Characterization of Pili Protein 67 kDa Streptococcus pneumoniae: New Candidate for Virulence Factor-Based Pneumococcal Antigen Vaccine

Abstract

Introduction: Streptococcus pneumoniae is a Gram-positive diplococci bacteria that cause infectious diseases such as otitis, meningitis, and pneumonia. Streptococcus pneumoniae has various virulence factors, one of which is pilus. In addition to being immunogenic, pilus S. pneumoniae also plays a role in bacterial adhesion to host cells and biofilm formation. The S. pneumoniae pilus found in this study consisted of several proteins with various molecular weights, one of which was a 67 kDa protein. Objective: This study aimed to determine the characteristics of the 67 kDa pilus protein, including Its ability as hemagglutinin and adhesin and its amino acid composition (AA). Methods: The LCMS/MS method is used to determine the AA composition of the 67 kDa pilus protein. The AA structure was analyzed through BLASTP by matching it with the sequence of the protein data bank of S. pneumoniae (taxid: 1313). The Protparam tool from ExPASy is used to calculate various physical and chemical parameters of the protein, while for evaluating its immunogenicity, it uses the VaxiJen V2.0 online server. Results: The results of this study indicate that the 67 kDa pilus protein is an anti-hemagglutinin protein and has a role as an adhesin protein. Adhesion tests show the action between protein concentration and the number of bacteria attached to enterocyte cells. LCMS/MS test results continued by BLASTP showed that the 67 kDa pilus protein had three AA sequences (ITYMSPDFAAPTLAGLDDATK, AEFVEVTK, and LVVSTQTALA), which had similarities with the A backbone chain of S. pneumoniae pilus. The physicochemical test shows that the protein is hydrophilic and nonpolar, while the antigenicity test shows that the protein is antigenic. Conclusion: Based on these characteristics, it can be concluded that the 67 kDa S. pneumoniae pilus protein can be used as a vaccine candidate for pneumococcus.