We also hypothesized that in younger age groups the effect of immune boosting and antibody decay in the absence of exposure would be more pronounced [22, 28]. In children aged 1–5, we found that antibody titres were not consistently higher in infected compared with noninfected children. This is likely to reflect large interindividual variation in antibody titres that learn more are at least partly the result of variation in cumulative malaria exposure that our short longitudinal study may have failed to capture. However, while we found no statistically significant difference in antibody titres between

groups of exposed and nonexposed children, we found strong evidence that the dynamics of antibody titres depend on recent parasite exposure. In children aged 1–5 years of age, we observed a decay in antibody titres during the 16-week-period of follow-up in those children who were parasite-free throughout the study or children who were not re-infected after malaria treatment at enrolment.

However, a large proportion of children (56%) in this age group became re-infected within 6 weeks of drug cure and remained parasite-positive throughout follow-up, consistent with the assumptions of intense malaria transmission in this region and little parasitic immunity in this age group. In this group, antibody titres against all malaria antigens remained stable during the 16-week period. The vast majority of these infections were submicroscopic and restricting GDC-941 our analyses to these submicroscopic infections did not change this pattern of highly stable antibody C59 in vivo titres in parasite-positive children. The fact that gSG6 antibody titres were also stable in individuals

who were consistently parasite-positive but declined in children who were never parasite-positive or who were not re-infected after treatment suggests that consistently parasite-positive children were continuously exposed to anophelines. In older children (>5 years) and adults, associations between malaria infections and antibody titres were less evident. In children 6–10 years old who were parasite-positive at enrolment but did not become re-infected after clearance of their infection, antibody titres against all antigens showed a statistically significant decline. In other categories of parasite exposure, there was no consistent pattern in antibody dynamics, although antibody titres against some antigens showed a decline over time that may be a result of reduced malaria exposure during follow-up. This decreased malaria exposure during follow-up may reflect seasonal fluctuations; there is currently no clear evidence of a decline in transmission intensity as a consequence of malaria control efforts in the region [14] but indoor residual spraying was implemented with variable coverage in the region. As expected, antibody titres were largely stable in adults.