Immunoregulatory mechanisms and CD4-CD8- (double negative) T cell subpopulations in human cutaneous leishmaniasis: a balancing act between protection and pathology

Chlorella vulgaris extract and Imiquimod as new therapeutic targets for leishmaniasis: An immunological approach

The therapeutic regimen for the treatment of American Tegumentary Leishmaniasis (ATL) is targeted at the death of the parasite; therefore, it is essential to develop a treatment that can act on the parasite, combined with the modulation of the inflammatory profile. Thus, the aim of this study was to make an in vitro evaluation of the therapeutic potential of Chlorella vulgaris extract (CV) and Imiquimod for ATL. Selectivity indices (SI) were determined by inhibitory concentration assays (IC50) in L. braziliensis cells and cytotoxic concentrations (CC50) were measured in human cells using the MTT method, based on the CV microalgae extract (IC50 concentrations of 15.63 to 500 µg/mL; CC50 concentrations of 62.5-1000 µg/mL) in comparison with the reference drugs and Imiquimod. The immune response was evaluated in healthy human cells by gene expression (RT-qPCR) and cytokine production (Flow Cytometry). The CV extract (SI = 6.89) indicated promising results by showing higher SI than meglumine antimoniate (SI = 3.44) (reference drug). In all analyses, CV presented a protective profile by stimulating the production of Th1 profile cytokines to a larger extent than the reference drugs. Imiquimod showed a high expression for Tbx21, GATA3, RORc and Foxp3 genes, with increased production only of the TNF cytokine. Therefore, the data highlight the natural extract and Imiquimod as strong therapeutic or adjuvant candidates against ATL, owing to modulation of immune response profiles, low toxicity in human cells and toxic action on the parasite.

Comparative analysis of the severity and progression of cutaneous leishmaniasis caused by Leishmania tropica in untreated and glucantime-treated patients

Millions of people worldwide are affected by cutaneous leishmaniasis (CL), a disease that has a significant impact on morbidity and mortality. Understanding the immune responses responsible for tissue damage or the process of lesion healing plays a pivotal role in shaping optimal treatment strategies. In this study, we investigated immunological phenotypes for three groups: glucantime treated (n = 30) and untreated (n = 30) CL patients infected with Leishmania tropica (L. tropica), and healthy controls (n = 20). T-lymphocytes (CD4+ and CD8+), and B lymphocytes (CD14+ and CD19+) were isolated using antibody-conjugated microbeads and magnetic field isolation to achieve high purity. A higher significant difference was observed between T-lymphocytes (CD4+ and CD8+), and B-lymphocytes (CD14+ and CD19+) cells in CL-infected groups before and after treatment (p < 0.0001). When compared, there was also a significant difference among T-lymphocytes (CD4+ and CD8+), B lymphocytes (CD14+ and CD19+) p < 0.0001, p < 0.0005, and p < 0.0007, respectively between CL-infected individuals (before and after treatment) to controls. Our findings suggest that an increased proportion of these cells seen in treated patients may mediate healing, while it is also possible that they may contribute to tissue injury. Understanding the immune system and lesion size of CL can help develop immunotherapies and comprehend the evolution of this parasitic disease.

Clinical and immunological spectra of human cutaneous leishmaniasis in North Africa and French Guiana

Cutaneous leishmaniasis (CL) caused by infection with the parasite Leishmania exhibits a large spectrum of clinical manifestations ranging from single healing to severe chronic lesions with the manifestation of resistance or not to treatment. Depending on the specie and multiple environmental parameters, the evolution of lesions is determined by a complex interaction between parasite factors and the early immune responses triggered, including innate and adaptive mechanisms. Moreover, lesion resolution requires parasite control as well as modulation of the pathologic local inflammation responses and the initiation of wound healing responses. Here, we have summarized recent advances in understanding the in situ immune response to cutaneous leishmaniasis: i) in North Africa caused by Leishmania (L.) major, L. tropica, and L. infantum, which caused in most cases localized autoresolutives forms, and ii) in French Guiana resulting from L. guyanensis and L. braziliensis, two of the most prevalent strains that may induce potentially mucosal forms of the disease. This review will allow a better understanding of local immune parameters, including cellular and cytokines release in the lesion, that controls infection and/or protect against the pathogenesis in new world compared to old world CL.

Severe mucosal leishmaniasis with torpid and fatal evolution

Mucosal leishmaniasis is a clinical condition that is difficult to diagnose and treat and usually precedes a cutaneous leishmaniasis condition with a long latency period as observed in our study of a patient who experienced a torpid evolution in 9 months, caused by having had cutaneous leishmaniasis on the neck without therapeutic treatment, although with ulcer closure 18 years earlier, incomplete treatment with antimonials and amphotericin B, with the destruction of the eyeball, a large area of necrosis on the face and nasal bone exposure. Additionally, the patient had chronic anemia (9.4 g/dl), lymphopenia and neutrophilia (lymphocytes 13.1%, neutrophils 84.4%), and co‐infections by fungi (yeasts and hyphae) and Gram‐negative bacteria (multidrug‐resistant Proteus mirabilis and Escherichia coli) leading to sepsis and subsequent death of the patient.

Double-negative T cells: Setting the stage for disease control or progression

Double-negative (DN) T cells are present at relatively low frequencies in human peripheral blood, and are characterized as expressing the alpha-beta or gamma-delta T-cell receptor (TCR), but not the CD4 nor the CD8 co-receptors. Despite their low frequencies, these cells are potent producers of cytokines and, thus, are key orchestrators of immune responses. DN T cells were initially associated with induction of peripheral immunological tolerance and immunomodulatory activities related to disease prevention. However, other studies demonstrated that these cells can also display effector functions associated with pathology development. This apparent contradiction highlighted the heterogeneity of the DN T-cell population. Here, we review phenotypic and functional characteristics of DN T cells, emphasizing their role in human diseases. The need for developing biomarkers to facilitate the translation of studies from animal models to humans will also be discussed. Finally, we will examine DN T cells as promising therapeutic targets to prevent or inhibit human disease development.

