Molecular typing of Strongyloides stercoralis in Latin America, the clinical connection.

This study analysed Strongyloides stercoralis genetic variability based on a 404 bp region of the cox1 gene from Latin-American samples in a clinical context including epidemiological, diagnosis and follow-up variables. A prospective, descriptive, observational study was conducted to evaluate clinical and parasitological evolution after ivermectin treatment of 41 patients infected with S. stercoralis. Reactivation of the disease was defined both by clinical symptoms appearance and/or direct larvae detection 30 days after treatment or later. We described 10 haplotypes organized in two clusters. Most frequent variants were also described in the Asian continent in human (HP24 and HP93) and canine (HP24) samples. Clinical presentation (intestinal, severe, cutaneous and asymptomatic), immunological status and eosinophil count were not associated with specific haplotypes or clusters. Nevertheless, presence of cluster 1 haplotypes during diagnosis increased the risk of reactivation with an odds ratio (OR) of 7.51 [confidence interval (CI) 95% 1.38­44.29, P = 0.026]. In contrast, reactivation probability was 83 times lower if cluster 2 (I152V mutation) was detected (OR = 0.17, CI 95% 0.02­0.80, P = 0.02). This is the first analysis of S. stercoralis cox1 diversity in the clinical context. Determination of clusters during the diagnosis could facilitate and improve the design of follow-up strategies to prevent severe reactivations of this chronic disease.

IL-10 participates in the expansion and functional activation of CD8+ T cells during acute infection with Trypanosoma cruzi.

IL-10 is a pleiotropic cytokine with immunoregulatory functions affecting various cell types. In a model of experimental infection with the protozoan Trypanosoma cruzi (T. cruzi), we found increased morbidity and lower parasite control in IL-10 deficient mice (IL-10 KO) compared to wild-type (WT) mice. Despite enhanced Mϕ function and dendritic cell activation, IL-10 KO mice were more susceptible to infection. The kinetics of T cells in spleen and peripheral blood revealed that infected IL-10 KO mice failed to increase the number of spleen and circulating total CD8+ T cells, a phenomenon observed from the second week of infection in WT mice. Total CD8+ T cells from IL-10 KO mice exhibited diminished proliferation, cytotoxic potential and IFN-γ production than their WT counterparts and T. cruzi-specific CD8+ T cells displayed reduced in vivo cytotoxicity. The absence of IL-10 selectively affected expansion, survival, and increased PD-1 expression of CD8+ T cells without altering these same parameters on CD4+ T cells. Increased inhibitory receptors expression and down-modulation of T-bet by CD8+ T cells from IL-10 KO infected mice were compatible with a T cell exhaustion phenotype. Collectively, these findings reveal that during acute infection, IL-10 plays a previously unrecognized stimulatory role on CD8+ T cells, the most relevant lymphocyte population for the control of intracellular T. cruzi stages. A clear knowledge of the underlying mechanisms that drive effector functions of cytotoxic T cells is critical to understand pathogen persistence and rational design of prophylactic strategies against T. cruzi.

Strongyloidiasis Outside Endemic Areas: Long-term Parasitological and Clinical Follow-up After Ivermectin Treatment.

Background: Strongyloides stercoralis affects 30-100 million people worldwide. The first-line therapy is ivermectin. Cure is defined as the absence of larvae by parasitological methods 1 year after treatment. To date, no longitudinal parasitological studies for longer periods of time have been conducted to confirm its cure. Here, we evaluated treatment response in long-term follow-up patients with chronic infection using parasitological and molecular methods for larvae or DNA detection. Methods: A prospective, descriptive, observational study was conducted between January 2009 and September 2015 in Buenos Aires, Argentina. Twenty-one patients with S. stercoralis diagnosis were evaluated 30, 60, and 90 days as well as 1, 2, 3, and/or 4 years after treatment by conventional methods (fresh stool, Ritchie method, agar plate culture), S. stercoralis-specific polymerase chain reaction (PCR) in stool DNA, and eosinophil values. Results: During follow-up, larvae were detected by conventional methods in 14 of 21 patients. This parasitological reactivation was observed starting 30 days posttreatment (dpt) and then at different times since 90 dpt. Eosinophil values decreased (P = .001) 30 days after treatment, but their levels were neither associated with nor predicted these reactivations. However, S. stercoralis DNA was detected by PCR in all patients, both in their first and subsequent stool samples, thus reflecting the poor efficacy of ivermectin at eradicating parasite from host tissues. Asymptomatic eosinophilia was the most frequent clinical form among chronically infected patients. Conclusions: These results suggest that the parasitological cure is unlikely. Strongyloidiasis must be considered a chronic infection and ivermectin administration schedules should be reevaluated.

