Polymorphism of B cell epitopes coded with PE/PPE gene family in BCG

Objective To understand the distribution of B cell epitopes coded with PE/PPE gene family in 13 BCG strains and the influence on BCG immunity. Methods Mycobacterium tuberculosis B cell Epitopes was retrieved from Immune Epitope Data for the alignment with sequence of B cell epitopes of proteome of M. tuberculosis strain H37Rv to determine the PE/PPE gene family coding B cell epitopes. Then the alignment between DNA sequence coding epitopes and genomes of 13 BCG strains was conducted, and the coding sequence in BCG genomes was extracted to analyze its distribution and mutation in BCG. Results Six PE/PPE genes encoded 28 B cell epitopes. 21 B cell epitopes were highly conservative in 13 BCG strains, 7 B cell epitopes showed gene mutation in the BCG genomes. All gene variations in B cell epitopes could occur in different formation periods of BCG. Conclusion PE/PPE proteins expressed by the PE/PPE gene family mostly are bacterial surface protein. The gene mutation of B cell epitope in PE/PPE protein family may affect the BCG protection. It should continue to carry out research on BCG genetic characteristics based on B cell epitopes.