Distinct CD4-CD8- (Double-Negative) Memory T-Cell Subpopulations Are Associated With Indeterminate and Cardiac Clinical Forms of Chagas Disease

CD4-CD8- (double-negative, DN) T cells are critical orchestrators of the cytokine network associated with the pathogenic inflammatory response in one of the deadliest cardiomyopathies known, Chagas heart disease, which is caused by Trypanosoma cruzi infection. Here, studying the distribution, activation status, and cytokine expression of memory DN T-cell subpopulations in Chagas disease patients without cardiac involvement (indeterminate form-IND) or with Chagas cardiomyopathy (CARD), we report that while IND patients displayed a higher frequency of central memory, CARD had a high frequency of effector memory DN T cells. In addition, central memory DN T cells from IND displayed a balanced cytokine profile, characterized by the concomitant expression of IFN-γ and IL-10, which was not observed in effector memory DN T cells from CARD. Supporting potential clinical relevance, we found that the frequency of central memory DN T cells was associated with indicators of better ventricular function, while the frequency of effector memory DN T cells was not. Importantly, decreasing CD1d-mediated activation of DN T cells led to an increase in IL-10 expression by effector memory DN T cells from CARD, restoring a balanced profile similar to that observed in the protective central memory DN T cells. Targeting the activation of effector memory DN T cells may emerge as a strategy to control inflammation in Chagas cardiomyopathy and potentially in other inflammatory diseases where these cells play a key role.

An old drug and different ways to treat cutaneous leishmaniasis: Intralesional and intramuscular meglumine antimoniate in a reference center, Rio de Janeiro, Brazil

Background

Treatment of cutaneous leishmaniasis (CL) remains challenging since the drugs currently used are quite toxic, thus contributing to lethality unrelated to the disease itself but to adverse events (AE). The main objective was to evaluate different treatment regimens with meglumine antimoniate (MA), in a reference center in Rio de Janeiro, Brazil.

Methodology

A historical cohort of 592 patients that underwent physical and laboratory examination were enrolled between 2000 and 2017. The outcome measures of effectiveness were epithelialization and complete healing of cutaneous lesions. AE were graded using a standardized scale. Three groups were evaluated: Standard regimen (SR): intramuscular (IM) MA 10–20 mg Sb⁵⁺/kg/day during 20 days (n = 46); Alternative regimen (AR): IM MA 5 mg Sb⁵⁺/kg/day during 30 days (n = 456); Intralesional route (IL): MA infiltration in the lesion(s) through subcutaneous injections (n = 90). Statistical analysis was performed through Fisher exact and Pearson Chi-square tests, Kruskal-Wallis, Kaplan-Meier and log-rank tests.

Results

SR, AR and IL showed efficacy of 95.3%, 84.3% and 75.9%, with abandonment rate of 6.5%, 2.4% and 3.4%, respectively. IL patients had more comorbidities (58.9%; p = 0.001), were mostly over 50 years of age (55.6%), and had an evolution time longer than 2 months (65.6%; p = 0.02). Time for epithelialization and complete healing were similar in IL and IM MA groups (p = 0.9 and p = 0.5; respectively). Total AE and moderate to severe AE that frequently led to treatment interruption were more common in SR group, while AR and IL showed less toxicity.

Conclusions/Significance

AR and IL showed less toxicity and may be good options especially in CL cases with comorbidities, although SR treatment was more effective. IL treatment was an effective and safe strategy, and it may be used as first therapy option as well as a rescue scheme in patients initially treated with other drugs.

Treatment of cutaneous leishmaniasis remains a challenge since the drugs used are quite toxic. Currently, there is a global effort to reduce the morbidity associated with the treatment of this disease and life-threatening complications due to drugs or treatment approaches. Meglumine antimoniate (MA) in different regimens was evaluated in cutaneous leishmaniasis patients in the state of Rio de Janeiro, Brazil. Effectiveness and toxicity were compared among the groups: standard regimen (SR) [intramuscular (IM) MA in the dosage of 10 to 20 mg of pentavalent antimony (Sb5⁺)/kg/day]; alternative regimen (AR) [IM MA in the dosage of 5 mg Sb5⁺/kg/day]; and intralesional route (IL) [patients treated with MA through the infiltration of the lesion]. AR and IL regimens demonstrated good effectiveness, with reduced abandonment rate and toxicity. Total adverse events were higher in the SR group, which frequently led to treatment interruptions. AR and IL showed less toxicity especially in CL cases with comorbidities, although SR treatment was more effective than AR and IL regimens. IL was an effective and safe treatment and may be used as a first therapy option as well as a rescue scheme.

Determinants of Unresponsiveness to Treatment in Cutaneous Leishmaniasis: A Focus on Anthroponotic Form Due to Leishmania tropica

Cutaneous leishmaniasis (CL) is a curable disease; however, due to various risk factors, unresponsiveness to CL treatments is inevitable. The treatment of CL has been firmly correlated with multiple determinants, such as demographical, clinical, and environmental factors, the host’s immune response, poor treatment adherence, the parasite’s genetic make-up, and Leishmania RNA virus. This study primarily focuses on the risk factors associated with different therapeutic outcomes following meglumine antimoniate (MA; Glucantime^®) treatment and policy approaches to prevent unresponsiveness in CL patients with a focus on anthroponotic form (ACL). Findings suggest that effective preventive and therapeutic measures should be more vigorously implemented, particularly in endemic areas. Accordingly, extensive training is essential to monitor drug unresponsiveness regularly, especially in tropical regions where the disease is prevalent. Since humans are the fundamental reservoir host of ACL due to L. tropica, prompt detection, early diagnosis, and timely and effective treatment could help control this disease. Furthermore, major challenges and gaps remain: efficacious vaccine, new tools, and expert staff are crucial before CL can be definitively controlled.

DNT Cell-based Immunotherapy: Progress and Applications

Cancer immunotherapy has firmly established a dominant status in recent years. Adoptive cellular immunotherapy (ACI) is the main branch of immunotherapy. Recently, the immune effector cells of ACI, such as T cells, NK cells, and genetically engineered cells, have been used to achieve significant clinical benefits in the treatment of malignant tumors. However, the clinical applications have limitations, including toxicity, unexpectedly low efficiency, high costs and strict technical requirements. More exploration is needed to optimize ACI for cancer patients. CD3+CD4-CD8- double negative T cells (DNTs) have emerged as functional antitumor effector cells, according to the definition of adoptive immunotherapy. They constitute a kind of T cell subset that mediates nontumor antigen-restricted immunity and has important immune regulatory functions. Preclinical experiments showed that DNTs had a dual effect by killing tumor cells and inhibiting graft-versus-host disease. Notably, DNTs can be acquired from healthy donors and expanded in vitro; thus, allogeneic DNTs may be provided as “off-the-shelf” cellular products that can be readily available for direct clinical application. We review the progress and application of DNTs in immunotherapy. DNTs may provide some novel perspectives on cancer immunotherapy.

