Characterization of memory T cells in individuals resistant to Schistosoma mansoni infection

Schistosomiasis affects about 240 million people worldwide and is estimated that about 700 million people live in areas at risk of infection. In the context of immune response associated with infection by Schistosoma mansoni, the role of memory T cells is not well understood.

AIM

To evaluate the frequency of memory CD4⁺ and CD8⁺ T cells from individuals resistant and susceptible to Schistosoma mansoni infection.

METHODS AND RESULTS

We selected individuals with low (resistant) and high (susceptible) parasite burden using databases generated during previous studies carried out in the same endemic area. The cell surface markers were performed using flow cytometry. In this study, the resistant individuals showed an increase in the CD4⁺ memory T-cell pool associated with an increase in the central memory cell (TCM) and a decrease in the effector memory cell (T_EM ). Individuals susceptible to infection had higher frequencies of effector memory cells compared to resistant individuals.

CONCLUSIONS

These data suggest that resistance to S mansoni infection may be associated with an increase in the number of CD4⁺ memory T cells and susceptibility to infection is associated with a decrease in the central memory cell as well as high proportions of effector memory cells.

Schistosoma antigens downmodulate the in vitro inflammatory response in individuals infected with human T cell lymphotropic virus type 1

Human T cell lymphotropic virus type 1 (HTLV-1) is the causal agent of HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP). While the immune response to HTLV-1 infection is polarized to the Th1-type, chronic helminth infections drive the Th2- and T regulatory-type, and are able to downregulate the inflammatory response in some autoimmune diseases.

OBJECTIVE

To evaluate whether Schistosoma spp. antigens alter the in vitro cytokine response in HTLV-1 infection.

METHODS

The recombinant Schistosoma antigens Sm29 and ShTSP2 (tetraspanin) and PIII, a fraction of the Schistosoma mansoni adult worm antigen were added to peripheral blood mononuclear cell (PBMC) cultures of HTLV-1-infected individuals and the levels of interferon (IFN)-γ and interleukin (IL)-10 in the supernatants were measured using the ELISA sandwich technique.

RESULTS

Compared to the levels of cytokine in nonstimulated cultures, the levels of IFN-γ were reduced in 50, 47 and 50% of patients by the presence of Sm29, ShTsp2 and PIII, respectively. The downregulation of IFN-γ production in the presence of Sm29 antigen was observed mainly in subjects who had lower basal levels of this cytokine. The levels of IL-10, however, increased by the addition of the three antigens in the cultures in 74, 62 and 44% of individuals, respectively. In addition, there was a decrease in the ratio of IFN-γ/IL-10 levels in cultures stimulated with Sm29 and ShTSP2 when compared to nonstimulated ones.

CONCLUSIONS

The Schistosoma spp. antigens used in this study were able to downmodulate IFN-γ production in vitro in HTLV-1 infection. This may be associated with the increased levels of IL-10 induced by the antigens.

Factors associated with resistance to Schistosoma mansoni infection in an endemic area of Bahia, Brazil

Detailed knowledge of factors associated with resistance to Schistosoma mansoni infection in endemic areas might facilitate more effective schistosomiasis control. We conducted a cross-sectional study of persons resistant to schistosomiasis and found no association between socioeconomic status and resistance to infection. Mononuclear cells of resistant subjects produced higher levels of interleukin-5 (IL-5), IL-13 and interferon-γ upon stimulation with soluble egg antigen (SEA) compared with infected persons. When stimulated with Sm21.6 or Sm22.6, levels of IL-10 were higher in cell culture of resistant persons. Levels of IgE against soluble adult worm antigen (SWAP) and against interleukin-4-inducing principle from S. mansoni eggs (IPSE) and levels of IgG4 against SWAP, SEA, and Sm22.6 were lower in the resistant group compared with the susceptible group. Our data suggest that socioeconomic status could not fully explain resistance to S. mansoni infection observed in the studied area. However, a mixture of Th1 and Th2 immune responses and low levels of specific IgG4 against parasite antigens could be mediating resistance to infection.

[Controversies in the association between type 1 diabetes and asthma]

OBJECTIVE

Critical review of the literature to investigate the relationship between asthma and type 1 diabetes mellitus (DM1).

