Impairment of theSchistosoma mansoni–Specific Immune Responses Elicited by Treatment with Praziquantel in Ugandans with HIV‐1 Coinfection

Elucidation of Cellular Responses in Non-human Primates With Chronic Schistosomiasis Followed by Praziquantel Treatment

For decades, mass drug treatment with praziquantel (PZQ) has been utilized to treat schistosomiasis, yet reinfection and the risk of drug resistance are among the various factors precluding successful elimination of schistosomiasis. Tractable models that replicate "real world" field conditions are crucial to effectively evaluate putative schistosomiasis vaccines. Herein, we describe the cellular immune responses and cytokine expression profiles under field conditions that include prior infection with schistosomes followed by treatment with PZQ. Baboons were exposed to Schistosoma mansoni cercariae through trickle infection over 5 weeks, allowed for chronic disease to develop, and then treated with PZQ. Peripheral blood mononuclear cells (PBMCs) were monitored for cellular immune response(s) at each disease stage and PZQ therapy. After initial infection and during chronic disease, there was an increase in non-classical monocytes, NK and NKT cells while the CD4:CD8 T cell ratio inverted from a 2:1 to 1:2.5. The cytokine expressions of PBMCs after trickle infections were polarized more toward a Th2 response with a gradual increase in Th1 cytokine expression at chronic disease stage. Following PZQ treatment, with the exception of an increase in B cells, immune cell populations reverted back toward naïve levels; however, expression of almost all Th1, Th2, and Th17 cytokines was significantly increased. This preliminary study is the first to follow the cellular immune response and cytokine expression profiles in a non-human primate model simulating field conditions of schistosomiasis and PZQ therapy, providing a promising reference in predicting the immune response to future vaccines for schistosomiasis.

Population level changes in schistosome-specific antibody levels following chemotherapy

AIMS

Previous studies have reported that chemotherapy of schistosomiasis by praziquantel in humans boosts protective antibody responses against S mansoni and S haematobium. A number of studies have reported schistosome-specific antibody levels before and after chemotherapy. Using these reports, a meta-analysis was conducted to identify predictors of population level change in schistosome-specific antibody levels after chemotherapy.

METHODS AND RESULTS

Following a systematic review, 92 observations from 26 articles published between 1988 and 2013 were included in this study. Observations were grouped by antigen type and antibody isotypes for the classification and regression tree (CART) analysis. The study showed that the change in antibody levels was variable: (a) between different human populations and (b) according to the parasite antigen and antibody isotypes. Thus, while anti-worm responses predominantly increased after chemotherapy, anti-egg responses decreased or did not show a significant trend. The change in antibody levels depended on a combination of age and infection intensity for anti-egg IgA, IgM, IgG1, IgG2 and anti-worm IgM and IgG.

CONCLUSION

The study results are consistent with praziquantel treatment boosting anti-worm antibody responses. However, there is considerable heterogeneity in post-treatment changes in specific antibody levels that is related to host age and pre-treatment infection intensity.

Effect of Schistosoma mansoni Infection on Innate and HIV-1-Specific T-Cell Immune Responses in HIV-1-Infected Ugandan Fisher Folk

In Uganda, fisher folk have HIV prevalence rates, about four times higher than the national average, and are often coinfected with Schistosoma mansoni. We hypothesized that innate immune responses and HIV-specific Th1 immune responses might be downmodulated in HIV/S. mansoni-coinfected individuals compared with HIV+/S. mansoni-negative individuals. We stimulated whole blood with innate receptor agonists and analyzed supernatant cytokines by Luminex. We evaluated HIV-specific responses by intracellular cytokine staining for IFN-γ, IL-2, and TNF-α. We found that the plasma viral load and CD4 count were similar between the HIV+SM+ and HIV+SM− individuals. In addition, the TNF-α response to the imidazoquinoline compound CL097 and β-1, 3-glucan (curdlan), was significantly higher in HIV/S. mansoni-coinfected individuals compared with HIV only-infected individuals. The frequency of HIV-specific IFN-γ+IL-2–TNF-α− CD8 T cells and IFN-γ+IL-2–TNF-α+ CD4 T cells was significantly higher in HIV/S. mansoni-coinfected individuals compared with HIV only-infected individuals. These findings do not support the hypothesis that S. mansoni downmodulates innate or HIV-specific Th1 responses in HIV/S. mansoni-coinfected individuals.