Cutaneous Leishmaniasis: The Complexity of Host's Effective Immune Response against a Polymorphic Parasitic Disease

This review is aimed at providing a comprehensive outline of the immune response displayed against cutaneous leishmaniasis (CL), the more common zoonotic infection caused by protozoan parasites of the genus Leishmania. Although of polymorphic clinical presentation, classically CL is characterized by leishmaniotic lesions on the face and extremities of the patients, which can be ulcerative, and even after healing can lead to permanent injuries and disfigurement, affecting significantly their psychological, social, and economic well-being. According a report released by the World Health Organization, the disability-adjusted life years (DALYs) lost due to leishmaniasis are close to 2.4 million, annually there are 1.0–1.5 million new cases of CL, and a numerous population is at risk in the endemic areas. Despite its increasing worldwide incidence, it is one of the so-called neglected tropical diseases. Furthermore, this review provides an overview of the existing knowledge of the host innate and acquired immune response to cutaneous species of Leishmania. The use of animal models and of in vitro studies has improved the understanding of parasite-host interplay and the complexity of immune mechanisms involved. The importance of diagnosis accuracy associated with effective patient management in CL reduction is highlighted. However, the multiple factors involved in CL epizoology associated with the unavailability of vaccines or drugs to prevent infection make difficult to formulate an effective strategy for CL control.

Double-negative T cells remarkably promote neuroinflammation after ischemic stroke

CD3⁺CD4^-CD8^- T cells (double-negative T cells; DNTs) have diverse functions in peripheral immune-related diseases by regulating immunological and inflammatory homeostasis. However, the functions of DNTs in the central nervous system remain unknown. Here, we found that the levels of DNTs were dramatically increased in both the brain and peripheral blood of stroke patients and in a mouse model in a time-dependent manner. The infiltrating DNTs enhanced cerebral immune and inflammatory responses and exacerbated ischemic brain injury by modulating the FasL/PTPN2/TNF-α signaling pathway. Blockade of this pathway limited DNT-mediated neuroinflammation and improved the outcomes of stroke. Our results identified a critical function of DNTs in the ischemic brain, suggesting that this unique population serves as an attractive target for the treatment of ischemic stroke.

Host's immune response in unresponsive and responsive patients with anthroponotic cutaneous leishmaniasis treated by meglumine antimoniate: A case-control study of Th1 and Th2 pathways

The objective of the present study was to compare the host's immune responses between unresponsive and responsive patients with anthroponotic cutaneous leishmaniasis (ACL) treated by meglumine antimoniate. A case-control study was carried out in an endemic focus in Iran. Blood samples were taken from patients and peripheral blood mononuclear cells (PBMCs) were isolated. Two wells were considered for each isolate of unresponsive and responsive patients; one was exposed to L. tropica (Lt-stimulated cells) and the other remained non-exposed (non-stimulated cells). After 24 h of incubation, whole RNA was extracted from each sample. Real-time quantitative PCR was carried out to confirm the differences in expression levels of IL-12 P40, IFN-γ, IL-1β, IL-4 and IL-10 among isolates. Data were analyzed and P < 0.05 was considered to be statistically significant. In our study, Lt-stimulated cells and non-stimulated cells in unresponsive groups demonstrated significantly lower expression levels of IL-1β, IL-12 P40 and IFN-γ genes and higher expression levels of IL-4 and IL-10 genes, compared to Lt-stimulated cells and non-stimulated cells in responsive groups. There was a negative correlation between IL-12 P40 with IL-10 and IL-1β with IL-10 in ACL Lt-stimulated cells in unresponsive group, while a positive correlation between IL-12 P40 with IL-1β and IL-12 P40 with IFN-γ in ACL Lt-stimulated cells in responsive group. Probably, different immune responses caused by various factors play a major role in the pathogenesis and development of unresponsiveness in ACL patients. The profile and timing of cytokine production correlated well with the treatment outcome of Leishmania infection.

Schistosoma mansoni rSm29 Antigen Induces a Regulatory Phenotype on Dendritic Cells and Lymphocytes From Patients With Cutaneous Leishmaniasis

The immune response induced by Schistosma mansoni antigens is able to prevent immune-mediated diseases. Conversely, the inflammatory response in cutaneous leishmaniasis (CL), although responsible for controlling the infection, is also associated with the pathogenesis of disease. The aim of this study was to evaluate the potential of the S. mansoni Sm29 antigen to change certain aspects of the profiles of monocyte derived dendritic cells (MoDCs) and lymphocytes from subjects with CL in vitro. Expression of surface molecules and intracellular cytokines in the MoDCs and lymphocytes as well as the proliferation of Leishmania braziliensis were evaluated by flow cytometry. Levels of cytokines were evaluated in culture supernatants by ELISA. It was observed that stimulation by rSm29 increased the frequency of expression of CD83, CD80, CD86, and IL-10R in MoDCs compared to non-stimulated cultures. Additionally rSm29 decreased the frequency CD4⁺ and CD8⁺ T cells expressing CD28 and increased the frequency of CD4⁺CD25^hi and CD4⁺CTLA-4⁺ T lymphocytes. Addition of rSm29 to cultures increased IL-10 levels and decreased levels of IL-12p40 and IFN-γ, while not altering TNF levels compared to non-stimulated cultures. This study showed that rSm29 induced a regulatory profile in MoDCs and lymphocytes and thereby regulated the exaggerated inflammation observed in CL. Considering that there are few therapeutic options for leishmaniasis, the use of rSm29 may be an alternative to current treatment and may be an important strategy to reduce the healing time of lesions in patients with CL.

Gene expression profile of cytokines produced in biopsies from patients with American cutaneous leishmaniasis

American cutaneous leishmaniasis (ACL) causes a local inflammatory process, inducing expression of several cytokine genes. Particularly, IFN-γ can predict to disease susceptibility. Based in these data, this study was aimed to investigate the gene expression profile of IFN-γ, IL-10, IL-27, TNF-γ, TGF-β and IL-6 produced in biopsies from ACL patients; and whether the gene expression profile of IFN-γ could determine the disease evolution. Gene expression of 6 cytokines was investigated in 40 formalin-fixed paraffin embedded (FFPE) biopsies from patients with cutaneous leishmaniosis (CL); and 10 FFPE biopsies from patients with mucosal leishmaniasis (ML) (control). All 50 patients were infected with Leishmania (Viannia) braziliensis. Gene expression was determined by qPCR; and a normal control group was used for calculations (5 normal biopsies). Values were expressed as Relative Quantification (RQ). The 40 CL patients were classified into 2 groups. CLlowIFN-γ, 35 patients with RQ for IFN-γ below 100; and CLhighIFN-γ, 5 (12.5%) patients with RQ above 100. Significant increase of mRNA levels of IFN-γ, IL-10 and IL-27 was shown in CLhighIFN-γ group when compared with CLlowIFN-γ and ML groups. TNF-α levels in CLlowIFN-γ group were higher than CLhighIFN-γ and ML groups. TGF-β and IL-6 were similar in 3 groups. Comparison of cytokine expression/group showed that CLlowIFN-γ group had an equilibrium between the cytokines analyzed. In ML group, IFN-γ was over-expressed; but in CLhighIFN-γ group, besides IFN-γ, IL-27 was also over-expressed. The immune response to Leishmania induces to identification of some markers, which can be determined by analysis by gene expression of cytokines produced in biopsies.

