In Silico Epitope-Based Vaccine Prediction against Fungal Infection Aspergillosis

Abstract

Aspergillus fumigatus is a pathogenic microorganism that causes aspergillosis due to the presence of its allergenic proteins. During the last two years, a few clinical cases have been reported where allergic bronchopulmonary aspergillosis (ABPA) has been detected in COVID-19 patients. The administration of antifungal medicine did not provide satisfactory results. It is a challenging job for medical scientists to protect mankind by designing an epitope-based vaccine against the rare disease aspergillosis. Other than twenty-three allergenic proteins, this microorganism contains an extra-cellular cellulase CelA expansin protein (Afu5g08030), which is allergenic. To design a peptide vaccine against aspergillosis, the identification of B cell and T cell epitopes is state-of-the-art technology. In our latest research, probable T cell and B cell epitopes are predicted. Molecular docking analysis of these predicted epitopes with their receptors is performed. Here, the primary sequence of the expansin protein is extracted and analyzed. Then, its secondary and tertiary structures are predicted using a homology modeling method and validated. Considering the physicochemical properties of this antigenic protein, two short stretches of peptides, namely 80KPQADEDPNASSSSSSS96 and 286DGGKTWQGTTRTS298, are predicted as linear B cell epitopes. Similarly, based on its contacts with the highest number of alleles, the peptide sequence 221LDLFQNAFTQLADVS235 is chosen as the most possible T cell epitope for the protein present in Aspergillus fumigatus with the highest binding energy for MHC II allele HLA-DRB1* 01: 01. Considering the binding energy of the B cell epitope with IgE, the second epitope 286DGGKTWQGTTRTS298 is designated as the most potential epitope of B cells for this protein. Docking studies were performed with the T cell epitope with the human ternary complex of T cell receptor, CD4 receptor, and peptide-MHC II molecule (PDB ID 3T0E) with a binding energy of −192 Kcal/mole. For peptide-based vaccines, the proposed B cell and T cell epitopes may be used against aspergillosis after further experimental analysis.