Antihelminthics in helminth-endemic areas: effects on HIV disease progression

BACKGROUND

Helminth infections, such as soil-transmitted helminths, schistosomiasis, onchocerciasis, and lymphatic filariasis, are prevalent in many countries where human immunodeficiency virus (HIV) infection is also common. There is some evidence from observational studies that HIV and helminth co-infection may be associated with higher viral load and lower CD4+ cell counts. Treatment of helminth infections with antihelminthics (deworming drugs) may have benefits for people living with HIV beyond simply clearance of worm infections.This is an update of a Cochrane Review published in 2009 and we have expanded it to include outcomes of anaemia and adverse events.

OBJECTIVES

To evaluate the effects of deworming drugs (antihelminthic therapy) on markers of HIV disease progression, anaemia, and adverse events in children and adults.

SEARCH METHODS

In this review update, we searched online for published and unpublished studies in the Cochrane Library, MEDLINE, EMBASE, CENTRAL, the World Health Organization (WHO) International Clinical Trials Registry Platform (ICRTP), ClinicalTrials.gov, and the WHO Global Health Library up to 29 September 2015. We also searched databases listing conference abstracts, scanned reference lists of articles, and contacted the authors of included studies.

SELECTION CRITERIA

We searched for randomized controlled trials (RCTs) that compared antihelminthic drugs with placebo or no intervention in HIV-positive people.

DATA COLLECTION AND ANALYSIS

Two review authors independently extracted data and assessed trials for eligibility and risk of bias. The primary outcomes were changes in HIV viral load and CD4+ cell count, and secondary outcomes were anaemia, iron deficiency, adverse events, and mortality events. We compared the effects of deworming using mean differences, risk ratios (RR), and 95% confidence intervals (CIs). We assessed the quality of evidence using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) approach.

MAIN RESULTS

Eight trials met the inclusion criteria of this review, enrolling a total of 1612 participants. Three trials evaluated the effect of providing antihelminthics to all adults with HIV without knowledge of their helminth infection status, and five trials evaluated the effects of providing deworming drugs to HIV-positive individuals with confirmed helminth infections. Seven trials were conducted in sub-Saharan Africa and one in Thailand. Antihelminthics for people with unknown helminth infection statusProviding antihelminthics (albendazole and praziquantel together or separately) to HIV-positive adults with unknown helminth infection status may have a small suppressive effect on mean viral load at six weeks but the 95% CI includes the possibility of no effect (difference in mean change -0.14 log10 viral RNA/mL, 95% CI -0.35 to 0.07, P = 0.19; one trial, 166 participants, low quality evidence).Repeated dosing with deworming drugs over two years (albendazole every three months plus annual praziquantel), probably has little or no effect on mean viral load (difference in mean change 0.01 log10 viral RNA, 95% CI: -0.03 to -0.05; one trial, 917 participants, moderate quality evidence), and little or no effect on mean CD4+ count (difference in mean change 2.60 CD4+ cells/µL, 95% CI -10.15 to 15.35; P = 0.7; one trial, 917 participants, low quality evidence). Antihelminthics for people with confirmed helminth infectionsTreating confirmed helminth infections in HIV-positive adults may have a small suppressive effect on mean viral load at six to 12 weeks following deworming (difference in mean change -0.13 log10 viral RNA, 95% CI -0.26 to -0.00; P = 0.04; four trials, 445 participants, low quality evidence). However, this finding is strongly influenced by a single study of praziquantel treatment for schistosomiasis. There may also be a small favourable effect on mean CD4+ cell count at 12 weeks after deworming in HIV-positive populations with confirmed helminth infections (difference in mean change 37.86 CD4+ cells/µL, 95% CI 7.36 to 68.35; P = 0.01; three trials, 358 participants, low quality evidence). Adverse events and mortality There is no indication that antihelminthic drugs impart additional risks in HIV-positive populations. However, adverse events were not well reported (very low quality evidence) and trials were underpowered to evaluate effects on mortality (low quality evidence).

AUTHORS' CONCLUSIONS

There is low quality evidence that treating confirmed helminth infections in HIV-positive adults may have small, short-term favourable effects on markers of HIV disease progression. Further studies are required to confirm this finding. Current evidence suggests that deworming with antihelminthics is not harmful, and this is reassuring for the routine treatment of confirmed or suspected helminth infections in people living with HIV in co-endemic areas.Further long-term studies are required to make confident conclusions regarding the impact of presumptively deworming all HIV-positive individuals irrespective of helminth infection status, as the only long-term trial to date did not demonstrate an effect.

