Distinct Immune Profiles of Exhausted Effector and Memory CD8+ T Cells in Individuals With Filarial Lymphedema

CD8+ T cells are crucial for the clearance of viral infections, and current research begins to highlight their importance in parasitic diseases too. In-depth research about characteristics of CD8+ T-cell subsets and exhaustion remains uncertain, especially during filariasis, a chronic helminth infection. Lymphatic filariasis, elicited by Wuchereria bancrofti, remains a serious health problem in endemic areas in Ghana, especially in those suffering from morbidity due to lymphedema (LE). In this observational study, the characteristics and profiles of CD8+ T cells were compared between asymptomatic Wuchereria bancrofti-infected individuals, uninfected endemic normals, and those with LE (grades 2–6). Focusing on exhausted memory (CD8+exmem: CD8+ T-betdimEomeshi) and effector (CD8+exeff: CD8+T-bethiEomesdim) CD8+ T-cell subsets, advanced flow cytometry revealed that LE individuals presented reduced frequencies of IFN-γ+CD8+exmem T cells expressing Tim-3 or LAG-3 which negatively correlated to the presence of LE. Moreover, the LE cohort further showed significantly higher frequencies of IL-10+CD8+exeff T cells expressing either Tim-3, LAG-3, CD39, KLRG-1, or PD-1, all associated markers of exhaustion, and that these frequencies positively correlated with the presence of LE. In summary, this study shows that distinct exhausted CD8+ T-cell subsets are prominent in individuals suffering from LE, suggesting that enhanced inflammation and constant immune activation might drive exhaustion of CD8+ T cells. Since T-cell exhaustion is known to be associated with insufficient control of persisting antigen, the data presented here reveals that these CD8+ T-cell exhaustion patterns in filarial LE should be taken into consideration for prevention and control management of LE

Multivariable regression analysis in Schistosoma mansoni-infected individuals in the Sudan reveals unique immunoepidemiological profiles in uninfected, egg+ and non-egg+ infected individuals

Background: In the Sudan, Schistosoma mansoni infections are a major cause of morbidity in schoolaged children and infection rates are associated with available clean water sources. During infection, immune responses pass through a Th1 followed by Th2 and Treg phases and patterns can relate to different stages of infection or immunity. Methodology: This retrospective study evaluated immunoepidemiological aspects in 234 individuals(range 4–85 years old) from Kassala and Khartoum states in 2011. Systemic immune profiles(cytokines and immunoglobulins) and epidemiological parameters were surveyed in n = 110 persons presenting patent S. mansoni infections (egg+), n = 63 individuals positive for S. mansoni via PCR in sera but egg negative (SmPCR+) and n = 61 people who were infection-free (Sm uninf). Immunoepidemiological findings were further investigated using two binary multivariable regression analysis. Principal Findings: Nearly all egg+ individuals had no access to latrines and over 90% obtained water via the canal stemming from the Atbara River. With regards to age, infection and an egg+ status was linked to young and adolescent groups. In terms of immunology, S. mansoni infection per se was strongly associated with increased SEA-specific IgG4 but not IgE levels. IL-6, IL-13 and IL-10 were significantly elevated in patently-infected individuals and positively correlated with egg load. In contrast, IL-2 and IL-1β were significantly lower in SmPCR+ individuals when compared to Sm uninf and egg+ groups which was further confirmed during multivariate regression analysis. Conclusions/Significance: Schistosomiasis remains an important public health problem in the Sudan with a high number of patent individuals. In addition, SmPCR diagnostics revealed another cohort of infected individuals with a unique immunological profile and provides an avenue for future studies on non-patent infection states. Future studies should investigate the downstream signalling pathways/mechanisms of IL-2 and IL-1β as potential diagnostic markers in order to distinguish patent from non-patent individuals

Development of patent Litomosoides sigmodontis infections in semi-susceptible C57BL/6 mice in the absence of adaptive immune responses

