Immunoepidemiology of Dracunculus medinensis infections II. Variation in antibody responses in relation to transmission season and patency

The serum antibody responses (specific IgG1, IgG4, and IgE, and total IgE) to Dracunculus medinensis infection in humans from a highly endemic area of northern Ghana were examined regularly by ELISA over a period of one year in cohorts of individuals who developed a patent D. medinensis infection du ring the study period (actively infected category), or who claimed to have never had a patent infection (endemic normal category). The results were an alyzed in relation to seasonality and time of patency of infection. For ind ividuals in the actively infected category, a clear seasonal variation in t he mean levels of specific IgG1 and IgG4 was found, with the highest levels late in the dry season and early in the rainy season, when transmission is high, and the lowest levels late in the rainy season and early in the dry season. Endemic normal individuals responded with low and fluctuating level s of specific IgG1 and with low and nonfluctuating levels of specific IgG I . For specific and total IgE, no seasonal variation was observed in any of the two infection status categories. In relation to time of patency of infe ction (only involving the category of actively infected individuals), the m ean levels of specific IgG1 and IgG4 increased from two months before paten cy of infection, peaked during patency, and then gradually decreased for fo ur months until a constant level was reached. No significant fluctuations i n the levels of specific and total IgE were observed in relation to time of patency. The present study thus showed extensive variation in levels of D. medinensis-specific IgG1 and IgG4 (but not IgE) over time. Seasonal variat ions in antibody responses may also occur in other helminth infections, esp ecially those with seasonal transmission, and these should be taken into co nsideration when interpreting the results of immunologic studies.