Erliyani Sartono

T-cell activation and the balance of antibody isotypes in human lymphatic filariasis

Human filarial infection presents a spectrum of clinical states with two major poles: asymptomatic microfilaraemia and amicrofilaraemic chronic disease. Microfilaremia is associated with a Th1-type tolerance, and maximal IgG4 antibodies, while elephantiasis patients react across a broad range of immune parameters. In this review, Rick Maizels and his colleagues discuss recent advances in the immunology of human filariasis and present a summary of their latest studies in an endemic area of Indonesia.

Regulatory T cells in human geohelminth infection suppress immune responses to BCG and Plasmodium falciparum

Chronic helminth infections induce T‐cell hyporesponsiveness, which may affect immune responses to other pathogens or to vaccines. This study investigates the influence of Treg activity on proliferation and cytokine responses to BCG and Plasmodium falciparum‐parasitized RBC in Indonesian schoolchildren. Geohelminth‐infected childrens in vitro T‐cell proliferation to either BCG or pRBC was reduced compared to that of uninfected children. Although the frequency of CD4+CD25hiFOXP3+ T cells was similar regardless of infection status, the suppressive activity differed between geohelminth‐infected and geohelminth‐uninfected groups: Ag‐specific proliferative responses increased upon CD4+CD25hi T‐cell depletion in geohelminth‐infected subjects only. In addition, IFN‐γ production in response to both BCG and parasitized RBC was increased after removal of CD4+CD25hi T cells. These data demonstrate that geohelminth‐associated Treg influence immune responses to bystander Ag of mycobacteria and plasmodia. Geohelminth‐induced immune modulation may have important consequences for co‐endemic infections and vaccine trials.

Depression of Antigen-Specific Interleukin-5 and Interferon-γ Responses in Human Lymphatic Filariasis as a Function of Clinical Status and Age

In an area in which brugian filariasis is endemic, when cytokine levels were analyzed as a function of clinical status comparing those who were asymptomatic and amicrofilaremic with those who were microfilaremic, it was found that both interferon (IFN)-gamma and interleukin (IL)-5 were suppressed in microfilariae carriers (P < .01 and P < .001, respectively), but IL-4 was unabated. Age had a significant effect on cytokine production in both groups. In asymptomatic amicrofilaremic subjects, IL-4 production was high in young persons and decreased with age, whereas in microfilaremic subjects, IL-4 increased significantly with age. Conversely, IFN-gamma showed a tendency to increase with age in asymptomatic amicrofilaremic subjects but not in microfilaremic subjects. IL-5 decreased significantly with increasing age in both asymptomatic amicrofilaremic and microfilaremic groups. These results indicate that the length of exposure to and infection with filarial parasites can each exert a substantial effect on the cytokine response profiles of host T cell populations.

Does treatment of intestinal helminth infections influence malaria? Background and methodology of a longitudinal study of clinical, parasitological and immunological parameters in Nangapanda, Flores, Indonesia (ImmunoSPIN Study)

BackgroundGiven that helminth infections are thought to have strong immunomodulatory activity, the question whether helminth infections might affect responses to malaria antigens needs to be addressed. Different cross-sectional studies using diverse methodologies have reported that helminth infections might either exacerbate or reduce the severity of malaria attacks. The same discrepancies have been reported for parasitemia.Methods/DesignTo determine the effect of geohelminth infections and their treatment on malaria infection and disease outcome, as well as on immunological parameters, the area of Nangapanda on Flores Island, Indonesia, where malaria and helminth parasites are co-endemic was selected for a longitudinal study. Here a Double-blind randomized trial will be performed, incorporating repeated treatment with albendazole (400 mg) or placebo at three monthly intervals. Household characteristic data, anthropometry, the presence of intestinal helminth and Plasmodium spp infections, and the incidence of malaria episodes are recorded. In vitro cultures of whole blood, stimulated with a number of antigens, mitogens and toll like receptor ligands provide relevant immunological parameters at baseline and following 1 and 2 years of treatment rounds. The primary outcome of the study is the prevalence of Plasmodium falciparum and P. vivax infection. The secondary outcome will be incidence and severity of malaria episodes detected via both passive and active follow-up. The tertiary outcome is the inflammatory cytokine profile in response to parasite antigens. The project also facilitates the transfer of state of the art methodologies and technologies, molecular diagnosis of parasitic diseases, immunology and epidemiology from Europe to Indonesia.DiscussionThe study will provide data on the effect of helminth infections on malaria. It will also give information on anthelminthic treatment efficacy and effectiveness and could help develop evidence-based policymaking.Trial registrationThis study was approved by The Ethical Committee of Faculty of Medicine, University of Indonesia, ref:194/PT02.FK/Etik/2006 and has been filed by ethics committee of the Leiden University Medical Center. Clinical trial number:ISRCTN83830814. The study is reported in accordance with the CONSORT guidelines for cluster-randomized studies.