SOURCE OF DATA

Bibliography search in MEDLINE and LILACS databases in the last twenty years.

SUMMARY OF DATA

Several studies demonstrate an inverse relationship between asthma, atopic diseases and the risk to develop DM1. According to the "Hygiene Hypothesis", the risk of allergic diseases decreases with infections early in childhood, towards distance of Th2 profile, common at birth, to the Th1 phenotype. Other articles described lack of association or positive association between DM1 and allergies. There is a possibility of environmental factors interfering in the development of disorders mediated by Th1 and Th2 cells, in the same individual, due to the absence of immunomodulatory mechanisms mediated by interleukin-10 and regulatory cells.

CONCLUSION

The existing information about the inverse association between Th1-mediated diseases (e.g., DM1), and those that are Th2-mediated (e.g., allergies) are conflicting requiring more investigation to explain this question.

Schistosoma mansoni antigen-driven interleukin-10 production in infected asthmatic individuals

Asthmatics infected with Schistosoma mansoni have a less severe course of asthma and an inhibition of the Th2 inflammatory response that seems to be mediated by interleukin (IL-10). The objective of this study was to evaluate the capacity of some S. mansoni antigens to stimulate IL-10 production in vitro by cells of asthmatic infected individuals. Peripheral bloods mononuclear cells were stimulated with the S. mansoni recombinant antigens Sm22.6, Sm14, P24, and PIII antigen. IL-10 was measured in the supernatants of cultures. As the recombinant antigens were cloned in Escherichia coli, we blocked contaminant endotoxin with polymyxin B added to the cultures. We demonstrated that all antigens used drove high production of IL-10 in S. mansoni infected individuals (n = 13, 408 +/- 514 and 401 +/- 383 pg/ml, 484 +/- 245 pg/ml, 579 +/- 468 pg/ml, respectively). In asthmatics infected with S. mansoni (n = 21) rP24 induced higher levels of IL-10 (565 +/- 377 pg/ml) when compared to PIII, rSm14 and rSm22.6 (184 +/- 209 pg/ml; 292 +/- 243 pg/ml; 156 +/- 247 pg/ml, respectively).

CONCLUSION

the S. mansoni antigens evaluated in this study stimulated IL-10 production by cells from infected individuals and therefore they have the potential to be used as a modulator of the inflammatory response in asthma.

Aluminum hydroxide associated to Schistosoma mansoni 22.6 kDa protein abrogates partial protection against experimental infection but not alter interleukin-10 production

The need to develop a vaccine against schistosomiasis led several researches and our group to investigate proteins from Schistosoma mansoni as vaccine candidates. Sm22.6 is a protein from S. mansoni that shows high identity with Sj22.6 and Sh22.6 (79 and 91%, respectively). These proteins are associated with high levels of IgE and protection to reinfection. Previously, we have shown that Sm22.6 induced a partial protection of 34.5% when used together with Freund's adjuvant and produced a Th0 type of immune response with interferon-g and interleukin-4. In this work, mice were immunized with Sm22.6 alone or with aluminum hydroxide adjuvant and high levels of IgG, IgG1, and IgG2a were measured. Unfortunately, no protection was detected. Since IL-10 is a modulating cytokine in schistosomiasis, we also observed a high level of this molecule in splenocytes of vaccinated mice. In conclusion, we did not observe the adjuvant effect of aluminum hydroxide associated with rSm22.6 in protective immunity.

Worms and allergy

Worms and asthma are associated with a type 2 immune response, but evidence has accumulated that helminth infection is negatively associated with atopy, prevalence of allergic diseases and severity of asthma. One important difference between these polarized type 2 responses is that in allergy modulation of the immunological response is not appropriate, whereas in infection with helminths, several host mechanisms down-regulate the host immune response. As a result, patients infected with worms have a decrease in both type 1 and type 2 responses. The main mechanism involved in this down-modulation is increased production of IL-10, but expansion of regulatory T cells and NKT cells may also participate. Regarding the interaction between worms and allergy, a few variables need to be taken in account: phase (acute or chronic) of helminth infection, parasite load and species of helminth. In animals and humans, acute helminth infection may increase manifestations of allergy, whereas chronic infection with parasites decreases atopy. The modulation of the immune response by helminths is dependent on having an adequate parasite load. Moreover, although several helminth species have been shown to modulate immune responses, most in vitro and in vivo studies have focused on the importance of Schistosoma mansoni in down-modulating allergic reactions.

