Effects of Ascaris lumbricoides in eosinophils, regulatory B cells and asthma severity in asthmatic patients from a helminth endemic population

Abstract

Background: Helminth infections can modify the immune response of the host and exert risk and protective effects on allergic diseases depending on the chronicity and intensity of the infection. Blood populations such as eosinophils and regulatory B cells have been independently associated with helminth infection and allergic diseases, with eosinophils being used as biomarkers for severity. However, the effects of helminth infections in these blood populations, and the predictive role of eosinophils in asthma severity is unclear in humans from endemic settings. Objectives: To characterize the effects of Ascaris lumbricoides infection in eosinophils, regulatory B cells and asthma severity in asthmatic patients from a helminth endemic population. Methods: In a rural community from the Colombia tropics, asthmatic patients were recruited and evaluated with a clinical questionnaire, specific and total IgE, complete blood counts, skin prick test, serial coprologicals and spirometry. Regulatory B cell subsets were evaluated in a subset of asthmatic patients and controls from the community. Results: A total of 82 patients with wheezing symptoms in the last year were recruited. Complete blood counts showed a mean eosinophil count of 654 (±SD 634) cells/uL, with 48,7% (n=40) of patients having eosinophils greater than 400 cells/uL. The frequency of active A.lumbricoides and T.trichiura infection were 46,3% (n=38) and 18,2% (n=15) respectively. In the multivariate analysis, A.lumbricoides sensitization was associated with a 6.9-fold increase in the odds of having eosinophils greater than 400 cells/uL (p=0.002) and House Dust Mite (HDM) sensitization was also associated with a 5,4-fold increase (p=0.008). Helminth infection was associated with higher log-transformed eosinophils independently of age and HDM sensitization.We found lower percentage of CD24+CD38+ B cells in asthmatic patients compared to control subjects and no significant differences between infected and uninfected patients for CD1dhighCD5+ and CD24highCD38high B cell subsets. Conclusion: In a rural community from the Colombian tropics, where helminths are endemic, sensitization to A.lumbricoides was more predictive of eosinophilia than sensitization to house dust mites. The frequency of regulatory B cell subsets was lower in asthmatic patients than in controls. Further research should evaluate larger cohorts and determine the basal level of eosinophils in this population and focus on the cellular function of regulatory B cells.