# Porcine Parvovirus 7: Evolutionary Dynamics and Identification of Epitopes toward Vaccine Design
## 4 Discussion
\begin{table}
\begin{tabular}{c c c c c c c c c c} \hline \hline \multirow{2}{*}{**No.**} & \multirow{2}{*}{**Allele**} & \multirow{2}{*}{**Start**} & \multirow{2}{*}{**End**} & \multirow{2}{*}{**Peptide**} & \multicolumn{2}{c}{**Global**} & \multicolumn{2}{c}{**vdW**} & \multicolumn{2}{c}{**H-Bond**} & \multirow{2}{*}{**Interacting**} & \multirow{2}{*}{**Vasien**} & \multirow{2}{*}{**Identify**} \\  & & & & & **Energy** & **Energy** & & **Energy** & & **Residues** & **Score** & **(99 Isolates)** \\ \hline A1 & SLA-2’0402 & 111 & 119 & YETSYTHNWY & \(-26.32\) & \(-2221\) & \(-14.13\) & Arg05, & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ A2 & SLA-2’0402 & 409 & 417 & AFLVITVRY & \(-23.20\) & \(-24.38\) & \(-1.49\) & Arg05, & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ A3 & SLA-2’0402 & 445 & 453 & WNPMMTGTY & \(-54.08\) & \(-30.77\) & \(-31.9\) & Arg07, & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ B1 & SLA-3’0401 & 166 & 174 & TAPENTENTNWY & \(-25.49\) & \(-21.17\) & \(-0.82\) & Arg08, & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ B2 & SLA-3’0401 & 170 & 178 & TNWWTWTWT & \(-37.42\) & \(-22.35\) & \(-41\) & Tyrt84, & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ B3 & SLA-3’0401 & 220 & 228 & RPCKNAMSE & \(-44.82\) & \(-24.06\) & \(-1.49\) & Ser151, & 0.5339 & 91.53\% & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ B4 & SLA-3’0401 & 385 & 393 & KRSSMMFAP & \(-33.28\) & \(-26.27\) & \(-3.37\) & Ser151, & 1.2953 & 100.00\% & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ B5 & SLA-3’0401 & 386 & 394 & KRSSMMFAP & \(-32.49\) & \(-18.96\) & \(-0.51\) & Arg070 & 0.9148 & 100.00\% & \\  & & & & & & & & & & \\  & & & & & & & & & & \\ B6 & SLA-3’0401 & 423 & 431 & RRSWWQARTR & \(-17.93\) & \(-20.24\) & \(-21.7\) & Gln156, & 0.6504 & 76.27\% & \\  & & & & & & & & & & Glu167 & \\ \hline \hline \end{tabular}
\end{table} 
Table 4: Molecular docking results of SLA-2’0402 and SLA-3’0401 with MHC I peptides. were predicted in PPV7 Cap located in loops (Figure S3). However, four of the six epitopes were highly variable in residue compositions (Figure S3), although it was not determined whether these epitopes were located on the capsid surface. We tried to predict the 3D structure of PPV7 Cap, but failed due to low identity (~11.6%) with the template of PPV1 Cap (data not shown). The loops of the PPV1 Cap are generally located on the capsid surface, and these loops were the dominant B cell epitope regions and were considered to be important for viral infection and immunogenicity (Figure S4). Amino acid mutations occurred predominantly in these loops [42], and as PPV1 Cap loops are generally located on the capsid surface, these amino acid mutations may influence receptor binding or antigenicity. Thus, high variations of the epitopes located in PPV7 Cap loops may influence receptor binding or antigenicity, if these epitopes are mostly located on the capsid surface; therefore, perhaps PPV7 uses antigenic shift to escape host immune responses. Interestingly, epitope C (IQELMPRKN to IQELRPGKN) had two point mutations (see underlined residues) in isolate PPV7-77, which dramatically decreased the antigenicity score from 0.7908 to 0.2766. Thereafter, the antigenicity of the peptide containing the double-point mutation in isolate PPV7-77 greatly decreased, which may be one of the strategies of this virus to evade the host's immune responses. Of note, epitope E (KRRSRMF) was highly antigenic (antigenicity score = 1.6044) and strictly conserved among all the isolates of PPV7. Therefore, this potential candidate can be used as a dominant antigen for PPV7 serodiagnosis. Additionally, we predicted several potential CD8 T cell epitopes derived from the PPV7 Cap, and identified nine peptides able be docked onto the SLA with high binding affinities.