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Open Access Highly Accessed Research

Foetal haemoglobin and the dynamics of paediatric malaria

Erica MW Billig1*, Philip G McQueen2 and F Ellis McKenzie1

Author Affiliations

1 National Institutes of Health, Fogarty International Center, Building 16, Room 303, Bethesda, MD, 20892, USA

2 National Institutes of Health, Center for Information Technology, 12 South Drive, Bethesda, MD, 20892, USA

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Malaria Journal 2012, 11:396  doi:10.1186/1475-2875-11-396

Published: 28 November 2012

Abstract

Background

Although 80% of malaria occurs in children under five years of age, infants under six months of age are known to have low rates of infection and disease. It is not clear why this youngest age group is protected; possible factors include maternal antibodies, unique nutrition (breast milk), and the presence of foetal haemoglobin (HbF). This work aims to gain insight into possible mechanisms of protection, and suggest pathways for focused empirical work, by modelling a range of possible effects of foetal haemoglobin and other red blood cell (RBC) developmental changes on parasite dynamics in infants.

Methods

A set of ordinary differential equations was created to investigate the leading hypotheses about the possible protective mechanisms of HbF-containing red blood cells, in particular whether HbF suppresses parasite population growth because parasite multiplication in individual RBCs is lower, slower or absent. The model also incorporated the intrinsic changes in blood volume and haematocrit that occur with age, and the possibility of parasite affinities for HbF-containing RBCs or reticulocytes.

Results

The model identified several sets of conditions in which the infant remained protected, or displayed a much slower growth of parasitaemia in the first few months of life, without any intervening immune response. The most protective of the hypothesized mechanisms would be the inhibition of schizont division in foetal RBCs so that fewer merozoites are produced. The model showed that a parasite preference for HbF-containing RBCs increases protective effects for the host, while a preference for reticulocytes has little effect.

Conclusions

The results from this simple model of haematological changes in infants and their effects on Plasmodium falciparum infection dynamics emphasize the likely importance of HbF and RBC number as an explanatory factor in paediatric malaria, and suggest a framework for organizing related empirical research.

Keywords:
Malaria; Plasmodium falciparum; Foetal haemoglobin