Iron-oxide nanoparticles (SPIONs) enhance malaria vaccine antibody response

Protein-subunit malaria vaccines typically elicit only modest and short-lived antibody responses without an effective delivery system. To address this limitation, carboxylated superparamagnetic iron-oxide nanoparticles (Fe₃O₄-COOH SPIONs) has been assessed as a carrier for the recombinant 19-kDa C-terminal fragment of Plasmodium falciparum merozoite surface protein-1 (PfMSP-1). Process began by synthesizing and functionalizing the SPIONs, followed by the conjugation of PfMSP-1 to the nanoparticle surface, and quantification of the antigen loading. BALB/c mice (n = 8/group) received one of four regimens by subcutaneous injection: SPIONs without antigen (control), soluble PfMSP-1 (25 μg) on days 0/21/42, SPION-PfMSP-1 single dose (0.25 mg SPIONs +25 μg antigen on day 0), or SPION-PfMSP-1 on days 0/21/42 with the same per-dose amounts. Serum was then collected at serial time points after priming for ELISA analysis. As expected, SPIONs alone failed to induce detectable PfMSP-1-specific IgG, and the soluble antigen, even after three doses, produced only moderate titers. In stark contrast, the SPION-bound antigen significantly enhanced the humoral responses. A single dose of SPION-PfMSP-1generated a IgG response that was delayed but steadily rising, consistent with sustained antigen availability. Most notably, the three-dose SPION-PfMSP-1schedule resulted in the highest and most durable titers throughout the observation period. Collectively, these data demonstrate that Fe₃O₄-COOH SPIONs notably improve the magnitude and longevity of anti-PfMSP-1 antibodies relative to the soluble protein. This finding strongly supports the use of SPIONs as a practical and effective vaccine-delivery platform for blood-stage malaria antigens, potentially enabling both dose-sparing and flexible scheduling.