# Porcine Parvovirus 7: Evolutionary Dynamics and Identification of Epitopes toward Vaccine Design
## 3 Results
### Sequence and Structural Characteristics  
Sequence alignments revealed that PPV7 genomes (total 45 of isolates deposited in GenBank) exhibited 91.9-100% nucleotide homology. Furthermore, PPV7 \(NS1\) and \(Cap\) genes (total 59 of each deposited in GenBank) had 92.8-100% and 85.7-100% homology, respectively, and the derived amino acid sequence of both proteins shared 89.9-100% and 82.4-100% identity, respectively. The Ca\({}^{2+}\) binding loop (YXGXG) was present in the Caps of PPV1, PPV2, PPV3 and PPV5 [1,10], and \"YXGXR\" was in PPV6 [11], but absent in PPV4. However, the potential Ca\({}^{2+}\) binding loop was the \({}^{267}\)YXGXG\({}^{272}\) motif in PPV7, and \"\({}^{269}\)GXX\({}^{271}\)\" (\"\({}^{269}\)GP\({}^{271}\)\") were strictly conserved in PPV7 (Figure 3). Furthermore, compared to the catalytic motif (HDXXY) of the putative secretory phospholipase A2 (PLA2) in PPV5 [10], a similar motif \({}^{300}\)HDXXN\({}^{304}\) was present in PPV7, whereas a point mutation occurred at position 304 (N 304 Y) in the 59 of PPV7 Cap proteins (Figure 3). \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & **FEL** & \multicolumn{3}{c}{**SLAC**} & \multicolumn{3}{c}{**FUBAR**} & \multicolumn{3}{c}{**MEME**} \\ \hline
**Site** & **dN-dS** & \(p\)**-Value** & **Site** & **dN-dS** & \(p\)**-Value** & **Site** & **dN-dS** & **Post.Pro** & **Site** & **\(\beta^{*}\)** & \(p\)**-Value** \\ \hline
24 & 2.492 & 0.004 & 24 & 5.741 & 0.018 & 24 & 6.900 & 0.997 & 24 & 2.5 & 0.01 \\
106 & 2.157 & 0.023 & 106 & 4.943 & 0.028 & 106 & 5.706 & 0.979 & 106 & 24.21 & 0 \\
158 & 1.552 & 0.033 & 158 & 3.652 & 0.098 & 158 & 3.244 & 0.972 & 158 & 1.55 & 0.05 \\
270 & 1.777 & 0.026 & 270 & 5.107 & 0.048 & 270 & 4.363 & 0.974 & 270 & 14.87 & 0 \\
446 & 1.649 & 0.015 & 446 & 3.970 & 0.055 & 441 & 2.926 & 0.944 & 441 & 18.72 & 0 \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Selection analysis of PPV7 Cap coding sequences. \begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline  & **FEL** & \multicolumn{3}{c}{**SLAC**} & \multicolumn{3}{c}{**FUBAR**} & \multicolumn{3}{c}{**MEME**} \\ \hline
**Site** & **dN-dS** & \(p\)**-Value** & **Site** & **dN-dS** & \(p\)**-Value** & **Site** & **dN-dS** & **Post.Pro** & **Site** & **\(\beta^{*}\)** & \(p\)**-Value** \\ \hline
24 & 2.492 & 0.004 & 24 & 5.741 & 0.018 & 24 & 6.900 & 0.997 & 24 & 2.5 & 0.01 \\
106 & 2.157 & 0.023 & 106 & 4.943 & 0.028 & 106 & 5.706 & 0.979 & 106 & 24.21 & 0 \\
158 & 1.552 & 0.033 & 158 & 3.652 & 0.098 & 158 & 3.244 & 0.972 & 158 & 1.55 & 0.05 \\
270 & 1.777 & 0.026 & 270 & 5.107 & 0.048 & 270 & 4.363 & 0.974 & 270 & 14.87 & 0 \\
446 & 1.649 & 0.015 & 446 & 3.970 & 0.055 & 446 & 3.901 & 0.988 & 446 & 3.43 & 0.02 \\ \hline \hline \end{tabular}
\end{table} 
Table 2: Selection analysis of PPV7 N1 coding sequences. A representative strain (KU563733) was used for a structural analysis of PPV7 Cap. The physicochemical properties of the PPV7 Cap, computed using the ProtParam tool, concluded that it contained 469 aa, with a molecular weight of 54,257.8 Da. The isoelectric point (PI) of this protein was 7.23, indicating that it is positive in nature. Out of 469 residues, 42 (Asp + Glu) were negatively charged and 42 (Arg + Lys) were positively charged. The instability index of (II) was computed to be 38.58, indicating that it was a stable protein. The predicted aliphatic index was 56.78 and the grand average of hydropathicity (GRAVY) for the protein sequence was \(-\)0.695. This protein contained 7483 atoms, and was described by the formula C2469H3639N647O714S14. The estimated half-life was 30 h (mammalian reticulytes, in vitro), \(>\) 20 h (yeast, in vivo) and \(>\) 10 h (_Escherichia coli_, in vivo). The secondary structure of the PPV7 Cap was analyzed by PSIPRED with (24%) beta sheets, (12%) helixes and (64%) loops present in the structure (Figure S2). Vaxijen v2.0 was used to evaluate the antigenicity of the Cap.