Abstract Background One of the most advantageous research aspects of the murine model of filariasis, Litomosoides sigmodontis, is the availability of mouse strains with varying susceptibility to the nematode infection. In C57BL/6 mice, L. sigmodontis worms are largely eliminated in this strain by day 40 post-infection and never produce their offspring, microfilariae (Mf). This provides a unique opportunity to decipher potential immune pathways that are required by filariae to achieve a successful infection. In this study we tracked worm development and patency, the production of microfilariae and thus the transmission life-stage, in Rag2IL-2Rγ−/− mice which are deficient in T, B and NK cell populations. Findings Although worm burden was comparable between wildtype (WT) and Rag2IL-2Rγ−/− mice on d30, by day 72 post-infection, parasites in Rag2IL-2Rγ−/− mice were still in abundance, freely motile and all mice presented high quantities of Mf both at the site of infection, the thoracic cavity (TC), and in peripheral blood. Levels of cytokine (IL-4, IL-6, TNFα) and chemokine (MIP-2, RANTES, Eotaxin) parameters were generally low in the TC of infected Rag2IL-2Rγ−/−mice at both time-points. The frequency of neutrophils however was higher in Rag2IL-2Rγ−/−mice whereas eosinophils and macrophage populations, including alternatively activated macrophages, were elevated in WT controls. Conclusion Our data highlight that adaptive immune responses prevent the development of patent L. sigmodontis infections in semi-susceptible C57BL/6 mice and suggest that induction of such responses may offer a strategy to prevent transmission of human filariasis

Summary of binary multivariable regression analysis between the different patient groups: Relation of the covariates age, exposure and individual cytokines or Igs.

<p>Summary of binary multivariable regression analysis between the different patient groups: Relation of the covariates age, exposure and individual cytokines or Igs.</p

Higher levels of SEA-specific IgG4 but not IgE production in infected individuals.

<p>Serum from all three groups was analyzed for the concentration of total IgE (A) and the optical density of SEA-specific IgG4 (C) and IgE (E) using ELISA. (F) depicts the ratio of antigen-specific IgG4/IgE. Graphs show box whiskers with median, interquartile ranges and outliers. Statistical significances between the indicated groups were obtained after Kruskal-Wallis and Mann-Whitney-U tests. Levels of total IgE and SEA-specific IgG4 immunoglobulins were further correlated with egg load (B and D respectively) and tested for statistical significance using the Spearman correlation test.</p

Systemic levels of IL-10 or IL-9 showed opposing profiles in patently infected individuals.

<p>Serum from all three groups was analyzed for the production of IL-9 (A) and IL-10 (C) using FlowCytomix technology. Graphs show box whiskers with median, interquartile ranges and outliers. Statistical significances between the indicated groups were obtained after Kruskal-Wallis and Mann-Whitney-U tests. Levels of IL-9 (B) and IL-10 (D) were correlated with the number of eggs and tested for statistical significance using the Spearman correlation test.</p

Systemic IL-13 is elevated in patently-infected <i>S. mansoni</i> individuals.

<p>Serum from participants (n = 234) was analyzed for the production of IFN-γ (A), IL-2 (B), IL-4 (C), IL-5 (D) and IL-13 (E) using FlowCytomix technology. Graphs show box whiskers with median, interquartile ranges and outliers. Statistical significances between the indicated groups were obtained after Kruskal-Wallis and Mann-Whitney-U tests. IL-13 levels were correlated with the number of eggs (F) and tested for statistical significance using the Spearman correlation test.</p

Lower levels of systemic IL-1β in SmPCR⁺ individuals.

<p>Individual serum samples from all three groups were analyzed for the production of IL-12p70 (A), TNF-α (B), IL-8 (C) and IL-1β (D) using FlowCytomix technology or ELISA (IL-8). Graphs show box whiskers with median, interquartile ranges and outliers. Statistical significances between the indicated groups were obtained after Kruskal-Wallis and Mann-Whitney-U tests. IL-1β levels were correlated with the number of eggs (E) and tested for statistical significance using the Spearman correlation test.</p

Map of study area.

<p>Schematic representation of the regions of Kassala and Khartoum states in the Sudan. Red circles denote villages in which study participants resided.</p

Characteristics of study population.

<p>Characteristics of study population.</p