The Binomial Parasite-Host Immunity in the Healing Process and in Reactivation of Human Tegumentary Leishmaniasis

Leishmaniasis is a vector-borne infectious disease caused by different species of protozoa from the Leishmania genus. Classically, the disease can be classified into two main clinical forms: Visceral (VL) and Tegumentary (TL) leishmaniasis. TL is a skin/mucosal granulomatous disease that manifests mainly as cutaneous localized or disseminated ulcers, papules diffusely distributed, mucosal lesions or atypical lesions. Once the etiology of the infection is confirmed, treatment can take place, and different drugs can be administered. It has already been shown that, even when the scar is clinically evident, inflammation is still present in the native tissue, and the decrease of the inflammatory process occurs slowly during the 1st years after clinical healing. The maintenance of residual parasites in the scar tissue is also well documented. Therefore, it is no longer a surprise that, under some circumstances, therapeutic failure and/or lesion reactivation occurs. All over the years, an impressive amount of data on relapses, treatment resistance and lesion reactivation after healing has been collected, and several factors have been pointed out as having a role in the process. Different factors such as Leishmania species, parasite variability, Leishmania RNA virus 1, parasite load, parasite persistence, age, nutritional status, gender, co-morbidities, co-infection, pregnancy, immunosuppression, lesion duration, number and localization of lesions, drug metabolism, irregular treatment and individual host cellular immune response were described and discussed in the present review. Unfortunately, despite this amount of information, a conclusive understanding remains under construction. In addition, multifactorial influence cannot be discarded. In this context, knowing why leishmaniasis has been difficult to treat and control can help the development of new approaches, such as drugs and immunotherapy in order to improve healing maintenance. In this sense, we would like to highlight some of the findings that may influence the course of Leishmania infection and the therapeutic response, with an emphasis on TL.

Clinical and laboratory profiles of patients with early spontaneous healing in cutaneous localized leishmaniasis: a historical cohort study

BACKGROUND

Skin ulcers in American cutaneous leishmaniasis (ACL) may heal spontaneously after months/years. However, few cases may present quick heal even during diagnosis procedure (early spontaneous healing- ESH). The main objective of this study was to compare ESH patients with cases requiring specific treatment [non-ESH (NESH)].

METHODS

A historical cohort study of ACL patients (n = 445) were divided into 2 groups: ESH - spontaneously healed patients (n = 13; 2.90%), and NESH- treated patients (n = 432; 97.10%). We compared clinical and laboratorial findings at diagnosis, including the lesion healing process.

RESULTS

ESH patients had a higher percentage of single lesions (p = 0.027), epithelialized lesion on initial examination (p = 0.001), lesions located in the dorsal trunk (p = 0.017), besides earlier healing (p < 0.001). NESH presents higher frequency of ulcerated lesions (p = 0.002), amastigotes identified in histopathology exams (p = 0.005), positive cultures (p = 0.001), and higher positivity in ≥3 parasitological exams (p = 0.030). All ESH cases were positive in only a single exam, especially in PCR.

CONCLUSIONS

ESH group apparently presented a lower parasitic load evidenced by the difficulty of parasitological confirmation and its positivity only by PCR method. The absence or deficiency of specific treatment is commonly identified as predisposing factors for recurrence and metastasis in ACL. However, due to the drugs toxicity, the treatment of cases which progress to early spontaneous healing is controversial. ESH patients were followed for up to 5 years after cure, with no evidence of recrudescence, therefore suggesting that not treating these patients is justifiable, but periodic dermatological and otorhinolaryngological examinations are advisable to detect a possible relapse.

CD3+CD4negCD8neg (double negative) T lymphocytes and NKT cells as the main cytotoxic-related-CD107a+ cells in lesions of cutaneous leishmaniasis caused by Leishmania (Viannia) braziliensis

Background

Cutaneous leishmaniasis (CL) is caused by Leishmania (Viannia) braziliensis, which infects dermal macrophages and dendritic cells, causing an intense immune-mediated-tissue inflammation and a skin ulcer with elevated borders that can heal spontaneously or after antimonial therapy. The resolution of lesions depends on an adaptive immune response, and cytotoxic cells seem to have a fundamental role in this process. The aim of this study is to better understand the role of cytotoxicity mediated mechanisms that occur during the immune response in the CL lesion milieu, considering distinct cytotoxic-related CD107a⁺ cells, such as CD8⁺, CD4⁺, CD4^neg CD8^neg (double-negative, DN) and CD4⁺CD8⁺ (double-positive, DP) T lymphocytes, as well as NK and NKT cells.

Methods

Lesion derived cells were assessed for T cell subpopulations and NK cells, as well as CD107a expression by flow cytometry. In addition, cytometric bead array (CBA) was used to quantify cytokines and granzyme B concentrations in supernatants from macerated lesions.

Results

Flow cytometry analyses revealed that NKT cells are the major CD107a-expressing cell population committed to cytotoxicity in CL lesion, although we also observed high frequencies of CD4⁺ and DN T cells expressing CD107a. Analysing the pool of CD107a⁺-cell populations, we found a higher distribution of DN T cells (44%), followed by approximately 25% of NKT cells. Interestingly, NK and CD8⁺ T cells represented only 3 and 4% of the total-CD107a⁺-cell pool, respectively.

Conclusions

The cytotoxicity activity that occurs in the lesion milieu of CL patients seems to be dominated by DN T and NKT cells. These findings suggest the need for a reevaluation of the role of classical-cytotoxic NK and CD8⁺ T cells in the pathogenesis of CL, implicating an important role for other T cell subpopulations.

Leishmaniavirus-Dependent Metastatic Leishmaniasis Is Prevented by Blocking IL-17A

Cutaneous leishmaniasis has various outcomes, ranging from self-healing reddened papules to extensive open ulcerations that metastasise to secondary sites and are often resistant to standard therapies. In the case of L. guyanensis (L.g), about 5-10% of all infections result in metastatic complications. We recently showed that a cytoplasmic virus within L.g parasites (LRV1) is able to act as a potent innate immunogen, worsening disease outcome in a murine model. In this study, we investigated the immunophenotype of human patients infected by L.g and found a significant association between the inflammatory cytokine IL-17A, the presence of LRV1 and disease chronicity. Further, IL-17A was inversely correlated to the protective cytokine IFN-γ. These findings were experimentally corroborated in our murine model, where IL-17A produced in LRV1+ L.g infection contributed to parasite virulence and dissemination in the absence of IFN-γ. Additionally, IL-17A inhibition in mice using digoxin or SR1001, showed therapeutic promise in limiting parasite virulence. Thus, this murine model of LRV1-dependent infectious metastasis validated markers of disease chronicity in humans and elucidated the immunologic mechanism for the dissemination of Leishmania parasites to secondary sites. Moreover, it confirms the prognostic value of LRV1 and IL-17A detection to prevent metastatic leishmaniasis in human patients.

