10-year longitudinal study of malaria in children: Insights into acquisition and maintenance of naturally acquired immunity
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Date
2022
Journal Title
Journal ISSN
Volume Title
Publisher
Wellcome Open Research
Abstract
Studies of long-term malaria cohorts have provided
essential insights into how Plasmodium falciparum interacts with
humans, and influences the development of antimalarial immunity.
Immunity to malaria is acquired gradually after multiple infections,
some of which present with clinical symptoms. However, there is
considerable variation in the number of clinical episodes experienced
by children of the same age within the same cohort. Understanding
this variation in clinical symptoms and how it relates to the
development of naturally acquired immunity is crucial in identifying
how and when some children stop experiencing further malaria
episodes. Where variability in clinical episodes may result from
different rates of acquisition of immunity, or from variable exposure
to the parasite.
Methods: Using data from a longitudinal cohort of children residing in
an area of moderate P. falciparum transmission in Kilifi district, Kenya,
we fitted cumulative episode curves as monotonic-increasing splines, to 56 children under surveillance for malaria from the age of 5 to 15.
Results: There was large variability in the accumulation of numbers of
clinical malaria episodes experienced by the children, despite being of
similar age and living in the same general location. One group of
children from a particular sub-region of the cohort stopped
accumulating clinical malaria episodes earlier than other children in
the study. Despite lack of further clinical episodes of malaria, these
children had higher asymptomatic parasite densities and higher
antibody titres to a panel of P. falciparum blood-stage antigens.
Conclusions: This suggests development of clinical immunity rather
than lack of exposure to the parasite, and supports the view that this
immunity to malaria disease is maintained by a greater exposure to P.
falciparum, and thus higher parasite burdens. Our study illustrates the
complexity of anti-malaria immunity and underscores the need for
analyses which can sufficiently reflect the heterogeneity within
endemic populations.
Description
Research Article
Keywords
Plasmodium falciparum, Clinical Malaria, Protective Immunity, Longitudinal Cohorts, Growth Curves