Bioinformatic Design of the Secreted form of SAG2 Protein as a Toxoplasma gondii Vaccine Candidate

Toxoplasmosis is one of the most common parasitic infections transmitted between humans and animals, caused by the protozoan Toxoplasma gondii. This organism acts as an obligate intracellular parasite, presenting an active and rapidly proliferating form known as a tachyzoite, in addition to two durable forms: the tissue cyst and the oocyst. Due to the considerable global impact of chronic infections in various host species, especially in humans and domestic animals, creating and producing an effective vaccine for preventing and managing toxoplasmosis is critically essential. The excretory antigens of Toxoplasma gondii play a vital role in vaccine development and diagnostic processes, with the SAG2 antigen being particularly significant. At present, sophisticated bioinformatics tools are utilized to design efficient signal peptides. This research will adopt an in silico approach to evaluating different signal peptides.

The signal peptide sequence was obtained from the Signal Peptide website and Uniprot. Following this, SignalP was utilized to predict the signal peptides and determine the positions of their cleavage sites. The ProtProm tool was then employed to assess the physicochemical characteristics and solubility. Furthermore, ProtCompB was used to forecast the subcellular localization of the fusion protein.

Of the 50 signal peptides analyzed, 49 were excluded based on SignalP criteria. The signal peptide with the highest aliphatic index was HDEA_ECOLI, while TORT_ECOLI exhibited the highest GRAVY value.

Additionally, SAG2, when fused with all signal peptides, was explicitly designed for the Sec pathway, except NAPA_ECOLI, MBHT_ECOLI, CUEO_ECOLI, and OPGD_ECOLI.

An appropriate signal peptide was recognized for the fusion and translocation of SAG2 into the extracellular environment. While additional experimental studies are necessary for conclusive validation.