RESUMO
Intestinal schistosomiasis, caused by the parasitic trematode Schistosoma mansoni, is a chronic disease and the prolonged and continuous exposure to S. mansoni antigens results in a deviation of the host's immune response. For diagnosis, the Kato-Katz (KK) method is recommended, however, this method showed low accuracy in areas of low endemicity. This study aimed to characterize the cytokine and chemokine profile of individuals with an extremely low parasite load (<4 eggs per gram of feces), e.g., individuals who were detected by alternative parasitological methods, such as the saline gradient and/or Helmintex®. In order to search for immunological markers for infection, the immunological profile in serum samples of these individuals was then compared with patients detected with the KK method and with a higher parasite load and with individuals repetitively negative by extensive stool exams. The study was conducted in Northern Minas Gerais in a rural area of the Municipality of Januária. Serum samples of a total of 139 parasitologically well-characterized individuals were assessed for the following immunological markers by commercially available immunoassays: TNF-α, IL-1ß, IL-6, IL-17A, IL-5, IL-10, IL-13, IL-33, IL-27, CCL3, CCL5, CXCL10, CCL11, and CCL17. As a result, there were no significant differences in concentrations or frequencies for immunological markers between egg-negative individuals or individuals with ultra-low (<4 epg) or low (4-99 epg) parasite loads. However, we found significant correlations between egg counts and eosinophil counts and between egg counts and IL-1ß or TNF-α concentrations. The most striking alterations were found in individuals with the highest parasite load (≥100 epg). They had significantly higher TNF-α concentrations in serum when compared with individuals with a low parasite load (4-99 epg) and CCL17 concentrations were significantly elevated when compared with egg-negative individuals. Radar diagrams of frequencies for cytokine and chemokine responders in each infection group confirmed a distinct profile only in the infection group with highest parasite loads (≥100 epg).
Assuntos
Antígenos de Helmintos/imunologia , Citocinas/sangue , Eosinófilos , Schistosoma mansoni/imunologia , Esquistossomose mansoni/imunologia , Adolescente , Adulto , Animais , Contagem de Células Sanguíneas , Brasil/epidemiologia , Citocinas/imunologia , Doenças Endêmicas , Fezes/parasitologia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Contagem de Ovos de Parasitas , Esquistossomose mansoni/sangue , Esquistossomose mansoni/epidemiologia , Esquistossomose mansoni/parasitologia , Adulto JovemRESUMO
Helminth infections and allergies are characterized by a predominant type-2 immune response. In schistosomiasis, the Th-2 response is usually accompanied by induction of immunoregulatory mechanisms that contribute to worm survival and less severe schistosomiasis. Although helminth-induced immunomodulatory mechanisms seem to affect atopy, epidemiological studies on the relationship between helminths and allergy have been inconsistent, and data suggest that the modulatory effects may be influenced by helminth species, chronicity of infection, and parasite burden. Here we performed a cross-sectional study to investigate the effects of Schistosoma mansoni parasite burden and immune response on allergic reactivity of individuals living in a schistosomiasis endemic area in Brazil. Fecal samples from the participants were collected for extensive parasitological examinations by spontaneous sedimentation, Kato-Katz, Helmintex and Saline Gradient tests and molecular detection of S. mansoni by qPCR. Additionally, the concentrations of cytokines and chemokines, total IgE and IgE-reactivity to common house dust allergens were quantified from serum samples. IgE reactivity to dust allergens was detected in 47 individuals (23.8%), and 140 individuals (54.4%) were diagnosed with S. mansoni infection. Most of the infected population (108 individuals) presented very low parasite burden (≤12 eggs/g of feces). The frequency and intensity (p ≤ 0.03) of allergic reactivity were lower in S. mansoni-infected compared with non-infected individuals. Multivariable logistic regression models adjusted by age revealed that allergic reactivity was positively associated with low IL-10 response (OR, 4.55, 95% CI, 0.56-7.36) and high concentration of the inflammatory mediators IL-33 (OR, 2.70, 95% CI, 1.02-7.15) or TNF-α (OR, 6.88, 95% CI, 0.32-143.39) in serum, and inversely associated with S. mansoni infection (OR, 0.38, 95% CI, 0.16-0.87). Most importantly, the logistic regression demonstrated that the modulatory effects of Schistosoma infection depend on parasite burden, with individuals infected with ≤12 eggs/g of feces showing allergic IgE-reactivity similar to non-infected individuals Altogether, our data show that immunomodulation of allergic reactivity depends on S. mansoni burden, low type-2 inflammatory response, and high level of IL-10.