Comparative Molecular Analysis and Antigenicity Prediction of an Outer Membrane Protein (ompC) of Non-typhoidal Salmonella Serovars Isolated from Different Food Animals in Lagos, Nigeria

Abstract

Non-typhoidal Salmonella (NTS) infections occur globally with high morbidity and mortality. The public health challenge caused is exacerbated by increasing rate of antibiotic resistance and absence of NTS vaccine. In this study, we characterized the outer membrane protein C ( OmpC) serovars isolated from different food animals and predicted antigenicity. ompC of 27 NTS serovars were amplified by polymerase chain reaction (PCR) and sequenced. Sequence data were analysed and B-cell epitope prediction was done by BepiPred tool. T-cell epitope prediction was done by determining peptide-binding affinities of major histocompatibility complex (MHC) classes I and II using NetMHC pan 2.8 and NetMHC-II pan 3.2, respectively. ompC sequence analysis revealed conserved region among ompCs of Salmonella Serovars. A total of 66.7% of ompCs were stable with instability index value < 40 and molecular weight that ranged from 27 745.47 to 32 714.32 kDa. All ompCs were thermostable and hydrophilic with the exception of S. Pomona (14p) isolate that had ompC with GRAVY value of 0.028 making it hydrophobic. Linear B-cell epitope prediction revealed ability of ompC to elicit humoral immunity. Multiple B-cell epitopes that were exposed and buried were observed on several positions on the ompC sequences. T-cell epitope prediction revealed epitopes with strong binding affinity to MHC–I and -II. Strong binding to human leukocyte antigen (HLA-A) ligands, including HLA-A03:1, HLA-A24:02 and HLA-A26:01 in the case of MHC-I were observed. While binding affinity to H-2 IAs, H-2 IAq and H-2 IAu (H-2 mouse molecules) were strongest in the case of MHC-II. ompCs of NTS serovars isolated from different food animal sources indicated ability to elicit humoral and cell-mediated immunity. Hence, ompCs of NTS serovars are potential candidate for production of NTS vaccines.