Helminths and skewed cytokine profiles increase tuberculin skin test positivity in Warao Amerindians

Current Epidemiology of Pediatric Tuberculosis

Tuberculosis (TB) is a communicable disease that is a major cause of ill health and one of the leading causes of death worldwide. Children act as reservoirs of infection out of which future cases develop. Without the successful detection and treatment of TB infection and disease in children, elimination strategies for TB will be ineffective. India has a severe problem with TB in children, which accounts for around 31% of the global pediatric TB load. However, over the past 10 y, children have consistently made up 6-7% of all patients treated yearly under the National Tuberculosis Elimination Programme (NTEP). There is an estimated detection gap of 56% in India, which is the reason for many missed cases of TB in children. Only 3% of children less than 14 y with MDR/RR-TB, are reported from India, which again is an underestimation of the actual incident cases. Population density, housing and living conditions, environmental conditions, cultural practices, age of the child, exposure to tobacco and other environmental pollutants, the virulence of the mycobacterial strain and their genetics, host genetics, BCG vaccination, malnutrition, immunodeficiency are some of the risk factors for TB exposure, infection and disease in children. Understanding the natural history as well as the epidemiology of childhood TB is important to assess which children are the most vulnerable. It would also guide us in understanding the burden of pediatric TB on a regional, national, or global level, thus facilitating the appropriate targeting of health resources and also guiding policy-making decisions.

Cytokine Responses during Mycobacterium tuberculosis H37Rv and Ascaris lumbricoides Costimulation Using Human THP-1 and Jurkat Cells, and a Pilot Human Tuberculosis and Helminth Coinfection Study

BACKGROUND

Helminth infections are widespread in tuberculosis-endemic areas and are associated with an increased risk of active tuberculosis. In contrast to the pro-inflammatory Th1 responses elicited by Mycobacterium tuberculosis (Mtb) infection, helminth infections induce anti-inflammatory Th2/Treg responses. A robust Th2 response has been linked to reduced tuberculosis protection. Several studies show the effect of helminth infection on BCG vaccination and TB, but the mechanisms remain unclear.

AIM

To determine the cytokine response profiles during tuberculosis and intestinal helminth coinfection.

METHODS

For the in vitro study, lymphocytic Jurkat and monocytic THP-1 cell lines were stimulated with Mtb H37Rv and Ascaris lumbricoides (A. lumbricoides) excretory-secretory protein extracts for 24 and 48 h. The pilot human ex vivo study consisted of participants infected with Mtb, helminths, or coinfected with both Mtb and helminths. Thereafter, the gene transcription levels of IFN-γ, TNF-α, granzyme B, perforin, IL-2, IL-17, NFATC2, Eomesodermin, IL-4, IL-5, IL-10, TGF-β and FoxP3 in the unstimulated/uninfected controls, singly stimulated/infected and costimulated/coinfected groups were determined using RT-qPCR.

RESULTS

TB-stimulated Jurkat cells had significantly higher levels of IFN-γ, TNF-α, granzyme B, and perforin compared to unstimulated controls, LPS- and A. lumbricoides-stimulated cells, and A. lumbricoides plus TB-costimulated cells (p < 0.0001). IL-2, IL-17, Eomes, and NFATC2 levels were also higher in TB-stimulated Jurkat cells (p < 0.0001). Jurkat and THP-1 cells singly stimulated with TB had lower IL-5 and IL-4 levels compared to those singly stimulated with A. lumbricoides and those costimulated with TB plus A. lumbricoides (p < 0.0001). A. lumbricoides-singly stimulated cells had higher IL-4 levels compared to TB plus A. lumbricoides-costimulated Jurkat and THP-1 cells (p < 0.0001). TGF-β levels were also lower in TB-singly stimulated cells compared to TB plus A. lumbricoides-costimulated cells (p < 0.0001). IL-10 levels were lower in TB-stimulated Jurkat and THP-1 cells compared to TB plus A. lumbricoides-costimulated cells (p < 0.0001). Similar results were noted for the human ex vivo study, albeit with a smaller sample size.

CONCLUSIONS

Data suggest that helminths induce a predominant Th2/Treg response which may downregulate critical Th1 responses that are crucial for tuberculosis protection.

