Infection by Ascaris lumbricoides and bronchial hyper reactivity: An outstanding association in Venezuelan school children from endemic areas

Allergenicity of <i>Ascaris lumbricoides</i> Tropomyosin and IgE Sensitization among Asthmatic Patients in a Tropical Environment

“…Nematodes induce specific IgE and IgG against components of excretion/secretion fluids and somatic antigens, including tropomyosin [16,34]; some of these antibodies are protective [27,35,36,37], and although there are mechanisms of immunoregulation that help avoid immunopathology [38,39] they could generate adverse effects in the host. There is no evidence that the IgE responses to A. lumbricoides tropomyosin are directly related to asthma symptoms, but some epidemiological studies suggest that A. lumbricoides infection is an important risk factor for asthma and allergic sensitization [1,2,3,4]. In addition, the related nematode A. simplex induces contact dermatitis in seafood-processing workers, allergic asthma, angioedema, urticaria and anaphylaxis [40].…”

“…Parasites from infected children were defatted by Soxhlet extraction with diethyl ether, extracted for 48 h at 4°C with 50 m M NH 4 HCO 3 saturated with chloroform and then concentrated/dialyzed using a hollow-fiber filter with a nominal molecular weight cutoff of 5 kDa [2]. Protein concentration was determined by the Bradford method [23], and then the extracts were membrane filtered, sterility tested by routine bacteriological methods and lyophilized.…”

“…Ascaris is a nematode affecting approximately 1.5 billion humans, especially in tropical regions, and there are reasons to think that this could influence the natural history of allergic diseases. For example, the infection has been described as a risk factor for wheezing, asthma, severe asthma and sensitization to inhaled allergens [1,2,3,4], and experimental infection with Ascaris suum induces IgE-mediated asthma, histamine release and airway responses after aerosol challenge [5,6]. We found that there are at least 12 IgE-binding components in A. suum extract and identified as tropomyosin a component of 40–42 kDa with intense IgE-binding signals and cross-reactivity with mite extracts [7], suggesting that in order to evaluate the role of A. lumbricoides as risk factor for asthma it is necessary to obtain more information about its allergens.…”

Human Ascariasis Increases the Allergic Response and Allergic Symptoms

“…The next link was the finding that both, helminthiases and allergy, were associated with high levels of total IgE, which was further extended to other features of the immune responses to both processes [65][66][67][68]. This has been followed by epidemiological reports that, using several approaches, have shown that ascariasis is a risk factor for asthma [69][70][71][72][73][74][75][76][77]. However, although there is abundant scientific literature supporting the boosting effect of ascariasis on allergic responses [5, 63- (Table 2), a number of questions remain regarding the mechanisms for inducing an increased allergic response and asthma symptoms in a condition naturally accompanied by immunosuppression (reviewed in [99,100]).…”

“…Natural infection is associated with a polarized Th2 cytokine response and high levels of total and anti-Ascaris IgE [5,65,73,[78][79][80][81][82][83][84][85] In some individuals, natural infection induces IgE-mediated allergic respiratory and cutaneous symptoms [63,86,87] In experimental human and animal models, bronchial challenges with Ascaris extract induce asthma symptoms [64,66,67] Experimental ascariasis in animals enhances IgE response to bystander antigens [88][89][90][91] Human ascariasis enhances IgE response to mite species-specific allergens [92, 93•, 94•] Several epidemiological surveys have found that ascariasis is a risk factor for asthma and atopy [69-75, 93•, 94•, 95, 96•] IgE responses to Ascaris allergens is more frequent and stronger in mite-sensitized asthmatic patients [76,81,97,98] could also increase symptoms and severity of this disease. Ascaris components and host genetic background influencing this boosting effect are only beginning to be unraveled, and deserve further investigations.…”