Anti‐Onchocerca volvulus Immunoglobulin Subclass Response in Children from Sierra Leone

The humoral immune responses of a paediatric population of 224 children, 2‐15 years of age, residing in an onchocerciasis endemic area of Sierra Leone, were studied to gain information that may be useful in the serodiagnosis of prepatent and low‐level infections with Onchocerca volvulus. The antigen‐specific levels of IgG and IgG4 were determined and evaluated in the context of the parasitological status of the child. Over 87% of the microfilaria‐negative children had significant levels of antigen‐specific antibodies against O. volvulus, suggesting that a large percentage of this paediatric population were harbouring prepatent or low‐level infections. Over 60% of the children in the group that had detectable numbers of microfilariae in skin snips had elevated levels of O. vlovulus‐specific IgG4. In contrast, only 23% of the microfilaria‐negative children had detectable IgG4 responses. The results presented here indicate that measures of O. volvulus‐specific IgG4 may be a useful indicator of the parasitological status of children during the very early stages of onchocerciasis.