Reverse vaccinology approach for the design of a transmission-blocking vaccine by targeting the malaria vector Anopheles

Abstract

According to the latest update from WHO, approximately 263 million cases of malaria were reported globally. The mosquito species Anopheles gambiae is the primary vector transmitting the malaria-causing pathogen Plasmodium spp. Scientists have recently focused on developing a transmission-blocking vaccine (TBV) to combat malaria by targeting vector homeostasis rather than specific Plasmodium species, which vary in their genomes and drug susceptibilities. To create this TBV, three salivary proteins (gSG6, D7, and AgTRIO) were selected as potential antigens. From these proteins, epitopes recognized by cytotoxic T cells (18), helper T cells (30), and B cells (10) were selected. These potentially positive antigens were then combined with mycobacterial tuberculosis heparin-binding hemagglutinin using suitable peptide linkers. The resulting vaccine sequence underwent prediction of biochemical properties and secondary and tertiary structure. The best model was generated using the I-TASSER platform, refined, validated, and docked to Toll-like receptor-4 (TLR-4) via the InterEvDock 2 server. The consensus docked complex demonstrated stability, mobility, and flexibility, as assessed through the Internal Coordinates Normal Mode Analysis Server and Groningen Machine for Chemical Simulations dynamics simulations. Furthermore, the vaccine exhibited a well-defined three-dimensional structure and strong binding to TLR-4 through multiple bonds. Molecular mechanics/generalized Born surface area yielded a ΔG of −28.5 kcal mol−1; however, stable binding was not achieved during the 100 ns molecular dynamics simulation, as indicated by a root mean square deviation of 1.25 nm. Following in silico simulation of vaccination, the vaccine was predicted to significantly induce robust B-cell and T-cell responses, antibody production (both IgM and IgG), and interferon-γ secretion. Importantly, this multi-epitope malaria TBV demonstrated predicted immunogenic potency without evidence of allergenicity or toxicity, suggesting its potential to limit the transmission of multidrug-resistant Plasmodium strains. However, these computational predictions require validation through in vitro and in vivo studies.