The Immunology of a Healing Response in Cutaneous Leishmaniasis Treated with Localized Heat or Systemic Antimonial Therapy

Background

The effectiveness of systemic antimonial (sodium stibogluconate, Pentostam, SSG) treatment versus local heat therapy (Thermomed) for cutaneous leishmaniasis was studied previously and showed similar healing rates. We hypothesized that different curative immune responses might develop with systemic and local treatment modalities.

Methods

We studied the peripheral blood immune cells in a cohort of 54 cutaneous Leishmania major subjects treated with SSG or TM. Multiparameter flow cytometry, lymphoproliferative assays and cytokine production were analyzed in order to investigate the differences in the immune responses of subjects before, on and after treatment.

Results

Healing cutaneous leishmaniasis lead to a significant decline in circulating T cells and NKT-like cells, accompanied by an expansion in NK cells, regardless of treatment modality. Functional changes involved decreased antigen specific CD4⁺ T cell proliferation (hyporesponsiveness) seen with CD8⁺ T cell depletion. Moreover, the healing (or healed) state was characterized by fewer circulating regulatory T cells, reduced IFN-γ production and an overall contraction in polyfunctional CD4⁺ T cells.

Conclusion

Healing from cutaneous Leishmaniasis is a dynamic process that alters circulating lymphocyte populations and subsets of T, NK and NKT-like cells. Immunology of healing, through local or systemic treatments, culminated in similar changes in frequency, quality, and antigen specific responsiveness with immunomodulation possibly via a CD8⁺ T cell dependent mechanism. Understanding the evolving immunologic changes during healing of human leishmaniasis informs protective immune mechanisms.

Globally, leishmaniasis treatment relies on the use of antimonial drugs (i.e. SSG). In an earlier study we showed that skin lesions due to L. major treated by the ThermoMed (TM) device healed at a similar rate and with less associated systemic toxicity than lesions treated with intravenous SSG. The current study compared the immune responses of these two therapeutic groups before, during and after therapy which may be relevant to resistance to reinfection and also in consideration for the development of local (versus systemic) therapy. Antimonials have immune effects on both the host and parasite while heat treatment locally kills the parasite and induces inflammation from a secondary burn. We demonstrated that healing from cutaneous leishmaniasis is a dynamic process associated with a modulation of immune responses independent of treatment modalities.

American tegumentary leishmaniasis: mRNA expression for Th1 and Treg mediators are predominant in patients with recent active disease

Besides the Th1×Th2 paradigm, Treg and Th17 cytokines may play a role in the response to American tegumentary leishmaniasis. Considering the sensitivity and accuracy of qPCR and the lack of studies using this approach, we evaluated mRNA expression for IFN-γ, TNF-α, IL-4, IL-10, IL-6, IL-17A, IL-22, TGF-β, Foxp3 and RORC in peripheral blood mononuclear cells (PBMC) from patients with active disease, after stimulation with L. (V.) braziliensis soluble or insoluble fractions. Our results show that the antigens promoted specific mRNA expression related to the immune response in patients with ATL, and the insoluble fraction seems to stimulate the immune response in a higher intensity. The pro-inflammatory response was also fueled by IFN-γ and TNF-α, probably due to the active disease. IL-4, in certain way, seems to regulate this response along with IL-10 that may be produced by Treg cells, which are supposedly present in the patients' samples due the evidenced expression of Foxp3, in the presence of AgIns. In contrast, down-regulated RORC suggests that the significant levels of IL-6 expressed in response to AgSol were not able to induce an expressive Th17 profile along with TGF-β, which might have predominantly contributed to the development of a regulatory profile in the active disease.

Protective and pathological functions of CD8+ T cells in Leishmania braziliensis infection

Cutaneous leishmaniasis (CL) caused by Leishmania braziliensis is characterized by a strong Th1 response that leads to skin lesion development. In areas where L. braziliensis transmission is endemic, up to 15% of healthy subjects have tested positive for delayed-type hypersensitivity to soluble leishmania antigen (SLA) and are considered to have subclinical (SC) infection. SC subjects produce less gamma interferon (IFN-γ) and tumor necrosis factor alpha (TNF-α) than do CL patients, but they are able to control the infection. The aim of this study was to characterized the role of CD8(+) T cells in SC infection and in CL. Peripheral blood mononuclear cells (PBMC) were stimulated with SLA to determine the frequencies of CD4(+) IFN-γ(+) and CD8(+) IFN-γ(+) T cells. Monocytes from PBMC were infected with L. braziliensis and cocultured with CD8(+) T cells, and the frequencies of infected monocytes and levels of cytotoxicity markers, target cell apoptosis, and granzyme B were determined. The frequency of CD8(+) IFN-γ(+) cells after SLA stimulation was higher for SC individuals than for CL patients. The frequency of infected monocytes in SC cells was lower than that in CL cells. CL CD8(+) T cells induced more apoptosis of infected monocytes than did SC CD8(+) T cells. Granzyme B production in CD8(+) T cells was higher in CL than in SC cells. While the use of a granzyme B inhibitor decreased the number of apoptotic cells in the CL group, the use of z-VAD-FMK had no effect on the frequency of these cells. These results suggest that CL CD8(+) T cells are more cytotoxic and may be involved in pathology.

Immunoregulation in human American leishmaniasis: balancing pathology and protection

Leishmaniasis covers a broad spectrum of diseases with distinct, and sometimes overlapping, characteristics. The common thread in all forms of leishmaniasis is the infection by the parasite Leishmania belonging to the genus Leishmania. Upon infection of humans, there can be at least three outcomes, (i) control of Leishmania by the host immune response resulting in asymptomatic disease, (ii) patent infection and development of a relatively mild form of leishmaniasis and (iii) patent infection and development of severe clinical forms. The factors that determine the outcome of an initial inoculation with Leishmania are many, with the species of Leishmania representing one of the strongest predictive factors for the development of a given clinical form of disease. This is seen with L. braziliensis and L. amazonensis, infection leading mostly to tegumentary forms of disease, and L. infantum with the potential to induce visceral disease. However, it is also clear that the host immune response is a key factor in disease progression, not only responsible for control of Leishmania, but also playing an important role in disease progression and pathology. This duality between protective and pathogenic immune responses in individuals infected with Leishmania in the Americas is the focus of this review.

