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Acquired immunity and postnatal clinical protection in childhood cerebral malaria
S Gupta1, R W Snow, C Donnelly
1Wellcome Trust Centre for Epidemiology of Infectious Disease, Department of Zoology, University of Oxford, UK.
Abstract:
By analysing data on the age distribution of cerebral malaria among sites of different transmission intensities, we conclude that the most plausible explanation for the epidemiological patterns seen is that (i) cerebral malaria is caused by a distinct set of Plasmodium falciparum antigenic types; (ii) these antigenic types or 'CM strains' are very common and induce strong strain-specific immunity; and (iii) the postnatal period of protection against cerebral malaria is much longer than the period of protection against other forms of severe disease. The alternative hypothesis that cerebral malaria may be caused by any 'strain' of P. falciparum is compatible with the data only if a single exposure is sufficient to protect against further episodes. This is not consistent with observations on the history of exposure of patients with cerebral malaria. Finally, it is clear that although the delayed peak in incidence of cerebral malaria (with age) can be generated by assuming that subsequent exposures carry a higher risk of disease, such an explanation is not compatible with the observation that severe disease rates are low among infants and young children in areas of high transmissibility.
Insights
Cerebral malaria is likely caused by specific Plasmodium falciparum strains that induce long-lasting immunity. This explains age-related disease patterns and protection observed in high-transmission areas.
Area of Science:
- Malariology
- Immunology
- Epidemiology
Background:
- Cerebral malaria (CM) is a severe Plasmodium falciparum complication.
- Epidemiological patterns of CM vary with transmission intensity and age.
- Understanding CM pathogenesis is crucial for effective control.
Purpose of the Study:
- To analyze age distribution of CM across different transmission intensities.
- To identify the most plausible explanation for observed CM epidemiological patterns.
- To evaluate hypotheses regarding Plasmodium falciparum strains and immunity in CM.
Main Methods:
- Analysis of age-specific incidence data for cerebral malaria.
- Comparison of epidemiological patterns at sites with varying malaria transmission intensities.
- Evaluation of hypotheses on Plasmodium falciparum antigenic types and strain-specific immunity.
Main Results:
- Cerebral malaria is associated with distinct Plasmodium falciparum antigenic types ('CM strains').
- These CM strains are common, induce strong strain-specific immunity, and confer long-lasting protection.
- Alternative hypotheses, including universal strain risk or solely exposure-dependent risk, are less compatible with observed data.
Conclusions:
- A distinct set of Plasmodium falciparum antigenic types likely causes cerebral malaria.
- Long-lasting, strain-specific immunity against CM is induced by these specific antigenic types.
- The findings explain the age-related incidence and protection patterns observed in different malaria-endemic settings.