TEMPORAL CHANGES IN THE HUMORAL IMMUNE-RESPONSE OF CATTLE DURING EXPERIMENTAL INFECTIONS WITH ONCHOCERCA-LIENALIS

In order to gain insights into the immune response in onchocerciasis d uring early infection, laboratory-reared calves were infected with 100 0 Onchocerca lienalis infective larvae and examined serologically over a period of 508 days. Levels of serum antibodies measured by ELISA ag ainst adult worm extract revealed a multiphasic response, characterize d by a broadly similar profile of peaks in individual animals arising at 15-30, 79 and > 266 days after infection. Timings of these changes in responsiveness closely mirrored parasite development, coinciding wi th larval moults and with the onset of a patent infection. The levels of individual antibody isotypes directed against parasite antigens was strongly skewed. The dominant response was of IgG1, although limited reactivities were also found for IgG2 and IgM; No parasite-specific Ig A antibodies were detected. Immunoblots of adult worms extracts reveal ed a pattern of antigen recognition over time that matched the results obtained by ELISA. Again, the IgG1 response was strongest, although c ertain IgG2 and IgM specificities were well represented. In general, t here was a steady increase in the number of individual antigens recogn ized as the infection progressed, with a striking expansion of antibod y specificities from day 79 following the fourth larval moult. Antibod ies to a 16 kDa component were a prominent feature of the response fol lowing development of a patent infection. These data reveal the strong influence of parasite biology on the development of the immune respon se in onchocerciasis.