Adriano Gomes-Silva

Can interferon‐γ and interleukin‐10 balance be associated with severity of human Leishmania (Viannia) braziliensis infection?

Suitable levels of interferon (IFN)‐γ and interleukin (IL)‐10 seem to favour the outcome of cutaneous leishmaniasis (CL), while high IFN‐γ and low IL‐10 production are associated with severity of mucosal leishmaniasis (ML). Considering that cytokine balance is important for the maintenance of protective responses in leishmaniasis, our aim was to investigate leishmanial antigens‐induced IFN‐γ and IL‐10 levels maintained in healed individuals who had different clinical outcomes of Leishmania infection. Thirty‐three individuals who recovered from L. braziliensis infection were studied: cured CL (CCL), cured ML (CML), spontaneous healing of CL (SH) or asymptomatic individuals (ASY). Cytokines were quantified by enzyme‐linked immunosorbent assay (ELISA) in culture supernatants of L. braziliensis‐stimulated peripheral blood mononuclear cells (PBMC). IFN‐γ levels were higher in CML (7593 ±  5994 pg/ml) in comparison to SH (3163 ± 1526 pg/ml), ASY (1313 ±  1048 pg/ml) or CCL (1897 ± 2087 pg/ml). Moreover, cured ML cases maintained significantly lower production of IL‐10 (127 ± 57·8 pg/ml) in comparison to SH (1373 ± 244 pg/ml), ASY (734 ± 233 pg/ml) or CCL (542 ±  375 pg/ml). Thus, a high IFN‐γ/IL‐10 ratio observed in CML can indicate unfavourable cytokine balance. On the other hand, no significant difference in the IFN‐γ/IL‐10 ratio was observed when CCL individuals were compared to SH or ASY subjects. In conclusion, even after clinical healing, ML patients maintained a high IFN‐γ/IL‐10 secretion profile in response to leishmanial antigens. This finding can explain a delayed down‐modulation of exacerbated inflammatory responses, which can be related in turn to the necessity of prolonged therapy in ML management. Conversely, lower IFN‐γ/IL‐10 balance observed in CCL, SH and ASY individuals can represent a better‐modulated immune response associated with a favourable prognosis.

IFNG +874T/A polymorphism is not associated with American tegumentary leishmaniasis susceptibility but can influence Leishmania induced IFN-γ production

BackgroundInterferon-gamma is a key cytokine in the protective responses against intracellular pathogens. A single nucleotide polymorphism (SNP) located in the first intron of the human IFN-γ gene can putatively influence the secretion of cytokine with an impact on infection outcome as demonstrated for tuberculosis and other complex diseases. Our aim was to investigate the putative association of IFNG+874T/A SNP with American tegumentary leishmaniasis (ATL) and also the influence of this SNP in the secretion of IFN-γ in vitro.MethodsBrazilian ATL patients (78 cutaneous, CL, and 58 mucosal leishmaniasis, ML) and 609 healthy volunteers were evaluated. The genotype of +874 region in the IFN-γ gene was carried out by Amplification Refractory Mutational System (ARMS-PCR). Leishmania-induced IFN-γ production on peripheral blood mononuclear cell (PBMC) culture supernatants was assessed by ELISA.ResultsThere are no differences between +874T/A SNP frequency in cases and controls or in ML versus CL patients. Cutaneous leishmaniasis cases exhibiting AA genotype produced lower levels of IFN-γ than TA/TT genotypes. In mucosal cases, high and low IFN-γ producers were clearly demonstrated but no differences in the cytokine production was observed among the IFNG +874T or A carriers.ConclusionOur results suggest that +874T/A polymorphism was not associated with either susceptibility or severity to leishmaniasis. Despite this, IFNG +874T/A SNP could be involved in the pathogenesis of leishmaniasis by influencing the amount of cytokine released by CL patients, although it could not prevent disease development. On the other hand, it is possible that in ML cases, other potential polymorphic regulatory genes such as TNF-α and IL-10 are also involved thus interfering with IFN-γ secretion.