Trypanosoma cruzi Infection Imparts a Regulatory Program in Dendritic Cells and T Cells via Galectin-1-Dependent Mechanisms.

Galectin-1 (Gal-1), an endogenous glycan-binding protein, is widely distributed at sites of inflammation and microbial invasion. Despite considerable progress regarding the immunoregulatory activity of this lectin, the role of endogenous Gal-1 during acute parasite infections is uncertain. In this study, we show that Gal-1 functions as a negative regulator to limit host-protective immunity following intradermal infection with Trypanosoma cruzi. Concomitant with the upregulation of immune inhibitory mediators, including IL-10, TGF-ß1, IDO, and programmed death ligand 2, T. cruzi infection induced an early increase of Gal-1 expression in vivo. Compared to their wild-type (WT) counterpart, Gal-1-deficient (Lgals1(-/-)) mice exhibited reduced mortality and lower parasite load in muscle tissue. Resistance of Lgals1(-/-) mice to T. cruzi infection was associated with a failure in the activation of Gal-1-driven tolerogenic circuits, otherwise orchestrated by WT dendritic cells, leading to secondary dysfunction in the induction of CD4(+)CD25(+)Foxp3(+) regulatory T cells. This effect was accompanied by an increased number of CD8(+) T cells and higher frequency of IFN-γ-producing CD4(+) T cells in muscle tissues and draining lymph nodes as well as reduced parasite burden in heart and hindlimb skeletal muscle. Moreover, dendritic cells lacking Gal-1 interrupted the Gal-1-mediated tolerogenic circuit and reinforced T cell-dependent anti-parasite immunity when adoptively transferred into WT mice. Thus, endogenous Gal-1 may influence T. cruzi infection by fueling tolerogenic circuits that hinder anti-parasite immunity.

Impairment in natural killer cells editing of immature dendritic cells by infection with a virulent Trypanosoma cruzi population.

Early interactions between natural killer (NK) and dendritic cells (DC) shape the immune response at the frontier of innate and adaptive immunity. Activated NK cells participate in maturation or deletion of DCs that remain immature. We previously demonstrated that infection with a high virulence (HV) population of the protozoan parasite Trypanosoma cruzi downmodulates DC maturation and T-cell activation capacity. Here, we evaluated the role of NK cells in regulating the maturation level of DCs. Shortly after infection with HV T. cruzi, DCs in poor maturation status begin to accumulate in mouse spleen. Although infection induces NK cell cytotoxicity and cytokine production, NK cells from mice infected with HV T. cruzi exhibit reduced ability to lyse and fail to induce maturation of bone marrow-derived immature DCs (iDCs). NK-mediated lysis of iDCs is restored by in vitro blockade of the IL-10 receptor during NK-DC interaction or when NK cells are obtained from T. cruzi-infected IL-10 knockout mice. These results suggest that infection with a virulent T. cruzi strain alters NK cell-mediated regulation of the adaptive immune response induced by DCs. This regulatory circuit where IL-10 appears to participate might lead to parasite persistence but can also limit the induction of a vigorous tissue-damaging T-cell response.

Trypanosoma cruzi induces regulatory dendritic cells in vitro.

A main feature of acute infection with Trypanosoma cruzi is the presence of immunological disorders. A previous study demonstrated that acute infection with the virulent RA strain downregulates the expression of major histocompatibility complex class II (MHC-II) on antigen-presenting cells and impairs the T-cell stimulatory capacity of splenic dendritic cells (DC). In the present work, we assessed the ability of trypomastigotes (Tp) to modulate the differentiation stage and functionality of bone marrow-derived DC in vitro. We observed that the Tp stage of T. cruzi failed to activate DC, which preserved their low expression of MHC-II and costimulatory molecules, as well as their endocytic activity. We also show that Tp induced transforming growth factor beta (TGF-beta) secretion by DC and enhanced the gap between interleukin-10 (IL-10) and IL-12p70 production, showing a higher IL-10/IL-12p70 ratio upon lipopolysaccharide (LPS) treatment. In addition, we observed that Tp prevented DC full activation induced by LPS, thereby downregulating their MHC-II surface expression and inhibiting their capacity to stimulate lymphocyte proliferation. In vitro IL-10 neutralization during the differentiation process of DC with Tp+LPS showed a reversion of their inhibitory effect during mixed lymphocyte reaction. In contrast, only simultaneous neutralization of IL-10 and TGF-beta, after DC differentiation, was involved in the partial restitution of lymphocyte proliferation. Since both TGF-beta and IL-10 are immunosuppressive cytokines essential in the modulation of the immune response and important in the induction of tolerance, our results suggest for the first time that Tp are responsible for the generation of regulatory DC in vitro.