated vaccinia virus recombinants (VVr) expressing the relevant p36/LACK protein of Leishmania infantum (VVp36) or co-expressing p36/LACK and interleukin-12 (VVp36IL12). Susceptible BALB/c mice were immunized with the VVr in various prime/booster protocols that included purified p36/LACK protein, followed 3 weeks later by a challenge with live L. major promastigotes. The course of the infection was monitored by measuring lesion development, parasite load and immunological parameters (IFN-gamma and IL-10 secretion by in vitro-stimulated lymphocytes, and specific IgG isotypes), before and after challenge. We found protocols of prime/booster immunization (VVp36/VVp36; VVp36IL12/p36; p36/VVp36IL12) that elicited different levels of protection in infected animals. The protocol of priming with purified p36 followed by a booster with VVp36IL12 induced 52% reduction in lesion size and a two-log unit reduction in parasite load. This partial protection correlated with activation of a specific Th1 type of immune response. These protocols could be of interest in the prophylaxis against Leishmania spp. and other parasitic diseases.     

The development of clinical signs of rheumatoid synovial inflammation is associated with increased synthesis of the chemokine CXCL8 (interleukin-8)

Paired synovial tissue samples were obtained from both clinically uninvolved (CU) and clinically involved (CI) knee joints of eight rheumatoid arthritis (RA) patients. In addition, biopsies were taken from five control subjects. We observed the expression of the chemokines CXCL8, CXCL9, CXCL10, CCL2 and CCL4 in CI and CU joints of RA patients. In particular, CXCL8 protein levels were specifically increased in CI joints compared with CU joints, which was confirmed by immunohistochemistry and in situ hybridization.     

The development of clinical signs of rheumatoid synovial inflammation is associated with increased synthesis of the chemokine CXCL8 (interleukin-8)

Paired synovial tissue samples were obtained from both clinically uninvolved (CU) and clinically involved (CI) knee joints of eight rheumatoid arthritis (RA) patients. In addition, biopsies were taken from five control subjects. We observed the expression of the chemokines CXCL8, CXCL9, CXCL10, CCL2 and CCL4 in CI and CU joints of RA patients. In particular, CXCL8 protein levels were specifically increased in CI joints compared with CU joints, which was confirmed by immunohistochemistry and in situ hybridization.     

Regulatory T cells in the pathogenesis and healing of chronic human dermal leishmaniasis caused by Leishmania (Viannia) species

Background

The inflammatory response is prominent in the pathogenesis of dermal leishmaniasis. We hypothesized that regulatory T cells (Tregs) may be diminished in chronic dermal leishmaniasis (CDL) and contribute to healing during treatment.

Methodology/Principal Findings

The frequency and functional capacity of Tregs were evaluated at diagnosis and following treatment of CDL patients having lesions of ≥6 months duration and asymptomatically infected residents of endemic foci. The frequency of CD4⁺CD25^hi cells expressing Foxp3 or GITR or lacking expression of CD127 in peripheral blood was determined by flow cytometry. The capacity of CD4⁺CD25⁺ cells to inhibit Leishmania-specific responses was determined by co-culture with effector CD4⁺CD25⁻ cells. The expression of FOXP3, IFNG, IL10 and IDO was determined in lesion and leishmanin skin test site biopsies by qRT-PCR. Although CDL patients presented higher frequency of CD4⁺CD25^hiFoxp3⁺ cells in peripheral blood and higher expression of FOXP3 at leishmanin skin test sites, their CD4⁺CD25⁺ cells were significantly less capable of suppressing antigen specific-IFN-γ secretion by effector cells compared with asymptomatically infected individuals. At the end of treatment, both the frequency of CD4⁺CD25^hiCD127⁻ cells and their capacity to inhibit proliferation and IFN-γ secretion increased and coincided with healing of cutaneous lesions. IDO was downregulated during healing of lesions and its expression was positively correlated with IFNG but not FOXP3.

Conclusions/Significance

The disparity between CD25^hiFoxp3⁺ CD4 T cell frequency in peripheral blood, Foxp3 expression at the site of cutaneous responses to leishmanin, and suppressive capacity provides evidence of impaired Treg function in the pathogenesis of CDL. Moreover, the concurrence of increased Leishmania-specific suppressive capacity with induction of a CD25^hiCD127⁻ subset of CD4 T cells during healing supports the participation of Tregs in the resolution of chronic dermal lesions. Treg subsets may therefore be relevant in designing immunotherapeutic strategies for recalcitrant dermal leishmaniasis caused by Leishmania (Viannia) species.     

Leishmania antigens are presented to CD8+ T cells by a transporter associated with antigen processing-independent pathway in vitro and in vivo

CD8+ T cells are generated in response to Leishmania major (Lm) or Toxoplasma gondii parasitic infections, indicating that exogenously delivered Ag can be processed for presentation by MHC class I molecules. We show that presentation of Lm nucleotidase (NT)-OVA is TAP independent in vivo and in vitro, and is inhibited by chloroquine, but not by proteasome inhibitors. In contrast, the presentation of T. gondii P30-OVA relies on the TAP/proteasome pathway. Presentation of OVA- or rNT-OVA-coated beads also bypassed TAP requirement above a certain Ag threshold. TAP was also dispensable for the presentation of wild-type Lm Ags to primed CD8+ T cells in vitro. Finally, in vivo priming of CD8+ T cells involved in acquired resistance to Lm was not compromised in TAP-deficient mice. Thus, Leishmania Ags appear to be confined to an intraphagosomal processing pathway that requires higher concentrations of Ags, suggesting that these parasites may have evolved strategies to impair the efficient endoplasmic reticulum-based, TAP-dependent cross-presentation pathway to avoid or delay CD8+ T cell priming.