Diversity of parvoviruses in bats from China and their evolutionary implications

Abstract

Parvoviridae is an important family of viruses associated with a spectrum of diseases in different mammals. Five of eight genera of its subfamily, Parvovirinae, consist of parvoviruses with clinical significance to humans. The origins and emergence of these parvoviruses are not clearly understood. Bats, on the other hand, have increasingly been recognized as important zoonotic virus reservoirs, however, not many parvoviruses are known from bats. To understand the role of bats in parvovirus evolution and transmission, samples of bats from Hong Kong and six Chinese provinces were first tested for the presence of parvoviruses using PCR. In total, 216 partial helicase-coding DNA fragments of parvoviruses were detected from bats of five different families. These fragments, as well as two additional parvoviruses detected during genome sequencing consisted of 28 potentially novel, and two known bat parvovirus species belonging to four parvovirus genera: Amdoparvovirus, Bocaparvovirus, Copiparvovirus and Dependoparvovirus.

One of the 28 potentially novel parvoviruses, Rhinolophus sinicus bat bocavirus (Rs-BtBoV), detected in bats from three different geographical regions, was further characterized. PCR specifically targeting Rs-BtBoVs detected related strains from 66 bats of six species. Rhinolophus sinicus bats had much higher detection rates than other species, suggesting their role as reservoir hosts. Among R. sinicus bats, higher Rs-BtBoV detection rates were observed in juveniles, and adult females than in adult males (P<0.05). Among adult females, Rs-BtBoV displayed a high propensity to infect lactating females (P<0.0001), with detection rate peaking during R. sinicus bats’ lactating season, and associated with lower body weight (P<0.05). Ten nearly-complete genomes amplified from bats of three different families displayed limited genetic diversity supporting interspecies transmission of the virus. One nearly-complete circular genome of Rs-BtBoV_str15 represented the first terminal hairpin sequences determined from a bat parvovirus, which revealed conserved motifs and secondary structures similar to those of human bocavirus 1.

Nearly-complete genomes amplified from four other bat bocaparvoviruses (BtBoV; Rp-BtBoV1, Rp-BtBoV2, Rol-BtBoV1, Rs-BtBoV2), and two bat adeno- associated viruses (BtAAV; Rs-BtAAV1 and Rp-BtAAV1) confirmed that they represent novel bat parvoviruses. The nearly-complete genomes of Rp/Rs-BtBoVs and Rp/Rs-BtAAVs represent the first species of parvoviruses from the horseshoe bats (Rhinolophidae), while Rol-BtBoV1 genome represents first Bocaparvovirus genome from fruit bats (Pteropodidae). Rs-BtBoV2, detected from four different bat species, displayed remarkably high genetic identities to Ungulate bocaparvovirus 5, suggesting recent interspecies transmission of the virus across hosts of different mammalian orders.

To understand evolutionary relationships among parvoviruses, phylogenetic analyses were performed on previously reported and novel bat parvoviruses, which showed parvoviruses of bat origin to be dispersed throughout the subfamily, Parvovirinae. All species of Bocaparvovirus were found to share ancestors with the BtBoVs, suggesting bats to be the major gene source for this genus. One known and two novel BtAAV genomes formed a monophyletic lineage most closely related to AAVs of humans. The rep ORFs of Rp/Rs-BtAAV1 shared highest amino acid identities with AAVs of humans. Overall, results from this study suggested that parvoviruses in bats are genetically diverse, and may evolve to occasionally spillover to other mammalian species, including humans.