High Avidity Antibodies to VAR2CSA were Associated with Absence of Placental Malaria in Ngali II.

<p>(<b>a</b>) The proportion (%) of Ab that remains bound to FV2 after incubation with 3M NH₄SCN (i.e., % high avidity Ab) in the plasma of primigravidae and multigravidae living in Ngali II is shown. Results represent the mean + SEM for 11 to 51 data points per bar. Throughout the course of pregnancy, the proportion of high avidity Ab to FV2 was higher in multigravid than primigravid women (p<0.0001; multilevel polynomial regression analysis). (<b>b</b>) The scattergram shows that the proportion of high avidity Ab to FV2 was highly variable. However, the proportion (%) of high avidity Ab in plasma of women who were PM⁻ was significantly higher than in plasma of PM⁺ women during pregnancy (PM⁻, n = 13; PM⁺, n = 14) (p = 0.0009), based on multilevel polynomial regression analysis. (<b>c</b>) A significantly higher proportion of high avidity Ab was present in plasma of PM⁻ women than PM⁺ women at 5–6 months (p<0.0001), but not at 3–4 and 7–8 months.</p

Characteristics of women followed longitudinally

<p>a mean ± SD.</p><p>b samples were selected from women who were slide and/or PCR-positive at least once during pregnancy confirming that women had become infected.</p

Correlation between Antibody Levels to VAR2CSA and Placental Malaria at Delivery.

<p>Anti-FV2 Ab levels (MFI ± SEM) were determined between 3 to 9 months of pregnancy in women in Ngali II (<b>a</b>) and Yaoundé (<b>b</b>) with known placental malaria status (Ngali II: PM⁻ n = 13, PM⁺ n = 14; Yaoundé: PM⁻ n = 10, PM⁺ n = 15). (a) A significant difference between PM⁻ and PM⁺ women in Ngali II was found throughout pregnancy using multilevel polynomial regression analysis (p = 0.0047). (<b>b</b>) PM⁻ women in Yaoundé also had higher mean Ab levels compared to PM⁺ women, although difference was not significant. (<b>c–d</b>) Data from PM⁻ and PM⁺ women were subdivided into primigravidae (PG) and multigravidae (MG). All PG in Ngali II and Yaoundé were PM⁺ at delivery, explaining why there are only 3 groups in the figures. Similar Ab levels were present in placental PM⁺ PG and PM⁺ MG. (<b>e</b>) The same plasma samples from PM⁻ and PM⁺ women in Ngali II collected at 4 to 7 months were tested for surface binding to CSA-binding IE (7G8 strain). In support of the results in Fig. 2a, higher levels of Ab was detected in women in Ngali II who were PM⁻ compared to those who were PM⁺ (p = 0.05). P values are based on multilevel polynomial regression analysis. Abbreviations: FV2, full-length VAR2CSA; PM⁻, placental malaria-negative; PM⁺, placental malaria-positive; PG, primigravidae; MG, multigravidae.</p