IL-4 and helminth infection downregulate MINCLE-dependent macrophage response to mycobacteria and Th17 adjuvanticity

The myeloid C-type lectin receptor (CLR) MINCLE senses the mycobacterial cell wall component trehalose-6,6'-dimycolate (TDM). Recently, we found that IL-4 downregulates MINCLE expression in macrophages. IL-4 is a hallmark cytokine in helminth infections, which appear to increase the risk for mycobacterial infection and active tuberculosis. Here, we investigated functional consequences of IL-4 and helminth infection on MINCLE-driven macrophage activation and Th1/Th17 adjuvanticity. IL-4 inhibited MINCLE and cytokine induction after macrophage infection with Mycobacterium bovis bacille Calmette-Guerin (BCG). Infection of mice with BCG upregulated MINCLE on myeloid cells, which was inhibited by IL-4 plasmid injection and by infection with the nematode Nippostrongylus brasiliensis in monocytes. To determine the impact of helminth infection on MINCLE-dependent immune responses, we vaccinated mice with a recombinant protein together with the MINCLE ligand trehalose-6,6-dibehenate (TDB) as adjuvant. Concurrent infection with N. brasiliensis or with Schistosoma mansoni promoted T cell-derived IL-4 production and suppressed Th1/Th17 differentiation in the spleen. In contrast, helminth infection did not reduce Th1/Th17 induction by TDB in draining peripheral lymph nodes, where IL-4 levels were unaltered. Upon use of the TLR4-dependent adjuvant G3D6A, N. brasiliensis infection impaired selectively the induction of splenic antigen-specific Th1 but not of Th17 cells. Inhibition of MINCLE-dependent Th1/Th17 responses in mice infected with N. brasiliensis was dependent on IL-4/IL-13. Thus, helminth infection attenuated the Th17 response to MINCLE-dependent immunization in an organ- and adjuvant-specific manner via the Th2 cytokines IL-4/IL-13. Taken together, our results demonstrate downregulation of MINCLE expression on monocytes and macrophages by IL-4 as a possible mechanism of thwarted Th17 vaccination responses by underlying helminth infection.

Immunological Interactions between Intestinal Helminth Infections and Tuberculosis

Helminth infections are among the neglected tropical diseases affecting billions of people globally, predominantly in developing countries. Helminths’ effects are augmented by coincident tuberculosis disease, which infects a third of the world’s population. The role of helminth infections on the pathogenesis and pathology of active tuberculosis (T.B.) remains controversial. Parasite-induced suppression of the efficacy of Bacille Calmette-Guerin (BCG) has been widely reported in helminth-endemic areas worldwide. T.B. immune response is predominantly proinflammatory T-helper type 1 (Th1)-dependent. On the other hand, helminth infections induce an opposing anti-inflammatory Th2 and Th3 immune-regulatory response. This review summarizes the literature focusing on host immune response profiles during single-helminth, T.B. and dual infections. It also aims to necessitate investigations into the complexity of immunity in helminth/T.B. coinfected patients since the research data are limited and contradictory. Helminths overlap geographically with T.B., particularly in Sub-Saharan Africa. Each disease elicits a response which may skew the immune responses. However, these effects are helminth species-dependent, where some parasites have no impact on the immune responses to concurrent T.B. The implications for the complex immunological interactions that occur during coinfection are highlighted to inform government treatment policies and encourage the development of high-efficacy T.B. vaccines in areas where helminths are prevalent.

Effects of parasites coinfection with other pathogens on animal host: A literature review

A parasite-host relationship is complicated and largely remained poorly understood, especially when mixed infections involving pathogenic bacteria and viruses are present in the same host. It has been found that most parasites are able to manipulate the host's immune responses to evade or overcome its defense systems. Several mechanisms have been postulated that may explain this phenomenon in different animal species. Recent evidence suggests that coinfections involving many parasitic species alter the host's vulnerability to other microorganisms, hinder diagnostic accuracy, and may negatively impact vaccination by altering the host's immune responsiveness. The objective of this review was to provide a comprehensive summary of the current understanding of how parasites interact with other pathogens in different animal species. A better understanding of this complex relationship will aid in the improvement efforts of disease diagnosis, treatment, and control measures such as novel and effective vaccines and therapeutics for infectious diseases.

Helminth species dependent effects on Th1 and Th17 cytokines in active tuberculosis patients and healthy community controls

Despite that the impact of different helminth species is not well explored, the current dogma states that helminths affect the Th1/Th2 balance which in turn affects the risk of tuberculosis (TB) reactivation and severity of disease. We investigated the influence of helminth species on cytokine profiles including IL-17A in TB patients and healthy community controls (CCs). In total, 104 newly diagnosed pulmonary TB patients and 70 HIV negative and QuantiFERON negative CCs in Gondar, Ethiopia were included following helminth screening by stool microscopy. Plasma samples and ex vivo stimulation of peripheral blood mononuclear cells (PBMCs) with purified protein derivative (PPD) and Staphylococcus enterotoxin B (SEB) was used to determine cytokine profiles by cytometric bead array. In CCs, Ascaris lumbricoides or Schistosoma mansoni infections were associated with an impaired Th1-type response (IFN-gamma, IL-6 and TNF-alpha) in PBMCs mainly with SEB stimulations, whereas in TB patients only hookworm infection showed a similar pattern. Among CCs, the IL-17A response in PBMCs stimulated with SEB was higher only for S. mansoni, whereas in TB patients, the elevated systemic IL-17A plasma level was significantly suppressed in hookworm infected TB patients compared to patients without helminth coinfection. Following treatment of TB and helminth infection there was a general decrease in ex vivio IL-10 and TNF-alpha production in unstimulated, PPD or SEB stimulated PBMCs that was the most pronounced and significant in TB patients infected with S. mansoni, whereas the follow-up levels of IFN-gamma and IL-17A was significantly increased only in TB patients without helminth coinfection from PBMCs stimulated mainly with SEB. In summary, in addition to confirming helminth specific effects on the Th1/Th2 response before and after TB treatment, our novel finding is that IL-17A was impaired in helminth infected TB patients especially for hookworm, indicating a helminth species-specific immunoregulatory effect on IL-17A which needs to be further investigated.