MHC class II restricted innate-like double negative T cells contribute to optimal primary and secondary immunity to Leishmania major

Although it is generally believed that CD4⁺ T cells play important roles in anti-Leishmania immunity, some studies suggest that they may be dispensable, and that MHC II-restricted CD3⁺CD4⁻CD8⁻ (double negative, DN) T cells may be more important in regulating primary anti-Leishmania immunity. In addition, while there are reports of increased numbers of DN T cells in Leishmania-infected patients, dogs and mice, concrete evidence implicating these cells in secondary anti-Leishmania immunity has not yet been documented. Here, we report that DN T cells extensively proliferate and produce effector cytokines (IFN-γ, TNF and IL-17) and granzyme B (GrzB) in the draining lymph nodes and spleens of mice following primary and secondary L. major infections. DN T cells from healed mice display functional characteristics of protective anti-Leishmania memory-like cells: rapid and extensive proliferation and effector cytokines production following L. major challenge in vitro and in vivo. DN T cells express predominantly (> 95%) alpha-beta T cell receptor (αβ TCR), are Leishmania-specific, restricted mostly by MHC class II molecules and display transcriptional profile of innate-like genes. Using in vivo depletion and adoptive transfer studies, we show that DN T cells contribute to optimal primary and secondary anti-Leishmania immunity in mice. These results directly identify DN T cells as important players in effective and protective primary and secondary anti-L. major immunity in experimental cutaneous leishmaniasis.

Although it is generally believed that CD4⁺ T cells mediate anti-Leishmania immunity, some studies suggest that CD3⁺CD4⁻CD8⁻ (double negative, DN) T cells may play a more important role in regulating primary anti-Leishmania immunity. Here, we report that DN T cells extensively proliferate and produce effector cytokines in mice following primary and secondary L. major infections. Leishmania-reactive DN T cells utilize αβ T cell receptor (TCR) and are restricted by MHC class II molecules. Strikingly, DN T cells from healed mice display functional characteristics of protective anti-Leishmania memory-like cells: rapid and extensive proliferation, effector cytokine production in vitro and in vivo, and accelerated parasite control following secondary L. major challenge. These results directly identify DN T cells as important players in protective primary and secondary anti-L. major immunity in experimental cutaneous leishmaniasis.

Dynamic identification of H2 epitopes from Leishmania (Leishmania) amazonensis cysteine proteinase B with potential immune activity during murine infection

Peptides from the COOH-terminal extension of cysteine proteinase B from Leishmania (Leishmania) amazonensis (cyspep) can modulate immune responses in vertebrate hosts. With this hypothesis as base, we used the online analysis tool SYFPEITHI to predict seven epitopes from this region with potential to bind H2 proteins. We performed proliferation tests and quantified reactive T lymphocytes applying a cytometry analysis, using samples from draining lymph node of lesions from L. (L.) amazonensis-infected mice. To define reactivity of T cells, we used complexes of DimerX (H2 D(b):Ig and H2 L(d):Ig) and the putative epitopes. Additionally, we applied surface plasmon resonance to verify real time interactions between the putative epitopes and DimerX proteins. Five peptides induced blastogenesis in BALB/c cells, while only two presented the same property in C57BL/6 mouse cells. In addition, our data indicate the existence of CD8+ T lymphocyte populations able to recognize each tested peptide in both murine strains. We observed an overlapping of results between the peptides that induced lymphocyte proliferation and those capable of binding to the DimerX in the surface plasmon resonance assays thus indicating that using these recombinant proteins in biosensing analyses is a promising tool to study real time molecular interactions in the context of major histocompatibility complex epitopes. The data gathered in this study reinforce the hypothesis that cyspep-derived peptides are important factors in the murine host infection by L. (L.) amazonensis.

Immune responses during cutaneous and visceral leishmaniasis

SUMMARY Leishmania are protozoan parasites spread by a sandfly insect vector and causing a spectrum of diseases collectively known as leishmaniasis. The disease is a significant health problem in many parts of the world, resulting in an estimated 1·3 million new cases and 30 000 deaths annually. Current treatment is based on chemotherapy, which is difficult to administer, expensive and becoming ineffective in several endemic regions. To date there is no vaccine against leishmaniasis, although extensive evidence from studies in animal models indicates that solid protection can be achieved upon immunization. This review focuses on immune responses to Leishmania in both cutaneous and visceral forms of the disease, pointing to the complexity of the immune response and to a range of evasive mechanisms utilized by the parasite to bypass those responses. The amalgam of innate and acquired immunity combined with the paucity of data on the human immune response is one of the major problems currently hampering vaccine development and implementation.

Immunoregulatory profile of monocytes from cutaneous leishmaniasis patients and association with lesion size

Leishmaniasis is an important tropical disease composed of several clinical forms that adversely affect millions of people globally. Critical cells involved in the host-Leishmania interaction are monocytes and macrophages, which act to protect against infections due to their ability to both control intracellular infections and regulate the subsequent adaptive immune response. Both soluble factors and cell surface receptors are keys in directing the immune response following interaction with pathogens such as Leishmania. Toll-like receptors (TLRs) have an essential role in immune responses against infections, but little is known about their role in human infection with Leishmania braziliensis. In this work, we evaluated peripheral blood CD14+ monocytes for the expression of immunoregulatory cytokines, co-stimulatory molecules and TLR9 from cutaneous leishmaniasis patients infected with L. braziliensis and noninfected individuals. Our results showed that patients present decreased expression of co-stimulatory molecules such as CD80 and CD86 following culture with media alone or after stimulus with soluble Leishmania antigen. Interestingly, TLR9 expression was higher after culture with soluble Leishmania antigen (SLA), suggesting a role of this molecule in immunoregulation of active disease. Lastly, higher frequencies of TLR9+ monocytes were correlated with greater lesion size. These findings demonstrate a peripheral monocytes profile compatible with important immunoregulatory potential.

Cytokines and NO in American tegumentary leishmaniasis patients: profiles in active disease, after therapy and in self-healed individuals

Studies suggest the influence of immune response on the successful treatment of American tegumentary leishmaniasis (ATL), and indicate the existence of protective immunity in self-healed patients. Thus, the aim of this work was to quantify interferon-gamma (IFN-γ), tumor necrosis factor-alpha (TNF-α), interleukin (IL-) 10, IL-17, IL-22 and nitric oxide (NO) in culture supernatants of PBMC from patients with active disease (AD), after treatment (AT), and from self-healed (SH) and healthy subjects (CT), in response to Leishmania (Viannia) braziliensis insoluble antigen (AgIns). All groups of patients produced IFN-γ, indicating a predominant proinflammatory profile. AD and AT patients presented TNF-α levels, with a slight increase after therapy, whereas it was weakly quantified in SH. Interestingly, NO secretion was significant in these individuals, whereas IL-17 appeared in low levels and seems to be regulated by NO. Although IL-22 was detected in AD, its role is still questionable. The presence of IL-10 in all groups of patients suggests that the cytokine plays distinct roles in the disease. These results indicate that specific cellular immunity takes part against Leishmania, but with some similarities between the different clinical states herein described; these mediators seem to be necessary for the cure to occur.

