Cellular immune response of asthmatic children in the presence of anti-Ascaris antibody

Highlights

• Anti-Ascaris IgE was associated with a higher risk of asthma.

• Anti-Asc IgG1 could be considered a protective factor against asthma.

• Levels of cytokines were measured using a cytometric bead array.

• Levels of IL-6, but not TNF-α, depended on the presence of anti-Asc IgG1 in serum.

• Anti-Asc IgG1 seems to favor a decrease in neutrophils and increase in IL-6.

Abstract

The presence of anti-Ascaris (anti-Asc) immunoglobin isotypes alters the risk of allergic asthma. In this study, we analyzed the relationships between serum levels of anti-Asc IgE, IgG1, and IgG4, without concurrent infection by the parasite, and the presence of asthma. We measured cytokine levels from Th1, Th2, and Th17 profiles. Children aged 2–14 years old, asthmatics (n = 64), and non-asthmatics (n = 40) were selected according to the International Study of Asthma and Allergies in Childhood criteria. Asthmatic patients who had positive skin allergy tests were considered to have allergic asthma. Stool exams were performed to exclude children who were parasitized by helminths/protozoans and blood samples were collected in non-parasitized individuals. We performed peripheral blood leukocyte counts and in vitro culture following mitogenic stimulation. Levels of cytokines (IL-2, IL-4, IL-6, IL-10, TNF-α, IFN-γ, and IL-17) in the supernatants were measured using a cytometric bead array. Titration of serum total IgE and IgE specific to Ascaris were obtained using ImmunoCAP; IgG1 and IgG4 titers were measured using enzyme-linked immunosorbent assays. Anti-Asc IgE was associated with a higher risk of asthma and an increase in the number of eosinophils and neutrophils. By contrast, anti-Asc IgG1 could be considered a protective factor against asthma, associated with lower levels of circulating neutrophils. There were high levels of IL-6 and TNF-α in asthmatics. Levels of IL-6, but not TNF-α, depended on the presence of anti-Asc IgG1 in serum. Anti-Asc IgE appears to increase risk of asthma, and anti-Asc IgG1 appears to favor decreased neutrophil counts and increased IL-6 levels.

Introduction

Ascaris lumbricoides (Asc) antigens are characterized by molecular mimicry of several allergens (Acevedo and Caraballo, 2011; Amoah et al., 2014; Sousa-Santos et al., 2019) and are able to stimulate Th2 subtype immune responses with production of IL-4, IL-5, IL-9, and IL-13, high levels of IgE, as well as mastocyte and eosinophil activation (Bethony et al., 2006; Corrigan, 2012). Th1 cytokines (IFN-γ, TNF-α and IL-6) are also present at high levels in asthma (Cho et al., 2005; Brightling et al., 2008; Grubek-Jaworska et al., 2012) and Th17 cells are associated with greater asthma severity (Alcorn et al., 2010). A. lumbricoides infection results in generation of regulatory T cells (Treg) and production of immunosuppressive cytokines (IL-10 and TGF-β) (Amoah et al., 2014).

The relationship between Ascaris infection and asthma is complex. Studies have generated conflicting results. No association was found between active infection and asthma symptoms in studies by Moncayo et al., 2013 and Hawlader et al., 2014. However, the association between these variables appeared to depend on parasite burden. By contrast, Lynch et al. (1998) reported that the low prevalence of allergic diseases and atopy in Venezuelan children was associated with active infection, characterized by high parasitic burden. Similarly, in a rural community in Colombia, moderate-to-severe ascariasis was shown to be protective against asthma (Zakzuk et al., 2018).

The classes of serum anti-Asc antibodies appear to influence the relationship between Ascaris infection and asthma. Anti-Asc IgE is a risk factor for asthma and allergic rhinitis symptoms, positivity on allergy skin tests, increased total IgE levels, higher peripheral blood eosinophil counts, and bronchial hyperreactivity (Obihara et al., 2006; Hunninghake et al., 2007; Moncayo et al., 2013; Zakzuk et al., 2018; Takeuchi et al., 2019). The presence of anti-Asc IgG was associated with higher levels of total IgE, eosinophilia, and a lower risk of atopy (Karadag et al., 2006). The anti-Asc IgG4 isotype can be used as a chronic infection marker (Santra et al., 2001; Cooper et al., 2003); it has also been associated with higher levels of total IgE in patients with respiratory allergy (Medeiros et al., 2006). In these studies, individuals were actively infected with A. lumbricoides. Except in the work of Moncayo et al. (2013), who analyzed a group of individuals who were uninfected, but who had positive anti-Asc IgE in the serum, the authors observed an increase in the risk of wheeze (atopic and non-atopic) and IgE anti-allergen positive. Nevertheless, the role of specific antibodies (in isolation from active infection) in the immune response to asthma has not been studied. Isotypes other than IgG1 were not evaluated, despite their being present in higher concentrations in human serum (Hamilton, 2001).

A strategy pursued by the Brazilian Ministry of Health involved mass treatment of public school children in disadvantaged communities (Brazilian Ministry of Health, 2012). The program allowed evaluation of populations from endemic areas that were not infected with geohelminths, but instead had been sensitized to parasite antigens, particularly specific IgE, IgG1, and IgG4. In these children, the role of these isotypes in modulating allergic responses remains unclear.

Therefore, in the present study, we analyzed the relationships between serum anti-Asc IgE, IgG1 and IgG4, without concurrent infection by the parasite, and the presence of asthma as well as the cytokines levels of Th1, Th2, and Th17 profiles.