Immunology of human schistosomiasis

There is a wealth of immunologic studies that have been carried out in experimental and human schistosomiasis that can be classified into three main areas: immunopathogenesis, resistance to reinfection and diagnostics. It is clear that the bulk of, if not all, morbidity due to human schistosomiasis results from immune-response-based inflammation against eggs lodged in the body, either as regulated chronic inflammation or resulting in fibrotic lesions. However, the exact nature of these responses, the antigens to which they are mounted and the mechanisms of the critical regulatory responses are still being sorted out. It is also becoming apparent that protective immunity against schistosomula as they develop into adult worms develops slowly and is hastened by the dying of adult worms, either naturally or when they are killed by praziquantel. However, as with anti-egg responses, the responsible immune mechanisms and inducing antigens are not clearly established, nor are any potential regulatory responses known. Finally, a wide variety of immune markers, both cellular and humoral, can be used to demonstrate exposure to schistosomes, and immunologic measurement of schistosome antigens can be used to detect, and thus diagnose, active infections. All three areas contribute to the public health response to human schistosome infections.

A wake up call for urinary schistosomiasis: reconciling research effort with public health importance

This review considers the current status of urinary schistosomiasis, caused by infection with Schistosoma haematobium, and argues that greater research effort and focus are needed to improve understanding of this neglected tropical disease (NTD). The inappropriateness of relying solely on data concerning the much more extensively studied intestinal form of schistosomiasis caused by S. mansoni is highlighted. The current lack of genome and transcriptome information for S. haematobium is directly hindering further targeted research and must be quickly rectified. Recent molecular phylogenies caution the expectation of similarities between schistosome species and highlight the close relationships of species within the S. haematobium group. Treatment, current and prospective drugs and vaccines, together with diagnosis are considered, highlighting the differences associated with urinary schistosomiasis. This infection has a significant and specific impact on the urino-genital system and has a strong association with bladder cancer, leading to severe and chronic morbidity. There is a clear need for new clinical initiatives in this area to better quantify the disease burden. Furthermore, emerging associations with HIV and other pathogens need to be closely monitored. Research is urgently needed to improve current knowledge in order to develop the next generation of control tools.

Effect of praziquantel treatment of Schistosoma mansoni during pregnancy on intensity of infection and antibody responses to schistosome antigens: results of a randomised, placebo-controlled trial

Background

Praziquantel treatment of schistosomiasis during pregnancy was only recommended in 2002; hence the effects of treatment during pregnancy are not fully known. We have therefore evaluated the effects on infection intensity and the immunological effects of praziquantel treatment against Schistosoma mansoni during pregnancy, compared with treatment after delivery.

Methods

A nested cohort of 387 Schistosoma mansoni infected women was recruited within a larger trial of de-worming during pregnancy. Women were randomised to receive praziquantel or placebo during pregnancy. All women were treated after delivery. Infection intensity after treatment was assessed by a single Kato-Katz examination of stool samples with duplicate slides and categorised as undetected, light (1–99 eggs per gram (epg)), moderate (100–399 epg) or heavy (≥400 epg). Antibodies against S. mansoni worm and egg antigens were measured by ELISA. Results were compared between women first treated during pregnancy and women first treated after delivery.

Results

At enrolment, 252 (65.1%) of the women had light infection (median (IQR) epg: 35 (11, 59)), 75 (19.3%) moderate (median (IQR) epg: 179(131, 227)) and 60 (15.5%) had heavy infection (median (IQR) epg: 749 (521, 1169)) with S. mansoni. At six weeks after praziquantel treatment during pregnancy S. mansoni infection was not detectable in 81.9% of the women and prevalence and intensity had decreased to 11.8% light, 4.7% moderate and 1.6% heavy a similar reduction when compared with those first treated after delivery (undetected (88.5%), light (10.6%), moderate (0.9%) and heavy (0%), p = 0.16). Parasite specific antibody levels were lower during pregnancy than after delivery. Praziquantel treatment during pregnancy boosted anti-worm IgG isotypes and to a lesser extent IgE, but these boosts were less pronounced than in women whose treatment was delayed until after delivery. Praziquantel had limited effects on antibodies against egg antigens.

Conclusion

S mansoni antigen-specific antibody levels and praziquantel-induced boosts in antibody levels were broadly suppressed during pregnancy, but this was not associated with major reduction in the efficacy of praziquantel. Long-term implications of these findings in relation to resistance to re-infection remain to be explored.

