The level of anti-sporozoite antibodies in a highly endemic malaria area and its relationship with exposure to mosquitoes

Abstract

The relationship between the humoral immune response to the conserved repeated epitope of the Plasmodium falciparum sporozoite and exposure to the mosquito vectors was examined in a study carried out in rural southern Tanzania, an area highly endemic for malaria. Considerable aggregation of the immune response between houses was observed. A statistically significant portion of this aggregation could be explained by differences in individual exposure to mosquitoes. However, two-thirds of the variance due to aggregation between households could not be accounted for, so that antibody level after controlling for exposure remained aggregated. Most of the variability in the development of the immune response was between individuals within households, and may be related to individual differences in behaviour and attractiveness to mosquitoes. The observed correlation of the immune response with exposure was due to continual exposure during several months, whereas recent exposure had almost no effect on the immune response observed in an endemic area. We concluded that in a highly endemic area the anti-sporozoite antibody level cannot be used as an indicator of recent infection and has only limited use as an indicator of continual infection.