DiagnosticsPrenatal Malaria Exposure Increases Risk Of Malaria And Anemia For Some Children
Some babies who are exposed to malaria before birth develop a tolerant
phenotype that increases their susceptibility to malaria and anemia in
childhood, says a new study in the open access journal PLoS Medicine. Indu
Malhotra and Christopher King (Case Western Reserve University) and
colleagues studied 586 newborns residing in a malaria-holoendemic area of
Kenya to age three, assessing their malaria infection, malaria-specific
immune responses, and anemia, and classifying them into three groups:
"sensitized" babies in which cord blood cells made activating cytokines in
response to malaria antigens; "exposed, not-sensitized" babies in which
cord blood cells did not make activating cytokines but made an inhibitory
cytokine (IL-10); and "not-exposed" babies born to uninfected mothers.
The authors report that in the first 3 years of life, the exposed,
not-sensitized newborns had a 60% greater risk of malaria infection than
the
unexposed group and a slightly higher risk of malaria infection than the
sensitized group. They also had lower hemoglobulin levels, a sign of
anemia,
than the other babies. At 6 months, the T-cells of exposed, not-sensitized
children were less likely to make activating cytokines in response to
malaria antigens but made more IL-10 than the T-cells of the other
children; malaria-specific antibody levels were similar in the three
groups, say
the authors.
Why some children exposed to malaria before birth become tolerant to the
disease while exposure to malaria antigens "primes" the immune system of
other children to respond efficiently to malaria antigens is not clear.
However, these findings could have important implications for the design
of
malaria vaccines for use in areas where children are often exposed to
malaria before birth and for the design of strategies for the prevention
of
malaria during pregnancy, say the authors.
"Once the significance of fetal malaria experience is better understood,"
the authors say, "it should translate into more effective strategies
for malaria chemoprophylaxis during pregnancy."
In a related Perspective on the study, Lars Hviid (not involved in the
research) states that the research by Dr. King and colleagues "adds
significantly to our understanding of prenatal exposure to P. falciparum
antigens" and has "obvious clinical importance." But he outlines
several areas for further investigation of pregnancy-associated malaria.
Funding:
The work was supported in part by United States Public Health
Service grants I064687, AI054711, MH080601, AI065717 and Veterans" Affairs
Research Service. The funders had no role in the study design, data
collection, analysis, decision to publish or preparation of the
manuscript. They
did contribute to the design of the study.
Competing Interests:
David Narum has declared the following competing
interest: ""Narum et al., United States Patent 7,078,507 for production of
recombinant EBA-175 RII protein.""
Citation:
"Can Prenatal Malaria Exposure Produce an Immune Tolerant Phenotype?: A Prospective Birth Cohort Study in Kenya."
Malhotra I, Dent A, Mungai P, Wamachi A, Ouma JH, et al. (2009)
PLoS Med 6(7): e1000116. doi:10.1371/journal.pmed.1000116
PLoS Medicine