Skin test reactivity and Der p-induced interleukin 10 production in patients with asthma or rhinitis infected with Ascaris

BACKGROUND

Helminth infections have been associated with reduced reactivity to aeroallergens, which could be related to interleukin 10 (IL-10) production, as reported in schistosomiasis.

OBJECTIVE

To compare skin responses to aeroallergens with Der p specific IL-10 production in patients with asthma or rhinitis according to Ascaris infection status.

METHODS

Cross-sectional study of 113 patients with asthma or rhinitis from a region endemic for geohelminths. Stool examinations and skin prick tests to aeroallergens were performed in all the patients. Der p specific IL-10 production was measured in the supernatant of peripheral blood mononuclear cell (PBMC) cultures of a subsample of 53 patients.

RESULTS

Forty-seven patients had Ascaris in their stool samples. Skin test results were positive in 77% of Ascaris-infected patients and in 71% of uninfected individuals. Median levels of Der p specific IL- 10 in PBMC cultures of infected and uninfected patients were similar (7.8 and 8.4 pg/mL, respectively). The lack of association remained when parasite load was taken into account and when patients with evidence of previous infection were removed from the uninfected group.

CONCLUSIONS

In patients with asthma or rhinitis living in an urban area endemic for geohelminths, we found no association between Ascaris infection and skin reactivity to aeroallergens. Furthermore, there was no difference in Der p specific IL-10 production by PBMCs. These negative findings indicate that different from what is observed in Schistosoma infection, Ascaris lumbricoides infection in individuals living in an urban area does not induce strong regulatory responses.

Schistosoma mansoni infection modulates the immune response against allergic and auto-immune diseases

Chronic Schistosoma mansoni infection leads to a type 2-immune response with increased production of interleukin (IL-10). Evidence indicates chronic exposure to S. mansoni down regulates the type 1 immune response and prevents the onset of Th1-mediated diseases such as multiple sclerosis, diabetes mellitus and Crohn's disease. Furthermore, our own studies have revealed that chronic exposure to S. mansoni also down regulates atopic disease, Th2-mediated diseases. Our studies show an inverse association between the skin prick test reactivity and infection with S. mansoni and show the severity of asthma is reduced in subjects living in an endemic area of S. mansoni. Moreover, we hypothesize the mechanisms involved in the modulation of inflammatory response in atopic individuals, is likely dependent on IL-10 production, an anti-inflammatory cytokine elevated during helminth infections. Patients with asthma and helminth infections produced less IL-5 than patients with asthma without helminth infections, and this down regulation could, in part, be mediated by IL-10. In conclusion, helminthic infections, through induction of regulatory mechanisms, such as IL-10 production, are able to modulate the inflammatory immune response involved in the pathology of auto-immune and allergic disease.

Cytokine profile associated with human chronic schistosomiasis mansoni

This study objective was to evaluate the cytokines associated with early events of hepatic fibrosis in schistosomiasis mansoni. Hepatic fibrosis was classified by ultrasonography in 94 patients. Immunological evaluation was performed by measurement of secreted cytokines (interleukin IL-5, IL-10, IL-13, interferon-gamma, tumor necrosis factor-alpha and transforming growth factors-beta) in peripherl blood mononuclear cells stimulated by Schistosoma mansoni antigens. Significantly, higher levels of IL-5, IL-10 and IL-13 were found in supernatants of SEA-stimulated PBMC from subjects with degree III hepatic fibrosis as compared to patients with degree I or II fibrosis, Significant increases in IL-5 and IL-13 levels were also observed in some of the subjects who remained untreated for one year following initial assessment and developed more serious fibrosis during this period. The data suggests a role for type 2 cytokines in early stages of hepatic fibrosis in human schistosomiasis mansoni.

