RT Journal Article SR Electronic T1 Acquired Immune Responses to Plasmodium falciparum Merozoite Surface Protein-1 in the Human Fetus JF The Journal of Immunology JO J. Immunol. FD American Association of Immunologists SP 356 OP 364 DO 10.4049/jimmunol.168.1.356 VO 168 IS 1 A1 King, Christopher L. A1 Malhotra, Indu A1 Wamachi, Alex A1 Kioko, John A1 Mungai, Peter A1 Wahab, Sherif Abdel A1 Koech, Davy A1 Zimmerman, Peter A1 Ouma, John A1 Kazura, James W. YR 2002 UL http://www.jimmunol.org/content/168/1/356.abstract AB Infants born in areas of stable malaria transmission are relatively protected against severe morbidity and high density Plasmodium falciparum blood-stage infection. This protection may involve prenatal sensitization and immunologic reactivity to malaria surface ligands that participate in invasion of red cells. We examined cord blood T and B cell immunity to P. falciparum merozoite surface protein-1 (MSP-1) in infants born in an area of stable malaria transmission in Kenya. T cell cytokine responses to the C-terminal 19-kDa fragment of MSP-1 (MSP-119) were detected in 24 of 92 (26%) newborns (4–192 IFN-γ and 3–88 IL-4-secreting cells per 106/cord blood lymphocytes). Peptide epitopes in the N-terminal block 3 region of MSP-1 also drove IFN-γ and/or IL-13 production. There was no evidence of prenatal T cell sensitization to liver-stage Ag-1. A total of 5 of 86 (6%) newborns had cord blood anti-MSP-119 IgM Abs, an Ig isotype that does not cross the placenta and is therefore of fetal origin. The frequency of neonatal B cell sensitization was higher than that indicated by serology alone, as 5 of 27 (18%) cord blood samples contained B cells that produced IgG when stimulated with MSP-119 in vitro. Neonatal B cell IgG responses were restricted to the Q-KNG allele of MSP-119, the major variant in this endemic area, whereas T cells responded to all four MSP-119 alleles evaluated. In utero sensitization to MSP-1 correlated with the presence of malaria parasites in cord blood (χ2 = 20, p < 0.0001). These data indicate that prenatal sensitization to blood-stage Ags occurs in infants born in malaria endemic areas.