American tegumentary leishmaniasis: cytokines and nitric oxide in active disease and after clinical cure, with or without chemotherapy

The influence of immune response on the treatment of American tegumentary leishmaniasis is pointed by several authors, and the existence of protective immunity in self-healed patients (SH) is also suggested. Thus, interferon-gamma (IFN-γ), tumour necrosis factor-alpha (TNF-α), interleukin (IL-) 10, IL-17, IL-22 and nitric oxide (NO) production was determined in PBMC culture supernatants from patients with active disease (AD) and after therapy, SH patients and healthy subjects, in response to the soluble antigen of Leishmania (Viannia) braziliensis. It was demonstrated that, during the active disease, there is a predominance of IFN-γ and TNF-α, indicating a proinflammatory phase of the response; IL-17 is also highlighted at this clinical state. Also, TNF-α was slightly increased in patients after therapy. NO secretion was noticed in SH individuals, while IL-17 appeared in low levels in these patients and seems to be regulated by NO. The presence of IL-10 was observed in all groups of patients. From this study, we can suggest that in the active disease and after clinical cure, with or without chemotherapy, specific cellular immunity takes part against Leishmania, but with some similarities between the clinical states. Thus, it indicates that the mediators herein described are necessary for the cure to occur.

Local inflammation is associated with aortic thrombus formation in abdominal aortic aneurysms. Relationship to clinical risk factors

Intraluminal thrombus formation in aortic abdominal aneurysms (AAA) is associated with adverse clinical prognosis. Interplay between coagulation and inflammation, characterised by leukocyte infiltration and cytokine production, has been implicated in AAA thrombus formation. We studied leukocyte (CD45+) content by flow cytometry in AAA thrombi from 27 patients undergoing surgical repair. Luminal parts of thrombi were leukocyte-rich, while abluminal segments showed low leukocyte content. CD66b+ granulocytes were the most prevalent, but their content was similar to blood. Monocytes (CD14+) and T cells (CD3+) were also abundant, while content of B lymphocytes (CD19+) and NK cells (CD56+CD16+) were low. Thrombi showed comparable content of CD14highCD16- monocytes and lower CD14highCD16+ and CD14dimCD16+, than blood. Monocytes were activated with high CD11b, CD11c and HLA-DR expression. Total T cell content was decreased in AAA thrombus compared to peripheral blood but CD8 and CD3+CD4-CD8- (double negative T cell) contents were increased in thrombi. CD4+ cells were lower but highly activated (high CD69, CD25 and HLA-DR). No differences in T regulatory (CD4+CD25+FoxP3+) cell or pro-atherogenic CD4+CD28null lymphocyte content were observed between thrombi and blood. Thrombus T cells expressed high levels of CCR5 receptor for chemokine RANTES, commonly released from activated platelets. Leukocyte or T cell content in thrombi was not correlated with aneurysm size. However, CD3+ content was significantly associated with smoking in multivariate analysis taking into account major risk factors for atherosclerosis. In conclusion, intraluminal AAA thrombi are highly inflamed, predominantly with granulocytes, CD14highCD16- monocytes and activated T lymphocytes. Smoking is associated with T cell infiltration in AAA intraluminal thrombi.

Foreskin T-cell subsets differ substantially from blood with respect to HIV co-receptor expression, inflammatory profile, and memory status

The foreskin is the main site of heterosexual human immunodeficiency virus (HIV) acquisition in uncircumcised men, but functional data regarding T-cell subsets present at this site are lacking. Foreskin tissue and blood were obtained from Ugandan men undergoing elective adult circumcision. Tissue was treated by mechanical and enzymatic digestion followed by T-cell subset identification and assessment of cytokine production using flow cytometry. Foreskin CD4(+) T cells were predominantly an effector memory phenotype, and compared with blood they displayed a higher frequency of CCR5 expression (42.0% vs. 9.9%) and interleukin-17 production. There was no difference in T-regulatory cell frequency, but interferon-γ and tumor necrosis factor-α production were increased in foreskin CD8(+) T cells. These novel techniques demonstrate that the foreskin represents a proinflammatory milieu that is enriched for HIV-susceptible T-cell subsets. Further characterization of foreskin T-cell subsets may help to define the correlates of HIV susceptibility in the foreskin.

Altered T cell memory and effector cell development in chronic lymphatic filarial infection that is independent of persistent parasite antigen

Chronic lymphatic filarial (LF) infection is associated with suppression of parasite-specific T cell responses that persist even following elimination of infection. While several mechanisms have been implicated in mediating this T cell specific downregulation, a role for alterations in the homeostasis of T effector and memory cell populations has not been explored. Using multiparameter flow cytometry, we investigated the role of persistent filarial infection on the maintenance of T cell memory in patients from the filarial-endemic Cook Islands. Compared to filarial-uninfected endemic normals (EN), microfilaria (mf) positive infected patients (Inf) had a reduced CD4 central memory (T_CM) compartment. In addition, Inf patients tended to have more effector memory cells (T_EM) and fewer effector cells (T_EFF) than did ENs giving significantly smaller T_EFF ∶ T_EM ratios. These contracted T_CM and T_EFF populations were still evident in patients previously mf+ who had cleared their infection (CLInf). Moreover, the density of IL-7Rα, necessary for T memory cell maintenance (but decreased in T effector cells), was significantly higher on memory cells of Inf and CLInf patients, although there was no evidence for decreased IL-7 or increased soluble IL7-Rα, both possible mechanisms for signaling defects in memory cells. However, effector cells that were present in Inf and CLInf patients had lower percentages of HLA-DR suggesting impaired function. These changes in T cell populations appear to reflect chronicity of infection, as filarial-infected children, despite the presence of active infection, did not show alterations in the frequencies of these T cell phenotypes. These data indicate that filarial-infected patients have contracted T_CM compartments and a defect in effector cell development, defects that persist even following clearance of infection. The fact that these global changes in memory and effector cell compartments do not yet occur in infected children makes early treatment of LF even more crucial.