Effect of Helicobacter pylori and Helminth Coinfection on the Immune Response to Mycobacterium tuberculosis

Tuberculosis remains one of the main causes of morbidity and mortality worldwide despite decades of efforts to eradicate the disease. Although the immune response controls the infection in most infected individuals (90%), the ability of the bacterium to persist throughout the host's life leads to a risk of reactivation. Underlying conditions including human immunodeficiency virus (HIV) infection, organ transplantation, and immunosuppressive therapies are considered risk factors for progression to active disease. However, many individuals infected with Mycobacterium tuberculosis may develop clinical disease in the absence of underlying immunosuppression. It is also possible that unknown conditions may drive the progression to disease. The human microbiota can be an important modulator of the immune system; it can not only trigger inflammatory disorders, but also drive the response to other infectious diseases. In developing countries, chronic mucosal infections with Helicobacter pylori and helminths may be particularly important, as these infections frequently coexist throughout the host's life. However, little is known about the interactions of these pathogens with the immune system and their effects on M. tuberculosis clinical disease, if any. In this review, we discuss the potential effects of H. pylori and helminth co-infections on the immune response to M. tuberculosis. This may contribute to our understanding of host-pathogen interactions and in designing new strategies for the prevention and control of tuberculosis.

Protective Effect of Intestinal Helminthiasis Against Tuberculosis Progression Is Abrogated by Intermittent Food Deprivation

Background

Tuberculosis (TB) is still a major challenge for humankind. Because regions with the highest incidence also have a high prevalence of helminthiasis and nutritional scarcity, we wanted to understand the impact of these on TB progression.

Methods

We have developed an experimental murine model for active TB in C3HeB/FeJ, coinfected with Trichuris muris and Heligmosomoides polygyrus nematodes, and exposed to an environmental mycobacterium (M. manresensis) and intermittent fasting. Cause-effect relationships among these factors were explored with Partial Least Squares Path modelling (PLSPM).

Results

Previous parasitization had a major anti-inflammatory effect and reduced systemic levels of ADA, haptoglobin, local pulmonary levels of IL-1β, IL-6, TNF-α, CXCL-1, CXCL-5 and IL-10. Oral administration of heat-killed M. manresensis resulted in a similar outcome. Both interventions diminished pulmonary pathology and bacillary load, but intermittent food deprivation reduced this protective effect increasing stress and inflammation. The PLSPM revealed nematodes might have protective effects against TB progression.

Conclusions

Significantly higher cortisol levels in food-deprivation groups showed it is a stressful condition, which might explain its deleterious effect. This highlights the impact of food security on TB eradication policies and the need to prioritize food supply over deworming activities.

Assessment of Malnutrition and Intestinal Parasitoses in the Context of Crisis-Hit Venezuela: A Policy Case Study

Venezuela is in the midst of a humanitarian crisis with a dangerous cocktail of hyperinflation, violence, minimal local food production, and policies that impact the nutrition for millions of Venezuelans. Independent data suggests that most Venezuelans are food insecure, with alarming rates of acute and chronic malnutrition, especially among children. A re-emergence of poverty-related intestinal parasitoses and anemia has aggravated their health. With little to no response from public authorities, Venezuela is now the lowest-ranked country in the world in deworming coverage. Modest independent and private epidemiological studies suggest prevalence rates as high as 60% in some regions. This article reviews public health policies regarding malnutrition and intestinal parasitoses and aims to provide a rational approach based on international recommendations for countries in crisis.