Doxycycline Treatment of Brugia malayi-Infected Persons Reduces Microfilaremia and Adverse Reactions after Diethylcarbamazine and Albendazole Treatment

BACKGROUND The efficacy of doxycycline for treating the causal agent of human lymphatic filariasis, Brugia malayi, is unknown. Standard treatment with diethylcarbamazine-albendazole is associated with adverse reactions. We assessed whether doxycycline alone or in combination with diethylcarbamazine-albendazole would lead to sustained amicrofilaremia and reduced incidence of adverse reactions. METHODS A double-blind, randomized, placebo-controlled 6-week field trial of doxycycline treatment (100 mg/day) of 161 persons infected with B. malayi was conducted. Four months after receiving doxycycline (n=119) or placebo (n=42), participants received diethylcarbamazine (6 mg/kg) plus albendazole (400 mg) or a matching placebo. Adverse reactions were assessed 48 and 60 h after administration of diethylcarbamazine-albendazole. Treatment efficacy was evaluated at 2, 4, and 12 months after the initial doxycycline treatment. RESULTS Four months after beginning doxycycline treatment, Wolbachia loads were reduced by 98%. Doxycycline treatment reduced the prevalence of microfilaremia at 2, 4, and 12 months of follow-up (P<.001 for all time points). At the 1-year follow-up, prevalence was reduced by 77% and 87.5% in patients receiving doxycycline alone or doxycycline plus diethylcarbamazine-albendazole, respectively. In contrast, the reduction of microfilaremia in the group receiving placebo doxycycline plus diethylcarbamazine-albendazole was merely 26.7%. Adverse reactions were lowest in the group receiving doxycycline plus placebo diethylcarbamazine-albendazole and highest in the group receiving placebo doxycycline plus diethylcarbamazine-albendazole. The proportion of persons with high fever and severe adverse reactions was significantly reduced in the group treated with doxycycline plus diethylcarbamazine-albendazole. CONCLUSIONS A 6-week course of doxycycline, either alone or in combination with diethylcarbamazine-albendazole, leads to a decrease in microfilaremia and reduces adverse reactions to antifilarial treatment in B. malayi-infected persons.

Polyparasitism and its impact on the immune system.

Parasitic infections are common in many tropical and sub-tropical regions of the world and concomitant infection, polyparasitism, is the rule rather than the exception in such areas. At the immunological level, different parasites induce quite different responses characterised, for example, by protozoa that polarise responses towards Th1, whilst helminths are strong Th2 and regulatory T cell inducers. The question of how the co-existence of such parasites within the same host might influence the immunological responses to each species and, more importantly, whether such interactions affect resistance, susceptibility or clinical outcome, needs to be addressed in well-designed studies of sufficient power. The current paper discusses what we know as well as the gaps in our knowledge of polyparasitism.

Regulatory T Cells in Human Lymphatic Filariasis: Stronger Functional Activity in Microfilaremics

Infection with filarial parasites is associated with T cell hyporesponsiveness, which is thought to be partly mediated by their ability to induce regulatory T cells (Tregs) during human infections. This study investigates the functional capacity of Tregs from different groups of filarial patients to suppress filaria-specific immune responses during human filariasis. Microfilaremic (MF), chronic pathology (CP) and uninfected endemic normal (EN) individuals were selected in an area endemic for Brugia timori in Flores island, Indonesia. PBMC were isolated, CD4CD25hi cells were magnetically depleted and in vitro cytokine production and proliferation in response to B. malayi adult worm antigen (BmA) were determined in total and Treg-depleted PBMC. In MF subjects BmA-specific T and B lymphocyte proliferation as well as IFN-gamma, IL-13 and IL-17 responses were lower compared to EN and CP groups. Depletion of Tregs restored T cell as well as B cell proliferation in MF-positives, while proliferative responses in the other groups were not enhanced. BmA-induced IL-13 production was increased after Treg removal in MF-positives only. Thus, filaria-associated Tregs were demonstrated to be functional in suppressing proliferation and possibly Th2 cytokine responses to BmA. These suppressive effects were only observed in the MF group and not in EN or CP. These findings may be important when considering strategies for filarial treatment and the targeted prevention of filaria-induced lymphedema.