Murine model of chronic L. (Viannia) panamensis infection: role of IL-13 in disease

Leishmania (Viannia) organisms are the most prevalent etiologic agents of human cutaneous leishmaniasis in the Americas. Nevertheless, our knowledge of the immunological mechanisms exploited by L. (Viannia) organisms remains limited and the mechanisms underlying disease are not well understood. Here, we report the development of a BALB/c mouse model of L. (V.) panamensis infection that is able to reproduce chronic disease, with persistent infection and clinically evident lesions for over 1 year. The immune response of the mouse resembles that found for L. (V.) panamensis-infected patients with chronic and recurrent lesions, presenting a mixed Th1/Th2 response with the presence of TNF-α, IFN-γ, IL-10 and IL-13. Using immunodeficient mice, the critical role for IL-13 and/or IL-4Rα in determining susceptibility to chronic infection was evident. With the induction of healing in the immunodeficient mice, increases in IFN-γ and IL-17 were found, concomitant with parasite control and elimination. Specifically, increases in CD4(+) (but not CD8(+)) T cells producing IFN-γ were observed. These results suggest that IL-13 represents an important target for disease control of L. (V.) panamensis infection. This murine model should be useful to further understand the pathology associated with chronic disease and to develop methods for the treatment and prevention of leishmaniasis caused by L. (Viannia) parasites.

Trypanosoma cruzi-induced activation of functionally distinct αβ and γδ CD4- CD8- T cells in individuals with polar forms of Chagas' disease

CD4(-) CD8(-) (double-negative [DN]) T cells have recently been shown to display important immunological functions in human diseases. They express γδ or αβ T-cell receptors that recognize lipid/glycolipid antigens presented via the nonclassical major histocompatibility complex molecules of the CD1 family. We recently demonstrated that while αβ DN T cells serve primarily to express inflammatory cytokines, γδ DN T cells express mainly interleukin-10 (IL-10) in patients with cutaneous leishmaniasis. We also demonstrated a correlation between DN T cells and the expression of gamma interferon in the acute phase of Trypanosoma cruzi experimental infection. In this work, we sought to investigate whether αβ or γδ DN T cells display distinct immunoregulatory potentials in patients with polar forms of human Chagas' disease. Our data showed that in vitro infection with T. cruzi leads to expansion of DN T cells in patients with the indeterminate and severe cardiac clinical forms of the disease. However, while αβ DN T cells primarily produce inflammatory cytokines in both forms of the disease, γδ DN T cells display a marked, significant increase in antigen-specific IL-10 expression in indeterminate patients relative to cardiac patients. Finally, higher frequencies of the IL-10-producing γδ DN T cells were correlated with improved clinical measures of cardiac function in the patients, suggesting a protective role for these cells in Chagas' disease. Taken together, these data show distinct functional characteristics for αβ and γδ DN T cells associated with distinct morbidity rates and clinical forms in human Chagas' disease.

Cellular and genetic mechanisms involved in the generation of protective and pathogenic immune responses in human Chagas disease

Perhaps one of the most intriguing aspects of human Chagas disease is the complex network of events that underlie the generation of protective versus pathogenic immune responses during the chronic phase of the disease. While most individuals do not develop patent disease, a large percentage may develop severe forms that eventually lead to death. Although many efforts have been devoted to deciphering these mechanisms, there is still much to be learned before we can fully understand the pathogenesis of Chagas disease. It is clear that the host's immune response is decisive in this process. While characteristics of the parasite influence the immune response, it is becoming evident that the host genetic background plays a fundamental role in the establishment of pathogenic versus protective responses. The involvement of three complex organisms, host, parasite and vector, is certainly one of the key aspects that calls for multidisciplinary approaches towards the understanding of Chagas disease. We believe that now, one hundred years after the discovery of Chagas disease, it is imperative to continue with highly interactive research in order to elucidate the immune response associated with disease evolution, which will be essential in designing prophylactic or therapeutic interventions.

Multivariate statistical analyses demonstrate unique host immune responses to single and dual lentiviral infection

Background

Feline immunodeficiency virus (FIV) and human immunodeficiency virus (HIV) are recently identified lentiviruses that cause progressive immune decline and ultimately death in infected cats and humans. It is of great interest to understand how to prevent immune system collapse caused by these lentiviruses. We recently described that disease caused by a virulent FIV strain in cats can be attenuated if animals are first infected with a feline immunodeficiency virus derived from a wild cougar. The detailed temporal tracking of cat immunological parameters in response to two viral infections resulted in high-dimensional datasets containing variables that exhibit strong co-variation. Initial analyses of these complex data using univariate statistical techniques did not account for interactions among immunological response variables and therefore potentially obscured significant effects between infection state and immunological parameters.

Methodology and Principal Findings

Here, we apply a suite of multivariate statistical tools, including Principal Component Analysis, MANOVA and Linear Discriminant Analysis, to temporal immunological data resulting from FIV superinfection in domestic cats. We investigated the co-variation among immunological responses, the differences in immune parameters among four groups of five cats each (uninfected, single and dual infected animals), and the “immune profiles” that discriminate among them over the first four weeks following superinfection. Dual infected cats mount an immune response by 24 days post superinfection that is characterized by elevated levels of CD8 and CD25 cells and increased expression of IL4 and IFNγ, and FAS. This profile discriminates dual infected cats from cats infected with FIV alone, which show high IL-10 and lower numbers of CD8 and CD25 cells.

Conclusions

Multivariate statistical analyses demonstrate both the dynamic nature of the immune response to FIV single and dual infection and the development of a unique immunological profile in dual infected cats, which are protected from immune decline.

Meglumine antimonate directly increases phagocytosis, superoxide anion and TNF-alpha production, but only via TNF-alpha it indirectly increases nitric oxide production by phagocytes of healthy individuals, in vitro

Leishmania has developed mechanisms to escape from immune defense of phagocytes by inhibiting microbicidal oxygen and nitrogen radicals. This work evaluated the influence of meglumine antimonate (Sb(V)) on the phagocyte functions involved in the defense against leishmania, through phagocytosis, reactive oxygen, nitrogen and TNF-alpha production in the absence or presence of the drug, in vitro. Meglumine antimonate increased the number of Saccharomyces cerevisiae ingested by monocyte and the percentage of these cells engaged in phagocytosis, which resulted in an increase of the monocyte phagocytic index by 158%. Meglumine antimonate also increased the number of S. cerevisiae ingested by neutrophil and the percentage of these cells engaged in phagocytosis, increasing the neutrophil phagocytic index by 219%. The median of percent reduction of NBT was significantly increased after treatment with this pentavalent antimony from 89.5% to 96.5%. Meglumine antimonate had no influence on nitric oxide production, but it significantly increased the mean+/-SEM production of tumor necrosis factor by 230%. However, monocytes incubated with TNF significantly increased NO production. This antimonial increased the phagocytic capacity of monocytes and neutrophils and enhanced superoxide anion production by phagocytes, which represent the first line of defense against the parasite. Furthermore, meglumine antimonate increased TNF, and via this cytokine, it may also indirectly increase NO production. Our data suggest that these immunomodulatory effects of meglumine antimonate may play a role in fighting leishmania and that meglumine antimonate provides the phagocytes with a mechanism that prevents leishmania from escaping immune defense.