Prevalence of and risk factors associated with latent tuberculosis infection in a Latin American region

Tuberculosis (TB) represents a health problem in Colombia, and its control is focused on the search for contacts and treatment of TB cases underscoring the role of latent tuberculosis infection (LTBI) as a reservoir of Mycobacterium tuberculosis. The burden of LTBI in Colombia is unknown. We aimed to estimate the prevalence of LTBI and identify the associated risk factors. In this cross-sectional study, we recruited participants from four health care centers in Cali, Colombia. The participants were eligible if they were aged between 14 and 70 years, and all participants answered a survey evaluating their medical history and sociodemographic and lifestyle factors. LTBI status was based on tuberculin skin test (TST) positivity using two thresholds: ≥10 mm (TST-10) and ≥15 mm (TST-15). The magnitude of the associations between independent factors and dependent outcomes (LTBI status and TST induration) were evaluated by logistic regression and generalized linear models, respectively. A total of 589 individuals were included with TST positivity rates of 25.3% (TST-10) and 13.2% (TST-15). Logistic regression showed that being between age 40 and 69 years (OR = 7.28, 95% CI [1.62–32.7]), being male (OR = 1.71, 95% CI [1.04–2.84]), being employed (OR = 1.56, 95% CI [1.02–2.38]), and having a low intake of alcohol (OR = 2.40, 95% CI [1.13–5.11]) were risk factors for TST positivity, while living in the north zone (OR = 0.32, 95% CI [0.18–0.55]), living in the suburb zone (OR = 0.28, 95% CI [0.15–0.52]) and having a secondary education (OR = 0.49 95% CI [0.29–0.83]) lowered the risk of TST positivity. The generalized linear model showed that the previous predictors, as well as a low body mass index, had an effect on TST reaction size. The LTBI prevalence found in the population was moderate, reflecting the continuous transmission of M. tuberculosis. Social factors seem to play a decisive role in the risk of LTBI. Employed males, who are over 40 years of age, are overweight, have a lower level of education and have a low intake of alcohol (50–100 mL, once/week) should be a priority group for prophylactic treatment as a strategy for TB control in this city.

Interactions between helminths and tuberculosis infections: Implications for tuberculosis diagnosis and vaccination in Africa

Africa is the second most populous continent and has perennial health challenges. Of the estimated 181 million school aged children in sub-Saharan Africa (SSA), nearly half suffer from ascariasis, trichuriasis, or a combination of these infections. Coupled with these is the problem of tuberculosis (TB) caused by Mycobacterium tuberculosis (Mtb) infection, which is a leading cause of death in the region. Compared to the effect of the human immunodeficiency virus on the development of TB, the effect of chronic helminth infections is a neglected area of research, yet helminth infections are as ubiquitous as they are varied and may potentially have profound effects upon host immunity, particularly as it relates to TB infection, diagnosis, and vaccination. Protection against active TB is known to require a clearly delineated T-helper type 1 (Th1) response, while helminths induce a strong opposing Th2 and immune-regulatory host response. This Review highlights the potential challenges of helminth-TB co-infection in Africa and the need for further research.

Risk Factors for Indeterminate Interferon-Gamma Release Assay for the Diagnosis of Tuberculosis in Children-A Systematic Review and Meta-Analysis

Background: Interferon-gamma release assays (IGRA) are well-established immunodiagnostic tests for tuberculosis (TB) in adults. In children these tests are associated with higher rates of false-negative and indeterminate results. Age is presumed to be one factor influencing cytokine release and therefore test performance. The aim of this study was to systematically review factors associated with indeterminate IGRA results in pediatric patients. Methods: Systematic literature review guided by the preferred reporting items for systematic reviews and meta-analyses (PRISMA) searching PubMed, EMBASE, and Web of Science. Studies reporting results of at least one commercially available IGRA (QuantiFERON-TB, T-SPOT.TB) in pediatric patient groups were included. Random effects meta-analysis was used to assess proportions of indeterminate IGRA results. Heterogeneity was assessed using the I² value. Risk differences were calculated for studies comparing QuantiFERON-TB and T-SPOT.TB in the same study. Meta-regression was used to further explore the influence of study level variables on heterogeneity. Results: Of 1,293 articles screened, 133 studies were included in the final analysis. These assessed QuantiFERON-TB only in 77.4% (103/133), QuantiFERON-TB and T-SPOT.TB in 15.8% (21/133), and T-SPOT.TB only in 6.8% (9/133) resulting in 155 datasets including 107,418 participants. Overall 4% of IGRA results were indeterminate, and T-SPOT.TB (0.03, 95% CI 0.02-0.05) and QuantiFERON-TB assays (0.05, 95% CI 0.04-0.06) showed similar proportions of indeterminate results; pooled risk difference was-0.01 (95% CI -0.03 to 0.00). Significant differences with lower proportions of indeterminate assays with T-SPOT.TB compared to QuantiFERON-TB were only seen in subgroup analyses of studies performed in Africa and in non-HIV-infected immunocompromised patients. Meta-regression confirmed lower proportions of indeterminate results for T-SPOT.TB compared to QuantiFERON-TB only among studies that reported results from non-HIV-infected immunocompromised patients (p < 0.001). Conclusion: On average indeterminate IGRA results occur in 1 in 25 tests performed. Overall, there was no difference in the proportion of indeterminate results between both commercial assays. However, our findings suggest that in patients in Africa and/or patients with immunocompromising conditions other than HIV infection the T-SPOT.TB assay appears to produce fewer indeterminate results.

