Evaluation of Toxoplasma gondii Perforin-like Proteins (PLPs) to Find the Potential Epitopes for Immunization through in silico Approach

Background: Toxoplasma gondii (T. gondii) is a widespread apicomplexan parasite that affects approximately one-third of the global population, posing particular risks to pregnant women and individuals with weakened immune systems. Despite its significant impact, there is currently no vaccine available for humans. Objective: This study employs computational methods (in silico) to investigate the physicochemical, antigenic, and structural properties of Perforin-like proteins (PLPs) from T. gondii, as well as to identify immunogenic epitopes within these antigens. Methods: For this aim, amino acid sequences of TgPLP1 and TgPLP2 were retrieved and submitted to the ProtParam (physicochemical), VaxiJen v2.0 (antigenicity), NetSurfP-6.0 (2D structure), Robetta (3D structure) web servers, along with the IEDB server to decipher the immunogenic epitopes. Subcellular characteristics such as signal peptide, transmembrane domain, post-translational modifications (PTMs), and cellular localization were also predicted. Results: Both proteins had a high MW of 125.50 and 92.21, respectively, with an alkaline pI, a 30 hours half-life in mammalian reticulocytes, good thermotolerance (high aliphatic index), and hydrophilicity properties (negative GRAVY). They also showed good antigenicity (0.7021 [PLP1] vs 0.5701 [PLP2]), while they were non-allergenic. Both proteins were extracellular with numerous post-translational modification sites (phosphorylation, glycosylation, and acetylation), and a transmembrane domain was only present in TgPLP1, with no signal peptide in both. Furthermore, numerous immunogenic B- and T-cell epitopes were identified within the TgPLPs sequences, suggesting their potential for inclusion in multi-epitope vaccine designs. Conclusion: Further studies are needed to confirm these findings and assess the efficacy of the proposed vaccine constructs.