Local immunological factors associated with recurrence of mucosal leishmaniasis

Recurrence of mucosal leishmaniasis (ML) is frequent, but the causative mechanisms are unknown. Our aim was to compare cellular and cytokine patterns of lesions from ML that evolved to recurrence or cure in order to determine the risk factor associated with recurrence. Lesions were evaluated by immunohistochemistry before and after therapy, and patients were followed-up for five years. Higher levels of CD4(+) T and IFN-gamma-producing cells were detected in active lesions and decreased after therapy. Macrophages and IL-10 were markedly increased in cured patients. Conversely, CD8(+) T and NK cells were higher in relapsed than in cured cases. Notably, a decrease in these cells in addition to decreased IL-10 and IFN-gamma was also observed after therapy. These data suggest that exacerbated CD8(+) activity, in addition to a poor regulatory response, could underlie an unfavorable fate with regard to ML. These markers may be useful for predicting the prognosis of ML in lesion studies.

Candidate gene case-control and functional study shows macrophage inhibitory factor (MIF) polymorphism is associated with cutaneous leishmaniasis.

American tegumentary leishmaniasis (ATL) is an infectious disease caused mostly by Leishmania(Viannia)braziliensis in Southeast Brazil. The clinical manifestations are vast, ranging from asymptomatic to severe mucosal leishmaniasis (ML). It has been suggested that variation of the pathogen does not fully explain the response spectrum and the variability of clinical manifestations. Previous data have shown that host genetics also play a role in disease outcome. Herein, we have tested the association of TNF, IL10, IL12 and MIF single nucleotide polymorphisms (SNPs) using a case-control study design including 110 cutaneous leishmaniasis (CL) patients and 682 healthy subjects. The genotype-phenotype correlation was also assessed using leishmania antigens to stimulate peripheral blood mononuclear cells obtained from cured CL patients. Results demonstrated that the MIF -173C allele is associated with leishmaniasis outcome and also with lower levels of MIF in culture supernatants. Also, the TNF -308AA genotype was statistically increased among leishmaniasis patients. The results showed here suggest that the lower levels of MIF produced by MIF -173C carriers could influence the host-Leishmania interaction, favoring infection and disease progression. On the other hand, high TNF levels can contribute to tissue damage, consequently leading to skin lesions.

Comparative Evaluation of Lesion Development, Tissue Damage, and Cytokine Expression in Golden Hamsters (Mesocricetus auratus) Infected by Inocula with Different Leishmania (Viannia) braziliensis Concentrations

ABSTRACT The golden hamster (Mesocricetus auratus) is a susceptible model to Leishmania (Viannia) spp.; however, available studies employ different infection protocols, which account for clinical and pathological presentation differences. Herein, L. (V.) braziliensis preparations were standardized to contain 104, 105, or 106 parasites to determine an optimal inoculum that ensured cutaneous lesions without causing a disseminated infection in hamsters. Lesion development was followed for 105 days by size measurements, and skin, draining lymph node, spleen, and sera were investigated to check parasite load, spleen visceralization, cytokine expression, histopathological changes, and anti-Leishmania IgG levels. The lesion emergence time was inversely proportional to the parasite concentration in the inocula. Animals infected by 104 parasites presented nodular lesions, while those infected with 106 parasites often exhibited ulcerated lesions. The differences in the final lesion sizes were observed between 104 and 105 inocula or 104 and 106 inocula. High IFNG expression, anti-Leishmania IgG levels, and parasite load occurred independently of the inoculum used. A mild inflammatory skin involvement was observed in animals infected with 104 parasites, while extensive tissue damage and parasite spleen visceralization occurred with 105 and 106 parasites. These results indicate that inocula with different concentrations of parasites generate differences in the time of lesion emergence, clinical presentation, and systemic commitment, despite high and similar IFNG expression and parasite load. This suggests that a modulation in the immune response to different parasite numbers occurs in an early phase of the infection, which could dictate the establishment and magnitude of the chronic phase of the disease.