The Influence of Parasite Infections on Host Immunity to Co-infection With Other Pathogens

Parasites have evolved a wide range of mechanisms that they use to evade or manipulate the host's immune response and establish infection. The majority of the in vivo studies that have investigated these host-parasite interactions have been undertaken in experimental animals, especially rodents, which were housed and maintained to a high microbiological status. However, in the field situation it is increasingly apparent that pathogen co-infections within the same host are a common occurrence. For example, chronic infection with pathogens including malarial parasites, soil-transmitted helminths, Mycobacterium tuberculosis and viruses such as HIV may affect a third of the human population of some developing countries. Increasing evidence shows that co-infection with these pathogens may alter susceptibility to other important pathogens, and/or influence vaccine efficacy through their effects on host immune responsiveness. Co-infection with certain pathogens may also hinder accurate disease diagnosis. This review summarizes our current understanding of how the host's immune response to infection with different types of parasites can influence susceptibility to infection with other pathogenic microorganisms. A greater understanding of how infectious disease susceptibility and pathogenesis can be influenced by parasite co-infections will enhance disease diagnosis and the design of novel vaccines or therapeutics to more effectively control the spread of infectious diseases.

Tuberculosis susceptibility and protection in children

Children represent both a clinically important population susceptible to tuberculosis and a key group in whom to study intrinsic and vaccine-induced mechanisms of protection. After exposure to Mycobacterium tuberculosis, children aged under 5 years are at high risk of progressing first to tuberculosis infection, then to tuberculosis disease and possibly disseminated forms of tuberculosis, with accompanying high risks of morbidity and mortality. Children aged 5-10 years are somewhat protected, until risk increases again in adolescence. Furthermore, neonatal BCG programmes show the clearest proven benefit of vaccination against tuberculosis. Case-control comparisons from key cohorts, which recruited more than 15 000 children and adolescents in total, have identified that the ratio of monocytes to lymphocytes, activated CD4 T cell count, and a blood RNA signature could be correlates of risk for developing tuberculosis. Further studies of protected and susceptible populations are necessary to guide development of novel tuberculosis vaccines that could facilitate the achievement of WHO's goal to eliminate deaths from tuberculosis in childhood.

Review: Impact of Helminth Infection on Antimycobacterial Immunity-A Focus on the Macrophage

Successful immune control of Mycobacterium tuberculosis (MTB) requires robust CD4⁺ T cell responses, with IFNγs as the key cytokine promoting killing of intracellular mycobacteria by macrophages. By contrast, helminth infections typically direct the immune system toward a type 2 response, characterized by high levels of the cytokines IL-4 and IL-10, which can antagonize IFNγ production and its biological effects. In many countries with high burden of tuberculosis, helminth infections are endemic and have been associated with increased risk to develop tuberculosis or to inhibit vaccination-induced immunity. Mechanistically, regulation of the antimycobacterial immune response by helminths has been mostly been attributed to the T cell compartment. Here, we review the current status of the literature on the impact of helminths on vaccine-induced and natural immunity to MTB with a focus on the alterations enforced on the capacity of macrophages to function as sensors of mycobacteria and effector cells to control their replication.

Infectious diseases prevalence, vaccination coverage, and diagnostic challenges in a population of internationally adopted children referred to a Tertiary Care Children's Hospital from 2009 to 2015

Infectious diseases are common in internationally adopted children (IAC).With the objective to evaluate infectious diseases prevalence in a large cohort of IAC and to explore possible risk factors for tuberculosis (TB) and parasitic infections, clinical and laboratory data at first screening visit of all IAC (<18 years) consecutively referred to our Center in 2009 to 2015 were collected and analyzed.In total, 1612 children (median age: 5.40 years; interquartile range: 3.00-7.90) were enrolled, 123/1612 (7.60%) having medical conditions included in the special needs definition. The most frequent cutaneous infections were Molluscum contagiosum (42/1612; 2.60%) and Tinea capitis (37/1612; 2.30%). Viral hepatitis prevalence was <1% (hepatitis B virus [HBV]: 13 children, 0.80%; hepatitis C virus: 1 child, 0.10%; hepatitis A virus: 6 children, 0.40%). A parasitic infection was diagnosed in 372/1612 (23.10%) children. No risk factors for parasitosis were evidenced. Active TB was diagnosed in 4/1355 (0.3%) children, latent TB in 222/1355 (16.40%). Only 3.7% (51/1355) children had concordant positive tuberculin skin test (TST) and QuantiFERON-TB-Gold In-Tube (QFT-G-IT) results. Risk factors for TST+/QFT-G-IT- results were previous Bacille de Calmette-Guérin vaccination (adjusted odds ratio [aOR]: 2.18; 96% confidence interval [CI]: 1.26-3.79; P = 0.006), and age ≥5 years (aOR: 1.49; 95% CI: 1.06-2.11; P = 0.02). The proportion of children with nonprotective titers for vaccine-preventable diseases (VPD) ranged from 15.70% (208/1323) for tetanus to 35.10% (469/1337) for HBV.Infectious diseases were commonly observed in our cohort. The high rate of discordant TST/QFT-G results brings up questions regarding the optimal management of these children, and suggests that, at least in children older than 5 years, only QFT-G-IT results may be reliable. The low proportion of children protected for VPD, confirms importance of a timely screening.