Specific T cell unresponsiveness in human filariasis: diversity in underlying mechanisms

In an attempt to overcome T cell unresponsiveness to filarial antigens, 65 individuals belonging to the three clinical groups of elephantiasis patients, microfilaraemics, and asymptomatic amicrofilaraemics who exhibited unresponsiveness to Brugia malayi adult worm antigen (BmA) were studied. Peripheral blood mononuclear cells were co‐cultured with antigen and one of the following reagents that have been reported to be effective in reconstituting T cell proliferation: interleukin‐2 (IL‐2), interleukin‐7 (IL‐7), anti‐interleukin‐4, anti‐interleukin‐10, anti‐CD2, anti‐CD27, anti‐CD28, indomethacin, phorbol myristate acetate (PMA), or calcium ionophore (A23I87). We were able to overcome antigen‐specific unresponsiveness in only a minority of the individuals studied. Co‐culture with IL‐2, IL‐7, indomethacin and PMA were the only conditions which resulted in enhanced proliferation to BmA in these individuals. In general, unresponsiveness in elephantiasis patients was easier to reverse than in other clinical groups: in 50% of elephantiasis patients, in 12.5% of microfilaraemics and in 20% of asymptomatic amicrofilaraemics. The results indicate that more than one distinct immunological mechanism may account for the antigen‐specific unresponsiveness in individuals exposed to and infected with brugian filariasis.

A Longitudinal Study of BCG Vaccination in Early Childhood: The Development of Innate and Adaptive Immune Responses

BCG vaccine drives a strong T helper 1 cellular immunity which is essential for the protection against mycobacteria, however recent studies suggest that BCG vaccination can have non-specific beneficial effects unrelated to tuberculosis. In the present cohort study the development of cytokine profiles following BCG vaccination was investigated. Immune responses to PPD were assessed before vaccination and at ages of 5 months, 1 year, and 2 years, followed by BCG scar measurement at 4 years of age. BCG was shown to induce both Th1 and Th2 type responses against PPD at about 5 months of age after vaccination, and while Th1 response was sustained, Th2 responses declined over time. However, BCG scar size was strongly correlated with Th2 responses to PPD at 5 months of age. Importantly, we observed no clear effects of BCG vaccination on innate immune responses in terms of early IL-10 or TNF-α production whereas some alterations in general adaptive immune responses to PHA were observed.

The Effect of Three-Monthly Albendazole Treatment on Malarial Parasitemia and Allergy: A Household-Based Cluster-Randomized, Double-Blind, Placebo-Controlled Trial

Background Helminth infections are proposed to have immunomodulatory activities affecting health outcomes either detrimentally or beneficially. We evaluated the effects of albendazole treatment, every three months for 21 months, on STH, malarial parasitemia and allergy. Methods and Findings A household-based cluster-randomized, double-blind, placebo-controlled trial was conducted in an area in Indonesia endemic for STH. Using computer-aided block randomization, 481 households (2022 subjects) and 473 households (1982 subjects) were assigned to receive placebo and albendazole, respectively, every three months. The treatment code was concealed from trial investigators and participants. Malarial parasitemia and malaria-like symptoms were assessed in participants older than four years of age while skin prick test (SPT) to allergens as well as reported symptoms of allergy in children aged 5–15 years. The general impact of treatment on STH prevalence and body mass index (BMI) was evaluated. Primary outcomes were prevalence of malarial parasitemia and SPT to any allergen. Analysis was by intention to treat. At 9 and 21 months post-treatment 80.8% and 80.1% of the study subjects were retained, respectively. The intensive treatment regiment resulted in a reduction in the prevalence of STH by 48% in albendazole and 9% in placebo group. Albendazole treatment led to a transient increase in malarial parasitemia at 6 months post treatment (OR 4.16(1.35–12.80)) and no statistically significant increase in SPT reactivity (OR 1.18(0.74–1.86) at 9 months or 1.37 (0.93–2.01) 21 months). No effect of anthelminthic treatment was found on BMI, reported malaria-like- and allergy symptoms. No adverse effects were reported. Conclusions The study indicates that intensive community treatment of 3 monthly albendazole administration for 21 months over two years leads to a reduction in STH. This degree of reduction appears safe without any increased risk of malaria or allergies. Trial Registration Controlled-Trials.com ISRCTN83830814