THE EFFECTS OF VECTOR CONTROL ON THE ANTIBODY-RESPONSE TO ANTIGENS OFONCHOCERCA-VOLVULUS

The effects of exposure to infective larvae on the antibody response t o a cocktail of specific recombinant antigens of Onchocerca volvulus a nd to a worm extract were evaluated by comparing the responses of indi viduals from a vector controlled area with those from an area of conti nuing transmission by ELISA. Individuals from the vector controlled ar eas were found to have reduced responses to both antigen preparations. Amicrofilerdermic (mf -) individuals from the area of vector control exhibited significantly lower total and subclass IgG responses to the worm extract. In contrast, the responses to the cocktail of specific r ecombinants were significantly reduced in individuals from the area of vector control who were still microfilerdermia positive (mf +). The d istribution of IgG subclass specific responses was similar to both ant igen preparations, both dominated by the IgG4 and IgG1 subclasses. IgG 1 responses to the worm extract remained elevated in the vector contro lled individuals but IgG4 was significantly reduced in the mf - indivi duals. Both subclasses reflected the total IgG response to the cocktai l of recombinants and were significantly reduced in individuals from t he vector controlled area, when compared to individuals from the hyper endemic area. IgG1 responses to the cocktail of recombinants are signi ficantly lower than IgG4 in all individuals and virtually absent in in dividuals from the vector-controlled area. Measuring total IgG and IgG 4 is more sensitive than IgG1 in detecting infection, 100 or 97% respe ctively, but they remain elevated in the individuals from the vector c ontrolled areas even after 8-10 years interruption of transmission. Th ese results have important implications for the serological monitoring of control programmes in individuals who have previously been infecte d.