Involvement of Different CD4 + T Cell Subsets Producing Granzyme B in the Immune Response to Leishmania major Antigens

The nature of effector cells and the potential immunogenicity of Leishmania major excreted/secreted proteins (LmES) were evaluated using peripheral blood mononuclear cells (PBMCs) from healed zoonotic cutaneous leishmaniasis individuals (HZCL) and healthy controls (HC). First, we found that PBMCs from HZCL individuals proliferate and produce high levels of IFN-and granzyme B (GrB), used as a marker of activated cytotoxic T cells, in response to the parasite antigens. IFN-is produced by CD4 + T cells, but unexpectedly GrB is also produced by CD4 + T cells in response to stimulation with LmES, which were found to be as effective as soluble Leishmania antigens to induce proliferation and cytokine production by PBMCs from immune individuals. To address the question of regulatory T cell (Tregs) involvement, the frequency of circulating Tregs was assessed and found to be higher in HZCL individuals compared to that of HC. Furthermore, both CD4 + CD25 + and CD4 + CD25 − T cells, purified from HZCL individuals, produced IFN-and GrB when stimulated with LmES. Additional experiments showed that CD4 + CD25 + CD127 dim/− Tregs were involved in GrB production. Collectively, our data indicate that LmES are immunogenic in humans and emphasize the involvement of CD4 + T cells including activated and regulatory T cells in the immune response against parasite antigens

Human cellular and humoral immune responses to Phlebotomus papatasi salivary gland antigens in endemic areas differing in prevalence of Leishmania major infection

International audienceBACKGROUND:Sand fly saliva compounds are able to elicit specific immune responses that have a significant role in Leishmania parasite establishment and disease outcome. Characterizing anti-saliva immune responses in individuals living in well defined leishmaniasis endemic areas would provide valuable insights regarding their effect on parasite transmission and establishment in humans.METHODOLOGY/PRINCIPAL FINDINGS:We explored the cellular and humoral immune responses to Phlebotomus (P.) papatasi salivary gland extracts (SGE) in individuals living in cutaneous leishmaniasis (CL) old or emerging foci (OF, EF). OF was characterized by a higher infection prevalence as assessed by higher proportions of leishmanin skin test (LST) positive individuals compared to EF. Subjects were further subdivided into healed, asymptomatic or naïve groups. We showed anti-SGE proliferation in less than 30% of the individuals, regardless of the immune status, in both foci. IFN-γ production was higher in OF and only observed in immune individuals from OF and naïve subjects from EF. Although IL-10 was not detected, addition of anti-human IL-10 antibodies revealed an increase in proliferation and IFN-γ production only in individuals from OF. The percentage of seropositive individuals was similar in immune and naïves groups but was significantly higher in OF. No correlation was observed between anti-saliva immune responses and LST response. High anti-SGE-IgG responses were associated with an increased risk of developing ZCL. No differences were observed for anti-SGE humoral or cellular responses among naïve individuals who converted or not their LST response or developed or not ZCL after the transmission season.CONCLUSIONS/SIGNIFICANCE:These data suggest that individuals living in an old focus characterized by a frequent exposure to sand fly bites and a high prevalence of infection, develop higher anti-saliva IgG responses and IFN-γ levels and a skew towards a Th2-type cellular response, probably in favor of parasite establishment, compared to those living in an emerging focus

Involvement of Different CD4+ T Cell Subsets Producing Granzyme B in the Immune Response to Leishmania major Antigens

The nature of effector cells and the potential immunogenicity of Leishmania major excreted/secreted proteins (LmES) were evaluated using peripheral blood mononuclear cells (PBMCs) from healed zoonotic cutaneous leishmaniasis individuals (HZCL) and healthy controls (HC). First, we found that PBMCs from HZCL individuals proliferate and produce high levels of IFN-γ and granzyme B (GrB), used as a marker of activated cytotoxic T cells, in response to the parasite antigens. IFN-γ is produced by CD4+ T cells, but unexpectedly GrB is also produced by CD4+ T cells in response to stimulation with LmES, which were found to be as effective as soluble Leishmania antigens to induce proliferation and cytokine production by PBMCs from immune individuals. To address the question of regulatory T cell (Tregs) involvement, the frequency of circulating Tregs was assessed and found to be higher in HZCL individuals compared to that of HC. Furthermore, both CD4+CD25+ and CD4+CD25− T cells, purified from HZCL individuals, produced IFN-γ and GrB when stimulated with LmES. Additional experiments showed that CD4+CD25+CD127dim/- Tregs were involved in GrB production. Collectively, our data indicate that LmES are immunogenic in humans and emphasize the involvement of CD4+ T cells including activated and regulatory T cells in the immune response against parasite antigens

A murine model of meningeal inflammation and subpial demyelination identifies an anti-MOG independent mechanism of cortical injury that is inhibited by Siponimod therapy

