Exposure to Ascaris Associated With Decreased Lung Function, Increased Asthma Risk in Men

Exposure to Ascaris lumbricoides infection (ascariasis) was associated with significantly decreased lung function and increased asthma risk in men, according to results of a study published in The Journal of Allergy and Clinical Immunology.

Investigators measured serum Ascaris immunoglobulin G (IgG) antibodies in adults aged 18 to 47 years at 3 centers in Norway. Associations between ascariasis seropositivity, defined as IgG concentrations greater than the 90^th percentile, and lung function and asthma, were analyzed using linear and logistic regression. Associations between DNA methylation and seropositivity were also assessed via commercial methylation assay.

Overall, serum Ascaris IgG antibody concentrations were measured in a total of 671 adults, 46% of whom were women. In men only, seropositivity was associated with a decrease in forced expiratory volume in the first second of expiration (FEV₁) results (-247 mL; 95% CI, -460, -34) and an increased odds for asthma (adjusted odds ratio [aOR], 5.84; 95% CI, 1.67, 20.37). The investigators found that women seropositive for ascariasis had decreased odds of developing asthma (aOR, 0.42; 95% CI, 0.18, 0.96), wheezing (aOR, 0.63; 95% CI, 0.16, 2.44), or experiencing 3 or more asthma symptoms within the 12 months prior to enrollment (aOR, 0.24; 95% CI, 0.15, 0.40). Exposure to Ascaris was also associated with 23 differentially methylated sites among men vs 3 among women. These included hypermethylation of the MYBPC1 gene, which can regulate airway muscle contraction and differential methylation of genes linked to asthma pathogenesis (CRHR1 and GRK1) and a gene region linked to nematode infection (PRSS22).

Study limitations include that the epigenetic analysis was performed with DNA extracted from whole blood only, as other relevant tissues were unavailable. Other limitations include the inability to determine whether identified changes in DNA methylation occur on the causal pathway between Ascaris exposure and lung function. 

According to the investigators, “[these] findings suggest that men and women might respond differently to Ascaris infections and that these responses could have long-term outcomes.” They also noted a, “…need to investigate the role of helminths on long-term lung health globally, including in high- and middle-income countries, as well as in low-income countries where helminth exposure is highly prevalent.”

Reference

Jõgi NO, Kitabe N, Storaas T, et al. Ascaris exposure and its association with lung function, asthma, and DNA methylation in Northern Europe. J Allergy Clin Immunol. Published online December 14, 2021. doi: 10.1016/j.jaci.2021.11.013

This article originally appeared on Infectious Disease Advisor