Species dependent impact of helminth-derived antigens on human macrophages infected with Mycobacterium tuberculosis: Direct effect on the innate anti-mycobacterial response

Background

In countries with a high prevalence of tuberculosis there is high coincident of helminth infections that might worsen disease outcome. While Mycobacterium tuberculosis (Mtb) gives rise to a pro-inflammatory Th1 response, a Th2 response is typical of helminth infections. A strong Th2 response has been associated with decreased protection against tuberculosis.

Principal findings

We investigated the direct effect of helminth-derived antigens on human macrophages, hypothesizing that helminths would render macrophages less capable of controlling Mtb. Measuring cytokine output, macrophage surface markers with flow cytometry, and assessing bacterial replication and phagosomal maturation revealed that antigens from different species of helminth directly affect macrophage responses to Mtb. Antigens from the tapeworm Hymenolepis diminuta and the nematode Trichuris muris caused an anti-inflammatory response with M2-type polarization, reduced macrophage phagosome maturation and ability to activate T cells, along with increased Mtb burden, especially in T. muris exposed cells which also induced the highest IL-10 production upon co-infection. However, antigens from the trematode Schistosoma mansoni had the opposite effect causing a decrease in IL-10 production, M1-type polarization and increased control of Mtb.

Conclusion

We conclude that, independent of any adaptive immune response, infection with helminth parasites, in a species-specific manner can influence the outcome of tuberculosis by either enhancing or diminishing the bactericidal function of macrophages.

The innate immune system is the first response against invading pathogens like the bacterium Mycobacterium tuberculosis (Mtb) or parasitic worms (helminths). The adaptive immune response takes over after being primed by the innate immune response. Infection with Mycobacterium tuberculosis typically gives rise to a pro-inflammatory T-helper(Th)-1 response while helminths promote a Th2 response which is needed to combat the infection. Co-infection with both of these pathogens could lead to reduced immunity contributing to worsening of tuberculosis due to an increased Th2 response caused by helminths. We found that antigens from different helminth species (a nematode, a cestode and a trematode) caused different responses towards Mtb in macrophages. Depending on the helminth species, the macrophages can be more or less capable of combating Mtb infection and priming the adaptive immune response, which in turn would influence the outcome of tuberculosis. Thus, exposure to helminth antigens, in a species-dependent manner, could lead to a better control of Mtb infection or worsening of tuberculosis.

Stat6-Dependent Inhibition of Mincle Expression in Mouse and Human Antigen-Presenting Cells by the Th2 Cytokine IL-4

The C-type lectin receptors (CLRs) Mincle, Mcl, and Dectin-2 bind mycobacterial and fungal cell wall glycolipids and carbohydrates. Recently, we described that expression of these CLR is downregulated during differentiation of human monocytes to dendritic cells (DC) in the presence of GM-CSF and IL-4. Here, we demonstrate that the Th2 cytokine IL-4 specifically inhibits expression of Mincle, Mcl, and Dectin-2 in human antigen-presenting cells (APC). This inhibitory effect of IL-4 was observed across species, as murine macrophages and DC treated with IL-4 also downregulated these receptors. IL-4 blocked upregulation of Mincle and Mcl mRNA expression and cell surface protein by murine macrophages in response to the Mincle ligand Trehalose-6,6-dibehenate (TDB), whereas the TLR4 ligand LPS overcame inhibition by IL-4. Functionally, downregulation of Mincle expression by IL-4 was accompanied by reduced cytokine production upon stimulation with TDB. These inhibitory effects of IL-4 were dependent on the transcription factor Stat6. Together, our results show that the key Th2 cytokine IL-4 exerts a negative effect on the expression of Mincle and other Dectin-2 cluster CLR in mouse and human macrophages and DC, which may render these sentinel cells less vigilant for sensing mycobacterial and fungal ligands.

The Effect of Deworming on Tests of Tuberculosis Infection in Children With Recent Tuberculosis Exposure: A Randomized Controlled Trial

BACKGROUND

Helminth infestations are associated with T-helper cell type 2 (Th2) immune responses, leading to suppression of Th1 responses required to control Mycobacterium tuberculosis infection. We hypothesized that deworming after documented M. tuberculosis exposure might improve Th1 immune responses.

