Pathogens exposure reduces atopy but not wheezing in Brazilian children
Published Online: October 31, 2011
The epidemic of asthma and atopy has been explained by alterations in immune responses related to a reduction in childhood infections. However, the findings of epidemiological studies investigating the association between infection and atopy or asthma are inconsistent, and none have investigated the effects of pathogen exposures on allergy in a developing country environment in a context where intestinal helminth infections are endemic.
In a research article to be published in The Journal of Allergy and Clinical Immunology (JACI) Alcantara-Neves et. al., report the findings of a study done in Brazilian children living in poor neighborhoods in the city of Salvador, in which they investigated the associations between eight different pathogens (Herpes simplex, Herpes zoster, Epstein-Barr and Hepatitis A viruses; Toxoplasma gondii, Helicobacter pylori, Ascaris lumbricoides and Trichuris trichiura) with allergen skin prick test reactivity, allergen-specific IgE (sIgE) and wheezing.
Not having IgG to Toxoplasma gondii was associated with a higher prevalence of sIgE (≥0.70 kU/L), while absence of infections with T. gondii, A. lumbricoides and H. simplex and Epstein-Barr viruses were associated with a higher prevalence of SPT. Children with three or fewer infection markers had a higher prevalence of sIgE and SPT compared with those with four or more infection markers. However, individual infections or the burden of infection were not associated with the prevalence of atopic or non-atopic wheeze. When stratified by age, the observed association between pathogen burden and prevalence of atopy was stronger in the oldest age group.
The findings provide support for the idea that the mechanism proposed for the “hygiene hypothesis” is operating in an urban Latin American context but it expression is so far restricted to the atopic status of individuals and not on the perceived asthma symptoms.
The Journal of Allergy and Clinical Immunology (JACI) is the official scientific journal of the AAAAI, and is the most-cited journal in the field of allergy and clinical immunology.