HUMAN BOCAVIRUS 1 GENOME ORGANIZATION AND REPLICATION MECHANISM

Abstract

Human bocavirus is a human pathogen that was identified in 2005. For the past decade, most of the studies about this virus were focused on clinical detection and its association-with diseases, while very little was known about the molecular virology. The studies presented in this thesis are composed of three parts: 1) Identification of novel HBoV1 proteins by transfection of an HBoV1 infectious clone or during HBoV1 infection; 2) exploring the interactions between the viral genome and proteins to uncover the details underlying HBoV DNA replication; and 3) providing evidence of HBoV1 hairpin independent DNA replication. In the first study, we identified three new non-structural proteins of human bocavirus 1 during infection of polarized human airway epithelium. Of the three newly identified proteins, we proved that one non-structural protein is critical for virus replication in the polarized human bronchial airway epithelium. The creation of a non-replicating infectious HBoV1 mutant may have particular utility in vaccine development for this virus. In the second study, we identified both cis- and trans-acting proteins that are required for HBoV1 DNA replication at the right-end hairpin in HEK293 cells. We also localized the minimal replication origin to a 46-nt sequence in the right-end hairpin, which contains both NS1 nicking and binding sites. The identification of these essential elements of HBoV1 DNA replication acting both in cis and trans provides opportunities for developing antiviral strategies targeting HBoV1 DNA replication, and to design next generation recombinant HBoV1 vectors, a promising tool for gene therapy of lung diseases. In the third study, we provided evidence that HBoV1 could replicate independent of hairpin sequence, which is quite different from other parvoviruses. Although the mechanisms are not fully understood, this study opened new directions for future studies of parvoviruses.