Association of type 2 cytokines with hepatic fibrosis in human Schistosoma mansoni infection

The objective of this study was to evaluate the role of cytokines in hepatic fibrosis in the prehepatosplenic and early hepatosplenic stages of schistosomiasis mansoni. Hepatic fibrosis was classified by ultrasonography of 94 patients. Immunological evaluation was performed by the measurement of secreted cytokines (interleukin-5 [IL-5], IL-10, IL-13, gamma interferon, tumor necrosis factor alpha, and transforming growth factor beta) in peripheral blood mononuclear cells (PBMC) stimulated by Schistosoma mansoni antigens. Significantly, higher levels of IL-5, IL-10, and IL-13 were found in supernatants of soluble egg antigen-stimulated PBMC from subjects with degree III hepatic fibrosis compared to patients with degree I or II fibrosis. Significant increases in IL-5 and IL-13 levels were also observed in some of the subjects who remained untreated for 1 year following initial assessment and developed more serious fibrosis during this period. The data suggest a role for type 2 cytokines in hepatic fibrosis in human schistosomiasis mansoni.

IgG anti-IgE autoantibodies in visceral leishmaniasis

Procedures for IgG depletion in visceral leishmaniasis (VL) and schistosomiasis sera using Sepharose-protein G beads also deplete IgE. In this study, the presence of IgG anti-IgE autoantibodies in sera from patients with VL (n = 10), and hepatic-intestinal schistosomiasis (n = 10) and from healthy individuals (n = 10) was investigated. A sandwich ELISA using goat IgG anti-human IgE to capture serum IgE and goat anti-human IgG peroxidase conjugate to demonstrate the binding of IgG to the IgE captured was performed. VL sera had higher titers (p < 0.05) of IgG anti-IgE autoantibodies (OD = 2.01 +/- 0.43) than sera from healthy individuals (OD = 1.35 +/- 0.16) or persons infected with Schistosoma mansoni (OD = 1.34 +/- 0.18). The immunoblotting carried out with eluates from Sepharose-protein G beads used to deplete IgG from these sera and goat anti-human IgE peroxidase conjugate, showed a similar pattern of bands, predominating the 75 kDa epsilon-heavy chain and also polypeptides resulting from physiological enzymatic digestion of IgE. A frequent additional band immediately above 75 kDa was observed only in VL sera.

[Evaluation of the sensitization power of Montenegro skin test]

The Montenegro skin test, used to diagnose cutaneous leishmaniasis, is now being considered to detect immunogenicity after vaccination. In this study, we evaluated the ability of this test to induce immune response and IFN-g production in subjects not previously exposed to Leishmania. The Montenegro skin test was performed using antigens of L. amazonensis produced by our laboratory (group I) or by FIOCRU-RJ (group II). At day 30, 33% of the subjects from group I and 42% from group II were positive, compared to 67% from group I and 50% from group II at day 90. IFN-y was detected in 56 % of subjects from group I and 17% from group II at day 30 (169+/-309 and 11+/-36pg/ml) and in 67% from group I and 58% from group II by day 360 (69+/-107 and 18+/-20pg/ml). These data demonstrate that the Montenegro skin test induces not only a delayed hypersensitivity reaction, but also IFN-y production.

Detection of specific IgE antibodies in parasite diseases

Activation of Th1 or Th2 cells is associated with production of specific immunoglobulin isotypes, offering the opportunity to use antibody measurement for evaluation of T cell function. Schistosomiasis and visceral leishmaniasis are diseases associated with Th2 activation. However, an IgE response is not always detected in these patients. In the present study we evaluated specific IgE antibodies to S. mansoni and L. chagasi antigens by ELISA after depletion of serum IgG with protein G immobilized on Sepharose beads or RF-absorbent (purified sheep IgG antibodies anti-human IgG). In schistosomiasis patients, specific IgE to SWAP antigen was demonstrable in only 10 of 21 patients (48%) (mean absorbance +/- SD = 0.102 +/- 0.195) when unabsorbed serum was used. Depletion of IgG with protein G increased the number of specific IgE-positive tests to 13 (62%) and the use of RF-absorbent increased the number of positive results to 20 (95%) (mean absorbances +/- SD = 0.303 +/- 0. 455 and 0.374 +/- 0.477, respectively). Specific IgE anti-L. chagasi antibodies were not detected in unabsorbed serum from visceral leishmaniasis patients. When IgG was depleted with protein G, IgE antibodies were detected in only 3 (11%) of 27 patients, and the use of RF-absorbent permitted the detection of this isotype in all 27 visceral leishmaniasis sera tested (mean absorbance +/- SD = 0.104 +/- 0.03). These data show that the presence of IgG antibodies may prevent the detection of a specific IgE response in these parasite diseases. RF-absorbent, a reagent that blocks IgG-binding sites and also removes rheumatoid factor, was more efficient than protein G for the demonstration of specific IgE antibodies.

