Conserved B-cell epitopes among human bocavirus species indicate potential diagnostic targets.
BACKGROUND
Human bocavirus species 1-4 (HBoV1-4) have been associated with respiratory and enteric infections in children. However, the immunological mechanisms in response to HBoV infections are not fully understood. Though previous studies have shown cross-reactivities between HBoV species, the epitopes responsible for this phenomenon remain unknown. In this study, we used genomic and immunologic approaches to identify the reactive epitopes conserved across multiple HBoV species and explored their potential as the basis of a novel diagnostic test for HBoVs.


RESULTS
We generated HBoV1-3 VP2 gene fragment phage display libraries (GFPDLs) and used these libraries to analyze mouse antisera against VP2 protein of HBoV1, 2, and 3, and human sera positive for HBoVs. Using this approach, we mapped four epitope clusters of HBoVs and identified two immunodominant peptides--P1 (¹MSDTDIQDQQPDTVDAPQNT²⁰), and P2 (¹⁶²EHAYPNASHPWDEDVMPDL¹⁸⁰)--that are conserved among HBoV1-4. To confirm epitope immunogenicity, we immunized mice with the immunodominant P1 and P2 peptides identified in our screen and found that they elicited high titer antibodies in mice. These two antibodies could only recognize the VP2 of HBoV 1-4 in Western blot assays, rather than those of the two other parvoviruses human parvovirus B19 and human parvovirus 4 (PARV4). Based on our findings, we evaluated epitope-based peptide-IgM ELISAs as potential diagnostic tools for HBoVs IgM antibodies. We found that the P1+P2-IgM ELISA showed a higher sensitivity and specificity in HBoVs IgM detection than the assays using a single peptide.


CONCLUSIONS
The identification of the conserved B-cell epitopes among human bocavirus species contributes to our understanding of immunological cross-reactivities of HBoVs, and provides important insights for the development of HBoV diagnostic tools.
MOH Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB, CAMS-Fondation Mérieux, Institute of Pathogen Biology (IPB), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
Zhuo
Z
Zhou
MOH Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB, CAMS-Fondation Mérieux, Institute of Pathogen Biology (IPB), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
Xin
X
Gao
MOH Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB, CAMS-Fondation Mérieux, Institute of Pathogen Biology (IPB), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
Yaying
Y
Wang
MOH Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB, CAMS-Fondation Mérieux, Institute of Pathogen Biology (IPB), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
Hongli
H
Zhou
MOH Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB, CAMS-Fondation Mérieux, Institute of Pathogen Biology (IPB), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
Chao
C
Wu
Fondation Mérieux, Lyon, France.
Gláucia
G
Paranhos-Baccalà
Fondation Mérieux, Lyon, France.
Guy
G
Vernet
MOH Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB, CAMS-Fondation Mérieux, Institute of Pathogen Biology (IPB), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
Li
L
Guo
MOH Key Laboratory of Systems Biology of Pathogens and Christophe Mérieux Laboratory, IPB, CAMS-Fondation Mérieux, Institute of Pathogen Biology (IPB), Chinese Academy of Medical Sciences (CAMS) & Peking Union Medical College (PUMC), Beijing, People's Republic of China.
Jianwei
J
Wang
D000595:Amino Acid Sequence; D000818:Animals; D015153:Blotting, Western; D017124:Conserved Sequence / Q000235:genetics*; D004797:Enzyme-Linked Immunosorbent Assay; D018985:Epitopes, B-Lymphocyte / Q000235:genetics*; D056661:Human bocavirus / Q000235:genetics*; D006801:Humans; D051379:Mice; D008969:Molecular Sequence Data; D010322:Parvoviridae Infections / Q000175:diagnosis*; D013045:Species Specificity
D018985:Epitopes, B-Lymphocyte