In Silico Analysis of L1/L2 Sequences of Human Papillomaviruses: Implication for Universal Vaccine Design

The aim of this study was to design a multiepitope universal vaccine for major human papillomavirus (HPV) structural proteins, L1/L2, by bioinformatics models. For this purpose, we predicted the most probable immunogenic epitopes of L1 and L2 from common high-risk HPV 16, 18, 31, and 45 beside high prevalent type 6 and 11 based on BCPREDS defaulted model, while solvent accessibility of structure was extrapolated. The three-dimensional molecular model of L1 protein was constructed by Swiss Model server, whereas sequence alignment provided model for prediction of L2 protein epitopes. After that, N-glycosylation sites were excluded from estimated epitope regions. Then, by other bioinformatics analyses, 20 epitopes were selected and fused in tandem repeats, reverse translated, and codon optimized to relevant sequence. The final protein parameters such as antigenicity were analyzed by protean program. Evaluation of new recombinant protein sequence indicated a molecular weight of 41.8 kDa with 400 amino acids beside positive charge. The computed isoelectric point (pI) value indicated the acidic nature of final product. The aliphatic index showed low thermal stability of this construct and the Grand Average Hydropathicity value was negative (-0.494). Analyzed plot showed that major parts of new protein construct had hydrophilic property, thus harboring antigenic potency. After all, sequence of final construct reverse translated to DNA and this codon-optimized sequence showed Codon Adaptation Index (CAI) of >0.8 for expression in Escherichia coli. Finally, this sequence ligated into pET28a bacterial expression vector. The new recombinant proteins harboring 20 B cell epitope seem to be suitable antigens based on computational methods as a universal vaccine candidate for HPVs.