Immunomodulation of allergic response in children and adolescents: What we can learn from lymphatic filarial infection.

BACKGROUND: Although it is well known that allergic diseases involve a strong Th2 immune response, with production of high levels of specific IgE allergen, knowledge on the association between filarial infection and allergies, among paediatric patients is scarce. OBJECTIVE: To evaluate the allergic response patterns in cases of filarial infection by comparing peripheral eosinophils, total IgE levels, immediate hypersensitivity and cytokine levels in children and adolescents in Brazil. METHODS: This was an exploratory study with three groups: (I) with filarial infection and without allergic diseases; (II) without filarial infection and with allergic diseases; and (III) without filarial infection and without allergic diseases. The prick test and specific IgE tests for aeroallergens were performed using five antigens. Peripheral eosinophils and total IgE were also evaluated. IL-4 and IL-5 were determined using whole-blood culture stimulated by three antigens. RESULTS: Eosinophilia and elevated levels of total IgE (≥400IU/dl) were observed in all groups. The prick test was positive in 56.6% of the cases. Group I presented hypersensitive responses similar to the allergic disease groups. In the whole-blood culture stimulated by Dermatophagoides pteronyssinus, average IL-4 production did not differ significantly among the groups, but IL5 production resulting from stimulation was greater in the allergic disease groups (p<0.05). CONCLUSIONS: The allergic response pattern in group with filarial infection was similar to that of the groups with and without allergic diseases, but the response to IL-5 in the culture stimulated by D. pteronyssinus was an exclusive characteristic of the allergic group.

The epidemiological delimitation of lymphatic filariasis in an endemic area of Brazil, 41 years after the first recorded case.

In 2002, the status of lymphatic filariasis (LF) in the district of Jaboatão, in north-eastern Brazil, was reviewed, 41 years after the first case of the disease was recorded in the area. Current data from Jaboatão were compared with older information from the district that had been published, as official reports on filariasis cases and mosquitoes and as the result of population surveys, between 1948 and 1997. Although the first microfilaria-positive cases were detected in the district in 1959, it was not until 1993 that the national Ministry of Health categorized Jaboatão as an endemic area. In 2002, fingerprick samples of blood, each of about 50 microl, were collected at night (23.00-01.00 hours) from 4365 individuals in the district and used to make thick smears. Microfilariae were detected in the smears of blood from 33 (0.8%) of the subjects, 12 of whom were considered autochthonous cases of LF. The male subjects were significantly more likely to be microfilaraemic than the female (1.1% v. 0.4%; P<0.05) but there was no direct relationship between prevalence and age, the microfilaraemics varying in age from 6-64 years. The Socorro sub-district had the highest prevalence, of 2.9%. It is recommended that the National Programme to Eliminate Filariasis uses mass drug administrations and vector control throughout the district, regardless of the prevalences recorded in the latest survey.