In silico Analysis of Toxoplasma gondii Surface and Secretory Proteins for the Design of a Novel Chimeric Vaccine

Background This study focuses on the Toxoplasma gondii ( T. gondii ) antigens ROP18, SAG1, and MIC13, which play key roles in pathogenesis, immune evasion, and host invasion. The aim was to design a novel chimeric antigen combining these proteins as a potential vaccine candidate against T. gondii . Methods Fragments of ROP18 (Q101–E300), SAG1 (P61–G160), and MIC13 (D171–R320) were linked using a rigid A(EAAAK)A linker. Bioinformatics analyses predicted various properties of the chimeric protein RSM1, including transmembrane domains, B- and T-cell epitopes, secondary and tertiary structures, antigenicity, physicochemical traits, codon optimization, and mRNA structure. Results RSM1 consists of 485 amino acids and has an antigenicity score of 0.6694. The aliphatic index, instability index, and GRAVY score were 68.66, 54.19, and –0.639, respectively. Structural predictions supported RSM1’s potential as a vaccine candidate. The most stable tertiary structure had a ΔG of –524.80 kcal/mol, with no stable hairpins or pseudoknots at the mRNA 5′ end, suggesting favorable translation. Discussion The bioinformatics analyses indicate that RSM1 possesses favorable antigenic and structural properties, supporting its potential as a multi-epitope vaccine candidate. Its predicted stability and translation efficiency suggest practical viability, although the moderate instability index points to the need for further optimization. Conclusion RSM1 represents a promising in silico -designed vaccine candidate against T. gondii . This study lays the groundwork for subsequent experimental evaluations to determine its immunogenicity and protective efficacy in vivo .