Antibody levels to recombinant VAR2CSA domains vary with Plasmodium falciparum parasitaemia, gestational age, and gravidity, but do not predict pregnancy outcomes

Abstract

Background: Maternal malaria is a tropical scourge associated with poor pregnancy outcomes. Women become resistant to Plasmodium falciparum pregnancy malaria as they acquire antibodies to the variant surface antigen VAR2CSA, a leading vaccine candidate. Because malaria infection may increase VAR2CSA antibody levels and thereby confound analyses of immune protection, gravidity-dependent changes in antibody levels during and after infection, and the effect of VAR2CSA antibodies on pregnancy outcomes were evaluated.

Methods: Pregnant women enrolled in a longitudinal cohort study of mother-infant pairs in Ouelessebougou, Mali provided plasma samples at enrollment, gestational week 30-32, and delivery. Antibody levels to VAR2CSA domains were measured using a multiplex bead-based assay.

Results: Antibody levels to VAR2CSA were higher in multigravidae than primigravidae. Malaria infection was associated with increased antibody levels to VAR2CSA domains. In primigravidae but not in secundigravidae or multigravidae, antibodies levels sharply declined after an infection. A relationship between any VAR2CSA antibody specificity and protection from adverse pregnancy outcomes was not detected.

Conclusions: During malaria infection, primigravidae acquire short-lived antibodies. The lack of an association between VAR2CSA domain antibody reactivity and improved pregnancy outcomes suggests that the recombinant proteins may not present native epitopes targeted by protective antibodies.

Keywords: Anaemia; Birth weight; Placental malaria; Pregnancy loss; Preterm delivery; VAR2CSA.

Fig. 1

Antibody levels to VAR2CSA domains stratified by gravidity. Levels at enrollment (a), gestational week 30–32 (b), and delivery (c) among primigravid (P, brown boxes), secundigravid (S, blue boxes) and multigravid (M, red boxes) women. Numbers that follow indicate the number of samples at enrollment, gestational week 30–32 and delivery in each gravid group: primigravidae (n = 157, 109, 152); secundigravidae (n = 118, 83, 114); multigravidae (n = 328, 245, 324). Significant differences between primigravidae and multigravidae are indicated with †, between primigravidae and secundigravidae with *, and between secundigravidae and multigravidae are indicated with §. The results are expressed as median fluorescent intensity (MFI). Box plot indicates the median (horizontal line) and interquartile range (box), the whiskers indicate the 10th and 90th percentiles

Fig. 2

Antibody levels to VAR2CSA domains in malaria infected (grey boxes) and uninfected women (open boxes) at enrollment in primigravid (a, d), secundigravid (b, e) and multigravid (c, f) women. Infections detected by blood smear microscopy are shown in a–c, and submicroscopic infections detected by PCR in d–f. Numbers that follow indicate the number of samples with positive blood smear or positive by PCR and with no infection in each gravid group: primigravidae (a n = 63, 94; d n = 18, 73); secundigravidae (b n = 29, 89; e n = 19, 62); multigravidae (c n = 50, 278; f n = 65, 190). Significant differences in antibody levels in malaria-infected women versus uninfected indicated by an asterisk. The results are expressed as median fluorescent intensity (MFI). Box plot indicates the median (horizontal line) and interquartile range (box), the whiskers indicate the 10th and 90th percentiles

Fig. 3

Antibody levels to VAR2CSA domains expressed as mean antibody levels to 11 domains at enrollment (E, light shade) and at delivery (D, dark shade) in women with no infections during the study and women infected at enrollment only. Numbers that follow indicate the number of samples with no infection or infection at enrollment only at enrollment (E) and at delivery (D) in each gravid group: primigravidae (E, n = 66, 48; D, n = 64, 46); secundigravidae (E, n = 64, 22; D, n = 57, 23); multigravidae (E, n = 212, 38; D, n = 204, 40). Box plot indicates the median (horizontal line) and interquartile range (box), the whiskers indicate the 10th and 90th percentiles