The development of TH2 responses from infancy to 4 years of age and atopic sensitization in areas endemic for helminth infections

Background: Helminth infections and allergies are associated with TH2 responses. Whereas the development of TH2 responses and allergic disorders in pediatric populations has been examined in affluent countries, no or little data exist from low income regions of the world. The aim of this study is to examine factors influencing the development of TH2 responses of children born in areas endemic for helminth infections and to relate these factors to atopic sensitization at 4 years of age.

Methods: Data were collected from pregnant mothers on helminth infections, education and socioeconomic status (SES). Total IgE, IL-5 in response to mitogen, and helminth antigens were measured in children at 2, 5, 12, 24 and 48 months of age. Skin prick testing (SPT) and allergen-specific IgE were determined at 4 years of age.

Results: Strong TH2 responses were seen at 5 months of age and increased with time. Although maternal filarial infection was associated with helminth-antigen specific TH2 responses, it was low maternal education or SES but not helminth infection, which was associated with the development of high total IgE and PHA-induced IL-5. At 4 years of age when allergen reactivity was assessed by SPT, the high general TH2 responses did not translate into higher prevalence of SPT. The risk factor for SPT reactivity was low maternal education which decreased the risk of SPT positivity to allergens (adjusted OR, 0.32; 95% CI, 0.12 - 0.87) independently of maternal filarial infection which tended to reduce the child's risk for being SPT positive (adjusted OR, 0.35; 95% CI, 0.07 - 1.70).

Conclusions: In areas endemic for helminths, potent TH2 responses were seen early in life, but did not translate into a higher SPT reactivity to allergens. Therefore, in many parts of the world TH2 responses in general and IgE in particular cannot be used for diagnosis of allergic diseases.