Apoptosis and frequency of total and effector CD8 + T lymphocytes from cutaneous leishmaniasis patients during antimonial therapy

BackgroundLeishmaniasis is an important parasitic disease affecting millions worldwide. Human cutaneous leishmaniasis (CL) is endemic in Rio de Janeiro, Brazil, where is caused by Leishmania braziliensis. The adaptive immune response is accountable for the healing of CL and despite of key role of CD8+ T cells in this immune response little is known about the CD8+ T lymphocytes frequencies, apoptosis and antigen-responsive CD8+ T lymphocytes of CL patients during antimonial therapy.MethodsUsing flow cytometry, we examined total and effector CD8+ T cells from CL patients before (PBT), during (PDT) and after (PAT) treatment for apoptosis and frequencies upon isolation and after in vitro L. braziliensis antigens (LbAg)-stimulation culture. Besides, a correlation study between immunological findings and lesion size was done.ResultsPDT showed lower frequencies of total CD8+ T lymphocytes and higher levels of apoptosis of these cells, which were also observed following LbAg-stimulation culture. Regarding effector CD8+ T cells, high frequencies were observed in PDT, while lower frequencies were observed in PAT. Interestingly, PDT showed higher frequencies of apoptotic-effector CD8+ T lymphocytes. Similar results were seen after in vitro antigenic-stimulation assays. Correlation analysis showed that the greater the size of lesion, the smaller the frequency of effector CD8+ T lymphocytes in PDT and PAT, as well as a positive correlation between apoptotic-effector CD8+ T cells frequency and lesion size of PDT.ConclusionsChanges in effector CD8+ T–lymphocyte frequencies, during and after treatment, seem to represent a critical stage to generate an efficient immune response and suggest that these cells would be evolved in the triggering or in the resolution of lesion, under the influence of therapy. This hypothesis opens new perspectives to clarify controversial statements about the protective or deleterious role of CD8+ T cells in the cure or aggravation of CL and the new approach of evaluating patients during treatment proved to be of utmost importance for understanding the immune response in the healing process of human CL.

Leishmania braziliensis-Reactive T Cells Are Down-Regulated in Long-Term Cured Cutaneous Leishmaniasis, but the Renewal Capacity of T Effector Memory Compartments Is Preserved

Leishmania (Viannia) braziliensis control and tissue damage relate to the effector immune response, which in turn affects clinical outcome. Leishmania reactive CD4+ and CD8+ T cells are expanded in long-term healed cutaneous leishmaniasis (hCL) patients but their functional characteristics remain to be determined. This study investigates antigen-specific recall in long-term healed CL caused by L. braziliensis infection. Healed CL subjects were grouped according to the time elapsed since the end of therapy: less than two years and two to five years. Activation phenotype (CD69+ or CD25+) and subpopulations of memory T cell phenotypes [central memory (Tcm): CD45RO+ CCR7+ or effector memory (Tem): CD45RO+ CCR7-] were quantified in ex vivo blood mononuclear cells and after Leishmania antigens stimuli. A reduction in the percentage of activated Leishmania-responder CD4+ and CD8+ T cells in hCL was associated with the time elapsed since clinical cure. Percentage of CD69+ in TCD4+ and TCD8+ cells were negatively correlated with IL-10 levels. Ex vivo analyses showed contracted Tem CD4+ and Tem CD8+ compartments from hCL with long time elapsed since clinical cure, although renewal of these compartments was observed following in vitro exposure to leishmanial stimuli. Our results show that healed L. braziliensis infected patients exhibit a recall response to Leishmania antigens with evident expansion of effector memory T cells. Regulated leishmanial-specific response seems to emerge only about two years after initial contact with the parasite antigens.

The skin homing receptor cutaneous leucocyte‐associated antigen (CLA) is up‐regulated by Leishmania antigens in T lymphocytes during active cutaneous leishmaniasis

The cutaneous leucocyte‐associated antigen receptor (CLA) can direct Leishmania‐specific T lymphocytes towards inflamed skin lesions. Homing receptors [CLA, lymphocyte‐associated antigen 1 (LFA‐1) or CD62L] were analysed in lymphocytes from blood and cutaneous leishmaniasis (CL) lesions. CL patients with active lesions (A‐CL) presented lower levels of T lymphocytes expressing the CLA+ phenotype (T CD4+ = 10·4% ± 7·5% and T CD8+ = 5·8% ± 3·4%) than did healthy subjects (HS) (T CD4+ = 19·3% ±  13·1% and T CD8+ = 21·6% ± 8·8%), notably in T CD8+ (P < 0·001). In clinically cured patients these percentages returned to levels observed in HS. Leishmanial antigens up‐regulated CLA in T cells (CLA+ in T CD4+ =  33·3% ± 14·1%; CLA+ in T CD8+ = 22·4% ± 9·4%) from A‐CL but not from HS. An enrichment of CLA+ cells was observed in lesions (CLA+ in T CD4+ = 45·9% ± 22·5%; CLA+ in T CD8+ = 46·4% ± 16·1%) in comparison with blood (CLA+ in T CD4+ = 10·4% ± 7·5%; CLA+ in T CD8+ = 5·8% ±  3·4%). Conversely, LFA‐1 was highly expressed in CD8+ T cells and augmented in CD4+ T from peripheral blood of A‐CL patients. In contrast, CD62L was not affected. These results suggest that Leishmania antigens can modulate molecules responsible for migration to skin lesions, potentially influencing the cell composition of inflammatory infiltrate of leishmaniasis or even the severity of the disease.