METHODS

This was a randomized controlled trial comparing the effect of early versus delayed (after 3 months) deworming on tuberculin skin testing (TST) and Quantiferon-Gold-in-tube responses among children from a setting with a known high burden of M. tuberculosis and helminth co-infection in Cape Town, South Africa. Children aged 6 to 15 years with documented M. tuberculosis exposure were enrolled. Ascaris lumbricoides status was measured by Ascaris-specific IgE and stool microscopy.

RESULTS

A total of 250 children (mean age, 9.6 years) were enrolled; 11.9% (27/227) were Ascaris stool microscopy positive and 54.2% (135/249) were Ascaris stool and/or IgE positive (Ascaris status). In univariable analysis, deworming at enrollment was not associated with a negative TST at 3 months (odds ratio, 0.61; 95% confidence interval, 0.35-1.07; P = 0.08). In stratified analysis, children with a positive Ascaris status were more likely to be TST negative at 3 months if dewormed early (odds ratio, 0.49; 95% confidence interval, 0.23-1.04; P = 0.06). In multivariable analysis, deworming was not associated with TST status (adjusted odds ratios, 0.62; 95% confidence interval, 0.34-1.10; P = 0.10). There was no association between deworming and Quantiferon-Gold-in-tube status.

CONCLUSIONS

Deworming in children with recent M. tuberculosis exposure is associated with a trend toward a negative TST result. Timing of deworming might influence interpretation of TST in settings with high burdens of tuberculosis and helminths.

Infectious Diseases of Poverty in Children: A Tale of Two Worlds

"Infectious diseases of poverty" (IDoP) describes infectious diseases that are more prevalent among poor and vulnerable populations, namely human immunodeficiency virus (HIV) infection, tuberculosis (TB), malaria, and neglected tropical diseases (NTDs). In 2013, 190,000 children died of HIV-related causes and there were 550,000 cases and 80,000 TB deaths in children. Children under age 5 account for 78% of malaria deaths annually. NTDs remain a public health challenge in low- and middle-income countries. This article provides an overview of the major IDoP that affect children. Clinicians must be familiar with the epidemiology and clinical manifestations to ensure prompt diagnosis and treatment.

Agreement between QuantiFERON®-TB Gold In-Tube and the tuberculin skin test and predictors of positive test results in Warao Amerindian pediatric tuberculosis contacts

Background

Interferon-gamma release assays have emerged as a more specific alternative to the tuberculin skin test (TST) for detection of tuberculosis (TB) infection, especially in Bacille Calmette-Guérin (BCG) vaccinated people. We determined the prevalence of Mycobacterium tuberculosis infection by TST and QuantiFERON^®-TB Gold In-Tube (QFT-GIT) and assessed agreement between the two test methods and factors associated with positivity in either test in Warao Amerindian children in Venezuela. Furthermore, progression to active TB disease was evaluated for up to 12 months.

Methods

163 HIV-negative childhood household contacts under 16 years of age were enrolled for TST, QFT-GIT and chest X-ray (CXR). Follow-up was performed at six and 12 months. Factors associated with TST and QFT-GIT positivity were studied using generalized estimation equations logistic regression models.

Results

At baseline, the proportion of TST positive children was similar to the proportion of children with a positive QFT-GIT (47% vs. 42%, p = 0.12). Overall concordance between QFT-GIT and TST was substantial (kappa 0.76, 95% CI 0.46-1.06). Previous BCG vaccination was not associated with significantly increased positivity in either test (OR 0.68, 95% CI 0.32-1.5 for TST and OR 0.51, 95% CI 0.14-1.9 for QFT-GIT). Eleven children were diagnosed with active TB at baseline. QFT-GIT had a higher sensitivity for active TB (88%, 95% CI 47-98%) than TST (55%, 95% CI 24-83%) while specificities were similar (respectively 58% and 55%). Five initially asymptomatic childhood contacts progressed to active TB disease during follow-up.

Conclusion

Replacement of TST by the QFT-GIT for detection of M. tuberculosis infection is not recommended in this resource-constrained setting as test results showed substantial concordance and TST positivity was not affected by previous BCG vaccination. The QFT-GIT had a higher sensitivity than the TST for the detection of TB disease. However, the value of the QFT-GIT as an adjunct in diagnosing TB disease is limited by a high variability in QFT-GIT results over time.

Epidemiology and disease burden of tuberculosis in children: a global perspective

Our understanding of the tuberculosis (TB) epidemic in children is incomplete due to challenges in diagnosis and reporting. Children have also been largely excluded from research and advocacy. However, the tide appears to be turning and interest in pediatric TB is increasing. In this article, we explore the epidemiology of childhood TB by first reviewing the natural history of TB in children and the factors that impact on each of the stages from exposure to disease. We then discuss how these factors affect what we see at a country and regional level. Finally, we assess the burden of childhood TB globally.

