Antibody reactivity to the VAR2CSA DBL5 domain among pregnant women in Northern Ghana.

backgroundPregnancy-associated malaria (PAM), caused predominantly by Plasmodium falciparum, remains a major contributor to maternal and neonatal morbidity in malaria-endemic regions. Placental sequestration of infected erythrocytes is mediated by the parasite protein VAR2CSA, a leading target for PAM vaccine development. However, extensive antigenic polymorphism within VAR2CSA complicates the identification of broadly protective vaccine candidates. Conserved subdomains such as the Duffy Binding-Like 5 (DBL5) domain may contribute to naturally acquired antibody responses during pregnancy. To assess the specificity of DBL5-directed immunity, hepatitis B virus (HBV)-infected pregnant women were included as a non-malarial infectious comparator group. This study evaluated plasma immunoglobulin G (IgG) reactivity to DBL5 and examined its concordance with antibody reactivity to full-length VAR2CSA among pregnant women in Northern Ghana.

methodsPlasma samples from 156 pregnant women were purposively selected from a cross-sectional antenatal cohort and categorised into P. falciparum-infected (n = 60), HBV-infected (n = 60), and co-infected (n = 36) groups. Recombinant DBL5 was expressed in E. coli, purified, and used in indirect enzyme-linked immunosorbent assays (ELISA) to measure plasma IgG reactivity. A subset of samples was tested in parallel against full-length VAR2CSA to evaluate concordance of antibody responses. Multi-tool immunoinformatics analyses were additionally performed to predict B-cell and T-cell epitopes and estimate population coverage.

resultsPlasma IgG reactivity to DBL5 differed significantly across study groups (p < 0.001), with the highest median optical density (OD450) observed among P. falciparum-infected women (1.54), compared with HBV-infected (0.88) and co-infected participants (1.20). DBL5-specific IgG responses demonstrated a strong positive correlation with reactivity to full-length VAR2CSA (Spearman's ρ = 0.75, p < 0.0001), indicating substantial concordance between recognition of the DBL5 domain and the native placental malaria antigen. Immunoinformatics analyses identified multiple conserved DBL5 regions with strong predicted HLA-binding affinity and broad estimated global population coverage.

conclusionPregnant women exposed to P. falciparum exhibit elevated plasma IgG reactivity to the VAR2CSA DBL5 domain, and these responses closely parallel antibody recognition of full-length VAR2CSA. These findings suggest that DBL5 may represent an immunologically recognisable component of naturally acquired PAM-associated antibody responses. However, given the exploratory cross-sectional design, the observed associations should be interpreted cautiously and warrant further investigation in longitudinal and functional studies evaluating the role of DBL5 in placental malaria immunity and future vaccine research.