Subpial demyelination is a specific hallmark of multiple sclerosis (MS) and a correlate of disease progression and cognitive decline. Although the mechanism(s) that mediate pathogenesis in this compartment remain unclear, it has been speculated that inflammation in the overlying meninges may be associated with sub-pial injury. We have previously shown that proteolipid-primed Th17 cells adoptively transferred into SJL/J recipient mice induce Experimental Autoimmune Encephalomyelitis (A/T SJL/J EAE) accompanied by extensive stromal cell remodelling and accumulation of lymphocytes in the brain meninges. Here we show that meningeal inflammation in this model overlays areas of subpial cortical demyelination associated with microglial/macrophage activation, disruption of the glial limitans and evidence of an oxidative stress response. These pathological features were observed even in the absence of measurable anti-MOG IgM or IgG antibodies. We took advantage of this model to test potential mechanisms of action of BAF312 (siponimod), a selective sphingosine 1-phosphate (S1P) receptor1,5 modulator. BAF312 treatment significantly ameliorated clinical manifestations of EAE concomitant with diminished meningeal inflammation and subpial pathology and as well as a selective reduction in Th17 cell accumulation in the central nervous system (CNS). We conclude that Th17 cells rather than anti-MOG antibodies are critically required for meningeal inflammation and cortical pathology in A/T SJL/J EAE. Moreover BAF312, a promising MS therapeutic, ameliorates the clinical and pathological features of this model perhaps through its affect on CNS-resident Th17 cells

Prediction of T Cell Epitopes from Leishmania major Potentially Excreted/Secreted Proteins Inducing Granzyme B Production.

Leishmania-specific cytotoxic T cell response is part of the acquired immune response developed against the parasite and contributes to resistance to reinfection. Herein, we have used an immune-informatic approach for the identification, among Leishmania major potentially excreted/secreted proteins previously described, those generating peptides that could be targeted by the cytotoxic immune response. Seventy-eight nonameric peptides that are predicted to be loaded by HLA-A*0201 molecule were generated and their binding capacity to HLA-A2 was evaluated. These peptides were grouped into 20 pools and their immunogenicity was evaluated by in vitro stimulation of peripheral blood mononuclear cells from HLA-A2+-immune individuals with a history of zoonotic cutaneous leishmaniasis. Six peptides were identified according to their ability to elicit production of granzyme B. Furthermore, among these peptides 3 showed highest affinity to HLA-A*0201, one derived from an elongation factor 1-alpha and two from an unknown protein. These proteins could constitute potential vaccine candidates against leishmaniasis

Psycho-social impacts, experiences and perspectives of patients with Cutaneous Leishmaniasis regarding treatment options and case management: an exploratory qualitative study in Tunisia

Although non-fatal and mostly self-healing in the case of Leishmania (L.) major, cutaneous leishmaniasis (CL) is mainly treated to reduce lesion healing time. Less attention is paid to the improvement of scars, especially in aesthetically relevant areas of the body, which can dramatically affect patients' wellbeing. We explored patients' perspectives about treatment options and the social and psychological burden of disease (lesion and scar). Individual in-depth interviews were conducted with ten confirmed CL patients at two L. major endemic sites in Southern Tunisia (Sidi Bouzid and Gafsa). Participants were selected using a sampling approach along a spectrum covering e.g. age, sex, and clinical presentation. Patients' experiences, opinions and preferences were explored, and their detailed accounts gave an insight on the impact of CL on their everyday lives. The impact of CL was found to be considerable. Most patients were not satisfied with treatment performance and case management. They expected a shorter healing time and better accessibility of the health system. Tolerance of the burden of disease was variable and ranged from acceptance of hidden scars to suicidal thoughts resulting from the fear to become handicapped, and the stress caused by close relatives. Some believed CL to be a form of skin cancer. Unexpectedly, this finding shows the big gap between the perspectives of patients and assumptions of health professionals regarding this disease. This study provided valuable information for better case management emphasizing the importance of improving communication with patients, and accessibility to treatment. It generated context-specific knowledge to policy makers in Tunisia to implement effective case management in a country where access to treatment remains a challenge due to socio-economic and geographic barriers despite a long tradition in CL control.</p

IFN-γ levels induced by <i>P</i>. <i>papatasi</i> salivary glands extracts stimulation in individuals living in old or emerging foci of <i>L</i>. <i>major</i> infection.

<p>IFN-γ was quantified by ELISA, in the culture supernatants of PBMC stimulated with <i>P</i>. <i>papatasi</i> salivary gland extracts (1 gland/ml) during 72h. Analysis of IFN-γ production was performed in individuals from OF and EF (a), LST+/Scar+ (healed), LST+/Scar- (asymptomatics) and LST-/Scar- (naïve) groups (b) and LST+, LST- groups (c), in each focus. Statistical significance was assigned to a value of p<0,05. Statistically significant differences between stimulated and non-stimulated cultures and between groups are showed. Horizontal lines represent median IFN-γ values.</p

Clinical and immunological parameters in individuals living in old (OF) or emerging foci (EF) of <i>L</i>. <i>major</i> infection.

<p>Clinical and immunological parameters in individuals living in old (OF) or emerging foci (EF) of <i>L</i>. <i>major</i> infection.</p