Antibody responses in onchocerciasis as a function of age and infection intensity

Onchocerciasis is caused by the filarial nematode Onchocerca volvulus and i s a major public health problem in West and Central Africa. With only parti al and long-term treatment currently available, there is a need to develop a suitable vaccine. We analysed the antibody response to infective L3 larva e because this stage is thought to be associated with host protective immun ity. In addition, we have related our findings to the age, gender and curre nt infection intensity of our participants: variables that may significantl y influence antibody production. Interestingly, whilst 90% of our study gro up were seropositive for adult specific immunoglobulin (Ig)E, only 23% prod uced L3 specific IgE. This is in contrast to IgG4 where seropositivity was comparable at 96% and 92%, respectively. Furthermore, IgG levels were signi ficantly affected by age and the intensity of infection but unaffected by h ost gender. This finding is independent for the IgG subclass (IgG1, IgG2, I gG3 and IgG4) and its specificity (L3 versus adult antigen). In summary, we show that L3 larvae induce little specific IgE and the antibody response s hows a different isotype balance than that against adult antigens. Both hos t and parasite variables can influence antibody production in this disease.