Antigen-triggered interferon-γ and interleukin-10 pattern in cured mucosal leishmaniasis patients is shaped during the active phase of disease

An exacerbated type 1 response to leishmanial antigens is the basis of tissue destruction observed in mucosal leishmaniasis (ML). After therapy, a persistent production of high levels of inflammatory cytokines can confer a poor prognosis. Herein we investigated whether the clinical conditions defined during the active phase of ML affect the magnitude of long‐term anti‐Leishmania immune response. Twenty clinically cured ML cases were studied. Peripheral blood mononuclear cells (PBMC) were cultured with L. braziliensis antigens (Lb‐Ag), Toxoplasma gondii antigens (Tg‐Ag), concanavalin‐A (Con‐A) or medium alone, and the lymphocyte proliferative response and cytokine secretion were quantified. Medical records were reviewed for Montenegro skin test (MST) during diagnosis, duration of ML disease or time elapsed after clinical cure. The duration of disease was correlated positively with MST (r = 0·61). Lb‐Ag induced interferon (IFN)‐γ was correlated positively with duration of illness (r = 0·69) as well as the frequency of secreting cells [enzyme‐linked immunospot (ELISPOT)] assay. No association was observed for Tg‐Ag or Con‐A. Disease duration was correlated negatively with interleukin (IL)‐10 production (r = −0·76). Moreover, a negative correlation between length of time after clinical cure and TNF levels (r = −0·94) or the IFN‐γ : IL‐10 ratio (r = −0·89) were also seen. We suggest that the magnitude of the IFN‐γ inflammatory response triggered by ML can be driven by the time of leishmanial antigens exposition during the active phase of the disease. This pattern could persist even long‐term after cure. However, despite IFN‐γ levels, the decrease of the TNF and IFN‐γ : IL‐10 ratio reflects the control of proinflammatory responses achieved by cure of ML, possibly preventing disease relapses.

Intranasal Vaccination with Leishmanial Antigens Protects Golden Hamsters (Mesocricetus auratus) Against Leishmania (Viannia) braziliensis Infection

Background Previous results have shown that oral and intranasal administration of particulate Leishmania (Leishmania) amazonensis antigens (LaAg) partially protects mice against L. amazonensis infection. However, vaccination studies on species of the subgenus Viannia, the main causative agent of cutaneous and mucosal leishmaniasis in the Americas, have been hampered by the lack of easy-to-handle bio-models that accurately mimic the human disease. Recently, we demonstrated that the golden hamster is an appropriate model for studying the immunopathogenesis of cutaneous leishmaniasis caused by L. (Viannia) braziliensis. Using the golden hamster model, our current study investigated whether the protective effect of intranasal immunisation with LaAg can be extended to L. braziliensis infection. Methodology/Principal Findings Golden hamsters vaccinated with either two intranasal (IN) doses of LaAg (10 µg) or two intramuscular doses of LaAg (20 µg) were challenged 2 weeks post-vaccination with L. braziliensis. The results showed that IN immunisation with LaAg significantly reduced lesion growth and parasitic load as well as serum IgG and IgG2 levels. At the experimental endpoint on day 114 post-infection, IN-immunised hamsters that were considered protected expressed IFN-γ and IL10 mRNA levels that returned to uninfected skin levels. In contrast to the nasal route, intramuscular (IM) immunisation failed to provide protection. Conclusions/Significance These results demonstrate for the first time that the nasal route of immunisation can induce cross protection against L. braziliensis infection.