Evidence of a T helper type 2 activation in human schistosomiasis

The lymphocyte proliferative response and cytokine production to S. mansoni antigen in vitro were evaluated in 22 schistosomiasis patients living in an area endemic for this disease. The majority of patients (86%) showed no lymphocyte proliferative response and none of them showed interferon-gamma (IFN-gamma) production, following in vitro stimulation with soluble adult worm antigen preparation (SWAP). In contrast, interleukin (IL)-5 (2038 +/- 1757 pg/ml) and IL-10 (867 +/- 762 pg/ml) were detected in peripheral blood mononuclear cell (PBMC) cultures stimulated with SWAP. Moreover, mRNA for IL-4 was detected in SWAP-stimulated PBMC from 4 of 6 patients evaluated. Restoration of lymphoproliferative response was achieved in 4 of 6 patients by adding anti-IL-10 monoclonal antibody (mAb) to PBMC cultures [mean stimulation index (SI) in the presence of antigen = 2.7 +/- 2.9; SI in the presence of antigen plus anti-IL-10, 21 +/- 16]. Restoration of IFN-gamma production by addition of anti-IL-10 mAb was achieved in 4 of 12 patients evaluated (248, 350, 687 and 710 pg/ml). Moreover, the addition of IL-10 to PBMC cultures of 3 schistosomiasis patients and 2 cured subjects who had high lymphoproliferative responses to SWAP resulted in the suppression of these responses by 90%, and completely suppressed IFN-gamma production in one of the subjects, whose PBMC produced IFN-gamma after stimulation with SWAP. The presence of IL-4 mRNA, high levels of IL-5, and the absence of IFN-gamma in PBMC culture supernatants from infected patients, supports the conclusion that patients living in an endemic area of schistosomiasis express a predominant T helper type 2 response. The high levels of IL-10 and the ability of neutralizing anti-IL-10 mAb to restore T cell responses indicate that this cytokine plays an important role in the modulation of T cell responses in schistosomiasis.

The absence of gamma-interferon production of S. mansoni antigens in patients with schistosomiasis

No gamma-interferon production was observed in peripheral blood mononuclear cells (PBMC) cultures from 45 patients living in an endemic area of schistosomiasis in Brazil following in vitro stimulation with schistosomula or adult worm antigens from Schistosoma mansoni (4.9 +/- 24 and 1.0 +/- 3.4 pg/ml, respectively). This immunological abnormality was observed in patients both with a high degree of infection (> or = 400 eggs/g feces) and with a low degree of infection (< 400 eggs/g feces), and was independent of the degree of natural exposure to infection. This absence of gamma-interferon production was antigen specific since high levels of this cytokine were detected in the same patients when their cells were stimulated with PPD (247 +/- 179 pg/ml) or PHA (408 +/- 328 pg/ml). In two of four subjects cured of a previous S. mansoni infection and currently living outside the endemic area, gamma-IFN was produced when their PBMC were stimulated with adult worm antigen (75 +/- 2.5 pg/ml).

[Primary disorders of neutrophils: principal clinical and laboratory aspects]

This article presents a review of different categories of inherited neutrophil dysfunctions, such as chronic granulomatous disease, disorders of chemotaxis, defects of degranulation and the leukocyte adherence deficiency. The clinical manifestations and laboratory findings of these phagocyte abnormalities, with particular reference to various tests of neutrophil functions used for diagnostic elucidation are described.