Trial registration

International Standard Randomised Controlled Trial Number for the current study: ISRCTN32849447 http://www.controlled-trials.com/ISRCTN32849447/elliott

Interactions between schistosomiasis and infection with HIV-1

In many regions of the world, both schistosomiasis and HIV/AIDS are endemic, resulting in patients harbouring co-infections. Because interaction with host CD4(+) T cells is a characteristic of schistosome as well as HIV-1 infections, bi-directional disease effects may be sufficiently different from sequelae caused by either infectious agent alone to warrant alteration of public health approaches in areas of co-endemnicity. Studies published over the past decade provide useful insights into interactions between schistosomiasis and infection with HIV-1, and overall support the hypothesis that special emphasis on treatment of schistosomiasis in populations with elevated prevalence or risk of HIV-1 infection is justified.

Helminths and HIV infection: epidemiological observations on immunological hypotheses

Parasitic helminths have co-evolved with the mammalian immune system. Current hypotheses suggest that immunological stimulation in the presence of helminths is balanced by immuno-regulation and by the broad spectrum of mechanisms possessed by helminths for countering the host immune response. The degree to which this balance is perfected, and the mechanisms by which this is achieved, vary between helminth species; we suggest that this is reflected not only in the degree of pathology induced by helminths but also in a variety of relationships with HIV infection and HIV disease. Available epidemiological data regarding interactions between helminths and HIV are largely observational; results are variable and generally inconclusive. Well designed, controlled intervention studies are required to provide definitive information on the species-specific nature of these interactions and on the advantages, disadvantages and optimal timing of de-worming in relation to HIV infection.

Gastrointestinal parasites in the immunocompromised

PURPOSE OF REVIEW

Parasites and other infections have many effects on the gastrointestinal tract of individuals who are immunocompromised. Few reviews focus on parasitic infections, which are covered here.

RECENT FINDINGS

The review first examines recent advances in our understanding of the taxonomy, diagnosis and treatment of pathogens such as cryptosporidia, cyclospora, isospora and microsporidia, which are recognized causes of diarrhoea in the immunocompromised, and discusses possible links between amoebiasis and HIV. The complex interactions of both intact and abnormal immune systems with helminth infections such as hookworm and strongyloidiasis, and with trematode infections such as schistosomiasis, are receiving increasing attention. These are discussed, together with the novel concept of using live helminths to treat inflammatory bowel disease.

SUMMARY

Parasitic infections remain a significant problem for immunocompromised individuals in resource-poor settings, and further work is needed to develop accessible diagnostic tests and to improve our understanding and management of their pathogenic effects. New concepts about the interactions of helminths with host immunity suggest the need for collection of further epidemiological and clinical data to unravel the complexities of such immunological interactions.

Immunology of human schistosomiasis: off the beaten path

Reviews of the immunology of human schistosomiasis generally address the host's protective responses against infection or the factors associated with development of severe pathology. However, there is a growing recognition that the high number of patients expressing moderate morbidity, rather than the few patients with severe morbidity, accounts for the greatest public health impact of schistosomiasis. Therefore, other aspects of the host immune response that have received relatively little attention may actually provide pivotal answers in our understanding and management of the morbidity associated with human schistosomiasis. This review highlights lines of investigation that focus on how immune responses to schistosomiasis may affect schistosomiasis-associated anaemia, alter susceptibility or disease progression during co-infections, and influence effective execution of mass treatment programmes.

Morbidity in schistosomiasis: an update

PURPOSE OF REVIEW

Schistosomiasis is an important poverty-related health problem and more than 200 million people are infected. This review summarizes papers from April 2003 to June 2004 with a focus on schistosomiasis morbidity and the various factors that affect the level of morbidity in endemic populations. The aim is to provide an update on the current state of knowledge and, hopefully, thereby stimulate continued research interest in this important area.

RECENT FINDINGS

Research into the immune responses associated with severe morbidity has provided new insights into the mechanisms of immune regulation as well as the role of genetic predisposition to periportal fibrosis. Malaria and schistosomiasis are co-endemic and co-infection with malaria may increase the level of morbidity in hepatosplenic schistosomiasis, and alter the host immune response towards schistosome antigens. Schistosome infections may render the host more susceptible to human immunodeficiency virus infection by either interfering with immune responses or increasing the risk of transmission due to genital lesions. An important advance in schistosomiasis research, and parasite genomics, is the recent availability of two major Schistosoma mansoni and Schistosoma japonicum DNA bioinformatic resources.

SUMMARY

Significant advances have been achieved in our understanding of the epidemiology, immunology and genetics of schistosomiasis, and the various factors that may influence morbidity. However, good research is vital for sustainable disease control, and continued progress requires a critical mass of researchers with a range of expertise from basic parasite biology to public-health interventions. It is therefore important to strengthen research capacity in endemic countries.