Recurrent wheezing is associated with intestinal protozoan infections in Warao Amerindian children in Venezuela: a cross-sectional survey

Background

While in developed countries the prevalence of allergic diseases is rising, inflammatory diseases are relatively uncommon in rural developing areas. High prevalence rates of helminth and protozoan infections are commonly found in children living in rural settings and several studies suggest an inverse association between helminth infections and allergies. No studies investigating the relationship between parasitic infections and atopic diseases in rural children of developing countries under the age of 2 years have been published so far. We performed a cross-sectional survey to investigate the association of helminth and protozoan infections and malnutrition with recurrent wheezing and atopic eczema in Warao Amerindian children in Venezuela.

Methods

From August to November 2012, 229 children aged 0 to 2 years residing in the Orinoco Delta in Venezuela were enrolled. Data were collected through standardized questionnaires and physical examination, including inspection of the skin and anthropometric measurements. A stool sample was requested from all participants and detection of different parasites was performed using microscopy and real time polymerase chain reaction (PCR).

Results

We observed high prevalence rates of atopic eczema and recurrent wheezing, respectively 19% and 23%. The prevalence of helminth infections was 26% and the prevalence of protozoan infections was 59%. Atopic eczema and recurrent wheezing were more frequently observed in stunted compared with non-stunted children in multivariable analysis (OR 4.3, 95% CI 1.3 – 13.6, p = 0.015 and OR 4.5, 95% CI 0.97 – 21.2, p = 0.055). Furthermore, recurrent wheezing was significantly more often observed in children with protozoan infections than in children without protozoan infections (OR 6.7, 95% CI 1.5 – 30.5).

Conclusions

High prevalence rates of atopic eczema and recurrent wheezing in Warao Amerindian children under 2 years of age were related to stunting and intestinal protozoan infections respectively. Helminth infections were not significantly associated with either atopic eczema or recurrent wheezing.

Effect of helminth-induced immunity on infections with microbial pathogens

Helminth infections are ubiquitous worldwide and can trigger potent immune responses that differ from and potentially antagonize host protective responses to microbial pathogens. In this Review we focus on the three main killers in infectious disease-AIDS, tuberculosis and malaria-and critically assesses whether helminths adversely influence host control of these diseases. We also discuss emerging concepts for how M2 macrophages and helminth-modulated dendritic cells can potentially influence the protective immune response to concurrent infections. Finally, we present evidence advocating for more efforts to determine how and to what extent helminths interfere with the successful control of specific concurrent coinfections.

High malnutrition rate in Venezuelan Yanomami compared to Warao Amerindians and Creoles: significant associations with intestinal parasites and anemia

BACKGROUND

Children in rural areas experience the interrelated problems of poor growth, anemia and parasitic infections. We investigated the prevalence of and associations between intestinal helminth and protozoan infections, malnutrition and anemia in school-age Venezuelan children.

METHODS

This cross-sectional study was conducted in 390 children aged 4-16 years from three rural areas of Venezuela: the Amazon Region, Orinoco Delta and Carabobo State. Stool samples were collected for direct parasitic examinations. Anthropometric indicators of chronic (height-for-age Z score) and acute (weight-for-height and Body Mass Index (BMI)-for-age Z score in respectively children under 5 years of age and children aged 5 years and above) malnutrition were calculated. Multivariate linear and logistic regression models were built to determine factors associated with nutritional status and polyparasitism.

RESULTS

Hookworm and Strongyloides stercoralis prevalences were highest in children from the Amazon rainforest (respectively 72% and 18%) while children from the Orinoco Delta and Carabobo State showed higher rates of Ascaris lumbricoides (respectively 28% and 37%) and Trichuris trichiura (40% in both regions). The prevalence of Giardia lamblia infection was not significantly different between regions (average: 18%). Anemia prevalence was highest in the Amazon Region (24%). Hemoglobin levels were significantly decreased in children with a hookworm infection. Malnutrition was present in respectively 84%, 30% and 13% of children from the Amazon Region, Orinoco Delta and Carabobo State. In multivariate analysis including all regions, G. lamblia and helminth infections were significantly and negatively associated with respectively height-for-age and weight-for-height/BMI-for-age Z scores. Furthermore, hemoglobin levels were positively associated with the height-for-age Z score (0.11, 95% CI 0.02 - 0.20).

CONCLUSIONS

In rural populations in Venezuela helminthiasis and giardiasis were associated with acute and chronic nutritional status respectively. These data highlight the need for an integrated approach to control transmission of parasites and improve the health status of rural Venezuelan children.